[Debraj] wrote to us describing a project he recently completed – a simple, compact spectrum analyzer using a 16-bit dsPIC microcontroller.
The analyzer is fed an analog signal, which is passed through a large resistor followed by an opamp. A DC offset is then applied to the signal, after which it is passed through a software-programmable gain amplifier before being fed into the dsPIC’s analog input. A Fast Fourier Transform calculation is done using code provided by the PIC’s manufacturer once 128 samples have been collected. The results are then displayed on the attached LCD in real-time.
If you get a chance, take a look at the video embedded below for a walkthrough and demonstration of his analyzer. [Debraj] says that the analyzer was built to measure harmonics in his home power lines, but for demonstration purposes, he has used a simple function generator instead.