Mobile Radio Audio Processor

  • Full Rx and Tx Filtering to CEPT Standards
  • Digital Control of Volume, Noise Squelch and R.S.S.I.
  • Tx VOGAD Circuitry
  • Serial µP Control of ALL Chip Functions
  • Deviation Limiter
  • Military/Marine and Mobile Radio Applications
  • FM/AM/SSB Applications
  • 16-kbit Data and Voice Scrambler Compatible
  • Low-Power 5-Volt CMOS Process

The FX506 is a µProcessor controlled, single-chip device containing ALL the circuit elements necessary to perform the audio functions of a mobile (or portable) radio system. On-chip signal paths include speech-band/pre-emphasis filters, variable gain/attenuation stages, voice-compression and deviation limiter circuitry. Each function in the signal path can be addressed or by-passed providing “real-time” dynamic control by the µProcessor. This half-duplex device comprises two separate audio signal paths.

The Pre-Process Path performs filtering and level adjustment on audio (RX or TX) for use in auxiliary systems such as “Frequency Inversion Scrambling”, “Sub-Audio” tone or “In-Band” data signalling. This path is output at the “Pre-Process Audio Output” pin. If no external processes are being used this output should be connected to the “Pre-process Audio Input” pin.

The Post-Process Path can adjust and prepare the input audio for output to the chosen transmitter driver or loudspeaker amplifier. Suitably configured, the FX506, which can operate on voice, direct-digital or tone data and sub audio frequencies, is compatible with FM, AM and SSB type transceivers. Digital gain elements are provided on-chip for dynamic control and balance of signal-path levels during manufacturing, test and operation.

System Squelch, a separate path, is sourced from either the incoming signal or Received Signal Strength Indication (R.S.S.I.) from the radio circuitry.

The FX506, a low-power 5-volt CMOS device, is available in 24-pin/lead plastic DIL and SMD package