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Microwave Theory and Techniques, IEEE Transactions on

Issue 5 • Date May 1991

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Displaying Results 1 - 19 of 19
  • Comments on "X-band 0.5, 1, and 2 Watt power amplifiers with marked improvement in power-added efficiency

    Publication Year: 1991
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (37 KB)  

    For the original article see ibid., vol.38, no.6, p.707-11 (1990). Power-added efficiency results from MMIC amplifiers which were designed, fabricated, and tested based on efforts reported in the above-named work have caused a reassessment of measurements made for that work. The new MMIC amplifiers exhibited a maximum power-added efficiency of 32% in X-band at 1-W output power. These results are significantly lower than the 53% average power-added efficiency for the 1-W hybrid amplifiers previously reported. In a recent experiment on one of the original hybrid amplifiers, the previous efficiency results could not be replicated or confirmed. It is prudent to assume that the earlier amplifier efficiency measurements were in error.<> View full abstract»

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  • Millimeter-wave technology advances since 1985 and future trends

    Publication Year: 1991 , Page(s): 759 - 767
    Cited by:  Papers (15)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (924 KB)  

    The author focuses on finline or E-plane technology. Several examples, including AVES, a 61.5-GHz radar sensor for traffic data acquisition, are included. Monolithic integrated 60- and 94-GHz receiver circuits composed of a mixer and IF amplifier in compatible FET technology on GaAs are presented to show the state of the art in this area. A promising approach to the use of silicon technology for monolithic millimeter-wave integrated circuits, called SIMMWIC, is described as well. As millimeter-wave technology has matured, increased interest has been generated for very specific applications: (1) commercial automotive applications such as intelligent cruise control and enhanced vision have attracted great interest, calling for a low-cost design approach; and (2) an almost classical application of millimeter-wave techniques is the field of radar seekers, e.g. for intelligent ammunitions, calling for high performance under extreme environmental conditions. Two examples fulfilling these requirements are described View full abstract»

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  • 94 GHz three-dimensional imaging radar sensor for autonomous vehicles

    Publication Year: 1991 , Page(s): 819 - 827
    Cited by:  Papers (13)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    The authors report on using millimeter-wave images for real-time vehicle guidance. For application in the field of autonomous locomotion, the main advantage of this sensor concept is direct access to range and velocity information. System design and imaging results of a multitask 94-GHz pulse Doppler radar with 25-cm radial and 1.5° angular resolution are discussed. To point out specific millimeter-wave scattering phenomena, various radar images of typically structured indoor situations are presented. Extraction of information from sensor data, for example, obstacle detection, is demonstrated by radar image processing View full abstract»

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  • Detection of target distance in the presence of an interfering reflection using a frequency-stepped double side-band suppressed carrier microwave radar system

    Publication Year: 1991 , Page(s): 809 - 818
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    A technique for detecting the distance to a highly reflective target in the presence of an interfering reflection using a frequency-stepped double-sideband suppressed carrier (DSBSC) microwave-millimeter-wave radar system is analytically derived. The main result of the analysis shows that the measured group delays produced by the DSBSC system possess a periodicity inversely proportional to the difference between the time delays to the target and interferer, independent of the signal-to-interference ratio (SIR). Simulation results are presented in the context of electron plasma density range estimation using a block diagram communications CAD tool. A unique and accurate plasma model is introduced. A high-resolution spectral estimation technique, based on an autoregressive time series analysis is applied to the measured group delays, and it is shown that accurate target distance estimates may be obtained, independent of SIR View full abstract»

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  • Millimeter-wave components and subsystems built using microstrip technology

