Abstract — We illustrate the idea of the building delta modulator/demodulator with the help of the non-uniform sampling method. Each of element, both analog and digital, that is used for this realization can be put together on one chip, making up a piece of the System on Chip circuit or the ASIC chip dedicated to special purpose, such as: measuring, communication, control systems, data compression, data encryption wireless telecommunication. The Adaptive Non-uniform Sampling Delta Modulators (ANS-DM) modulation algorithm implementations, and the codec architecture are described in the paper also. We present a comparative study of integrated CMOS continuous time (CT) analog filters dedicated for speech codecs with adaptive non-uniform sampling. Five CMOS implementations of this block have been studied, four of them fabricated in 0.35 m CMOS technology. The system considerations and simulation results are shown. Keywords — adaptive delta modulation, CMOS circuits, switched-capacitor filters, continuous time filters, anti-aliasing filters, non-uniform sampling, speech codecs. I. INTRODUCTION HE investigation aimed at the improvement of analog to digital conversion efficiency prove that not all potential possibilities of delta modulation analog signal processing have been fully utilized, so far [1]. The concept of using adaptive sampling to reduce the data rate of source coding is very promising theme, however studied only fragmentarily [2]. The investigation aimed at the improvement of analog to digital conversion efficiency prove that not all potential possibilities of delta modulation analog signal processing have been fully utilized, so far [1]. The concept of using adaptive sampling to reduce the data rate of source coding is very promising theme, however studied only fragmentarily [2]. The long-term research works [1, 3, 4] allow to affirm, that reaching high accuracy and large noise immunity in wide dynamic range, with use of the uniform sampling ADM converters, is not possible. Therefore we propose use of the 2 – parameters, 1-bit PCM differential modulation, which in fact depends on application of adaptation of both the step size and sampling interval. The results of simulating works proved that for nonstationary sources, the adaptive sampling delta converters expose higher coding efficiency than the former proposals, based on uniform sampling methods. Classification and evaluation of the ADM converters solutions presented in the works [4, 5], including conceptual studies, enabled construction of the adaptive sampling converters (NS-DM and ANS- DM) prototype circuits. The studies of the solutions proved that, at present, fully efficient hardware implementation of adaptive sampling delta converters conception on the base of microprocessor standard chips, is possible. The work was aimed at elaboration of analyze methods and performance evaluation of the filters for delta systems with step size and sampling rate adaptation. It comprised the studies of mathematical description, computer simulations, and design methodology, as well as proposal of electronic circuits implementation. Within analytical part, the method of description of the performances of the filters for adaptive sampling delta converters has been worked out. The method of design of the filters architecture was proposed. In simulating investigations, performance of the filters were analyzed. The unique approach to this investigations enabled comprehensive comparison of former and new solutions. Each practical design must be done in specific technology, so initially our choice was an 2P4M 0.35m CMOS technology from austriamicrosystems (AMS), and all the presented simulation/measurements are done for this specific silicon foundry. However the circuit solutions are transferable into more advanced technology node (e.g. 180nm CMOS from United Microelectronics Corporation) with improved elements – especially capacitors which have significantly lower parasitics. NMOS and PMOS transistors for AMS 0.35 technology have threshold voltages varying between -0.68 ÷ -0.72 Volt and 0.46 ÷ 0.59 Volt, respectively. In the framework of our project we investigated 5 different filters, 4 of them were manufactured as a part of four test chips. II. PRINCIPLE OF THE ANS-DM MODULATIONS A. Functional diagram and algorithm of the ANS-DM modulations The ANS-DM is a modulation, where both coder parameter’s: the step size and the sampling instant are adopted. Changes of the input signal level cause adequate a sampling frequency and a step size adaptation (Fig.1). This Filter implementation for CMOS adaptive sampling Delta Modulators R. Golanski, J. Godek, J. Kolodziej, W. Machowski, S. Kuta, Department of Electronics, AGH-UST University of Science and Technology, Krakow, POLAND {golanski,godek,jackolo,machowsk,skuta}@agh.edu.pl T INTERNATIONAL JOURNAL OF CIRCUITS, SYSTEMS AND SIGNAL PROCESSING Issue 2, Volume 5, 2011 159