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.
A microwave power combiner with waveguide ports is proposed and its design method is described. It can combine a large number of inputs at the same time and its voltage tolerance is high. On the side wall of a circular TM0m0 (m = 2, 3, 4,…) mode resonator, rectangular waveguides are connected as the input terminal while a circular waveguide is connected at the bottom surface of the resonator as the output port. The output is transformed into a rectangular waveguide via a TM 01ô‐TE 10□ mode transformer.
Slits on the side of the output circular waveguide prevent propagation of the modes that do not contribute to the power combining. In the design method, the Y parameters are computed from the equivalent circuit seen from the output side. Thus, the matching condition is obtained from the image parameters. Actual dimensions of the iris for adjustment of the coupling between the input and output waveguides and the resonator can be found from this procedure. The insertion loss of a 14‐GHz four‐way combiner with a TM020 mode resonator was 0.25 dB.
Presently, realization of a high‐output FET amplifier with more than several tens of watts at microwave frequencies requires power combining. This paper proposes a low loss and broadband power combiner with a simple structure in which a cylindrical TMOmO mode (m × 2, 3, …) cavity with coaxial input and output lines is used. The effects of modes m and the number of devices to be combined are studied by means of an equivalent circuit. Since the spurious modes in the resonator degrade the reliability of the power‐combined FET amplifier, a structure is proposed in which slits and subcavity are attached to the TMOmO mode cavity for suppression of spurious modes. To verify the effectiveness of these structures, the spurious modes are excited and their reflection characteristics are measured. The insertion losses of the 4‐ and 8‐way combiners designed with m × 2 and 4 in the 12‐GHz band are 0.25 and 0.45 dB, respectively. An FET amplifier with a maximal output of 40 W is realized with the present power combiner.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.