Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 1995"
Abstract: A theory for combined differential and common-mode normalized power waves is developed in terms of even and odd mode impedances and propagation constants for a microwave coupled line system. These are related to even and odd-mode terminal currents and voltages. Generalized s-parameters of a two-port are developed for waves propagating in several coupled modes. The two-port s-parameters form a 4-by-4 matrix containing differential-mode, common-mode, and cross-mode s-parameters. A special case of the theory allows the use of uncoupled transmission lines to measure the coupled-mode waves. Simulations verify the concept of these mixed-mode s-parameters, and demonstrate conversion from mode to mode for asymmetric microwave structures. >
780 citations
TL;DR: In this paper, the authors proposed a significantly improved space mapping (SM) strategy for electromagnetic (EM) optimization, which leverages every available EM analysis, producing dramatic results right from the first step, instead of waiting for upfront EM analyses at several base points.
Abstract: We propose a significantly improved space mapping (SM) strategy for electromagnetic (EM) optimization. Instead of waiting for upfront EM analyses at several base points, our new approach aggressively exploits every available EM analysis, producing dramatic results right from the first step. We establish a relationship between the novel SM optimization and the quasi-Newton iteration for solving a system of nonlinear equations. Approximations to the matrix of first-order derivatives are updated by the classic Broyden formula. A high-temperature superconducting microstrip filter design solution emerges after only six EM simulations with sparse frequency sweeps. Furthermore, less CPU effort is required to optimize the filter than is required by one single detailed frequency sweep. We also extend the SM concept to the parameter extraction phase, overcoming severely misaligned responses induced by inadequate empirical models. This novel concept should have a significant impact on parameter extraction of devices.
387 citations
TL;DR: In this paper, a dual-mode multisection distributed feedback semiconductor laser is used to generate high power signals between 40 and 60 GHz with extremely high spectral purity and stability.
Abstract: This paper presents a new approach to the optical generation of millimeter-wave signals using a dual-mode multisection distributed feedback semiconductor laser. This simple device is capable of generating high power signals between 40 and 60 GHz with extremely high spectral purity and stability. The two optical modes produced by this laser are heterodyned on an ultrafast photodiode to give a beat signal at the mode difference frequency. The phase noise of the beat signal is greatly reduced by phase-locking the modes using an electrical drive signal applied to the laser at a subharmonic of the beat frequency. Millimeter-wave signals are obtained with a linewidth of less than 10 Hz, a phase noise of less than -85 dBc/Hz at 100 kHz offset, and a locking range of about 500 MHz. Millimeter-wave fiber-radio systems are seen as a major application area for these new compact optical sources. >
280 citations
TL;DR: This paper presents a new approach to microwave circuit optimization and statistical design featuring neural network models at either device or circuit levels, which has the capability to handle high-dimensional and highly nonlinear problems.
Abstract: The trend of using accurate models such as physics-based FET models, coupled with the demand for yield optimization results in a computationally challenging task. This paper presents a new approach to microwave circuit optimization and statistical design featuring neural network models at either device or circuit levels. At the device level, the neural network represents a physics-oriented FET model yet without the need to solve device physics equations repeatedly during optimization. At the circuit level, the neural network speeds up optimization by replacing repeated circuit simulations. This method is faster than direct optimization of original device and circuit models. Compared to existing polynomial or table look-up models used in analysis and optimization, the proposed approach has the capability to handle high-dimensional and highly nonlinear problems. >
277 citations
TL;DR: The possibility to apply millimeterwave for various applications in the commercial arena has a long history, as the advantages being offered by such systems have been known for more than three decades as discussed by the authors.
