Parallel connection type unilateral elliptic function transmission line filter

Abstract

The invention provides a parallel connection type unilateral elliptic function transmission line filter composed of transmission line elements. Input signals are fed into a first parallel connection cross joint (2) from an input transmission line (1) and divided into two paths to be transmitted to a second parallel connection cross joint (7) respectively through a cascading transmission line joint (3) and a parallel connection transmission line joint (4), and two paths of the input signals are synthesized and then output from an output transmission line (8). Two open circuit transmission line branch joints are connected to the two parallel connection cross joints respectively to adjust the amplitude of reflected signals. As for given cut-off frequency fc, various transmission line element parameters are selected, more than two nonzero limited frequency reflection null points with frequency lower than or higher than fc are generated, and a passing band is generated nearby a frequency band of the nonzero limited frequency reflection null points; meanwhile, more than two nonzero limited frequency transmission null points with frequency higher than or lower than fc are generated, a stop band is generated nearby a frequency band of the nonzero limited frequency transmission null points, and therefore filter characteristics of a unilateral elliptic function nearby fc are achieved. The filter is suitable for bandwidth below the medium degree of microwave and millimeter wave frequency bands, low loss, high selectivity.

Description

technical field [0001] The invention relates to a system widely used in microwave and millimeter wave frequency band communication, radar and measuring instruments, etc., to control the frequency response of signals, block the transmission of frequency components of useless signals, and make the frequency components of useful signals pass through almost without attenuation filter. Background technique [0002] Filters are passive circuits widely used in microwave circuits and systems. They are used to achieve specific frequency selection characteristics. Filters can be divided into high-pass, low-pass, band-pass and band-rejection types according to transmission characteristics. The passband of the filter Properties such as insertion loss and stop band rejection have a great influence on the performance index of the circuit. With the increasingly tight frequency resources and the increasingly crowded spectrum, the radio system puts forward higher requirements for the freque...

AI Technical Summary

Problems solved by technology

However, the circuit implementation is complicated, and it is usually implemented by introducing cross-coupling between non-adjacent resonant cavities.

Although the synthesis and design of this filter with cross-coupling have been widely studied, its processing and debugging are difficult, which limits its engineering application.

[0004] In order to achieve good frequency selection characteristics near the working frequency band, band-pass filters and band-stop filters are mainly used at present. However, band-pass filters with steep transition band attenuation characteristics generally require multi-stage filters. Multi-stage filters are composed of a Composed of a series of mutually coupled resonators, the insertion loss is large, the in-band group delay and its fluctuation increase, and the volume is large

Multi-stage band-stop filters have the same disadvantages

A filter with a single high-Q resonant tank can achieve lower insertion loss, but this single-loop filter has a narrow bandwidth, which is difficult to meet the requirements of practical applications

Images