A filter and a transmission zero point adjustment method of the filter

Abstract

The filter of the present invention includes a filter main channel and an energy absorbing coupling unit connected to the input and output ends in an additional coupling manner. The energy absorbing coupling unit is composed of two resonators with the same or similar frequency and coupling. The filter of the present invention can directly generate a pair (two) of transmission zeros through an additional coupling, and even produce multiple pairs of transmission zeros, thereby greatly reducing the physical size of the filter, and simultaneously solving the problem of no cross-coupling but possible The key issue of realizing filter transmission zero. Properly adjusting the frequency of each resonator in the energy absorbing coupling unit can also realize the asymmetric distribution of transmission zero points, which solves the problem of arbitrary distribution of transmission zero points. At the same time, the filter of the present invention has no restrictions on the resonator structure, so all resonators can adopt the same shape, and there is no need to introduce coupling cross lines. The whole design process is the same as that of the traditional Chebyshev filter. becomes simpler.

Description

technical field [0001] The invention relates to the technical field of filter devices, in particular to a design of a filter without cross-coupling but with a transmission zero point and a method for adjusting the transmission zero point of the filter. Background technique [0002] Strong anti-jamming capability has become one of the most important performances of contemporary communication systems. In wireless communication systems, interference mainly comes from electromagnetic waves with frequencies close to the passband frequency, especially adjacent frequency signals. Interference will lead to the reduction of the coverage of the communication base station, a sharp drop in communication capacity, and a sharp drop in signal quality. When the interference is severe, it may even cause the communication system to be paralyzed. For the new generation of digital communication systems, the negative effects of various interferences will be more serious, mainly because high-spe...

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Problems solved by technology

[0004] (1) Most of the coupling realized by using the crossover line is electric field coupling. In order to realize the quasi-elliptic function characteristics of the filter, it is required that the coupled coupling in the main path must be magnetic field coupling, which makes the structure selection of the resonator subject to certain restrictions. limit

[0005] (2) In order to avoid unnecessary additional coupling between the crossover line and unrelated resonators while achieving the desired cross-coupling, it is often necessary to optimize the topology of the filter and use some resonators with very special structures And the special coupling structure, and sometimes the resonators have to be misplaced, which is not conducive to the miniaturization design of the filter

Therefore, it is difficult to achieve strong coupling between resonators by using crossover lines, and it is also difficult to achieve a filter design with a relatively large bandwidth.

Especially when the operating frequency is relatively low and the miniaturization of the device is required, the difficulty is even greater

Even if a narrowband filter is designed, due to the limitation of the processing technology, the processing yield of the filter with coupled cross lines is relatively low, and the processing repeatability is not ideal.

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