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A broadband antenna for GSM1800-UMTS base stations with multiple switchable beams in azimuth is presented in this paper. The multiple beams are obtained by means of a broadband Butler matrix. The radiating element is broadband and consists of two stacked patches. The elevation pattern is shaped with null filling and upper lobe reduction that has been achieved by means of a broadband corporate feed network implemented in microstrip technology. Photographs and measurements of the manufactured prototypes are presented confirming that the design of all of the elements is correct. Index Terms--Broadband antennas, multibeam antennas, planar arrays.

The accuracy of a phase-retrieval procedure for microwave beams was analyzed and verified using an 84-GHz quasi-optical beam transmitted by a corrugated waveguide. The output intensity and phase profiles of the beam were directly measured with a microwave receiver. The beam intensity was also measured at several planes and the data were used with a phase-retrieval algorithm to yield an independent estimate of the phase. Moment and matching coefficient methods were used to analyze the retrieved profiles. In the higher order moment analysis, the intensity profiles, which were calculated from the retrieved phase profiles, coincided well with the measured profiles in terms of the beam size, asymmetric property (skewness), and flatness/peakedness (kurtosis) over the entire profile. Analysis indicated that the mode content of the beam obtained by phase retrieval matched that of the direct measurement with a matching coefficient of 0.97 using both the intensity and phase profiles. Index Terms--Electron cyclotron heating (ECH), Gaussian beam, gyrotron, phase measurement, phase retrieval, quasioptical mirror.

A scheme is presented to perform longitudinal and transverse spatial phase coding of continuous-wave optical beams. This phase coding scheme has an information storage capacity which scales with the power of the read-out optical beam, and can be extended to implement a multiplex array detector.

Parabolic cylindrical reflectors (PCRs) can have a large field of view, for example a 15 m reflector can access an area of 1[degrees] by 120[degrees] at 1.4 GHz. It is seen that the radiation pattern is asymmetric. This causes problems in situations where the radiation pattern rotates with time, such as radio astronomy. The rotation of the radiation pattern limits the field of view. In this paper a normalized signal to noise ratio is calculated for a full observation and this is then used to determine the field of view. The greatest variation occurs where the radiation pattern of a single feed element is used. The variation is reduced by RF beamforming. If the radiation pattern has an aspect ratio of 2.5:1 the observed field of view is approximately constant and has a value that is three times larger than that of an equivalent parabolic dish. Index Terms--Earth rotational synthesis, field of view, sensitivity, parabolic cylindrical reflector (PCR).

Blind source separation (BSS) and blind beamforming schemes attempt to separate additive source signals, collected at a sensor array, and their direction-of-arrival (DOA). To this extent, many different and powerful algorithms have been produced to accomplish these tasks. However, unlike an optimal or adaptive method, an algebraic method for BSS and blind beamforming has the relative advantage of simplicity. This paper investigates such a technique that provides closed-form, algebraic expressions for BSS and beamforming in terms of performance and reliabity. We provide these results, as well as a summary of the properties, and possible Uses for this technique, in contrast to more optimal, adaptive techniques.

A coarray-based near-field, wideband synthetic aperture beamformer using stepped-frequency signal synthesis and post-data acquisition processing is presented. While coarray techniques offer significant reduction in the number of array elements for a given angular resolution, the hybrid subarray-stepped frequency realization of wideband systems simplifies implementations and offers flexibility in beamforming. Proof of concept is provided using real data collected in an anechoic chamber for several pulse shapes and array weightings.

An algorithm for adaptation of the complex baseband weights of a transmit antenna array is described and discussed.

The focal shift and focal switch of flattened Gaussian beams (FGB), focused by an aperture bifocal lens, are investigated and discussed.

