ECE422 Software Defined Radio Kit Information

Background Information

Over the course of the semester in ECE422, you will construct a software-defined radio (SDR) kit that you can use with a PC to receive signals in the high frequency (HF) band from 4-8 MHz. The radio can be constructed and analyzed by following a series of modules outlined on this page. These modules can be completed using your own time, lab time in ECE422 (PRA sessions), or a combination thereof. All scheduled PRA sessions for the course where there are not predefined lab experiments (there are 3 such experiments in ECE422) can be potentially used for this purpose. In addition to the kits, a PC running Windows will be required to run the SDR software. This computer can be your own personal machine, and/or the network analyzers in the GB347 lab, which run Windows.

The software defined radio (SDR) kit is based on the "RX Ensemble" radio kit available from Five Dash Inc., which is a multi-band high frequency HF radio receiver. Unlike the RX Ensemble, which is a switched-band design which allows coverage from 1.8 MHz through 30 MHz, the kit is simplified single-band variation that covers 4-8 MHz. Detailed and very useful assembly information can be found here, bearing in mind that the kit has been modified. Therefore, use that link for general assembly information but follow the modules below in detail to determine how and what to populate on the SDR kit board.

Overview

A block diagram of the RX-III receiver is shown below. Each block in the diagram is covered by a separate module.

The signal in the receiver originates from the antenna. After passing through a bandpass filter the signal is applied to a quadrature sampling detector (QSD), which downconverts the signal from the carrier frequency to a near zero intermediate frequency (IF) essentially at baseband. The QSD derives its oscillator from a PC-controlled frequency synthesizer and subsequent frequency divider to produce two local oscillator signals 90 degrees out of phase. The output of the QSD is low pass filtered and amplified to produce the in-phase (I) and quadrature (Q) components of the received signals, before they are finally sampled by analog to digital converters (ADCs) in the soundcard of the PC. The SDR circuit, soundcard, and PC form the SDR receiver which runs specialized software radio software for demodulating the signal from the I/Q signals. From there, you can either listen to the signals or perform digital decoding in the case of digital transmission modes.

Note on the Modules

The modules are written in Jupyter notebook format. This allows for the embedding of certain elements in the notebook such as interactive graphs, and computer code. The computer code used is Python, which in turn makes use of the numerical libraries NumPy and SciPy. While you do not need to concern yourself with understanding the code, those with an interest can use this code on their own if they want to try doing the analysis on their own. The code is also largely compatible with MATLAB, and can be used as a basis for doing the same calculations in that tool, if desired.

The complete set of modules are listed below. The modules have been grouped into sets A, B, C, and D. Each module group can be completed independently of the others, so you can work on the modules in any order you like. The exceptions are Module Sets D and E, which can only be completed once Module Sets A-C are completed. Within each Module Set, you should complete the modules in the order listed. This is because modules further in the set depend on the previous ones.

Modules

Module Set A: Antenna

Module Set B: Receiver front end

Module Set C: Local Oscillator

Module Set D: Detector

Module Set E: Using the SDR

Additional Information