Embedded Systems and Real-Time Software Development
 

DRX-1

HERON-81 WREN-85

MON-81

RADIO LIB

DRX-1
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DRX-1 DC to 1.0 MHz  VLF Digital Radio Receiver
     
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  The DRX-1 is a PC controlled DC to 1.0 MHz Digital Receiver, designed for the reception of the VLF bands. Application software running on a PC controls the receiver by its RS-232 port.  The receiver is based on a software radio architecture, where the DSP code is loaded from the hard disk of the PC.

The DRX-1 directly samples the RF input signal using a 16-bit sigma-delta analog to digital convertor (ADC).  The ADC feeds a digital down converter (DDC), which tunes the receiver to the required centre frequency and reduces the sample rate by decimation. The DDC feeds the DSP for additional decimation, audio filtering and demodulation.

A powerful 32-bit 180 MFLOPs floating-point DSP (Analog Devices SHARC ADSP-21065L) allows precision FIR filtering with a 100 dB min. filter stopband and linear demodulation minimises distortion products.  Addition filtering of the demodulated audio signal by an adaptive-filter attenuates extraneous background noise, to further improve the clarity of reception.

Decimation reduces the input sample rate to a more useable audio sample rate, where the DSP performs FIR filtering and signal demodulation.

The RF input stage consists of a passive low-pass filter followed by a DC-coupled ADC driver amplifier.

The DRX-1 Digital Receiver is controlled by the RS-232 port of a PC.  The application software runs under Windows 95/98/ME/2000 allows complete control of the Digital Receiver and Demodulation modes.
 

Key Features:

  • 50/600 ohm RF input (1V peak-peak maximum).
  • DC to 1.0 MHz Frequency response.
  • 1 Hz tuning resolution.
  • 2.5 MHz sample rate (high-stability oscillator option available).
  • 100 dB min Filter Stopband and Distortion Products.
  • Clarify Control (-200 Hz to +200 Hz).
  • Direct Speaker Drive.
  • RS-232 Controlled.
  • Windows 95/98/ME/2000 Application Software.
  • Digital Down Converter for RF tuning.
  • Powerful 32-bit Floating-Point DSP for signal demodulation.
  • +12V DC powered

DSP Demodulation Modes:

  • AM.
  • SSB (LSB and USB).
  • CW.

DSP Demodulation Modes:

  • No Filtering (3600 Hz bandwidth).
  • Voice (Wide (300 - 3300 Hz), Normal (300 - 2700 Hz) or Narrow (300 - 2100 Hz)).
  • CW (400 Hz or 800 Hz centre frequency, Wide (200 Hz bandwidth) or Narrow (100 Hz bandwidth)).
  • All Filtering is by linear-phase FIR filters.
 
For optimal operation a RF pre-selector followed by an automatic gain control (AGC) circuit is required to maximise the required signal at the input of the receiver.
 

Block diagram of DRX-1
  Email: sales@trionyxsignal.co.uk
     
Copyright © 2008 by Trionyx Signal Processing.
Last modified: 25/01/2008