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Oscilloscopes Blog

25 Posts authored by: KeysightOscilloscopes Employee

Battlefield scenarios can set up competing forces for radar/EW designers as well. Many seconds or minutes may go by as a scenario plays out with a clear winner and *****. But emulating this scenario with multi-emitter signal sources and multi-channel receivers is nontrivial. Designers need wide analysis bandwidth in measurements on hardware; they also need to evaluate a significant time period of system activity. Given this conflict, this class of pulsed RF, microwave, and mmWave applications presents a challenge.

On the signal source side, the technique of using pulse descriptor words (PDWs) is changing the game with regard to throughput and real-time signal creation. On the receiver side, if direct digitization techniques are used for amplitude and phase flatness advantages, as is the case when using some high-bandwidth oscilloscopes, the related high-speed sampling approach will burn through acquisition memory very quickly. But “segmented memory” can save the day: Signals of interest are placed into memory segments, and the receiver ignores the time when signals of interest are not present, as shown in Figure 1.

segmented memory illustration - keysight oscilloscopes

Figure 1. The segmented memory approach, where signals of interest are stored into memory segments.

This blog post explores how segmented memory in wideband oscilloscopes can be used through pulse analysis software. We’ll address the application area of Radar/EW in terms of pulse amplitude, frequency, and phase measurements, and how you can optimize accuracy.

Oscilloscope segmented memory helps you achieve long target-time capture in pulsed RF applications

In most basic pulsed RF measurements with an oscilloscope, you take measurements on a single RF pulse from a pulse train or on a limited number of pulses. And that makes sense—a fast sample rate (adequate to capture carrier plus modulation without aliasing) uses up the scope memory depth quickly. Consider an example where a pulsed RF signal has a 15-GHz carrier frequency and 2-GHz-wide modulation.

The oscilloscope must sample fast enough to handle the modulated 15-GHz RF pulse signal.  That requires a sample rate of at least ~ 2.5 x 16 GHz, or 40 GSa/sec. To have some margin beyond the 2-GHz modulation on the carrier, and to avoid the roll-off of the scope bandwidth, the next highest sample rate selectable is the full 80 GSa/sec of the oscilloscope for 33-GHz bandwidth capture.

Using a standard capture approach, where all samples simply go into the available memory regardless of what signals are present, and using the full 2-Gpts memory depth available, that corresponds to 25 msec of capture time:

(2 GSa) / (80 GSa/sec) = 25 msec

But let’s consider a different example, where a pulse train has a pulse repetition interval of 100 μusec (a pulse repetition rate [PRI] of 10 kHz) and 1-usec wide pulses. The related scope capture includes close to 250 pulses based on the following calculation:

(25 msec) / (100 μsec / pulse) = 250 pulses

By using oscilloscope segmented memory, you can dramatically increase the number of pulses captured.  With segmented memory mode, the 2 Gpts of memory depth can be broken into smaller segments. Each segment gets filled with captured trace after a trigger condition is met. In this case, the trigger event is still the beginning of the RF pulse, and segments can be defined to be a little longer than the longest pulse captured.  For example, you can use a 1.2-μsec-wide segment size can to capture the 1-usec-wide pulses, for example.

The segmented memory capture can be set up to achieve 1.2-μsec wide segments where the memory depth is chosen to be 96 kpoints and 32,768 segments, as shown in Figure 2.

Segmented memory setup on a Keysight oscilloscope

Figure 2. Segmented memory setup using 1.2-usec wide segments for 1-usec-wide pulse capture

The calculation for the required segment memory depth is simple. If you know that the sample rate is 80 GSa/sec and you want a 1.2-μsec segment length, then:

(80 GSa/sec) x (1.2 μsec) = 96,000 samples

With this choice, up to 32k segments can be selected.  Press the “Single” capture button, and 32k pulses are captured and brought into 32k segments. That corresponds to 3.3 seconds of target activity time. Is this gapless capture? No, but it is capture that focused on capturing RF pulses and ignored the time when no signal is present. Contrast this with Real Time Sampling Mode, which had 25 msec of gapless capture of 250 RF pulses.

The segmented capture can be seen in Figure 3, taken on a pulsed RF signal with a 15-GHz carrier and 2-GHz-wide linear FM chirp modulation. You can even use the “Play” button to play back the 32k segments. Statistics are calculated on the 32k pulses that were captured.

Keysight oscilloscope segmented memory capture
Figure 3. 33-GHz oscilloscope segmented memory capture of 32k pulses into 32k segments, 1.2 usec per segment

You can make similar measurements on lower frequency signals using a mid-range 8-GHz bandwidth oscilloscope. With 20-GSa/sec sampling rate on two inputs channels and 800 Msamples of memory depth, a “Single” capture can be spread across multiple memory segments.  These oscilloscopes offer 10 GSa/sec sampling across four channels as well.

There are also oscilloscopes with 63 GHz of bandwidth on two channels, with 160 GSa/sec sampling rate and a 2 Gpts memory depth.  They offer 80 GSa/sec sampling rate capture on four channels with a 2-Gpts memory depth.

Enhance measurements with oscilloscope segmented memory combined with pulse analysis software

You can control segmented memory with vector signal analysis (VSA) software. VSA lets you conduct statistical pulse analysis on many RF pulses captured into segmented memory. For example, you can perform analysis on digitally down-converted oscilloscope samples, where the format is now baseband I/Q, the measurement has been tuned to the center frequency, and a frequency analysis span is chosen to be just a little wider than the signal spectral width. This allows processing gain to reduce noise in the measurement.

After noise reduction, many measurements can be taken on the I/Q data, including how the amplitude, frequency, and phase change across an RF pulse. Figure 4 shows an example of these measurements, where memory segments 3, 4, and 5 and the pulses contained in those segments are being analyzed.

In this example, the linear FM chirp-frequency shift across the RF pulse is measured and compared to a best-fit linear ramp. (Check the right pane center).  The difference between the measured pulse and the best-fit straight line ramp is calculated and displayed (horizontal trace with noise).  You can see that the measured ramp and reference ramp have very little difference between them. The error trace is displayed with a 1 MHz/div scale and around 500-kHz peak deviation; the Freq Error RMS in the right bottom right shows around 300 kHz of frequency error.

In a similar way, the phase shift across a pulse is compared to a best-fit parabolic phase shift (see right top pane), characteristic of linear FM chirp modulation on radar pulses. You can zoom in on the difference between the measured and reference to see how much a target system is deviating from the ideal. Here we see around +8 and -5 degrees peak deviation and a Phase Error RMS of 2 degrees, as shown in the bottom right table of Figure 4.

