RF and microwave balun-filter on dual-mode ring or patch resonator

• Main Author: Wan, Chenxin
• Other Authors: Zhu Lei
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/54626
• Institution: Nanyang Technological University

The researches of filter designs have been widely conducted as the filter is a necessary component for signal processing to get rid of noise and obtain the signal with desired frequency band. The filter would be implemented with lumped elements as well as transmission lines. The structure of the circuit and parameter values of these elements determine the type of filter, its bandwidth, order and return level. Balun transformer is also a widely-applied component in signal processing to transform an unbalanced RF signal to balanced signals. It consists of one input port and two output ports that the signals from the two output ports are with equal amplitude and 〖180〗^o phase difference. The balun transformer could be achieved with microstrip lines with several structures. The most common structures are: balun with simple coupled line, balun transformer with coplanar striplines, and Marchand balun. Since the balun transformer is always followed by a bandpass filter and matching network in many applications of RF front-end modules, in order to build a compact RF module to reduce the size of circuit, a balun will be fabricated on a dual-mode ring or patch resonator bandpass filter so that a new component with both the function of filter and the characteristic of balun will be implemented. In this project, a fifth-order balun filter in S-Plane bandpass prototype will be proposed and synthesized. The designed balun filter is with 1 GHz center frequency and 1 GHz bandwidth. The reference frequency is 2.5 GHz and the passband return level is -15 dB. The structure of the circuit will be analyzed and the values of the parameters of each element will be evaluated based on the Chebyshev Response of the bandpass prototype with the application of several theories such as Richards’ Transformation Theory, Kuroda Identities and Element Extraction Technique.