Abstract: An efficient method for calculating the dispersion characteristics of planar waveguide structures is presented, of which the principle is known as the ‘method of lines’ in mathematical literature The wave equation is discretized in only one direction, and the resulting differential-difference equation can be solved analytically As an example of application the phase constant and the characteristic impedance of microstrips with tuning septums are calculated

Abstract: Using a dielectric‐lined waveguide in combination with a relativistic electron beam, we are able to produce 1 kW of Cerenkov microwave radiation. We have observed the dependence of the output microwave frequency on the beam voltage. In addition, we have detected microwave radiation in excess of 150 GHz, corresponding to higher‐order mode interaction.

Abstract: Normal mode expansions are used to mode match the tangential electric field at the transverse junction of two cylindrical waveguides. Instead of mode matching the tangential magnetic field the principle of conservation of complex power is invoked and leads, without a matrix inversion, to an expression for the junction's input admittance matrix, as seen from the smaller guide. Simple matrix algebra and the reciprocity theorem then provide the generalized scattering matrix of the two-port (with higher order modes included). It is also shown that the solution satisfies the continuity condition for tangential magnetic field in the junction's aperture. Numerical results are given for parallel plate waveguides with TEM, TE/sub 1/, and TM/sub 1/ incident fields, numerical convergence being achieved with about ten modes in the smaller waveguide.

Abstract: : Dielectric properties have been measured at 94 GHz for thallium halide materials KRS-5 and KRS-6 using Fabry-Perot resonance transmission and short-waveguide reflection in dielectric-filled waveguide section The dielectric constants are 31-32 for KRS-5 and 28-31 for KRS-6; the loss tangents are 02 for both These values predict a waveguide loss of 8 dB/cm for a closely-confined HE sub 11 mode in KRS-5 at 94 GHz Difficulties in coupling to such high dielectric constant fibers have so far prevented direct measurement, but scale model studies at 10 GHz yield a successful coupling technique to the HE sub 11 mode through an intermediate dielectric Propagation in a 05 mm diameter KRS-5 fiber was observed with 02 dB/cm loss, much lower than that predicted for HE sub 11; the as-yet unidentified mode has a phase velocity about c, but small external fields and less than 15 dB loss from a 90 deg, 20 cm radius bend Propagation constants for KRS-5 waveguides were calculated and losses estimated for various designs A loosely coupled HE sub 11 KRS-5 fiber with foamed-teflon cladding could exhibit 3 dB/meter loss, with 3 dB/meter additional loss from 60 cm radius bends A simple theory of relative guiding properties for multilayer cylindrical waveguides is given (Author)

Abstract: We present the concept of an ultra-wide-band distributed gyrotron traveling-wave amplifier for millimeter and submillimeter waves. The radius of the waveguide in the interaction region is increased along the axis, while the strength of the dc magnetic field is decreased in such a way that the wave cutoff frequency is kept nearly equal to the electron cyclotron frequency. The basic principle of operation, peak gain, and saturated efficiency are analyzed. It is shown that instantaneous bandwidth over at least two octaves is theoretical possible. Technological requirements for achieving such an amplifier are assessed, including proposed structures for distributed input wave coupling.

Abstract: The reflection and the scattering properties of even TE and TM surface waves incident in an abruptly ended dielectric slab waveguide are analyzed. The discontinuity is regarded as a junction between two open waveguides namely the dielectric slab waveguide and the free space waveguide. The boundary conditions acting together with the orthogonality provide singular coupled integral equations on the discrete and the continuous wave amplitudes at the discontinuity. These singular coupled intergral equations with Cauchy kernels and infinite limits of integration are solved by iteration via the Neuman series. Numerical results are presented for the reflectivity of the even TE/sub 0/ and TM/sub 0/ fundamental modes, together with their mode conversion on even TE/sub 2/ and TM/sub 2/ in a slab where two guided modes can propagate. Reflectivity and mode conversion of higher order excitations are also investigated

Abstract: The generation of high‐power bursts of microwave radiation from hollow, relativistic E layers injected through a cusped magnetic field into a magnetron‐type conducting boundary configuration has been studied experimentally. Using a 2‐MeV, 2‐kA, 5‐ns injected beam pulse, approximately 250 MW of radiated power have been generated at 9.6 GHz.

