Double-frequency differential band-pass filter based on branch load resonator

Abstract

The invention provides a double-frequency differential band-pass filter based on a branch load resonator. The problems of high insertion loss, low selectivity and inflexible design of a filter are solved. Two opposite quasi-interdigital coupling branch knot load resonators, a stepped impedance microstrip line in three-line interdigital coupling with the quasi-interdigital coupling branch knot loadresonators and U-shaped microstrip lines on the two sides are printed in the middle of the upper surface of a dielectric substrate. The lower surface of the substrate is etched with two linear L-shaped stepped impedance slot lines which rotate 90 degrees counterclockwise. The above structures are all symmetrical about the center of the dielectric substrate. All the structures are symmetrical about the center of the central point of the substrate and are bent by 90 degrees relative to the stepped impedance slot lines, so that the size of the filter is greatly reduced; through quasi-interdigital coupling and three-line interdigital coupling structures, the insertion loss of the filter is reduced and three transmission zeros are formed, so that the selectivity of the filter is enhanced; anda branch knot loaded in the center is in an open circuit mode and a short circuit mode, is independent and adjustable in frequency, meets different requirements, and is used for a radio frequency front end of a wireless communication system.

Description

technical field [0001] The invention belongs to the field of microwave and radio frequency technology, and mainly relates to the structure and design of a bandpass filter, in particular to a dual-frequency differential bandpass filter based on a stub load resonator, which can be applied to a radio frequency front end of a wireless communication system. Background technique [0002] In recent years, with the rapid development of wireless communication technology, filter, as a key frequency selection device, plays an increasingly important role, and its performance often directly affects the quality of the entire communication system. Microstrip bandpass filters are widely used because of their small size, light weight, arbitrary distribution of transmission zeros, and asymmetric suppression characteristics. Since the radio frequency and microwave communication frequency bands are very limited, it is increasingly necessary to expand the high frequency communication frequency b...

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Problems solved by technology

In 2015, Li Yang and other scholars published a paper "Balanced Dual-Band Bandpass Filter With Multiple Transmission Zeros Using Doubly Short-Ended Resonator Coupled Line" in IEEE TRANSACTIONSON MICROWAVE THEORY AND TECHNIQUES journal (VOL.63, NO.7, JULY 2015), proposing A dual-frequency differential bandpass filter based on a double-ended short-circuit resonator is proposed, which realizes three transmission zeros, but the center frequencies of the two passbands of the filter cannot be adjusted independently, and the overall size of the design is large

In 2016, Chu Hui of Nantong University and others invented a dual-frequency differential filter. The authorized announcement number is CN 105762447 B. The multi-layer board is used to achieve a small size, but the structure is complex and the center frequencies of the two passbands of the filter are different. with independent adjustability

In 2018, Jian-Xin Chen and other scholars published a paper "Miniaturized Dual-band Differential Filter Using Dual-mode Dielectric Resonator" in the journal IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS (VOL.28, NO.8, AUGUST2018), proposing a dual-mode Dielectric Resonator based on The dual-frequency differential filter of the mode dielectric resonator can realize independently adjustable frequency, but there is only one transmission zero point between the two frequency bands, and the out-of-band selectivity of the filter is not good enough

[0003] In summary, based on the shortcomings of the existing differential dual-band filters, such as large structure size, large insertion loss, inability to independently adjust the frequency and bandwidth of the two passbands, and low selectivity, we design a compact, low insertion loss, high Selective, independently adjustable center frequency stub-loaded resonator-based dual-band differential bandpass filter, flexible and practical enough for increasingly complex communication systems

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