An electronic system with real-time fault detection is provided. In one embodiment, the system includes analog circuitry, having a first input coupled to receive an input signal and a second input coupled to receive a test signal. The test signal is at an edge of a selected band that contains the input signal. The test signal is used to identify faults in the electronic system during operation of the electronic system. The electronic system further includes an analog to digital (A/D) converter coupled to an output of the analog circuitry. The A/D converter generates digitized spectrum. Digital circuitry is coupled to the output of the A/D converter. The digital circuitry processes the input signal from the band to provide an output for the system and processes the test signal to detect faults in the analog circuitry, the digital circuitry and the A/D converter.