Continuous electrically tunable band-pass filter

Abstract

A continuous electrically tunable band-pass filter disclosed by the invention has the advantages of low in-band insertion loss, high out-of-band rejection, continuously adjustable center frequency and excellent standing wave performance. The filter comprises a metal ground carrier plate, an upper dielectric substrate, a lower dielectric substrate, and three rectangular substrate integrated waveguide resonant cavities are formed by two layers of vertically overlapped dielectric substrates and metalized through hole arrays. A liquid crystal material is filled in the rectangular hollow area of the lower dielectric substrate in the middle of the substrate integrated waveguide resonant cavity and is sealed through the bottom metal ground carrier plate. The whole filter structure is installed on the metal ground carrier plate through vertical overlapping conductive bonding, an external electric field is applied, the liquid crystal material is modulated through a bias circuit embedded in a liquid crystal substrate integrated waveguide resonant cavity, and signal transmission energy coupling is achieved through an inductive metal window. Therefore, the continuous frequency adjustable characteristic of the band-pass filter of the three-order substrate integrated waveguide resonant cavity is realized.

Description

technical field [0001] The invention relates to a continuously adjustable band-pass filter with center frequency which is suitable for radio frequency microwave communication system and can be widely used in the front end of the radio frequency communication system. Background technique [0002] A filter is a two-port network with frequency selective properties. At present, in radar and microwave communications, multi-frequency work is more and more common, and the requirements for frequency separation are also increased accordingly. The system requires filters to have high Q values ​​and wide adjustable bandwidths, and the deterioration of passband performance is small. . It is not possible to completely attenuate all frequencies outside the desired frequency range, especially there is an attenuated but not isolated range outside the desired passband, which is usually called the roll-off phenomenon of the filter. As the roll-off range gets smaller and smaller, the passban...

AI Technical Summary

Problems solved by technology

However, because the direction of the short-circuit end is constantly changing, the grounding of the interdigital filter is a difficult point

The substrate-integrated waveguide structure is equivalent to a dielectric-filled metal waveguide. The particularity of its metallized through-holes will cause inherent short-circuit characteristics when applied to liquid crystal electric tuning filters, resulting in device function failure.

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