Showing papers on "Phased array published in 2006"

On Probing Signal Design for MIMO Radar

Abstract: A multiple-input multiple-output (MIMO) radar system, unlike a standard phased-array radar, can choose freely the probing signals transmitted via its antennas to maximize the power around the locations of the targets of interest, or more generally to approximate a given transmit beampattern, and also to minimize the cross-correlation of the signals reflected back to the radar by the targets of interest. In this paper, we show how the above desirable features can be achieved by designing the covariance matrix of the probing signal vector transmitted by the radar. Moreover, in a numerical study, we show that the proper choice of the probing signals can significantly improve the performance of adaptive MIMO radar techniques. Additionally, we demonstrate the advantages of several MIMO transmit beampattern designs, including a beampattern matching design and a minimum sidelobe beampattern design, over their phased-array counterparts.

Frequency diverse array radars

Abstract: This paper presents a generalized structure for a frequency diverse array radar. In its simplest form, the frequency diverse array applies a linear phase progression across the aperture. This linear phase progression induces an electronic beam scan, as in a conventional phased array. When an additional linear frequency shift is applied across the elements, a new term is generated which results in a scan angle that varies with range in the far-field. This provides more flexible beam scan options, as well as providing resistance to point interference such as multipath. More general implementations provide greater degrees of freedom for space-time-frequency-phase-polarization control, permitting novel concepts for simultaneous multi-mission operation, such as performing synthetic aperture radar and ground moving target indication at the same time.

A 77-GHz Phased-Array Transceiver With On-Chip Antennas in Silicon: Receiver and Antennas

Abstract: In this paper, we present the receiver and the on-chip antenna sections of a fully integrated 77-GHz four-element phased-array transceiver with on-chip antennas in silicon. The receiver section of the chip includes the complete down-conversion path comprising low-noise amplifier (LNA), frequency synthesizer, phase rotators, combining amplifiers, and on-chip dipole antennas. The signal combining is performed using a novel distributed active combining amplifier at an IF of 26 GHz. In the LO path, the output of the 52-GHz VCO is routed to different elements and can be phase shifted locally by the phase rotators. A silicon lens on the backside is used to reduce the loss due to the surface-wave power of the silicon substrate. Our measurements show a single-element LNA gain of 23 dB and a noise figure of 6.0dB. Each of the four receive paths has a gain of 37 dB and a noise figure of 8.0 dB. Each on-chip antenna has a gain of +2 dBi

32-channel 3 Tesla receive-only phased-array head coil with soccer-ball element geometry.

Abstract: A 32-channel 3T receive-only phased-array head coil was developed for human brain imaging. The helmet-shaped array was designed to closely fit the head with individual overlapping circular elements arranged in patterns of hexagonal and pentagonal symmetry similar to that of a soccer ball. The signal-to-noise ratio (SNR) and noise amplification (g-factor) in accelerated imaging applications were quantitatively evaluated in phantom and human images and compared with commercially available head coils. The 32-channel coil showed SNR gains of up to 3.5-fold in the cortex and 1.4-fold in the corpus callosum compared to a (larger) commercial eight-channel head coil. The experimentally measured g-factor performance of the helmet array showed significant improvement compared to the eight-channel array (peak g-factor 59% and 26% of the eight-channel values for four- and fivefold acceleration). The performance of the arrays is demonstrated in high-resolution and highly accelerated brain images.

Phased Array Antennas : Floquet Analysis, Synthesis, BFNs and Active Array Systems

