Equivalent Meandered-Straight Line Concept and Its Implementation for Device Miniaturization

This paper presents an equivalent meandered-straight line concept for miniaturizing microwave devices. To demonstrate the concept, a rectangular meander line model was developed based on theoretical approach. The developed model is applied to design a meandered line, which is equivalent to a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$35-\Omega$</tex> straight line. Good agreement in simulated and measured responses between the meandered-straight line and the corresponding one confirms the proposed concept. The designed meandered line is then implemented to miniaturize a hybrid coupler. The miniaturized hybrid coupler occupies an area of 0.73 times than of the conventional footprint and exhibits good performance. The average transmission amplitude is -3.42 dB, with a very small amplitude imbalance of ±0.05 dB. Moreover, the measured bandwidth for -10 dB reflection coefficient is 830 MHz (34.58%), which indicates a wideband characteristic response.