Novel approach

摘要

A RadCom reader has developed a software defined radio technique that can potentially demodulate CW, SSB, DSB, AM, FM and DEM. Steve Ireland and Phil Harmon report. The two SDRs we have looked at to date, the FlexRadio SDR-1000 and the SoftRock series, have adopted the principle of using hardware to convert a fairly broad (up to 96kHz) slice of the radio spectrum straight into the digital domain, in what is effectively a wide-band direct-conversion receiver. This approach allows software to process the whole of this slice at once - for example, to produce a bandscope-type display - but for best results a high-performance soundcard is needed for the analogue to digital conversion and it's not easy to maintain amplitude and phase balance in the hardware over the whole 96kHz slice. While the FlexRadio/SoftRock approach to SDR may be the way ahead for the future, such a wide slice of spectrum can mean that, at least in the medium term, it can be difficult to handle strong unwanted signals using this approach.