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2017

Calling all power electronics engineers! Can you please help me by completing this short survey?

 

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I was excited and intimidated when I took the opportunity to write this blog post for Keysight EEsof EDA.  I had some exposure to what Keysight ADS is and what you can use it for in college – but to write tutorial blogs to assist engineers who design the next satellite that will be launched into space?  That seemed like a daunting task. 

 

I participated in a training session that walked me through designing a Low Pass Filter and I wanted to share it with you. 

I was able to design this low pass filter in 3 easy steps.

 

Step 1:  Start up ADS and create your workspace. 

If you don’t have ADS get a free 30-day trial here.

 

Choose your directory and name your workspace. 

 

Select only the Analog/RF library, and uncheck all others if needed.  This means that the components from the RF/Analog library will be available for later. 

 

 

Name your library, and select the Standard ADS Layers .0001 mil layout resolution.  Make sure everything looks correct, and click “Finish”.

 

Your workspace is now created!  

 

Step 2:  Build your schematic.

 

 

By expanding to cell view, you can now see that your schematic pops up in your workspace. 

 

 

 

Select the components you need by clicking on the component and dropping it on the schematic page.  You can rotate parts by using the toolbar icon or cursor on or use the cursor to drag the handle on the component.  Connect up the components with the wire button, and don’t forget to ground your circuit! 

 

 

 

To change the values, units, or even the name of your component, double-click the component and make changes as needed.

 

 

Step 3:  Set up an S-Parameter Simulation.

Select the “Simulation-S_Param” on the palette and drop it on your schematic area.  Insert the port terminations, and make sure to ground them.

 

 

To set up the simulation, double-click the gear on the schematic. Change the step size and frequency range.  I used a step size of .5 going from 1 GHz to 10 GHz.  Click OK, and now you are ready to simulate!

 

Click the gear (alternatively, use F7), select simulate, and fix any errors that may have shown up.

ADS has a variety of different plots.  I’m going to create a rectangular plot. 

 

 

Select the rectangular plot and select which S-parameter measurement you want to use, select your units (S-parameters are usually measured in dB), and click ok. You can zoom in and out with your mouse, and view all with this icon:

 

 

Put a marker on the trace, and you can move them around with the red arrows. 

 

 

 

Now I’ve created a low pass filter and plotted an S-parameter measurement. 

 

That wasn’t so bad, was it?

 

I skipped a few steps. For a complete set of instructions check out the attached PDF at the bottom of this blog post.

 

For other getting started topics, check out our video playlist: 

www.keysight.com/find/eesof-ads-tutorial-videos

If you’re looking for help designing a broadband Power Amplifier (PA), the 3D Smith Chart may be just the answer for you. 3D Smith Charts can be easily generated from Keysight’s Advanced Design System (ADS) software using Python scripts. You don’t even need to know Python. A Data Link with Python in ADS provides a simple way for you to call preprogrammed Python scripts, complete with bi-directional data transfer.

 

The Cylindrical 3D Smith Chart (also called the "Smith Tube") was pioneered by a team at Baylor University led by Dr. Baylis and presented in a landmark IEEE WAMICON paper in 2014 that introduced the "Smith Tube" in the literature for the very first time (see more references at the end). 

 

Here are 5 ways a 3D Smith Chart can help you design a broadband PA:

 

1. It gives you a unique perspective and fast insight into resonance.

LC impedance matching network topology, S22 response

 Figure 1.  This LC impedance matching network topology may at first seem simple to analyze.

s22 response, smith chart

 

Figure 2. It’s not always obvious, why, for example, a particular resonant inflection occurs in the S22 response such as the one shown at 1.52 GHz.

 

While an LC impedance matching network for a PA design may seem simple to analyze, understanding why a resonance inflection occurs is not always easy (Figure 1 and 2). If you can get to the root of the resonance, you can exploit it to build a broadband match. A 3D Smith Chart allows you to do just that. By plotting the impedance shift of each individual matching component at each frequency, you can find the cause of a resonance and determine what adjustments are needed to mitigate its effects (Figure 3).

