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Microwave Theory and Techniques, IEEE Transactions on

Issue 6 • Date June 2001

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Displaying Results 1 - 22 of 22
  • Comments on "On the computation of the complete spectral Green's dyadic for layered bianisotropic structures" [with reply]

    Page(s): 1140 - 1142
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (103 KB)  

    For original paper see F.L.Mesa, R.Marques and M.Horno, ibid., vol.46, no.8, pp.1158-64 (Aug. 1998). In the above paper the authors have shown how to compute their complete spectral Green's dyadic (CSGD) for multilayered bianisotropic planar structures. This paper comments on their results, and includes their reply to the comments. View full abstract»

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  • Analysis of metallic waveguides of a large class of cross sections using polynomial approximation and superquadric functions

    Page(s): 1136 - 1139
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB) |  | HTML iconHTML  

    By using the polynomial approximation and superquadric functions in the Rayleigh-Ritz procedure, a unified method has been proposed to analyze conducting hollow waveguides of a large class of cross sections in our previous paper. Some useful and complicated cross-sectional waveguides in the microwave system, namely, eccentric annular, pentagonal, L-shaped, single-ridged, and double-ridged waveguides are analyzed in this paper. Compared with other numerical methods, this method has the advantages of being straightforward, accurate, and computational effective View full abstract»

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  • Ultra-broad-band doubly balanced star mixers using planar Mouw's hybrid junction

    Page(s): 1077 - 1085
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    The planar Mouw's hybrid junction is realized by coplanar waveguide (CPW) to coplanar strip (CPS) or CPW to CPW T-junctions. A new explanation of Mouw's theory based on coupled transmission lines and including the transmission line losses is presented, The modified theory is more suitable for ultra-broad-band mixer design. Some prototype mixers with CPW to CPS or CPW to CPW T-junctions are fabricated with Al 2O3 substrate, The prototype mixers show a bandwidth of greater than 20:1 if the even-mode resonance has been damped out. A method for damping out the even-mode resonance is also presented. All of the prototype circuits show much broader bandwidth than that of conventional star mixer View full abstract»

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  • General oscillator characterization using linear open-loop S-parameters

    Page(s): 1094 - 1100
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    From a practical standpoint, oscillator design using linear open-loop S-parameters is attractive to designers due to the ease of use and widespread availability of linear S-parameter-based analysis software. However, the easiest and, therefore, most common approach is based on intuition and rules of thumb. The intent of this paper is to obtain quantitative expressions that characterize oscillator performance in terms of the linear open-loop S-parameters. A characteristic equation is derived that determines oscillator stability. The Nyquist stability criteria can be applied to this equation directly from the open-loop Bode plot. A closed-loop gain parameter is derived, which describes how the open-loop circuit self-connects. From this parameter, the startup time, oscillation frequency, and loaded Q can be predicted. A prediction of actual oscillation frequency can be made based on a simple oscillator model with known saturation characteristics. It will be shown under what conditions these expressions simplify to more readily applicable forms. In many cases, the designer can adjust analysis parameters to allow the use of the simplified expressions View full abstract»

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  • Reduction of substrate-mode effects in power-combining arrays

    Page(s): 1067 - 1072
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    We report a simple theory for the reduction of substrate modes in quasi-optical power-combining arrays. This qualitative theory predicts that detrimental substrate-mode effects can be greatly reduced through a judicious choice of the array unit cell size. Experimental evidence from quasi-optical tripler grids is presented to confirm the theory. Measured results show a dramatic improvement in the radiation pattern and effective radiated power of arrays with both grounded and ungrounded substrates View full abstract»

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  • Analytic sampling-circuit model

    Page(s): 1013 - 1019
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    We develop analytic expressions for the impulse response and kickout pulses of a simple sampling circuit that incorporate the nonlinear junction capacitance of the sampling diode. We examine the effects of both the time-varying junction capacitance and conductance on the impulse response and kickout pulses, and discuss their impact on the accuracy of the nose-to-nose calibration technique View full abstract»

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  • Frequency-tunable microwave dielectric resonator

