Reliable analog bandpass signal generation

A novel method for generating bandpass type signals is introduced. A phase function is turned into a jittery bandpass signal using a delta-sigma modulator and digital phase modulation. This signal can be used to verify the correct operation of a charge-pump phase-locked loop. After validation of this circuit, more complex communication signals such as GMSK may be generated for test purposes. As all components are digital or may be tested digitally, this scheme is amenable to built-in self-test.