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Microwave Theory and Techniques, IEEE Transactions on

Issue 1  Part 1 • Date Jan. 2002

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Displaying Results 1 - 25 of 41
  • Guest editors' overview

    Page(s): 1 - 3
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    Freely Available from IEEE
  • Comments on "General oscillator characterization using linear open-loop S-parameters" [with reply]

    Page(s): 226 - 228
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    For original paper see ibid., vol. 49, no. 6, p. 1094-1100 (2001). A general expression for the gain in terms of S-parameters, based on the physical concept of the input and output impedances of the self-terminated circuit, has been provided. This expression is mathematically equivalent to the one provided in terms of T-parameters in the aforementioned paper by Randall and Hock, and in the opinion of the commenter invalidates the S-parameter formulation provided by them in the paper. In reply, the authors state that Cascio's comments and S-parameter derivation touch on an important fundamental concept underlying the derivation described in their paper. They claim that their paper did not go into depth explaining some of the subtleties related to this, but they welcome the opportunity to do so now in this reply. View full abstract»

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  • Authors' reply

    Page(s): 227 - 228
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    First Page of the Article
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  • Dyadic Green's function modifications for obtaining attenuation in microstrip transmission layered structures with complex media

    Page(s): 112 - 122
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    Rigorous derivation of the correction to the Green's function for a microstrip structure containing complex layered media is done for imperfect metallization. A hierarchy of formulas is found consistent with a full-wave electromagnetic code employing zero-thickness extent conductors for the guiding structure metal. At the top of the hierarchy are formulas that utilize new Green's functions of the structure, whereas at the bottom are formulas that are only dependent on the conductor geometry and material properties. Numerical examples are provided to show the sensitivity of the propagation constant attenuation to those elegantly simple formulas at the bottom of the hierarchy View full abstract»

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  • Analysis of the coaxial helical-groove slow-wave structure

    Page(s): 191 - 200
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    A coaxial helical-groove structure is presented and analyzed in this paper. The dispersion equation and coupling impedance of the structure are given. Numerical calculations of the dispersion relation and coupling impedance with different structure dimensions are carried out. Calculated results indicate that the cold bandwidth of this structure can reach 60%, while the coupling impedance is more than 16 Ω. It is shown that the coaxial helical groove is a wide-band slow-wave structure with high-power capacity View full abstract»

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  • A generalized solution for diversity combining techniques in fading channels

    Page(s): 46 - 50
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    This paper develops an exact and general formulation in order to investigate the performance of equal gain, selection/equal gain, and selection/maximal ratio combining techniques. The performance is examined in terms of both the reliability and mean signal-to-noise ratio at the combiner output. Although the solution presented here considers the Nakagami fading environment, the formulation is general and can be easily applied to any other fading channel View full abstract»

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  • Active microwave imaging. I. 2-D forward and inverse scattering methods

    Page(s): 123 - 133
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    Active microwave imaging (MWI) for the detection of breast tumors is an emerging technique to complement existing X-ray mammography. The potential advantages of MWI arise mainly from the high contrast of electrical properties between tumors and normal breast tissue. However, this high contrast also increases the difficulty of forming an accurate image because of increased multiple scattering. To address this issue, we develop fast forward methods based on the combination of the extended Born approximation, conjugate- and biconjugate-gradient methods, and the fast Fourier transform. We propose two nonlinear MWI algorithms to improve the resolution for the high-contrast media encountered in microwave breast-tumor detection. Numerical results show that our algorithms can accurately model and invert for the high-contrast media in breast tissue. The outcome of the inversion algorithms is a high-resolution digital image containing the physical properties of the tissue and potential tumors View full abstract»

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  • Phase-locked-loop control of active microstrip patch antennas

    Page(s): 201 - 206
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    Active patch antennas are simple to fabricate, compact, and low cost, but have inherently poor phase noise and stability. In this paper, a phase-locked loop (PLL) integrated with a 4-GHz active patch antenna was investigated in order to reduce the phase noise and stabilize the frequency of the oscillator. Both these aims were realized by careful integration and optimization of the PLL parameters. Experimental results showed that a phase noise reduction in excess of 55 dB was achieved using this technique. A standalone voltage-controlled oscillator and passive patch technique can provide lower phase noise, but the active patch lends itself to effective integration. Measurement techniques were demonstrated to measure the phase noise and stability of the patch oscillator View full abstract»

