SystemVue Hands-On Workshop - Throw Away Your …...• Programming spreadsheets are difficult when...

SystemVue Hands-On Workshop

Throw Away Your Spreadsheets!

Al Lorona Application Engineer Agilent EEsof EDA July 2013

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Lab #1: WhatIF

Lab #2: What is Spectrasys? We will emphasize all of its advantages over a spreadsheet. How does it integrate with other tools? I will demo export to ADS. There we can perform HB or CE simulation. Replace any block with a circuit.

Model-based simulation.

Lab #3: Data Flow simulation. Using RF Link, apply a modulated signal to our Spectrasys circuit.

Welcome & Agenda

Copyright © 2013 Agilent Technologies 2

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We are going to create an RF system in Spectrasys. As a related exercise, we’ll show how to bring that system into ADS for further simulation. This allows you to have the ‘best of both worlds’: the tremendous system and synthesis capability of Spectrasys and the high-end circuit simulation of ADS. The example used in this tutorial is that of a dual band WiFi receiver, but the frequency range and modulation are unimportant to someone learning Spectrasys for the first time. These techniques are applicable to any topology. Learn them, and you’ll be able to simulate any RF system properly. There is a hands-on lab with three parts: Part I is using WhatIF, and Part II is using Spectrasys. Part III goes further by applying a modulated signal to a Spectrasys design. So, we will focus on technique more than on a specific schematic diagram.

Introduction


RF Architecture Defined…

Engineers determine how many, what type, which parameters, and the order of stages required to meet system specifications:

CouplerIL=2 dBCPL=20 dBDIR=30 dBZ0=50 ohm

1

3

2

? or


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Because it can cause:

• Poor performance

• Many design turns

• Higher Cost

• Longer time to market

Architecture is Critical


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• Linear Analysis

• Spreadsheets

• Other Tools

Traditional RF Architecture Analysis


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Many people use only linear simulators. They ignore the nonlinear effects of the system. Furthermore they are not iterative.

Linear Analysis


Advantages Disadvantages Very fast, real-time tuning No nonlinear effects or frequency

conversion

Effective optimization because of simulation speed

Works on circuits – not systems

Effective statistical analysis Slow speed for systems

Fast analysis using behavioral models Slow for device-based system analysis

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Analytical equations are programmed for each path of interest - typically scalar, unilateral, and unfiltered.

.

Spreadsheets, Cascade and Line-up Tools


Advantages Disadvantages Readily available Poor integration with other tools

Simple data entry Typically scalar calculations

Cheap All paths must be anticipated and programmed…and what if the lineup changes? Typically assumes unfiltered and flat frequency response Typically no mismatch effects, leakage paths or reverse paths Difficult to hand off & maintain

Spreadsheets – Difficult, Inaccurate, and very Limited

Copyright © 2013 Agilent Technologies

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Traditional Method Limitations

• CIRCUIT simulators are designed for components, not system realization.

• Programming spreadsheets are difficult when image noise, intermod filtering, mismatch effects and multiple paths are considered.

• Conclusion: no traditional tools are good for analyzing RF system architectures.


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What is Required for RF Architecture Analysis?

This led to…

• Spur identification and resolution • Identifying root causes is critical in systems with hundreds of leakage,

harmonic and intermod tones.

• Phase noise

• Noise analysis that considers the channel bandwidth

• In-channel and out-of-channel intermodulation analysis

• Accuracy: mismatch, phase, images, measured vs. ideal models, etc.

• Integration with other software tools and measurement instruments


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• SPARCA: method developed in 2002

• Based in the spectral domain

• Bilateral signal flow of all paths; all paths are considered

• Vector (magnitude and phase) modeling

• Channel concepts integrated into the method

• Works with SystemVue, ADS, and GoldenGate

Spectrasys


How Spectrasys Works

Signal generation and propagation:

• All signals, harmonics, intermods, and noise propagate from every node to every other node, in every direction

• Non-linear simulation, including phase Measurements:

• Signals and noise are each integrated across the channel BW

• Spectrums at each node Impairments:

• True filtered and non-flat transfer function is modeled • Mismatch, leakages, and reverse paths are modeled

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Spectrasys is Part of SystemVue. What is SystemVue?

