An oversampling delta-sigma frequency discriminator

A circuit technique for performing oversampled A/D conversion on the phase/frequency information of an angle modulated signal is presented. It is shown that the technique is equivalent to a classic delta-sigma data conversion with instantaneous frequency as the input variable. Details of first and second-order implementations of the technique are presented, and suitability of the technique is discussed for applications such as in the rapidly evolving personal communications field. The most immediate application will be at the IF stage of a receiver where the discriminator input signal is bandlimited by the IF filter, and where sufficient amplification has occurred to provide the input signal levels required by the discriminator