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  • Scattering by FSS on anisotropic substrate for TE and TM excitation

    Page(s): 72 - 76
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    The scattering of electromagnetic waves from frequency-selective surfaces (FSS) composed of rectangular conducting patches mounted on uniaxial dielectric anisotropic substrate is investigated by using a full-wave analysis. The moment method is used in combination with the spectral-domain immittance approach to determine reflection and transmission coefficients of the FSS structure as function of the geometry parameters and dielectric anisotropy. The analysis provides very accurate results compared to those presented by others and to those obtained by measurements View full abstract»

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  • Security system for optical communication signals with fiber Bragg gratings

    Page(s): 13 - 16
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    A security system for optical communication signals based on Bragg grating structures is presented in this paper. The technique can be implemented in different levels of sophistication with corresponding cost and technical difficulty. The technique is demonstrated in its simplest version with an array of two fiber Bragg gratings in each side of the optical link. The principle has been tested with a periodic pulse train of 1.4-GHz repetition rate. A simulation that allows the design of more sophisticated systems is also presented and show very good agreement with experimental results View full abstract»

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  • On the effect of IF power nulls in Schottky diode harmonic mixers

    Page(s): 134 - 142
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    Experimental results reveal the existence of a null in the IF output power for certain bias voltage levels in single Schottky diode harmonic mixers at terahertz frequencies. This dramatic loss of IF power is due to a drastic increase of conversion loss and is governed by intrinsic diode parameters, as well as external parameters. For a second harmonic mixer, this is due to a competition of two mixing paths; one is the mixing of the RF with the doubled local oscillator (LO) frequency and the other a mixing of the RF with the LO to an LO sideband followed by a second mixing with the LO, both leading to the IF. In this paper, we present a systematic investigation of and some basic relations between these parameters and the depth and voltage levels where the conversion loss increases. Good agreement is obtained between a simple analysis and the experimental data on second and fourth harmonic mixers View full abstract»

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  • Efficient optical control of millimeter waves in a slot line on semiconductor plasma substrate

    Page(s): 207 - 210
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    Efficient control of millimeter-waves in a slot line on an Si and GaAs substrate is discussed both theoretically and experimentally. The spectral-domain method is used to estimate the propagation and the attenuation constants in the slot line with the density of the optically induced plasma as a parameter. Experiments in the millimeter-wave range of 35-50 GHz are carried out using high-resistivity Si and GaAs wafers with the dimension of 15 mm×30 mm×600 μm. The slot-width could be varied from 0.5 to 2 mm. The attenuation of millimeter waves by over 20 dB can be controlled by optical means using light-emitting diodes with 870 nm wavelength and 68 mW optical power. The experimental results agree considerably well with the theory. The response of millimeter waves with pulsed optical illumination is also examined using a high-power laser diode of 20 W optical power and a pulsewidth less than 100 ns. High-speed response due to optically induced plasma is confirmed for the slot line on GaAs substrate View full abstract»

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  • A simple method to design wide-band electronically tunable combline filters

    Page(s): 172 - 177
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    A new systematic approach for designing wide-band tunable combline filters is presented. New results on tunable combline filter theory are proposed and explicit design formulas, to obtain the filter design parameters from specifications, are included. These design parameters are: center frequency, resonator electrical length, instantaneous bandwidth, and tuning capacitance. The proposed design technique is used to construct an X-band wide-band microstrip tunable filter from 8 to 12 GHz with commercial GaAs FETs as tuning elements. Parasitic effects and simulation problems are also discussed View full abstract»

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  • System impact of the physical length of unapodized chirped fiber Bragg gratings on dispersion compensation

    Page(s): 88 - 93
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    It is shown, for the first time, how the group-delay ripple, due to a pair of identical unapodized dispersion compensating gratings, can be affected by a small change in the physical length of one of the gratings. It is theoretically and experimentally demonstrated that the ripple can be smoothened by a slight difference in length between the gratings. The pair are arranged in a four-port optical circulator in a cascading configuration. System simulations indicate that the performance of the unapodized gratings may be improved by using such a scheme. This has implications for dispersion compensation in high-speed long-haul transmission systems View full abstract»

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  • Investigation of the longitudinal multiconductor transmission line functions for symmetric coupled-microstrip systems