    Page(s): 1020 - 1026
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    A new type of tunable composite dielectric resonator (DR) has been designed, In the structure of this DR, a controllable insert was used to change the resonance frequency (f0) in a wide spectral range, while preserving a high quality factor. The simplest of proposed resonance systems for obtaining f0 control is a microwave DR crossed by an air slot, which is controlled by fast piezoelectric actuator. Analytical and experimental techniques were employed for optimization of the composite DR structure. It has been observed that this device can create a change up to 20%-25% in its resonance frequency View full abstract»

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  • Effect of internal reflections on the radiation properties and input impedance of integrated lens antennas-comparison between theory and measurements

    Page(s): 1118 - 1125
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    This paper presents the effect of internal reflections on the beam pattern and input impedance of integrated lens antennas. A silicon lens was designed and manufactured, and measurements were conducted at a frequency of 100 (impedance) and 500 GHz (beam pattern). A frequency-dependence characterization of the beam pattern clearly showed the existence and impact of internal reflections. The measurements confirmed that most of the frequency variations of the beam pattern could be attributed to internal reflections, as predicted by the model. An on-wafer measurement strategy for determining the antenna impedance at millimeter-wave frequencies is presented. The validity of the model was also proven by an excellent match of the input impedance measurements and predictions. Not only the level, but also the oscillation on the impedance curve was predicted accurately. Initial space qualification was performed in the form of thermal cycling View full abstract»

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  • An effective method for designing nonuniformly coupled transmission-line filters

    Page(s): 1027 - 1031
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB) |  | HTML iconHTML  

    An effective method is presented in this paper to design nonuniformly coupled transmission-line filters. This kind of filter can be used to realize almost an arbitrary filter characteristics as nonuniform transmission-line filters do. They can be cascaded directly, and no directional coupler is needed. This method begins with calculating characteristic impedance of a nonuniform transmission line by those techniques already established for designing nonuniform transmission-line filters, then determining the even- and odd-mode impedances of a nonuniformly coupled transmission line by a simple transformation. A first-order solution to the related nonlinear equations is especially proposed to calculate effective dielectric constants and line dimensions from the obtained characteristic impedances simultaneously. A device was built and tested, and the measured results verify that the proposed method is of practical use View full abstract»

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  • Design of asymmetric filters with requirements in two bands of finite extension

    Page(s): 1045 - 1049
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB) |  | HTML iconHTML  

    In this paper, a general design procedure is presented for a class of filters characterized by requirements in two frequency bands, both of finite extension (one passband and one stopband). The filter structure is formed of suitable series resonators coupled through impedance inverters. The resonators also exhibit, in addition to the series resonance in the passband, a parallel resonance in the stopband. The procedure derives a suitable pole-zero distribution for the overall transfer function and determines the parameters of the equivalent resonators in order to obtain a quasi-equiripple response, both in the passband and stopband of the filter. The procedure has been implemented to design filters in rectangular waveguide; a pair of identical filters to be used in a diplexer have been designed through the procedure and fabricated in order to validate the theory View full abstract»

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  • A Ka-band indium-antimonide junction circulator

    Page(s): 1101 - 1106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB) |  | HTML iconHTML  

    Following a brief overview of the underlying theory, experimental results are presented for the first time showing circulator action in a semiconductor junction structure. An axially magnetized indium-antimonide disc fixed in a three-port finline structure and cooled to the temperature of boiling nitrogen, 77 K gives circulation across Kα-band. For a dc magnetic bias of 0.73 T, a 15-dB isolation is recorded from 28 to 40 GHz, or a fractional bandwidth of at least 35%. Typical insertion loss is less than 1.5 dB from the WG22 reference plane at the test fixture ports. Continued operation above 40 GHz is predicted, but has not yet been measured. Measurement suggests that circulation is evident even where the effective propagation constant is imaginary, although better theoretical agreement is achieved when this is a real quantity. This new device makes millimeter-wave broad-band circulation a possibility and confirms the current model based upon the Drude-Zener approximation. A theoretical example is then given for a design operating to 140 GHz, yielding a fractional bandwidth of 110% View full abstract»

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  • Numerical simulation using ADI-FDTD method to estimate shielding effectiveness of thin conductive enclosures