Abstract: This investigation concerns a TEM wave obliquely incident onto the open end of a parallel plate wave guide with a truncated upper plate. The lower plate as well as the dielectric slab between the two plates is assumed to extend out indefinitely in order to support the propagation of at least one surface wave mode. Reflection from the wave guide opening is determined as a function of incident angle via a dual Wiener-Hopf formulation. It is found that total reflection, i.e., a reflection coefficient with magnitude equal to unity, is possible for incident angles greater than the critical angle associated with the lowest-order surface wave mode of the grounded dielectric slab. The field external to the parallel plate wave guide in this case becomes completely evanescent in the cross-sectional plane perpendicular to the plane of incidence, which is determined by the propagation direction of the incident wave and the edge of the upper plate. It is shown that the phase of the reflection coefficient thus obtained can be used to construct the modal equation for the fundamental mode(s) of a wide microstrip.

Abstract: We report the separate TE01 and TE02 operation of a CO2 laser in a hybrid oscillator formed by placing a circular metallic waveguide and a focusing lens inside the cavity of an otherwise conventional laser. With the TE01 output focused into a passive waveguide outside the cavity, transmission in excess of 90% has been measured through a 31‐cm‐long, 0.5‐mm‐i.d. straight metallic tube. Bending increased the losses far more than originally anticipated.

Abstract: The results and interpretation of the modest-power (~90 kW) lower-hybrid-heating experiment on Alcator A are presented. The expected results from linear waveguide-plasma coupling theory are outlined, and the possible effects of parametric instabilities, scattering from density fluctuations, and imperfect energetic ion confinement are addressed. It is found experimentally that good coupling and the absence of RF breakdown are achieved with a double waveguide array at available RF power densities PRF ≤ 4.5 kW.cm·−2, the waveguide vacuum windows being outside the toroidal field magnets; a waveguide array having vacuum windows near the waveguide mouth so that the ω = ωce layer can be pressurized shows no breakdown at PRP > 8 kW/cm2 when a single waveguide is energized. Energetic ion production and a factor-of-50 increase in the fusion neutron rate are observed to take place at well defined values of central plasma density; below these densities electron heating occurs. The ion tail production is found to be independent of the relative phase of the double waveguide array employed. This ion heating occurs at a lower density than theoretically expected; together with the electron heating this indicates waves having n|| ~5 being absorbed near the plasma centre. Probes at the plasma edge observe a frequency-down-shifted and broadened RF pump signal that is strongly attenuated as the plasma density increases through the neutron production band. These anomalous heating results and probe signals can be explained by a parametric decay of the pump wave into higher n|| lower hybrid waves near the plasma edge. An alternate qualitative explanation would be the poloidal scattering of the lower hybrid waves at the plasma periphery due to density fluctuations; the n|| of the scattered lower hybrid waves would then increase as they propagated inward because of magnetic shear. The neutron rate decay times imply that the RF creates ion tails having a substantial fraction of their energy above 50 keV. The neutron decay times and rates strongly depend on plasma current and indicate the expected influence of ion confinement on RF heating efficiencies. Finally, the RF heating efficiencies are assessed.

Abstract: A line-source excited parallel plane waveguide with perfectly conducting or surface impedance walls is investigated in the high frequency range where alternative field representations involve many rays or many modes. It is shown that a hybrid ray-mode field representation can be developed whereby the truncation remainder of a mode series can be expressed in terms of ray fields or, conversely, the truncation remainder of a ray series can be expressed in terms of guided modes. A great variety of appropriate ray-mode combinations, each determined from a physically well-founded criterion, is possible: with respect to propagation angles measured at the source, the retained modes are those whose characteristic plane wave propagation angles fill the void left by the truncated ray series and vice versa. The analysis thus clarifies and quantifies the intimate relation between a bundle of rays and a corresponding bundle of modes. The accuracy of various ray-mode mixtures, and computational simplifications gained thereby, are illustrated in several numerical examples covering different parameter ranges, with the conventional guided mode series serving as a reference solution.

Abstract: A high speed optical sampler is proposed that is driven by cw microwaves. The sampler is composed of waveguide interferometers of the type originally proposed by Martin. A voltage applied to one (or both) arms of the interferometer modulates the interference of the optical radiation at the output. Such an interferometer can be driven at high frequencies if synchronism is maintained between the optical radiation and the applied voltage pattern. Spatially periodic exciting structures can serve this purpose. Deviations from synchronism can be compensated (within limits) by adjustment of the peak amplitude of the microwave voltage. A cascade of four interferometers on LiMb03, driven at 10 GHz, at multiples of (appr.) 3V (3, 6, 12, 24) have a predicted sampling-function width of 2 ps at 20 GHz repetition rate. Experiments on single section and double-section interferometers will be reported.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: A device for scanning a beam spot. The device has a light deflecting portion and a light condensing thin film lens formed on a thin film waveguide path. In this device, a chirped signal is applied to a surface elastic wave transducer constituting the light deflecting portion, whereby scanning of the beam spot is effected on or near the curved end surface of the thin film waveguide path. This device is very compact and capable of high-speed scanning.

