Ultra-wideband band-pass filter with transmission zero point

Abstract

The invention discloses an ultra-wideband band-pass filter with a transmission zero point, and aims to provide a band-pass filter with the excellent trapped wave characteristic and standing wave performance. The ultra-wideband band-pass filter with the transmission zero point is realized by the following technical scheme that dumbbell rectangle heads of two symmetric air bridges restricted betweenmetal ground passbands are symmetrically etched on the wide edges of the left and right sides of each of the front and back surfaces of a dielectric substrate, the first dumbbell head located at theproximal end of the wide edge of the dielectric substrate forms an equivalent circuit of a first resonator and lumped parameters of the first resonator in a manner that a first high-impedance short-circuit branch is vertically connected with a first low-impedance open-circuit branch of a terminal, and the second dumbbell head located at the far end of the wide edge of the dielectric substrate forms an equivalent circuit of a second resonator with a dual relationship with the first resonator and lumped parameters of the second resonator; and an equivalent circuit of a third resonator and lumpedparameters of the third resonator, composed of an H-shaped branch, falls in a cup-shaped cross section formed by synthesizing two flag shapes oppositely and symmetrically, wherein the first resonatorsequentially transmits signals to the second resonator and the third resonator to form a main transmission link path.

Description

technical field [0001] The invention is suitable for radio frequency microwave communication systems, and can be widely used in ultra-wideband band-pass filters at the front end of ultra-wideband communication systems. Background technique [0002] Filters are one of the indispensable devices in wireless communication systems. In the communication system, the signal will be interfered by the environmental noise signal outside the system, as well as the harmonic influence in the system due to the nonlinearity of the system, which will significantly reduce the communication quality of the communication system. In order to suppress the interference signal outside the system and the harmonic signal generated by nonlinearity in the system, it is necessary to add a filter to the system to ensure that the useful signal can pass through with a small loss, and the useless signal can be suppressed greatly. [0003] With the rapid development of mobile communication technology, ultra-...

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Problems solved by technology

However, this solution will bring an additional increase in the size of the entire filter, which is not conducive to the realization of miniaturized design

The design of UWB filter mainly has the following difficulties: (1) The relative bandwidth has reached 110%, and the commonly used narrowband and broadband filter design methods (such as [3] parallel coupling type, interdigitated type) are no longer applicable, and need New theories and design methods have been proposed and applied; (2) There are higher requirements on performance (such as in-band insertion loss and group delay are smaller)

(3) The frequency band span is too large, and there are many other narrow-band transmission signals in the band (such as: WiMAX: 3.3GHz-3.6GHz, satellite C-band: 3.7GHz-4.2GHz, WLAN: 5.15GHz ~5.35GHz&5.725GHz~5.825GHz), so how to add notch characteristics in the passband to suppress narrowband signals is also a design difficulty

The method of cascading high- and low-pass filters is equivalent to using two filters to realize the function of a band-pass filter, and the volume is too large; microstrip multi-mode resonance technology is one of the mainstream technologies for realizing ultra-wideband filters, but due to It has only one resonator, and it is difficult to introduce a notch point in the passband and a transmission zero point outside the passband at the same time in terms of structure; low-temperature co-fired ceramic technology and liquid crystal polymer technology, complex processing, high cost, and difficult to introduce transmission zero

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