Fourier transform and signal processing (part 1)

As a radioamateur I am interested in SDR which stands for Software Defined Radio. While SDR as a term seems to be pretty self explanatory, my interest is to make a radio with as less hardware as possible and in the same time provide most of the radio functions in software. This will allow an easily customization of the supported waveforms, demodulation types, etc while also providing a low cost solution that can be improved step by step to beat the existing classic solutions.

Since discussing about SDR and even making progress in this domain is quite a challenge, some knowledge about signal processing needs to be gathered in order to be able to pursue such a great domain. Therefore I thought making small projects having clear goals and objectives will lead step by step to define a good architecture of my SDR.

SDR uses a lot of computational effort to modulate/demodulate radio signal in the digital domain and for that reason an ADC/DAC is the first hardware one should have for that job. There are many constraints about the perfect suitable ADC/DAC but I will be discussing it later in a chapter devoted to SDR types. However, what I want to bring into discussion is the sound card available in every PC nowadays, a piece of hardware that has ADC and DACs ready to be used at moderate sample rate.

Therefore, the first accommodation project would be one to understand how to access the sound card to record/play audio samples and control the various available configuration parameters.

Since I’m a big fan of Linux, open source and especially Linux kernel, all the work I’ve done is on Linux OS. This will allow a great level of customization for my projects and also will speed-up development by using various tools ready available and provided by the OSS community.

What could be a starting project involving sound processing and audio card as ADC/DAC? Remember it should be something usable and with clear goals. So it is a RLC meter.

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