| Summary: | This paper presents a novel miniaturization 90° phase shifter using parallel coupled inductors and capacitors. The size reduction is achieved by replacing the quarter-wavelength transmission lines in a conventional fixed 90 degrees phase shifter with the resonator circuit. The resonator circuit, formed by the parallel coupled inductors and capacitor, provides a 90° phase shift at 45 MHz. In this way, the circuit size can be largely reduced without sacrificing the operation bandwidth and power handling. The inductors structure used in the phase shifter carries high power, which consists of two full coupled rectangle metal coils. The proposed miniature fixed phase shifter is then applied to the design of a directional coupler centered at 45 MHz. The measured results show a bandwidth of 40-50 MHz for better than 35 dB return loss with a phase shift of ~90°, a deviation within ~2°, and power handling of 63 dBm (2 kW). Notably, the proposed fixed phase shifter occupies an area of 58.5 mm × 30.5 mm × 33 mm, which is only about 0.009 λ<sub>0</sub> × 0.0045 λ<sub>0</sub> × 0.005 λ<sub>0</sub> at 45 MHz.
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