3D Smith Chart, Smith Chart

 3D Smith Chart, Smith Chart3D Smith Chart, Smith Chart

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3. From these 3D plots, now we can see the resonance around 1.5 GHz occurs due to the impedance from C3, which is “spinning” around the impedance set by the rest of the network.

 

2. You can create a solid 3D surface. 

3D Smith Chart, Smith Chart, EVM contours, EVM surface3D Smith Chart, Smith Chart, EVM contours, EVM surface

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4. An example EVM surface represented by a set of load-pull contours is shown. By viewing the entire surface in this format, some interesting things stand out that aren’t immediately obvious from the contours.

 

In PA design, load pull is typically used to sweep a transistor's load and plot contours of constant performance (e.g., output power). Load-pull contours are a flat representation of a 3D surface. Sometimes they are easy to interpret and design with, but using them to interpret the surface topology of complex structures can be challenging. Plotting the entire surface as a 3D solid structure can be very insightful in some instances, for example, finding the minimum EVM region of a PA under a modulated input signal (Figure 4).

 

 3. You can extend contours to the third dimension.

3D Smith Chart, Smith Chart

Figure 5. A plot of load-pull contours in 3D (with the third dimension being frequency) is shown. 

 

Suppose you’re trying to design an amplifier to deliver high output power over a broad bandwidth. Typically, this would be done by performing load-pull simulations at several frequencies and then trying to build a matching network to hit the correct loads to deliver the power required for each individual frequency. Using a 1D Smith Chart, this would be a long, difficult process, resulting in so much clutter on the plot that you would likely be unable to make sense of the results. Typically, a designer can only visualize one contour or single frequency set of contours at a time. Plotting the same contours on a 3D Smith Chart “spreads out” the contours and allows you to visualize more information at once (Figure 5).

 

 4. You can create a surface from cross-sectional data.

 3D Smith Chart, Smith Chart

Figure 6. Another way to visualize the frequency dependent power contours in Figure 5 is to create a solid surface by connecting the contours together in the Z dimension.

 

With a 3D Smith Chart you can create a solid “triangulated” surface by connecting the contours together in the Z-dimension. This provides you yet another way to visualize the contour data in 3 dimensions. In some cases, contour surfaces are easier to understand than repeated individual contours.

 

 5. You can plot your 3D matching network and frequency-dependent load-pull contours on the same 3D Smith Chart.

3D Smith Chart, Keysight ADS, ADS Python Data Link Basics3D Smith Chart, Smith Chart

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 7.  The 3D matching network and the frequency-dependent load pull contours are plotted on the same 3D Smith Chart.

 

By plotting this data together, it’s intuitive to adjust the matching network component values so that the impedance "threads the needle" though the Pout power contour level across the frequency band. An interactive highlight marker in ADS helps you gain insight into what adjustments are needed.

 

 4 ways to boost simulation data processing using python          Matt Ozalas

These 5 applications of the 3D Smith Chart came from my friend, Matt Ozalas, RF Design Expert. Hear from him yourself in his May 4th, 2017 webcast, Four Ways to Boost Simulation Data Processing Using Python.

 How to Design a Power Amplifier: The Basics

 You might recognize him from his YouTube Series, How to Design a Power Amplifier: The Basics.

 

 free trial, ADS, Keysight

Apply today for your free 30-day full version trial of Keysight ADS. 