Keysight pulse analysis software calculations
Figure 4. Pulse analysis software calculations based on measurements taken on oscilloscope segmented memory

The left center pane shows the spectral content of the RF pulse, the left upper pane displays a view of RF pulse envelope amplitude, and the left lower pane shows the difference between the measured amplitude envelope and a best-fit straight-line reference signal.

Finally, you can perform statistical analysis on the measured parameters on the number of pulses captured into segments. In Figure 5, the statistical analysis can be seen in the pulse table based on capture of 1000 memory segments.

Statistical analysis on 1000 oscilloscope memory segments
Figure 5. Statistical analysis on 1000 memory segments

 

Summary

When directly capturing wideband pulsed RF signals, the fast sampling rate required can make the capture of many pulses a challenge. The available acquisition memory gets eaten up quickly. Segmented memory is one way to address this problem by acquiring RF pulses into memory segments, and then turning off the acquisition during “quiet” time until the next RF pulse occurs.

Pulse-analysis software can both control a segmented memory capture and digitally down-convert captured signals into baseband I/Q data. This effectively tunes the measurement to a specific carrier frequency with a frequency measurement span slightly wider than the signal under test—reducing noise and increasing measurement accuracy. The time required for system validation decreases thanks to the capability to compare actual, measured pulse characteristics against ideal, relative, best-fit reference signals for amplitude, frequency, and phase. With that, you can identify issues in signal creation or system performance, and overcome the challenges that battlefield scenarios present.

A change is coming in the tools for measurements in both pulsed RF aerospace/defense and I/Q vector-modulated communications application. Whether for multi-channel analysis or for wider analysis bandwidth, high-bandwidth oscilloscopes are taking the place of traditional spectrum and signal analyzers. That’s because they can handle signals with spectral content beyond 1 or 2 GHz. These signals are being created to support the higher resolution requirements in radar systems and move the vast amounts of information in new communications systems.

 

So how do you create a powerful, wideband RF measurement suite? By coupling a high-bandwidth real-time oscilloscope with RF analysis software. Once you’ve married the two, you achieve a number of enhancements:

 

  • Noise reduction through digital down-conversion
  • A wide range of vertical scaling options, including linear and log magnitude
  • Key RF measurements including occupied bandwidth (OBW) and power spectral density (PSD)
  • Vector demodulation options for communications formats like QAM16
  • Analog demodulation options including AM, FM and PM
  • Set-up of segmented memory capture
  • Statistical pulse analysis

 

Pulse amplitude, frequency, phase, and FFT measurements

 

For radar and electronic warfare applications, it’s helpful to perform a variety of measurements on many pulses. This includes things like amplitude variation, frequency, and phase shift across pulses, and a view of the spectrum of signals. For applications such as aircraft warning receivers, you also want the capability to measure time difference and phase difference between pulses associated with the capture of a wave front by multiple antennas on an aircraft. Let’s consider some of these measurements.

 

In the simplest case, you can measure the basic pulse amplitude, frequency shift, and phase shift across the measured RF pulse. The RF pulse train is sampled by the oscilloscope and then digitally down-converted to reduce noise and allow further signal processing.

 

For example, in Figure 1, a 15-GHz carrier, 2-GHz-wide linear FM chirped RF pulse signal is shown after vector signal analysis (VSA) processing. Here’s what the image shows:

 

  • 2 GHz-wide spectral content of the signal (upper left);
  • Real part of the down-converted I/Q data (lower left);
  • 2-GHz-wide linear FM frequency chirp seen across the RF pulse (upper right);
  • parabolic phase shift seen across the RF pulse (lower right).

 

These measurements are taken in the “Vector” measurement mode.

 

Basic vector mode analysis of FFT

Basic vector mode analysis of FFT, real part of I/Q, FM chirp, and phase shift across pulse seen

 

 

Single channel, segmented memory capture, statistical RF pulse analysis

 

The next level of analysis requires a shift into “Pulse Analysis” mode. Here we use multiple oscilloscope channels to capture RF pulse signals into segments of oscilloscope memory. These are digitally down-converted into baseband I/Q signals, and then evaluated for single and multiple channel pulse analysis. For single-channel measurement, you can make three comparisons:

 

  • the linear FM frequency chirp to an ideal, best-fit linear FM chirp signal;
  • the phase shift across a pulse to a best-fit parabolic phase shift profile;
  • the amplitude of the pulse envelope to a best fit ideal straight-line best fit reference.

 

In Figure 2, you’ll see these comparisons being made between measured to reference, and then the “error” between the measured and reference is expanded in vertical scale for a close view.

 

A pulse table also displays RF pulse parameters, including an RMS error calculation between the measured frequency or phase across the pulse, compared to a best-fit reference signal. It’s also possible to show statistics for the measurements over all the pulses.

 

Keysight single-ch spectrum amplitude phase and frequency measurements

Single-channel spectrum, amplitude, phase, and frequency measurements vs. best-fit reference signals

 

Dual-channel delta pulse amplitude, frequency, and time-delay measurements

You can also make “two-channel delta” measurements, as shown in Figure 3. These measurements are becoming increasingly important in applications such as aircraft warning receiver testing, where multiple signals are being captured from multiple antennas. The time delay and frequency difference of arrival between wave fronts must be measured for angle-of-arrival calculations.

 

Notice in this example a 1 nsec time delay being measured between two RF pulses. You’ll also see a 0.2-dB difference in amplitude and a 16-kHz difference in frequency, on average.

 

Pulse analysis is also performed on three of ten captured pulses that are being placed into oscilloscope memory segments. The parabolic phase shift across pulses (lower left), the linear FM chirp frequency shift across pulses (middle right), and the pulse envelope of pulses (upper left) are superimposed for signals coming into two oscilloscope channels. As in the previous example, each scope-channel measured signal can have the measured, reference, and error signal calculations made. Finally, the FFT spectral content for both scope-channel captures of the two pulse trains (center left) is also shown.

 

Keysight 2 channel measurements of RF pulse characteristics

Two-channel measurements of RF pulse characteristics including time, amplitude, and frequency difference between two channels

 

Cross-correlation between pulses for precise time-delay measurements between RF pulses

 

In the aircraft warning receiver example mentioned previously, you can determine very precise measurements of time delay between RF pulses captured on different antennas on an aircraft by using a cross-correlation measurement between pulses. In Figure 4, a 50-psec time difference of arrival (TDOA) is being measured between two RF pulses captured on two scope input channels. Here pulses have a 10-GHz carrier, 100-MHz-wide linear FM chirp modulation, and a 1-usec width. In this measurement, you can first remove the channel-to-channel skew between oscilloscope channels, including cable delays at the temperature measurements will be taken, through de-embedding. Then a measurement can be made to see the actual time shift between the captured signals. Measurements show a mean delay of 50 psec, with a peak-to-peak variation in delay between 47 psec and 53 psec.