Abstract: The possibility to apply millimeterwaves for various applications in the commercial arena has a long history, as the advantages being offered by such systems have been known for more than three decades. Within the last five years the necessity of turning their attention away from the military sector towards commercial products has caused more and more companies to look at millimeterwave communications and automotive radar. By chance, this was accompanied by the advent of low-cost integration procedures, i.e., hybrid- and monolithic-integration techniques, respectively. Thus, the necessary technology is mature and available now, opening a wide field of deployment areas. Millimeterwave systems have found an ever increasing interest, due to their specific advantages, as well as the lack of frequencies for new services. While the military market is decreasing, commercial applications in the area of microwave tags, radio communication, and traffic control are increasing rapidly. The two most important application areas right now are: 38 GHz short-haul transmission links for PCN installations, an already valuable niche market, and 77 GHz automotive radar sensors-simple collision warning devices and intelligent cruise control sensors as well-which have the largest market potential for the very near future. >
251 citations
TL;DR: In this paper, the authors presented the closed-form Green's functions of the vector and scalar potentials in the spatial domain for the sources of horizontal electric, magnetic, and vertical electric dipoles embedded in general, multilayer, planar media.
Abstract: The closed-form Green's functions of the vector and scalar potentials in the spatial domain are presented for the sources of horizontal electric, magnetic, and vertical electric, magnetic dipoles embedded in general, multilayer, planar media. First, the spectral domain Green's functions in an arbitrary layer are derived analytically from the Green's functions in the source layer by using a recursive algorithm. Then, the spatial domain Green's functions are obtained by adding the contributions of the direct terms, surface waves, and complex images approximated by the Generalized Pencil of Functions Method (GPOF). In the derivations, the main emphasis is to put these closed-form representations in a suitable form for the solution of the mixed potential integral equation (MPIE) by the method of moments in a general three-dimensional geometry. The contributions of this paper are: 1) providing the complete set of closed-form Green's functions in spectral and spatial domains for general stratified media; 2) using the GPOF method, which is more robust and less noise sensitive, in the derivation of the closed-form spatial domain Green's functions; and 3) casting the closed-form Green's functions in a form to provide efficient applications of the method of moments. >
244 citations
TL;DR: The problem of beam squinting in phased arrays is analyzed and the concept of true-time delay is introduced, and the advantages of realizing variable delay lines by optical rather than by microwave means are reviewed.
Abstract: This tutorial review paper deals with various methods for solving a basic problem of wideband phased arrays, i.e. beam squinting, using optical technologies. The problem of beam squinting in phased arrays is analyzed and the concept of true-time delay is introduced. The advantages of realizing variable delay lines by optical rather than by microwave means are reviewed, together with principles of operation. Among the techniques described are switched-path length delay lines, fiber stretchers, tunable lasers with highly dispersive fiber, and coherent techniques incorporating dispersive delay. Recent experimental results are discussed in the light of practical system requirements. >
230 citations
TL;DR: In this article, the detrimental effects of chromatic and polarization mode dispersion on systems using single-laser-based optical self-heterodyning for generation and transport of millimeter (mm)-wave signals are described and experimentally verified.
Abstract: This paper describes the detrimental effects of chromatic and polarization mode dispersion (PMD) on systems using single-laser-based optical self-heterodyning for generation and transport of millimeter (mm)-wave signals. The decrease of the generated mm-wave power due to chromatic dispersion in conjunction with nonnegligible laser phase noise is calculated and experimentally verified. Considering statistical properties of the PMD an analytical expression for the cumulative probability distribution of the power penalty is found and used to determine the required system margin for a given system outage rate. Furthermore, two system experiments using ASK and DPSK modulation scheme, respectively, are presented showing no limitation due to the dispersion effects. >
195 citations
TL;DR: In this paper, the authors discuss recent results in the development of miniature filters using a solidly mounted resonator (SMR) concept wherein the acoustic resonator is isolated from the substrate with a sequence of quarter wavelength thick layers that form a reflector.
