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Microwave Theory and Techniques, IEEE Transactions on

Issue 1 • Date Jan. 1979

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Displaying Results 1 - 21 of 21
  • [Front cover - Jan. 1979]

    Page(s): f1 - f2
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    Freely Available from IEEE
  • Comments on "The Measurement of Noise in Microwave Transmitters" [Letters]

    Page(s): 84 - 85
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    In the recent paper, "The Measurement of Noise in Microwave Transmitters," J. R. Ashley et al. give a review of several methods for the measurement of AM and FM noise, respectively. The section, which deals with FM noise measurements at frequencies below 5 GHz, may be the source of erroneous conclusions, as will be pointed out in this comment. View full abstract»

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  • Freely Available from IEEE
  • IEEE copyright form

    Page(s): 91
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    Freely Available from IEEE
  • [Back cover]

    Page(s): b1 - b2
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    Freely Available from IEEE
  • A Microwave System for the Controlled Production of Local Tumor Hyperthermia in Animals

    Page(s): 78 - 83
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    A microwave system was designed and constructed which provides controlled, localized hyperthermia in the tumors of four experimental animals. The components of the system are a 2.45-GHz microwave source, a four-way power-dividing network and reflected power monitor, a temperature-controlled microwave power regulator, and small direct-contact microwave applicators. Adjustment of the temprature control results in elevated temperatures in the centers of tumors which can be maintained to within ± 0.1°C without production of significant whole body hyperthermia.The temperatures at the edges of the locally heated tumors were found to vary within ±1.0°C of the center temperature. The system is currently being used to evaluate the therapeutic potential of sustained Iocalized hyperthermia in small tumors implanted subcutaneously in mice. View full abstract»

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  • Slot-Coupled Tee Junction in Rectangular-Guide E Plane

    Page(s): 65 - 69
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    An expression for the equivalent circuit of a waveguide tee junction coupled through a narrow transerse slot of variable length is determined from self-reaction and discontinuity in modal voltage. Impedance loading on primary guide and coupling are deternined from the equivalent network parameter. A comparison between theoretical and experimental results is presented. View full abstract»

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  • Design Theory for Broad-Band YIG-Tuned FET Oscillators

    Page(s): 8 - 14
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    Design techniques that have been succcessfully used on the development of X-band GaAs FET YIG-tuned oscillators are presented. The design procedure results in the maximization of the oscillator bandwidth. Small-signal device characterization is utilized and accurately predicts the oscillator bandwidths. Spurious oscillation conditions are discussed, and design techniques are prescribed for eliminating spurious oscillations in both the active circuit and resonator. The operation of an experimental oscillator verifies the design procedure. View full abstract»

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  • Microwave Amplifier Design with Potentially Unstable FET's

    Page(s): 1 - 3
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    The concept of maximally efficient gain, as applied to the design of microwave transistor amplifiers with potentially unstable devices, is illustrated by an example, utilizing the parameters of a typical small-signal microwave FET. View full abstract»

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  • Online Measurements of the Fast Changing Dielectric Constant in Oil Shale Due to High-Power Microwave Heating

    Page(s): 38 - 43
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    The change of the complex dielectric constant epsilon of off shale under intensive microwave heating is an abrupt phenomenon which is quite different from that due to conventional heating. Based on the principle of competitive chemical kinetics, a theory is proposed here for explaining this rapid change of the dielectric constant. A mathematical analysis of a coaxial waveguide loaded with oil-shale blocks which has a fast changing epsilon with respect to time is carried out in detail, from which an online measuring technique is derived for measuring this fast changing epsilon with respect to time and temperature. Preliminary experimental results show that the proposed theory is suitable for explaining this fast changing phenomenon. The online measuring technique reported here is very similar to the three-probe or five-port measuring methods reported in the literature, except that it is more general compared to some of these methods. Its designing approach is also different because it is derived from a modfied phasor analysis with the physical picture easily visualized. View full abstract»

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  • A New Microwave Variable Power Divider

    Page(s): 89 - 90
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    A new variable power divider (VPO) has been developed without any phase shifter and only two diodes are needed and in a balanced circuit four diodes. The two varactor diodes are equally biased. The differential phase shift between the output is zero independent of the power dividing ratio. Measurements on an experimental VPD at L-band frequencies are presented. View full abstract»

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  • The Measurement of the Radiation Losses in Dielectric Image Line Bends and the Calculation of a Minimum Acceptable Curvature Radius

    Page(s): 51 - 53
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    Measurements of the insertion loss due to radiation curved dielectric image lines of rectangular cross section are described for the frequency range from 26 to 90 GHz. A minimum acceptable curvature radius as a function of the frequency is calculated employing the field distributions of straight dielectric image lines and is compared with measurements. View full abstract»

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  • The Calculation and the Measurement of the Coupling Properties of Dielectric Image Lines of Rectangular Cross Section

    Page(s): 54 - 58
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    In this paper the coupling properties of uniformly coupled dielectric image lines of rectangular cross section are calculated employing an exact method for the determination of the phase constants of the even and the odd mode. The theoretical results are verified experimentally. The results are also applied to the calculation of the coupling characteristics of practical dielectric image line directional couplers. View full abstract»

