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Compact 90-and 180-degree directional couplers incorporating bandpass characteristics are presented. They can integrate a bandpass filter and a power-divider/combiner in an RF transceiver, resulting in its miniaturization. The bandpass directional coupler can be represented as a coupled-resonator network, and its coupling coefficients and external-Q can be determined from a desired coupling ratio and operational bandwidth of the bandpass coupler. Measured results are also presented on a Ku-band bandpass 180-degree directional coupler with TE018-mode dielectric resonators.

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This paper presents a novel type of polarizer that is composed of grooved circular waveguides. The presented polarizer is suitable for realizing high performance and low fabrication cost in Ka-band and above because of simple structure. An accurate design of the polarizer is performed using mode-matching techniques. A Ka-band polarizer fabricated with the aid of the design technique has realized excellent performances.

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