Abstract: Miniature filters have been under development for wireless applications from 500 MHz to over 6 GHz using thin piezoelectric films on common substrates. This paper discusses recent results in the development of miniature filters using a solidly mounted resonator (SMR) concept wherein the acoustic resonator is isolated from the substrate with a sequence of quarter wavelength thick layers that form a reflector. The SMR concept is discussed in detail and applications to filters is presented. Ladder filters have been demonstrated with insertion losses in the 3 dB range using aluminum nitride films for the piezoelectric and appropriate substrates such as silicon, sapphire, and glass. The ladder filters reported consist of interconnected series and shunt resonators forming a monolithic structure on a single die of comparable size to an integrated circuit.
189 citations
TL;DR: In this paper, the authors evaluate the potential of using high-resistivity silicon as a low-cost low-loss microwave substrate through an experimental comparative study and demonstrate that the losses of a coplanar transmission line (CPW) realized on high resistivity (3 k to 7 k /spl Omega/-cm) silicon substrates are comparable to the losses realized on a GaAs substrate covered with insulators.
Abstract: Silicon has many advantages as a microwave substrate material including low cost and a mature technology. The aim of this paper is to evaluate the potential of using high-resistivity silicon as a low-cost low-loss microwave substrate through an experimental comparative study. Coplanar waveguides fabricated on Si, GaAs, and quartz substrates are tested and their characteristics are compared. Microwave spiral inductors and meander lines are also fabricated on various substrates, and their performance is also analyzed. The results demonstrate that the losses of a coplanar transmission line (CPW) realized on high-resistivity (3 k to 7 k /spl Omega/-cm) silicon substrates are comparable to the losses of a CPW realized on a GaAs substrate covered with insulators. Furthermore, measured unloaded Q's of microwave inductive structures on high-resistivity silicon substrates are comparable to the measured unloaded Q's of the same structures on GaAs and on quartz. This paper demonstrates that high-resistivity Si can be used as a microwave substrate. >
171 citations
TL;DR: In this paper, a simple fiber-optic link with a representative set of link parameters and a variety of electrooptic modulators: simple Mach-Zehnder, linearized dual and triple MZHnder, simple directional coupler (two operating points), and linearized directional coupling with one and two dc electrodes are compared.
Abstract: Intermodulation and harmonic distortion are calculated for a simple fiber-optic link with a representative set of link parameters and a variety of electrooptic modulators: simple Mach-Zehnder, linearized dual and triple Mach-Zehnder, simple directional coupler (two operating points), and linearized directional coupler with one and two dc electrodes. The resulting dynamic ranges, gains, and noise figures are compared for these modulators. A new definition of dynamic range is proposed to accommodate the more complicated variation of intermodulation with input power exhibited by linearized modulators. The effects of noise bandwidth, preamplifier distortion, and errors in modulator operating conditions are described. >
TL;DR: In this article, a six-port phase/frequency discriminator (SPD) was used in conjunction with a digital signal processor (DSP) to perform various PSK and QAM demodulations directly at microwave and millimeter-wave frequencies.
Abstract: A novel digital millimetric receiver (DMR) scheme is introduced. Using a six-port phase/frequency discriminator (SPD) in conjunction with a digital signal processor (DSP), the receiver performs various PSK and QAM demodulations directly at microwave and millimeter-wave frequencies. An important feature of the new DMR is that hardware imperfections such as phase/amplitude imbalance are readily eliminated by a simple calibration procedure. The concept is proved through computer simulation and measurements at 26.5 GHz. This receiver scheme is proposed for small/medium capacity digital terminals typically found in various wireless communication networks.
TL;DR: In this article, a combined finite difference time domain model for the electromagnetic and heat transfer processes of microwave cooking, tempering, and pasteurizing of foods is presented, including temperature dependence of the electrical and thermal properties of the food product.