Abstract: Preface. 1 Phased Array Fundamentals: Pattern Analysis and Synthesis. 1.1 Introduction. 1.2 Array Fundamentals. 1.3 Pencil Beam Array. 1.4 Linear Array Synthesis. 1.5 Planar Aperture Synthesis. 1.6 Discretization of Continuous Sources. 1.7 Summary. References. Bibliography. Problems. 2 Introduction to Floquet Modes in Infinite Arrays. 2.1 Introduction. 2.2 Fourier Spectrum and Floquet Series. 2.3 Floquet Excitations and Floquet Modes. 2.4 Two-Dimensional Floquet Excitation. 2.5 Grating Beams from Geometrical Optics. 2.6 Floquet Mode and Guided Mode. 2.7 Summary. References. Problems. 3 Floquet Modal Functions. 3.1 Introduction. 3.2 TEz and TMz Floquet Vector Modal Functions. 3.3 Infinite Array of Electric Surface Current on Dielectric-Coated Ground Plane. 3.4 Determination of Blind Angles. 3.5 Active Element Pattern. 3.6 Array of Rectangular Horn Apertures. References. Bibliography. Problems. 4 Finite Array Analysis Using Infinite Array Results: Mutual Coupling Formulation. 4.1 Introduction. 4.2 Symmetry Property of Floquet Impedance. 4.3 Mutual Coupling. 4.4 Array of Multimodal Sources. 4.5 Mutual Coupling in Two-Dimensional Arrays. 4.6 Active Input Impedance of Finite Array. 4.7 Active Return Loss of Open-Ended Waveguide Array. 4.8 Radiation Patterns of Finite Array. 4.9 Radiation Patterns of Open-Ended Waveguide Array. 4.10 Array with Nonuniform Spacing. 4.11 Finite Array Analysis Using Convolution. References. Bibliography. Problems. 5 Array of Subarrays. 5.1 Introduction. 5.2 Subarray Analysis. 5.3 Subarray with Arbitrary Number of Elements. 5.4 Subarrays with Arbitrary Grids. 5.5 Subarray and Grating Lobes. 5.6 Active Subarray Patterns. 5.7 Four-Element Subarray Fed by Power Divider. 5.8 Subarray Blindness. 5.9 Concluding Remarks. References. Bibliography. Problems. 6 GSM Approach for Multilayer Array Structures. 6.1 Introduction. 6.2 GSM Approach. 6.3 GSM Cascading Rule. 6.4 Transmission Matrix Representation. 6.5 Building Blocks for GSM Analysis. 6.6 Equivalent Impedance Matrix of Patch Layer. 6.7 Stationary Character of MoM Solutions. 6.8 Convergence of MoM Solutions. 6.9 Advantages of GSM Approach. 6.10 Other Numerical Methods. References. Bibliography. Problems. 7 Analysis of Microstrip Patch Arrays. 7.1 Introduction. 7.2 Probe-Fed Patch Array. 7.3 EMC Patch Array. 7.4 Slot-Fed Patch Array. 7.5 Stripline-Fed Slot-Coupled Array. 7.6 Finite Patch Array. References. Bibliography. Problems. 8 Array of Waveguide Horns. 8.1 Introduction. 8.2 Linearly Flared Horn Array. 8.3 Grazing Lobes and Pattern Nulls. 8.4 Surface and Leaky Waves in an Array. 8.4.1 Surface Wave. 8.5 Wide-Angle Impedance Matching. 8.6 Multimodal Rectangular/Square Horn Elements. 8.7 Multimodal Circular Horn Elements. References. Bibliography. Problems. 9 Frequency-Selective Surface, Polarizer, and Reflect-Array Analysis. 9.1 Introduction. 9.2 Frequency-Selective Surface. 9.3 Screen Polarizer. 9.4 Printed Reflect Array. References. Bibliography. Problems. 10 Multilayer Array Analysis with Different Periodicities and Cell Orientations. 10.1 Introduction. 10.2 Layers with Different Periodicities: Rectangular Lattice. 10.3 Nonparallel Cell Orientations: Rectangular Lattice. 10.4 Layers with Arbitrary Lattice Structures. 10.5 Summary. References. Bibliography. Problems. 11 Shaped-Beam Array Design: Optimization Algorithms. 11.1 Introduction. 11.2 Array Size: Linear Array. 11.3 Element Size. 11.4 Pattern Synthesis Using Superposition (Woodward's Method). 11.5 Gradient Search Algorithm. 11.6 Conjugate Match Algorithm. 11.7 Successive Projection Algorithm. 11.8 Other Optimization Algorithms. 11.9 Design Guidelines of a Shaped Beam Array. References. Bibliography. Problems. 12 Beam Forming Networks in Multiple-Beam Arrays. 12.1 Introduction. 12.2 BFN Using Power Dividers. 12.3 Butler Matrix Beam Former. 12.4 Blass Matrix BFN. 12.5 Rotman Lens. 12.6 Digital Beam Former. 12.7 Optical Beam Formers. References. Bibliography. Problems. 13 Active Phased Array Antenna. 13.1 Introduction. 13.2 Active Array Block Diagrams. 13.3 Aperture Design of Array. 13.4 Solid State Power Amplifier. 13.5 Phase Shifter. 13.6 Intermodulation Product. 13.7 Noise Temperature and Noise Figure of Antenna Subsystems. 13.8 Active Array System Analysis. 13.9 Active Array Calibration. 13.10 Concluding Remarks. References. Bibliography. Problems. 14 Statistical Analysis of Phased Array Antenna. 14.1 Introduction. 14.2 Array Pattern. 14.3 Statistics of R and I. 14.4 Probability Density Function. 14.5 Confidence Limits. 14.6 Element Failure Analysis. 14.7 Concluding Remarks. References. Bibliography. Problems. Appendix. Index.

