Use of Allpass Networks to tune the Center Frequency of Sigma Delta Modulators
Abstract
Standard sigma-delta modulators use feedback around 1-bit quantizers to transform open loop integrator poles into closed loop transmission zeros of the noise transfer function. The DC transmission zeros permit high resolution quantization of data over a frequency band in their neighborhood. Closed loop zeros can be shifted to arbitrary spectral locations by doubling the number of integrators and then applying local feedback around integrator pairs thereby converting them to resonators. These spectrally shifted zeros support high resolution quantization at the selected (arbitrary) center frequency. In this paper we describe an alternate technique for shifting the open loop poles around the unit circle. In this method, rather than forming resonators, we use a spectral transformation on the baseband process performed by imbedded all-pass filters. Analog to digital filters, Low-power filter, Digital filter.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1993
- Accession Number
- ADA279337
Entities
People
- Bill Mcknight
- Bob Caulfield
- Fred Harris
Organizations
- Naval Command, Control and Ocean Surveillance Center