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Oscilloscopes Blog

7 Posts authored by: Paul Capozzoli Employee

Good news! We're extending the end date for the Infiniium S-Series oscilloscope promotion, "Your Scope. Your Way." to March 31, 2018. 

S-Series Oscilloscope

The S-Series oscilloscopes (500 MHz to 8 GHz) provide you with unmatched measurement accuracy with the best signal integrity and most comprehensive measurement software for signal analysis, compliance, and protocol analysis. With "Your Scope. Your Way." promotion, you can choose ANY ONE of the following value-add offers with each S-Series oscilloscope purchase – at no additional cost:


Offer #1:  Get the new N8888A Infiniium Protocol Decode Software Bundle for free (supports 32 protocols)



PCIe Gen 1Ethernet 10BaseTSVIDFlexRayUSB 2.0



Quad eSPI


Ethernet 100BaseTXCANUFSUSB 3.1 Gen 1

USB 3.0 SuperSpeed Inter-Chip (SSIC)









Offer #2:  Get two N2796A 2 GHz single-ended active probes for free

N2796A 2GHz single-ended active probe


Offer #3:  Get 400 Mpts/channel memory for free (DSOS000-400)


Offer details and T&C can be found here: Promotion ends March 31, 2018 so hurry!

Knowing the quality of the scope’s measurement system is paramount when you need to have accurate measurement results.  While banner specs like bandwidth, sample rate, and memory depth provide a basis of comparison, these specifications alone don’t adequately describe oscilloscope measurement quality.  

Figure 1: Keysight Infiniium S-Series Oscilloscope


Seasoned scope users will also compare a scope’s update rate, intrinsic jitter, and noise floor, all of which enable better measurements.  For scopes with bandwidths in the GHz range, another quality metric involves characterizing a scope’s ENOB. 


What is ENOB in the first place?  It stands for Effective Number of Bits and is really the measure of how well your oscilloscope accurately represents the captured waveform. 


The higher the ENOB, the better the oscilloscope sees the signal the way the components in your design see the signal.


Bits of Resolution and Effective Number of Bits

The ADC is the most recognized component on the oscilloscope. It converts the analog data to digital data. It drives the oscilloscope’s bits of resolution.  It is defined by its sample rate and its signal to noise ratio.  Typically, scopes have 8 bits of resolution, although recently oscilloscopes have added 10 and 12 bit ADCs.


Effective number of bits (ENOB) is a measure of the dynamic performance primarily associated with signal quantization levels of your oscilloscope.


While some oscilloscope vendors may give the ENOB value of the oscilloscope’s ADC by itself, this figure has no value. ENOB of the entire system is what is important.


While the ADC could have a great ENOB, poor oscilloscope front-end noise would dramatically lower the ENOB of the entire measurement system.


Oscilloscope ENOB isn’t a specific number, but rather a series of curves. I am often asked, “what is the ENOB of a specific Keysight oscilloscope?”  Many vendors simply state a specific single number for ENOB, for example, an ENOB of 5.5.  The reality of the situation is this is just not how effective number of bits work. They are frequency dependent. So, it may be 5.5 at one specific frequency setting but is probably not 5.5 across the entire bandwidth of the oscilloscope.


ENOB was established by IEEE in 1993 as a measurement of an oscilloscope’s signal integrity and measurement accuracy. 



It directly correlates to an oscilloscope’s signal to noise ratio.  A higher ENOB will provide better oscilloscope measurements for Jitter, eye height and width, and amplitude.  ENOB is a metric, and does not indicate what is causing signal integrity issues.


Effective number of bits is directly related to the ADC within an oscilloscope.  In general, the bits of resolution within the ADC determines the quantizing levels for your oscilloscope as shown in Figure 1.  



Bits of Resolution

Quantizing Levels

At 1 Volt, Full Scale

 1 LSB =

At 16 mV, Full Scale

1 LSB =



3900 uV

62.5 uV



976 uV

15.6 uV



244 uV

3.9 uV



61 uV

1.0 uV

 Figure 2: Oscilloscope specification comparison


Increasing the number of ADC bits makes each quantizing step size smaller, so the maximum error is minimized.


ENOB is measured as a fixed amplitude sine wave at varying frequencies.  Each curve is created at a specific vertical setting while frequency is varied. ENOB calculations are easy to make. 


  1. First, input a perfect sine wave, capture it on a scope and measure the deviation from the result vs the input.                                                                                                                                                                          For example, input a sine wave from a PSG at 1 GHz into the scope and measure the 1 GHz sine wave. 
  2. Then fit it against a perfect 1 GHz sine wave. 


The difference between the data record and best fit sine wave is assumed to be signal error.  ENOB considers noise, ADC non-linearities, interleaving errors, and other error sources. 


What erodes the bits of resolution?

ENOB is primarily impacted by noise and distortion.  Noise of course effects your signal-to-noise ratio and distortion impacts the total harmonic distortion.   If the base noise of an oscilloscope is greater than the quantizing levels of the ADC, then there is no way for the scope to accurately represent the digital signal level to the least significant bit. 


