MATLAB Examples

FM Stereo Receiver Using Analog Devices AD9361/AD9364

This model shows how to use the Xilinx® Zynq-Based Radio Support Package with Simulink® to build an FM Stereo receiver. The receiver receives and demodulates the FM signal transmitted by the stereo FM broadcast radio.

Refer to the Getting Started documentation for details on configuring your host computer to work with the Support Package for Xilinx® Zynq-Based Radio.

Contents

Introduction

Xilinx Zynq-Based SDR hardware along with Analog Devices™ AD9361/AD9364 is required for running the model. The model configures the SDR hardware to receive stereo FM signal over the air. It plays the left and right channels.

Structure of the Example

The top level structure of the FM Mono receiver model is shown in the figure below:

In this example, the radio baseband data is received from the SDR Hardware via a Zynq® SDR Receiver block ZC706 and FMCOMMS2/3/4 Receiver. The Zynq SDR receiver block is configured at a sampling rate of 960 kHz using the Baseband sample rate parameter in the Zynq SDR Receiver block.

To perform stereo decoding, the FM Broadcast Demodulator Baseband block uses a peaking filter which picks out the 19 kHz pilot tone from which the 38 kHz carrier is created. Using the obtained carrier signal, the block downconverts the L-R signal, centered at 38 kHz, to baseband. Afterwards, the L-R and L+R signals pass through a 75 microsecond deemphasis filter . The FM Broadcast Demodulator Baseband block separates the L and R signals and converts them to the 48 kHz audio signal

Running the Example

The SDR hardware is configured to use input ports for the RF center frequency. Using input ports for these parameters allows them to be updated while the model is running. The center frequency can be configured to a local FM radio station using the Slider Gain block. Set the center frequency to a local FM radio station and start the model. This tunes the SDR device to the local FM station and you can listen to the radio station through the audio device connected to your computer. Change the center frequency to listen to a different station.

If you hear some dropouts or delay in the sound, run the model in Accelerator mode. From the model menu, select Simulation->Accelerator, then click the run button.

Troubleshooting the Example

If the received signal is very weak, you can try increasing the receiver gain by changing the Source of gain variable to Input port for the manual gain control mode or by changing it to 'AGC Fast Attack' or 'AGC Slow Attack'.

If you run the example as described but fail to see a signal like the one shown (e.g. you only receive noise or the spectrum display is never updated), see Xilinx FPGA-Based Radio Processing Errors and Fixes.

References