Abstract: A wide-band distributed coupler for coupling rf energy from an input waveguide into a tapered interaction waveguide in a traveling-wave amplifier comprising a plurality of channel filters connecting between the input and interaction waveguides, with each filter coupled to the interaction waveguide at the appropriate cross-sectional position along its tapered length where the interaction waveguide cutoff frequency approximately matches the wave frequency propagated by the filter. Each filter comprises, in one embodiment, a main coaxial cavity tuned to a distinct center frequency, a first simple isolation cavity for coupling rf energy between the input waveguide and the main cavity, and at least one second simple isolation cavity for coupling energy between the main cavity and the tapered interaction waveguide. This coupler is compatible both in bandwidth and geometry with the tapered interaction waveguide.

Abstract: A high power amplifier for amplifying millimeter-wave radiation comprising: a length of metallic waveguide tapered from a small cross-sectional end to a larger cross-sectional end; a magnetron-type electron injection gun for injecting a spiral beam of relativistic electrons at the small end of the waveguide for propagation axially therein so that the wall radius of the tapered waveguide increases in the downstream direction of the electron beam; an input coupler for launching electromagnetic waves to be amplified into the waveguide at the large waveguide end thereof such that the individual frequencies in the input waves are reflected at various points along the constriction of the waveguide taper so that they copropagate with and are amplified by the electron beam; and a magnetic circuit for generating an axial magnetic field within the tapered waveguide with a unique profile approximately in accordance with the following equation to maintain synchronism: ##EQU1## where the z subscript is the waveguide axial direction, the ⊥ subscript designates the direction perpendicular to this axial direction, and the o subscript represents those quantities at the entrance point for the electron beam into the waveguide. This device has been found experimentally to have negligible launching loss and low sensitivity to electron velocity spread.

Abstract: We consider the problem of optimizing parallel stripe electrodes intended for influencing the refractive index of integrated optics waveguides that are embedded in electrooptic materials. In particular, such electrodes may be used for modulating the coupling efficiency of push-pull directional couplers or the phase of one of two orthogonal modes of a single waveguide. We show that an optimum electrode spacing exists for a push-pull directional coupler with fixed waveguide spacing. In addition, we discuss the optimum position for a single dielectric waveguide placed underneath a pair of stripe electrodes and show that it depends on the orientation of the optic axis of the electro-optic crystal and on the spacing of the electrodes.

Abstract: The stability of a relativistic electron layer inside a magnetron waveguide is examined. The dispersion relationship for the cyclotron maser/negative mass instability in this "gyromagnetron" device is derived, using a Pierce type analysis. The coupling constant e between the electron beam and the waveguide circuit is computed. Based on a study of ~, we design a proof-ofprinciple experiment for a gyromagnetron amplifier which operates at the sixth cyclotron harmonic, thereby reducing the magnetic field requirement by a factor of six. The operating beam voltage is relatively low. The problem of mode competition is examined, but is found to be not serious. The design procedure is described.

Abstract: We have formulated a model to calculate the mode size and propagation constant of single-mode titanium-lithium niobate diffused strip waveguides directly from controllable fabrication parameters and basic constants. The model is compared to measurements of the lateral and vertical mode width of Ti:LiNbO 3 waveguides for a variety of diffusion conditions. We show that the model accurately predicts the geometrical mean mode size of the two-dimensional waveguide. The model provides a simplified method for estimating the mode size and propagation constant of the guide, and is useful in designing waveguide devices having low fiber/waveguide coupling and bending losses.

Abstract: A formally exact solution is given for the problem of scattering at a circular-to-rectangular waveguide junction and at a thick diaphragm, with a centered circular aperture, in a rectangular waveguide. The method uses normal TE and TM mode expansions of the waveguide fields and traditional mode matching of the transverse electric and magnetic fields at the junction boundary. Exact closed-form expressions are obtained for the electric field mode-matching coefficients which couple the TE(TM) modes in the rectangular guide to the TE(TM) and TM(TE) modes in the circular guide. Numerical results are presented for the case of TE/sub 10/ mode propagation in the larger rectangular guide with all other modes cutoff. Convergent numerical results for the equivalent shunt susceptances of such junctions are obtained when about 12 modes (eight TE and four TM) are retained in the circular waveguide or in the circular aperture of the diaphragm. The results are graphically compared with formulas and curves due to the quasi-static theory of Bethe and the variational theory given in the Waveguide Handbook [2].

