FM signal generation using delta-sigma oscillators

A frequency modulation signal generator based on delta-sigma oscillators is presented. The signal, mixed with out-of-band quantization noise, is encoded in a single bit stream. The design is entirely digital except for a 1-bit DAC. It therefore exhibits many digital circuit qualities such as programmability, accuracy, low sensitivity to process variations and mature testing methods. It is more efficient in terms of silicon area than other digital synthesis methods as it does not require a ROM or a multiplier. While the carrier frequency is fixed to a quarter of the clock frequency, this generator allows a wide range of modulated signal frequency and modulation index. It can be used as a stimulus for built-in self-test of wireless communication systems.