Compact Absorptive Microstrip Bandpass Filter with Adjustable Bandwidth and Phase

Abstract

In this communication, a compact absorptive bandpass filter (ABPF) characterized by adjustable bandwidth and phase, low group delay (GD), a high absorptive ratio and low insertion loss (IL) is proposed. The presented ABPF consists of a bandpass section that is made of a quarter-wavelength coupled line and four stubs that are basically a lumped resistor in series with a short-circuited quarter-wavelength transmission line. The stubs not only perform the function of absorption but also have the advantage of adjustable bandwidth and phase. To verify the design concept and analysis formulas, an ABPF operating at 2.4 GHz is fabricated and measured; its simulated and measured results are in good agreement.