Integrating digital demodulators into OpenWebRX

OData support
Dr. Horváth Péter
Department of Broadband Infocommunications and Electromagnetic Theory

OpenWebRX, a web-based SDR receiver application (the topic of my Bachelor's thesis), is an online communication receiver that supports AM/FM/SSB/CW demodulation, and its web user interface helps accurate tuning with a real-time updated spectrogram of the received band. It allows remote access over the Internet, and multiple users can use it for receiving different signals simultaneously.

Throughout my Master's thesis project, I have added a demodulator for BPSK31, which is commonly used on amateur radio bands today, to the server-side signal processing. The user can select a BPSK31 signal to receive by clicking on the waterfall diagram on the web user interface, and the decoded data appears in the browser afterwards.

The CSDR software package that carries out digital signal processing has been extended with new functions for BPSK31 and RTTY demodulators in a way that it is possible to reuse the same functions for receiving other BPSK and M-FSK modulated signals as well. This work included implementing several fundamental synchronization techniques used in digital demodulators.


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