SystemVue 2013.01

WhatIF Spectrasys

DataFlow

SystemVue is made up of several products. WhatIF and Spectrasys are the two of most interest to us here. WhatIF is a tool for analyzing spur-free zones. It lets you select a suitable IF frequency for a system. It is extremely fast and easy. Spectrasys is the RF System simulator. It’s extremely powerful. More about it later. Dataflow is the ‘mixed signal’ system simulator. It combines DSP and RF.


Spectrum Plot

Noise floor from another component

Info box

Wideband signal

Noise floor

Wideband signals underneath the noise floor

The first type of Spectrasys plot is a spectrum plot. Signals, harmonics, intermods, and noise. The info box shows details on the large 175 MHz tone (displayed when the mouse hovers over that signal), including frequency, power, node name, and the path taken by the signal to appear at the output. This is where Spectrasys earns its “root cause analysis” name, because you can see the exact path taken by every signal.

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Detail of Readout P5: 2107.5 MHz, -38.954 dBm

Node Total from 'RX1'

P5: 2107.5 MHz, -38.982 dBm{3}[RXLO1],RXLO1\IS1,RX1\Mixer_1,RX1\LPF_Butter_1,RX1\RXIFAmp,RX1\RXAttn

The readout in detail: P5 – means ‘power spectrum at node 5’ {3} – is the ‘coherency number’ used to determine which spectra should add coherently. [RXLO1] – is the frequency equation showing how the signal was generated. RXLO1,Mixer_1,LPF_Butter_1, etc. - is the path taken by this signal to arrive at the output… where the signal came from.

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But we are getting ahead of ourselves!

Let’s back up and see exactly what it takes to set up a Spectrasys simulation.

We will look at a recommended procedure, use SystemVue multicarrier sources, incorporate COTS parts and built-in behavioral models, then interpret the results with plots and tables. Our first example will be a dual-band 2.4 & 5.3 GHz receiver

Hold on


With Spectrasys, you do the following in this order: Lay out the schematic. Set up the controller. Simulate. Add plots and tables to look at the results. Let’s take these one at a time…

Proceed like this

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Block diagram In Part II of the lab, the receiver block diagram is created and then simulated with Spectrasys. You will look at spectral power plots as well as path-related (or “budget”) measurements like cascaded gain, channel power, cascaded noise figure, carrier-to-noise ratio, and many others.

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To place the various parts on the schematic, click on View -> Part Selector. This makes the Part Selector visible. Then, from the RF Design library, select and place the desired parts.

Schematic

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RF Design Kit

All parts on the schematic came from the RF Design library in SystemVue. Over 130 different parts are available. They are all behavioral models. Multiport S- and X-parameter files are also included. A number of vendor models are also available on the web. Even if the exact part you need is not here, you can still create your own model from built-in parts and/or measured data.

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Workspace Tree

To see the ‘big picture’ of any workspace, look at the Workspace Tree. The tree shows everything relating to this workspace. There is one schematic, one Spectrasys simulator called “System1”, an Equation page, several Datasets containing simulation results, and various plots such as “System1_PWR_at_Node_6” and “…Path1_CP”.

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Add item

‘New Item’ lets you add all of this!

New Item button

Anything you might need to add to the workspace can be found under the New Item button. This is

a very good button to know about!

This is how the

Spectrasys simulator, the schematics, the notes,

etc., are added

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Now it’s time to set up the simulation. Place a Spectrasys (a.k.a. System) simulator into the workspace and open it up. You will see the screen below. All sources on the schematic automatically populate the Schematic Source Summary. The important parameters that are the user’s responsibility are Dataset, Bandwidth, and Paths (next slide). The Dataset is the name of the simulation result. The Measurement Bandwidth is used in noise power and channel power computations.

