rfplot

Plot cumulative RF budget result vs. cascade input frequency and amplifier power characteristics

Syntax

rfplot(rfobj)

rfplot(rfobj,rfpara)

rfplot(rfobj,m,n)

rfplot(amp,freq)

rfplot(ax,___)

Description

Use the rfplot function to plot:

• Cumulative RF budget result vs. cascade input frequency

• Magnitude response of the S-parameters

• Amplifier power characteristics (since R2023a)

• One-tone and two-tone analysis (since R2023b)

rfplot(rfobj) plots the magnitude response of S-Parameters, S₂₁ for the cascaded budget object, rfobj.

rfplot(rfobj,rfpara) plots the RF budget result specified by RF parameters rfpara versus a range of input frequencies. The input frequencies are applied to the cascade of elements in the RF budget object, rfobj.

Cumulative (that is, terminated subcascade) results are automatically computed to show the variation of the RF budget result through the entire design.

rfplot(rfobj,m,n) plots the magnitude response of S-Parameters, S_mn (S₁₁, S₁₂, S₂₁ , or S₂₂) for the cascaded budget object, rfobj.

rfplot(amp,freq) plots the amplifier power characteristics at the operating frequency, specified in freq. (since R2023a)

rfplot(ax,___) plots the cumulative RF budget result or amplifier power characteristics (since R2023a) on the axes specified in ax instead of the current axes. Specify ax as the first input argument followed by any of the input arguments in the previous syntaxes. Return the current axes using the gca function.

Examples

Plot Cumulative Output Power and Gain of RF System

Create an RF system.

Create an RF bandpass filter using the Touchstone® file RFBudget_RF.

f1 = nport('RFBudget_RF.s2p','RFBandpassFilter');

Create an amplifier with a gain of 11.53 dB, a noise figure (NF) of 1.53 dB, and an output third-order intercept (OIP3) of 35 dBm.

a1 = amplifier(Name='RFAmplifier',Gain=11.53,NF=1.53,OIP3=35);

Create a demodulator with a gain of –6 dB, a NF of 4 dB, and an OIP3 of 50 dBm.

d = modulator(Name='Demodulator',Gain=-6,NF=4,OIP3=50, ...
        LO=2.03e9,ConverterType='Down');

Create an IF bandpass filter using the Touchstone file RFBudget_IF.

f2 = nport('RFBudget_IF.s2p','IFBandpassFilter');

Create an amplifier with a gain of 30 dB, a NF of 8 dB, and an OIP3 of 37 dBm.

a2 = amplifier(Name='IFAmplifier',Gain=30,NF=8,OIP3=37);

Calculate the RF budget of the system using an input frequency of 2.1 GHz, an input power of –30 dBm, and a bandwidth of 45 MHz.

b = rfbudget([f1 a1 d f2 a2],2.1e9,-30,45e6)

b = 
  rfbudget with properties:

               Elements: [1x5 rf.internal.rfbudget.Element]
         InputFrequency: 2.1 GHz
    AvailableInputPower: -30 dBm
        SignalBandwidth:  45 MHz
                 Solver: Friis      
             AutoUpdate: true

   Analysis Results
        OutputFrequency: (GHz) [   2.1    2.1   0.07    0.07   0.07]
            OutputPower: (dBm) [-31.53    -20    -26  -27.15  2.847]
         TransducerGain: (dB)  [-1.534  9.996  3.996   2.847  32.85]
                     NF: (dB)  [ 1.533  3.064  3.377   3.611  7.036]
                   IIP2: (dBm) []                                   
                   OIP2: (dBm) []                                   
                   IIP3: (dBm) [   Inf     25  24.97   24.97  4.116]
                   OIP3: (dBm) [   Inf     35  28.97   27.82  36.96]
                    SNR: (dB)  [ 65.91  64.38  64.07   63.83  60.41]

Plot the available output power.

rfplot(b,'Pout')
view(90,0)

Plot the transducer gain.

rfplot(b,'GainT')
view(90,0)

Plot S-parameters of an RF system on a Smith Chart and a Polar plot.

s = smithplot(b,1,1,'GridType','ZY'); 

p = polar(b,2,1); 

Plot Phase and Group Delay of RF System

Create an RF bandpass filter using the Touchstone® file RFBudget_RF.

f1 = nport('RFBudget_RF.s2p','RFBandpassFilter');

Create an amplifier with a gain of 11.53 dB, a noise figure (NF) of 1.53 dB, and an output third-order intercept (OIP3) of 35 dBm.

a1 = amplifier(Name='RFAmplifier',Gain=11.53,NF=1.53,OIP3=35);

Create a demodulator with a gain of –6 dB, a NF of 4 dB, and an OIP3 of 50 dBm.

