Car radio digital signal processor

DSP radio system

The Digital Signal Processing (DSP) radio system (see Fig.1) consists of:

• Analog tuner (also called RF/IF)
• SAA7724H
• Audio power amplifier
• Microcontroller
• IF co-processor
• Audio co-processor.

The microcontroller interfaces to the RF/IF and SAA7724H via an I²C-bus. Analog tape and CD inputs are input from other parts of the radio. The IF co-processor and audio co-processor interfaces to the SAA7724H via an I²S-bus.

SAA7724H

The SAA7724H digitizes up to two IF signals and performs DSP to generate left front, right front, left rear, and right rear audio and RDS/RBDS data output. The SAA7724H also samples analog baseband tape, FM MPX, AUX inputs, analog and digital CD, performs signal processing on these sampled waveforms and multiplexes the proper signal to the output. A microcontroller interface allows the SAA7724H to be controlled and monitored.

The SAA7724H is composed of hardwired and programmable DSP circuitry, with programmable parameters, such as injection frequencies, filter coefficients and control parameters. Some functions or groups of functions are implemented with programmable sequence processors.