References

 For more information, see the following IEEE papers:

1. Joseph Barkate ; Matthew Fellows ; Jennifer Barlow ; Charles Baylis ; Robert J. Marks.  "The Power Smith Tube: Joint optimization of power amplifier input power and load impedance for power-added efficiency and adjacent-channel power ratio". IEEE Wamicon, 2015. http://ieeexplore.ieee.org/document/7120398/

2. Matthew Fellows ; Matthew Flachsbart ; Jennifer Barlow ; Joseph Barkate ; Charles Baylis ; Lawrence Cohen ; Robert J. Marks.  "Optimization of power-amplifier load impedance and waveform bandwidth for real-time reconfigurable radar".  IEEE Transactions on Aerospace and Electronic Systems ( Volume: 51, Issue: 3, July 2015 ).  http://ieeexplore.ieee.org/abstract/document/6857780

3. Matthew Fellows, Sarvin Rezayat,Jennifer Barlow, Joseph Barkate, Alexander Tsatsoulas,Charles Baylis,Lawrence Cohen. "The bias smith tube: Simultaneous optimization of bias voltage and load impedance in power amplifier design." Radio and Wireless Symposium (RWS), IEEE. 24-27 Jan. 2016. http://ieeexplore.ieee.org/document/7444408/

4. Charles Baylis; Matthew Fellows; Matthew Flachsbart; Jennifer Barlow; Joseph Barkate; Robert J. Marks.  "Enabling the Internet of Things: Reconfigurable power amplifier techniques using intelligent algorithms and the smith tube".  2014 IEEE Dallas Circuits and Systems Conference (DCAS).  http://ieeexplore.ieee.org/document/6965341/

 

You are designing a power amplifier and have a nonlinear device model. You may want to know what load gives the maximum power-added efficiency (PAE) while the device is delivering a specified output power and while it is operating below some maximum allowable gain compression. How do you do this? Andy Howard, a Senior Application Engineer at Keysight Technologies, has created a simulation example that will help you overcome this design challenge. 

The plots below show results in the Load_Pull_Using_Loads_From_File_Data_Mining data display. Andy has specified the desired output power of 32 dBm. The maximum allowed gain compression is increased from 2 to 3 to 4 to 5 dB. The PAE increases from about 49% to > 67%:

This example has two swept-power load pull simulations. Equations are used to interpolate the data to find the load that gives the maximum PAE while delivering a specified power while below a specified maximum amount of gain compression. One of the load pull simulations reads in loads you have specified graphically on a Smith Chart. The other load pull simulation allows you to specify a circular region on a Smith Chart.

To learn more, download Andy's swept-power load pull simulation example on Keysight EEsof Knowledge Center. (a login required) http://edadocs.software.keysight.com/pages/viewpage.action?pageId=39554744

Interested in Keysight ADS?  

sipro, pipro, free trial

Go straight to the Knowledge Center article (login required): How to Create your own 3D Smith Chart Plots

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Engineers surround themselves with the best tools they can find. For the RF engineer, a new tool discussed in the literature recently is the Cylindrical 3D Smith Chart (also called the “Smith Tube”).  This 3D version of the classical Smith Chart allows engineers to explore data in new and interesting ways. It was pioneered by a team at Baylor University led by Dr. Baylis and presented in a landmark IEEE WAMICON paper in 2014 that introduced the "Smith Tube" in the literature for the very first time (see more references at the end). 

 

The Smith Chart was developed in the 1930’s as a graphical way to transform complex impedances to reflection coefficients.  For an unassuming diagram based on slide rules, the Smith Chart is still enormously relevant in the digital age; in fact, most engineers try to fit so much data into this small circle that we end up with more lines, arcs, and circles than we can ever interpret.  With access to so much data these days, things can get awfully cluttered.  Now, it’s possible to make sense out of more data by adding a third dimension to the classical Smith Chart plot.  For example, on the classic Smith Chart, you can visualize how impedance changes versus frequency.  On the 3D Smith Chart, you can understand how impedance changes versus frequency AND voltage…or gain…or input power, or anything you can imagine!   

 

To create a 3D Smith Chart, simply take a standard Smith Chart and stack it on an arbitrary Z-axis (Figure 1). The Z-axis can take on any value or scale you desire, such as frequency, power, or transmission line length. The composite plot is then just a stacked set of Smith Charts with each "slice" representing a single classical Smith Chart for a given Z value. 

 3D Smith Chart, Smith Chart

Figure 1. The 3D Smith Chart is analogous to generating a plot in Cylindrical Coordinates, where a cross-sectional plane is represented in polar form by (r,Ɵ) , and the Z-axis is specified in the standard Cartesian Coordinate system.

