In this contribution two planar microstrip band-pass filters based on closed loop resonators with reconfigurable center frequency are proposed at K-band. Two geometries, a square-ring and a meander loop, are closely investigated. The frequency reconfigurability is achieved by means of PIN diodes. The filters are designed for and fabricated on a standard printed circuit board technology. Dual-mode resonators are used to obtain a compact design suitable for integration into an active antenna frontend. The paper presents the filter design, the tuning range, an analysis of the occurring losses, and the verification through simulation and measurement.
