Capture Over-the-Air Signals

You can use the SoC Blockset™ Support Package for AMD FPGA and SoC Devices together with a supported SDR device to capture over-the-air signals to the MATLAB^® workspace.

Capture RF Data to Baseband File Using Analog Devices AD9361/AD9364

Record RF signals for post-capture processing in MATLAB®. Save an FM broadcast signal to a file as baseband samples. Read the file containing the recorded signal and demodulate the baseband samples.

Configure SDR Hardware

If your radio hardware is already configured for host-radio communication, skip this section. To configure your radio hardware for host-radio communication, follow the steps in the Set Up Xilinx Devices. Attach an antenna suitable for the 88–108 MHz band to the first RX channel.

Configure Receiver System Object

Create a receiver System object with the specified properties. The specified center frequency corresponds to a local FM station. If you have an FMCOMMS5 radio hardware, set deviceName to 'FMCOMMS5'.

stationCenterFrequency = 95e6;
deviceName = 'AD936x';
rx = sdrrx(deviceName,'BasebandSampleRate',528e3,...
    'CenterFrequency',stationCenterFrequency,'OutputDataType','Double');

Initiate Data Capture to File

Call the capture function, specifying the receiver object, a capture duration, and a file name. The function returns the captured data in a file named "FMRecording.bb". After capturing the FM signal, unlock the receiver object by using the release function.

capture(rx,5,'Seconds','Filename','FMRecording.bb');

## Establishing connection to hardware. This process can take several seconds.

release(rx);

Demodulate FM Recording

Create a comm.BasebandFileReader (Communications Toolbox) System object to read the captured signal and extract frames of data from the file. Set the baseband file reader to take 4400 samples per frame when reading the saved baseband signal.

bbr = comm.BasebandFileReader('FMRecording.bb');
bbr.SamplesPerFrame = 4400;

Use the BasebandSampleRate field of the baseband file reader object to set the SampleRate property of the demodulator. You can find the BasebandSampleRate field in the MetaData structure. Create a comm.FMBroadcastDemodulator (Communications Toolbox) System object. Demodulate and play back each frame of the FM data. Use a while loop to read all frames of the captured data.

fmbDemod = comm.FMBroadcastDemodulator( ...
    'AudioSampleRate', 48e3, ...
    'SampleRate',bbr.Metadata.BasebandSampleRate,'PlaySound',true);

while ~isDone(bbr)
    fmbDemod(bbr());
end