Compact frequency and bandwidth tunable stopband filters using split ring resonators and varactors coupled transmission line
Two highly compact tunable stopband filters using microstrip transmission lines coupled with split ring resonators (SRRs) and varactor diodes are presented. Frequency or bandwidth tuning capability of each device is demonstrated. The frequency tunable filter, realized by a single stage, shows a wide tuning range of 19.8% with a maximum bandwidth of 5% and an insertion loss of approximately 20dB at 4GHz. The bandwidth tunable filter, realized by double stages, shows a 10-dB bandwidth of 1934% with a biasing voltage of 010V. The implemented frequency tuning and bandwidth tuning devices show a significant area reduction of 60.1% and 53.5%, respectively, in comparison with a similar frequency or bandwidth tunable structure presented by others. Equivalent circuit models are presented. The measured S-parameters are in good agreement with simulated ones.
varactor split ring resonator (srr) tunable filter metamaterial wide bandwidth