Adjustable filter with stable wide stop band

Abstract

The invention discloses an adjustable filter with a stable wide stop band, which solves the technical problem that in the prior art, an upper stop band is not stable enough as the harmonic frequency links along with a fundamental wave passband when the filter is designed. The adjustable filter with the stable wide stop band primarily comprises two phase step impedance resonators (SIR) which separately load varactors Cv11 and Cv12, a pair of feeders and two varactors Cv21 and Cv22 connected to the resonators and the feeders, wherein the varactors Cv11 and Cv12 loaded to zero points of the spread voltages of the lowest subharmonic (third harmonic) radio frequency are used for adjusting the fundamental frequency and meanwhile, the third harmonic frequency does not link and tune along with fundamental frequency, so that the stable distance between the fundamental waves and the harmonic waves is stable. The adjustable filter optimizes the characteristic parameters of SIR on the premise of stabilizing the upper stop band, so that the frequency tuning range of the fundamental wave passband is expanded, and the performance index can meet the application demand of microwave frequency band.

Description

technical field [0001] The invention relates to the technical field of radio frequency communication, in particular to an adjustable filter with a stable wide stop band. Background technique [0002] With the rapid development of wireless communication technology, reconfigurable / tunable microwave components have attracted great attention from scholars. As an important frequency selective element, tunable bandpass filter has been widely studied for its advantages of reducing system size, cost and complexity. In the past, various frequency tuning techniques such as MEMS, ferroelectrics, piezoelectric actuators, varactor diodes, and microfluidics have been used to study tunable filters. The filter based on the planar transmission line (such as microstrip) loaded varactor has the advantages of small size, fast tuning speed and low cost in use, and is popular in the design of tunable filters. [0003] In recent years, most tunable filters load a varactor diode to the open end o...

AI Technical Summary

Problems solved by technology

[0003] In recent years, most tunable filters load a varactor diode to the open end of a quarter-wavelength (λ / 4) uniform impedance resonator (UIR) or stepped impedance resonator (SIR) for analysis to obtain the maximum frequency However, the tunable filter with this structure does not take into account that its harmonic frequency will be linked with the fundamental passband, which will cause the problem that the upper stopband is not stable enough, so it cannot meet the diverse wireless communication needs.

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