    Page(s): 183 - 190
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    In inhomogeneous multiconductor transmission line (MTL) structures such as coupled microstrip, propagation is characterized by multiple quasi-TEM modes with distinct propagation constants. These "mode delays" cause the MTL functions to exhibit longitudinal behavior that superficially appears problematic in the context of passive lossless reciprocal systems. This paper presents a thorough investigation of the longitudinal MTL functions. Using MTL formulation and computer simulation, we explain the mathematics and physics of mode delays so that their effects are not misinterpreted or attributed to error in the numerical analysis of MTLs View full abstract»

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  • A circuit-fed tile-approach configuration for millimeter-wave spatial power combining

    Page(s): 17 - 21
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (106 KB) |  | HTML iconHTML  

    In this paper, a circuit-fed spatially combined transmitter array is described for operation at 44 GHz. The array contains 256 elements where each element consists of a monolithic-microwave integrated-circuit amplifier and a circularly polarized microstrip patch antenna. The array is constructed using 16-element tile-approach subarrays. Each subarray is a two RF-level (three-dimensional) multichip module containing integrated microstrip patch antennas. The basic construction of the transmitter array resembles tile-approach phased arrays; however, the implementation has been tailored for the power-combining application. The peak performance at 43.5 GHz is equivalent isotropic radiated power of 40.6 dBW (11570 W), effective transmitted power (Peff) of 5.9 W, dc-to-RF efficiency of 7.3%, and system gain of 35 dB View full abstract»

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  • Experimental confirmation of the dynamics of coupled-oscillator arrays and implications for angle-based modulation

    Page(s): 143 - 149
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    This paper describes a set of experimental measurements designed to test the predictions of the continuum theoretical model concerning the dynamics of a linear array of mutually injection-locked voltage-controlled oscillators. The model indicates that the phase distribution evolves according to a diffusion process, the diffusion rate being determined by the inter-oscillator locking range. The theoretical predictions are confirmed by the experimental results. In addition, a discussion of computational predictions of the characteristics of the signal received in the far zone when such an oscillator array excites a linear array of radiating elements is included View full abstract»

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  • Monolithic transistor SPST switch for L-band

    Page(s): 51 - 56
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    A comparison of single-pole single-throw switch topologies is presented in this paper. A three-MESFET monolithic GaAs switch was designed, for 2-GHz operation, fabricated and tested in three different bias conditions: Vbias = 0 (self-bias); Ibias = 0 (floating); and Vbias ≠ 0, Ibias ≠ 0 (biased). It will be shown that a floating configuration presents on-state lower insertion loss (IL) (~1.7 dB). However, the off-state isolation has the same order of magnitude in all three bias conditions (typically 50 dB). Comparing measurements and simulations, the best available nonlinear model for the floating bias operation was selected. Finally, several resonant topologies were studied and a new topology is proposed to increase the off-state isolation without degrading the on-state IL. The advantages and drawbacks of resonant topologies over nonresonant configurations are also discussed, taking into account technology constraints and operation frequency. A solution to reduce the inductor value is proposed View full abstract»

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  • A completely integrated 1.9-GHz receiver front-end with monolithic image-reject filter and VCO

    Page(s): 210 - 215
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    A 1.9-GHz monolithic superheterodyne receiver front-end with 300-MHz IF on-chip tunable image-reject filter and voltage-controlled oscillator (VCO) is presented. Two versions of the receiver were fabricated on a 0.5-μm bipolar process and compared to a previously fabricated version with an off-chip VCO. The two versions are identical, except for the fact that the 2.2-GHz VCO was realized with and without ground-shielded inductors. The receiver that used ground-shielded inductors had a conversion gain of 25.6 dB, a noise figure of 4.5 dB, a third-order input intercept point (IIP3) of -19 dBm, an image rejection of 65 dB, and a phase noise of -103 dBc/Hz at 100-kHz offset. The receiver drew 32.5 mA from a 3-V supply and had a die area of 2.1 mm×1.7 mm. The local-oscillator-IF isolation improved compared to the previously fabricated front-end with an off-chip VCO View full abstract»

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  • A dynamic model for printed apertures in anisotropic stripline structures

