measuredFilter

RF filter circuit model extraction

Since R2024a

Description

Use measuredFilter to create an object that accepts a measured s-parameter data file and extracts the Coupling Matrix and other properties of the filter as analysis results.

Creation

Description

mfilter = measuredFilter creates a default extracted filter model object with a filter order of 4..

mfilter = measuredFilter(PropertyName=Value) sets Properties using one or more name-value arguments. For example, measuredFilter(FilterOrder = 4)

Properties

Sparameters — 2-port s-parameters data

sparameters (default)

2-port s-parameters specified as a sparameters object. It is recommended that the input data comes from a test setup using a calibrated 2-port network analyzer with calibration extended to the test cables. The s-parameter data must include the filter passband response along with sufficient out-of-band rejection for the extraction process to occur.

Example: sparameters('Filter_6A.s2p')

Data Types: sparameters object
Complex Number Support: Yes

FilterOrder — filter order

4 (default) | positive real integer

Filter order of the filter under test specified as a real finite positive integer between [1, 14].

Example: obj = measuredFilter(FilterOrder = 5)

Data Types: double

CenterFrequency — center frequency

1e9 (default) | positive scalar

Center frequency of the filter under test, specified as a scalar in Hz

Example: obj = measuredFilter(CenterFrequency = 850e6)

Data Types: double

BandWidth — bandwidth

10e6 (default) | positive scalar

Bandwidth of the filter under test. specified as a scalar in Hz. measuredFilter uses a narrow-band approximation algorithm where:

• The absolute upper fractional bandwidth limit should be set at 30%

• It is preferred to limit the fractional bandwidth to less than 5%

Example: obj = measuredFilter(BandWidth = 20e6)

Data Types: double

LowPassPoles — lowpass poles

lowpass poles

This is a read-only property (analysis result).

ResidueY11 — y11 y-parameter residue

lowpass filter y11 residue

This is a read-only property (analysis result).

ResidueY12 — y12 y-parameter residue

lowpass filter y12 residue

This is a read-only property (analysis result).

ResidueY21 — y21 y-parameter residue

lowpass filter y21 residue

This is a read-only property (analysis result).

ResidueY22 — y22 y-parameter residue

lowpass filter y22 residue

This is a read-only property (analysis result).

CouplingMatrix — Coupling Matrix

extracted coupling matrix

This is a read-only property (analysis result).

QualityFactor — Quality factor (Q-factor)

filter quality factor

This is a read-only property (analysis result).

Object Functions

residue	Extract lowpass admittance residues and poles of a measuredFilter object
transversalMat	Calculate the transversal matrix of a measuredFilter object
canonicalCouplingMat	Perform canonical matrix rotation
optimize	Isospectral optimization of a measuredFilter object
sparameters	Calculate S-parameters for RF PCB objects
qualityfactor	Calculates the unloaded quality factor of a measuredFilter object

Examples

Measured Filter S-Parameter Extraction

This example shows how to input a measured data file and extract its s-parameters

S_measured = sparameters(fullfile(matlabroot,'toolbox','rfpcb',...
'rfpcb','rfpcbfilterfiles','FILTER_8.s2p'));
rfplot(S_measured); hold on
obj = measuredFilter(...
Sparameters=S_measured,BandWidth=9.601e6,...
CenterFrequency=2114.6528e6,FilterOrder=8);
S_calc = sparameters(obj);
rfplot(S_calc,'--')

Version History

Introduced in R2024a