MATLAB: How to pass Z-parameters as a parameter input to the plot function of the rfckt.cascade object within the RF Toolbox 2.3 (R2008a)

RF Toolbox

I am using the "rfckt.cascade" object to create a tee network using the RF Toolbox 2.3.

I am able to analyze and plot the S-parameters of this object successfully, but I need to view the plot of the Z-parameters of this object. However, the PLOT function of the "rfckt.cascade" object does not accept Z-parameters z11, z21, etc. as valid arguments.

Best Answer

The ability to do pass Z-parameters as input arguments to the "plot" function of the "rfckt.cascade" object is not available in the RF Toolbox.

As a workaround, use the S2Z function to convert S-parameters from the "AnalyzedResult.S_Parameter" field of the "rfckt.cascade" object into the equivalent Z parameters. Then, replace the "AnalyzedResult.S_Parameter" with the output of the S2Z function and plot the results of the "rfckt" object.

Related Solutions

MATLAB: How to cascade a four port device with a two port device using rfckt objects in RF Toolbox

Unlike RF Blockset which has a 'Coupler' block for Simulink, there is no four port device rfckt object. In RF Toolbox, rfckt circuit objects are designed for chain of objects, i.e. we are limited to two port networks. As a workaround, if you could represent the Coupler as a 2 port network touchstone file, it will be possible to read the file and create a 'rfckt.passive' element with it. And then we can continue do the RF analysis on that network.

Please refer to the sample scripts below demonstrating this using two approaches -

1. Use the 'nport' object which reads both S-parameters and noise data from a Touchstone file. Then cascade them using an 'rfbudget' object. This sample script is the recommended and approach and it uses some functions which were released in MATLAB R2017a.

%%Using NEW nport objects (Recommended)/Approach 1
%%Read in a 3 Port coupler 

S3 = sparameters('default.s3p');

Coupler to to 2-port nport

S2 = snp2smp(S3);
rfwrite(S2, 'coupler2port.s2p')
% Creating a nport object
Coupler2port = nport('coupler2port.s2p');
% Note that coupler does not have noise of its own.
ckt1 = nport('default.s2p'); % Other 2 port sparameter device

% Noise Data can be viewed by doing ckt1.NoiseData
%%CASCADE

ckt_cascade = rfbudget([Coupler2port ckt1],[2e9:1e9:10e9],-30,10);
show(ckt_cascade);

To export the network into Simulink, i.e. RF Blockset please uncomment and execute the command below

% exportRFBlockset(ckt_cascade)

2. Use the 'rfckt.amplifier' object which contains both S-parameter and noise data. Then cascade them using 'rfckt.cascade'. This approach is not recommended, as it might be not available in future releases.

%%Using OLD rfckt objects /Approach 2
%%Read in a 3 Port coupler 
ckt = read(rfckt.passive,'default.s3p'); % This only works for passive data
s3p = ckt.NetworkData.Data;
Z0 = ckt.NetworkData.Z0;

Coupler to to 2-port rfckt.amplifier

s2p = snp2smp(s3p,Z0);
% Creating a rfckt object
rfwrite(s2p,ckt.NetworkData.Freq,'coupler2port_ckt.s2p')
Coupler2port = read(rfckt.amplifier,'coupler2port_ckt.s2p');
ckt1 = read(rfckt.amplifier,'default.s2p'); % Other 2 port sparameter device
%%CASCADE
ckt_cascade = rfckt.cascade('Ckts', {Coupler2port, ckt1});
analyze(ckt_cascade, 2.9e9)

MATLAB: Does converting a multiple port S-parameters to Verilog-A module give me an error

With 55-port input data, the value returned by 'rationalfit' is a 55x55 array of fit objects. As shown in the error message above, the first input argument of 'writeva' must be a scalar, not a 55x55 array.

The solution is to loop through the elements of the fit array by indexing fit(i,j), for example.:

>> status = writeva(fit(1,1),'tmp')
status =
    logical

Best Answer

Related Solutions

MATLAB: How to cascade a four port device with a two port device using rfckt objects in RF Toolbox

MATLAB: Does converting a multiple port S-parameters to Verilog-A module give me an error

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