A new type of smart antenna array receiver with adaptive beamforming is proposed. The novel system offers a drastic reduction in hardware requirements for the smart antenna system through the use of a new Spatial Multiplexing of Local Elements (SMILE) scheme. In this scheme, a single element of the array is sequentially connected to signal processing circuitry in order to sample the incoming modulated carrier. The sampling rate is higher than the signal bandwidth so that the information of the original signal can be fully restored in the post stages using low-pass filters. This system offers an N times reduction in RF hardware for an N-element array. A four-element prototype is built. System principles, SNR, advantages, and hardware, including a new type of array feed network, are discussed. The system performance is validated through a link test with digitally modulated data. Index Terms--Digital beamforming (DBF), smart antenna, Spatial Multiplexing of Local Elements (SMILE), spatial multiplexing.

Accurate computation of the propagation constants and field distributions of various modes in nonlinear optical dielectric waveguides is discuused.

An effective adaptive null-forming arrangement for two nearby microphones in endfire orientation is proposed. Its implementation and tests are discussed.

Design of space-time receivers is discussed. The receivers preserve the whiteness of channel noise while reducing the intersymbol interference (ISI) so that optimum maximum a posteriori (MAP) equalization can be performed on the receiver output.

A full-vectorial imaginary-distance beam propagation technique is described. It is based on a finite element scheme with curvilinear edge/nodal hybrid elements and anisotropic perfectly matched layers (PML), and it is used to investigate the propagation characteristics in holey fibers (HL).

An optical-modeling procedure is proposed, for calculating vertical-cavity surface-emitting lasers (VCSEL) modes. The procedure is based on the bidirectional beam-propagation method.

Results of numerical modeling of tapered amplifiers with different geometries are discussed. Simulations are based on extended Maxwell-Bloch equations (MBE) and have to do with spatial and spectral hole burning, carrier heating, and many-body interactions, as well as dynamic wave-mixing between a light signal injected in a laser amplifier and the amplified spontaneous emission.

Research developing a method for implementing quadratic inequality constraint with updating of recursive least squares aimed at improving robustness of locating errors in sensor parameters of beamformers is presented. Particular attention is given to the benefits if better suppression of interference.

A discussion of a single-mirror interferometer with spatial separation of the two arms is presented. Topics include refractive index, beam intensity, and thermal and acoustic fluctuations.

The quasi-optical antenna mixer system transforms an RF signal into an intermediate frequency signal just after it spatially receives the RF signal and the local oscillator's (LO) signal. In this paper, we present a novel beam-scanning system using the quasi-optical antenna mixer array and describe its principle of operation and the experimental results in the microwave band. The arrival direction of RF signals can be controlled by adjusting the LO incident angle and/or the LO frequency without implementing RF circuits such as phase shifters. Therefore, the novel beam-scanning system has no loss due to RF circuits and can be easily designed because of its simple composition. Index Terms - Beam scanning, coplanar waveguide, microstrip antenna, phased array, quasi-optical antenna mixer.

The behavior of arrays of coupled oscillators has been previously studied by computational solution of a set of nonlinear differential equations describing the time dependence of each oscillator in the presence of signals coupled from neighboring oscillators. The equations are sufficiently complicated in that intuitive understanding of the phenomena which arise is exceedingly difficult. We propose a simplified theory of such arrays in which the relative phases of the oscillator signals are represented by a continuous function defined over the array. This function satisfies a linear partial differential equation of diffusion type, which may be solved via the Laplace transform. This theory is used to study the dynamic behavior of a linear array of oscillators, which results when the end oscillators are detuned to achieve the phase distribution required for steering a beam radiated by such an array. Index Terms - Beam steering, coupled oscillators, injection locked, phased array.

Asymmetrical Gauss-Hermite beam-mode analysis is presented to investigate the hexagonal horn. The fractional power in the fundamental beam mode is approximately 86%. The near- and far-field radiation patterns are calculated. The high fractional power in the fundamental beam mode of the horn indicates that it can be used as an efficient Gaussian beam launcher in quasi-optical systems. Index Terms - Horn antennas.