Abstract: Integrals arising in the Wiener-Hopf solution for wide microstrip antennas are approximated in closed form for the case of an electrically thin substrate. The resulting expressions are used to obtain simple, closed-form expressions for resonant frequency and unloaded radiation Q for rectangular microstrip patch antennas which are valid when commonly used quasi-static formulas no longer hold. Numerical comparisons show significant shifts in resonant frequencies as compared with existing theories.

Abstract: Gain was measured for fast and slow waves propagating in a dielectric-loaded T${\mathrm{E}}_{01}$ axi-symmetric waveguide penetrated by an annular electron beam. This measurement is the first reported in the slow-wave regime, where axial velocity modulation dominates the azimuthal bunching. Small-signal gain at 6.0 GHz of over 30 dB, instantaneous bandwidth of 3.7%, and tuning bandwidth of over 11% are reported. In a feedback-amplifier configuration gain of 53 dB, power output of 20 kW, and 10% electronic efficiency are also reported.

Abstract: A system and method for the controlled in situ heat processing of hydrocarbonaceous earth formations involves the application of electromagnetic energy at a selected frequency or at selected frequencies to a waveguide structure formed by electrodes bounding a particular volume of hydrocarbonaceous material. Terminating one end of the structure with different impedances at different times produces electric field standing waves of different respective phase at that end at a selected frequency. Two standing waves substantially 90° out of phase in formations having relatively uniform dielectric properties result in substantially uniform application of heating power if the product of the amplitude-squared of the electric field standing wave and dwell time is substantially the same in each of the two modes. Feeding the line at both ends provides partial offset for attenuation. Various desired controlled heating patterns other than uniform may be effected by utilizing different dwell times or applied fields. Different frequencies provide further flexibility, particularly where the line is terminated differently at the respective frequencies. Energy at the different frequencies may be applied simultaneously.

Abstract: A system for the detection of wing icing by monitoring variations in flexural waves transmitted through the outer plate material of an aircraft airfoil The flexural waves in the plate of the wing airfoil are more subject to variation from the accumulation of ice on the wing than the compressional waves The flexural waves are detected apart from the compressional waves, which tend to remain relatively constant, to provide an indication of icing Changes in amplitude, phase or dispersion characteristics of the flexural waves are detected to indicate ice buildup, and, in one embodiment, these values are ratioed to the corresponding levels in the compressional wave in order to provide compensation for variations other than ice buildup The ultrasonic waves may be coupled directly from a transducer to the airfoil plate or via an ultrasonic waveguide interposed between the transducer and the plate The receiver for the ultrasonic waves to be detected may be positioned to receive direct flexural waves transmitted over a distance through the plate or flexural waves reflected from reflecting boundaries in the plate

Abstract: An integrated optical temperature sensor requiring no electrical connection and consisting of a parallel array of unequal arm‐length waveguide interferometers in LiNbO3 has been designed and the key components have been demonstrated. The optical transmission of each interferometer varies sinusoidally with temperature with a period inversely proportional to the path length difference between the two arms. This device has a projected range and resolution of ≳700 °C and 2×10−3 °C, respectively, and would be particularly useful in applications requiring immunity to electrical noise.

Abstract: The gyrotron amplifiers in two slow wave structures, disc and helix-loaded waveguides, are investigated for wideband applications, For each structure, properties of the vacuum waveguide mode are examined in connection with the gyrotron application, and the gyrotron dispersion relation is obtained. For the disc-loaded waveguide, it is found that the group velocity of the waveguide mode can be easily varied by the disc parameters, and the gain and the bandwidth are at least comparable to those of the ordinary gyrotron. In the helix-loaded waveguide configuration, the gyrotron can be very broad in its bandwidth. Moreover, the hybrid mode operation, using the helix mode as a carrier, shows possibility of fast wave wideband amplification by contouring the waveguide.

