rfbudget

Create RF budget object and compute RF budget results for chain of 2-port elements

Description

Use the rfbudget object to create an RF budget object and compute the RF budget results for a chain of 2-port elements. In this RF chain, you can use a 2-port element such as amplifier, nport, or modulator. You can also open the rfbudget object in an RF Budget Analyzer app and then export the completed circuit to RF Blockset™ for circuit envelope analysis.

Creation

Syntax

rfobj = rfbudget

rfobj = rfbudget(elements,inputfreq,inputpwr,bandwidth)

rfobj = rfbudget(___,autoupdate)

rfobj = rfbudget(Name=value)

Description

rfobj = rfbudget creates an rfbudget object, rfobj, with default empty property values.

rfobj = rfbudget(elements,inputfreq,inputpwr,bandwidth) sets Elements, InputFrequency, AvailableInputPower, and SignalBandwidth properties and computes the RF budget analysis. By default, if any of the input properties are changed, the object recomputes results.

rfobj = rfbudget(___,autoupdate) sets the AutoUpdate property. You can use this syntax with any of the previous syntaxes.

rfobj = rfbudget(Name=value) sets Properties using one or more name-value arguments. You can specify multiple name-value arguments.

Properties

Elements — RF budget elements

[] (default) | RF budget object | array of RF budget objects

RF budget elements, specified as an RF budget object or an array of RF budget objects. Use an array of RF budget objects when you perform RF budget analysis on an RF chain.

This table lists supported RF budget elements you can use to design an RF chain.

Element Type	RF Budget Elements
Linear Elements	attenuator
	rfantenna
	rffilter
	nport
	seriesRLC
	shuntRLC
	phaseshift
	txlineCoaxial
	txlineCPW
	txlineMicrostrip
	txlineParallelPlate
	txlineRLCGLine
	txlineStripline
	txlineTwoWire
	txlineEquationBased
	txlineDelayLossless
	txlineDelayLossy
Nonlinear Elements	amplifier
	modulator
	rfelement
	mixerIMT

Example: a = amplifier; m = modulator; rfbudget(Elements=[a m]) calculates the RF budget analysis of the amplifier and modulator circuit.

InputFrequency — Input frequency of signal

[] (default) | nonnegative scalar or column vector in Hz

Input frequency of the signal, specified as a nonnegative scalar or column vector (since R2023a) of size M-by-1 in Hz. M represents number of frequencies. If the input frequency is a vector, then the RF budget object analyzes each input frequency separately.

Example: InputFrequency=2e9

Data Types: double

AvailableInputPower — Power applied at input of cascade

[] (default) | scalar in dBm

Power applied at the input of the cascade, specified as a scalar in dBm.

Example: AvailableInputPower=-30

Data Types: double

SignalBandwidth — Signal bandwidth at input of cascade

[] (default) | scalar in Hz

Signal bandwidth at the input of the cascade, specified as a scalar in Hz.

Example: SignalBandwidth=10

Data Types: double

AutoUpdate — Automatically recompute RF budget analysis

true (default) | false

Automatically recompute the RF budget analysis by incorporating changes made to the existing circuit, specified as true or false.

Setting AutoUpdate to false turns off automatic budget recomputation as parameters change. To compute the budget result of an rfbudget object when you set the AutoUpdate property to false, use the computeBudget function.

Example: AutoUpdate=false

Data Types: logical

Solver — Computation Method

Friis (default) | HarmonicBalance

Computation method, specified as Friis or HarmonicBalance. The Friis solver is faster and the HarmonicBalance solver supports computation of second-order nonlinearities such as OIP2.

When you set the Solver type to HarmonicBalance, the tone and harmonic-dependent properties are displayed.

Note

The HarmonicBalance solver does not support architectures where the input or output frequencies at any stage in the cascade are nonzero and less than SignalBandwidth.

