Co-planar waveguide filter with ground perforation for ultra-wideband system

In this paper, a compact co-planar waveguide band-pass filter is proposed for ultra-wideband (UWB) communication systems by utilizing perforation in the ground layer. An aperture compensation technique is developed to control the coupling strength, since UWB filters require a strong coupling strength due to its wide bandwidth (> 50%). The coupling strength appears frequency-distributed and its maximum value rapidly rises as the aperture widens. Then, a pair of capacitively loaded line sections is inserted between two identical parallel coupled lines to formulate a new planar band-pass filter with multi-pole band-pass behavior. The predicted and measured results show attractive properties of the proposed filter with a pass-band of 3.1 to 5.0 GHz (50%), |S₁₁| < -18 dB, group delay 800 psec, insertion loss < 1 dB, and the size of 9 × 9 mm².