A 77-GHz Phased-Array Transceiver With On-Chip Antennas in Silicon: Transmitter and Local LO-Path Phase Shifting

Abstract: Integration of mm-wave multiple-antenna systems on silicon-based processes enables complex, low-cost systems for high-frequency communication and sensing applications. In this paper, the transmitter and LO-path phase-shifting sections of the first fully integrated 77-GHz phased-array transceiver are presented. The SiGe transceiver utilizes a local LO-path phase-shifting architecture to achieve beam steering and includes four transmit and receive elements, along with the LO frequency generation and distribution circuitry. The local LO-path phase-shifting scheme enables a robust distribution network that scales well with increasing frequency and/or number of elements while providing high-resolution phase shifts. Each element of the heterodyne transmitter generates +12.5 dBm of output power at 77 GHz with a bandwidth of 2.5 GHz leading to a 4-element effective isotropic radiated power (EIRP) of 24.5 dBm. Each on-chip PA has a maximum saturated power of +17.5 dBm at 77 GHz. The phased-array performance is measured using an internal test option and achieves 12-dB peak-to-null ratio with two transmit and receive elements active

A wireless communication device using adaptive beamforming

Abstract: A method and apparatus is disclosed herein for wireless communication with adaptive beamforming. In one embodiment, the apparatus comprises a processor, a radio frequency (RF) transmitter having a digitally controlled phased array antenna coupled to and controlled by the processor to transmit content using adaptive beamforming, and an interface to a wireless communication channel coupled to the processor to communicate antenna information relating to the use of the phased array antenna and to communicate information to facilitate playing the content at another location.

High Resolution Capabilities of MIMO Radar

Abstract: Multiple-input multiple-output (MIMO) radar is a multistatic architecture composed of multiple transmitters and receivers, which seeks to exploit the spatial diversity of radar backscatter. In conjunction with centralized processing, MIMO radar has the potential to significantly improve radar functions such as detection and parameter estimation. MIMO radar is distinct from other types of array radars such as phased array or STAP, which process the signals of closely spaced elements and, hence, cannot capitalize on the spatial characteristics of targets. In this work, we explore the ability of MIMO radar and coherent processing to locate a target with high resolution and to resolve targets located in the same range cell. A distributed target model is developed. It is demonstrated that MIMO radar with centralized coherent processing is able to resolve scatterers with a range resolution well beyond that supported by the signal bandwidth. The location estimation capabilities are further illustrated by introducing a new two-dimensional ambiguity function. The analysis is discussed in the context of established results for randomly thinned arrays. The investigation of high resolution MIMO radar also includes comparison with the performance of non-coherent MIMO radar and the effect on performance of the number of sensors and their locations.

Phased array systems and phased array front-end devices

Abstract: Disclosed herein is a front-end device for a phased array system. The front-end device includes an array of horn antennas, a first set of transmission lines coupled to the horn antenna array for a first polarization, a second set of transmission lines coupled to the horn antenna array for a second polarization orthogonal to the first polarization, and a plurality of L-shaped excitation elements. Each L-shaped excitation element of the plurality of L-shaped excitation elements couples a transmission line from each of the first and second sets of transmission lines to a respective horn antenna of the horn antenna array.

