circuit design training manual: low noise amplifier part ii low noise...l hfss l hfss-ie l...

Circuit Design Training Manual: Low NoiseAmplifier Part II

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Circuit Design TrainingManual: Low Noise Amplifier Part II

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Table of ContentsTable of Contents Contents-1

1 - Introduction 1-1

Prerequisite 1-1

ANSYS Electronics Desktop 1-1

2 - DC Analysis 2-1

Set up DC Analysis 2-2

Run DC Analysis & Plot DC-IV Curve 2-5

3 - LNA with Non-Linear Model 3-1

View DC Bias 3-1

Run Linear Analysis 3-3

Create Report 3-4

RF 1 Tone Nonlinear Analysis 3-6

Define RF 1 Tone Analysis 3-11

Define a Power Sweep and Analyze 3-12

Create Results: Pout/TG21 vs. Pin 3-14

Create Results: Spectrum 3-16

Create Results: Wave Form 3-17

Add a Second RF Source to Input port 3-18

Add Intermodulation Analysis Setup and Analyze 3-22

Create Results: Pout vs Pin 3-23

Create Results: Calculate IP3 3-24

Create Results: Intermodulation Spectrum 3-25

Harmonic Balance: Setup andOptions 3-25


Contents-1



Contents-2




1 - IntroductionThis document covers the following topics:

l Circuit Simulationl Schematic Capturel DC Analysisl Linear (S-parameter) Analysisl Nonlinear Analysisl Single Tonel Compressionl Multi Tonel Intermodulation

PrerequisiteTo perform the training exercise, you need the relevant designs and the corresponding footprints

available at the following location:Examples>Circuit>Low Noise Amplifier.

ANSYS Electronics DesktopThe ANSYS Electronics Desktop, illustrated in the following figure, provides a comprehensiveenvironment for designing and simulating various electronic components and devices.


Introduction 1-1




Figure 1-1 ANSYS Electronics Desktop

The desktop supportsmany design types listed below:

l HFSSl HFSS-IEl EMDesign (HFSS 3D Layout or Planar EM)l Circuit Designl Circuit Netlistl Filter Designl Q3D Extractorl 2D Extractor

Introduction 1-2




All design types appear as icons on the toolbar or under theProjectmenu. The relevant designtype for simulating LNA using an s-parameter model of NEC NE68133 BJT, isCircuitDesignwhich is illustrated in the following figure.

Figure 1-2 Project menu

Introduction 1-3



PDF layout 1-4




2 - DC AnalysisThis section shows how to set up the LNA schematic and define a DC analysis before running thesimulation. Set up the schematic as follows:

1. Go to File > Open Examples > Circuit > Low Noise AmplifierExamples and select LNA_DC_IV_Start.aedt.

2. Save the file in a different location other than the Examples folder.

The LNA schematic of the inserted design has the following circuit shown in the following figure.The circuit uses a non linear model for the transistor (using a spice lib file instead of the Sparameter data file.

Figure 2-1 Circuit


DC Analysis 2-1




Set up DC Analysis1. Right-clickAnalysis and selectAdd Nexxim Solution Setup > DC Analysis from the

short-cut menu.

Figure 2-2 Analysis options

TheDC Analysiswindow appears.

DC Analysis 2-2




Figure 2-3 DC Analysis

2. ClickAdd on theDC Analysiswindow.3. On the dialog box, select variable VB and define a Linear step sweep 0.75 to 0.85 with step

0.01 and clickOK.

DC Analysis 2-3




Figure 2-4 Add/Edit Sweep window

4. SelectVC and define two Linear step sweeps: 0 to 0.5 step 0.01 clickAdd; then 0.5 to 5step 0.5, clickAdd, and then clickOK.

DC Analysis 2-4




Figure 2-5 Add/Edit Sweep window

5. On theAdd/Edit Sweepwindow, clickOK to accept the settings.

Run DC Analysis & Plot DC-IV Curve1. Right-clickDC Analysis on theProject Manager window and select Analyze.2. Right-clickResults and select CreateStandard Report/Rectangular Plot.3. SelectVC from the Primary Sweep,Current under Category and Inegative(Ic) under

Quantity as shown in the following figure.

DC Analysis 2-5




Figure 2-6 Report

4. On the Families tab, click the ellipsis under Edit and selectAll value for VB.

Figure 2-7 Families tab

5. ClickNew Report andClose.

DCIV Curves are generated as shown in the following figure.

DC Analysis 2-6




Figure 2-8 DC-IV curve

Note: If you just want the value for current probes, checkDC Display options as shown below.

DC Analysis 2-7




Figure 2-9 DC Display options

DC Analysis 2-8



3 - LNA with Non-Linear ModelNon linear model for the transistor (using a spice lib file) is used in the circuit of the project LNA_RF_1_Tone_Start instead of the S parameter data file.

Select the project LNA_RF_1_Tone_Start.aedt from the Low Noise Amplifier folder underExamples> Circuits.

