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Microwave Theory and Techniques, IEEE Transactions on

Issue 7 • Date Jul 1987

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Displaying Results 1 - 14 of 14
  • [Front cover - Jul. 1987 [T-MTT]]

    Page(s): f1 - f2
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    Freely Available from IEEE
  • Patent abstracts

    Page(s): 676 - 679
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    These patent abstracts of recently issued patents of interest to microwave engineers are intended to provide the minimum information necessary for readers to detennine if they are interested in examining the patent in more detail. Complete copies of patents are available for a small fee by writing: U.S. Patent and Trademark Office, Box 9, Washington, DC, USA. View full abstract»

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  • [Back cover - Jul. 1987 [T-MTT]]

    Page(s): b1 - b2
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    Freely Available from IEEE
  • Thermal Lowering of the Threshold for Microwave Breakdown in Air-Filled Waveguides

    Page(s): 653 - 656
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    It is demonstrated that the presence of absorbing inhomogeneities in an air-filled microwave waveguide may significantly lower the threshold for microwave breakdown. The underlying physical mechanism is locally enhanced microwave absorption and subsequent heating of the waveguide air. The results provide an explanation of the fact that break-down thresholds of microwave transmission systems are observed to be much lower than theoretical predictions. View full abstract»

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  • Analysis of Nonreciprocal Coupled Image Lines

    Page(s): 629 - 635
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    The effective dielectric constant method is used to analyze the nonreciprocal coupling properties of coupled image lines separated by a Iongitudinally magnetized ferrite slab. Two structures are considered, one incorporating low-dielectric-constant image lines (epsilonr = 2.56), the other incorporating image lines consisting of high-dielectric-constant material (epsilonr = 9.8). Results of dispersion characteristics, coupling parameters, and field distributions are presented. View full abstract»

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  • MMIC 14-GHz VCO and Miller Frequency Divider for Low-Noise Local Oscillators

    Page(s): 657 - 662
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    An MMIC voltage-controlled oscillator and an MMIC frequency divider are developed and applied to a 14-GHz low-noise local oscillator. To obtain both wide tuning range and low pulling figure, the source-follower FET circuit is used in the voltage-controlled oscillator. A wide-band balanced mixer and a filtering amplifier are integrated in a single chip and constitute the Miller frequency divider. -The MMIC's were assembled into a 14-GHz phase-locked loop in order to demonstrate that they will operate as key components of low-noise oscillators. It is shown experimentally that even for low-Q MMIC circuitry, the carrier noise of the oscillator is reduced enough for practical purposes such as space-borne heterodyne receivers, transmitters, and radio repeaters in Ku-band satellite communication systems. Thus, prospects are bright for development of single-chip microwave low-noise oscillators. View full abstract»

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  • Two Methods for the Measurement of Substrate Dielectric Constant

    Page(s): 636 - 642
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    Two methods for the accurate and convenient measurement of the dielectric constant of a microwave substrate are proposed. Both methods use the precision measurement capability of the HP-8510 Network Analyzer system and a rigorous theoretical analysis of multilayer transmission lines [6], and hence can also be used for the measurement of the frequency dependence of the relative dielectric constant. Accuracy on the order of 1.0 percent can be obtained by use of these techniques. Measurements were done for various substrates and gave results as predicted. View full abstract»

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  • Spectral-Domain Analysis of Single and Coupled Cylindrical Striplines (Short Papers)

    Page(s): 672 - 675
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    A spectral-domain technique for finding the characteristic impedances of a single cylindrical stripline and a coupled pair of cylindrical striplines is presented. Assuming a charge distribution on the strip, the variational expression for the line capacitance for single cylindrical strip-Iine is derived. Good agreement with published results is obtained. The cylindrical coupled strip and microstrip lines are also analyzed and a comparison with their planar counterparts is made. View full abstract»

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  • Characteristic Impedance and Effective Permittivity of Modified Microstrip Line for High Power Transmission

    Page(s): 615 - 620
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    In a quasi-TEM approximation, the calculation of the characteristic impedance and effective permittivity of a modified microstrip line with the upper strip conductor edges turned up from the substrateis presented. Both these theoretically derived quantities are compared with experimental values. To further facilitate the analysis and synthesis of the modified microstrip line, closed-form approximations to the characteristic impedance and effective permittivity have been found containing elementary functions only. The modified microstrip can be used in the construction of lines capable of transmitting high power on substrates having high loss factor and low thermal conductivity, for example, on low-cost plastics. View full abstract»

