Electrically tunable four-passband filter based on double layered resonator

Abstract

The invention discloses an electrically tunable four-passband filter based on a double layered resonator, and mainly solves the problems that the number of passbands of a traditional electrically tunable filter is small, adjustable passband bandwidth is not constant, the out-of-band rejection degree is poor and the volume is large. The electrically tunable four-passband filter based on the double layered resonator includes a pair of parallel coupling feeder lines (1) and a pair of adjustable stepped impedance resonators (2, 3) which are arranged on an upper microstrip medium substrate (7), and a branch loading resonator (4) and two direct current biasing circuits (5, 6) which are arranged on a lower microstrip medium substrate (8), wherein the two direct current biasing circuits (5, 6) are connected to two ends of the adjustable stepped impedance resonators (2) and (3), thereby realizing continuously adjustability of a third passband and a fourth passband, and the branch loading resonator (4) realizes fixing of a first passband and a second passband. The electrically tunable four-passband filter based on the double layered resonator is small in size and high in out-of-band rejection degree, can realize four passbands, realizes continuous adjustability of the third passband and the fourth passband under the condition that the bandwidth is basically maintained unchanged, and can be used for a wireless communication system.

Description

technical field [0001] The invention belongs to the technical field of microwave devices, in particular to a microstrip electrically adjustable four-pass band filter, which can be used for a radio frequency front end of a wireless communication system. Background technique [0002] With the rapid development of modern communication technology, the contradiction of spectrum resource congestion has become increasingly prominent. In order to efficiently utilize limited spectrum resources, it is usually required that the RF front-end, such as filters, have the characteristics of fast tuning. The electric tuning filter changes the capacitance value of the varactor diode by controlling the DC bias voltage, thereby changing the resonant frequency and realizing fast switching at different operating frequencies. In addition, in order to achieve different service requirements in multiple frequency bands, the wireless communication system needs to use filters to select in-band working...

AI Technical Summary

Problems solved by technology

The current electronically tuned filters are mainly concentrated in the fields of single passband and double passband, and the three-passband or even four-passband electronically tuned filters are more difficult to implement due to their complex structure.

[0003] In January 2009, E.E.Djoumessi et al. published "Varactor-tuned quarter-wavelength dual-bandpass filter" in the IET Microwave Antennas Propagation journal (Vol.3, no.1, pp.117–124, 2009), proposing an electronic Adjustable dual-passband microstrip filter, the filter can realize the continuous electric adjustment of two passbands, but it is difficult to extend the structure to more passbands; in 2009, Ko-Wen Hsu et al. .1041-1044, 2009.) published "Design of a Novel Four-Band Microstrip Bandpass Filters using Double Layered substrate", and proposed a four-band microstrip filter based on a double-layer structure, which can realize Four passbands, but cannot achieve fast adjustable frequency

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