Differential Radio Frequency Passive Filters

Abstract

This thesis aims to introduce differential circuits and methods for common mode suppression as well as introducing equivalent circuit models for different bi-layer planar transmission lines. Bi-layer transmission lines are widely used in the design of various passive microwave components including differential components. This thesis aims to facilitate the design of differential filters through the development of wideband circuit models. Such circuit models can be used to reach the optimum design, thus avoiding the time-consuming and computationally expensive electromagnetic (EM) simulations. These circuit models are based on the multimode cross-junction model which was previously employed in the modelling and design of several microwave components. The derived circuit models are then used to design a balanced Composite Right Left-Handed (CRLH) transmission line with high common mode rejection ratio (CMRR). The CRLH transmission line, in addition to its bandpass filtering response, has numerous applications in microwave circuits deign. The thesis is divided into five chapters as listed below: Chapter 1: This chapter introduces the background, motivation, objectives, major contributions and organization of the thesis. Chapter 2: This chapter reviews the theory of differential microwave components and their advantages. It emphasizes the need for common mode noise suppression and compares various techniques for common mode suppression in differential transmission lines. It also includes a literature survey on the differential filters emphasizing the structures which employs hybrid microstrip /slotline structures .