    Publication Year: 1991 , Page(s): 768 - 774
    Cited by:  Papers (5)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    The author describes the evaluation of microstrip as a transmission medium for components and subsystems operating in the millimeter wavebands. The manufacturing process for thin-film MICs on single-crystal quartz is described. The microwave integrated circuit (MIC) manufacturing process is suitable for high-value manufacturing of highly integrated subsystems since manufacturing costs for the circuits are almost independent of the number of circuit functions. Designs for various circuit elements are discussed, and an integrated subsystem is described in which MIC techniques are used to produce a miniature millimeter-wave distance-measuring sensor. Range measurement results for the miniature sensor are presented View full abstract»

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  • Microwave systems design for high-performance moving target indicators in radars

    Publication Year: 1991 , Page(s): 791 - 797
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Clutter cancellation of 65 dB and better is directly proportional to good radar stability, and since many hardware areas produce instabilities at various levels, the architecture of a radar requires special design considerations to support this high stability. The noise character and generation methods of these instabilities in the various hardware areas are described, and design solutions are given to eliminate them. Microwave delay line, a reliable, accurate method of measuring radar stability in L- and S-band radars, is described. The longest microwave delay line available for use at L -band and S-band frequencies is a 15-μs sapphire bulk acoustic wave (BAW) delay line. For higher-frequency radars, smaller delays must be used to keep the insertion loss down to a usable level. The question is raised as to the adequacy of this delay time to provide sufficient visibility for stability measurements of the stable noise. For transmitter measurements, it is adequate for the more common pulse widths, which are less than 15 μs. For LO measurements, the analysis shows that this delay does provide sufficient decorrelation for accurate LO noise measurements View full abstract»

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  • Capacitance-voltage characteristics of microwave Schottky diodes

    Publication Year: 1991 , Page(s): 857 - 863
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Based on an analytical solution of Poisson's equation, the authors calculate/capacitances of metal circular dots and metal stripes on the surface of a doped semiconductor material. When the dimensions of the dot or stripe are much larger than the depletion region, the results are reduced to the conventional formula for a parallel-plate capacitor. In the opposite limit, the overall capacitance is determined by the edge effect. This edge capacitance is proportional to the device periphery, with the coefficient of proportionality dependent on the shape of the metal. The parallel-plate component of the device capacitance is modulated by the applied voltage; the edge component is nearly independent of the applied voltage. Hence, the largest capacitance modulation is achieved in devices with the smallest ratio of the device periphery over the device area, which has the smallest edge effect. The measured capacitances of small round GaAs Schottky barrier diodes are in reasonable agreement with calculated results View full abstract»

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  • Theoretical and experimental characterization of coplanar waveguide discontinuities for filter applications

    Publication Year: 1991 , Page(s): 873 - 882
    Cited by:  Papers (67)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    A full-wave analysis of shielded coplanar waveguide (CPW) two-port discontinuities based on the solution of an appropriate surface integral equation in the space domain is presented. Frequency-dependent scattering parameters for open-end and short-end CPW stubs are computed using this method. The numerically derived results are compared with measurements performed in the frequency range 5-25 GHz and show very good agreement. From the scattering parameters, lumped-element equivalent circuits have been derived to model the discontinuities. The inductors and capacitors of these models have been represented by closed-form equations, as functions of the stub length, to compute the circuit element values for these discontinuities View full abstract»

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  • Advances in millimeter-wave subsystems in Japan

    Publication Year: 1991 , Page(s): 775 - 781
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    The authors describe the development trends and results of millimeter-wave systems in Japan in such fields as communication, radar, and measurement systems. The applications included are the W-40G waveguide transmission communication system, an automobile traffic control system using the 60-GHz band, a collision avoidance radar system for an automobile, a plasma electron density measuring system, and satellite communication. The authors describe the development of devices such as high-power FET amplifiers, traveling wave tube amplifiers (TWTAs), IMPATT amplifiers, low-noise amplifiers, and monolithic microwave integrated circuit (MMIC) devices used in constructing the millimeter-wave systems View full abstract»

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  • An overview of frequency synthesizers for radars

