The characteristic analysis of CPW bandpass filter by magnetic material

This paper presents the characteristic analysis of coplanar waveguide (CPW) filters with flaky magnetic material on top of the filter. This 2-port CPW 2.3-GHz filter with single-ended input single-ended (SISO) output is fabricated on FR4 (Flame Retardant 4) substrate, to discuss the influence of magnetic material on the variations of operating frequency, bandwidth and center frequency. According to measurement results, when magnetic material with different thicknesses is placed on the CPW filter, the center frequency of the filter decreases as the thickness of the magnetic material increases, and vice versa. The frequency decreases by 20% as the thickness of 4mm magnetic material on the top. The lower and upper sides of passband frequency are reduced by 3.29MHz and 6.71MHz per mm thickness of magnetic material on average, respectively. This change can be achieved due to the magnetic materials' layers on top of CPW filter not by changing the actual hardware of the circuit.