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  • Analysis and Design of MESFET Gate Mixers

    Page(s): 643 - 652
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    A general and efficient nonlinear/linear analysis of MESFET gate mixers is presented. In the nonlinear analysis, the Newton-Raphson algorithm is used in conjunction with a novel approach for computing partial derivatives required by the Jacobian.The study of conversion gain and stability characteristics of the mixer is based on S-parameter matrix theory. As a result of the analysis, the possibility of improving the conversion gain of X-band MESFET gate mixers by an appropriate choice of the RF drain termination has been theoretically and experimentally demonstrated. View full abstract»

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  • Design of Broad-Band Dielectric Waveguide 3-dB Couplers

    Page(s): 621 - 628
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    It is shown how 3-dB couplers with bandwidths on the order of 30 percent can be designed by appropriately taking advantage of the dispersion and the frequency dependence of coupling per unit length between two dielectic waveguides with asymmetrical cross sections. Theoretical methods for computing frequency responses of such couplers are discussed. It is shown how the phase response can be simply compensated to give approximately symmetrical-coupler-type or "magic tee" coupler-type phase-difference responses over comparable bandwidths. Experimental results confirming theoretical calculations are presented. View full abstract»

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  • An Investigation of Parametric Noise in Millimeter-Wave IMPATT Oscillators

    Page(s): 663 - 671
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    The IMPATT oscillator used as an LO source in a receiver has often been found to contribute a large amount of excess noise to the system (sometimes more than 40 dB compared to a klystron). Often the IMPATT noise has been referred to as avalanche noise, but theoretically this should only reduce the carrier-to-noise ratio by 10-15 dB when compared to a klystron. In the following paper, we show that the excess noise far from the carrier frequency (i.e., sideband noise) is much more dependent on parametric oscillations excited below the cutoff frequency of the mount than, on avalanche noise. By modifying the Hines equation for parametric stability, we have been able to investigate the parametric noise properties of realistic millimeter-wave IMPATT oscillators. Using theoretical waveguide models, we have investigated how the sideband noise depends on various mount configurations, avalanche currents, and IMPATT diodes, The calculated curves show good correlation with the measured noise at 4 GHz from the carrier. It often has been found to be very difficult to completely reduce the parametric noise in avalanche oscillators. In these cases, the method of comparison between different mounts presented here for finding the diode-mount configuration which gives least parametric noise can be an aid in the construction of low-noise IMPATT oscillators. View full abstract»

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  • Characteristics of Metallic Waveguides Inhomogeneously Filled with Dielectric Materials with Surface Plasma Layers

    Page(s): 609 - 614
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    The propagation of millimeter waves in metallic waveguides inhomogeneously filled with dielectric materials having surface plasma layers is characterized. The modal phase shift and attenuation of a 94-GHz wave are computed for a 10-µm plasma layer thickness as a function of carrier density. In the unexcited state, 90 percent of the millimeter-wave power is confined to the interior air region of the guide, while the remaining 10 percent propagates in the semiconductor insert. In the excited state at high injection levels, over 99 percent of the wave power propagates in the air region. Consequently, in this state, the waveguide will have a very low loss. A resonant cavity using the waveguide configuration shown to have a wide tuning range and high cavity Q. View full abstract»

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  • Getting the Picture (Jul. 1987 [T-MTT])

    Page(s): 680
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    First Page of the Article
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Aims & Scope

The IEEE Transactions on Microwave Theory and Techniques focuses on that part of engineering and theory associated with microwave/millimeter-wave components, devices, circuits, and systems involving the generation, modulation, demodulation, control, transmission, and detection of microwave signals. This includes scientific, technical, and industrial, activities. Microwave theory and techniques relates to electromagnetic waves usually in the frequency region between a few MHz and a THz; other spectral regions and wave types are included within the scope of the Society whenever basic microwave theory and techniques can yield useful results. Generally, this occurs in the theory of wave propagation in structures with dimensions comparable to a wavelength, and in the related techniques for analysis and design..

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