ENOB values will always be lower than the oscilloscope’s ADC bits.  In general, a higher ENOB is better. However, a couple cautions need to accompany engineers who look exclusively at ENOB to gauge signal integrity. ENOB doesn’t consider offset errors or phase distortion that the scope may inject.  So, it is also important to look at the base noise of an oscilloscope as well as its frequency response (amplitude flatness), phase linearity and gain accuracy to get a complete picture of the accuracy of an oscilloscope.  


In general, by choosing an oscilloscope with superior ENOB, you are choosing a scope with better signal integrity.


You not only impress your colleagues but you also get more accurate waveform shapes, more accurate and repeatable measurements, wider eye diagrams and less jitter.


Figure 3: ENOB of the S-Series DSOS104A 1 GHz real-time oscilloscope from 100 MHz to 1 GHz.


For more information on determining measurement quality, check out the Scopes University S1E4 video, Determining Oscilloscope Measurement Quality.

The New Design and Test Challenges

If you plan on leveraging the work you previously did in your PCIe 3.0 design, you are mistaken. A doubling of the speed from 8 gigatransfers/second to 16 gigatransfers/second has a tremendous impact on both the design and validation of your high speed interconnect technology.


What are the Key Drivers for PCIe 4.0?

Big Data Needs Throughput. Big data is a term for data sets that are so large or complex that traditional data processing applications are inadequate to deal with them. Challenges include analysis, capture, data curation, search, sharing, storage, transfer, visualization, querying, and updating.

Networking Connectivity Applications.   Streaming movies, streaming sporting events, on-demand TV and the multitude of personal videos uploaded and downloaded is growing exponentially. Simply put, PCIe 3.0 cannot keep up with the latest Ethernet specs without increasing the number of lanes that are required. An increase in the number of lanes means increased cost in terms of power, circuit board layout and required components.  

Storage Technology. PCIe 3.0 has been pushed to its limits for SSD (Solid State) storage devices.   Greater interconnect speeds are required to take advantage of latest storage technologies.



Channel Attenuation – Higher frequency means greater channel loss. PCIe 3.0 circuit traces can be made to run up to 16-20 inches if design care is taken. PCIe 4.0, on the other hand, is expected to have a maximum trace length of 10-12 inches. It’s simply impossible to use low-cost FR-4, pass through two connectors, and retain enough signal integrity at these speeds; no matter how robust the transmit and receive equalization schemes at the source and endpoint devices are.

So how do you mitigate the effects of greater channel attenuation?    

The answer is retimer(s). A retimer is actually an extension component or, thought of another way, a smart repeater operating at the physical layer to fine tune the signal. So to achieve 20 inches you can place the retimer at 10 inches from both the transmitter and receiver to ensure the required channel length. The link initialization protocol still negotiates the amount of transmitter de-emphasis (to optimize the receiver equalization), but now this negotiation is done to and from the retimer instead of the transmitter.   Therefore, the Retimer, from a link equalization standpoint, behaves exactly like any endpoint or root complex device. It has an upstream and downstream side so when you boot up it starts the initialization. This essentially doubles the essentially doubling the channel length, but at an added cost.  

Signal Integrity – If you are driving a signal into the channel transmit lane (Tx) and it encounters a change in the impedance profile, it will generate a reflection and, if the return loss of the SERDES is sufficiently high, (meaning poor) it bounces back down the channel. If I have high return loss, then the reflected signal may significantly impact the integrity of the transmitted signal.

So whatever design you use for PCIe 3.0 will not work for 4.0. It is not simply a matter of doubling the data rate, because you now have to meet a more stringent return loss characteristic.   So, you actually have to change the design at the silicon level to effectively give you more return loss at the higher frequencies.

Receiver Calibration – The key challenge is the ever shrinking eye height specification. PCIe 4.0 specifies a minimum eye height of 15 mV after equalization with a maximum bit error rate 1 X 10-12.   You are totally dependent upon your receiver’s ability to maximize the eye height. You now have to calibrate to an even finer grain of detail.


How do you effectively validate and test?

Keysight is the first to market with full support of both PCIe 4.0 TX Tests under the 0.7 version of the specification and includes the extensive reference clock phase jitter tests required under this specification.

The N5393F compliance test software for transmitter testing of PCI Express 4.0 devices allows for BASE spec testing of new PCI Express silicon under the 0.7 version of the PCIe 4.0 specification. The N5393F product supports transmitter testing of speeds up to 16 GBits/s while also supporting intermediate speeds of 2.5G, 5G, and 8GBit/s. In addition, legacy PCI Express 1.1, 2.X, and 3.X transmitter tests are also supported. This software will run on real time oscilloscopes having 12 GHz (or greater bandwidth) including the Z-Series, V-Series, X-Series, Q-Series, and 90000A platforms.

The N5393F also includes reference clock tests defined in the PCIe 4.0 specification, covering phase jitter requirements. Since the vast majority of PCI Express implementations utilize a common reference clock architecture, it is critical to ensure that a candidate reference clock device meets the many different permutations of phase jitter required for each of the 4 data rates. For PCIe 4.0, this represents over 144 different tests that have to be performed on the reference clock.