True time delay phase array radar using rotary clocks and electronic delay lines

Abstract: Local oscillator circuitry for an antenna array is disclosed The circuitry includes an array of rotary traveling wave oscillators which are arranged in a pattern over an area and coupled so as to make them coherent This provides for a set of phase synchronous local oscillators distributed over a large area The array also includes a plurality of phase shifters each of which is connected to one of the rotary oscillators to provide a phase shifted local oscillator for the array The phase shifter optionally includes a cycle counter that is configured to count cycles of the rotary oscillator to which it is connected and control circuitry that is then operative to provide a shifted rotary oscillator output based on the count from the cycle counter A system and method for operating a true-time delay phased array antenna system The system includes a plurality of antenna element circuits for driving or receiving an rf signal from the elements of the array Each element circuit has a transmit and a receive path and a local multiphase oscillator, such as a rotary traveling wave oscillator Each path has an analog delay line for providing a true-time delay for the antenna element Preferably, the analog delay line is a charge coupled device whose control nodes are connected to phases of the local multiphase oscillator to implement a delay that is an integer number local multiphase oscillator periods A fractional delay is also included in the path by using a sample and hold circuit connected to a particular phase of the oscillator By delaying each antenna element by a true time delay, broadband operation of the array is possible

Bistatic SAR Processing and Experiments

Abstract: Bistatic synthetic aperture radar (SAR) uses a separated transmitter and receiver flying on different platforms to achieve benefits like exploitation of additional information contained in the bistatic reflectivity of targets, reduced vulnerability for military applications, forward-looking SAR imaging, or increased radar cross section. Besides technical problems such as synchronization of the oscillators, involved adjustment of transmit pulse versus receive gate timing, antenna pointing, flight coordination, and motion compensation, the development of a bistatic focusing algorithm is still in progress and not sufficiently solved. As a step to a numerically efficient processor, this paper presents a bistatic range migration algorithm for the translationally invariant case, where transmitter and receiver have equal velocity vectors. In this paper, the algorithm was successfully applied to simulated and real bistatic data. The real bistatic data have been acquired with the Forschungsgesellschaft fur Angewandte Naturwissenschaften (FGAN)'s X-band SAR systems, namely the Airborne Experimental Radar II and the Phased Array Multifunctional Imaging Radar, in October 2003

