A multi-resonator combined cavity filter

Abstract

The invention discloses a multi-resonator combination cavity filter, which comprises a cavity with a top opening and a cover plate located at the opening of the cavity, wherein the cavity is internally provided with at least three resonant cavities, resonant rods are respectively fixed at the bottom of the resonant cavities, tuning screws penetrate through the cover plate and are inserted into theresonant rods respectively, and the plurality of resonant cavities, the resonant rods located inside the corresponding resonant cavities and the tuning screws extending into the corresponding resonant rods form a plurality of resonators; the cavity depth of the resonant cavities decreases in sequence along a radio frequency signal transmission direction, and the height of the resonant rods located inside the corresponding resonant cavities decreases in sequence, thereby ensuring that the resonators are enabled to be identical in working frequency but mutually different in resonant frequency through adjusting the length of the tuning screws extending into the resonant cavities. The resonators of the cavity filter are identical in working frequency but mutually different in resonant frequency at a frequency doubling position, thereby enabling the resonators to mutually supplement in harmonic suppression, and thus enabling the cavity filter to be better in harmonic suppression ability.

Description

Technical field [0001] The invention belongs to the technical field of microwave filters, and more specifically, relates to a cavity filter with a combination of multiple resonator structures. Background technique [0002] Microwave cavity filters are widely used in wireless systems such as digital microwave communications, mobile communications, and navigation systems. Its main function is to allow useful signals to pass as far as possible without attenuation, and to have as much reflection as possible for useless signals. As the spectrum resources of microwave radio frequency systems become increasingly scarce, the requirements for filtering performance of filters are also getting higher and higher. For wireless systems, out-of-band harmonics are generally generated at the center frequency multiplier. Out-of-band harmonic signals will have a relatively large impact on the signal-to-noise ratio of the system and will interfere with other wireless systems. Therefore, the microwav...

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Problems solved by technology

[0003] At present, the cavity filter is formed by cascading resonators. In order to ensure that all resonators can work at the same operating frequency, it is generally designed that all resonators have the same resonant frequency. Since the resonant frequency of each resonator is different It is periodic, so the passband characteristic of the filter is also periodic. For a filter with a center frequency of F0, it will generate spurious passband, resulting in reduced filter rejection of out-of-band harmonics at these octaves

When the input signal frequency is wide, the double frequency passband of the resonant frequency can also pass through the filter, resulting in a decrease in the filtering performance of the filter. Therefore, it is urgent to find a cavity filter that can suppress out-of-band harmonics at the double frequency.

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