The N5393F also adds support for transmitter testing over the new U.2 (or SFF-8639) connector. As PCI Express expands its application base to support Solid State Storage Drives (or SSDs), the U.2 connector has been chosen as the main interface used in computer server platforms.

 Keysight PCIe Compliance Application

Easily select any PCIe transmit compliance application.

PCIe Compliance Application Menu

All testing is automated and produces a hyperlinked HTML report file that makes it easy to identify and study any failed or marginal clock jitter parameters.

Learn more about all of Keysight's PCI Express (PCIe) design and test solutions

What is USB Type-C?

USB Type-C is a USB specification for a small 24-pin reversible-plug connector for USB devices and USB cabling.  It supports 10 Gbps data rates, with a path to 40 Gbps, and can source or sink up to 100 Watts (5 Amps at 20 Volts).  In ALT mode it supports DisplayPort, HDMI, MHL, Thunderbolt, and it is possible to support other serial protocols like Ethernet and even PCI Express.


The USB Type-C connectors connect to both hosts and devices, replacing USB Type-B and USB Type-A connectors and cables.  And for the first time, both the connector and the cable direction is reversible! The new form factor is much smaller, essentially the size of a micro USB Type B connector. 


Simplicity and capability for the consumer; one connector for a number of applications and uses, its high data rates, power management capabilities, its ease of use and small size are driving this to be THE interface for laptops, tablets, desktop PC’s, phones, displays, cameras, storage devices, automobiles, external batteries, music jacks, USB hubs, TV’s, and the list goes on. Think about it, use your phone to drive a room projector and while you are presenting the projector is charging your phone.  Only with Type-C is this possible.


But this capability and versatility creates complexity for designers, integrators and validators.  USB Type-C is one of the more challenging architectures for digital design engineers due to the extreme rise time of the digital signals it’s meant to carry. This, combined with the small physical size of this high-density reversible connector and much higher power specifications increases the risk that design engineers will encounter unforeseen interoperability issues at the fundamental, physical layer. These issues can be avoided by leveraging measurement tools to adequately debug and characterize the performance and validate designs with industry standard compliance applications. 


To learn more about USB Type-C, including insights from one of the industry experts, check out our recent Podcast USB Type-C - EEs Talk Tech #1


Diagram courtesy USB-IF


USB Type-C Design

The USB Type-C connector is small, measuring 8.4 mm x 2.6 mm.  There are four differential data lanes on this interface, two pair of Transmit and Receive.  They are specified up to a maximum of 20 gigabits per second performance.  So, this connector is really able to meet most current needs for data throughput with room to grow as data demand continues to rise in the future.


There are four pins on this interface for USB2, shown in grey below, but only two of these pins go through the Type-C cable.  The pins were duplicated to simplify the issue of orientation independence.


There are two pins for sideband use which are utilized for the alternate standards, they're called SBU1 and SBU2.  These alternative modes include DisplayPort, Thunderbolt, and MHL.


Then there are two pins for configuration and the power delivery channel.  These are the CC1 and CC2 shown in purple in the graphic below.  This is a single communication channel where all protocol and power is negotiated to create a contract between the host and device.  The CC pins have three functions; termination/orientation detection, Vconn Supply, and Power Delivery Channel.  The Vconn wire (one of the CC channels) is used to power active or electronically marked cables.  When a connection is made the host initiates communication on the CC lines and provides a list of its capabilities such as power levels, display modes, maximum data rate, thunderbolt, etc. The device then indicates its capabilities and the two end points agree on a contract.   


Finally, we have four pins for Power called the VBus and four pins for ground, and they're located on the diagram below in red and black.  Since there are four of each, this increases the power levels allowed fourfold.  This interface allows for VBus up to 20 volts and current levels all the way up to five amps. That means this interface can carry 100 watts of power! This alone is a major concern as many devices will be fried if the power negotiations are not done correctly and accurately.

Type-C Connector Summary


Type-C Connector Summary:

RX/TX Lanes:  4 High-speed differential data lanes, each specified up to 20 Gbps

CC Lines:  Configuration Channel and Vconn Supply

Vbus and GND:  The Power Pins. There are 4 Grounds and 4 Supply Pins that handle up to 20 volts and a maximum of 5 amps.

SBU Lines:  Sideband Use Pins are extra lines for alternative use.

 D+/- Lines:  USB2.0 operation and link communication


USB Test Implications


Since D+ and D- are USB2, they are assumed to be active in a Type-C design.  Therefore, a full regiment of USB2 test and validation of the device is required in addition to testing Type-C USB3.1.  USB2 runs at 480 Mbps in a half-duplex mode where both protocol and PHY level testing is required.


The configuration pins – CC1 and CC2 have a number of different functions. First, they can determine whether a device is connected.  They can also determine connector orientation thanks to a termination aspect related to the CC pin.  The power delivery channel can be configured with these pins to ensure compatibility between the two devices.  Since there are two of these CC pins and only one is connected through to the link, the other may be used to supply power to the cable (Vconn), should it need it.  


