Duplex Filter Array


The FX304 is a duplex filter array and scrambler.

  • Full Duplex Audio Processing
  • Designed to meet Net-C Cellular Specification
  • On-Chip Audio Bandpass Filters (300-3000Hz)
  • Fixed Frequency Inversion
  • Clear/Invert Facility
  • Output Enable/Disable
  • High Baseband and Carrier Rejection
  • Independent I/P Gain Adjustment
  • On-Chip Clock Oscillator Circuits
  • Crystal Oscillator Stability
  • Single 5V CMOS Process
  • Surface Mount and DIL Package Styles
The FX304 is a duplex filter array and frequency inversion scrambler compatible with the Net-C specification. The two channels, C1 and C2, are identical and independent, each consisting of:
  • A 10th order 3.1 kHz input low pass filter in the 'Invert' path.
  • A balanced modulator providing fixed frequency inversion (3.3 kHz) and having high baseband and carrier rejection.
  • A 14th order bandpass filter (300Hz to 3 kHz).
  • Input Op-Amps in both 'Clear' and 'Invert' paths allowing external components to set input gains, and pre-emphasis or de-emphasis in the 'Clear' path.
  • Clear/ Invert switching causing automatic changeover of signal routes and input circuitry.
  • A buffered low noise output with switching clock filter.
  • An Output Enable switching facility.
Both filter sets meet the Net-C specification and use switched capacitor technology. The common carrier frequency and filter switching clock are generated on-chip using an external 4.433619MHz Xtal or clock input.
Grey ceramic case.