    Publication Year: 1991 , Page(s): 782 - 790
    Cited by:  Papers (6)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    The authors present an overview of frequency synthesizer techniques suitable for radar systems. Various synthesizer architectures and key synthesizer components are considered along with a discussion of advantages and disadvantages. Some architectures are hardware intensive and, because of their physical size, are more suitable for stationary or shipboard radars. Architectures requiring smaller volume are more suitable for airborne applications. Direct, phase-locked, and frequency-locked architectures are covered, including key building blocks and performance limitations. The direct digital synthesizer (DDS) architecture is considered briefly, as it is not yet widely used in radar systems. Finally, projections are made of advances in components that have a direct effect on frequency synthesis View full abstract»

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  • Microwave aquametry-needs and perspectives

    Publication Year: 1991 , Page(s): 828 - 835
    Cited by:  Papers (7)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The author reviews the technical and economic importance of microwave techniques for moisture content determination in industrial processes, pointing out certain areas that require more consideration, and lists the most urgent problems to be solved. Determination of moisture content or water content in materials with microwave radiation has several advantages over other electrical methods applying lower frequencies. Problems concerning the development of microwave equipment for those purposes are also reviewed. Trends in further development of the instrumentation and research concepts are considered View full abstract»

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  • Mathematical methods for treatment planning in deep regional hyperthermia

    Publication Year: 1991 , Page(s): 864 - 872
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    Techniques are described which accelerate the rerunning of programs for each new set of input parameters in the computer simulation for treatment planning in deep regional hyperthermia cancer therapy using the Sigma 60 applicator. This is done by separating the problem into responses by individual quadrants and by using an impulse response to get multiple frequencies per run. The implementation of these techniques using the finite-difference time-domain (FDTD) method is described. The accuracy is tested against three-dimensional measurements made in a homogeneous phantom, and the results are presented. The result is a method capable of planning an optimum treatment for deep regional hyperthermia View full abstract»

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  • Measurement of the microwave absorption for small samples in a coaxial line

    Publication Year: 1991 , Page(s): 890 - 892
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    Microwave absorption measurements in terms of power loss per unit volume of very small liquid and solid samples (0.003-2.6 μL) contained in capillaries inserted across the dielectric of a coaxial line have been made between 2 and 26.5 GHz. This perturbation technique makes it possible to measure small differences in the absorption of the samples in a swept fashion. The measured value of the microwave absorption of heavy and light water is within 10% of the value calculated from published values of the dielectric constant at all frequencies up to the highest frequency measured and within 5% at frequencies (<20 GHz) where the effects of the impedence mismatch caused by the sample are minimal. The measured differences in the Debye relaxation times of light and heavy water agrees with published values to even better accuracies owing to the similarities in the dielectric constants and thus similarities in the mismatch in the coax caused by the sample View full abstract»

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  • A frequency-dependent basis function applied to microstrip

    Publication Year: 1991 , Page(s): 893 - 896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    Spheroidal wave functions (SWF) and the spectral-domain method (SDM) are used to compute the effective dielectric constant for microstrip. The authors explore the ability of the SWF to change shape as a function of a parameter, e.g. frequency, while maintaining orthogonality, completeness, edge condition, and aperture limit. The authors introduce the SDM equations, provide a brief overview of the SWF, and study the effective dielectric constant as a function of frequency for several commonly used basis functions. A single-term expansion for the vector current density provides excellent results over a broad spectrum (1-100 GHz). Numerical results compare favorably with other commonly used techniques View full abstract»

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  • An experimental adaptive nulling receiver utilizing the sample matrix inversion algorithm with channel equalization

    Publication Year: 1991 , Page(s): 798 - 808
    Cited by:  Papers (4)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    The authors explore two ideas for effectively achieving channel equalization within the framework of a narrowband sidelobe canceler. The first approach relies primarily on digital equalization to enhance conventional sample matrix inversion (SMI) performance, whereas the second utilizes feedback to extend the SMI method into the realm of analog adaptive cancellation. An experimental four-channel receiver that supports open-loop and closed-loop operation is described. As implemented, three different canceler modes are possible: feedforward, feedback, and a tandem feedback/feedforward combination. All three modes have been successfully demonstrated in bench experiments with a broadband noise source using the SMI algorithm. Cancellation ratios in excess of 50 dB have been achieved in a four-channel testbed system View full abstract»