 

Two-channel cross-correlation measurement for precise time delay between pulses

Two-channel cross-correlation measurement for precise time delay between pulses

 

Math function used to measure phase shift between two RF pulses

 

The difference in phase between two RF pulses is also critical in a variety of radar/EW/warning receiver-oriented applications. Through the use of math functions, the measured phase across one pulse can be subtracted from the measured phase across a second pulse, measured on two oscilloscope input channels. We can measure the same two linear FM chirp signals from the last example to view the phase shift between the two pulse trains by comparing related pulses. Again this might be seen from two antennas on an aircraft. The time shift has now been set to zero on an arbitrary waveform generator, but a 25-degree phase shift is being introduced between the two signals. A capture shown in Figure 5, top center trace C, and related blue marker 1, show this 25-degree phase shift in a mean measurement in lower right Trace D, as well as only a 0.8-degree standard deviation and a 0.7 variance.  These are average values over the width of the pulses.

 

Two-channel phase difference measurement between two RF pulses

Two-channel phase difference measurement between two RF pulses

 

Summary

More radar/EW/warning receiver applications are driving toward wider modulation bandwidths to increase range and angle-of-arrival precision capability in related systems. At times, this extends beyond 1-GHz modulation bandwidths. Designers increasingly use wideband oscilloscopes as RF receivers to evaluate related wideband signals when validating their hardware prototypes. Although scope measurements directly are of interest, it’s often advantageous to use analysis software to digitally down-convert captured wideband signals to reduce noise and allow more in-depth analysis of baseband I/Q signals. By combining a wideband scope and VSA software with appropriate techniques, you can readily make angle-of-arrival calculations for a variety of systems.

By: Drew Hanken

Have you ever wondered, “What is this ringing I am seeing in my signal? Why is there preshoot and overshoot on a simple square wave? How is a preshoot possible when it appears to be precausal to downstream information?”

I have been an R&D engineer here at Keysight/Agilent Technologies for the last five years. Fourier series is a topic that was covered in a recent graduate class as a method for solving partial differential equations. I’ll explain the occurrence of this ringing from the perspective of the underlying theory, and then relate it back to using an oscilloscope.

Download the "6 Essentials for Getting the Most Out of Your Oscilloscope" eBook.

 

In short, this ringing is a phenomenon that presents itself because of the method an oscilloscope uses to construct a signal – by summing the frequency components of the signal. This method of building a signal is known as Fourier series. It is the most useful way for an oscilloscope to process and measure a signal because it deconstructs the signal into its frequency components for analysis. The inherent discontinuity of a square wave presents some problems with this reconstruction method that can be understood by exploring the mathematical theory. Understanding this can help you to select the right oscilloscope for your measurement needs. It’s also worth noting that this method is used by all oscilloscopes, it’s not just a Keysight method.

Keysight Fourier Series on a Keysight Infiniium oscilloscope

First off, you need to understand that any arbitrary function f(x) can be constructed by the sum of simple sine or cosine functions that vary in amplitude and frequency. More specifically, any function of x, f(x), can be built using an infinite series of sine waves with coefficients An and increasing frequencies (n*pi).

any arbitrary function f(x) can be constructed by the sum of simple sine or cosine functions that vary in amplitude and frequency

any arbitrary function f(x) can be constructed by the sum of simple cosine functions that vary in amplitude and frequency

Sine and cosine functions can both be used for Fourier series because they both have the property of orthogonality. There are a few other functions that satisfy the orthogonality requirement including Bessel functions and Legendre polynomials. While these functions are useful for problems in cylindrical or polar coordinates, they do not apply to this discussion. The definition of orthogonality for a function φ is that it must satisfy the following condition:

Sine and cosine functions can both be used for Fourier series because they both have the property of orthogonality

Using the above definition, it is possible to solve for the coefficients (An) for any function, and build the function, using orthogonal functions.

Build a function using orthogonal functions

You can see that any function can be constructed using an infinite series of terms, and approximated by a finite number of sine waves. Every function has a unique set of coefficients, An, that are substituted into the sum. The values of these coefficients determine the function that will be reconstructed.  It is easy to picture changing the amplitude of a sine wave by multiplying it by a coefficient. This would be a Fourier series with only one term, and would return the desired function with the magnitude changed. Let’s look at constructing a linear line using sine and cosine functions. This is tougher to picture because a line is not oscillatory, but the addition of multiple sine or cosine terms will begin to take the shape of a line.

Constructing a linear line using sine functions to create a Fourier Series

Constructing a linear line using cosine functions to create a Fourier Series

You can see that the more terms that are summed, the closer the approximation becomes to the actual function. Theoretically, if an infinite number or terms are used, the Fourier series will cease to be an approximation and take the exact shape of the function.

Now, let’s take a look at a square wave and how it appears when constructed using Fourier series the same way an oscilloscope would. We will first write a step function of length (L) that, when repeated periodically, will be our representation of a square wave.

A step function of length (L), when repeated periodically, represents a square wave on an oscilloscope.

As stated earlier, this function can be rewritten as an infinite series of an orthogonal function φ:

Square wave function, written as an infinite series of an orthogonal function φ

With choosing a sine wave as the orthogonal function in the above expression, all that is left is to solve for the coefficients to construct a square wave and plot the results.

use a sine wave as the orthogonal function

One important takeaway from this formula is that the series composition of a square wave only uses the odd harmonics. This stems from the fact that a square wave is an odd function, which has important implications on measuring signals of this sort. Given a 1 Gb/s square wave, the bandwidth of the measurement device must now exceed 3 Gb/s to capture more information than the primary frequency. Each incremental harmonic that is captured will start to look more like a square wave with faster rising and falling edges as seen below.

Each incremental harmonic that is captured will start to look more like a square wave with faster rising and falling edges

The rise time of the plotted signals gets smaller as the number of terms increases. The highest term in the Fourier series will correspond to the highest frequency that is used to construct the signal. Thus, the rise time is dictated by this last term, which in turn dictates highest frequency. An ideal square wave will have a zero rise time – but that would take infinite bandwidth to reproduce with this method. This square wave’s discontinuity is the heart of the problem, and is the reason for the preshoot and overshoot seen above. Taking a closer look at these areas of the wave, you can see that the ringing in the signal does not change in magnitude with the number of terms and remains at roughly 18% of the amplitude. It will, however get thinner as more terms are used and be a smaller source of error. This ringing caused by a discontinuity is referred to as Gibbs Phenomenon, and is unavoidable when the signal is properly constructed using Fourier series. That is not to say that other sources of ringing are not present, but it is important to be aware of this behavior at discontinuities.

his ringing caused by a discontinuity is referred to as Gibbs Phenomenon

FourierSeries_13_Keysight

Given this information, you can see why it is important to select the right oscilloscope based on your measurement needs. If you need to capture the slew rate of your transceiver, or to open the area of your eye diagram, you may need a higher bandwidth oscilloscope to capture the frequency content of the higher order harmonics and to reduce the effects of ringing on your capture.