d = modulator(Name='Demodulator',Gain=-6,NF=4,OIP3=50, ...
        LO=2.03e9,ConverterType='Down');

Create an IF bandpass filter using the Touchstone file RFBudget_IF.

f2 = nport('RFBudget_IF.s2p','IFBandpassFilter');

Create an amplifier with a gain of 30 dB, a NF of 8 dB, and an OIP3 of 37 dBm.

a2 = amplifier(Name='IFAmplifier',Gain=30,NF=8,OIP3=37);

Calculate the RF budget of the system using an input frequency of 2.1 GHz, an input power of –30 dBm, and a bandwidth of 45 MHz.

b = rfbudget([f1 a1 d f2 a2],2.1e9,-30,45e6);

Show the analysis in the RF plot.

rfplot(b)

Group Delay

To plot the group delay, first plot the S11 data for the RF System.

rfplot(b,1,1)

Use the Group Delay option on the plot graph to plot the group delay of the RF system.

Phase Delay

Use the Phase Delay option on the plot graph to plot the phase delay of the RF System.

Plot Amplifier Characteristics

Since R2023a

Create an amplifier object.

amp = amplifier;

Plot the amplifier power characteristics at 2.1 GHz.

rfplot(amp,2.1e9)

Set OIP3 of amplifier to 25 dBm.

amp.OIP3 = 25;

Plot the amplifier power characteristics at 2.1 GHz with nonlinearity.

rfplot(amp,2.1e9)

Plot the amplifier power characteristics on the axes specified in ax instead of the current axes.

f = figure;
ax = axes(f);
rfplot(ax,amp,2.1e9)

Visualize One-Tone and Two-Tone Analysis Results

Since R2023b

One- and two-tone analysis are used to evaluate the performance of nonlinear systems. This example uses a 2-element system with an amplifier, a nonlinear element and a filter.

Define the input frequency, signal power, and signal bandwidth.

freq = 2.1e9;
inputPower = -30; 
bandwidth = 10e6; 

Create an amplifier with a noise figure of 3 dB and OIP3 of 30 dB.

amp = amplifier('Gain', 10, 'NF', 3, 'OIP3', 30);

Create a filter with an input S2P file.

filt = nport('passive.s2p'); 

Create an rfbudget object with amplifier and filter element to model a two-element chain.

rfobj = rfbudget('Elements', [amp filt], 'Solver','HarmonicBalance',...
                 'InputFrequency', freq, ...
                 'AvailableInputPower', inputPower, ...
                 'SignalBandwidth', bandwidth);

Plot the one-tone analysis of the system. Use the one-tone plot to determine the presence of harmonics in the output.

rfplot(rfobj,'OneTone');

Plot the two-tone analysis of the system. Use the two-tone analysis plot to evaluate intermodulation distortion or products of the RF components.

rfplot(rfobj,'TwoTone');

Zoom-in the frequency of interest in the two-tone analysis plot to evaluate the intermodulation distortion (products).

rfplot(rfobj,'TwoTone');
axis([2.09,2.15,-360,-40])

Input Arguments

rfobj — RF budget object

rfbudget object

RF budget object, specified as a rfbudget object.

Example: rfplot(rfobj,'Pout')

rfpara — RF parameters

'Pout' | 'GainT' | 'NF' | 'OIP3' | 'IIP3 | 'SNR' | 'One-Tone' | 'Two-Tone' | 'Sparameters'

RF parameters, specified as one of the following:

• 'Pout' — Available output power (dBm)

• 'GainT' — Transducer gain (dB)

• 'NF'— Noise Figure (dB)

• 'OIP3' - Output Third-Order Intercept (dBm)

• 'IIP3' — Input Third-Order Intercept (dBm)

• 'SNR' — Signal-to-Noise Ratio (dB)

• 'Sparameters' — S - parameters S₂₁ magnitude response (dB)

• 'OneTone' — One-tone analysis (since R2023b)

• 'TwoTone' — Two-tone analysis (since R2023b)

Note

To plot one- and two-tone analysis results, you must compute robj using the harmonic balance solver. (since R2023b)

Example: rfplot(rfobj,'Pout')

amp — Amplifier object

amplifer object

Since R2023a

Amplifier object, specified as an amplifier object.

freq — Operating frequency

positive scalar

Since R2023a

Operating frequency, specified as a positive scalar.

ax — Axes object

axes object | uiaxes object

Axes object, specified as an axes or a uiaxes object.

Version History

Introduced in R2017b

R2023b: Visualize one- and two-tone harmonic balance results of RF budget chain

The rfplot function and the RF Budget Analyzer app now support visualizing one- and two-tone harmonic balance results of the RF budget chain.

R2023a: Visualize amplifier power characteristics

The rfplot function now supports visualizing amplifier power characteristics.