Automated Antenna Design with Evolutionary Algorithms

Abstract: Current methods of designing and optimizing antennas by hand are time and labor intensive, and limit complexity. Evolutionary design techniques can overcome these limitations by searching the design space and automatically finding effective solutions. In recent years, evolutionary algorithms have shown great promise in finding practical solutions in large, poorly understood design spaces. In particular, spacecraft antenna design has proven tractable to evolutionary design techniques. Researchers have been investigating evolutionary antenna design and optimization since the early 1990s, and the field has grown in recent years as computer speed has increased and electromagnetic simulators have improved. Two requirements-compliant antennas, one for ST5 and another for TDRS-C, have been automatically designed by evolutionary algorithms. The ST5 antenna is slated to fly this year, and a TDRS-C phased array element has been fabricated and tested. Such automated evolutionary design is enabled by medium-to-high quality simulators and fast modern computers to evaluate computer-generated designs. Evolutionary algorithms automate cut-and-try engineering, substituting automated search though millions of potential designs for intelligent search by engineers through a much smaller number of designs. For evolutionary design, the engineer chooses the evolutionary technique, parameters and the basic form of the antenna, e.g., single wire for ST5 and crossed-element Yagi for TDRS-C. Evolutionary algorithms then search for optimal configurations in the space defined by the engineer. NASA's Space Technology 5 (ST5) mission will launch three small spacecraft to test innovative concepts and technologies. Advanced evolutionary algorithms were used to automatically design antennas for ST5. The combination of wide beamwidth for a circularly-polarized wave and wide impedance bandwidth made for a challenging antenna design problem. From past experience in designing wire antennas, we chose to constrain the evolutionary design to a monopole wire antenna. The results of the runs produced requirements-compliant antennas that were subsequently fabricated and tested. The evolved antenna has a number of advantages with regard to power consumption, fabrication time and complexity, and performance. Lower power requirements result from achieving high gain across a wider range of elevation angles, thus allowing a broader range of angles over which maximum data throughput can be achieved. Since the evolved antenna does not require a phasing circuit, less design and fabrication work is required. In terms of overall work, the evolved antenna required approximately three person-months to design and fabricate whereas the conventional antenna required about five. Furthermore, when the mission was modified and new orbital parameters selected, a redesign of the antenna to new requirements was required. The evolutionary system was rapidly modified and a new antenna evolved in a few weeks. The evolved antenna was shown to be compliant to the ST5 mission requirements. It has an unusual organic looking structure, one that expert antenna designers would not likely produce. This antenna has been tested, baselined and is scheduled to fly this year. In addition to the ST5 antenna, our laboratory has evolved an S-band phased array antenna element design that meets the requirements for NASA's TDRS-C communications satellite scheduled for launch early next decade. A combination of fairly broad bandwidth, high efficiency and circular polarization at high gain made for another challenging design problem. We chose to constrain the evolutionary design to a crossed-element Yagi antenna. The specification called for two types of elements, one for receive only and one for transmit/receive. We were able to evolve a single element design that meets both specifications thereby simplifying the antenna and reducing testing and integration costs. The highest performance antenna found using a getic algorithm and stochastic hill-climbing has been fabricated and tested. Laboratory results correspond well with simulation. Aerospace component design is an expensive and important step in space development. Evolutionary design can make a significant contribution wherever sufficiently fast, accurate and capable software simulators are available. We have demonstrated successful real-world design in the spacecraft antenna domain; and there is good reason to believe that these results could be replicated in other design spaces.

Antenna calibration method and system

Abstract: A phased array antenna system includes an RF front end, a radome, and an optical calibrator embedded in the radome for enabling in-situ calibration of the RF front end The optical calibrator employs an optical timing signal generator (OTSG), a Variable Optical Amplitude and Delay Generator array (VOADGA) for receiving the modulated optical output signal and generating a plurality of VOADGA timing signals, and an optical timing signal distributor (OTSD) The in-situ optical calibrator allows for reduced calibration time and makes it feasible to perform calibration whenever necessary

Lightweight space-fed active phased array antenna system

Abstract: A system for a satellite includes a core system and multiple nodes for generating an active phased array. Each node includes a transceiver for wirelessly receiving a transmit signal from the core system, for wirelessly transmitting the transmit signals to a target, for wirelessly receiving the receive signals from the target, and for wirelessly transmitting the receive signal back to the core system. The system also includes a subsystem for inhibiting signal interference between the transmit and receive signals. Each of the nodes may also include local power generation circuitry.

A mm-WAVE FULLY INTEGRATED PHASED ARRAY RECEIVER AND TRANSMITTER WITH ON CHIP ANTENNAS

Abstract: A phased array mm-wave device includes a substrate, a mm-wave transmitter integrated onto the substrate configured to transmit a mm-wave signal and/or a mm-wave receiver integrated onto the substrate and configured to receive a mm-wave signal. The mm-wave device also includes a phased array antenna system integrated onto the substrate and including two or more antenna elements. The phased array mm-wave device also includes one or more dielectric lenses. A distributed mm-wave distributed combining tree circuit includes at least two pairs of differential tranconductors with regenerative degeneration and accepts at least two differential input signals. Two mm-wave loopback methods measure the phased array antenna patterns and the performance of an integrated receiver transmitter system.

Combining MIMO Radar with OFDM Communications

Abstract: MIMO radar systems have been proposed elsewhere which utilise OFDM waveforms as the scene illuminator. This suggests an opportunity exists to code the OFDM radar waveform in such a way as to provide a communication link to broadcast the radar data to remote users. The benefit of this would arise from the dual use of the microwave band, addressing the problem where demand for bandwidth is exceeding capacity. This paper explores the technical issues associated with this idea and outlines some of the key features of such a system. We describe how OFDM waveforms can be applied to MIMO radar; and what constraints must be placed on the waveform to ensure robust operation for both radar and communication functions. A candidate system design is presented, along with basic analysis of the expected performance of both radar and communications functionality.