Learn more about oscilloscopes available from Keysight.

 

Wideband RF measurements are changing and along with them, the tools you need to make sense of the signals. Today’s radar systems require higher target tracking resolution, communications systems require higher data throughput—and to meet the demands, you require wider modulation schemes on related signals to validate prototypes and production units.

 

Gone are the days when an instantaneous measurement bandwidth of 510 MHz, the longtime standard in signal and spectrum analyzers, could handle this modulation bandwidth. Some systems have crossed beyond 1- GHz and even 2-GHz-wide formats. You need a different approach to make high-quality, insight-providing wideband RF measurements.

 

How different an approach? One that uses high-bandwidth, real-time oscilloscopes. Digitizers and oscilloscopes offer enough bandwidth and sample rate to directly sample the carrier plus modulation either alone or with the use of down-converters in front of the scopes.

 

The trick is knowing what to use when. One way to consider your options for wideband measurements is to plot the possibilities on a chart. The vertical axis represents analysis bandwidth of the solution and the horizontal axis representing carrier frequency that you can measure. Don’t worry about doing the plot—we’ve taken care of it:

Applicable tools as a function of signal carrier frequency and spectral width

 

As you see, classic signal analyzers offer analysis bandwidths up to 1 GHz and handle carrier frequencies up to around 50 GHz. As an alternative, mid-range oscilloscopes offer bandwidths in the 8-GHz range, letting you measure signals with carrier frequencies approaching 8 GHz, and with very wide modulation bandwidths, approaching 8 GHz. As long as the carrier plus modulation spectrum fits within the oscilloscope bandwidth, you can make meaningful measurements.

 

But even that may not be enough. In wideband aerospace/defense applications, including electronic warfare, radar, and surveillance, signals of interest may have carrier frequencies higher than 8 GHz. Cue the high-performance oscilloscopes. These scope families have higher bandwidths up to 33 GHz and 63 GHz and, as you might guess, corresponding higher prices. But they offer impressive performance in areas like frequency response flatness and low noise. An alternative is to place a down converter in front of a mid-range oscilloscope. You pay less but can handle high carrier-frequency signals with wideband modulation—provided you’re willing to make some tradeoffs in amplitude and phase linearity.

 

As a first down-converter option, you can place a standard signal analyzer in front of a mid-range oscilloscope and use the IF down-conversion path in the signal analyzer. You’ll typically need calibration to flatten the overall system amplitude and phase response over frequency. But a solution like this can address a wide range of carrier frequencies, typically up to 50 GHz.

 

A second down-converter option is to place a lower cost harmonic mixer in front of a mid-range scope. This results in a “banded” solution: Very high carrier frequencies can be analyzed, but there is generally a “band” of carrier frequencies that a particular harmonic mixer can handle. That makes this option especially convenient for applications like 5G, Wigig, and automotive radar.

 

Typical RF performance for high-bandwidth real-time oscilloscopes

So what do you need to know before making FFT or wideband RF measurements with an oscilloscope or scope combined with vector signal analyzer (VSA) software? You need to know that the RF characteristics can have a major influence on the measurement results—so you’ll need to evaluate this first.

 

Today you can find oscilloscopes that incorporate amplitude and phase correction for excellent absolute amplitude accuracy and low deviation from linear phase across their frequency range. This in turn contributes to high-quality RF measurements. These oscilloscopes also offer excellent noise densities, in the vicinity of -160 dBm per hertz, and high dynamic range and signal-to-noise ratios, considering the wide bandwidth capability they offer.

 

What does that do for you? You can look at wideband signals with very small amplitude adjacent in time to large signals. You can also boost scope sensitivity to measure isolated, small-amplitude signals. The time-base circuitry in these oscilloscopes also means good, close-in phase noise, which corresponds to low jitter in very deep memory traces. If you want more details, see the RF characteristics of a high-performance 33-GHz oscilloscope in Table 1.

Table 1. Typical RF performance in a high-bandwidth oscilloscope

 

Wideband pulsed RF time-domain measurements of envelope, frequency, and phase chirp

Now that we know what our high-bandwidth scope is capable of, let’s see how it handles time-domain measurement and analysis of wideband pulsed-RF signals with no help. The choice of which oscilloscope to use depends on the maximum frequency content of the carrier plus modulation. Consider an example where a signal under test is supposed to have 1-usec-wide pulses, with a pulse repetition interval of 100 usec. It also has an RF carrier frequency of 15 GHz and linear FM chirping that is 2-GHz wide.

 

Figure 2 shows a variety of measurements on a single RF pulse, including envelope parameters and the frequency chirp across the pulse. Stable triggering on this pulse is accomplished with trigger “holdoff” set to a value slightly longer than the 1-usec RF pulse width.

Figure 2. Time-domain measurements on 1-usec wide, 15-GHz carrier, 2-GHz-wide linear FM chirped RF pulse with a 33-GHz bandwidth oscilloscope

 

To make amplitude measurements, we use the “Envelope” math function and then pulse measurements are dropped down onto the visible RF pulse envelope. A “Frequency” measurement is dropped down onto the RF pulse (not onto the envelope), and a “Measurement Trend” math function is defined with the frequency measurement as a source. Next we perform a smoothing math function on the measurement trend with the resultant linear ramp display of the linear FM chirp modulation, also shown in Figure 2. The oscilloscope magnitude linearity over the frequency span of interest has a direct effect upon the quality of the envelope measurement. To see the effect, take a look at the magnitude plot over frequency of the 33-GHz bandwidth scope in Figure 3.

Figure 3. Typical magnitude linearity over frequency on four individual 33-GHz channels

 

Wideband pulsed RF-gated FFT measurement of spectrum

You can create a wideband FFT by defining an “FFT Magnitude” math function with “Rectangular” windowing. Then create a time-gated FFT using the (you guessed it) “Timing Gate” math function. Once the time-gating math function is defined, you can define an FFT math function that is calculated from the time record within the time gate, as shown in Figure 4.

Figure 4. View of normal and time-gated FFT and display with time gate at the beginning of the RF pulse

 

Wideband pulsed-RF time- and frequency-domain measurements with a scope plus VSA software

But that’s not all. You can further enhance RF and FFT measurements made with high-bandwidth oscilloscopes by importing scope-captured signals into VSA software. Some advantages of using VSA software include:

  • many built-in RF measurements;
  • ability to bandpass-filter oscilloscope input samples and decimate prior to the FFT calculation to reduce noise and speed the calculation;
  • variety of digital and analog demodulation options like QAM16 and FM demodulation;
  • time-domain baseband view of pulse with reduced noise through processing gain;
  • frequency and phase shift across the pulse through a demodulator.

