Ultra-Compact Inductive Coupled UHF Tunable Filter
In this paper, ultra-compact inductive coupled UHF tunable filters with two different coupling coefficients have been designed, fabricated, characterized, and compared. The relationship between the coupling coefficient and the filter's performance has been investigated. The proposed filters were fully embedded into low cost multi-layered organic package substrate. The embedded filters were comprised of high Q spiral stacked inductors, high dielectric BaTiO 3 composite MIM capacitors, and varactor diodes. The fabricated two filters were operated in the frequency regime ranged from 500MHz to 900MHz for TV tuner receivers. The one with a coupling coefficient of 0.26 exhibited lower insertion loss of approximately −2dB, higher return loss of below −10dB, and larger tuning range of 56.3%. The other one with a coupling coefficient of 0.17 was more selective than that with a coupling coefficient of 0.26. The fabricated tunable filter exhibits extremely compact volume of 3.4 × 4.4 × 0.5mm 3 , which is the smallest in previously reported ones.