So what are the test implications for the CC pins?   First, there's power delivery channel testing, which means you need to be able to monitor the data coming through that CC pin. You also may need to test with Vconn loaded or unloaded.  Because your device may need to power the cable, you must be able to terminate the device you're going to test.  In addition, there are serious implications if your power exceeds the proper levels.  An incorrect power level could destroy a device, or it could become a safety issue with life threating consequences.  Either way, extensive testing and validation is mandatory.  The key test requirements for you to consider include protocol and PHY testing for a wide range of voltages and currents as both the provider and the consumer of the power.


In the case of USB3 testing, you must test both TX1 and TX2 ports, which will require doubling the test time. You can either do this testing either by taking out the connector and flipping it over and sticking it back in, or you can do an electronic flip.  And if you’re testing Thunderbolt 3 over Type-C you will need to know that all four lanes can be TX or RX.


There are even narrower margins when dealing with 10 or 20 gigabits per second data since the eye height and width are decreased significantly.  Since you are concerned about losses in the path, you must ensure you do not have to much loss in the path to your measurement equipment. 


Finally, there is testing Type-C alternative modes.  You will need to control the CC line to get into the required alternate mode.  Testing the configuration channel is very important, not only do you need to verify it, but you also have to use it to control states of your device.


Type-C incorporates many protocols, very high data rates, power delivery, and of course USB2, and the number of signal to observe and control present a number of challenges for testing.  The good news is that Keysight’s oscilloscopes can help you test and validate your Type-C device with our full range of protocol and physical layer test and compliance applications.


Keysight’s Type-C test and validation solutions with oscilloscopes:


USB 3.1 Compliance Application – for Gen 1 (5 Gbps) and Gen 2 (10 Gbps)

Keysight’s U7243B USB 3.1 validation and compliance test software provides a fast and easy way to verify and debug your USB 3.1 products.  This software allows you to automatically execute USB 3.1 electrical tests and then displays the results in a flexible report. In addition to the measurement data, the report provides a margin analysis that shows how closely your device passed or failed each test to help you determine the exact signal levels within your design.


USB 3.1 compliance test application from Keysight Technologies

USB 3.1 Compliance


USB 3.1 Protocol Trigger and Decode

Keysight’s N8821A USB 3.1 Gen1/Gen2 protocol trigger and decode application includes a suite of configurable protocol-level searches and software-based triggering specific to USB 3.1. The multi-tab protocol viewer shows you the correlation between the waveforms and the selected packet using a time-correlated tracking marker so you can quickly move between the type-c physical and protocol layer information.

USB 3.1 protocol decode with time-correlation from Keysight Technologies

USB 3.1 protocol decode with precise time-correlation between waveforms and listing


USB PD Protocol Compliance Software

Keysight’s N8840A USB power delivery (PD) electrical and protocol compliance test software helps you quickly validate and debug your USB power delivery provider, consumer, dual-role device, and eMarker cable. USB power delivery compliance test software allows you to automatically execute a USB Type-C power delivery compliance test plan and then see the results in a comprehensive report (.pdf, .csv, and .xml).  These tests conform to the latest USB-IF USB PD specification and test plan and perform electrical physical layer BMC-PHY tests, protocol layer BMC-PROT tests, and power state BMC-POW tests. 


USB PD Compliance from Keysight Technologies

USB PD Compliance


USB PD Triggering and Decode

You can extend your oscilloscope’s capability with the N8837A USB-PD protocol triggering and decode application which makes it easy to debug and test designs that include USB-PD protocols using a Keysight Infiniium oscilloscope. This application can set up your USB-PD protocol decode in less than 30 seconds and access a rich set of integrated protocol-level triggers. You can save time and eliminate errors by viewing time-correlated packets at the protocol level and quickly troubleshoot serial protocol problems by identifying their timing or signal integrity root cause.

USB-PD protocol decode with time-correlation from Keysight Technologies

USB-PD protocol decode with precise time-correlation between waveforms and listing


In summary, it is critical to validate your design to industry specifications to ensure safety as well as device interoperability for new Type-C designs.  Keysight’s oscilloscopes can help you achieve your testing goals and help to get your product to market faster.

Keysight recently introduced the industry’s first (and only) certified Thunderbolt 3 transmitter compliance application, N6470A


What is Thunderbolt 3?

Thunderbolt is the brand name of a hardware interface that allows the connection of external peripherals to a computer.  Thunderbolt 3 was developed by Intel and was announced in the first half of 2015.  Its claim to fame is speed; two independent 20 Gbps links into one logical 40 Gbps link.  Thunderbolt 3 is a revolutionary I/O technology that supports high resolution displays and high performance data devices through a single compact USB Type-C port.  It sets new standards for speed, flexibility, and simplicity.  Multiple devices can be daisy chained to create a Thunderbolt network.  While Thunderbolt one and two just specified active electrical and also optical cables, version three also supports connecting devices with passive cables at full speed. The Type-C connector brings more speed, more pixels (4K), more power (100 Watts), and more protocols (Thunderbolt, DisplayPort, USB, and PCIe).   From the Intel Thunderbolt website, they depict the following:  

