A millimeter-wave bandpass filter with ultra-wide stopband

Abstract

A millimeter-wave bandpass filter with an ultra-wide stop band, the lower layer microstrip line structure adopts high and low impedance cascaded open-circuit stubs, which can generate transmission zero points for high-frequency signals by using the low-pass characteristics of high and low impedance microstrip lines; the upper layer In the microstrip line structure, the open-circuit stubs cascaded with ladder impedance can achieve better broadband matching, and obtain an ultra-wideband filter with low insertion loss, steep transition band, ultra-wide stop band, and low group delay. At the same time, the length of the stepped impedance microstrip line in the upper layer microstrip line is different from the length of the high and low impedance microstrip line in the lower layer microstrip line. The good matching of the resonator can also increase the transmission pole in the passband of the filter, and increase the transmission zero in the high frequency stopband of the filter, so that the ripple in the passband of the filter is better, with a good transition band and better stopband performance.

Description

technical field [0001] The invention relates to a band-pass filter, in particular to a millimeter-wave band-pass filter with an ultra-wide stop band. Background technique [0002] The contradiction between the continuous increase of new communication systems and the limited spectrum resources continues to deepen. Not only does it need to improve the utilization rate of the original frequency, but also new technologies with higher capacity and faster speed need to be invented urgently. Ultra-wideband technology has been placed high expectations by all walks of life due to its unique and excellent performance, and has become one of the technologies with the most application potential in communication systems in the past ten years. As the core component of the UWB system front-end, the UWB filter's performance will directly have a major impact on the entire system, and has become a research hotspot. [0003] In order to ensure that adjacent ultra-wideband systems cannot interf...

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Problems solved by technology

[0004] However, the ultra-wideband filter based on the microstrip vertical transition structure has poor harmonic suppression, which makes the parasitic passband outside the passband obvious, and the stopband is extremely narrow. In practical applications, it is easy to introduce clutter, causing mutual interference

In addition, the group delay in the passband of most ultra-wideband filters at present is relatively large, and the flatness is not enough, which will cause the phase relationship disorder of the signal arriving at the receiving end due to the phase shift or delay of each frequency component, that is, the phase distortion

In order to make the ultra-wideband filter have a better transition band and better stop band performance, multi-stage cascading is usually used, which not only leads to a large insertion loss of the filter, but also sacrifices the overall size of the filter, which is not conducive to the miniaturization of the system. change

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