DIGITAL RADIO

DRX-1 Digital Radio Receiver

The DRX-1 is a DC to 1.0 MHz digital radio receiver. The DRX-1 directly samples the RF input signal using a 16-bit 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.

ULF/VLF Convertor

The ULF/VLF convertor, accepts a ULF/VLF input from an antenna and upconvertors the signal to 4.0 MHz, where is its received on a conventional HF Receiver. The input impedance is 50 ohm and the input bandwidth is 10 Hz to 300 kHz, to cover the ULF and VLF bands. The convertor is based on a double-balance diode-ring mixer for exceptional signal performance.
The ULF/VLF Convertor is supplied with documentation and example applications.

SHARC DSP Radio Library

A set of DSP Radio Library functions implemented on the SHARC ADSP-2106x, which performs DSP demodulation on baseband IQ components and FIR Filtering operations on audio and speech signals. The filtering is aimed at filtering the demodulated audio (e.g. from short-wave receivers) to improve the clarity of reception. Different filtering modes are aimed at Speech (Single Side Band, SSB, NBFM), Music (Amplitude Modulation, AM), Morse Code (Continuous Wave, CW) and Data (AM). The 32-bit floating-point DSP allows filtering with a -100 dB minimum stopband, a figure unobtainable from 16-bit fixed-point DSPs.
The DSP Radio Library is supplied with documentation and DSP example code. The full DSP source code is available.