Thunderbolt was developed to simultaneously support the fastest data and most video bandwidth available on a single cable, while also supplying power. The USB group introduced the USB-C connector, which is small, reversible, fast, supplies power, and allows other I/O in addition to USB to run on it, maximizing its potential. So in the biggest advancement since its inception, Thunderbolt 3 brings Thunderbolt to USB-C at 40 Gbps, fulfilling its promise to create one compact port that does it all. As Intel states on their website, Thunderbolt 3 mode is a single cable that provides four times the data and twice the video bandwidth of any other cable, while supplying power. It’s unrivaled for new uses, such as 4K video, single-cable docks with charging, external graphics, and built-in 10 Gigabit Ethernet networking.  Simply put, Thunderbolt 3 delivers the best USB-C.   You can connect two 4K 60 Hz displays with amazing resolution, contrast, and color depth to see your photos, videos, applications, and text with remarkable detail.   Just to give you an idea of the performance, you can transfer a 4K high definition movie in less than 30 seconds. You can connect two 4K displays with nearly 16 million more pixels than an HDTV. The latest MacBook Pro 2016 Includes Thunderbolt 3 with USB-C.  Some other Manufacturers with notebooks and laptops supporting Thunderbolt 3 are HP, Acer, Dell, Alienware, Asus, Lenovo, MSI, and Razer Blade.


Who needs to do Thunderbolt 3 Compliance testing?

Manufacturers of Thunderbolt 3 chip sets, servers, workstations, laptops, gaming PC’s, industrial cameras, high speed PCIe storage, displays, and adapters are required to perform industry standard compliance and validation testing to the industry compliance specification “USB Type-C Thunderbolt Alternate Mode Electrical Host / Device Compliance Test Specification”. Their key issues are ‘how do I ensure the transmitter is in spec?’, ‘how much time will it take to make all the required measurements?’ and ‘how can I make sure my test results are repeatable?’   At 20 Gbps, signals are significantly impaired when conducted electrically over short distances. Analyzing these signals is critical for chip manufacturers characterizing silicon, or a system integrator doing debug, validation, or compliance.

The good news is that Keysight’s high speed Infiniium oscilloscopes are now the only scopes that are currently specified for Transmitter compliance testing.  Here is what this standard specifies for transmit compliance test equipment:


Required Test Equipment Capabilities

  • DC to 21±1GHz, -3db bandwidth or greater
  • 50G sample/sec sampling rate or greater, sampling 2 channels simultaneously
  • Sample memory: 2 channels at 50 M samples per channel or greater
  • 1st and 2nd order CDR capability
  • Equalization for USB3.1 model capability


Recommended Test Equipment:


Our N6470A Thunderbolt 3 electrical transmit compliance test application

The N6470A Thunderbolt 3 electrical test software gives you a fast and easy way to verify and debug your Thunderbolt designs for both silicon validation as well as end products like storage devices or motherboards. The Thunderbolt 3 electrical test software allows you to automatically execute Thunderbolt 3 electrical transmitter tests and displays the results in a flexible report format.

In addition to the measurement data, the report provides a margin analysis that shows how closely your device passed or failed each test. The N6470A Thunderbolt 3 electrical test software covers the prescribed test methods and parameters required for Thunderbolt electrical certification testing. This produces results that are consistent with those obtained during official certification at approved test labs and informational testing at plugfests.  In addition to automatic setup and execution of the transmitter tests, the N6470A Thunderbolt 3 electrical test software also provides automatic setup and control of the crosstalk generator source, a required condition for electrical testing during official certification tests.

N6470A Automation

  • Test setup wizard guides you through test selection, configuration, connection, execution, and results reporting
  • Measurement connection setups are displayed
  • Automated setup and control of the required crosstalk source(s), and the oscilloscope setup is automatically configured for each test
  • Test results report documents test configuration, measurements made, pass/fail status, margin analysis, and waveforms

N6470A Extensibility

  • Run tests with live or saved waveforms for easy regression testing if specification requirements change
  • Create and fully integrate custom tests, configuration variables, and connection instructions
  • Insert external application calls into the run sequence, such as MATLAB scripts or your device controller
  • Configure additional external instruments used in your test suite


Keysight provides a simple, repeatable automated and unattended calibration and test execution using automation software for transmit test.  All Type-C PHY standards are addressed by Keysight’s Test platform; Thunderbolt 3, USB 3.1, and DisplayPort. Our solution helps you with pre-compliance testing with jitter, rise time and voltage measurements. For a complete presentation please see this URL: Thunderbolt 3 over Type C - Overcoming Test Challenges.


The N6470A Thunderbolt 3 Compliance Test Software for Infiniium oscilloscopes is priced at $16,000* for a fixed license and $24,000* for a transportable license.

