Over on his blog Lukas Lao Beyer has uploaded a post that shows his journey with designing and building a software defined radio from scratch. Lukas’ finished SDR design is called the FreeSRP and is based on the Analog Deviced AD9364 transceiver and a Xlinx FPGA.
In his post Lukas describes how he designed the PCB with Altium Designer, routing the traces carefully to ensure the shortest path was used, and to ensure impedance matching was correct. Then after producing the PCB’s with OSH park he writes how he assembled the board by carefully placing the components down by hand and using his reflow oven. This was no easy task due to the manual nature of the operation and the high possibility for undetectable solder problems to arise. Despite the difficulties he found that the SDR powered up as expected.
His next steps were to start work on the FPGA controller design, however he discovered that he had failed to properly route some clock pins on the FPGA. On his third revision of the PCB he was able to fix this. Finally he was able to program the FPGA and get his SDR to work.
Designing an SDR from scratch is no easy task, especially if you have little design experience like Lukas did. However, in the end despite some mistakes he was able to build a working SDR that interfaces with GNU Radio.