Example: Solver='Friis'

Data Types: string

MaxHarmonics — Maximum number of harmonics for each tone in one- and two-tone HB analyses

[] (default) | positive integer

Since R2024a

Maximum number of harmonics to use for each tone in one- and two-tone harmonic balance (HB) analyses, specified as a positive integer. Use this property for faster HB analysis and set MaxHarmonics to [] to return to the default automatic determination of harmonics.

Example: MaxHarmonics=5

Dependencies

To enable this property, set Solver to HarmonicBalance.

Data Types: double

MinHarmonics — Minimum number of harmonics for each tone in one- and two-tone HB analyses

[] (default) | positive integer

Since R2024a

Minimum number of harmonics to use for each tone in one- and two-tone harmonic balance (HB) analyses, specified as a positive integer. Use this property to achieve higher-fidelity HB simulation in highly nonlinear systems and set MinHarmonics to [] to return to the default automatic determination of harmonics.

Example: MinHarmonics=5

Dependencies

To enable this property, set Solver to HarmonicBalance.

Data Types: double

HarmonicOrder — Number of harmonics to use for all tones in HB analyses

[] (default) | positive integer

Number of harmonics to use for one-tone harmonic balance (HB) analysis, specified as a positive integer. For each two-tone analysis, max(3,HarmonicOrder) harmonics is used. Use the default value for automatic determination of harmonics.

Use this property to

• Accelerate the HB analysis by reducing the number of harmonics needed for a mildly nonlinear system.

• Ensure harmonic balance accuracy by increasing the number of harmonics used in a highly nonlinear system.

Dependencies

To enable this property, set Solver to HarmonicBalance.

Data Types: double

OutputFrequency — Output frequencies

scalar | vector | matrix

This property is read-only.

Output frequencies in Hz, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Data Types: double

OutputPower — Output power

scalar | vector | matrix

This property is read-only.

Output power in dBm, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Data Types: double

TransducerGain — Transducer power gains

scalar | vector | matrix

This property is read-only.

Transducer power gains in dB, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Data Types: double

NF — Noise figures

scalar | vector | matrix

This property is read-only.

Noise figures in dB, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Note

If AvailableInputPower is very large, it can result in negative NF values during harmonic balance analysis [1].

Data Types: double

IIP2 — Input-referred second-order intercept

scalar | vector | matrix

This property is read-only.

Input-referred second-order intercept (IIP2) in dBm, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Dependencies

To compute IIP2 values, set Solver to HarmonicBalance.

Data Types: double

OIP2 — Output-referred second-order intercept

scalar | vector | matrix

This property is read-only.

Output-referred second-order intercept (OIP2) in dBm, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Dependencies

To compute OIP2 values, set Solver to HarmonicBalance.

Data Types: double

IIP3 — Input-referred third-order intercept

scalar | vector | matrix

This property is read-only.

The Input-referred third-order intercept (IIP3) in dBm, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Data Types: double

OIP3 — Output-referred third-order intercept

scalar | vector | matrix

This property is read-only.

The Output-referred third-order intercept (OIP3) in dBm, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Data Types: double

SNR — Signal-to-noise ratio

scalar | vector | matrix

This property is read-only.

Signal-to-noise ratio (SNR) in dB, returned as one of the following:

• Scalar when M and N = 1

• Vector when M or N = 1

• Matrix when M and N > 1

where M represents the number of frequencies in the input and N represents the number of stages in the cascade.

Data Types: double

WaitBar — Display progress bar

true (default) | false

Display a progress bar with a cancel button during harmonic balance analysis, specified as true or false.