The full N6470A compliance test suite



N6470A Real-Time Eye diagram for 10 waveforms with margin analysis




*All prices are in USD and are subject to change

You may already be familiar with the Keysight S-Series oscilloscopes. They offer the best signal integrity for bandwidths up to 8 GHz, which is enabled by a set of custom technology blocks to give you:

Keysight S-Series oscilloscope

  • 4X the vertical resolution with the world’s fastest 10-bit analog to digital converter (ADC) that runs at 40 Gigasamples/sec
  • Greater signal detail from a front end with 50% less noise than other portable oscilloscopes
  • The ability to see your signal the way the components in your design see that signal with the highest effective number of bits (ENOB)
  • Superior timing and jitter measurements thanks to timebase accuracy of 12 parts per billion
  • Quick and easy analysis with more than 42 software applications
  • And more! (Intrigued? Check out the data sheet)

Whether you have already purchased an S-Series oscilloscope, or are currently in the market for something in the 500 MHZ – 8 GHz range, you’ll want to check out some of the recent enhancements that make this great oscilloscope even better.  Here are just a few:

The new N7020A Power Rail Probe

The Keysight N7020A power rail probe was designed for making power integrity measurements that need mV sensitivity when measuring noise, ripple, and transients on DC power rails. Many of today’s products have tighter tolerances on their DC power rails and the N7020A power rail probe is engineered to help assure your products meet these tighter tolerances by measuring periodic and random disturbances (PARD), static and dynamic load response, programmable power rail response and similar power integrity measurements.

Key features:

  • Low noise: 1:1 attenuation ratio probe for greater signal to noise ratio. Only 0.9 mVpp at 1 GHz and a setting of 2 mV/div
  • Large offset range: +/-24 V offset range enables you to set your oscilloscope at maximum sensitivity and have the signal centered on the screen to view down at 1 mV/div
  • Low DC loading: 50 kΩ DC input impedance will minimize load on DC power rails
  • High bandwidth: 2-GHz bandwidth makes it very useful for finding high-speed transients that can have detrimental effects on clocks and digital data

When you combine the power rail probe with the signal integrity of the S-Series you can validate power distribution design specs more accurately than any other probe/scope solution.

Keysight N7020A Power Rail probe connected to the S-Series oscilloscope

 The N7020A Power Rail probe connected to the S-Series oscilloscope


The new N2820A High Sensitivity Current Probe

As modern battery-powered devices and integrated circuits become more green and energy efficient, there is a growing need to make high-sensitivity, low-level current measurements to ensure the current consumption of these devices is in acceptable limits. The Keysight N2820A high-sensitivity probe is engineered to make high-dynamic-range, high-sensitivity measurements to meet these measurement challenges.

The ultra-sensitive N2820A AC/DC current probe can support measurements from 50 uA to 5 A on Keysight oscilloscopes using a make-before-break (MBB) connector, which allows you to quickly probe multiple locations on your DUT without having to solder or unsolder the leads.

It connects to two oscilloscope channels to provide simultaneous low- and high-gain views for wider dynamic range measurement. When used in combination with the Infiniium S-Series high-definition oscilloscopes this probe can deliver the ultimate high-sensitivity measurement solution.

Keysight N2820A current probeThe Keysight N2820A current probe


Type-C Power Delivery Decode

The Keysight N8837A Type-C Protocol Trigger and Decode software is the industry’s first oscilloscope-based USB-PD protocol decode/trigger solution.  This provides insights to USB PD engineers working on ALT mode (alternate mode) for DisplayPort, Thunderbolt 3.0, and MHL.  The S-Series are the only oscilloscopes that support hardware serial trigger on BMC signals, and allow you to quickly identify the root cause of both protocol and signal integrity issues.

Type-c decodingKeysight Type-C Power Delivery Protocol Decode


MultiScope Software Application

The Keysight MultiScope software application (N8834A) provides the ability to connect up to 10 Infiniium Series oscilloscopes for 40-channels of acquisition with a tight time correlation between the scopes with very low inter-scope intrinsic jitter.  The software allows you to perform multi-lane analysis for applications such as optical networking, MIMO, DDR memory and high-speed serial standards.  These signals are presented live on a PC with the N8900A Infiniium analysis software or on the leader scope, eliminating the need for a PC.


eSPI Protocol Decode and Trigger Application

The Keysight N8835A Enhanced Serial Peripheral Interface (eSPI) was developed by Intel as a successor to its Low Pin Count (LPC) bus. So it can test and trigger on not only legacy SPI data but also embedded controller (EC), baseboard management controller (BMC) and Super-I/O with extensive triggering for all key commands and responses. This standard allows designers to use 1-bit, 2-bit, or 4-bit communications at speeds from 20 to 66 MHz.

The Keysight N8835A eSPI protocol decode
The Keysight N8835A eSPI protocol decode


New Serial Data Analysis Tool Bit Error Rate Eye Contour Software

The Keysight Serial Data Analysis tool (N5394A) has been enhanced to include Bit Error Rate (BER) eye contour capability, allowing you to cut testing time from weeks to hours!  It extrapolates noise and jitter to show how an eye will close over time at various error rates.  This allows DDR4/LPDDR4 designers to make BER measurements on command and data signals. The DDR4 and LPDDR4 JEDEC spec now have new data and timing design specifications with a Bit Error Rate of <1 x 10 -16.   The Keysight BER contour measurement method addresses these new requirements.

