Filter
A filter of complex RF broadband signals.
blockType: Filter
Path in the library:
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Description
Unit Filter is a filter for complex radio frequency (RF) broadband signals. You can use the Butterworth, Chebyshev, or inverse Chebyshev methods to design the filter. You can also model the filter in the time or frequency domain and plot its characteristics.
Ports
Input
#
IN
—
time-dependent input signal
real scalar | real column | real column | complex scalar | complex column
Details
A time-dependent input signal given as a real scalar or column, complex scalar or column. The column represents successive points in time.
Data types |
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Complex numbers support |
Yes |
Output
#
OUT
—
time-dependent output signal
complex scalar
| complex column
Details
A time-dependent output signal returned as a complex scalar or column. The time-dependent output signal is equal in size to the time-dependent input signal.
Data types |
|
Complex numbers support |
Yes |
Parameters
Main
#
Design method —
filter design method
Butterworth
| Chebyshev
| InverseChebyshev
Details
Filter Design Method. Defined as:
-
Butterworth
-
Chebyshev
-
InverseChebyshev
Values |
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Default value |
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Program usage name |
|
Tunable |
No |
Evaluatable |
No |
#
Filter type —
filter response type
Lowpass
| Highpass
| Bandpass
| Bandstop
Details
Filter response type. Defined as:
-
Lowpass
- simulates the type of low-pass filter with the design specified in Design method. -
Highpass
- simulates a high-pass filter type with the method specified in Design method. -
Bandpass
- simulates a bandpass filter type with the method specified in Design method. -
Bandstop
- simulates the bandpass filter type with the method specified in . Design method.
Values |
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Default value |
|
Program usage name |
|
Tunable |
No |
Evaluatable |
No |
#
Implement using filter order —
enable implementation using filter order
Logical
Details
Select this check box to implement the filter order manually.
Default value |
|
Program usage name |
|
Tunable |
No |
Evaluatable |
No |
#
Filter order —
filter order
Real number
Details
The filter order, specified as an integer, is . If a value of Filter type value is selected Lowpass
or Highpass
, specify the number of single storage items. If the parameters Filter type value is selected Bandpass
or `Bandstop`or , specify twice the number of items.
Dependencies
To use this parameter, tick the checkbox of the parameters Implement using filter order.
Default value |
|
Program usage name |
|
Tunable |
No |
Evaluatable |
Yes |
#
Passband frequency (Hz) —
bandwidth frequency
Real number
Details
The bandwidth frequency for low-pass, high-pass and bandpass filters, specified as a positive real scalar or a positive ascending vector of two values. Depending on the filter type, the accepted value types and values by default differ:
Parameters value Filter type | Value type | Value types Default values (Hz) |
---|---|---|
|
Positive real scalar |
|
|
Positive real scalar |
|
|
Positive increasing vector of two values |
|
Dependencies
To use this parameter, set the parameter Filter type value Lowpass
, Highpass
or Bandpass
.
Default value |
|
Program usage name |
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Tunable |
No |
Evaluatable |
Yes |
#
Stopband frequency (Hz) —
bandwidth frequencies for bandpass filters
Real number
Details
Bandwidth frequencies for bandpass filters, given as a positive real scalar or a positive increasing vector of two values, in Hz.
In parameters Filter type и Implement using filter order accepted types of values and values by default differ as follows.
Parameter value Filter type | Value type | Default values (Hz) | To enable this parameter |
---|---|---|---|
|
Positive real scalar |
|
Set to Filter type value |
|
Positive real scalar |
|
Set to Filter type value |
|
Positive increasing vector of two values |
|
Set to Filter type value |
|
Positive increasing vector of two values |
|
Set the value for the Filter type value |
Default value |
|
Program usage name |
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Tunable |
No |
Evaluatable |
Yes |
#
Stopband attenuation (dB) —
attenuation in the delay band
Real number
Details
Attenuation in the delay band, given as a positive real scalar greater than the value of the parameters *Passband attenuation (dB)*in dB.
Dependencies
To use this parameter:
-
Set the parameters to. Filter type value
Lowpass
,Highpass
orBandpass
and uncheck the box Implement using filter order. -
Set Filter type value `Bandstop`and tick the checkbox Implement using filter order.
Default value |
|
Program usage name |
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Tunable |
No |
Evaluatable |
Yes |
#
RF frequency (Hz) —
signal band centre
Real number
Details
The centre of the signal bandwidth with respect to the filter transfer function, specified as a positive real scalar, in Hz.
Default value |
|
Program usage name |
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Tunable |
No |
Evaluatable |
Yes |
Main
#
Modeling domain —
modelling domain
Time (Fixed step)
| Frequency (Digital filter)
Details
Modelling area. Defined as:
-
Time (Fixed step)
- modelling with usage of fixed step solvers (NDF2
,Trapezoidal
,Backward Euler
) -
Frequency (Digital filter)
- modelling with a 1-D digital filter.
Values |
|
Default value |
|
Program usage name |
|
Tunable |
No |
Evaluatable |
No |
#
Solver —
time domain solvers
NDF2
| Trapezoidal
| Backward Euler
Details
Fixed-step solvers. Defined as:
-
NDF2
- A balance of narrowband and wideband accuracy. This solver is suitable for situations where the frequency content of the signals in the system is unknown with respect to the Nyquist frequency. -
Trapezoidal
- performs narrowband modelling. Frequency distortion and lack of damping effects make this method unsuitable for most wideband modelling. -
Backward Euler
- Modelling the largest class of systems and signals. Damping effects make this solver suitable for broadband modelling, but overall accuracy is low.
Values |
|
Default value |
|
Program usage name |
|
Tunable |
No |
Evaluatable |
No |
#
FIR filter length —
Length of 1-D digital filter
Real number
Details
The 1-D digital filter length or impulse response duration specified as a positive integer.
Dependencies
To use this parameter, set the parameters to Modeling domain value Frequency (Digital filter)
.
Default value |
|
Program usage name |
|
Tunable |
No |
Evaluatable |
Yes |
Optional
Algorithms
Determination of FIR filter coefficients
The programme calculates the coefficients of the discrete FIR filter using the parameters RF frequency (Hz) и *FIR filter length*and the transfer function defined using the obtained poles and zeros of the filter.
To determine the coefficients of the direct form of the Discrete FIR Filter block, the following steps are performed:
-
Determines the frequency points that are in the passband centred around the carrier frequency using this formula.
where
-
- is the carrier frequency, in Hz.
-
- is the length of the FIR filter.
-
- is the time step of the filter.
-
Determines the transfer function values for the frequency points specified in step 1 using this formula.
-
-
Determines the coefficients of the discrete FIR filter using this formula