    Page(s): 22 - 26
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    This paper presents a full-wave analysis method for printed apertures in anisotropic stripline structures. Both electric and magnetic anisotropy of the most general form are assumed. Working in the Fourier domain, closed-form expressions for the transformed electromagnetic fields are derived. Special attention is dedicated to the particular case of dielectrics with uniaxial anisotropy. In this case, spectral Green's functions in compact and closed form are obtained. Effects of the anisotropic ratio on the input impedance of a printed slot are presented View full abstract»

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  • Carrier reuse with gain compression and feed-forward semiconductor optical amplifiers

    Page(s): 77 - 81
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    The results of two techniques for optical carrier regeneration and wavelength reuse using semiconductor optical amplifiers (SOAs) are presented in this paper. The main objective is to recover an optical carrier by erasing its amplitude modulation. The first technique employs gain compression of deeply saturated SOAs. The second technique uses a feed-forward approach, where a delayed current signal is injected into the SOA with the same shape of the incoming optical pulse. The second technique could be capable to recover the optical carrier with less than 3-dB noise. However, it was observed that the SOA gain recovery time limits the maximum usable bit rate. Theoretical simulation showed good agreement with experimental results View full abstract»

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  • A new model for enhancement-mode power pHEMT

    Page(s): 57 - 61
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    Optimum loading for a power enhancement-mode pseudomorphic high electron-mobility transistor (E-pHEMT) is determined by a systematic harmonic load-pull simulation. The simulation uses a modified Angelov-Parker model that can accurately predict DC, small-signal RF, and power performance of the devices. The optimum second harmonic loading for a 2-mm device is found to be open circuit and the optimum third harmonic is at the third quadrant, which is about 1∠210°. The measured versus modeled results show very good agreement and, therefore, verify the model. The simulation predicts that as high as 80% power-added efficiency can be achieved for E-pHEMT under optimum source and load termination with harmonic tuning View full abstract»

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  • Evolution of leaky modes on printed-circuit lines

    Page(s): 94 - 104
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    The frequency evolution of dominant (quasi-TEM) and higher order modes on an open printed-circuit structure such as a microstrip is examined. Three different mode types are considered, including bound modes (BMs), leaky modes that leak into the surface wave of the background structure, and leaky modes that also leak into space. One of the fundamental goals is to establish the conditions under which one type of mode can transition into another type as the frequency changes. One important conclusion is that the dominant BM can never transition into a leaky mode for a microstrip structure with an isotropic substrate, but such a transition is possible for an anisotropic substrate, observed originally by Tsuji et al. and Shigesawa et al. However, higher order BMs can directly transition into leaky modes, as shown by Oliner and Michalski and Zheng. On other structures such as coplanar strips, where the bound dominant mode exhibits odd symmetry, a transition from a bound dominant mode to a leaky mode is possible, as shown by Shigesawa et al. and Tsjui et al. In addition to examining the mathematical transitions that are possible, the physical continuation of modes is also investigated, by examining the frequency evolution of the currents excited by a practical source. It is concluded that there may be physical continuity between modes, even if there is no mathematical continuity View full abstract»

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  • Barrier enhancement mechanisms in heterodimensional contacts and their effect on current transport

    Page(s): 68 - 71
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    It has been shown that, in a three-dimensional (3D) to two-dimensional (2D) contact system, the quantized nature of the energy of the 2D system imposes important changes on thermionic emission of carriers from a 3D metal to two-dimensional electron gas (2DEG). Interestingly, in actual devices, barrier heights higher than what is theorized based on the first confined state are measured. In this paper, we introduce an additional mechanism that explains barrier height enhancement in 3D-2D contacts, which is due to the repulsive Coulombic force that is exerted by the 2DEG on the thermionically emitted electrons. An analytical derivation of the barrier height due to this effect is given and total thermionic emission current is derived. These results are particularly important for design and understanding of device behavior for low-noise photodetectors in front end optical receivers. The electron cloud model presented for the reservoir of mobile charges that are free to move in response to charged particle or electromagnetic waves implies that any means of interaction that disturbs the equilibrium of the electron cloud have strong signature at the contact, as well as the temporal response of the induced disturbance. This can be effective for low-power-detection applications 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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Meet Our Editors

Editor-in-Chief
Dominique Schreurs
Dominique.Schreurs@ieee.org

Editor-in-Chief
Jenshan Lin
jenshan@ieee.org