Tunable microstrip filter with piezo-moved ground electrode

New principle of microstrip resonators and filters tuning is developed and studied. Realized idea is the operation by the effective dielectric constant (/spl epsiv//sub eff/) of substrate using piezo-control. For that, between substrate and ground electrode a narrow air gap (/spl Delta/) is created, and its size is controlled by the piezoelectric plate. The change in /spl epsiv//sub eff/(/spl Delta/) leads to the variation of filter resonant frequency while quality factor is preserved.