Abstract: Microwave cooking, tempering, and pasteurizing of foods involves several complex and interacting physical phenomena. Although such processes are widely used, the interactions between the food product, packaging, and the microwave oven itself are particularly complicated, are not well understood, and applicable simulation tools are lacking. In this contribution we describe a combined finite difference time domain model for the electromagnetic and the heat transfer processes which include temperature dependence of the electrical and thermal properties of the food product. This model is validated by comparison to experiment. >
TL;DR: In this article, the authors examined the conductor loss and effective dielectric constant of microshield lines and presented results on transitions to conventional coplanar waveguide, right-angle bends, different stub configurations, and lowpass and bandpass filters.
Abstract: Several millimeter-wave passive components have been fabricated using the microshield transmission line geometry, and their performance is presented herein. Microshield is a quasi-planar, half-shielded design which uses a thin dielectric membrane (1.5 /spl mu/m) to support the conducting lines. This approach provides a nearly homogeneous, air-filled environment and thus allows extremely broad-band TEM operation. This paper examines the conductor loss and effective dielectric constant of microshield lines and presents results on transitions to conventional coplanar waveguide, right-angle bends, different stub configurations, and lowpass and bandpass filters. Experimental data is provided along with numerical results derived from an integral equation method. The microshield line is shown to be very suitable for high performance millimeter and submillimeter-wave applications. >
TL;DR: In this article, a true time-delay beamformer based on a fiber-optic dispersive prism is developed and characterized for the control of an ultrawideband time-steered array antenna.
Abstract: A true time-delay beamformer based on a fiber-optic dispersive prism is developed and characterized. The beamformer is used to control an ultrawideband time-steered array antenna, which is a significant improvement over inherently narrowband phased-array antennas. The time-steered transmitter antenna consists of eight broadband spiral elements in a sparsely-populated array. In transmit mode the bandwidth is microwave-component limited to 2-18 GHz. The transmitter shows an unprecedented performance with >100/spl deg/ azimuth steering and no observed squint over the full frequency range. We also extend the beamformer functionality and demonstrate, we believe for the first time, fully-independent dual-beam dual-frequency ultrawideband antenna transmitter operation. Furthermore, the beamformer is shown to be capable of controlling the transmitter under pulsed operation with microwave pulse-widths as short as 75 ps. In the phase-steered receive mode, the antenna is component-limited to two elements and a frequency range of 6-16 GHz. However, we can still demonstrate squint-free receiver steering over >70/spl deg/ azimuth over the full available frequency range. >
TL;DR: In this article, the CAD oriented closed form analytical expressions for characteristic impedance per unit length capacitance and relative effective dielectric permittivity of top and bottom shielded multilayered coplanar waveguides are derived for a wide verity of CPW structures.
Abstract: Conformal mapping technique is used to obtain CAD oriented closed form analytical expressions for characteristic impedance per unit length capacitance and relative effective dielectric permittivity of top and bottom shielded multilayered coplanar waveguides. Analytical expressions are deduced for a wide verity of CPW structures. >
TL;DR: In this paper, a detailed phenomenological theory for the determination of conversion properties is presented, which is capable of predicting the frequency-conversion loss rather accurately for arbitrary bias by examining the I-V characteristic, Knowing the electron temperature relaxation time, and using parameters derived from the I -V-characteristic also allows to predict the -3-dB IF bandwidth.
Abstract: A study has been done of microwave mixing at 20 GHz using the nonlinear (power dependent) resistance of thin niobium strips in the resistive state. Our experiments give evidence that electron-heating is the main cause of the nonlinear phenomenon. Also a detailed phenomenological theory for the determination of conversion properties is presented. This theory is capable of predicting the frequency-conversion loss rather accurately for arbitrary bias by examining the I-V characteristic, Knowing the electron temperature relaxation time, and using parameters derived from the I-V-characteristic also allows us to predict the -3-dB IF bandwidth. Experimental results are in excellent agreement with the theoretical predictions. The requirements on the mode of operation and on the film parameters for minimizing the conversion loss (and even achieving conversion gain) are discussed in some detail. Our measurements demonstrate an intrinsic conversion loss as low as 1 dB. The maximum IF frequency defined for 3-dB drop in conversion gain, is about 80 MHz. Noise measurements indicate a device output noise temperature of about 50 K and SSB mixer noise temperature below 250 K. This type of mixer is considered very promising for use in low-noise heterodyne receivers at THz frequencies. >
TL;DR: In this paper, the synthesis and realization of an analog-phase shifter, delay line, attenuator, and group delay synthesizer is presented, all implemented using the same generic single stage reflection topology.
