A new design of a tunable WLAN-band pass filter using a combination of varactor device, RF-choke and Hairpin-Defected Ground Structure

A novel compact electrical tunable microstrip band pass filter, realized by coupling two Hairpin-DGS resonators, is proposed. The tunability is achieved by embedding varactor diodes to the Hairpin-DGS resonators. The measured relative tuning range of the band pass filter is 23.5% with a fractional bandwidth of 8%. The measured insertion loss is 3.6 dB to 2.1 dB within the tuning range. The simulated and measured results show good agreement and validate the proposed approach.