Active ultra-wideband filter design for 5G applications

Abstract

In this paper, a microstrip band-pass filter with adjustable operating frequency bandwidth is proposed. The filter is mainly composed of four resonant units with the same structure and size. Each resonance unit can achieve the band-pass independently by regulating the on and off states of the diodes. Moreover, there is a square metal structure inside each resonant unit. The square structure has four slots with the same size, and four PIN diodes of the same type are welded in sequence at the slots. The internal coupling strength of the resonant unit can be controlled by randomly adjusting the on and off states of the four PIN diodes in the resonant unit. In addition, a liquid crystal material is placed in the middle of the double-layer dielectric plate under the four resonance units, and the dielectric properties of the material can be changed by adjusting the voltage, thereby further expanding the band-pass characteristics of the filter. As a result, the operating bandpass range of the resonant unit can be regulated.