Abstract: The synthesis and realization of an analog-phase shifter, delay line, attenuator, and group delay synthesizer-are presented. These variable control devices are all implemented using the same generic single stage reflection topology. The optimum conditions of operation have been determined and the corresponding group delay behaviors have been investigated to produce simple design equations. As proof-of-concepts, monolithic technology has been used to realize an X-band, phase shifter, delay line, and attenuator. Hybrid technology has been used to realize an L-band, group-delay synthesizer. Because of the high levels of performance measured, these control devices are ideally suited for use as general building blocks in adaptive signal processing applications, including large phased array applications. >
TL;DR: In this article, the authors present new design dimensions for the ridge waveguide septum polarizer and demonstrate its influence on the polarizer performance, including a stepped approach for extremely thick septa, optimizing components without the need for additional phase-adjusting structures, and providing application engineer with some design guidelines.
Abstract: This contribution presents new design dimensions for the ridge waveguide septum polarizer. Emphasis is placed first, on including the finite septum thickness in the analysis; second, demonstrating its influence on the polarizer performance; third, including a stepped approach for extremely thick septa; fourth, optimizing components without the need for additional phase-adjusting structures; and fifth, providing the application engineer with some design guidelines. Examples for varying septum thickness and/or number of sections are given for C-, X-, R120-, Ku- and K-band applications. The analysis is based on an efficient mode-matching technique. Evolution-strategy methods are used for optimization. Both algorithms are translated into PC-operational software. Results are compared with previously published theoretical/experimental polarizer data and with a finite-element analysis, and are found to be in good agreement. >
TL;DR: In this article, a planar microwave and millimeter-wave inductors and capacitors have been fabricated on high-resistivity silicon substrates using micro-machining techniques.
Abstract: Planar microwave and millimeter-wave inductors and capacitors have been fabricated on high-resistivity silicon substrates using micro-machining techniques The inductors and capacitors are suspended on a thin dielectric membrane to reduce the parasitic capacitance to ground The resonant frequencies of a 12 nH and a 17-nH inductor have been increased from 22 GHz and 17 GHz to around 70 GHz and 50 GHz, respectively We also report on the design and measurement of a new class of stripline filters suspended on a thin dielectric membrane Interdigitated filters with 43% and 5% bandwidth have been fabricated and exhibit a port-to-port 07 dB and 20 dB loss, respectively, at 14-15 GHz The micro-machining fabrication technique can be used with silicon and GaAs substrates in microstrip or coplanar-waveguide configurations to result in planar low-loss lumped elements and filters suitable for monolithic integration or surface mount devices up to 100 GHz >
TL;DR: In this paper, a rigorous boundary contour mode-matching (BCMM) method is presented for the efficient calculation of the modal scattering matrix of arbitrarily shaped Hand E-plane discontinuities, junctions, and/or obstacles in rectangular waveguides.
Abstract: A rigorous boundary contour mode-matching (BCMM) method is presented for the efficient calculation of the modal scattering matrix of arbitrarily shaped Hand E-plane discontinuities, junctions, and/or obstacles in rectangular waveguides. For the inhomogeneous waveguide region with general contour, the field is expanded in the complete set of cylindrical wave functions. The full-wave expansion allows the immediate rigorous inclusion of cascaded structures such as combined H- and E-plane bends. The efficiency of the method is demonstrated at the rigorous design of useful waveguide components which could not be modeled by mode-matching technique so far: cylindrical post-compensated H-plane T-junction, mitered H-plane and E-plane bends of arbitrary angle, cascaded H-/E-plane bends, circular post-coupled filter, E-plane filter with rounded corners, 180/spl deg/ rat race structure, and side-coupled dual TE/sub 311//TE/sub 113/-mode filter. The theory is verified by measurements. >
TL;DR: The Advanced Microwave Sounding Unit (AMSU) is being developed to fly on the new generation of NOAA polar orbiters due to be launched in the latter half of the 1990's as discussed by the authors.
