Modeling of LTCC-Ferrite Tunable Inductors and Development of an -Band Phase Shifter

This paper presents the modeling of a tunable inductor using a low-temperature co-fired ceramic (LTCC)-ferrite tape and subsequent development of a loaded transmission line phase shifter using these inductors. The inductors are initially realized in the form of circular disks fabricated from commercially available ferrite tape (ESL 40011) wound with a copper wire. A complete model of this inductor is obtained between 0.3 and 4 GHz and validated by measurements. The phase shifter comprises these inductors in shunt, thus minimizing the effect of low-field magnetic losses in L-band. The magnetic material is operated below the resonance region in a partially magnetized state with the help of a bias current that configures the phase shifter electronically. The phase shifter exhibits an insertion loss of 2 ± 0.5 dB and a differential phase shift varying between 35° and 10° in the above band. Finally, to demonstrate the feasibility of integration with other RF components, a working prototype of the same phase shifter that is fully integrated in LTCC is also presented with measurements.