 

If the oscilloscope-captured data is imported to VSA software, it can be digitally down-converted into I and Q baseband data, bandpass-filtered, and then resampled. This can greatly decrease the amount of noise in the measurement. Essentially the process is “tuning” to the center frequency of the signal and “zooming” into the signal to analyze the modulation. This is also referred to as “processing gain.”

 

In this example, the original 8-GHz-wide measurement with the associated noise is reduced to a 500-MHz-wide measurement, centered on the 3.7-GHz carrier with an instantaneous measurement bandwidth slightly wider than the width of the signal modulation. This corresponds to an improvement in signal-to-noise (SNR) ratio of:

 

10log*(ScopeBW/Span) = 10log*(8E+09/500E+6) = 12 dB.

 

SNR is improved by 10log*(ScopeBW/Span).

 

By taking advantage of this processing gain, combined with the VSA software’s capability to use a log-magnitude scale, and using averaging, you can now see the 50-dB down pulse, as shown in Figure 5. It wasn’t visible in the scope display with the 8-GHz wide measurement.

Figure 5. 50 dB down pulse seen with VSA software “Center Frequency” and “Span” set

 

The secret to long target-time capture and statistical pulse analysis

When an oscilloscope samples a wideband RF signal, it must do so at a fast enough rate to accurately capture the carrier plus modulation. Often a very fast sample rate is required. In a normal real-time sampling mode, the oscilloscope memory will not allow for a long capture period.

 

But there is a work-around: oscilloscope segmented memory. This can greatly increase the target activity time when there is a low-duty-cycle signal, such as a common pulsed RF radar signal. The scope memory is divided into smaller segments of fixed time width, chosen to be a little wider than the widest RF pulse. The scope triggers on an event, such as the beginning of the RF pulse, and then places one RF pulse in a memory segment. The scope then stops capturing data, rearms the trigger, and waits for the next RF pulse. A second RF pulse is put into the second segment of memory. This process continues until all the scope memory segments are used.

 

Modern pulse-analysis software can let you take advantage of the scope segmented memory and then offers built-in measurements for pulsed RF signals. Figure 6 shows a capture of many RF pulses via segmented memory, combined with pulse-parameter measurements in the pulse-analysis software. Here a 1-GHz linear FM chirp and related phase shift across pulses is compared to a best-fit ideal linear ramp and ideal parabola, respectively. A close-up view is made of the delta between measured and reference for frequency in trace S and for phase in trace J.

Figure 6. Pulse analysis software calculations based on measurements taken on oscilloscope segmented memory

 

Conclusion

The bandwidth limitations of signal and spectrum analyzers are driving designers to use digitizers and oscilloscopes, with or without down-converters. Math functions like envelope, measurement trend, and FFT all prove helpful in understanding target system operation and issues. Combining an oscilloscope with VSA software creates a powerful RF-measurement suite to perform measurements, including demodulation, extended SNR time-domain views, and statistical RF pulse analysis. Yes, there’s a tradeoff between dynamic range/SNR and the instantaneous bandwidth available, but you can still access many useful wideband measurements to evaluate a prototype or production unit.

By: Ryan Carlino

 

As you become an oscilloscope power user, you may find that there are times when the usual four oscilloscope channels are just not enough. You might want to make sure your system comes out of reset properly by observing the timing relationship of various reset and status lines. You also might need to verify that power supply rails come up and go down in the proper order. Modern FPGAs often have more than four power supplies and those supplies are required to sequence in a specified fashion (i.e. certain supplies need to come up before other ones and in a specified amount of time). Here’s an example of Altera’s specification of how fifteen power supplies for a Stratix FPGA should come up.

From page 322 of: Stratix V Device Handbook

 

Designing power sequencing circuits and verifying their actual behavior is something I do on most boards I work on. Here’s a trick for capturing more than four power supplies in a single scope image.

 

A board I am working on right now provides eight power supplies to some custom bipolar ASICs (Keysight-designed chips that have both positive and negative power supplies). Like an FPGA, the ASICs have specific power sequencing requirements. In my case, four positive supplies should come up and “peel off,” followed by four negative supplies which also “peel off.” The ASIC designers and I came to this agreement and I documented it on a post-it note, which became my design spec (Figure 1).

 

 

Now that boards are built, I want to verify that my design worked this way. Ideally, I would capture an oscilloscope plot that looked just like my drawing, but my scope only has four channels! I don’t want two plots and I don’t have time to save the waveform data and load them into a plotting program.

 

This is where saving waveforms into memory really shines: you can display up to eight waveforms at once. Here’s how I get the plot I want using my Keysight S-Series oscilloscope.

  1. Pick a master signal to trigger on – It’s going to take three triggers to get all eight waveforms, so pick one signal to be the “master”. I like to use the first signal that turns on. Set the trigger level in the middle of that signal and keep it there.
  2. Make sure the timing is consistent – Stacking waveforms is only useful if the signals aren’t moving in time with respect to each other. I like to take a few test triggers to see if the waveforms come up consistently. If some of the signals shift in time, try to figure out how far they go. Will a composite waveform make sense if the timing changes?
  3. Check the vertical and horizontal scales – You want to capture the signals so they fit on the screen. Pick an appropriate vertical scale and offset for each signal. Check that the horizontal scale is big enough to capture the last signal when triggering on the first.
  4. Trigger and save, then repeat as needed – Get probes on your signals and start capturing. First probe your master signal (#1) and three other signals (#2, #3, #4). Save signals #2-#4 into three waveform memories. Then, move the probe from #2 to signal #5. Trigger and save signal #5 into the last memory. Then move the probes to the final signals #6-#8 and trigger and save. Now you can view all eight of your signals!

 

Let’s run through an example of my eight power supplies turning on. I use two grids (positive rails on top, negative rails on bottom) with all waveforms at the same vertical scale. I use +12V as my trigger, since it comes up first. I checked that the turn-on timing is consistent during power-up and set my horizontal and vertical scales.

 

On my first trigger, I capture three of the negative supplies and save them into memories.

 

Just right-click each waveform to save and select Save Channel -> To Memory.

 

 

With three memories done, I move the CH2 probe and trigger a second time to capture the last negative supply into a memory.

 

 

On my final trigger, I move the probes to the positive supplies and save 8-waveform plot.

 

 

I like to label the waveforms with descriptive names using bookmarks.

 

 

So, there are my 8 power supplies turning on – all on one plot. I can see where things are not ideal and can react to them if needed. Now, I can repeat the process to get a turn-off plot.

Author: Chris Felder

As one of the Keysight R&D engineers who developed Project Echo, the touch screen and interface for Keysight InfiniiVision oscilloscopes introduced on the 4000 X-Series in 2012, I know these oscilloscopes from the inside out; literally. Here are a few creative shortcuts we have built into the oscilloscope interface to help you get more out of the scope.

