Engee documentation

Filter

A filter of complex RF broadband signals.

filter

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

Float64 | Float32.
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

Float64 | Float32.
Complex numbers support

Yes

Parameters

Main

# Design method — filter design method
Butterworth | Chebyshev | InverseChebyshev

Details

Filter Design Method. Defined as:

  • Butterworth

  • Chebyshev

  • InverseChebyshev

Values

Butterworth | Chebyshev | InverseChebyshev
Default value

Butterworth
Program usage name

DesignMethod
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

Lowpass | Highpass | Bandpass | Bandstop
Default value

Lowpass
Program usage name

ResponseType
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

true (switched on)
Program usage name

UseFilterOrder
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

3
Program usage name

FilterOrder
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)

Lowpass

Positive real scalar

1e9

Highpass

Positive real scalar

2000000000

Bandpass

Positive increasing vector of two values

[2000000000 3000000000]

Dependencies

To use this parameter, set the parameter Filter type value Lowpass, Highpass or Bandpass.

Default value

1.0e9
Program usage name

PassFreq_lp
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

Lowpass

Positive real scalar

2000000000

Set to Filter type value Lowpass and uncheck the box Implement using filter order

Highpass

Positive real scalar

1000000000

Set to Filter type value Highpass and uncheck the box Implement using filter order

Bandpass

Positive increasing vector of two values

[1500000000 3500000000]

Set to Filter type value Bandpass` and uncheck the box Implement using filter order

Bandstop

Positive increasing vector of two values

[2100000000 2900000000]

Set the value for the Filter type value Bandstop and clear or select the check box Implement using filter order
Default value

2.0e9
Program usage name

StopFreq_lp
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 or Bandpass and uncheck the box Implement using filter order.

  • Set Filter type value `Bandstop`and tick the checkbox Implement using filter order.

Default value

40
Program usage name

StopAtten
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

1.0e9
Program usage name

RF
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

Time (Fixed step) | Frequency (Digital filter)
Default value

Time (Fixed step)
Program usage name

ModelingDomain
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

NDF2 | Trapezoidal | Backward Euler
Default value

NDF2
Program usage name

SolverFixedStep
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

128
Program usage name

LengthFir
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:

  1. 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.

    1. Determines the transfer function values for the frequency points specified in step 1 using this formula.


  1. Determines the coefficients of the discrete FIR filter using this formula