Keysight oscilloscope eye contours based on different bit error rates
Eye contours based on different bit error rates


New E-Band Signal Analysis Reference Solution

The Keysight N8838A E-band signal analysis solution delivers an integrated, low-cost wideband RF testing solution.  Using a high-performance oscilloscope with an external mixer and signal generator we provide an integrated down-conversion system that delivers 2.5 GHz of analysis bandwidth over the E-band frequency range of 55 to 90 GHz.



New CAN, LIN, FlexRay and CAN-FD protocol triggering and decode

The Keysight N8803C software can help electronic system designers test and debug the physical layer of automotive serial buses faster.  The CAN, LIN, FlexRay, and CAN-FD serial buses are the backbone for communication among many separate controllers, sensors, actuators, and ECUs located throughout automotive and industrial designs. These serial bus interfaces provide content-rich points for debug and test and the N8803C CAN, LIN, FlexRay, CAN-FD protocol decode is your view into these signals.

The Keysight N8803C CAN Protocol Decode Software
The N8803C CAN protocol decode software


New PAM-4 Measurement Application


The Keysight N8836A analysis software helps you quickly identify design flaws by characterizing PAM-4 signals.


Available PAM-4 real-time eye measurements include:

  • Eye width, eye height, eye skew (relative) for each PAM-4 eye
  • Level mean, RMS, and “thickness” for each level


PAM-4 waveform measurements include:

  • Level mean, RMS, and “thickness” for each level
  • Data TIE for each threshold
  • Rise/Fall times for each of 6 PAM-4 transition types
  • Support for CTLE, FFE, and DFE Equalization




As you can see our engineering teams have been hard at work continually adding new capabilities to our S-Series oscilloscope solution set to help you get your job done faster.

By looking for an oscilloscope with good signal integrity you not only can impress your colleagues, but you also get:

  • More accurate wave shapes
  • More accurate and repeatable measurements 
  • Wider eye diagrams
  • And less jitter

Signal integrity is the primary measure of signal quality.  When you need to view small signals, or small changes on larger signals; it is critical that you see those signals the way the components in your design see those signals.

Oscilloscopes themselves are subject to the signal integrity challenges of distortion, noise, and loss.  Scopes with superior signal integrity attributes provide a better representation of signals under test, while oscilloscopes with poor signal integrity attributes show a poorer representation of signals under test.  This difference impacts your ability to gain insight, debug, and characterize designs.

Results from oscilloscopes with poor signal integrity can increase risk in development cycles times, production quality, and components chosen.  To minimize this risk, you will want to choose an oscilloscope that has high signal integrity attributes.

Let’s take a look at some of the error attributes that effect signal integrity

The Oscilloscope’s Noise Floor

Having a scope with low noise (high dynamic range) is critical if you really want visibility to small currents and voltages, or to see small changes on larger signals.  You cannot see a signal smaller than the noise floor of the oscilloscope.

Noise can come from a variety of sources, including the front end of the oscilloscope, the analog to digital converter (ADC) in the scope and the probe or cable used connected to the device. The ADC itself has quantization error. For oscilloscopes, quantization noise typically plays a lesser role in contribution of overall noise than the front end of the oscilloscope which plays a more significant role.

Most oscilloscope vendors will characterize noise for a specific model number and include these values on the product datasheet. If not, you can find out yourself.  It’s easy to measure in just a few minutes. Disconnect all inputs from the front of the oscilloscope and set the scope to 50 Ω input path.  Set the sample rate at high.  Run the scope with infinite persistence and see how thick the resulting waveform is. The thicker the waveform, the more noise the scope is producing internally.

Each oscilloscope channel will have unique noise qualities at each vertical setting. You can view the noise visually just by looking at wave shape thickness, or you can be more analytical and take a Vrms AC measurement to quantify.   These measurements will enable you to know how much noise each oscilloscope channel has at various vertical settings to measure signals that are less than the noise of the scope. All acquired vertical values are subject to deviation up to the noise value of the oscilloscope. Noise impacts both horizontal as well as vertical measurements.

The lower your oscilloscope’s noise, the better the measurement results will be.

Figure 1:  Keysight S-Series oscilloscope and a competitive scope analyzing the same signal.  Which would you like for your signal measurements?

Frequency Response

Each oscilloscope model will have unique frequency response that is a quantitative measure of the scope’s ability to accurately acquire signals up to the rated bandwidth. These requirements must be kept in order for oscilloscopes to accurately acquire waveforms:

  • Capture signals must be within the bandwidth of the oscilloscope
  • the scope should have a flat frequency response
  • And a flat phase response


Missing any one of these requirements will cause an oscilloscope to inaccurately acquire and draw a waveform and provide misleading measurement results.

Fast signal edges contain multiple harmonics, and scope users expect the oscilloscope to accurately measure each harmonic component using the correct magnitude. Ideally oscilloscopes would have a uniform flat magnitude response up to the bandwidth of the scope, with the signal delayed by precisely the same amount of time at all frequencies (phase). Flat frequency responses indicate that the oscilloscope is treating all frequencies equally, without a flat phase response the scope will show distorted waveforms.

