High-Pass and Low-Pass Mixed Element Lossless Two-Port Networks as Phase Shifters

Abstract

Phase shifters are one of the sub-units in many systems. In active-phased array radar (APAR) systems, digital phase shifters (switched line, reflection, loaded-line, and high pass/low-pass which is the smallest in volume [17]) are used. High-pass/low-pass phase shifters was introduced over 50 years ago [28,40,44]. Besides the size advantage, if their power and phase-bandwidth capabilities are compared with other type phase shifters [7,23,39], high-pass/low-pass phase shifters are the best choice [28]. From the more complicated versions [46] to simple versions [43], the usage of the high-pass/low-pass shifters has increased in the last 20 years. For a system designed to be small in size, all the sub-units must be as small as possible. Therefore, in practice, high-pass/low-pass phase shifters are implemented using lumped elements. However, the connection points will deteriorate the frequency response of the phase shifter at microwave frequencies. Therefore, these points must be considered as distributed elements, circuits must be designed to contain mixed lumped and distributed elements. In this thesis, phase shifting properties of four different mixed element lossless two-port networks have been studied: Two high-pass networks (with inductors and capacitors separated by distributed elements and with capacitors separated by distributed elements), two low-pass networks (with inductors and capacitors separated by distributed elements and with capacitors separated by distributed elements). In the design of these networks, a real frequency-based approach is utilized. Namely, free parameters are initialized, and then optimized to get the desired response. Obtained circuit functions are used to calculate the normalized component values. In the thesis, a new component value calculation process is defined. Calculated normalized values are denormalized to get real component values. In the last section of the thesis, high-pass and low-pass sections are designed. Then real component values are calculated for different frequency values, and performances of the phase shifters are obtained and compared.