A Reconfigurable Capacitively-coupled Microstrip Bandpass Filter for 4G LTE and 5G Applications

This paper presents the design and simulation of a reconfigurable bandpass filter operating at 3 GHz for 4G LTE and 5G applications. The proposed filter structure is based on a capacitively coupled microstrip open-ring resonator. It utilizes a substrate with a dielectric constant of 3.55 and incorporates PIN diodes to achieve adjustable frequency. After conducting eigenmode analysis and simulations using HFSS and ADS, the proposed filter exhibits two distinct operating states: a center frequency of 3.0 GHz when the diode is in reverse bias and 2.65 GHz in forward bias. The design performs exceptionally well, demonstrating minimal insertion losses of -0.69 dB and -0.96 dB, respectively, along with satisfactory return loss.