The Nth order and three level delta modulation

Two delta modulation (DM) systems are presented which provide a higher signal to noise ratios(SNR) than conventional DM, at the price of an increase in complexity. Nth order DM, which transmits the filtered error signal of one DM using a second DM, was shown to provide a substantial increase in SNR over ordinary DM while using the same clock rate. Expressions and curves for the optimum value of N as a function of the bandwidth expansion ratio, the improvement in SNR as a function of N, and the dynamic range of the system are given. An analysis of the performance of the system over an additive noise channel is given, which predicts an increase in threshold of a few db over N = 1. The analytical results are supported by experimental measurements and simulations. Three level DM is a system only slightly more complicated than conventional DM which can provide an improvement in SNR of close to 6 db. An analysis of the theoretical improvement in SNR, and the performance of this system on the additive noise channel is given. Analog/hybrid and digital computer simulation results are presented.