A theoretical analysis is presented for the radiation characteristics of a dielectric slab waveguide periodically loaded with thick metal strips. A boundary-integral-equation formulation is employed to describe the fieIds in the grating layer. Through numerical calculations, we show that the leakage constant of the fundamental TM mode is much larger than that of the fundamental TE mode. This property will find application in mode filters for millimeter- and submillimeter-wave integrated circuits.

Radiation Characteristics of a Dielectric Slab Waveguide Periodically Loaded with Thick Metal Strips

The transmission characteristics of rib waveguides are examined in the submillimeter-wave region at Lambda/sub 0/ =337 µm. A number of miniature polyethylene rib waveguides are fabricated by means of a die-cast technique. The mode launching into such a waveguide is performed by focusing a laser beam directly on the end face of the waveguide, while the transmitted power is detected at any point on a waveguide through a movable grating coupler which can couple selectively with one of propagating modes. The measured phase constants show good agreement with the theoretical ones calculated by our analytical method, while the attenuation constants, typicafly alpha lambda /sub 0/ = 4.5 X 10/sup -3/ are found to be about 1.8 times as much as theoretical ones. Finally, the good confinement of fields in the rib portion is proved by means of two simple methods.

Submillimeter Guided-Wave Experiments with Dielectric Rib Waveguides

The refractive index of dielectric sheet materials (polystyrene, polypropylene) and of paraffin is measured at mm-wave frequencies using the specimens as dielectric slab waveguides. The mode wavelengths are measured in the evanescent field outside the slab of monomode and two-mode waveguides in which stationary interference patterns of modal fields are generated. The accuracy of the method is about 0.5%.

Quasioptical millimeter-wave measurements: Refractive index of thin plates

The transmission characteristics of dielectric rib waveguides are analyzed by the approximate mode matching method and their experiments with newly developed techniques confirm the validity of our analysis. Moreover, a more advanced method in consideration of the coupling between TE and TM modes is discussed.

An Approximate Analysis of Rib Waveguides

In this paper, a tube-contacted slab dielectric waveguide for millimeter waves is proposed, and a theoretical analysis and experiments are performed to determine the propagation characteristics. This waveguide consists of a dielectric tube with its radius larger than the wavelength, placed on a guiding film. The guided wave energy is concentrated near the contact point between the tube and the film. Since the tube is easily bent due to its structure and the field distribution is similar to Gaussian, the structure can be used as a low-dispersion flexible dielectric waveguide. Also, since the tube radius is larger than the wavelength, the waveguide can be used for high power transmission. The effective dielectric constant method has been used for analysis, and the field distribution and the phase constant have been computed. A waveguide has been fabricated for 35 GHz and the field distribution, propagation loss, guide wavelength, the field distribution at a bend and the bending loss have been measured. Measured results of the field distribution, guide wavelength and bending loss have agreed well with theoretical predictions. The propagation loss is 1.52 dB/m. In addition to the bending loss, variations of the field distribution at the transition from the straight guide to the bend have been measured. Based on these measured results, it is shown that the waveguide can be used for low-dispersion flexible transmission line or for high power transmission.

Tube-contacted slab dielectric waveguide for millimeter waves

The attenuation constants of a symmetric polyethylene slab waveguide are measured in the submillimeter-wave region at lambda/sub 0/= 337 mu m. In our experiments the fine metal grating is used as a coupler, instead of a usual prism coupler. Our coupler which is different from the conventional grating coupler fixed on a slab is easily movable along a slab without a fluctuation in the coupling efficiency, and the loss measurement is successfully performed for several kinds of slab thicknesses by using such couplers. As a result, the attenuation constant of about 1.3 dB/m is measured, in good reliability, for a slab of 10 mu m in thickness. Finally, to make clear the accuracy of our loss measurements, the transverse broadening of the field along the propagating direction of a slab is measured experimental!y, and it is concluded that there is little influence of the transverse broadening on the measured attenuation constants.

http://ieeexplore.ieee.org/iel6/22/25070/01129755.pdf

Ml Kio Tsuji

Papers

Sub)millimeter Guided-Wave E:~periments with Polyethylene Slab Waveguides