The use of a tilted mirror to improve the performance of power lasers by discriminating against higher order lateral modes was described. Interference between higher order modes and the fundamental lateral mode has been known to cause beam steering. A model was developed to calculate the reflectivity seen by different modes in fiber pump laser structures. Results showed that proper engineering of tilted mirrors improved the performance of power lasers.

The spectral changes of a Gaussian Schell-model beam caused by the Wolf effect were investigated. The spectral shift was characterized by means of transverse profiles and isoshift lines. Results showed that loci were present when there was no spectral change while loci were absent when there was a maximum shift. This spatial representation can be suitable for such areas as laser Doppler radar systems and high-resolution spectroscopy.

A phase-conjugating mirror based on stimulated Brillouin scattering was used to boost the beam quality of a single-rod Nd:YAG laser near the diffraction limit. The nonlinear reflectivity of the phase-conjugating mirror Q-switched the laser and considerably increased the beam diameter. The stimulated Brillouin scattering mirror combined with a highly selective aperture framework resulted in stable mode operation and increased efficiency via large mode volume.

A cumulant-based blind beamformer for recovery of statistically independent narrowband source signals in the presence of coherent multipath propagation has been developed. The approach is based on the observation that for a blind beamformer, the presence of coherent multipaths is equivalent to the case of independent sources with a different steering matrix. Such method is applicable to any arbitrary array configuration. Furthermore, it maximizes signal-to-interference plus noise ratio.

We report the development and demonstration of the first true time-delay (TTD) fiber-optic beamformer for ultrawide-band antenna receive operation. The beamformer is based on a dispersive-fiber prism configuration that properly time delays the signals originating at each receiving element for coherent combining in the microwave domain. The time-steered receive antenna consists of eight spiral elements arranged into a one-dimensional (1-D) sparsely populated array. The receive array shows an instantaneous bandwidth of 6-18 GHz, limited by the available matched microwave amplifiers. The array performance is measured in an anechoic chamber and exhibits unprecedented squint-free steering over an azimuth scan of 120 [degrees] over the full frequency range. Index Terms - Antenna array feeds, phased arrays, optical control, optical fiber delay lines.

A technique for constructing the finite difference schemes of the beam propagation method at the boundary of the computational window retains the propagation matrices within longitudinal homogeneous sections. The involvement of only the refractive indexes and mesh parameters helps the approach to avoid tedious adjustments, reducing computational time. The schemes do not depend on the computed fields and facilitate a similar treatment of both interior and boundary points. The method can be easily implemented for both two- and three-dimensional structures.

We report a first demonstration of a fiber-optic beamformer for independent two-dimensional (2-D) true time-delay steering of a transmitter array. The fiber-optic beamformer is based on a simple dispersive prism optical delay approach, with separate azimuth and elevation control stages. The azimuth dispersive prism stage includes an amount of dispersion in each link proportional to the corresponding column position in the array. The microwave signals, properly time-delayed for azimuth steering, are amplified and serve as inputs to identical dispersive prisms feeding the elements in each column. The elevation dispersive prism stages include an amount of dispersion in each link proportional to the corresponding row position in the array. Each time-delayed microwave signal feeds a single flared-notch element in a 4 x 4 array. The 2-D array pattern measurements in an anechoic chamber clearly demonstrate independent [+ or -] 30 [degrees] azimuth and [+ or -] 30 [degrees] elevation steering. There is no observed squint over the microwave-component determined bandwidth of 6-18 GHz.

Scanning of the rotation angle of a locus derivative is required in fan-beam reconstruction using projection data obtained from noncircular scanning locus. Geometrical techniques of circular equispatial fan-beam reconstruction formula yields a derivative-free noncircular fan-beam reconstruction formula which is similar to the circular formula except for the source-to-origin distance which is a function of the rotation angle.