Abstract: Wavelength multiplexers and demultiplexers using a chirped grating and an ion-exchanged multimode waveguide are presented. The waveguide is prepared by the electric-field-assisted ion-exchange technique, and the chirped grating is fabricated by the computer-controlled electron-beam writing technique. The device requires no collimating and focusing components and has the advantages of (1) high resolution, (2) large channel number, (3) small cross talk, (4) low insertion loss, (5) low loss coupling to multimode fiber, (6) compact and stable rugged structure, and (7) possibility of economical mass production. The design considerations and the fabrication process are described, and the demultiplexing characteristics of the fabricated device are discussed.

Abstract: Properties of the electromagnetic waves propagating through a helix‐loaded waveguide are investigated, including the important influence of the outer conducting wall on the dispersion properties. A closed algebraic dispersion relation for the eigenfrequency ω and the axial wave number k is obtained for arbitrary azimuthal harmonic number. It is shown that in the limiting case, where the outer conducting wall approaches close to the helix, this dispersion relation is reduced to three distinctive modes. These are the transverse electric mode, the transverse magnetic mode, and the helix mode, which can be further simplified to straight lines in the (ω, k) parameter space. Numerical investigation of the dispersion relation is also presented.

Abstract: A theoretical parameter study is given of a TE/sub 11/ to HE/sub 11/ mode converter consisting of a section of cylindrical corrugated waveguide with ring-loaded slots. The analysis, using modal field-matching techniques to determine the scatter matrix of the converter, allows the return loss to be computed accurately. For a wide range of waveguide sizes it is shown that a bandwidth ratio of 1.5 with a return loss better than 30 dB is possible. The low-frequency performance of the converter is limited by the deterioration in return loss, while at high frequencies the generation of a small amount of unwanted EH/sub 12/ mode is the restriction. If the effects of this mode can be neglected, operation over a wider bandwidth is possible, particularly for larger waveguide size.

Abstract: The gyrotron amplifiers in two slow wave structures, disc and helix-loaded waveguides, are investigated for wideband applications, For each structure, properties of the vacuum waveguide mode are examined in connection with the gyrotron application, and the gyrotron dispersion relation is obtained. For the disc-loaded waveguide, it is found that the group velocity of the waveguide mode can be easily varied by the disc parameters, and the gain and the bandwidth are at least comparable to those of the ordinary gyrotron. In the helix-loaded waveguide configuration, the gyrotron can be very broad in its bandwidth. Moreover, the hybrid mode operation, using the helix mode as a carrier, shows possibility of fast wave wideband amplification by contouring the waveguide.

Abstract: An electron beam driven dielectric‐lined waveguide has produced 30–100 kW of coherent radiation over an octave band on the TM01 mode of the waveguide. Operation of the TM02 mode has been realized as well. Impedance mismatches at the ends of the liner section provide a reflected signal, which undergoes amplification during successive passes.

Abstract: We report the first demonstation of electrical tuning of the center wavelength of waveguide electro‐optic TE〈–〉TM converter/filters. Using a novel dual electrode configuration the filter center wavelength is shifted by one filter bandwidth by application of a 10‐V tuning voltage.

Abstract: The mode indices of a waveguide are found as the poles of the reflectance in the superstrate or the substrate. Complicated boundary condition problems are avoided by using the recursion relations for the reflectance. The method is especially suited for computer waveguide design.

Abstract: CW operation of a 1.60 μm GaInAsP/InP buried-heterostructure integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide (BH BJB DBR integrated laser) was achieved at room temperature. Single longitudinal-mode operation at fixed mode was obtained in a temperature range of about 60 deg C, under the CW condition, and it was also maintained under rapid direct modulation of 1.6 GHz.

