Matched Filter
Matched filter.
Description
The Matched Filter block implements matched filtering of the input signal. Matched filtering is a FIR filtering operation with coefficients equal to the time reversed samples of the transmitted signal. The filter can improve the SNR before detection.
Ports
Input
X - input signal
complex matrix M by N
The input signal is in the form of a complex matrix M by N. Matched filtering is applied on the first dimension. The input X and output Y have the same dimensions. The initial transient is removed from the filtered result.
The size of the first dimension of the input matrix may be varied to mimic the varying signal length. The size variation may occur, for example, in the case of a pulse signal with a variable pulse repetition rate.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Coeff - coefficients of matched filter
complex vector-column of length M
Coefficients of the matched filter as a complex vector-column of length M.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Dependencies
To use this port, set Source of coefficients to Input port.
Output
Y is the output of the matched filter
complex matrix M by N
The output of a matched filter returned as a complex matrix M by N. The dimensions of the output Y are the same as the dimensions of the input X.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
G - gain of the matched filter
`valid matrix of size N
The matched filter gain returned as a valid matrix of size N. The gain is calculated for each column X. Units in dB.
Dependencies
To use this port, select the Enable SNR gain output checkbox.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Parameters
Source of coefficients - source of coefficients of matched filter
Property (by default) | Input port
Set whether the matched filter coefficients come from the Coefficients parameters or from the input port.
-
Property- the matched filter coefficients are specified by the Coefficients parameters. -
Input port- the matched filter coefficients are set via the Coeff input port.
Coefficients - coefficients of the matched filter
[1;1] (by default).
Set the coefficients of the matched filter as a column vector. This parameter is used when you set the Property value for the Source of coefficients parameter.
Spectrum window - window for spectral weighting
None (By default) | Hamming | Chebyshev | Hann | Kaiser | Taylor
Specify the window used for spectral weighting using one of the options:
-
None. -
Hamming -
`Chebyshev
-
`Hann
-
Kaiser
-
Taylor
Spectral weighting is often used with linear FM signals to reduce side lobe levels in the time domain. The block calculates the window length internally to match the FFT length.
Spectrum window range (Hz) - coverage area of the spectrum window
[0, 1e5] (By default)
Specify the spectrum range in hertz to which Spectrum window is applied as a 1 by 2 vector in the form [StartFrequency, EndFrequency].
Note that both parameters StartFrequency and EndFrequency are measured in the main frequency band. That is, they are within [-Fs/2,Fs/2], where Fs is the sampling frequency specified in any of the signal library blocks. The parameters StartFrequency must be less than EndFrequency.
Dependencies
This parameter is used when you set the Spectrum window parameter to any value other than None.
Inherit sample rate - inherit sample rate
Enabled (By default) | Off
Select the checkbox to inherit sample rate from upstream blocks. Otherwise, set the sample rate using the Sample rate (Hz) parameters.
Sample rate (Hz) - sampling rate
1e6 (By default) | Positive scalar
The sampling frequency of the signal as a positive scalar. The unit of measurement is Hz.
The ratio of Sample rate (Hz) to Pulse repetition frequency (Hz) must be an integer. This restriction is equivalent to requiring that the pulse repetition interval be an integer multiple of the sampling interval.
Dependencies
To use this parameter, clear the Inherit sample rate checkbox.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Sidelobe attenuation level - side lobe attenuation level
30 (By default)
Set the side lobe attenuation level (in dB) of the Chebyshev or Taylor window as a positive scalar value.
Dependencies
This parameter is used when you set the Spectrum window parameters to Chebyshev or Taylor.
Kaiser shape parameter - the Kaiser shape parameter
0.5 (By default).
Set the parameter that affects the attenuation of the side lobe of the Kaiser window as a non-negative scalar.
Dependencies
This parameter is used when you set the Spectrum window parameters to Kaiser.
Number of constant level sidelobes - number of almost constant level sidelobes in the Taylor window
4 (By default).
Set the number of almost constant level sidelobes adjacent to the main sidelobe in the Taylor window as a positive integer.
Dependencies
This parameter is used when you set the Spectrum window parameter to Taylor.
Enable SNR gain output - Enable SNR gain output
off (By default) | `on
Select this checkbox to receive the SNR gain of the matched filter through the G output port. The output port is used when this check box is selected.