 

3D Smith Charts can be easily created using a Python library which can be set up to plug directly into Keysight ADS, which allows you to access this capability to plot and analyze simulation or measurement data.

 

How to Set Up Your Own 3D Smith Chart

 

The first step is to set up the ADS Data Link with Python, which provides a simple way to call a Python script from ADS, complete with bi-directional data transfer. Find out how in the video below. Registered users can also view the application note, ADS Data Link with Python

ADS Data Link Basics (Part 1 of 3) - YouTube 

 

To use the ADS Data Link with Python, you must first install Python Anaconda (available at no charge), and then load the functions into ADS. The ADS and Python functions needed for this setup are available in the workspaces (for registered users). A Data Display with interactive step-by-step instructions is included in the workspace and will walk you through the setup for your particular machine (Figure 2).  

 3D Smith Chart, Keysight ADS, ADS Python Data Link Basics

Figure 2. For most ADS users, this simple data display page should be all that’s needed for setup.

 

Following setup, you can call Python scripts directly from ADS using previously loaded functions. They can be invoked either from Data Display or from Schematic through a MeasEqn component. To execute a Python script and return what the script prints to the command line, use the following ADS equation:

Eqn Rtn=call_python_script(C"\\PythonScripts","3dsc_generate.py")

Since Python scripts are typically used to process and/or plot data generated from an ADS simulation, you will also need to pass ADS data into Python and then receive data back into ADS from Python. This can be done using the following equation:

 

ADS_RtnData=call_python_script_IO(PATH to Directory of Python Script, Python Script Name, Data1, Data2, Data3...,DataN)

 

The above function exports data from ADS into Python, runs the specified Python script (which can access the data), and automatically exports data back to ADS using the Python script—all in one step. Using this function along with a predefined Python script, you can generate a 3D Smith Chart from ADS and plot simulation data on it. The Python scripts used to generate the 3D Smith Chart are provided in the workspace folder ./Smith_3D_wrk/data/Python, provided for registered users. 

 

Similar 3D Smith Chart plots can be generated from other workspaces. All you have to do is adjust the path string in the function "call_python_script_IO()" to point to the location of the Python folder that has the 3D Smith Chart scripts you are calling.

 

The above process is ideal if you want to plot points, lines, simple surfaces, and contours using data generated from ADS simulations. If you’re interested in using Python scripting to generate more advanced plots on the 3D Smith Chart; however, then you’ll want to get a better understanding of the Python functions that enable 3D Smith Chart plotting.

 

Watch this video to see advanced plotting using the ADS Data Python link. Registered users can view the application note, How to Create your own 3D Smith Chart Plots

Advanced Plotting Using the ADS Data Link (Part 2 of 3) - YouTube  

 

You can see that the 3D Smith Chart offers you unique insights that other standard plotting tools simply cannot, and we've only just begun. Find out so much more in this upcoming live webcast: Four Ways to Boost Simulation Data Processing Using Python.

 

Four Ways to Boost Simulation Data Processing Using Python

 

Registered users can view the following resources in the Keysight EEsof EDA Knowledge Center (register here):

 

Apply today for your free 30-day full-version trial of Keysight ADS. 

free trial, ADS, Keysight

 

References

 For more information on the "3D Smith Tube" from the team at Baylor University, see the following IEEE papers:

1. Joseph Barkate ; Matthew Fellows ; Jennifer Barlow ; Charles Baylis ; Robert J. Marks.  "The Power Smith Tube: Joint optimization of power amplifier input power and load impedance for power-added efficiency and adjacent-channel power ratio". IEEE Wamicon, 2015. http://ieeexplore.ieee.org/document/7120398/

2. Matthew Fellows ; Matthew Flachsbart ; Jennifer Barlow ; Joseph Barkate ; Charles Baylis ; Lawrence Cohen ; Robert J. Marks.  "Optimization of power-amplifier load impedance and waveform bandwidth for real-time reconfigurable radar".  IEEE Transactions on Aerospace and Electronic Systems ( Volume: 51, Issue: 3, July 2015 ).  http://ieeexplore.ieee.org/abstract/document/6857780