As Keysight was designing the first touch interface, which is used on the Keysight 3000T, 4000-X, and 6000-X Series scopes today, we conducted extensive usability testing to ensure the touch screen and interface design enhanced the existing interface and the scope could be entirely driven using the touch screen. While touch can provide many benefits, we also wanted to be sure that it did not impair the usability for those not using the touch feature. Even if you prefer to drive the scope using the front panel keys and knobs, using touch in minor ways may greatly accelerate your tasks.

Let’s start with the “main menu” button in the upper left corner.

All of the oscilloscope’s menus and dialogs are accessible through this menu.  There are some handy shortcuts along the left side, and you can manipulate several feature states directly through this menu (channels, cursors, measurements, etc.).  The Applications menu gives a list of your licensed and installed oscilloscope applications, but also lists unlicensed applications – handy if you’d like to explore and read about all the capabilities built into your scope.

 

From the main menu, we move on to the status area along the top of the graticule; this area hold lots of readouts that show the state of the oscilloscope, and all of them are touchable.  Touch the scale or delay values in the Horizontal grouping, for instance, and you’ll get this handy popup:

 

From here, you can step the values using buttons, or touch the values once more to get a numerical keypad for direct entry.  If you want to change other timebase settings, you can press the gray ‘H’ button in the status area for a quick shortcut to the Horizontal softkey menu.

In some areas, we’ve added more significant shortcuts for the most common tasks.  Touch the trigger status indicator, for example, and you immediately toggle from Auto mode to Normal mode, and vice-versa:

 

The sidebar along the right side of the screen is another area we’ve really optimized for touch.  Any dialog box with a series of dots in the upper left (what we call a “gripper”) can be repositioned by dragging it from the title bar area; the same is true of sidebar tabs.  Any tab can be grabbed using the grippers, undocked, and positioned anywhere you like.  You can even re-dock the tab in a half-height mode, allowing you to see two tabs at once:

 

Like the status area, sidebar tabs are filled with touch shortcuts.  You can touch the analog channel input information in the Summary tab to quickly perform a slew of front end and probe configuration settings:

 


Titles in the sidebar tab look a bit like buttons for a reason – they all have handy shortcut menus when you touch them.  Touching the title in the Cursors sidebar, for example, lets you directly change mode and source settings without needing to travel to the Cursors Menu:

 

In the Measurements tab, you can touch individual installed measurements to track, clear, or reset them:

The softkey menu area along the bottom of the screen frequently includes readouts for status items related to the current menu, and…you guessed it…they’re all touchable! If you have the WaveGen (waveform generator) option enabled on your scope, the Waveform Generator Menu contains a particularly handy shortcut; if you touch the “Gen Out” area, you get a comprehensive control stack for the selected WaveGen, from which you can change a variety of settings without bouncing between multiple softkey menus:

Like all dialog boxes, this dialog can be re-positioned by dragging it within its title bar area.  You can also use the blue Menu button to configure dialog boxes to use a transparent background.  Now you can position and configure dialog boxes and sidebar tabs as you wish!

We strive to follow the rule, “everything is touchable” and we’re constantly adding new shortcuts and convenience menus with every software release. 

 

We always welcome your suggestions and feedback – comment here to let us know what we can do to make your oscilloscope experience more efficient.

By: Taku Furuta

 

Visiting engineers that use our gear is exciting and it's often an excellent learning experience. My visits with engineers cover a range of topics from answering questions on specific technical capabilities to presenting the latest technologies to researching product use models.

In these visits, I often demonstrate product features and benefits when using oscilloscopes. However, it is also common that customers show me their oscilloscope measurement tips that blow my mind.  My first blog talked about the formula to figure out system bandwidth (the bandwidth of the scope + the probe). Now let me share a neat measurement where you can quickly find the “true” bandwidth (or system bandwidth) of your oscilloscope yourself, a tip that an engineer taught me about 15 years ago.

Download the "6 Essentials for Getting the Most Out of Your Oscilloscope" eBook.

 

“Let me test it to see if your new scope REALLY has 6 GHz bandwidth” said a customer in the very first VIP visit disclosing Keysight’s (then Agilent) first 6 GHz real-time oscilloscope.  This caught me by surprise as no previous customers I had ever met had made such a statement.

“I need to connect my fastest step response generator to your scope’s front end first”.  He plugged in his faster-than-50-ps edge rate step signal generator and then differentiated the signal using the “differentiate” math function to derive the impulse response signal.  He continued and applied the “FFT” (Fast Fourier Transform) math function to the calculated impulse response signal in order to plot the frequency content from DC all the way up to 6 GHz (and beyond).  Finally, he nodded, smiled and told me, “Excellent and congratulations!  Your scope has more than 6 GHz of analog bandwidth” by pointing out the FFT plot where the FFT value finally attenuated down by -3 dB (the bandwidth point).

In theory, a perfect step response has an instantaneous (zero) rise time, and therefore you can mathematically derive the perfect impulse response by differentiating it.  And in theory, the perfect impulse response signal has an infinite amount of frequency content, so it is a perfect signal to check the “finite” bandwidth limit of an oscilloscope’s front end.  No signals are perfect, but the fast edge rate step generator can serve this purpose well.  Wow, what a quick and clever way to test the system!  Ever since this customer visit, this has become my favorite method to demonstrate an oscilloscope’s front end bandwidth performance.

Alright, enough of a nostalgic story. Here are the step by step instructions with oscilloscope screenshots for you to duplicate this “measure of your oscilloscope’s true bandwidth” procedure.  As I wrote in my first blog, most oscilloscopes come with a little “more” bandwidth than what’s specified in their datasheet, so this may be a fun exercise!  The procedure will be a little simpler if you have a Keysight InfiniiVision X-Series (3000A/TX, 4000X or 6000X) oscilloscope because you can generate a pretty fast step response using the trigger out function of the X-Series.  You can alternatively use your favorite step generator, but be sure the edge rate is fast enough to contain enough frequency to test your oscilloscope.  I recommend using an edge rate more than twice as fast as the calculated rise time specified in the scope’s datasheet.  Also, note that the accuracy of your measurement heavily depends on the cleanness/flatness (signal integrity) of the input step response.