Set up the simulation

<<Click-click!>>


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We mentioned a ‘path’ earlier.

Level diagrams require that we define at least one path along which to make the measurement.

Let’s see how a path is defined.

Path

25 Copyright © 2013 Agilent Technologies

Defining a Path On the Paths tab of this RF System analysis, “PathRX1” starts at the part called “RXSource” and ends on the Part called “RX1Out”. Simply by doing this, Spectrasys knows to use the shortest path between these components to generate the level diagrams. Any number of paths may be enabled, and for any path you can start anywhere in the circuit and end anywhere else!


Start Anywhere… End Anywhere

(Beginning Node - 1) RF-to-IF Path (End Node - 3)

LO-to-RF Path

(Beginning Node - 2) LO-to-IF Path (End Node - 3)

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Channel Definition

Freq center

BW

Adjacent Channel Upper #1

Adjacent Channel Lower #1

Main Channel

The other necessary concept is that of a channel. To make a measurement, you must define a channel bandwidth This is important because calculations of signal and noise power are performed in that bandwidth, which is exactly how a receiver would experience total power in a bandwidth.

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Measurement Bandwidth

The channel is defined on the General tab of System simulator. Simply set it to the desired value and re-simulate. Total node power will now be integrated across the new bandwidth.

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Lab #2 - Spectrasys

2445 MHz

20 MHz

2405 MHz

10 MHz

100 MHz

50 MHz

5225 MHz 5325 MHz

Frequency Band 2.4 & 5.4 GHz Bandwidth 10 MHz & 50MHz

Spurious Signals Less than -40 dBc

Noise Figure Less than 4 db

Sensitivity -60dBm for 0 mw output

We’ll now take the information provided by WhatIF (Appendix A) to help design a dual-band WiFi receiver. The specs for the receiver are shown in the table. The figures below right show the required spectrum input to the receiver (to accurately feed the full multicarrier signals into our receiver to see its real-world response.)

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R IL

IFTableData=(2x5) [109,2.5,3.5,32.5,42.…RFTableLOPwr=13dBmRFTableInPwr=-10dBm

RFTableData=(5x5) [109,0,15,23,36; 10,0…IPSAT=12dBmIP1dB=7dBmLO=13dBm

ConvGain=-6.500000000dBPart=HMC218MS8

Part0_2 {MIXER_TBL}

Mixer

The mixer is the same one used in our WhatIF analysis. It is a COTS part from the Hittite library.


Spectrum Detail – as seen previously

Noise floor from another component

Info box

Wideband signal

Noise floor

Wideband signals underneath the noise floor

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It is important to note that this simulation uses CW signals. We haven’t applied modulation yet.

Some of the signals appear to have a bandwidth or shape… this is a convenience that Spectrasys provides.

Now let’s go on to examine level diagrams.

A Reminder


Level Diagrams Are Like Chain or Budget Analysis

Channel Power (CP) is one of dozens of measurements that are automatically calculated. You simply choose which ones to plot after simulating. Or, if the measurement you want doesn’t exist, you can write it yourself using equations. Markers at the input and output of the duplexer show that it has a loss of about 1 dB. Plotting GAIN could have also determined this.


Level Diagrams – Compression Example

The components along a path are shown on the x-axis, and the quantities plotted on the y-axis. Here, we see Channel Power (CP) in red, and Compression (COMP) in blue. The LNA is starting to go into compression.


Change LNA Parameters

Double-click on the LNA

symbol on the schematic to

change any of its

parameters.

Re-run the simulation to

see the results of the

changes.


Possible measurements

… and more

A very few of the many possible

measurements that can be plotted in a

level diagram.


