A Design of Compact Wideband Bandpass Filter with Controllable Center Frequency Using Different Rectangular Arrays

Abstract

This study presents a design of compact wideband bandpass filter with a chip size of $1140 \mu m \times 1424 \mu m$ (including pads) and fabricated through GaAs-based integrated passive technology. The proposed bandpass filter is consisted of an intertwined spiral inductor and a rectangular-array-capacitor. The spiral inductor is intertwined targeting to achieve a high inductance so that the center frequency of bandpass filter could be lower, moreover, a compact size can be obtained. As for the capacitor, through changing the size and number of rectangular array, the capacitance can be varied and thusly, the center frequency of bandpass filter can be controlled. Simulation results show that a wide bandwidth with fractional bandwidth of 126%, and the center frequency could be varied from 3.35 GHz to 3.19 GHz through changing the size and number rectangular array. Furthermore, the frequency of lower band transmission zero could be varied from 2.40 GHz to 2.35 GHz, the frequency of upper band transmission zero could be varied from 7.21 GHz to 7.13 GHz, giving an option to slightly enhance the selectivity of bandpass filter. This study is expected to give a method for the design of controllable bandpass filter based on semiconductor fabrication technology.