Waveguide Reflection Research Articles

Waveguide type power combining amplifiers

AbstractThis paper is concerned with the waveguide power combining amplifier of reflection type and of transmission type. The structure of the waveguide reflection type power combining amplifier consists of an IMPATT diode (to be called the active element) under a post at the center of the waveguide and of a shorting plunger. At the distance Z in front of the active device, another active device is placed under a post and an inductive window is located at Z in front of this second device. On the other hand, the transmission type (power combining) amplifier consists of an active device under a post located at Z from an inductive window. Another device is placed under a post at Z further down the waveguide and an exit inductive window at Z from the second device. The waveguide height of the two amplifiers are 3 mm for which the stability condition is satisfied for the amplifier. Tapered sections are installed from the reduced height waveguide to standard waveguides.The equivalent circuits of the two amplifiers have been derived from the electromagnetic field equations. The experiment of the power combining amplifiers have been performed at the 10‐GHz range. The output power is 2.5 mW to 103 mW when the input power was changed from 0.5 mW to 20 mW. The calculated results from the equivalent circuits agree well with the measured data.

The influence of waveguide reflections and system configuration on the performance of an active noise attenuator

Reflections of sound from waveguide terminations can play a major role in the performance of a random noise active attenuator. Their influence depends on the direction reflections propagate along the waveguide and on the configuration of the attenuator. Upstream and downstream reflections are therefore important parameters to be considered when choosing the configuration best suited for a particular application. Theoretical and experimental results are presented, showing that waveguide reflections interact with other major parameters of a random noise attenuator.

InGaAsP/InP waveguide grating filters for λ=1.5 μm

We report the first demonstration of InGaAsP/InP passive waveguide reflection grating filters. Waveguide filters with ∼1.5-μm center wavelength, peak reflectivity >99%, and spectral bandwidths (full width at half-maximum) as narrow as 6 Å and as broad as 130 Å have been achieved.

Characterization of a Dual-Mode Horn for Submillimeter Wavelengths (Short Papers)

A simple dual-mode conical horn has been developed and tested at 0.5, 1.4, 3.1, and 34.2 mm. The horn has nearly equal beam shape in the E and H plane far field patterns with a 3-dB half angle of 6°. At 34.2 mm, the waveguide reflection loss and the phase center have been determined.

Analysis of optical waveguide junctions by means of an integral equation method

AbstractUsing a slab waveguide model we analyze the problem of waveguide mode transmission and reflection that occurs at the junctions of dielectric optical waveguide due to lateral offset, angular tilt, and gap between the guides, and deformations of the end faces. the analysis first develops a set of integral equations for the unknown equivalent electric and magnetic surface currents over the end faces. the integral equations are discretized through partitioning of the boundaries of both ends into small elements, and their solutions are expanded in a Neumann series, which makes it possible to obtain the solutions iteratively. Using reciprocity and mode orthogonality properties appropriately, the mode coupling coefficients are obtained. After discussing the relation between partition number of the boundaries and convergence of solutions, and the satisfaction of energy relations, we give numerical examples for the reflection and transmission coefficients of guided modes, the radiation losses and the radiation power patterns, choosing end shapes and their locations as the parameters.

Measurement of the Dielectric Constant and Loss Tangent of Thallium Mixed Halide Crystals KRS-5 and KRS-6 at 95 GHz

The dielectric constants and loss tangents of KRS-5 and KRS-6 thallium halide mixed crystals have been measured at 95 GHz using both the shorted waveguide (SWG) reflection method and the Fabry-Perot (F-P) transmission method on samples filling standard WR-10 waveguide. The results--KRS-5: epsilon'/sub r/ = 31; tan delta = 1.8 x 10/sup -2/; KRS-6: epsilon'/sub r/ = 29, tan delta = 2 x 10/sup-2/-- agree reasonably well with a simple theoretical fit to the far-infrared Iattice absorption of TIBr and TICI centered at about 1400 GHz. The dielectric samples were hot-pressed into copper wafers with dimensions matching WR-10 waveguide, and then machined and polished to obtain flat, parallel air-dielectric interfaces.

