Resonator-Based Analog Phase Shifter with Small Loss Variation and Phase Error

An analog phase shifter based on half-wavelength (λ/2) resonators is presented in this paper. By utilizing this approach, phase shift within the operating frequency range can be achieved by changing the center operating frequency (f0) of the λ/2 resonator. In this design, phase slope K for the proposed 180° analog phase shifter is thoroughly analyzed and relative constant K can be achieved for different f0by studying the varactor-loaded λ/2 resonator. As a result, small phase errors can be realized. Moreover, the required capacitance ratio for the employed varactor is quite small for the proposed this design. Accordingly, the varactor internal resistance of the employed varactor can be irrelevant to the shifting phase. Therefore, small insertion loss variation can be also realized in this design. In order to verify the design concept, a fifth-order example centered at 6.5 GHz with an operating bandwidth of 650 MHz is designed and manufactured. According to measurement, the proposed design has provided 0º to 189º phase shift tuning ranges with the maximum in-band phase difference of ±8º. In addition, the maximum insertion loss variation for the proposed 180º tunable phase shifter is about ±0.2 dB.