Figure 3-1 circuit

View DC BiasThe steps to view DC bias are as follows:

1. Right-clickLNA_Matched_NL on theProject Manager and selectView DC BiasValues>Show DC Bias or the icon on toolbar.


LNAwith Non-Linear Model 3-1




Figure 3-2 View DC Bias Values

DC current and voltage at each node are displayed in the schematic as shown in the followingfigure.





Figure 3-3 DC Bias

2. Check the bias of the transistor, with 2.5V, 3mA which was the bias point of the Sparameters used for matching.

3. Save the project.

Run Linear Analysis1. Right-clickAnalysis and selectAdd Nexxim Solution Setup >Linear Network Analysis

from the short-cut menu.2. Click Add and define a Linear Step sweep from 0.5 GHz to 2GHz in steps of 0.01GHz.





Figure 3-4 Linear Network Analysis, Frequency Domain

3. SelectEnable Noise Calculation and clickOK.4. On the Project Manager window, right-click the option LinearFrequency under Analysis

and select Analyze from the short-cut menu to start simulation.

Create Report1. Right-clickResults and selectCreate Standard Report > Rectangular Plot: dBS21,

dBS11, dBS22, and NF in dB.





Figure 3-5 S Parameter settings

2. After selecting the options shown in Figure 15, clickNew Report to create the S-parameterplot.

3. Select Noise figure as shown in the following figure and clickAdd Trace andClose.4. Rename the report to S Parameters & NF.

Figure 3-6 NF settings





Using the non linear model, it is possible to run a linear analysis.

The non linear model is linearized at the bias condition and the simulation computes thecorresponding small signal S parameters. This allows the user to check that the results using thenon linear model are close to those obtained with the S parameter data file

Figure 3-7 S parameters and noise floor vs frequency

RF 1 Tone Nonlinear Analysis1. Double-click the input port symbol to open thePort Definitionwindow.





Figure 3-8 Port Definition dialog box

2. ClickEdit Sources to open theConfigure Portsand Sources dialog box.3. Ensure that Input is selected under Ports List andPower andSinusoidal are selected

underAdd New Source.





Figure 3-9 Configure ports and sources

4. Press the “Add to selected port” button and edit Name to RF_IN5. Select Property POWER and enter Pin (local variable, -10dBm) as the value of property

POWER.l In theAdd Variable dialog type -10dbm in theValue field and press Enter.6. Select Property FREQand enter F_IN (local variable, 0.9GHz) as the value of property

FREQ.l In theAdd Variable dialog type 0.9GHz in theValue field and press Enter.





Figure 3-10 Properties dialog box

7. Select Property TONE and enter F_IN as the value of Property TONE and clickOK.





Figure 3-11 Select Analysis dialog box

8. Review the Configure and Port dialog box to ensure that the final settings resemble thoseshown in the figure below.





Figure 3-12 Configure ports and sources dialog box settings

9. ClickOK.

Define RF 1 Tone AnalysisTheSelect Analysis dialog allows the user to match specific Sources (e.g. Power Sources,Voltage Sources etc.) with specific Analysis setups. This offers the flexibility to havemultipleSources andmultipleAnalysis setups and thenmatch them accordingly. For now we only haveone Source and one Analysis setup so we can simply clickOK to continue.





In theProject Manager window expand theExcitations option to verify that the sourceRF_IN isadded. Notice that the schematic symbol for the input port has a different appearance indicatingthat a source is present.

Figure 3-13 Source in the schematic

Define a Power Sweep and Analyze1. Right-clickAnalysis and selectAdd Nexxim Solution Setup > Harmonic Balance (1-

Tone) from the short-cut menu.





Figure 3-14 Harmonic Balance (1-Tone)

TheHarmonic Balance Analysis dialog box appears.





Figure 3-15 Harmonic Balance Analysis

2. Enter the following settings:l Name = Psweep.l Max. Harmonic Number = 7.l F1 value = F_IN.3. In theSweep Variables panel, clickAdd and selectPin from theVariable drop-downmenu

and set Linear Step from -40 dBm to 10 dBm in steps of 1 dBm.

Figure 3-16 Frequency Sweep

4. ClickAdd and accept the settings by clickingOK.5. Right-click Psweep under Analysis setup and select Analyze to start simulation.

Create Results: Pout/TG21 vs. Pin1. Right-clickResults and select Create Standard Report > Rectangular Plot from the

short-cut menu.2. SelectPsweep in the Solution field andSweep in the Domain field.3. Select Power,P(Output)<F1>, dBm to plot the output power at Port 2 for the fundamental

F1 and click New Report.





Figure 3-17 Reports

4. Select Transducer Gain, TG(Output, Input)<F1,F1>), dB to plot the transducer gainbetween fundamental at port1 and fundamental at port2.

5. ClickAdd Trace and close the dialog box.6. In Project Manager window click Pout trace and in the Properties window set Y axis to Y2.





Create Results: Spectrum1. Right+Click Results and select Create Standard Report/Rectangular Plot.2. SelectPSweep in Solution field andSpectral in the Domain field.3. Select Power P(Output) in dBmand from the Families tab set variable Pin to -15dBm.4. Click New Report and Close.5. Rename the plot toPout Spectrum.





