Multiband Combiner

Frequency-shift and combine signals

Since R2021b

• 

Libraries:
Communications Toolbox / RF Impairments and Components

Description

The Multiband Combiner block interpolates, shifts input signals to the specified frequency bands, and then combines them into a single signal. For more information, see the Algorithms section.

Examples

Combine QPSK and GMSK Signals Using Simulink

Combine two 60 KHz frequency bands adjacent to each other.

Run the model to explore how combining the frames affects the signals. The model frequency shifts and combines frames of QPSK and GMSK baseband modulated signals. A spectrum analyzer displays the individual and combined signals.

Extended Examples

Interference Modeling

Interference modeling in a bent pipe satellite communications link.

• Open Model

Ports

Input

In — Input signals

N_samp-by-N_chan matrix

Input signals, specified as an N_samp-by-N_chan matrix. N_samp is the number of input samples per channel and N_chan is the number of channels.

Data Types: double | single
Complex Number Support: Yes

Output

Out — Output signal

N_out-by-1 vector

Output signal, returned as an N_out-by-1 vector of the same data type as input signal In. N_out is the number of output samples. The Rate options parameter specifies single-rate or multirate mode. For more information, see Algorithms.

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Input sample rate (Hz) — Input signal sample rate

1e6 (default) | positive scalar

Input signal sample rate in Hz, specified as a positive scalar.

Frequency offsets (Hz) — Frequency offsets

[0 1e6] (default) | scalar | 1-by-N_chan vector

Frequency offsets in Hz, specified as one of these options.

• Scalar — Each channel of the input signal is frequency-shifted by this scalar value.

• 1-by-N_chan vector — Each channel of the input signal is frequency-shifted by the corresponding value in this vector. N_chan is the number of channels in the input signal In.

Rate options — Options for processing rate

Enforce single-rate processing (default) | Allow multirate processing

Options for the processing rate, specified as one of these values.

• Enforce single-rate processing — The output sample rate must be an integer multiple of the input sample rate. The number of rows in the output is higher than or equal to the number of rows in the input signal. The output frame rate is equal to the input frame rate.

• Allow multirate processing — The output has the same number of rows as the input. The output frame rate is higher than or equal to the input frame rate.

For more information, see the Algorithms section.

Output sample rate options — Options for output sample rate

Auto (default) | Specify via property

Options for the output sample rate, specified as one of these values.

• Auto — The block interpolates the input signals to ensure that the resulting sample rate of the signals is sufficient to avoid distorting the frequency content of the original signals after they are frequency-shifted to produce the output signal.

• Specify via property — Specify the output sample rate by using the Output sample rate (Hz) parameter.

Output sample rate (Hz) — Output signal sample rate

3e6 (default) | positive scalar

Output signal sample rate in Hz, specified as a positive scalar.

Tips

To avoid distortion, specify this value to be greater than or equal to the automatically computed output sample rate. To determine the automatically computed output sample rate, first run the block with the Output sample rate options parameter set to Auto.

Dependencies

To enable this parameter, set the Output sample rate options parameter to Specify via property.

Output delay (samples) — Output delay

36 (default) | positive scalar

This parameter is read-only.

Output delay in samples, specified as a positive scalar.

Block Characteristics

Data Types	double | single
Multidimensional Signals	no
Variable-Size Signals	no

Algorithms

Multiband Combiner

This figure shows how the multiband combiner algorithm processes input signal data.

When the output sample rate is greater than the input sample rate, the input signal is interpolated to avoid distortion in the frequency-shifted signal. Each column of the input signal is frequency-shifted by the corresponding value specified in the Frequency offsets (Hz) parameter. The frequency-shifted signals are then added together into a single channel output signal. Each channel in the input must have the same number of samples.

The Rate options parameter enables operation of the block in single-rate mode or multirate mode. For single-rate mode, the output frame rate equals the input frame rate. For multirate mode, the output frame rate is increased by the ratio of the interpolation and decimation factors (that is, by L/M). The interpolation and decimation factors are computed as [L,M] = rat(R_O/R_I).

When the algorithm is configured to automatically compute the output sample rate, the output sample rate is computed as R_O = R_I × L/M

• R_O is the output sample rate specified in Output sample rate (Hz).

• R_I is the input sample rate specified in Input sample rate (Hz).

• L is the interpolation factor and is computed as L = ceil(2 × B_max/R_I).

• M is the decimation factor.

• B_max is the maximum bandwidth and is computed as B_max = max(abs(Frequency offsets (Hz))) + (R_I/2).

Multiband Combining Delay

Multiband combining introduces a delay computed as delay = round(length(num)/2). The numerator coefficients, num, are computed as num = designMultirateFIR(L,M), where L is the interpolation factor and M is the decimation factor.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2021b