Tables

It’s also possible to put any desired

data into a table, such as this path measurement of Cascaded Noise

Figure (CNF).


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Please begin Lab #2 now!

Start by opening the workspace, “Dualband_Wifi” and look at the Design, “Sch1”.

You will add the 5.3 GHz band front-end parts then simulate.

You will look at the output spectrum and also at the power and noise figure budgets.

Lab #2 - Spectrasys


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Keep the following in mind as we proceed.

1. Spectrasys should be used whenever and wherever you used to use a spreadsheet, because it will do everything a spreadsheet does and much more.

2. Once the system cascaded parameters are worked out in Spectrasys the workspace can be exported to ADS. At that point you can switch over to thinking in terms of “circuits”. The RF Architect product launches Spectrasys from inside of ADS. 3. Spectrasys can be ‘dumbed down’ to make its results match that of a spreadsheet, but when allowed to operate normally will tell you much more than a spreadsheet can. A good example of this is in calculating IP3 in a system with filters… Spectrasys will give an answer which is exactly what you would measure in the lab, including the effect of filter skirts. 3. Remember that all mismatch, leakage, and nonlinear effects are simulated in Spectrasys. At every node. In every direction. To every other node in the circuit. Using real, measured data if desired.

A Few More Points


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4. All of the components in the “RF Design” library are for Spectrasys only. They should never be used in any other simulation. 5. Spectrasys isn’t like Harmonic Balance. HB is a circuit simulator that looks only at certain specific frequencies. Spectrasys is a system simulator that looks at all frequencies at all times. A continuous-frequency technique. 6. The MultiSource part in Spectrasys has a number of modes. They are: CW Noise Multicarrier Continuous frequency Wideband RX intermod 7. Finally, Spectrasys answers mysteries such as:

a. How can the channel noise power be below thermal noise? b. How come my noise figure decreases through a cascade? c. Why is there no attenuation across a filter?

A Few More Points (continued)


Link to ADS File -> Export -> Export Schematics to

ADS…

DEMO


Link to ADS

The schematic as it comes into ADS. Missing components = no ADS equiv.


ADS Results

2 4 6 80 10

-250

-200

-150

-100

-50

-300

0

freq, GHz

dBm(

Vout

)Output Spectrum


Rule

One of the philosophies of SystemVue is that

“Everything is Interchangeable.”

That goes for sources, sinks, and models.


Sources Captured by VSA

Built-in LTE source

Stored in file

A signal can come from a built-in source, a text file, from a waveform captured by test

equipment, or a waveform created in another application.


A Variety of Sinks

Any signal can be measured by a built-in sink, stored in a file, or

routed to test equipment.


Several types of models are always available for simulation: 1. Built-in behavioral. 2. X-parameters. 3. S-parameters. 4. Result of another sim. 5. MATLAB model. 6. An actual circuit,

whether in ADS, Genesys, or GoldenGate.

Models


Simulation Results

Simulation results are exactly the same with the X-parameter model


Simple, behavioral models

Add realism: vendor parts, measured data, noise floor, other impairments

More realism: EM effects, measured data, real-world modulated signals, custom models

What is Our Goal?

To work toward ultimate accuracy by adding realism to the simulation


What a DataFlow Schematic Looks Like

Thus far, we have stayed in the analog/RF domain. SystemVue also handles simulations in the digital domain. Digital modulation. Uses the DataFlow simulator. We can apply these signals to our system. We’re no longer limited to pure tones and can see the effects of our RF nonlinearities on real signals. Black arrows: Envelope mode.


The “Other” Simulator - DataFlow

When SystemVue is in Envelope mode, signals have a characterization (carrier) frequency and a bandwidth, and the System Sample Rate sets the analysis bandwidth.


SampleRate sets Bandwidth The Sample Rate of 640 MHz gives a total analysis bandwidth of 640 MHz. We can only see what’s inside of this bandwidth, so it’s important to ‘get it right’.