Frequency-response correction filters produce flat responses for both magnitude and phase for more accurate waveforms.  Some oscilloscopes have strictly analog front-end filters that determine frequency response, while others apply correction filters in real time. Combining correction filters with front-end analog filters creates flatter magnitude and phase responses verses raw analog filters alone. High-quality oscilloscopes include both analog as well as correction filters to create a uniform and flat frequency response.

Figure 2: The flat frequency response of the Keysight S-Series oscilloscope.


Bits of Resolution and Effective Number of Bits

The ADC is the most recognized component on the oscilloscope. It converts the analog data to digital data. It drives the oscilloscope’s bits of resolution.  It is defined by its sample rate and its signal to noise ratio.  Typically most scopes have 8 bits of resolution, although recently oscilloscopes have added 10 and 12 bit ADCs

Effective number of bits (ENOB) is a measure of the dynamic performance primarily associated with signal quantization levels of your oscilloscope. While some oscilloscope vendors may give the ENOB value of the oscilloscope’s ADC by itself, this figure has no value. ENOB of the entire system is what is important. While the ADC could have a great ENOB, poor oscilloscope front-end noise would dramatically lower the ENOB of the entire measurement system.

Oscilloscope ENOB isn’t a specific number, but rather a series of curves. ENOB is measured as a fixed amplitude sine wave that is swept in frequency. Each curve is created at a specific vertical setting while frequency is varied. The resulting voltage measurements are captured and evaluated. Using time-domain methods, ENOB is calculated by subtracting the theoretical best fit sine wave from what was measured. The error between these curves can come from the front-end of the oscilloscope from attributes such as phase non-linarites and amplitude variations over frequency sweeps.

ENOB values will always be lower than the oscilloscope’s ADC bits.  In general, a higher ENOB is better. However, a couple cautions need to accompany engineers who look exclusively at ENOB to gauge signal integrity quality. ENOB doesn’t take into account offset errors or phase distortion that the scope may inject.

Figure 3: ENOB of the Keysight S-Series DSOS104A 1 GHz real-time oscilloscope from 100 MHz to 1 GHz.


Intrinsic Jitter (time interval error)

An oscilloscope jitter measurement floor impacts your time interval error, decreases your eye width, can cause timing violations, and compounds accuracy of correlated measurement across channels.

Measured in picoseconds rms or picoseconds peak-to-peak.  Contributions to jitter naturally occur in high-speed digital systems. Jitter sources include thermal and random mechanical noise from crystal vibration.  Excessive jitter is bad.  If you need to make jitter measurements, understanding how well your oscilloscope will make those measurements is critical to interpreting your jitter measurement results. Oscilloscopes sample and store digitized waveforms. Each waveform is constructed of a collection of sample points. A perfect oscilloscope would acquire a waveform with all sample points equally spaced in time. However, in the real world, imperfections in the internal scope circuitry horizontally displace the ADC sample points from their ideal locations and this value is represented in the jitter measurements that the oscilloscope makes. Oscilloscopes themselves have jitter and when they make a jitter measurement, they can’t determine which portion of the jitter measurement result came from the device under test versus the scope itself.

Oscilloscope jitter can come from interleaving errors, the jitter of the ADCs sample clock input signal, and other internal sources. This is also called the intrinsic source jitter clock (SJC). Oscilloscope vendors shorten the term to “intrinsic jitter” and use this term to mean the minimum intrinsic jitter value over short time period.  Jitter measurement floor is a function of noise, signal slew rate, and intrinsic jitter.  The term “jitter measurement floor” refers to the jitter value that the oscilloscope reports when it measures a perfect jitter-free signal. The scope’s circuitry that is associated with horizontal accuracy is known as the time base. The time base is responsible for time scale accuracy as well as the horizontal component of jitter. Oscilloscopes with well-designed time bases contribute less to horizontal jitter component of jitter and hence will report a lower value.

Figure 4: Measuring the Jitter using a histogram of a TIE measurement.


And of course don’t forget probing

The probe connected to the oscilloscope becomes an additional load driven by the signal source.  Resistive, capacitive and inductive loading effects must be considered.   There are effects for varying lead length/span of a probe tip.  Longer wires may get you a convenience of probing physically separated test points easily, but there is a trade off in doing that.  The key here is that shorter is better.  Keep the probe’s input tips, leads, connectors, and grabbers in front of your probe input as short as possible, and you will get a better result. Learn more about this in Kenny’s earlier post: Do yourself a favor, read this.

Consider probe noise and its effects on measurement accuracy.  Choose a probe with a lower attenuation ratio for lower noise measurements.  Lower attenuation means higher signal-to-noise ratio (less noise), but lower input resistance, lower dynamic range, and lower common mode range.


Your oscilloscopes’ signal integrity makes a big difference in measurement results.  So choose a scope with superior signal integrity.  Evaluate noise, frequency response, ENOB, and jitter measurement floor. An easy way to do this is to ask a scope manufacturer to supply you with the data they’ve already taken.

As unit intervals continue to shrink, every picosecond matters.  You can’t afford to have your test and measurement equipment impact your measurement and analysis.  Understanding an oscilloscope’s characteristics and how they can impact your measurements is imperative.


Want to learn more about oscilloscope signal integrity? Check out the Evaluating Oscilloscope Signal Integrity application note.