Design of Coplanar Stripline Bandpass Filter With Reconfigurable Filter Switch

This article has designed a bandpass filter using a coplanar stripline stub (CPS) resonator consisting of open and short-ended strip lines connected to the PIN diode switches. The use of spurline stub resonators inside CPS results in bandpass and bandstop filters, depending on the PIN diode switch configurations. The work presents a novel circuit architecture aimed at reducing the parasitic resonance of the spurline resonators and acquiring the necessary series stub characteristics. The proposed filter resonates at 6.9–9, 1.7–4.7, and 8.4 GHz when the PIN diodes are forward and reverse-biased, respectively. It also resonates at 1–2.1, 4.8–5.3, and 6.9–9 GHz when one diode is reverse-biased, and the other is connected in forward bias. An insertion loss below −0.55 dB and a return loss less than 10 dB have been obtained during simulation and measurement. The designed filter can find different applications for the 1.8 GHz GSM band, 2.4/5.8 GHz (WLAN), 3.6 GHz (WiMAX), long-term evolution (LTE), and WIFI. The filter can be used in various multi-frequency systems owing to its compact size. The measured and simulated findings of the proposed CPS spurline stub resonator wideband bandpass filters are substantially consistent.