Abstract: The Advanced Microwave Sounding Unit, AMSU, is being developed to fly on the new generation of NOAA polar orbiters due to be launched in the latter half of the 1990's. The UK Meteorological Office (UKMO) are procuring the high frequency component of AMSU (AMSU-B) with five channels in the range 88-191 GHz. In order to determine the radiometric performance and verify the method for calibration of AMSU-B an extensive series of tests have been performed by the UKMO on the engineering and three flight models. The instruments were placed in a 3 m thermal-vacuum chamber where their temperature could he controlled over the full range expected in orbit and an Earth target and a space target could be viewed. For the first flight model the measured Ne/spl Delta/T values were all >
TL;DR: In this paper, the authors explored the power dissipation limit of traveling-wave photodetectors (TWPDs) and developed a small-signal steady-state model that includes the effects of electrical propagation losses along the detector.
Abstract: The traveling-wave photodetectors (TWPD) discussed here offer theoretical quantum efficiencies approaching 100% while maintaining a very large electrical bandwidth. Additionally, they are capable of dissipating the high-power levels required for large dynamic range applications. In this paper, the power dissipation limit of the TWPD is explored. A small-signal steady-state model is developed that includes the effects of electrical propagation losses along the detector. Fabrication details are presented and experimental data shows a 3/spl times/1250 /spl mu/m/sup 2/ detector with a 4.8-GHz bandwidth. >
TL;DR: In this article, a full wave model of conducting posts in rectangular waveguides yielding their generalized S-matrix is presented by cascading the generalized scattering matrices of the posts and waveguide discontinuities, slot couplings between two combline resonators are obtained.
Abstract: A full wave model of conducting posts in rectangular waveguides yielding their generalized S-matrix is presented. By cascading the generalized scattering matrices of the posts and waveguide discontinuities, slot couplings between two combline resonators are obtained. The validation and accuracy of the method are confirmed by comparing the numerical results with measured data. It is shown that both electric and magnetic couplings can be obtained by changing the slot positions, and the electric coupling is more sensitive to the tuning screw than magnetic coupling. A 6-pole slot coupled combline filter with asymmetrical transmission zeros is designed and built. Excellent filter responses are obtained.
TL;DR: In this article, it is shown how the synthesis may be carried out by applying a new equivalent circuit identity to transform a lumped element filter into a cross-coupled CQ filter.
Abstract: Previous designs for CQ filters have required matrix rotation operations on the coupling matrix of the canonic form of the cross-coupled filters. This is a rather awkward and not entirely satisfactory process since the theory is not general, requiring the application of equations specific to each order of filter, and in fact has been developed only as far as even order 10. A new direct CQ synthesis has now been discovered having no such limitations. It is shown how the synthesis may be carried out by applying a new equivalent circuit identity to transform a lumped element filter into a cross-coupled CQ filter.
TL;DR: In this paper, a 20 GHz bandwidth optoelectronic mixer has been constructed and characterized, and the mixer was then incorporated into a simple superheterodyne receiver architecture, which was shown to have a tangential sensitivity of -66 dBm and a compressive dynamic range of 44 dB.
