Magnetic Tuning of Three-Pole Microstrip Bandpass Filter

摘要

Lot of work on frequency tuning in resonators and filters with magnetic biasing fields have been reported. Normally the frequency shifts are due to variation of ferrimagnetic resonance of substrate material. In the present paper we have reported the frequency tuning of three-pole microstrip bandpass filter by varying the relative permeability of the substrate material with the externally applied dc biasing magnetic field. For this a three-pole microstrip bandpass filter with a center frequency 2.8 GHz was fabricated' using a thick silver film deposited oh LiZnTi polycrystalline ferrite substrate. A tunability of 17 MHz in the moderate range of applied magnetic field was observed at room temperature. Fabricated device shows the negligible variation in its transmission loss in the presence of biasing field.