This paper presents some structures of artificial coplanar waveguide with very slow phase velocity and their applications to a design of compact 3-dB branch-line couplers. The slow-wave structure is constructed by periodically loading both of series inductance and shunt capacitance. First, a basic miniature branch-line coupler is designed and consequently considerable size-reduction of about 1/4 is obtained. Next, a broadband design technique is described using open-circuited quarter-wavelength series-stubs added at each port as a matching network. By size-reducing the series-stubs and branchline sections, a very compact broadband coupler with a good hybrid performance over a wide bandwidth of 31 percent or more is realized. The design concepts and procedures are verified both numerically and experimentally.

A metallic waveguide that has an array of dielectric rods located at a distance from the side wall of approximately one quarter the waveguide width was previously proposed for single mode propagation over a wide frequency range. In this study, the S parameters of such a waveguide were measured for the TE10 mode.

A new type of mode converter that converts TE30 to TE10 mode is proposed. As an example of the ease of fabrication, holes can be drilled at the top of a metallic waveguide and dielectric rods inserted. This converter is useful for application as a power divider or power combiner.

This paper suggests a new type of 180-degree 3 dB hybrid, which consists of a cylindrical cavity and four E-plane rectangular waveguides radially coupled with it, and shows that good hybrid properties are realized by modifying the positions of the four input/output waveguides and the radius of the cylindrical cavity that are determined by the field distribution of the TE111 resonant mode. Moreover, a method of broadening the bandwidth with additional impedance steps is described. The present hybrid is marked by simple structure, and hence is useful for applications at millimeter wave frequencies and to high-power microwave systems. Experimental verification is additionally shown.

This paper describes a novel Wilkinson power divider operating at two arbitrary different frequencies. The proposed divider consists of two-section transmission lines and a series RLC circuit connected between two output ports. The circuit parameters for a dual-band operation are derived by the even/odd mode analysis. Equal power split, complete matching, and good isolation between two output ports are numerically demonstrated. Dual-band and broadband Wilkinson power dividers can be successfully designed. Finally, verification of this design method is also shown by electromagnetic simulations and experiments.

This paper treats a new-type power combining system of four oscillators equally coupled to one another through an eight-port hybrid. This system is marked by easy analyzability and adjustability from its symmetrical construction. In addition, a combined power from the four oscillators is distinguishably delivered to an arbitrary port of four output ports, and hence can be switched in four ways. Experimental corroboration is presented also.

A metallic waveguide with dual in-line dielectric rods can propagate electromagnetic waves more than two times higher than the cutoff frequency region and without higher modes [1]. If the straight portion in the waveguide has even symmetry, then dielectric rods are only required in the bent portion. Connection losses between the portions are improved by adding other dielectric rods.

This paper presents a new quarter-wavelength microstrip coupler compensated with a periodic sequence of floating metallic strips in the slots on the inner edges. After describing the characteristics of the coupled-line, as an example, a 15-dB coupler is designed and a high directivity of 30 dB or more in theory is obtained over a full band of a single-section coupler. Next, couplers with various coupling factors are designed, and the usefulness for very loose coupling is demonstrated. Furthermore, a three-section coupler is designed to show the effectiveness in a wide frequency range. The validity of the design concept and procedure is confirmed by electromagnetic simulations and experiments.

A system that has an array of dielectric rods at the center of a waveguide was previously suggested for single mode propagation with a wide frequency range. However, it is difficult to introduce the wave source from a coaxial cable, due to use of the TE10-like and TE20-like modes. In this investigation, an asymmetric setup of the dielectric rods is proposed for better coupling efficiency of the TE10 mode.

Dielectric rod arrays in a metallic waveguide alter the propagation modes and group velocities of electromagnetic waves. We have focused on TE30-to-TE10 mode converters and investigated how their behavior varies with frequency. A mode converter is proposed that passes the TE10 mode at frequencies lower than 2fc, and converts the TE30 mode into the TE10 mode for frequencies higher than 3fc.