Adjustable bandwidth type ultra-wide-band band-pass filter based on parallel coupling line loading

Abstract

The invention discloses a novel adjustable bandwidth type ultra-wide-band filter. The filter comprises two pairs of coupling lines, three open microstrip transmission lines, five grounded microstrip lines, five power supply microstrip lines and five short microstrip lines. By loading varactors between the parallel coupled lines and the tail portions of the transmission lines, resonant mode and bandwidth are controlled, so that the adjustable bandwidth type ultra-wide-band filter is formed. By loading varactor values between the parallel coupling lines, coupling intensity can be adjusted, so that insertion loss can be effectively controlled. By loading varactors at terminals by means of the transmission characteristics of half-wavelength open transmission lines, the position of a generated transmission zero point can be adjusted. By means of the coupling lines with the varactors arranged in between and the half-wavelength open transmission lines with the varactors arranged on the terminals, good transmission characteristics can be realized, two side bands of a passband can be independently adjusted, and the restrain amplitude of an upper stop band within a broadband range can reach 40 dB; the structure is simple, electric property is high, and circuit integration and system packaging can be achieved easily.

Description

technical field [0001] The invention relates to the field of adjustable filters based on varactor diodes, in particular to an ultra-wideband bandpass filter with adjustable bandwidth based on parallel coupled line loading Background technique [0002] With the development of radio frequency systems, wireless communication systems are moving towards fully adjustable and multi-objective. As an important part of reconfigurable wireless systems, tunable filters play a vital role in their development. Tunable filters have received extensive attention due to their wide applications in electronic measurements, military applications, multifunctional receivers, and dynamic spectrum collection, etc. There are semiconductor, radio frequency MEMS, BST film adjustable capacitors, and varactor diodes to achieve reconfigurability. Due to its fast tuning speed and low cost, varactor diodes have received extensive attention from researchers in recent years. In recent years, many scholars a...

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Problems solved by technology

In recent years, many scholars are working on the study of tunable filters with good frequency adjustment, high frequency selectivity and bandwidth control, such as literature 1 (Tang C W, Tseng C T, Chang S C.A Tunable Bandpass Filter With Modified Parallel-Coupled Line[J].IEEE Microwave&Wireless Components Letters,2013,23(4):190-192."), and literature 2 ("Varactor-tuned microstrip bandpass filters with different passband characteristics") introduced several possible The structure of the tunable filter, the shortcomings of the tunable filter structure designed in the past are: (1) the bandwidth adjustment range is limited; (2) the filter performance is unstable during the adjustment process; (3) the varactor diode introduces parasitic parameters , causing unnecessary resonance, the power supply increases the circuit size

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