Demodulating Over-the-Air Communications

Today, modern radio designs have made a predominant shift to the software-defined radio architecture. From cellular handsets to military communications devices, the flexibility to use multiple wireless standards with a common RF front end is a compelling benefit. While the architecture of a software-defined radio is well understood, the inner workings are often not. In this article, we will explain how the software-defined radio architecture can be used to demodulate an unknown over-the-air signal. In this case, we will use a software-defined PXI RF vector signal analyzer from National Instruments to prototype the software-defined radio. By understanding basic radio hardware and software fundamentals, even the novice engineer should be able to demodulate over-the-air transmissions.