    Page(s): 1060 - 1066
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    Numerical simulations were run using the alternating-direction implicit-finite-difference time-domain (ADI-FDTD) method to calculate the shielding effectiveness of various enclosures. The enclosures were composed of very thin conductive sheets, which are generally fabricated using conductive paints or electroless plating techniques on plastic surfaces. In this case, very fine cells must be used for finite-difference time-domain (FDTD) modeling. In the conventional FDTD method, fine cells reduce the time-step size because of the Courant-Friedrich-Levy (CFL) stability condition, which results in an increase in computational effort, such as the central processing unit (CPU) time. In the ADT-FDTD method, on the other hand, a larger time-step size than allowed by the CFL stability condition limitation can be set because the algorithm of this method is unconditionally stable. Consequently, an increase in computational efforts caused by fine cells can be prevented. The results from the ADI-FDTD method were compared with results from the conventional FDTD method, analytical solutions, and experimental data. These results clearly agree quite well, and the required CPU time for the ADI-FDTD method can be much shorter than that for the FDTD method View full abstract»

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  • New simple proofs of the two-port stability criterium in terms of the single stability parameter μ12)

    Page(s): 1073 - 1076
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB) |  | HTML iconHTML  

    The classical scattering-parameter stability criterium for a linear two-port makes use of two conditions involving the Rollet parameter K plus one additional parameter. A new stability criterium was developed by Edwards and Sinksky [1992] on the basis of a condition on a single parameter, i.e., μ1 or μ2. This paper presents a new, simpler, and more straightforward set of proofs of the single-parameter stability criterium for a linear two-port. The first proof is algebraic and shows the equivalence of the conditions K>1, b 1>1 with the condition μi>1 (i=1, 2). The second proof, which is geometrical, relies only on the classical stability circle concepts in an improved way with respect to the treatment by Edwards and Sinksky View full abstract»

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  • A full-wave modal analysis of inhomogeneous waveguide discontinuities with both planar and circular cylindrical boundaries

    Page(s): 1132 - 1136
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB) |  | HTML iconHTML  

    A full-wave analysis of an inhomogeneous waveguide region with both planar and circular cylindrical boundaries is presented in this paper. Circular cylindrical modal functions are used to represent the fields. Field matching on the planar walls and apertures is rigorously achieved by the finite plane-wave series expansion of each modal field, whereas the addition theorem for cylindrical waves is used for rigorous field matching on the circular cylindrical boundaries. Numerical results are given for rectangular waveguides with 90° bends and rounded outer corners View full abstract»

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  • Performance of Ku-band on-chip matched Si monolithic amplifiers using 0.18-μm-gatelength MOSFETs

    Page(s): 1086 - 1093
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB) |  | HTML iconHTML  

    We demonstrated Ku-band (12-20 GHz) Si MOSFET monolithic amplifiers with on-chip matching networks. In these amplifiers, we used 3-μm-thick Al-metal transmission lines on 8-μm-thick polyimide-SiON-SiO2 isolation layers for the matching networks. The amplifier showed a gain of 6-10 dB and a noise figure (NF) of 3.5-4 dB up to about 20 GHz, the highest gain and lowest NF yet reported for MOSFET amplifiers at this frequency. We also clarified the lossy on-chip inductor effect on the gain and noise performance of the amplifiers View full abstract»

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  • Control of attenuation pole frequency of a dual-mode microstrip ring resonator bandpass filter

    Page(s): 1113 - 1117
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB) |  | HTML iconHTML  

    A novel method is proposed to control the attenuation pole frequency of a dual-mode circular microstrip ring resonator bandpass filter, keeping the bandwidth constant. In this paper, the coupling between the dual modes is provided as the total effect of stub perturbation at the end of symmetry plane, and the angle between input/output ports. By making a various combinations of these two parameters, it is possible to control the attenuation pole frequency. An additional small coupling induced by excitation capacitance is also considered. Filters are simulated using the calculated coupling constant, and then the attenuation pole frequencies and bandwidth of the simulated filters are verified by experiment. Theoretical expressions are further devised to calculate the attenuation pole frequencies View full abstract»

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  • An inverse technique to evaluate permittivity of material in a cavity

    Page(s): 1129 - 1132
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (96 KB) |  | HTML iconHTML  