Data Types: logical

Object Functions

show	Display RF budget object in RF Budget Analyzer app
computeBudget	Compute results of RF budget object
computeAMPMTable	Compute AM/AM-AM/PM table representation from RF budget object
exportScript	Export MATLAB code that generates RF budget object
exportRFBlockset	Export RF budget object to RF Blockset Model
exportTestbench	Export RF budget object to RF Blockset measurement testbench model
exportTransmitter	Export RF budget summary to create phased transmitter
exportReceiver	Export RF budget summary to create phased receiver
rfplot	Plot cumulative RF budget result vs. cascade input frequency and amplifier power characteristics
smithplot	Plot measurement data on a Smith chart
polar	Plot specified object parameters on polar coordinates

Examples

Default RF Budget

Open a default RF budget object.

obj = rfbudget

obj = 
  rfbudget with properties:

               Elements: []
         InputFrequency: [] Hz 
    AvailableInputPower: [] dBm
        SignalBandwidth: [] Hz 
                 Solver: Friis      
             AutoUpdate: true

RF Budget Analysis of Series of RF Elements

Create an amplifier with a gain of 4 dB.

a = amplifier(Gain=4);

Create a modulator with an OIP3 of 13 dBm.

m = modulator(OIP3=13);

Create an N-port element using passive.s2p.

n = nport('passive.s2p');

Create an RF element with a gain of 10 dB.

r = rfelement(Gain=10);

Calculate the RF budget of a series of RF elements at an input frequency of 2.1 GHz, an available input power of –30 dBm, and a bandwidth of 10 MHz.

b = rfbudget([a m r n],2.1e9,-30,10e6)

b = 
  rfbudget with properties:

               Elements: [1x4 rf.internal.rfbudget.Element]
         InputFrequency: 2.1 GHz
    AvailableInputPower: -30 dBm
        SignalBandwidth:  10 MHz
                 Solver: Friis      
             AutoUpdate: true

   Analysis Results
        OutputFrequency: (GHz) [  2.1    3.1    3.1     3.1]
            OutputPower: (dBm) [  -26    -26    -16   -20.6]
         TransducerGain: (dB)  [    4      4     14     9.4]
                     NF: (dB)  [    0      0      0  0.1392]
                   IIP2: (dBm) []                           
                   OIP2: (dBm) []                           
                   IIP3: (dBm) [  Inf      9      9       9]
                   OIP3: (dBm) [  Inf     13     23    18.4]
                    SNR: (dB)  [73.98  73.98  73.98   73.84]

Type the show command at the command window to display the analysis in the RF Budget Analyzer app.

show(b)

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); 

Harmonic Balance Solver for Nonlinear RF Budget Analysis

Create two modulators with output-referred second-order intercept set to 20 and available power gain set to 3.

m = modulator(Gain=3,OIP2=20,ImageReject=false,ChannelSelect=false);
m2 = modulator(Gain=3,OIP2=20,ImageReject=false,ChannelSelect=false);

Create an RF budget object specifying the input frequency of the signal, power applied at cascade, and signal bandwidth. Select HarmonicBalance as solver method to compute nonlinear effects such as IIP2 and OIP2.

b = rfbudget([m m2],2.1e9,-30,100e6,Solver='HarmonicBalance')

b = 
  rfbudget with properties:

               Elements: [1x2 modulator]
         InputFrequency: 2.1 GHz
    AvailableInputPower: -30 dBm
        SignalBandwidth: 100 MHz
                 Solver: HarmonicBalance
                WaitBar: true
             AutoUpdate: true

   Analysis Results
        OutputFrequency: (GHz) [  3.1    4.1]
            OutputPower: (dBm) [  -27    -24]
         TransducerGain: (dB)  [    3      6]
                     NF: (dB)  [ 3.01  7.783]
                   IIP2: (dBm) [   17  4.457]
                   OIP2: (dBm) [   20  10.46]
                   IIP3: (dBm) [  Inf    Inf]
                   OIP3: (dBm) [  Inf    Inf]
                    SNR: (dB)  [60.96  56.19]

Number of Harmonics in HB Analysis

Create an amplifier with a gain of 10 dB.

a = amplifier(Gain=10);

Create a modulator with an OIP3 of 13 dBm.

m = modulator(OIP3=13);

Create an N-port circuit element using passive.s2p.

n = nport('passive.s2p');

Calculate the RF budget of a series of RF elements at an input frequency of 2.1 GHz, an available input power of –30 dBm, and a bandwidth of 10 MHz using HB analysis. Set the number of harmonics that the rfbudget object should use for all the tones in HB analyses.