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Let’s do Lab #3 now.

It’s a DataFlow simulation with LTE and WLAN signals. A new part called “RF Link” encloses a Spectrasys schematic so it can be used in this type of simulation. Nonlinear effects include: gain compression, frequency response, noise and frequency conversion (if any).

Enjoy!

Lab #3


Intermodulation Concepts

Simplistic cascaded intermod equations (spreadsheets) are NOT used by Spectrasys ADVANTAGES: Using Spectrasys…

• Mismatch effects, filtering, isolation are all considered • Arbitrary signal formats are supported (as seen in Lab #2) • Consequently, intermod measurements (especially IP2 and

IP3) are accurate for non-ideal systems


Measurements: Intermodulation & Compression Time does not permit looking at the intermod measurements available in Spectrasys, but be aware that all of the following are possible: • Cascaded Gain (3rd IM)

• Channel Frequency (Tone)

• Channel Power (Desired 3rd IM)

• Channel Power (Tone)

• Gain (3rd IM)

• Gain (All Signals)

• Percent 3rd IM

• Stage Output 1 dB Compression • Stage Output 2nd IM • Stage Output 3rd IM • Stage Output Saturation Power • 3rd Order Intercept (Input) • 3rd Order Intercept (Output) • 3rd IM Power (Propagated) • 3rd IM Power (Generated) • 3rd IM Power (Total)


Source Setup

The Intermod Source Wizard (open a MultiSource to see this button) makes visualizing and setting up the 2 tones very easy.

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Example: Intermodulation & Compression DBM

[GIM3P], DB[SDR]

-200

-160

-120

-80

-40

0

40

80

120

160

200

DBM

[IIP3]

, PRI

M3

-30

-24

-18

-12

-6

0

6

12

18

24

30

Node

1 5 6 16 9 10 17 7 8 4

Intermodulation & Compression

R IL

R IL

DBM[IIP3]DBM[GIM3P]DB[SDR]PRIM3


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We hope that this workshop was a good use of your time.

Throw away your spreadsheets!!

For Additional Information: SystemVue: http://www.agilent.com/find/eesof-systemvue-info Try SystemVue: http://www.agilent.com/find/eesof-systemvue-evaluation ESL Design Notebook Blog: http://esl-design-notebook.tm.agilent.com/

Thank you for attending


http://www.agilent.com/find/eesof-systemvue-info

http://www.agilent.com/find/eesof-systemvue-evaluation

http://esl-design-notebook.tm.agilent.com/






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The intended use model is this: use WhatIF first to choose an IF range, then move on to Spectrasys for the actual implementation and simulation.

If you’d like, you can start Part I of the lab now, which is an introduction to WhatIF. This lab will take you about 20 minutes to complete.

In case you do not wish to perform Part I right now, the following slides will show you the highlights of that lab

Appendix A Lab #1: WhatIF


Frequency planning WHATIF is an tool for IF and LO

frequency planning and spurious response prediction.

“Design-on-the-fly” is possible

because WHATIF is extremely fast. The plot of spur-free zones to the left takes less than a second!

Tradeoffs and changes to mixer

models can be realized instantly. Throw away your complicated graphical techniques or specialty spreadsheets.

You can select either a robust

mixer behavioral model or a measurement-generated mixer spur table.

In summary then, WHATIF is an

essential tool providing the basic IF and LO frequency plan prior to moving into the SPECTRASYS architecture and design role.

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Receiver example

This is the dual-band receiver used in Lab 1. The two WhatIF screenshots above show the setup for the two parallel mixers used in the receiver. Mixer 1 (low band) is on the left, and Mixer 2 (high band) on the right. These data are entered into WhatIF when you run the tool in the lab.

