Research of Impedance Characteristic for FR4 Substrate CBCPW Transmission Line

keywords:FR4 substrate, FDTD, CBCPW, impedance characteristic, return loss

Abstract:For purpose of improving matching performance between RF circuit and antenna, the characteristic impedance and return loss of CBCPW based on FR4 substrate using the FDTD method are calculated. Based on theoretical analysis, several CBCPW with FR4 substrate are fabricated. The thickness of substrate is 1.5mm, the width of center conductor are chosen to be 1mm, 1.5mm and 1.7mm respectively, while corresponding slot width are 0.2mm, 0.3mm, and 0.4mm. S₁₁is measured using vector network analyzer within the frequency range of 1MHz to 3GHz. Good agreement with theoretical analysis is achieved even in high frequency band, and all of the three CBCPW have return loss below 10dB. The third structure has the best matching character with considering fabrication error and soldering techniques.