Ultrawide-band properties of long slot arrays

Abstract: In this paper the ultrawide-band properties of a long slot array are described. The study provides the rigorously derived Green's function (GF) for an infinite long slot array. From these GF active impedances and radiation patterns for various cases were obtained. The ultrawide bandwidths and the array performances of such apertures are highlighted, providing physical insights to understand the mathematical formulation throughout the paper.

Extension of DAMAS Phased Array Processing for Spatial Coherence Determination (DAMAS-C)

Abstract: The present study reports a new development of the DAMAS microphone phased array processing methodology that allows the determination and separation of coherent and incoherent noise source distributions. In 2004, a Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) was developed which decoupled the array design and processing influence from the noise being measured, using a simple and robust algorithm. In 2005, three-dimensional applications of DAMAS were examined. DAMAS has been shown to render an unambiguous quantitative determination of acoustic source position and strength. However, an underlying premise of DAMAS, as well as that of classical array beamforming methodology, is that the noise regions under study are distributions of statistically independent sources. The present development, called DAMAS-C, extends the basic approach to include coherence definition between noise sources. The solutions incorporate cross-beamforming array measurements over the survey region. While the resulting inverse problem can be large and the iteration solution computationally demanding, it solves problems no other technique can approach. DAMAS-C is validated using noise source simulations and is applied to airframe flap noise test results.

A broadband slotted ridge waveguide antenna array

Abstract: A longitudinally-slotted ridge waveguide antenna array with a compact transverse dimension is presented. To broaden the bandwidth of the array, it is separated into two subarrays fed by a novel compact convex waveguide divider. A 16-element uniform linear array at X-band was fabricated and measured to verify the validity of the design. The measured bandwidth of S11les-15 dB is 14.9% and the measured cross- polarization level is less than -36 dB over the entire bandwidth. This array can be combined with the edge-slotted waveguide array to build a two-dimensional dual-polarization antenna array for the synthetic aperture radar (SAR) application

Demonstration of a continuously variable true-time delay beamformer using a multichannel chirped fiber grating

Abstract: A continuously variable true-time delay beamformer based on a multichannel chirped fiber grating (MCFG) is demonstrated. The beamformer is capable of wide-band squint-free operation and demonstrates beam steering of a four-element array over /spl plusmn/40/spl deg/. The use of an MCFG provides a significant reduction in the length of the chirped grating required, eliminates spurious signal transmission, and utilizes narrow-band tunable laser sources. In addition, the effect of grating errors on the antenna pattern is examined and the tolerance on performance is presented.

High frame rate imaging system for limited diffraction array beam imaging with square-wave aperture weightings high frame rate imaging system for limited diffraction array beam imaging with square-wave aperture weightings

Abstract: A general-purpose high frame rate (HFR) medical imaging system has been developed. This system has 128 independent linear transmitters, each of which is capable of producing an arbitrary broadband (about 0.05-10 MHz) waveform of up to plusmn144 V peak voltage on a 75-ohm resistive load using a 12-bit/40-MHz digital-to-analog converter. The system also has 128 independent, broadband (about 0.25-10 MHz), and time-variable-gain receiver channels, each of which has a 12-bit/40-MHz analog-to-digital converter and up to 512 MB of memory. The system is controlled by a personal computer (PC), and radio frequency echo data of each channel are transferred to the same PC via a standard USB 2.0 port for image reconstructions. Using the HFR imaging system, we have developed a new limited-diffraction array beam imaging method with square-wave aperture voltage weightings. With this method, in principle, only one or two transmitters are required to excite a fully populated two-dimensional (2-D) array transducer to achieve an equivalent dynamic focusing in both transmission and reception to reconstruct a high-quality three-dimensional image without the need of the time delays of traditional beam focusing arid steering, potentially simplifying the transmitter subsystem of an imager. To validate the method, for simplicity, 2-D imaging experiments were performed using the system. In the in vitro experiment, a custom-made, 128-element, 0.32-mm pitch, 3.5-MHz center frequency linear array transducer with about 50% fractional bandwidth was used to reconstruct images of an ATS 539 tissue-mimicking phantom at an axial distance of 130 mm with a field of view of more than 90deg. In the in vivo experiment of a human heart, images with a field of view of more than 90deg at 120-mm axial distance were obtained with a 128-element, 2.5-MHz center frequency, 0.15-mm pitch Acusori V2 phased array. To ensure that the system was operated under the limits set by the U.S. Food and Drug Administration, the mechanical index, thermal index, and acoustic output were measured. Results show that higher-quality images can be reconstructed with the square-wave aperture weighting method due to an increased penetration depth as compared to the exact weighting method developed previously, and a frame rate of 486 per second was achieved at a pulse repetition frequency of about 5348 Hz for the human heart