b = rfbudget([a m n],2.1e9,-30,10e6,...
    Solver="HarmonicBalance",HarmonicOrder=3)

b = 
  rfbudget with properties:

               Elements: [1x3 rf.internal.rfbudget.Element]
         InputFrequency: 2.1 GHz
    AvailableInputPower: -30 dBm
        SignalBandwidth:  10 MHz
                 Solver: HarmonicBalance
          HarmonicOrder: 3
                WaitBar: true
             AutoUpdate: true

   Analysis Results
        OutputFrequency: (GHz) [       2.1        3.1     3.1]
            OutputPower: (dBm) [       -20        -20   -24.6]
         TransducerGain: (dB)  [        10      9.996   5.396]
                     NF: (dB)  [-2.842e-14  -0.004353  0.3376]
                   IIP2: (dBm) [       Inf        Inf     Inf]
                   OIP2: (dBm) [       Inf        Inf     Inf]
                   IIP3: (dBm) [       Inf      2.997   2.998]
                   OIP3: (dBm) [       Inf      12.99   8.391]
                    SNR: (dB)  [     73.98      73.98   73.64]

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.

Tips

• The Touchstone file in the nport object must be passive at all specified frequencies. To make N-port S-parameters passive, use the makepassive function.

Algorithms

ABCD parameters are used in the computation of S-parameters of the cascade for Friis Solver. When S21 = 0, conversion to ABCD results in NaNs. For such cases, modifications to the S-parameters are made as follows:

S₂₁ = 0, S₁₁ = -1, and S₂₂ ≠ -1

• Connected large resistance (R_p = 10¹² ohm) in parallel with the network.

• Connected small resistance (R_s = 10^-12 ohm) in series to the beginning of the network.

S₂₁ = 0, S₂₂ = -1, and S₁₁ ≠ -1

• Connected large resistance (R_p = 10¹² ohm) in parallel with the network.

• Connected small resistance (R_s = 10^-12 ohm) in series after the network.

S₂₁ = 0, S₂₂ = -1, and S₁₁ = -1

• Connected large resistance (R_p = 10¹² ohm) in parallel with the network.

• Connected small resistance (R_s = 10^-12 ohm) in series to the beginning of the network.

• Connected small resistance (R_s = 10^-12 ohm) in series after the network.

S₂₁ = 0

• Connected large resistance (R_p = 10¹² ohm) in parallel with the network.

References

[1] Roychowdhury, J., D. Long, and P. Feldmann. “Cyclostationary Noise Analysis of Large RF Circuits with Multitone Excitations.” IEEE Journal of Solid-State Circuits 33, no. 3 (March 1998): 324–36. https://doi.org/10.1109/4.661198.

Version History

Introduced in R2017a

R2024a: Control number of harmonics in HB simulation using rfbudget object

You can now use the rfbudget object to increase the number of harmonics for higher fidelity HB simulation and reduce the number of harmonics for faster HB simulation.

R2023b: Recommended over rfckt.cascade and analyze

rfbudget is recommend over rfckt.cascade and analyze because it enables you to:

• Create an RF budget chain and compute the RF budget results for a chain of two-port elements. You can include linear and nonlinear elements in your chain. For more information, see Elements.

• Compute gain, noise figure, IP2, and IP3 of cascaded RF elements using Friis and harmonic balance solvers and export the RF chain to RF Blockset and rfsystem for circuit envelope analysis.

R2023a: InputFrequency property now accepts only nonnegative scalar and vector values

Starting this release, you can specify the InputFrequency property of the rfbudget object as a nonnegative scalar or as a column vector of nonnegative values.

The rfbudget object throws an error if you set the InputFrequency property to a negative value. Update the property to a positive value in existing circuits designed using the rfbudget object to ensure accurate RF budget computations.

R2022b: Specify number of harmonics to use for all tones in HB analysis

Specify the number of harmonics for all tones in HB analyses by setting the HarmonicOrder property in the rfbudget object.