Highly Selective Wideband Analysis And Design Of Microstrip Filter

As an important compement in modern wideband wireless communication system, wideband bandpass filters have essential meaning in theory and practical engineering. As a topic in recent years, various wideband bandpass filters have been designed and investigated. Different application background require different performance feature of the filter. With the growing need and the rapid development of personal mobile communication, electronic warfar and satellite communications, wireless communication technology are moving towards high speed and high capacity. As a key component of the transceiver system, filter plays an important role. Especially in the receiver front-end, the performance of bandpass filter will directly affect the whole receiver. Therefore, the items of high performance like miniaturization, low loss, high rejection and good selectivity must be concerned in the design of the wideband bandpass filter. In this paper, multiform high performance wideband bandpass filters are mainly designed and analyzed.Firstly, the history and the development of microwave filters are inrodcued briefly. The current research status in the world is given later.Secondly, after the brief introduction of the multimode resonator theory and the SIR structure, two compact wideband/UWB bandpass filters are designed for UWB system. Different resonators are used to generate multiple transmission zeros and achieve high selectivity.In order to optimize the selectivity of the filter, the transversal signal-interaction concept is used in the design. Simplified circuit model and basic theory are given briefly. Then a wideband bandpass filter and a dual wideband bandpass filter based on transversal signal-interaction concepts are designed to meet different requirements. Besides, multi-mode resonators are also used in the design to realize controllable resonance points and better out-of-band characteristics.For reducing the common mode noise, a differential (balanced) wideband bandpass filter is designed for achieving the desired functions. The differential filter that can only allow the differential-mode signals to pass in certain frequency-range and provide very good common-mode signals rejection, improves ambient noise immunity and increase the dynamic range.All the filters in this paper are fabricated and measured based on the the theoretical design models. Simulation and experimental results are demonstrated and discussed in the following sections.