Reconfigurable bandpass filter using Ce-doped YIG ferrites for wideband applications

Integration of compact, tunable, low-cost monolithic microwave integrated circuit-based bandpass filters on a semiconductor substrate has been a persistent requirement in the communication industry. In the present investigation, a compact reconfigurable bandpass filter is fabricated using a double T-transducer based on the phenomena of magnetostatic surface spin waves (MSSWs). The Ce-doped Bi0.1YIG 500 μm thick disks with cerium concentration in the range of 0.2–1.0 provide the path for the propagation of MSSWs. The operating frequency for this device extends from S to X band Rogers RT/duroid® substrate, which is used for planar microstrip filter design, fabrication, and testing for practical applications. The effect of the coupling gap between the two transducers was optimized using appropriate choice of lumped components to improve the performance of the filter. The best coupling was observed for 1.2 mm coupling gap. The simulated and experimental results confirm the lowest insertion loss of −1.24 dB. The operating frequency shows a large tunability of 132.3% with a relatively small bias field of 0.3–2.1 kOe. The promising characteristics of bandpass filters such as low passband insertion loss, narrow bandwidth, high bandpass reflection coefficient, and high band-stop rejection were achieved by varying the Ce concentration in YIG samples.