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  • Broad-Band Internal Matching of Microwave Power GaAs MESFET's

    Page(s): 3 - 8
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    Broad-band internal matching techniques for high-power GaAS MESFET's at C band have been developed adopting novel circuit configurations and large-signal characterizations in the circuit design. The lumped-element two-section input matching network is formed on a single ceramic plate with a high dielectric constant. The semidistributed single-section output circuit is formed in microstrip pattern on an alumina plate. The internally matched GaAs FET with 11200-mu m total gate width developed has a 2.5-W power output at 1-dB gain compression and a 4.4-W saturated power output with 5.5-dB linear gain from 4.2 to 7.2 GHz without external matching. The FET internally matched from 4.5 to 6.5 GHz exhibited 5-W saturated power output with 6-dB linear gain. View full abstract»

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  • Water-Immersed Microwave Antennas and Their Application to Microwave Interrogation of Biological Targets

    Page(s): 70 - 78
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    This paper describes a method of significantly improving the resolution of systems used for interrogating the spatial variation of permittivity of biosystems at S band. The basic principle employed is to contract the wavelength of the interrogating radiation and to reduce the physical aperture of the interrogating probes by immersing the transmitting antenna, receiving antenna, and the target into a material with a high dielectric constant, namely water. The antenna design is described, and line scans employing transmitted and reflected energy are presented. View full abstract»

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  • A Fast Low-Loss Microstrip p-i-n Phase Shifter

    Page(s): 14 - 16
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    A 4-bit p-i-n phase shifter with low RF attentuation, fast switching time, and low switching power requirements is described. The circuit, made in microstripline, consists of four cells giving phase shifts of 180, 90, 45, and 22.5deg, respectively. Each cell consists of a 3-dB coupler loaded by two p-i-n diodes. The transmission loss is 1.6 dB ± 0.2 dB over the operating bandwidth of 11.7-12.2 GHz for a biasing current of only 5 mA/cell. Switching time between phase states is 1 ns. View full abstract»

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  • On an Ultrabroad -Band Hybrid Tee

    Page(s): 58 - 64
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    A hybrid tee is investigated which consists of two broad-band line transformers and a lumped branching point. The branching point forms a bridge circuit, the resistances of which are determined by six lines and their load resistors. The bandwidth is wider than three decades, extending from 2.4 MHz to 5 GHz, and is determined by the transformers. In a special version, the upper cutoff frequency can be shifted to about 12 GHz. The isolation between opposite lines is greater than 40 dB. View full abstract»

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  • Microstrip Tapped-Line Filter Design

    Page(s): 44 - 50
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    The subject of this article is a step-by-step design procedure for microstrip tapped-line filters, accompanied by appropriate design curves. In addition to microstrip tapped-line interdigital filters, a new hairpin-line filter using tapping is introduced. The equation to equation the singly loaded Q for hairpin resonators produced by tapping is derived. Experimental data is presented for filters over 20-percent bandwidth. View full abstract»

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  • Experimental Attenuation of Rectangular Waveguides at Millimeter Wavelengths

    Page(s): 31 - 37
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    The experimental values of attenuation of commercially available rectangular waveguides were determined at frequencies between 25 and 200 GHz with emphasis on high accuracy. They were compared with the theoretical values computed from the dc conductivities, taking into consideration temperature effects, work hardening, size effects, surface roughness, and a room-temperature anomaly of the skin effect. A new way to express the excess attenuation due to these effects was fomulated. Excess ratios of attenuation of coin-silver waveguides were found to be well below the values used in engineering in the past. They can satisfactorily be explained by surface roughness. The normalized excess attenuations of copper guides are higher than those of guides made of silver but lower than cited in the literature. View full abstract»

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  • Circuit Behavior and Impedance Characteristics of Broad-Band TRAPATT-Mode Amplifiers

    Page(s): 23 - 31
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    The characteristics of TRAPATT-mode high-efficiency oscillators and broadband amplifiers are reviewed. It is concluded that a broad-band amplifier like a high-efficiency oscillator should have capacitive circuit impedances and is distinguished from a high-efficiency oscillator principally by the number of important harmonics employed. A smaller number of harnonics for the amplifier can lead to broader bandwidth but lower efficiency. The relative merits of experimental amplifier circuits are discussed. It is shown that coaxial-line circuits employing diode packages with large lead inductances are characterized by harmonic impedances which can have large values over broad frequency bands. However, it is also shown that the device waveforms in this case are excessively degraded and relativeIy low-efficiency results. On the other hand, microstrip circuits with a Iow-impedance diode mount can provide broadband low impedances at both fundamental and third harmonic and have exhibited better performance. View full abstract»

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  • Analysis and Design of an X-Band Actively Compensated IMPATT Diode Amplifier

    Page(s): 17 - 23
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    This paper shows how broad-banding of an IMPATT diode amplifier can be achieved using a circuit technique known as active reactance compensation. Theoretical analysis and experimental results both show that the gain-bandwidth products of an uncompensated IMPATT amplifier improves from G12/B = k to G14/B = 2k (where k is a constant) for the same amplifier actively compensated. The measured 3-dB bandwidth of 230 MHz for a 9.0-GHZ amplifier having a gain of 10 dB is improved to 700 MHz at the same gain. View full abstract»

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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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