Create Results: Wave Form1. Right-clickResults and selectCreate Standard Report/Rectangular Plot.2. SelectPSweep from the Solution drop-downmenu and Time in Domain field.3. Select Category:Voltage, Quantity:V(Output), Function: none4. In the Families tab, for variable Pin, clickEdit and select Pin = -40, -30, -20, -10 dBm for the

Pin values. Click to close the dialog box.5. ClickNew Report andClose.





Add a Second RF Source to Input port1. Double click the input port symbol to open thePort Definitionwindow.

Notice that theRF_IN power source is already present in the Source List panel as shown inthe following figure.

2. Click theEdit Sources button to open theConfigure Ports andSources dialog.





Figure 3-18 Configure Ports and Sources dialog

3. Check that the “Input” port is selected under “Name” in the upper left area of the dialog andin the “Add New Source” areamake sure “Power” and “Sinusoidal” are selected.

4. Press the “Add to selected port” button and edit Name to RF_IN2.5. Select Property POWER and enter Pin (recall that we already created the Pin variable

earlier).6. Select Property FREQand enter F_IN2 (local variable, 901MHz) as the value of property

FREQ.7. In the Add Variable dialog type 901MHz in the Value field and press Enter.8. Select Propertry TONE and enter F_IN2 as the value of property TONE.9. ClickOK to bring up the Select Analysis dialog box.





The Select Analysis dialog allows you tomatch specific Sources (e.g. Power Sources,Voltage Sources etc.) with specific Analysis Setups. This gives you the flexibility to havemultiple Sources andmultiple Analysis Setups and thenmatch them accordingly.





The Configure ports and sources dialog should look as shown below.

Notice that the schematic symbol for the input port now has a different appearance indicatingthat 2 Sources are present.





Add Intermodulation Analysis Setup and Analyze1. Right click Analysis and select Add Nexxim Solution Setup > Harmonic Balance (N-

Tone).2. Enter the following settings:l Set Name as InterModl Click Edit Tones/Maxk and set No. of Tones to 2l Set F1 to F_IN and F2 to F_IN2, MaxK=5 for both.l ClickOK.3. ClickAdd in the Sweep Variables area and set Linear Step from -40 dBm to 0 dBm in steps

of 1dBm for the variable Pin.4. Click Add and then clickOK.





5. Right-click InterMod from under Analysis and select Analyze to start the simulation.

Create Results: Pout vs Pin1. Right click Results and select Create Standard Report/Rectangular Plot.2. Select InterMod in Solution field andSweep in Domain field.3. Click Edit under Harmonics and include F1 and -F1+2F2 asDefinedOutputs.4. SelectPower, P(Output)<F1>, dBm and clickNew Report to plot the output power at

Output port for the fundamental.5. SelectPower, P(Output)<-F1+2F2> , dBm, click Add Trace to plot the output power at

Output port for the IM3.6. Click Close.7. Rename the plot toPout vs pin InterMod.

See the difference in slopes between the fundamental and third order products. As expected, thethird order term has a slope that is 3 times unity in linear region.





Create Results: Calculate IP31. Right click Results and select Create Standard Report/Data Table.2. Select InterMod in Solution field and Sweep in domain field.3. Click onOutput Variables button to open theOutput Variables window.4. Enter in the expression field :

dBm(P(Output)<F1>)+(dBm(P(Output)<F1>)-dBm(P(Output)<-F1+2F2>))/2

5. Enter in field Name: IP3, and click Add and Done.6. Select Output Variable in Category, IP3 in QuantityNone as Function, and in Primary

Sweep select Pin value =-34dBm.7. ClickNew Report and Close.





Create Results: Intermodulation Spectrum1. Right clickResults and selectCreate Standard Report/Rectangular Plot and InterMod

inSolution field andSpectral in Domain field.2. On the Families tab, click Edit, select Pin =-4 dBm, and on the Traces tab, select Power,P

(Output), dBm.3. ClickNew Report, and clickClose.4. Rename the plot to Intermodulation Spectrum.

Harmonic Balance: Setup and OptionsHarmonic Balance Analysis can be controlled using the options shown:

l MaxHarmonic Number: Max harmonics computed in the solution (MAXK)l F1 value is the single tone frequency, we are using a variable F_IN in this example.

TheMethod parameter selects between the standard harmonic balance calculation and a shootingmethod that facilitates single-tone analysis of circuits with strongly nonlinear behavior.

l Method=HB, standard harmonic balance, is the default for single-tone analysis and isalways used for multi-tone harmonic balance analysis.





l Method=Shooting is available for single-tone analyses only. Whenmethod is set toshooting, single-tone harmonic balance uses a time-domain shootingmethod that isefficient for nonlinear circuits. This option is ignored for multi-tone harmonic balance.

Transient Initial Time set to a positive non-zero value is representing time required for Transient tostabilize before HB begins using the result.

With Auto_Refine_Solution=yes, Nexxim examines the result at each sweep iteration to determineif the solution is sufficiently resolved. If it is not, Nexxim doubles the number of harmonics andrepeats the iteration. Thus, you can start the sweep with MAXK set to a low number, and haveNexxim automatically adjust MAXK as needed tomaintain accuracy.




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