Novel C-band tunable bandpass filter with low bias magnetic fields using partially magnetized ferrites

Abstract

A compact magnetically tunable bandpass filter on partially magnetized yttrium iron garnet (YIG) substrate is presented. The bandpass filter led to a large frequency tunability of 7% (from 5.77 to 6.2GHz) under a low bias field of 0 to 100 Oe, while partially magnetized ferrites exhibit a tunable permeability μ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> range from 0.71 to 0.94. The bandpass filter also exhibited a good impedance match and a low insertion loss of about 1 dB. These results are in sharp contrast to conventional YIG based tunable bandpass filters that need large bias fields of >1 kOe at C-band, and will lead to more compact tunable bandpass filters with low power consumption.