Mitsuyoshi Kishihara

H-Plane Crossed-Waveguide Hybrids

This paper presents a novel cruciform quadrature hybrid in H-plane rectangular waveguide, which is composed of two cross waveguides having two cylindrical metallic posts in the cross region, and one post at each input/output port. The former two posts produce directional nature in a signal flow, and the latter post achieves a matched state. Several basic hybrids are designed in this structure, and then a broadband one is successfully realized. Actually, a fractional bandwidth of about 28 percent is obtained with a tolerance limit for return loss and isolation of 20 dB, and the power-split imbalance stays within plusmn0.1 dB over the bandwidth. The validity of the design results is confirmed both numerically and experimentally. Furthermore, the advantage of the present hybrid is demonstrated by comparison with conventional hybrids

Cruciform directional couplers in H-plane rectangular waveguide

This paper suggests a very compact waveguide directional coupler with a tight coupling of 3-dB or so, which is composed of two cross H-plane rectangular waveguides having two metallic posts in the square junction and an inductive window at each port. The metallic posts are set symmetrically along a diagonal line of the cross region mainly to make for the directivity properties, and the inductive windows are arranged properly at each input/output port near the junction to realize a matched state. Actually, several couplers are successfully designed based upon this concept. Additionally, the design procedure is validated by em-simulations (HFSS) and experiments. The present coupler is marked by a compact coplanar structure, four right-angled ports and ease of realizing 3-dB coupling.

Backfire-to-endfire radiation characteristics of CRLH-TL using substrate integrated waveguide and metal-patches

We have proposed a new type of the CRLH-TL consisting of two-layer planar substrates recently. It consists of a base waveguide of a substrate integrated waveguide (SIW), and series capacitances realized by slit apertures and metal patchs arranged on the upper conductor of the SIW. It is expected to become one of the basic CRLH-TL structures over 10 GHz or millimeter-wave. However radiation from the metal-patchs cannot neglect in this structure. Then we proposed a leaky-wave antenna using the SIW metal-patch type CRLH-TL. In this paper, beam scan characteristics as a function of driving frequency are confirmed theoretically and experimentally. A SIW metal-patch type CRLH-TL with transition frequency of 16 GHz is designed for a leaky-wave antenna and fabricated. Measured results agree well with theoretical and numerical results.

Design of Cruciform Substrate-Integrated Waveguide Hybrids Based on H-Plane Planar Circuit Approach

This paper suggests a novel cruciform substrate- integrated waveguide quadrature 3-dB hybrid, and shows the frequency characteristics of hybrids designed at various center frequencies using the H-plane planar circuit approach. As a result, relatively flat coupling properties are realized in a compact structure.

Cruciform Directional Couplers in E-Plane Rectangular Waveguide

This paper proposes a new type of compact waveguide directional coupler, which is constructed from two crossed e-plane rectangular waveguide with two metallic posts in the square junction and one metallic post at each port. The metallic posts in the square junction are set symmetrically along a diagonal line to obtain the directivity properties. The metallic post inserted at each input/output waveguide port can realize a matched state. Tight-coupling properties 0.79-6dB is realized by optimizing the dimension of the junction and the positions/radii of the posts. The design results are verified by em-simulator (Ansoft HFSS)

A design of multi-stage, multi-way microstrip power dividers with broadband properties

We investigate a design method of multi-stage, multi-way microstrip power dividers to construct a compact low-loss power divider with number of outputs. First, we describe an integration design technique of multi-way power dividers founded on the planar circuit approach in combination with segmentation method, and design broadband 3- and 4-way power dividers. Next, we successfully design a 9-way power divider consisting of 3-way dividers of two-stage structure using a similar technique. As a result, the fractional bandwidths of nearly 90%, 100%, and 85% are obtained, respectively. The validity of these design results is confirmed by HFSS and an experiment.

New composite right/left-handed transmission line using substrate integrated waveguide and metal-patches

A new Composite Right/Left-Handed Transmission Line (CRLH-TL) for millimeter wave frequency is proposed and investigated theoretically and experimentally. It consists of a Substrate Integrated Waveguide (SIW) with slit apertures and a dielectric film with metal patches. A prototype of SIW Metal-patch type CRLH-TL that satisfies the balance condition is designed. Dispersion diagram and S-parameters are derived numerically, and typical field distributions of RH and LH transmission and the zero-order resonance are shown. The experimental results of the proposed SIW Metal-patch type CRLH-TL agree the analytical results well. Because both the layers of the SIW and the metal-patched dielectric film compose simple planar periodic structure, the SIW Metal-patch type CRLH-TL has advantage of simple manufacturing. It is expected to be one of the basic structure of CRLH-TL or components such as leaky wave antenna and LH coupler above 10 GHz or millimeter wave frequency.

Broad-band cruciform substrate integrated waveguide couplers

This paper describes a method to broaden the bandwidth of cruciform substrate-integrated waveguide couplers. The design and the analysis of the couplers are performed using the H-plane planar circuit approach, and the frequency characteristics of the couplers designed at 24 GHz are shown. As a result, fractional bandwidths of 30% for a 3dB coupler and 16% for a 1.7dB coupler can be realized. The design results are verified numerically and experimentally.

Analysis of Post-Wall Waveguide by H-Plane Planar Circuit Approach

A waveguide whose side walls are formed of densely arranged metallic posts has been proposed and applied to antennas etc. for millimeter-wave. This paper suggests an analytical method of the post-wall waveguide or the substrate integrated waveguide by applying the analysis technique of the H-plane waveguide discontinuities based on the planar circuit approach. The analytical procedure consists of the derivation of the mode impedance matrices for regular-shaped circuits and short-circuiting fictitious ports arranged at the peripheries of the metallic posts. First, a straight section of the post-wall waveguide is treated as an example and the analysis method is described. Then the S-parameters of the guide are calculated. Next, the analysis method is applied to the design of a right-angled corner with an air post. The analysis and the design results are verified by an em-simulator (HFSS).

Design of Cruciform Directional Couplers in E-Plane Rectangular Waveguide

This paper proposes a new type of compact waveguide directional coupler, which is constructed from two crossed E-plane rectangular waveguide with two metallic posts in the square junction and one metallic post at each port. The metallic posts in the square junction are set symmetrically along a diagonal line to obtain the directivity properties. The metallic post inserted at each input/output waveguide port can realize a matched state. Tight-coupling properties 0.79 - 6dB are realized by optimizing the dimension of the junction and the positions / radii of the posts. The design results are verified by em-simulator (Ansoft HFSS).