Baseband File Reader

Read baseband signals from file

• 

Libraries:
Communications Toolbox / Comm Sources

Description

The Baseband File Reader block reads a signal from a baseband file. A baseband file is a specific type of binary file written by the Baseband File Writer block. Baseband signals are typically downconverted from a nonzero center frequency to 0 Hz. The block automatically reads the sample rate, center frequency, number of channels, and any descriptive data.

Examples

Write Baseband Signal to File in Simulink

Generate and write a QPSK-modulated signal to a file. Then, read the file and plot the constellation diagram of the signal.

The model cm_baseband_writer_ex1 generates a QPSK-modulated signal and writes the noisy QPSK signal to a file named bbw_example.bb.

Open a second model, cm_baseband_writer_ex2, to read the signal from the file and display the constellation diagram.

Read Baseband Signal from File in Simulink

Read the baseband signal from the saved file example.bb.

The baseband_samples_1ghz.bb file contains 10,000 samples having a sample rate of 1 Hz. The simulation stop time for the model is set to 12,000. The Baseband File Reader block configuration has Inherit sample time from file enabled, Samples per frame set to 100, and Repeatedly read the file disabled. As a result, the simulation time exceeds the amount of saved data and the last 2000 samples are zero padded.

The Baseband File Reader block configuration is modified to enable the Repeatedly read the file parameter. Now, when the model runs, after 10,000 s, the file is read again so the samples from 10,000 to 12,000 s are a repeat of the first 2000 samples.

Ports

Output

Data — Baseband signal

scalar | vector | matrix

Baseband signal, returned as a scalar, vector, or matrix. The signal is read from the file specified by the Baseband file name parameter. The sample time is either inherited from the file or can be set by the Sample Time (s) parameter.

Data Types: double
Complex Number Support: Yes

EOF — End-of-file indicator

logical scalar

End-of-file indicator, returned as a logical scalar. The output is true when the Repeatedly read the file parameter is false and the entire file has been read. To enable this port, select the Output end-of-file indicator parameter.

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.

Baseband file name — Name of baseband file to read

example.bb (default) | character vector

Name of the baseband file to read, specified as a string scalar or character vector.

• Click Browse to locate the baseband file you want to read.

• Click File Info to display this information:

  • File name, including absolute path

  • Sample rate

  • Center frequency

  • Number of samples

  • Number of channels

  • Data type

  • Any metadata fields

    • • If the file has no descriptive data, this property is an empty structure.

      • If the baseband file writer defined the object with a function call, the bb-file stores that function call. The baseband file reader executes the function call to display the object.

        • If you are licensed to use the software associated with that feature, the metadata output contains the object contents.

        • If you are not licensed to use the software associated with that feature, the metadata output contains the string rather than the object contents.

Inherit sample time from file — Select source of sample time

on (default) | off

Select this check box to inherit the sample time from the file specified by Baseband file name.

Sample time (s) — Block sample time

1 (default) | positive scalar

Specify the block sample time in seconds as a positive scalar. To enable this parameter, clear the Inherit sample time from file check box.

Samples per frame — Number of samples per output frame

100 (default) | positive integer scalar

Number of samples per output frame, specified as a positive integer or inf. When this parameter is inf, the output frame contains all of the samples in the baseband file.

Repeatedly read the file — Continuously loop data from file

off (default) | on

Select this check box to repeatedly read the contents of the baseband file. When the end of the file is reached:

• The block outputs zeros, if the Repeatedly read the file parameter is not selected (off).

• The block outputs samples from the beginning of the file, if the Repeatedly read the file parameter is selected (on).

Simulate using — Type of simulation to run

Code generation (default) | Interpreted execution

Type of simulation to run, specified as Code generation or Interpreted execution.

• Code generation — Simulate the model by using generated C code. The first time you run a simulation, Simulink generates C code for the block. The model reuses the C code for subsequent simulations unless the model changes. This option requires additional startup time, but the speed of the subsequent simulations is faster than with the Interpreted execution option.

• Interpreted execution — Simulate the model by using the MATLAB^® interpreter. This option shortens startup time, but the speed of subsequent simulations is slower than with the Code generation option. In this mode, you can debug the source code of the block.

For more information, see Interpreted Execution vs. Code Generation (Simulink).

Block Characteristics

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

Extended Capabilities

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

Version History

Introduced in R2016b

R2024a: Support reading objects from metadata

The Baseband File Reader block now supports reading objects and structures-of-structures from the saved metadata.