InfiniiVision Series Oscilloscopes

Trigger out edge rate

6000 X-Series (DSO/MSO-X 6000A)

~ 700 ps

4000 X-Series (DSO/MSO-X 4000A)

~ 1.4 ns

3000 X-Series (DSO/MSO-X 3000A/T)

~ 1.7 ns

Table 1:  The summary of the trigger out signal’s edge rate

 Step 1: Connect a fast edge rate step response signal.  The below example uses the trigger out signal of the InfiniiVision 6000X (~700 ps edge rate).  Scale the signal so the edge gets placed at the center of the screen.  Make sure to vertically maximize the signal without clipping it in order to use full 8 bit resolution of your scope’s analog to digital converter (see the blog post “This Quick Trick Makes Your Oscilloscope Measurement 1,000 Times Better” for more detail).  Change the channel’s input impedance to 50 Ω to match your source.  Usually, a fast step generator has an output impedance of 50 Ω.  The output impedance of the InfiniiVision X-Series oscilloscope’s trigger out signal is also 50 Ω.

Step 2:  Apply the differentiate math function to your step response signal (channel 1 in this example).  For the Keysight InfiniiVision oscilloscopes, the differentiate math function is available on the 3000AX, 3000TX, 4000X and 6000X.

Figure 1: The step response signal (yellow) and the math function impulse response signal (purple)

Step 3: Apply the FFT math function to your impulse response signal (math function 1 in this example).  For the Keysight InfiniiVision oscilloscopes, the FFT math function is available on all models.

Figure 2: The step response signal (yellow) and the math function FFT plot (purple) of the impulse response signal

 

Step 4:  Turn on cursors to measure the frequency where the signal is attenuated by -3 dBm.  You can read the ΔY value in the cursor readout to precisely determine this point.  This is the true measured bandwidth of your oscilloscope.  In this example, it measured the “true” bandwidth of a 200 MHz InfiniiVision MSO-X 4024A to be around 250 MHz while the product’s specification says 200 MHz.  A nice bonus of an extra 50 MHz.

Figure 3: Measuring the oscilloscope’s bandwidth using the cursor

 

Now, let’s expand the same concept to measure the system bandwidth of your oscilloscope and probe. A similar connection can be used, however, it will require a probing point for the probe to pick up the signal.  What I usually use is a 50 Ω microstrip line fixture like the ones shown below.

Figure 4a: Handmade microstrip line 50 ohm fixture

Figure 4b: Keysight E2655C Probe deskew and performance verification kit

 

Insert the fixture between the cable and the scope’s BNC channel input and then probe the signal with the probe you want to measure the system bandwidth for.

Figure 5: Connecting the probe to the fixture

 

Once you have the probed signal on screen, just repeat the steps describe above.  The next section shows two screenshots from the system bandwidth measurements done on the 200 MHz scope; 200 MHz scope + 100 MHz passive probe and 200 MHz scope + 200 MHz passive probe.  You will note the “true” bandwidth is higher than the calculated bandwidth, since both oscilloscope and probe usually have a slightly more bandwidth than they specify.

Figure 6: 200 MHz oscilloscope + 100 MHz probe system bandwidth

 

For example, the measured system bandwidth in Figure 6 is around 140 MHz.  If you were to use the formula from the previous blog, the theoretical system bandwidth of a 200 MHz and a 100 MHz probe should be around 90 MHz, so you are getting ~ 50 MHz more due to “bonus” bandwidths on the scope and the probe.  In fact, because you already know the true bandwidth of this 200 MHz scope is around 250 MHz, you can easily find that this 100 MHz passive probe actually has around 170 MHz bandwidth using the same formula!  Note, I’m assuming both the scope and probe have the Gaussian response filter.

Figure 7: 200 MHz oscilloscope + 200 MHz probe system bandwidth

 

In the final example, it measured system bandwidth to be around 200 MHz, as seen in Figure 7.  Applying the same formula, you can calculate quickly that this 200 MHz probe actually has more than 300 MHz bandwidth, 100 MHz additional bandwidth beyond the specified value!!

 

 

By: Taku Furuta

 

I bought my first car navigation system, or “nav”, back in 2000. I believe I was still one of the “early adopters”; however, the car nav was already becoming a popular car electronic in Japan by then.  Actually, it was a pretty fancy one with a retractable display, 3D virtual map, built in gyro-compass (so it would still provide guidance even when satellite signals were lost), altitude meter and more.  However, what impressed me the most was the “full voice control system”.  “Take me home”, “call my mom”, “100 m scale”, “avoid traffic jam” were some of the popular commands I used back then.  Oh, yeah, and the nav even spoke different Japanese dialects depending on the location and setting I chose.

Coincidently, year 2000 is when I joined Keysight, (Agilent at the time). Joining one of the most technically savvy companies in the industry as an oscilloscope product line manager, I had a high hope of “what if oscilloscopes can hear my voice, too”.

Well, Agilent (Keysight) certainly did not disappoint me. In fact, did you know that Agilent has had a voice control enabled oscilloscope since 1999?  The product was called “Option 200: VoiceControl for Agilent Infiniium Oscilloscopes (E2635A)”.  Here is the picture from the original datasheet.

The option understood popular scope operating commands like “Run”, Stop”, “Default Setup” and “Auto Scale”. It controlled the vertical setting (like volts/div), horizontal controls (like time/div or delay sweep), and trigger and storage commands.  In another words, the most popular operations were possible via voice commands… in 1999!  In fact, many of my customers back then were asking for a scope “foot switch” for those operating it hands-free in the manufacturing line or engineers holding two probes in both their hands.  “Wow, this must be a perfect solution, just like I loved my car nav voice commands!”  At least, this was my first reaction as a first year product line manager.  Well, it did not come out to be exactly that way.

First it understood English, to be specific American English, but nothing else. Growing up in the US, I had no problem using it. Believe it or not, it didn’t understand my good-old colleague’s British English!  Obviously it did not understand Japanese and perhaps had a lot of trouble with “Asian pronounced English” as well.  There was no “Siri” back then and I guess I don’t need to talk about the sales results.  However, I thought it was a brilliant idea as the fundamental needs were there.  Second, as you can see on the image above, one must use an included special “microphone” when talking to the scope, which was just one more device to lose.

Now, let me fast forward the clock to the year 2014, 15 years after a great but crazy innovation. If my memory is correct, no other oscilloscope vendors released another voice control enabled scope since the Infiniium option 200. And so Keysight tries again, in the era where voice control is a lot more pervasive, again thanks to Siri and Google devices in the market.

So, the new InfiniiVision 6000 X-Series oscilloscopes released in April 2014 comes with the world’s only voice control system, but this time with 14 different languages and dialects, including English (American), English (British) and English (Indian)! And yes, it understands Japanese as well.  Furthermore, no dorky microphone is needed this time.  And off course, now it is powered by the Nuance Communications, Inc. voice recognition engine (the company who build the Siri voice recognition system).

 

So, the next time, you see the InfiniiVision 6000 X-Series scope, make sure to say “Hello Scope” and it will gladly listen and respond to your commands in most languages around the world.

