A Four-Frequency Differential Bandpass Filter

Abstract

The invention provides a four-frequency differential bandpass filter, and aims to improve the out-of-band selectivity of the four-frequency differential bandpass filter and reduce the in-band insertion loss. The four-frequency differential bandpass filter comprises a dielectric substrate; two first microstrip resonators, two second microstrip resonators, two step impedance microstrip lines and uniform impedance microstrip lines, which are symmetrical about the axis AA', are printed on the upper surface of the dielectric substrate; the uniform impedance microstrip lines are etched with a pair of interdigital coupling linear gaps, and are connected with the tail ends of high impedance microstrip lines of the two step impedance microstrip lines; a U-shaped input microstrip line is printed atone side of the axis AA'; a U-shaped output microstrip line is printed at the other side of the axis AA'; a metal floor is printed on the lower surface of the dielectric substrate; a first step impedance gap line and a first L-shaped step impedance gap line, which are connected, are etched at one side of the U-shaped output microstrip line on the metal floor; and a second L-shaped step impedance gap line and a second step impedance gap line, which are connected, are etched at one side of the U-shaped output microstrip line.

Description

technical field [0001] The invention belongs to the technical field of microwave and radio frequency, in particular to a four-frequency differential band-pass filter, which can be applied to the radio frequency front end of a wireless communication system. Background technique [0002] In recent years, with the rapid development of communication technology, the filter, as a key frequency selection device, plays an increasingly important role, and its performance often directly affects the quality of the entire communication system. With the continuous advancement of wireless communication technologies such as Global Positioning System, Wireless Local Area Network, Global Interoperability Microwave Access, and Mobile Cellular Systems, single-frequency filters are no longer practical due to their poor adaptability and large size. In order to satisfy multiple functions of multi-band terminal equipment at the same time, multi-band filters have become the mainstream of filter dev...

AI Technical Summary

Problems solved by technology

Since the research on the four-frequency differential band-pass filter is not deep enough, the performance of the current four-frequency differential band-pass filter needs to be further improved

[0003] For example, in 2017, scholars such as Zhang Shi Xuan published the paper "MultibandBalanced Filters With Controllable Bandwidths Based on Slotline CouplingFeed" in the journal IEEE MICROWAVE AND WIRELESSCOMPONENTS LETTERS (Vol.27, No.11, NOVEMBER 2017), and proposed a coupling-based embedding The resonator's four-frequency differential bandpass filter uses a slot line coupling feed structure for feeding to achieve inherent common-mode rejection, and the center frequency and bandwidth are adjustable by using four pairs of nested folded half-wavelength resonators However, due to the multi-layer nested structure of the resonator, the insertion loss of the two high-frequency passbands of the four-frequency differential bandpass filter is relatively large, and the out-of-band selectivity is low

Images