3. Matthew Fellows, Sarvin Rezayat,Jennifer Barlow, Joseph Barkate, Alexander Tsatsoulas,Charles Baylis,Lawrence Cohen. "The bias smith tube: Simultaneous optimization of bias voltage and load impedance in power amplifier design." Radio and Wireless Symposium (RWS), IEEE. 24-27 Jan. 2016. http://ieeexplore.ieee.org/document/7444408/

4. Charles Baylis; Matthew Fellows; Matthew Flachsbart; Jennifer Barlow; Joseph Barkate; Robert J. Marks.  "Enabling the Internet of Things: Reconfigurable power amplifier techniques using intelligent algorithms and the smith tube".  2014 IEEE Dallas Circuits and Systems Conference (DCAS).  http://ieeexplore.ieee.org/document/6965341/

 

Introduced in a separate post, GoldenGate 2017 enhances circuit reliability in RFIC design by checking against electrical (such as voltage and current) and geometrical rules that exist in the PDK and/or rules set by the user. This feature is referred to as safe operating area, or SOA. When GoldenGate 2017 finds out that one of these rules is not met, it will issue a warning in the log file. The RF designer can also track down the failing device(s) in the schematic with the tool’s highlighting feature for an efficient debugging experience.

In analog and RF circuits it is common, for instance, to have different voltage and FET domains, making it easy to have a higher voltage being allowed at some nodes but that same voltage being destructive at other nodes. Traditionally, the check for overvoltage is done manually, which, of course, is not generally reliable and is tedious. The simulation tool can perform this task much more efficiently.

Here is an example where the drain of the transistor sees a slight overvoltage that is not high enough to damage the transistor right away, making the oversight hard to uncover during chip evaluation. However, ignoring this slight overvoltage will cause reliability issues down the road, the type that gives semiconductor manufacturers nightmares. GoldenGate 2017 eliminates these fears. It checks against PDK rules by reading the asserts in the kit and it also allows the user to set his or her own rules to check against, enhancing overall reliability.

GoldenGate 2017 integrates the SOA functionality in a well-designed fashion, making it efficient for RFIC designers to check against rules. Besides printing assert violations in the simulation log file, GoldenGate’s “Violation Display” GUI makes the management of rule violation a breeze by displaying a summary of rule checks. Further debugging is straightforward and is done by expanding the details in the same window. Highlighting the violating device(s) in the schematic is also possible at this stage with the click of a mouse button.

Furthermore, results from sweep runs can be expanded into a separate display window for convenient study and comparison. The tables dynamically update column entries to include only relevant data and to keep the table size manageable.

Do you work on RFIC design and have not tried GoldenGate yet? Download your free trial and discover how this world-class circuit simulation tool can help optimize your design process and resolve your circuit simulation challenges.

GoldenGate, offered by Keysight EEsof EDA, is the best-in-class RFIC simulation tool inside the Cadence Virtuoso design environment. For many years, RF designers have relied on GoldenGate to solve their challenging problems, and have benefited from its robust simulation convergence and fast simulation capabilities to fully characterize their transceiver designs prior to tape-out.

GoldenGate offers powerful RFIC simulation solutions. Here are some of its characteristics:

  • Best-in-Class RF Circuit Simulation
    • Provides the most advanced steady-state (including harmonic balance, time balance, time shooting, and hybrid) and envelope (hybrid time-/frequency-domain nonlinear) solvers for design and verification of RFICs within the Cadence Virtuoso environment
    • Supports all large- and small-signal RF and transient analyses including large-signal stability and full X-parameter modeling and simulation
  • Advanced Analysis Support
    • Offers a wide variety of capabilities, such as Monte Carlo, Corners, and Fast Mismatch & Yield Contributor, to fully explore, analyze, and optimize designs before tape-out, minimizing the time and expense of re-spins
    • Includes a unique transistor-level PLL jitter and noise analysis option
  • Automation and Usability
    • Accelerates design and verification by providing a number of built-in and easily accessible multi-dimensional sweep, optimization, Monte Carlo, and load-pull tools along with simulation management capabilities
    • Automates EVM, ACPR, gain compression, IP3, and load-pull analyses
  • RF to mm-Wave Design Support
    • Provides access to ADS Data Display with dedicated RF templates and adsLib with over 150 RF distributed-element library components
    • Handles large S-parameter blocks with Multi-Threaded Convolution
  • Wireless Standard-Compliant Design
    • Enables scalable system-level solutions from RF architecture exploration through end-to-end verification with links to SystemVue and Ptolemy
    • Verifies full radio functionality using Keysight's comprehensive library of standard-based wireless verification intellectual property (IP) to accelerate the validation of complex RFICs; wireless libraries for 5G, Bluetooth, LTE, WCDMA, WiMAX, DTV, etc.

 

Keysight EDA has just released GoldenGate 2017, which introduces the following new features:

  • Safe Operating Area (SOA) – With SOA, GoldenGate 2017 enhances circuit reliability by automatically ensuring all devices operate within their safe operating areas – electrical or geometrical rules set by the PDK and/or the user. GoldenGate 2017 produces appropriate warnings, and highlights the failing devices in the schematic, simplifying the debugging process. This feature replaces tedious and unreliable manual checks. SOA is covered in more detail in a separate post.
  • TSMC Model Interface (TMI) – The use of the new and fast TSMC silicon processes – 16nm FinFET or later – which all require TMI support, makes it possible to design mm-wave circuits with silicon. Doing so enables the mass production of transceivers employed by systems adhering to the upcoming communications standards. Now that GoldenGate supports TMI, users can take full advantage of many of GoldenGate’s strengths, such as robust simulation convergence and fast simulation speed, while designing the latest and greatest circuits. It is worth mentioning that GoldenGate’s implementation of TMI also supports the circuit aging feature of TMI.
  • Simulation Speed Improvement – GoldenGate 2017 significantly improves its envelope transient simulation time and further establishes itself in the efficient simulation realm by introducing 4x parallel threading. Relatively long envelope transient simulation runs benefit the most, and that is where speed matters the most. The following table showcases a few sample envelope transient test runs.

 

Test Case

Wall Time prior to GoldenGate 2017

GoldenGate 2017 Wall Time

Wall Time Improvement

White Noise, ET

3.57hrs

1.01hrs

3.5x

Power Amplifier ACPR, ET 3

5.08hrs

1.86hrs

2.7x

Unit NPort Recurs Var Step, ET

2.39hrs

0.86hrs

2.8x

Level 3 ET

1.24hrs

0.42hrs

3.0x

 

  • New and Updated Model Support – GoldenGate 2017 adds support for the following models: BSIM-IMG 102.6.1, 102.7, and 102.8, BSIM-CMG 106.1, 107, 108, and 110, BSIM-CMG Level = 72, BSIMSOI 4.4, CMC Diode, MOSVAR 1.3, Leti-UTSOI 2.20, HiSIM HV 2.10 and 2.3.1, HiSIM 2.9.0, HICUM L0 1.32, and HICUM L2 2.34

 

   GoldenGate is part of Keysight's RFIC solution that also includes Momentum for 3-D planar electromagnetic simulation and Advanced Design System (ADS) for linking the RF system, subsystem, and component-level design and analysis as part of a unique and comprehensive RFIC design flow. GoldenGate 2017 is fully compatible with the following Cadence versions:

  • IC 5.1.0 and all subversions
  • IC 6.1.5, 6.1.6, 6.1.7, and all subversions
  • ICADV 12.1 and 12.2

 

   Do you work on RFIC design and have not tried GoldenGate yet? Download your free trial and discover how this world-class circuit simulation tool can help optimize your design process and resolve your circuit simulation challenges.