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  • Phase noise characterization of SAW oscillators based on a Newton minimization procedure

    Publication Year: 1991 , Page(s): 883 - 889
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    An iterative minimization technique is used to optimize the values of circuit and device parameters which determine the phase noise response of a voltage-controlled SAW-stabilized oscillator (VCSO). An expression-developed by T.E. Parker (1985) is used to calculate the double-sideband phase noise to carrier ratio from circuit parameter values; good agreement between calculations and phase noise measurements is achieved by minimizing the squared error through the use of a steepest-descent/Newton-Raphson minimization scheme. Less accurately known circuit parameters are thus optimized in an iterative fashion. Exact expressions for the elements of the Hessian Matrix are used in the Newton-Raphson procedure, allowing for fast computations. The numerical findings suggest that useful results can be obtained in the determination of VCSO circuit parameters View full abstract»

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  • Optimization of SAR distributions in liver and lung regions irradiated by the H-horn annular phased array hyperthermia system

    Publication Year: 1991 , Page(s): 852 - 856
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The author discusses a type of annular phased array (APA) system-the H-horn APA. The phase and amplitude control of power deposition patterns for this system have been theoretically analyzed at a frequency of 200 MHz. The formulas for calculating the electric field (E-field) and specific absorption rate (SAR) for this APA system have been derived and can be applied to other types of APA systems. Models on computerized tomography (CT) scans from liver and lung regions have been used for predicting optimization of the E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the phase and amplitude control of SAR patterns results in a more selective and effective heating of tumors situated eccentrically and deeply within the body. The numerical results indicate that it is possible to shift the absorbed power patterns by electrically varying the phase and/or the amplitude of the sources and manually moving the positions of the horns View full abstract»

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  • A multiview microwave imaging system for two-dimensional penetrable objects

    Publication Year: 1991 , Page(s): 845 - 851
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    A microwave imaging system is based on a multiview numerical solution to the integral equation of 2D transverse magnetic (TM) scattering is proposed. This solution is achieved by the moment method, and a pseudoinversion transformation is used to face ill-conditioning problems. All experimental setup is described that uses a scanning subsystem for measuring the values of the scattered electric field inside an observation domain located outside the investigation one (i.e., the area containing the cross sections of cylindrical dielectric scatters). Rotations of the investigation domain with respect to the scanning subsystem and the transmitting antenna allow a multiview imaging process. The imaging system does not require plane-wave illumination and does not use any first-order approximations; hence, it may be used even in the case of strong scatterers. The offline and once-and-for-all computation of the pseudoinverse matrix allows an inexpensive reconstruction in terms of computer resources. Some tests of the system were carried out, and the results are reported View full abstract»

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  • Cylindrical geometry: a further step in active microwave tomography

    Publication Year: 1991 , Page(s): 836 - 844
    Cited by:  Papers (40)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB)  

    A prototype imaging system for active microwave tomography using cylindrical geometry has been developed, making it possible to obtain images of the dielectric properties of biological targets at 2.45 GHz. This configuration allows a fast exploration of body slices placed along the array axis, in a way similar to that of present X-ray scanners. The electromagnetic compatibility (EMC) of this approach is critical because the strongly attenuated received fields are measured on the same array which is being used to emit a high-level illuminating signal. Therefore, carefully designed high-frequency architectures and detection techniques are necessary. The system requires no mechanical movements to illuminate the body from multiple directions (views) and measure the scattered fields. In this way, a complete data set consisting of 64 views is acquired in 3 s using low-power illumination. The system is described, and images obtained with biological phantoms and actual bodies are presented View full abstract»

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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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