Abstract: Laser linewidth is controlled by reflecting a certain portion of the laser light back into the laser cavity. This control is accomplished by aligning the active layer on an electroabsorptive cell with the active layer of a semiconductor laser on a single substrate with a first waveguide therebetween. Light from the laser is guided by the first waveguide to the electroabsorptive cell whose light absorption is electronically controlled. The laser light propagates through the active region in the electroabsorptive cell and then is guided by a second waveguide to a reflection facet. The laser light is reflected by this reflection facet back through the waveguide-cell-waveguide-laser light path. The foregoing device can be formed using either a monolithic or a hybrid design.

Abstract: Crosstalk characteristics of an intersecting waveguide are presented. Two straight channel waveguides which intersect at an angle of a few degrees on y -cut LiNbO 3 were fabricated by in-diffusion of Ti. Experimental results show that the crosstalk characteristics are determined by the refractive index change profile and the geometry of intersection associated with guided wave modes. In a special case, a TE/TM mode splitter was obtained by using the intersecting waveguide which provides adequate anisotropy by the change in refractive indices. Splitting ratio was 17 and 14 dB for the TE and TM modes, respectively.

Abstract: It is shown that for polar regions, where the conductivity is predominantly reactive, the wave functions for the transverse electromagnetic mode of the earth-ionosphere waveguide are Hankel functions of the first kind with real argument; therefore they extend up to large heights over the polar ionosphere. A Green's function for the excitation of the waveguide by extended current or field sources in the ionosphere is obtained for an exponential ionosphere. The potential of ELF waveguide excitation by wireless antennas is discussed.

Abstract: Slow-wave characteristics of a coplanar waveguide with substrate resistivity are analysed using the mode-matching technique. This waveguide is suitable for microwave monolithic integrated circuits because of its coplanar configuration. Numerical results are presented and compared with an experimental measurement in the literature.

Abstract: Point‐contact Josephson junctions with a submicron contact diameter have been used as high‐frequency mixers (170–220 GHz) under high thermal background conditions. The junction is formed across a full height (0.56×1.06 mm2) waveguide between a 3–5‐μm thick Nb whisker and a 0.2‐mm diam Nb center conductor of a coaxial line. The best single‐side band mixer‐noise temperature that was measured is 165 K (± 25%) with a corresponding single‐side band conversion efficiency of 0.36±0.03 (a loss of 4.5 ±0.4 dB) at a signal frequency of 185 GHz, including losses in the coupling horn and the waveguide. The performance was measured with the hot‐cold source technique. The effects of nonheterodyne response in that situation were investigated in detail. The junctions have been operated in a coherent receiver that can be used on a telescope with only small adaptations. The instantaneous bandwidth of the receiver is about 20 GHz.

Abstract: : Open circular waveguides are used to model jet engine inlets. The exact Wiener-Hopf solution for scattering by a semi-infinite cylinder is studied in the resonance region, where the cylinder diameter is of the order of a wavelength. In particular, the Wiener-Hopf factorization functions are calculated by numerical integration and compared to various approximations, to define regions of validity. Scattering from the rim is studied as a function of frequency, incidence angle, and time. A ray-optic model for rim backscatter is discussed. The relative power absorption of the five lowest order waveguide modes is evaluated. Coupling of incident plane waves to waveguide modes, and radiation by these modes are shown to be related by reciprocity. The waveguide termination model for a jet engine assumes an incident waveguide mode strikes an axially symmetric cone on a flat plate. The various techniques for evaluating scattering by this structure are discussed, and the problem is solved for a few cases. (Author)

Abstract: A nonreciprocal traveling-wave resonator critically coupled to a waveguide becomes an isolator with high isolation. The dielectric image-line isolator with a magnetized ferrite pillbox as the nonreciprocal traveling-wave resonator is described. The validity of the theory is verified by experiments earned out at the 50-GHz range. The theoretical and experimental estimations of the coupling coefficient between a pillbox resonator and a straight dielectric waveguide are also included.

Abstract: We report a fibre-coupled Ti: LiNbO3 directional coupler modulator with total fibre-device-fibre insertion loss as low as 1.5 dB for λ=1.32 μm. Low loss has been achieved by using diffusion parameters to give good mode match to the fibre and low propagation loss, an effective SiO2 buffer layer to eliminate electrode loading loss and a directional coupler geometry which minimises the effect of bend loss.