Miniaturised dual‐mode dielectric resonator filter with controllable passband

A miniaturised dual‐mode filter based on dielectric resonator (DR) with a controllable passband is proposed in this Letter. The filter is a combination of a traditional rectangular DR and a planar metallic loop with the dual‐mode feature. The loop decreases the frequencies of the dominant modes inside the DR, thus the circuit size is greatly reduced compared with the traditional DR devices. By using commonly used tuning disk, the passband of the proposed filter can be altered freely. A demonstration example is designed and fabricated, and the simulated and measured results verify the design method with good agreement.