Abstract: A very compact light beam scanning system is provided by utilizing the optical integrated circuit technique. A Luneburg lens of As 2 S 3 and a SAW transducer device are provided on a waveguide and a wideband heterodyning RF oscillator including two varactor tuned oscillators and a digital linearization circuit are provided as the drive circuit for the transducer device.

Abstract: The planar waveguide Bragg lens and a component utilizing a planar waveguide Bragg lens with a greater acceptance angle characterized by several grating structures being arranged in series and having an inclination towards one another for varying angles of incidence. In one embodiment, each of the grating structures are circular arc segments which are interconnected together to form a single grating structure having curved segments which also has a greater acceptance angle than a conventional planar waveguide Bragg lens.

Abstract: A simple scheme is proposed for the construction of a wide-band fast wave gyrotron travelling wave amplifier. The key features of this scheme include a contoured waveguide, a tapered magnetic field, and injection of input signals in opposite direction of the streaming electrons. Bandwidths at tens of percents, and gain at tens of decibals, are projected.

Abstract: A novel GaAs monolithic integrated circuit mixer has been fabricated which is impedance matched to fundamental waveguide. It consists of a slot coupler, coplanar transmission line, surface-oriented Schottky-barrier diode, and RF bypass capacitor monolithically integrated on the GaAs surface. At 110 GHz, a monolithic mixer module mounted in the end of a waveguide horn has an uncooled double-sideband (DSB) mixer noise temperature of 339 K and conversion loss of 3.8 dB.

Abstract: A graphical method for determining the size of a resonant rectangular microstrip patch for a specified frequency is given. Using an expression obtained from the reflection coefficient of a transverse electromagnetic (TEM) wave in a semi-infinite microstrip patch, the resonance condition of a given mode for a patch of finite size is derived in a manner analogous to that of a rectangular, waveguide cavity. Radiation is shown to be in the form of both surface waves and space waves and is dependent on the angles of incidence for waves impinging onto the edges of the patch. By varying the aspect ratio, it is also possible to modify the Q factor of a resonant path. Analytical expressions for the resonant frequency and the Q factor are then derived under the assumption of a very thin substrate slab, encountered frequently in the application. Design curves in the form of the "Argand diagram" are then presented for microstrip patches with fixed aspect ratios.

Abstract: We derive the modes inside a cylindrical waveguide of finite surface impedances, assuming the waveguide transverse dimensions are large compared to the wavelength λ. This paper restricts its consideration to the modes with β e k, where β is the propagation constant and k = 2π/λ. For these modes we show that asymptotically, for large values of k, the field ψ becomes infinitesimal (of the same order of 1/k) at the boundary. Taking this into account, we obtain simple expressions for the asymptotic properties of ψ for large k. The theory applies to a variety of waveguides: corrugated waveguides, optical fibers, waveguides with smooth walls of lossy metal, and so on. An important property of the modes considered here is that their attenuation constant is very low, ie., asymptotic to 1/k2 for large k. Thus, these modes are useful for long-distance communication. Another consequence of ψ → 0 at the boundary is that for large k the distribution of ψ inside the boundary is essentially independent of the boundary parameters, i,e., independent of the surface impedances in the longitudinal and transverse directions. This consequence implies that the same radiation characteristics of the corrugated feed can be obtained using other structures and, therefore, construction can be simplified in many cases, with little sacrifice in performance. We also derive general expressions for ψ and the propagation constant β.

Abstract: The paper describes the behaviour of a multimode corrugated feed for use in monopulse radar. Four square input waveguides are used to excite sum-and difference-channel modes. With appropriate choice of parameters it is possible to generate radiation patterns with low crosspolarisation thus allowing the polarisation characteristics of a target to be obtained. The results of an anlysis of the relevant waveguide discontinuity problem are presented and a means to compensate phase differences between modes is also described. Some preliminary experimantal results are found to be in accord with theory.

Abstract: The effect of broadening the bandwidth with a dielectric load in a cylindrical gyrotron is investigated for a hollow electron beam. The linear dispersion relation for the azimuthally symmetric, transverse electric (TE) modes is obtained by the method of the wave impedance matching. It is found that the TE perturbations exhibit three unstable modes characterized by their phase velocities vph : one fast wave, the long wavelength mode (LWM, vph ≳c), and two slow waves, the intermediate (IWM, c≳vph ≳ce−1/2) and the short (SWM, vph