Research And Design Of Microstrip Electronically Reconfigurable Filter

At present, with the rapid development of modern wireless communications, theoccupation of the spectrum is more and more intensive, and spectrum congestion isbecoming prominent. In order to make more efficient use of limited spectrum resources,the spectrum technologies such as spread spectrum, frequency hopping, dynamicfrequency allocation has been widely used. As a key component in these technologies,electronically reconfigurable or tunable filter has attracted more and more attention, andis in great demand. Reconfigurable filters working in transceiver, play a significant rolein controlling the spectrum of proposed signals, eliminating and preventing interferenceof out-of-band noise, supporting multiple information channels.In this paper, the design theory of traditional filter and different implementations ofelectronically reconfigurable filter are introduced. This paper deals with the researchand design of microstrip electronically reconfigurable filter. The major work isconcluded as follows:Firstly, the basic design theory of traditional filter is introduced. After that, asummarization and comparison of different implementations of electronically tunablefilter is made, and PIN diode and varactor diode are selected as the realizations oftunable filter in my work.And then, the resonant characteristic of1/4wavelength stepped-impedanceresonator (SIR) is analyzed. Common1/4wavelength SIR is transformed to net-typeshape, and then the mechanism of reconfiguration is acquired. Based on net-type1/4wavelength SIR, three bits reconfigurable filter is designed. Besides, the resonantcharacteristic of E-shape dual-mode resonator is analyzed, and a dual-band bandpassfilter is designed using this E-shape dual-mode resonator. Based on this dual-bandbandpass filter, a novel switchable bandpass filter with two-state frequency responses isdesigned.Finally, tunable filter with constant absolute bandwidth and reconfigurablebandwidth are investigated. The phenomenon of mode splitting of ring dual-moderesonator is analyzed, and using ring dual-mode resonator to realize bandwidthreconfiguration is proposed. Besides, the key problem in keeping absolute bandwidthconstant is research, and an analytic design method for tunable filter with constantabsolute bandwidth is proposed. In the design process, the proposed filters are simulated, fabricated and measured. Good agreement between the simulated and measured resultsvalidates the design concept.