What’s the next crazy and innovative idea? What should all scopes have as a standard feature in 2030, another 15 years from now?  As a Keysight oscilloscope planner, my job is to help realize your craziest oscilloscope dreams!  Let me know!!

By Taku Furuta

 

“I am using a 100 MHz oscilloscope with an included 100 MHz passive probe, I am supposed to be able to measure a 90 MHz sine wave, right?  Is the scope or probe broken?”

I hear this sort of question popping up from time to time, understandably since most oscilloscope datasheets do not discuss the “system bandwidth” or your effective bandwidth when a scope is used with a specific probe.

Both an oscilloscope and a probe have bandwidth specifications, the frequency value where the amplitude of input signal attenuates by 3 dB.  So, if your scope’s datasheet specifies its bandwidth at “100 MHz”, you are guaranteed to measure at least ~70% of your signal amplitude at its bandwidth frequency.  The same can be said for your probe as well.  The tricky part is, however, your oscilloscope + probe bandwidth, or your “system bandwidth”, may not be 100 MHz when you use them together. So, what is the system bandwidth in this case?

Before knowing your system bandwidth, you need to know the front end filter response of your oscilloscope.  You may or may not find this info in the datasheet, so call your scope’s support line if it is not stated.  If you don’t want to call/write the support line, I’ll provide you a quick tip to figure this out by just looking at the calculated rise time specifications in datasheets at the end of this blog.  However, it is a good rule of thumb to think the filter is a “Gaussian” type if the bandwidth of your scope is below 1 GHz.  For oscilloscopes with 1 GHz or more bandwidth, it could have a filter type called a “Brickwall”.

In the case of the Gaussian filter, which is the traditional front end filter type used for decades in both analog and digital storage oscilloscopes, the scope and probe’s system bandwidth is calculated using the below formula.

Let’s apply the above example to this formula.  Since your scope’s and probe’s bandwidth are 100 MHz each, your system bandwidth will be 70.7 MHz.  In other words, your signal’s amplitude is attenuated by 3 dB at 70.7 MHz.  Obviously, you will not see full amplitude of a 90 MHz sine wave!

In reality, most of oscilloscope manufacturers add some margin to the bandwidth specifications of both scopes and probes.  So, if you see the specification says “100 MHz”, it most likely has some additional bandwidth, like 110 or 120 MHz.

Now, say if you have a “Brickwall (or maximum flatness)” type filter response oscilloscope and probe instead.  It is extremely rare to see the Brickwall filter on a 100 MHz scope, but for this example say you did.  In such case, unfortunately, the former “square root of sum of squares” formula cannot be used.  In this case, the system bandwidth formula will be:

System Bandwidth = min {scope bandwidth, probe bandwidth}

So, if I apply the original example to this formula, your system bandwidth is now at 100 MHz, therefore, you should see nearly full amplitude of your 90 MHz sine wave.

I am not sure why this simple formula has disappeared from most oscilloscopes’ datasheets.  Perhaps there is more than sufficient bandwidth in most oscilloscopes today where engineers do not need to operate them at their upper limits.  Perhaps this is already taught in school.  Nevertheless, this is a quite useful tip to know, especially if you are seeing unexpected measurement results.

BTW, here is a quick and dirty way to determine if your scope has the “Gaussian” or “Brickwall” type response filter.  First, find your scope’s calculated rise time info.  The below is an example from Keysight InfiniiVision 4000 X-Series oscilloscope.

Now, divide “0.35” the calculated rise time value.  In the case of the 200 MHz oscilloscope (4022A), it will be

0.35 / 1.75 ns = 200 MHz

So, you verified the coefficient it was used to calculate the rise time was “0.35”.  0.35 is the coefficient value for a “Gaussian” response filter, so you know this 200 MHz oscilloscope has a Gaussian filter front end.  On the other hand, if you apply the same formula to 1 GHz oscilloscope (4104A),

0.35 / 450 ps = 778 MHz

The value was 778 MHz and not 1 GHz.  Well, you now know the coefficient used for this oscilloscope was not “0.35”, but was “0.45” (0.45 / 450 ps = 1 GHz).  When the coefficient value is larger than 0.35 such as 0.4, 0.45 or even 0.5, it indicates the scope’s front end has a filter response closer to the Brickwall filter.

Hope this small tip helps you to understand the scopes better.  See you all in the next blog!

Meet the Team!

Welcome to the new Keysight Oscilloscopes blog! We will be posting regularly on a wide variety of topics involving test and measurement: everything from industry updates to application news to oscilloscope tips and tricks.

To begin, we wanted to introduce the blogging team so you know their areas of expertise and where they will focus their posts and communications.

 

Daniel Bogdanoff, Keysight Technologies

Daniel Bogdanoff – Daniel has a degree in Electrical Engineering from Texas A&M University (whoop!) and works closely with oscilloscopes.  He will focus on helpful tips and techniques you should consider when working with benchtop equipment. In addition to working at Keysight, Daniel is also a Contributing Technical Expert for Electronic Design.

 

 

 

 

 

Takuya Furuta, Keysight Technologies

Takuya Furuta – Taku has a wide range of experience and in-depth oscilloscope product knowledge, including oscilloscopes from other manufacturers. His posts will cover the history of oscilloscopes, internal scope architecture and front end filters, and perhaps even some high speed digital applications.

 

 

 

 

 

Johnnie Hancock, Keysight Technologies

Johnnie Hancock – Johnnie began his career as an analog hardware designer and has been around as long as dirt. He has tremendous knowledge across a wide variety of applications with his most recent areas of focus being on oscilloscope-based power supply and automotive serial bus measurements. In his spare time Johnnie enjoys spending time with his four grandchildren and beautiful wife of 40 years.

 

 

 

Mike Hoffman, Keysight Technologies

Mike Hoffman – Mike has a great deal of experience around oscilloscope tips and tricks as well as deep technical knowledge. He will focus most of his topics around these areas and will also cover industry news.

 

 

 

 

 

Kenny Johnson, Keysight Technologies

Kenny Johnson – Kenny is an R&D engineer currently disguised as a marketing engineer. He spent a significant amount of his R&D career working on oscilloscope probes (design and project management) and has 17 patents related to this work. When not earning a paycheck he enjoys running, biking and canyoneering (just like 127 Hours but without the arm thing).

 

 

 

 

Don Schoenecker

Don Schoenecker – Don is a very technical member of the team who will cover a broad range of topics – everything from modular trends to application-specific posts. With over 30 years of experience in the use of test tools to improve product development, Don brings stories and a message of encouragement to help you improve your designs. As a Texas A&M Aggie from Colorado (whoop!), he is happy to be back in the mountains.

 

 

 

 


Robert Lashlee, Keysight Technologies

Robert Lashlee – Robert will write on a wide variety of topics and cover industry trends as well as new oscilloscope measurements and applications.