A tunable microwave notch filter is developed on magneto-dielectric material having low saturation magnetization to attain low external dc magnetic field for biasing. A simple microstrip line at 10 GHz is developed on nickel ferrite/low density polyethylene nanocomposite system as substrates and its microwave transmission response is studied in X-band. Composite system is developed by dispersing nano sized nickel ferrite (~6.63 nm) in low density polyethylene to obtain a homogeneous flexible substrate. Saturation magnetization of 4% volume fraction of the composite is found to be 1.8745 emu/g. Tunability of Q value and insertion loss is studied with magnitude of external dc magnetic field and at different angles of its orientation with the axial plane. A very low field up to 250 G is sufficient to tune the selectivity. An insertion loss of ~-30 dB and Q ~ 375 at 10.2 GHz is observed. The interaction of magneto static modes with orientation of the applied dc magnetic bias with respect to rf magnetic field is discussed with couple mode theory. Good cut-off behaviour of more than 28 dB is observed at magnetic field angles from 23.52° to 34.21°. The experimental and theoretical couplings show close proximity.
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