    A numerical technique to estimate the dielectric constant and loss factor of a homogeneous dielectric material placed in an arbitrary shaped cavity has been developed. The values of S-parameters are measured experimentally by placing the sample in the cavity. Starting with a trial set of permittivity values, the computation is carried out using the finite-element method (FEM) to match the S-parameters around the fundamental resonance frequency. The FEM routine is run several times while optimizing the values of dielectric constant and conductivity of the sample. During the process of optimization, eight different measures of error between computed and experimental values of complex S-parameters are examined. It is found that there is no single measure of error, which can be minimized to estimate two parameters (dielectric constant and the loss factor), but the combination of errors has to be minimized to get the exact solution. The computer program can generate the solution with an accuracy of less than 0.01% in a few hours on a Pentium-based personal computer View full abstract»

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  • On the application of the microgenetic algorithm to the design of broad-band microwave absorbers comprising frequency-selective surfaces embedded in multilayered dielectric media

    Page(s): 1050 - 1059
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB) |  | HTML iconHTML  

    In this paper, we present a procedure for synthesizing broad-band microwave absorbers incorporating frequency-selective surface (FSS) screens embedded in dielectric media using a binary coded genetic algorithm (GA). The GA simultaneously and optimally chooses the material in each layer, thickness of each layer, FSS screen periodicity in the z- and y-directions, its placement within the dielectric composite, and the FSS screen material. Additionally, the GA generates the cell structure of the FSS screen. The result is a multilayer composite that provides maximum absorption of both TE and TM waves for a prescribed range of frequencies and incident angles. This technique automatically places an upper bound on the total thickness of the composite View full abstract»

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  • Optimum design of very high-efficiency microwave power amplifiers based on time-domain harmonic load-pull measurements

    Page(s): 1107 - 1112
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    Due to the large expansion of wireless communications, the need for high-efficiency power amplifiers has emerged. In mobile communication systems, power amplifiers are the most critical elements for the power-dissipation budget. Thus, the operating conditions of active devices have to be optimized using accurate and complementary computer-aided design (CAD) and experimental tools. This paper reports two design methods of high-efficiency power amplifiers. The first one is CAD oriented and based on the substitute generator technique using the nonlinear model of transistors. The second one is based on a specific measurement system of time-domain waveforms using a modified vector network analyzer, coupled with harmonic active load-pull techniques (three active loops). This new setup enables the measurement and optimization of time-domain waveforms at both ports of transistors driven by constant-wave test signals. These two design methodologies are applied to the optimization of an S-band 1-W class-F GaInP/GaAs heterojunction-bipolar-transistor power amplifier View full abstract»

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  • New uniplanar subnanosecond monocycle pulse generator and transformer for time-domain microwave applications

    Page(s): 1126 - 1129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    This paper presents the development of a new monocycle pulse generator and pulse-to-monocycle-pulse transformer operating in the subnanosecond regime. These circuits employ Schottky diodes, step recovery diodes, and simple charging and discharging circuitry, and are completely fabricated using coplanar waveguides. Simple transient analysis and design of the circuits are presented along with their operating principles. The pulse-to-monocycle-pulse transformer converts a 1 V 300 ps pulse into a 0.7-V 350 ps monocycle pulse. The monocycle pulse generator produces a monocycle pulse having 333 ps pulsewidth and more than 2 V from an input square wave of 10 MHz repetition rate. The generated monocycle pulses have very symmetrical positive and negative portions and low ringing level View full abstract»

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  • Accurate modeling of dual dipole and slot elements used with photomixers for coherent terahertz output power

    Page(s): 1032 - 1038
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB) |  | HTML iconHTML  

    Accurate circuit models derived from electromagnetic simulations have been used to fabricate photomixer sources with optimized high-impedance antennas. Output powers on the order of 1 μW were measured for various designs spanning 0.6-2.7 THz. The improvement in output power ranged from 3 to 10 dB over more conventionally designed photomixers using broad-band log-spiral antennas. Measured data on single dipoles, twin dipoles, and twin slots are in good agreement with the characteristics predicted by the design simulations View full abstract»

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  • Shield-based microwave on-wafer device measurements

    Page(s): 1039 - 1044
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    This paper introduces a shielding technique for use with microwave on-wafer device characterization. This results in a shield-based test fixture, which offers many advantages compared to conventional structures. Among others, the test fixture offers full scalability and very low cost, high measuring accuracy, mitigation of leakage problems associated with lossy substrates, and a large measuring realism. The performance of the shield-based method is demonstrated with measurements on test structures fabricated in low-cost silicon processes 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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