Dynamic Microstrip band pass filter with capacitive coupling for 4G and 5G wireless communication systems

This paper presents the design and simulation of a reconfigurable capacitively coupled microstrip bandpass filter for 4G LTE and 5G wireless applications. The proposed structure incorporates a PIN diode to achieve dual-frequency operation with low insertion losses and strong impedance matching. Simulation results using HFSS demonstrate two distinct resonant states. In the ON-state (forward bias), the filter operates at a center frequency of 2.70 GHz, achieving an insertion loss of –0.69 dB and a return loss of –16.3 dB, making it suitable for LTE operation. In the OFF-state (reverse bias), the resonance shifts to 3.50 GHz, with an insertion loss of approximately –0.9 dB and a return loss better than –20 dB, aligning with 5G mid-band requirements. The results confirm that the proposed filter provides excellent frequency reconfigurability, good matching performance, and low losses, making it a strong candidate for next-generation adaptive wireless communication systems.

Keywords — Reconfigurable Bandpass Filter, Microstrip, PIN Diode, 4G LTE, 5G, HFSS Simulation.