ANALYSIS AND DESIGN OF SWITCHED CAPACITOR INTERPOLATORS USING A NOVEL SAMPLING TECHNIQUE

Abstract

unterpolators are used in many switched capacitor filter systems to allow reduction of the complexity of conventional active- RC post filters leading to considerable saving in chip area. It has been found that interpolators suffer from an undesirable distortion which occur due to the sample and hold shaping effect at the lower input sampling rate. An attempt has been made to reduce this distortion. In this dissertation a novel sampling technique [7] is applied to FIR SC interpolators which considerably reduce the spectrum distortion. A generalized design of FIR SC interpolator for various values of interpolating factor has been examined, which is based on - polyphase structures synthesized from the original prototype digital interpolation filter transfer function without any modification. Analysis and design of direct form (DF) and active delayed block (ADB) polyphase structures for FIR interpolators has been exmined from computational point of view. Further simulated amplitude response of the improved FIR SC interpolator has also been obtained and the comparison is carried out between the improved and earlier implementation [2] . The effect of the variation of interpolating factor (L) and the order of the interpolator (N) on the amplitude . response has been stuided by obtaining the simulated amplitude response curves. Software packages "DFINT" and "ADBINT" have been developed using MATLAB for designing and obtaining amplitude response of FIR SC interpolators. Results are presented in Chapter 4, which indicate that spectrum distortion in the given FIR SC interpolator has been relatively reduced [2].