Demonstration of advanced reconnaissance techniques with the airborne SAR/GMTI sensor PAMIR

Abstract: PAMIR (Phased Array Multifunctional Imaging Radar) is an experimental airborne radar system that has been designed and built by the Research Institute for High Frequency Physics and Radar Techniques (FHR) of Forschungsgesellschaft fur Angewandte Naturwissenschaften (FGAN). The goal is to meet the growing demands for future reconnaissance systems with respect to flexibility and multi-mode operation by the use of an electronically steerable phased array antenna. The X-band system with a bandwidth of 1.8 GHz serves as a platform for different tasks. One of the main objectives is to demonstrate synthetic aperture radar (SAR) imaging at a very high resolution and for a long range. The fine resolution will also be applied for inverse SAR (ISAR) imaging of ground moving targets. Moreover, five parallel receiving channels allow array processing techniques like ground moving target indication (GMTI) via space–time adaptive processing, electronic counter-counter-measures and interferometric SAR with a very high 3D-resolution. A multi-channel scan-MTI mode with a range resolution adapted to the target size allows for a wide area GMTI operation that can be complemented by target tracking. Together with the predecessor system AER-II, operating at a frequency band contained in that of PAMIR, the possibility of experimental investigation of bistatic SAR is given. SAR images of large urban areas and ISAR images of moving objects, both with finest resolution down to the sub-decimetre scale, are presented. Results of GMTI in a wide area scanning mode and broadband bistatic experiments including true bistatic SAR processing are shown as well.

History of acoustic beamforming

Abstract: The development of the beamforming method (also called microphone antenna, phased array of microphones, acoustic telescope, or acoustic camera) is reviewed in this paper. The microphone antenna was invented by Billingsley (1974) and has since seen dramatic improvements due to the availability of better data acquisition and computing hardware. Recent mathematical and software developments invert the beamforming process and allow a quantitative determination of the sources. Beamforming is indispensable for the localization of sound sources on moving objects, on flying aircraft, on high-speed trains, on motor cars in motion, on open rotors like helicopter and wind turbine rotors. In these applications, the ability to follow the motion of the sources is important. The second important applications are source localization tests in the test sections of open and closed wind tunnels. The background noise suppression capability of the beamforming method is required here. The various applications are discussed with a long list of references. 1 Berlin Beamforming Conference

Optically beamformed beam-switched adaptive antennas for fixed and mobile broad-band wireless access networks

Abstract: In this paper, a 3-bit optical beamforming architecture based in 2/spl times/2 optical switches and dispersive media is proposed and demonstrated. The performance of this photonic beamformer is experimentally demonstrated at 42.7 GHz in both transmission and reception modes. The progress achieved for realizing these architectures with integrated optics is also reported. Due to its advanced features (i.e., potential fast-switching, huge bandwidth, and immunity to electromagnetic interference), the architecture is a very promising alternative to traditional beamforming technologies for implementing beamformed base-station antennas in fixed and mobile broad-band wireless access networks operating in the millimeter-wave band. The study presented here has been carried out in the frame of the IST 2000-25390 OBANET project.