RX Specs Frequency Band 2.4 & 5.4 GHz

Bandwidth 10 MHz & 50MHz

Spurious Signals Less than -40 dBc

Noise Figure Less than 4 db

Sensitivity -60dBm for 0 mw output


Mixer type

One more necessary step is to choose the mixer type. Here a Hittite double balanced mixer with measured spur levels is selected from a vendor library that is shipped with Genesys. All that is left to do is to click on the Apply button, and instantly…


Spectrum …the spectrum appears, resulting from using the commercial, off-the-shelf mixer component. Wherever there is a green bar, that is a spur-free zone. Spurs from Mixer 1 are in blue, and from Mixer 2 are in red. The plot shows that, for the settings chosen, there is only one spurious-free 100 dB IF band. Hover your mouse over any spurious product and you are told the mixer product, spur level, and frequency band. If you hover over the green band, a box appears telling you that the band is 672 – 705 MHz… that’s 33 MHz wide. Not wide enough for the required 50 MHz bandwidth of the receiver. We’ll have to address this. This plot is achieved by using the mixer table data only. Later, using Spectrasys, we can find out more exact levels by running an actual nonlinear simulation.

Mixer #1 products

Mixer #2 products

Spurious free range


Experiment with different settings

It is very useful to be able to change the amplitude range, Low Side/High Side injection, or input drive level, and then re-plot. Here, the required spurious-free range has been relaxed to 80 dB, and Mixer 1 was changed to Hi Side injection. It’s a great aid to be able to do this. You can try a number of different parameters, loosen tolerances, etc., and instantly see the effect on the frequency plot. Other tools can’t do this! Let’s see if any of these changes helped find a wider spur-free zone for our IF…


Much Better

The plot now shows a lower and wider IF frequency band to choose from (212.5 to 875 MHz). In the lab, 220 - 270 MHz was selected for the IF. Now that the IF band is chosen, the required LO frequencies are easy to calculate. This is the end of Part I of the lab. Now we continue with a discussion of what Spectrasys is and what it can do.


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New Spectrasys features 1. High Carrier Count (HCCI) – August 2013 2. Zero IF support, for direct baseband outputs 3. Multi-port RFLINK, for MIMO and IQ architectures 4. Phase Noise Co-Simulation

Appendix B: What’s New in Spectrasys?


Background: What is the Output Spectrum when you have 10 to 200 Input Carriers?

This has been always been a Challenge in the Simulation Industry!


Solution: Only Need the Envelop not Individual Intermods

Output

Frequency

Am

plitu

de


Synthesized Envelops: All 2nd and 3rd and Order Intermod Groups

25 Carriers

1,1,-1

2,-1

1,-1

1,-1 DC

1,1 2

1,1,1

2,1

3


Simulation Time Speedup (x1500 for 100 Carriers) (Single non-linearity)

Intel Core i3 CPU, 3.0 GHz, 8 GB RAM, x64

HCCI


Spectrasys Zero IF Receiver Model


Zero IF Receiver Model

1. Load Zero IF Receiver 2.wsv


Presenter

Presentation Notes

Zero IF Receiver Workspace Agilent Technologies SystemVue Workspace ABSTRACT This example illustrates a zero IF architecture implemented in the RF simulator and the modulation and demodulation are implemented in data flow and using the VSA 89600-A software. �SETUP A QPSK modulator and demodulator have been created in their own schematics. The RF ZIF receiver has also been created in its own schematic. All three of these pieces have been brought together in the co-simulation design.

Zero IF Receiver Model The RF Link

1. Observe the RF_Link

ZIF Receiver

Component


Zero IF Receiver Model RF Link

1. Run the DF simulation:

2. Record your EVM:_____%

3. Without stopping the simulation, change the GainImbal value in the Tune Window to 2. What happens and Why?


Presenter

Presentation Notes

Important Note: Changing values in the RF-Link component will not effect the simulation because it is characterized at the time the simulation is started.

Phase Noise Tuning

1. Checkpoint the Noise Plot 2. Slide the PK10K Tuner to -70 dBc

3. When done remove the Checkpoints:


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