DSPRX - Signalprocessing for SSB - Direct Conversion Receiver using Phasemethod for Sideband Supression

by Michael Keller, DL6iAK

DSPRX does all necessary signalprocessing for Direct conversion Receivers using IQ-mixer for demodulation. I and Q signal is fed into right/left channel of the soundcard. The 90° phaseshifting is done by the PC. Sidebandsupression is done by adding or subtracting the shifted and unshifted signalcomponents. The program allows when using a sampling rate of 48kHz a +/- 24kHz tuning range. When using a 7040.00kHz crystal (LXO) you can tune from 7016.0kHz to 7064.0kHz. There is nomore problem with shifting a crystal, all is done by the signal processing in the PC. An Athlon 1000 and a soundcard allowing 100kHz sampling rate will give you 100kHz tuning range out of a fixed crystal local oszilator. The spectral display will show the frequencies centered arround the used LO. Tuning is done by moving the tune trackbar. The red lines will show the filter range. The bandwidth of the filters can be changed on the fly by moving the trackbars. Used XO-frequency can be set in the dspr.ini file. The sampling rate in this version is fixed to 32kHz. I will release a version, where you can set sampling rate up to 48kHz, if your computer is able to do this job at that rate. 32kHz will run on a 500MHz AMD. Amplitude balance and constant time delay between right/left channel can be trimmed. I run a very simple IQ-demodulator for 7040.0 kHz using two NE612 as IQ-Mixers.

Block diagram of DSPRX

The programm will be soon improved for transmitting purpose, so it can be used for simple direct conversion transceivers.

The program is free for all non commercial purposes. I do not know, how the program is working on different hardware, just try it on your own risk.

Download dsprx.zip (207 KB)