Abstract: Optoelectronic mixers can exhibit a very wide bandwidth of operation with significantly reduced third-order intermodulation products. A 20 GHz bandwidth optoelectronic mixer has been constructed and characterized. The third-order intermodulation terms were demonstrated to be more than 70 dB below the IF output. The mixer was then incorporated into a simple superheterodyne receiver architecture, which was shown to have a tangential sensitivity of -66 dBm and a compressive dynamic range of 44 dB. System limitations and possible improvements are discussed. >
TL;DR: In this article, the merging of RADAR and LIDAR technologies in the constitution of a hybrid LidAR-RADAR detection scheme has been described, which has reduced incoherent backscatter clutter by 17 dB in laboratory experiments and related computer simulations.
Abstract: Since microwaves do not penetrate water, RADAR, the principal tool for remote sensing of the earth and atmosphere, cannot be used directly for the detection of underwater objects. Currently, aerial light detecting and ranging (LIDAR) systems are therefore preferred for the detection and ranging of objects submerged in the sea. LIDAR provides for large area coverage at high speed, but it lacks coherent detection capability, a shortcoming that severely limits system sensitivity and underwater target contrast. In response to this problem, this paper details the merging of RADAR and LIDAR technologies in the constitution of a hybrid LIDAR-RADAR detection scheme. This new sensor configuration has reduced incoherent backscatter clutter by 17 dB in laboratory experiments and related computer simulations. >
TL;DR: In this article, a simple way to determine a small-signal equivalent circuit of high-electron mobility transistors (HEMTs) is proposed, where the intrinsic elements determined by a conventional analytical parameter transformation technique are described as functions of extrinsic elements.
Abstract: A simple way to determine a small-signal equivalent circuit of High Electron Mobility Transistors (HEMTs) is proposed. Intrinsic elements determined by a conventional analytical parameter transformation technique are described as functions of extrinsic elements. Assuming that the equivalent circuit composed of lumped elements is valid over the whole frequency range of the measurements, the extrinsic elements are iteratively determined using the variance of the intrinsic elements as an optimization criterion. Measurements of S-parameters up to 62.5 GHz at more than 100 different bias points confirmed that the HEMT equivalent circuit is consistent for all bias points. >
TL;DR: In this article, a new variety of millimeter-wave Fresnel-zone plate lens with enhanced focusing quality is described, where each full-wave zone of the lens is divided into four quarter-wave subzones, which are covered by dielectric rings having equal thickness but different permittivities.
Abstract: A new variety of millimeter-wave Fresnel-zone plate lens with enhanced focusing quality is described Each full-wave zone of the lens is divided into four quarter-wave subzones, which are covered by dielectric rings having equal thickness but different permittivities More practical equations are derived for the radii of the zones, and for the thickness of the lens by taking into account the angle of incidence of the electromagnetic wave A Fresnel-zone plate antenna (FZPA) consisting of a quarterwave lens and a scalar feed is developed and analysed theoretically Equations for the aperture field and far field are derived using multiple ray tracing through dielectric plates and vectorial Kirchhoff diffraction theory, respectively It is demonstrated that the proposed transmissive-type FZPA has an aperture efficiency of more than 50% in the 60 GHz frequency band This computed efficiency agree with the measured overall efficiency reported by other researchers for an X-band quarter-wave reflector-type FZPA
TL;DR: In this article, the authors investigate the generation of signals using pulsed semiconductor lasers for application in millimeter-wave (mm-wave) wireless links and demonstrate the application of this method to the feeding of mm-wave wireless links incorporating microstrip patch antennas.
Abstract: We investigate the generation of signals using pulsed semiconductor lasers for application in millimeter-wave (mm-wave) wireless links. The generation of mm wave harmonic frequencies in both mode-locked and gain-switched lasers is considered and a method to generate mm-wave modulated optical signals with modulation depths approaching 100% is implemented. The technique uses optical filtering to select only two optical modes in the pulsed laser spectrum that beat together in a highspeed photodiode. The application of this method to the feeding of mm-wave wireless links incorporating microstrip patch antennas is demonstrated. These optically fed links have application in indoor wireless LAN's and optical fiber microcellular systems. >