Characteristics of a hollow-core distributed feedback CO2laser

Using perturbation theory and a plane wave analysis, the scattering amplitudes and coupling coefficients for a planar, hollow-core, double grating distributed feedback (DFB) waveguide laser are derived. Waveguide reflectivity has been compared for a single and double grating waveguide configuration. For a waveguide dimension of 100 μm over a 10 cm length, reflectivity is enhanced from 75 percent for a single grating to 98 percent using a double grating configuration. Included in this analysis is the effect of phase relationship between the two gratings. Using this analysis a means has been devised whereby reflectivity of the DFB waveguide may be optimized during operation of the laser. With the double grating configuration, coupling is enhanced such that a greater plate separation is possible in nearly all cases. Use of a double grating allows the plate separation of the waveguide to be increased from 80 to 100 μm, reducing total waveguide loss from 15.9 to 8.1 dB/m. These results have led to a method of solving heretofore prohibitive characteristics of single grating hollow-core DFB waveguides. Formal relationships for the waveguide parameters where a double grating configuration is used have been presented for designing hollow-core DFB waveguide lasers operating at 10.6 μm.

Waveguide array excitation of lower hybrid fields in a tokamak plasma

The launching of RF waves from a two- and four-waveguide array is studied. From Brambilla's grill theory, analytic expressions for the reflection coefficients, the power spectrum and the fields in the slab model of a cold inhomogeneous plasma are derived. As a first approximation to the coupling problem, only the fundamental mode in the waveguides is considered, the fast wave in the plasma is neglected and the density profile near the plasma edge is assumed to be linear. It is shown that for a fourwaveguide array with alternate 0, π phases, optimum coupling is obtained when the inside waveguides carry about four times the power of the outside ones. This reduces and equalizes the waveguide reflection coefficients and avoids excessive shifts of the penetrated power spectrum to low values of the wavenumber parallel to the magnetic field.

Simple waveguide reflection maser with broad tunability

The design and performance of a simple two-stage reflection maser for use between 9 and 10 GHz are described. The maser is used to improve the sensitivity of a transmission electron spin resonance spectrometer. A ruby-filled waveguide structure permits broad tunability and straightforward construction. All microwave components except the ruby section are at room temperature.

Circular waveguide method for measuring reflection properties of absorber panels

A technique is developed for direct determination of the plane wave reflection properties of plane layered media. The approach is applicable for media containing a high-index absorber layer. A circular waveguide aperture is used to measure the near field scattering from the external medium. The analytical development results in a set of Smith chart contours from which the reflection properties of the medium can be determined from the measured waveguide reflection coefficient. The approach is demonstrated with measurements of a ferrite absorber panel.

Standard mismatch - the production of controlled small reflections in waveguides

Standard mismatch - the production of controlled small reflections in waveguides

The Schwinger Variation Method

Abstract : The Schwinger variation method is removed from its customary setting in Green's function theory, and is approached from the integral equations viewpoint. The traditional Schwinger theory is improved upon in two respects. Error bounds are provided for the approximations to A(f), a function determining waveguide transmission and reflection coefficients due to diaphragms containing windows. A method, involving quadratures only, is provided and will improve the accuracy of this approximation as much as desired.

A technique for the continuous indication of waveguide reflection coefficient, impedance or admittance

Apparatus is described which yields a continuous indication of the complex reflection coefficient of a waveguide component, presented in the form of a cathode-ray tube display. The indication is derived from the simultaneous observation of the standing-wave pattern at three or more suitably spaced points by means of a multiple-detector arrangement. A special bolometer element has been developed for this purpose.The equipment is particularly useful for the rapid measurement of v.s.w.r. values close to unity, the accuracy attainable being of the same order as that of a good-quality slotted-section standing-wave indicator.The only specialized microwave component used is the multiple-detector section, a relatively simple and inexpensive unit. Any one detector section may be used over a ±20% range of guide wavelength and the display unit does not require modification.

Problems and practice in the production of wave-guide transmission systems

The magnetron, considered as an h.f. generator, exhibits peculiar forms of frequency instability which lead to specific wave-guide performance requirements. Some considerations of reflections in wave guides and of probability functions show the difficulties in the way of meeting these requirements. In order to achieve consistent success, the random choice or interchange of wave-guide sections or components must be abandoned in favour of selection or production matching when the number of sections or reflections is more than two or three. The two procedures may be complementary or alternative.The realization of these features has led to an intensive development of general wave-guide manufacturing practice and has guided the measurement of sequences of different wave-guide assemblies which give a very satisfactory performance for magnetron working.