A full-duplex dual-frequency self-steering array using phase detection and phase shifting

Abstract: A full-duplex dual-frequency self-steering array using phase detection and phase shifting is presented. By RF decoupling the transmitter and receiver arrays, the proposed system promises greater system efficiency by ensuring a constant transmit power. This also allows for a separate low-frequency interrogating signal capable of various modulation schemes. A two-element prototype is demonstrated with interrogating and retrodirective frequencies of 1.425 and 2.85 GHz, respectively. Retrodirectivity is reported for angles of 0deg, -15deg, and +25deg. The power of the received signal is improved by up to 12 dB for -60deglesthetasles60deg when compared to a conventional two-element array

An innovative computational approach based on a particle swarm strategy for adaptive phased-arrays control

Abstract: In this paper a new approach to the control of phased arrays is presented and assessed. Starting from the adaptive array theory, a particle swarm strategy is used to tune the phase coefficients of the array in order to adaptively minimize/avoid the effects of interfering signals at the receiver. To show the effectiveness of the proposed approach, a selected set of numerical examples, concerned with linear as well as planar arrays, is presented. Furthermore, to evaluate the advantages of the particle swarm optimizer (PSO)-based strategy over state-of-art methods, a comparative study is carried out by analyzing the performance of the method in terms of both the signal-to-interference-plus-noise-ratio and resulting beam pattern. The achieved results, even though preliminary, seem to confirm that the PSO-based approach satisfactorily works and it generally outperforms previously proposed/state-of-art phase-only adaptive control strategies

Compact light weight UHF arrays using long slot apertures

Abstract: A wideband low profile phased array using long slot aperture was recently developed for radar and EW applications. A prototype UHF array with 4 x 8 (32) elements (1.12 m × 2.24 m × 23 cm) was built and tested for 150–600 MHz operation. Array patterns, gain, and cross-pol level were measured. Excellent performance was observed. The array is 23 cm thick, and it weighs 7 kg (2.8 kg/m 2 ). Lossy loading material may be used to make it thinner, but this is believed to be the lightest and thinnest UHF array reported for wideband applications without gain penalty.

An Integrated Subharmonic Coupled-Oscillator Scheme for a 60-GHz Phased-Array Transmitter

Abstract: This paper describes the design of an integrated coupled-oscillator array in SiGe for millimeter-wave applications. The design focuses on a scalable radio architecture where multiple dies are tiled to form larger arrays. A 2 times 2 oscillator array for a 60-GHz transmitter is fabricated with integrated power amplifiers and on-chip antennas. To lock between multiple dies, an injection-locking scheme appropriate for wire-bond interconnects is described. The 2 times 2 array demonstrates a 200 -MHz locking range and 1 times 4 array formed by two adjacent chips has a 60-MHz locking range. The phase noise of the coupled oscillators is below -100 dBc/Hz at a 1-MHz offset when locked to an external reference. To the best of the authors' knowledge, this is the highest frequency demonstration of coupled oscillators fabricated in a conventional silicon integrated-circuit process

An RF phased array applicator designed for hyperthermia breast cancer treatments.

Abstract: An RF phased array applicator has been constructed for hyperthermia treatments in the intact breast This RF phased array consists of four antennas mounted on a Lexan water tank, and geometric focusing is employed so that each antenna points in the direction of the intended target The operating frequency for this phased array is 140 MHz The RF array has been characterized both by electric field measurements in a water tank and by electric field simulations using the finite-element method The finite-element simulations are performed with HFSS software, where the mesh defined for finite-element calculations includes the geometry of the tank enclosure and four end-loaded dipole antennas The material properties of the water tank enclosure and the antennas are also included in each simulation The results of the finite-element simulations are compared to the measured values for this configuration, and the results, which include the effects of amplitude shading and phase shifting, show that the electric field predicted by finite-element simulations is similar to the measured field Simulations also show that the contributions from standing waves are significant, which is consistent with measurement results Simulated electric field and bio-heat transfer results are also computed within a simple 3D breast model Temperature simulations show that, although peak temperatures are generated outside the simulated tumour target, this RF phased array applicator is an effective device for regional hyperthermia in the intact breast