A method is described for the synthesis of planar array antennas with prescribed contoured beams. The technique utilizes a transformation which divides the problem into two decoupled subproblems. One subproblem involves the determination of certain coefficients of the contour transformation in order to achieve the required footprint contours. The number of coefficients which need to be used depends on the complexity of the desired contour, but is very small in comparison to the number of planar array elements. The other subproblem consists of a linear array shaped beam synthesis, for which there already exist powerful methods for determining appropriate element excitations. The size required for this prototype linear array depends on the number of contour transformation coefficients used and the size of the final planar array. Simple formulas then determine the final planar array excitations from the information forthcoming from the above two subproblem solutions.

The beam quality and propagation characteristics of the output beam from a multimode stable-cavity laser are studied. Experimental beam propagation measurement for the output beam of a coaxial electrical discharge CO2 laser are performed. The fundamental beam parameters are then evaluated using the geometrical parameters of the stable resonator. Results show that the equipartition of the the laser's ouput power over the full set of tranverse modes in the cavity aperture is strongly dependent on the device's gain profile.

A new method for optimizing the designs of photonic circuits is presented. The method, known as the semivectorial finite-different beam propagation method, solves the wave equation that determines how the optical beam propagates on a dielectric substrate in an alternating manner. It is also capable of meeting the boundary conditiions of individual polarizations without splitting off the phase term. Numerical results demonstrate the applicability of the proposed method.

This paper describes a simple, systematic procedure for designing linear constraints in minimum variance beamformers which allows an arbitrary specification of the quiescent response - the beamformer response when only white noise is present. In this approach, the first constraint is dedicated to the imposition of a desired quiescent response, and additional constraints are included to assure proper reception of the desired signal. The function of these additional constraints is to make the overall beamformer response equal the quiescent response in the desired signal region so that the signal is not cancelled when it is present. Optionally, the response can also be fixed in other regions of interest by adding more constraints. This design procedure clearly demonstrates that the key to designing efficient constraints lies in finding the weighting coefficients which specify the desired quiescent response - a problem identical to the synthesis of desired beam patterns for nonadaptive arrays. Using two recently developed algorithms to synthesize desired quiescent responses, the effectiveness of this new design procedure is illustrated by examples in both narrow-band and broadband arrays.

The concept of quasi-phase matched second harmonic generation is analyzed in the space and wave vector mmismatch domains. Factors leading to deviations from the ideal state are investigated to compute the tuning characteristics and acceptance bandwidths of a nonlinear device material. These include periodicity, wavelength, angle of propagation and temperature. A design methodology for obtaining structures with the required tuning wave curves is also presented.

A study proposes a semivectorial beam propagation technique for investigating rib or channel waveguides in the polarized mode. It uses the finite-difference method and alternating-direction implicit method for propagating the optical beam while retaining other traditional beam propagation techniques for obtaining the mode index. The new technique was used to analyse form birefringence in longitudinally varying devices.

A beam propagation technique based on the azimuthal effective index method is proposed for fields that may be represented by the circular-cylindrical coordinate system. The two-dimensional method improves on previous beam propagation processes because it requires adherence to a quasi-cylindrical symmetry only for the propagating field and not for the waveguide structure. Although its applications are limited, it may be implemented for several situations like fiber-slab combinations and nonsynchronous fiber-fiber couplers.

A method of controlling the spot-size of a focused microwave Gaussian-beam using an active aperture-blockage is described. The Gaussian-beam launcher consists of an open-ended scalar-horn with a dielectric hyperhemisphere at its aperture. Also included is an AgI-pellet at the aperture-center with a provision to heat it with an external de source. The scalar-horn plus the dielectric lens launch a Gaussian-beam; and, the AgI pellet when heated, becomes a superionic conductor offering an aperture-blockage. This results in a variation of the spotsize of the emergent-beam. Theoretical results and experimental data are furnished and compared.

An analog neural network approach for the implementation of the MVDR beamformer is presented and an analog circuit is described. It was pointed out, however, that an array operating in a nonstationary environment requires a programmable conductance matrix for the neural network. The programmable capacitor array can be used to realize the time-varying synaptic weight matrix on a real-time basis. Moreover, it was shown that the conductance representing negative covariance matrix element is connected to the negative output terminal of the variable amplifier.