A Compact and Electrically Adjustable Balanced Bandpass Filter

Abstract

The invention discloses a compact electrically tunable balanced band pass filter. The filter comprises an upper layer of a microstrip line structure, a middle layer of a dielectric substrate and a lower layer of a grounding metal patch and metal through holes. The microstrip line structure comprises a multimode resonator and two pairs of input/output feeders. The multimode resonator comprises a first microstrip line and a second microstrip line which are symmetrical up and down; the first microstrip line and the second microstrip line are all E-shaped; the first microstrip line faces downwards; the second microstrip line faces upwards; the microstrip branch lines at the left and right two sides of the first microstrip line are connected with the microstrip branch lines at the left and right two sides of the second microstrip line respectively through two variable capacitance diodes which are connected in series; the central microstrip branch line of the first microstrip line is connected with the central microstrip branch line of the second microstrip line through two variable capacitance diodes which are connected in series; and a section of short microstrip branch line is loaded at the center of the two variable capacitance diodes which are connected in series. According to the filter provided by the invention, the central frequency of a passband is tunable; and the bandwidth is tunable.

Description

technical field [0001] The invention relates to a balanced band-pass filter, in particular to a compact and electrically adjustable balanced band-pass filter used in a reconfigurable radio frequency front-end system requiring high signal-to-noise ratio, and belongs to the technical field of microwave communication. Background technique [0002] The rapid development of wireless communication technology puts forward higher requirements for the high performance, miniaturization, compatibility and flexibility of the RF front-end system. As an important part of the RF front-end system, the RF electronically tunable filter has the advantages of small size, low cost, and reconfigurability, so it has been paid more and more attention. Compared with the traditional single-ended filter, the balanced filter has the effect of common mode suppression, which can well suppress the noise interference of the surrounding environment, improve the signal-to-noise ratio, and meet the high-quali...

AI Technical Summary

Problems solved by technology

However, once the filters designed by these two methods are processed, the bandwidth cannot be adjusted during the frequency adjustment process

[0006] In summary, most of the published articles or patents involve reconfigurable single-ended bandpass filters, and there are relatively few adjustable balanced bandpass filters that can suppress environmental noise. The proposed method and structure and the realized limited performance

In practical applications, not only the center frequency of the filter is required to be adjustable, but the bandwidth is also adjustable. Although the bandwidth of the adjustable balanced filter involved in the published articles or patents is controllable, once it is processed, the frequency During the adjustment process, the bandwidth is not adjustable

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