Experiments on DSP

Today DSP technology has been incorporated into many amateur radio equipments. I want to make some experiments by myself on DSP.

Current Goal

While DSP has wide-range applications, I begin experiment on subjects such as filtering, demodulation and generation of SSB/CW/AM signals.

Hardware/Software environment

When an amateur trys to play with DSP one can purchase an evaluation board from various manufacturers such as TI, Analog Devices, Motorola etc. They are available from $100 price range.

Another approach is to use a PC soundcard. Recenctly many amateur radio application software have been developed for soundcards. Those include audio spectrum analyzers, audio filters and MOD/DEMOD software for SSTV/RTTY/PSK31 etc.

I decided to use a soundcard. It can handle audio frequency only, but many of low cost DSP evaluation boards are also restricted to AF. It also have merits. Because processing is done by PC's main CPU, you don't need to learn new programming environment and floating point calculation is available unlike some low-end DSP chips . The sound chip in my PC is CS4614 by Crystal Semiconductor. Its maximum sampling rate is 48kHz (16bit) and it has full-duplex capability.

I chose Linux and g++ compiler as programming environment. The sound driver is ALSA. Recently I began writing codes also in Java, so some of my prorams run on MS-Windows , too.

Besides those programing environment, tools are needed to design digital filters and other functional elements. Many commercial and non-commercial ones may be availble, but I don't know well about them. Currently I'm using Java applets which I found on a web site to design FIR filters.

Current Experiments