Showing papers on "Phased array published in 2001"

Handbook of Antennas in Wireless Communications

Abstract: From the Publisher: The move toward worldwide wireless communications continues at a remarkable pace, and the antenna element of the technology is crucial to its success. With contributions from more than 30 international experts, the Handbook of Antennas in Wireless Communications brings together all of the latest research and results to provide engineering professionals and students with a one-stop reference on the theory, technologies, and applications for indoor, hand-held, mobile, and satellite systems.Beginning with an introduction to wireless communications systems, it offers an in-depth treatment of propagation prediction and fading channels. It then explores antenna technology with discussion of antenna design methods and the various antennas in current use or development for base stations, hand held devices, satellite communications, and shaping beams. The discussions then move to smart antennas and phased array technology, including details on array theory and beamforming techniques. Space diversity, direction-of-arrival estimation, source tracking, and blind source separation methods are addressed, as are the implementation of smart antennas and the results of field trials of systems using smart antennas implemented. Finally, the hot media topic of the safety of mobile phones receives due attention, including details of how the human body interacts with the electromagnetic fields of these devices.Its logical development and extensive range of diagrams, figures, and photographs make this handbook easy to follow and provide a clear understanding of design techniques and the performance of finished products. Its unique, comprehensive coverage written by top experts in their fields promises tomake the Handbook of Antennas in Wireless Communications the standard reference for the field.

Systems and methods for reducing secondary hot spots in a phased array focused ultrasound system

Abstract: Systems and methods for performing a therapeutic procedure using focused ultrasound include providing a piezoelectric transducer including a plurality of transducer elements (22), such as a concave concentric ring array or a linear array of transducer elements. Drive circuitry (14) is coupled to the transducer for providing drive signals to the transducer elements at one of a plurality of discrete RF frequencies. A controller (16) is coupled to the drive circuitry for periodically changing a frequency of the drive signals to one of the plurality of discrete frequencies, while controlling a phase component of the drive signals to maintain the focus of the transducer at a primary focal zone during a single sonication.

Implementing guided wave mode control by use of a phased transducer array

Abstract: A multichannel time-delay system has been built and applied to a transducer array for implementing guided wave mode control. The time-delay system has a capability of sending high energy controllable tone-burst signals from eight independent channels with arbitrary time delays from 0 to 30 /spl mu/s with resolution of 0.025 /spl mu/s. Software time delays are also provided for summing up received signals of each channel. Theoretical discussions indicate the impact of the time delay capability on the bandwidth and sensitivity improvement of a transducer array for guided wave generation. Determination of both physical and software time delay values is based on a knowledge of dispersion curves and element spacing. Based on reference signals, a non-knowledge-based automatic time-delay searching algorithm was introduced for guided wave mode selection. Experiments were conducted with a phased comb transducer array mounted on a carbon steel pipe. The experimental results show that signal to noise ratio has been greatly improved by use of the time-delay system. Some other benefits of the phased array, including unidirection generation and mode control flexibility, are discussed.

Phased array antenna providing enhanced element controller data communication and related methods

Abstract: A phased array antenna may include a substrate and a plurality of phased array antenna elements carried by the substrate, and a plurality of element controllers connected to the phased array antenna elements. Each element controller may be switchable between inactive and active data receiving states. The phased array antenna may further include a plurality of subarray controllers and a plurality of data buses. Each data bus may connect a respective subarray controller to respective columns and rows of element controllers. Further, each subarray controller may cooperate with a respective data bus for sending data in parallel to a plurality of rows of element controllers and while sequentially switching a given column of element controllers from the inactive data receiving state to the active data receiving state

Parametric audio system

Abstract: A parametric audio system having increased bandwidth for generating airborne audio signals with reduced distortion. The parametric audio system includes a modulator (112) for modulating an ultrasonic carrier signal with a processed audio signal, a driver amplifier (118) for amplifying the modulated carrier signal, and an array of acoustic transducers (122) for projecting the modulated and amplified carrier signal through the air along a selected projection path to regenerate the audio signal. Each of the acoustic transducers in the array (122) is a membrane-type transducer (Fig. 2a and 2b). Further, the acoustic transducer array (122) is a phased array capable of electronically steering, focusing, or shaping one or more audio beams.

Ghost artifact cancellation using phased array processing

Abstract: A ghost artifact cancellation technique is disclosed. Phased array combining is used to cancel ghosts caused by a variety of distortion mechanisms, including space-variant distortions, such as local flow or off-resonance. The technique uses a constrained optimization that optimizes signal-to-noise ratio (SNR) subject to the constraint of nulling ghost artifacts at known locations. In one aspect multi-coil, k-space data is passed through a converter to convert the k-space data to image domain. After the conversion, the images contain ghost artifacts. The images are then passed through one or more phased array combiners. Each phased array combiner separates the superimposed ghosts to produce an image without ghosts. These images may then be aligned by means of shifting and combined by a variety of means to improve the final image quality. In another aspect, the phase encode order is varied in time to produce ghosts with time varying phase. The series of images are then used to adaptively compute the phased array combiner and output combiner coefficients. The developed technique may be used with phase encode orders which reduce image distortion.

Antenna integrated ceramic chip carrier for a phased array antenna

Abstract: An integrated ceramic chip carrier module for a phased array antenna. The module is comprised of a plurality of layers of low temperature, co-fired ceramic formed into an integrated module. The module combines the injection molded probes, button layer and holder, and the ceramic chip carrier into a single integrated component part. This construction provides for improved performance, reliability, manufacturing repeatability, and lower overall antenna manufacturing costs.

Subarray weighting for the difference patterns of monopulse antennas: joint optimization of subarray configurations and weights

Abstract: Given a linear antenna array with an excitation distribution affording a sum pattern, subarray weighting allows the same array also to generate a difference pattern, with minimal alteration of the signal feed circuitry. Previous implementations of this approach have optimized the weights of given subarrays. Here we report the simultaneous optimization of the partition in subarrays and the subarray weights.

Optimal focusing by spatio-temporal inverse filter. II. Experiments. Application to focusing through absorbing and reverberating media.

Abstract: To focus ultrasonic waves in an unknown heterogeneous medium using a phased array, one has to calculate the optimal set of signals to be applied on the transducers of the array. (In most applications of ultrasound, medical imaging, medical therapy, nondestructive testing, the first step consists of focusing a broadband ultrasound beam deeply inside the medium to be investigated.) Focusing in a homogeneous medium simply requires to compensate for the varying focus–array elements geometrical distances. Nevertheless, heterogeneities in the medium, in terms of speed of sound, density, or absorption, may strongly degrade the focusing. Different techniques have been developed in order to correct such aberrations induced by heterogeneous media (time reversal, speckle brightness, for example). In the companion to this paper, a new broadband focusing technique was investigated: the spatio-temporal inverse filter. Experimental results obtained in various media, such as reverberating and absorbing media, are present...

Planar strip array (PSA) for MRI.

Abstract: Parallel, spatial-encoded MRI requires a large number of independent detectors that simultaneously acquire signals. The loop structure and mutual coupling in conventional phased arrays limit the number of coils and therefore the potential reduction in minimum scan time achievable by parallel MRI tchniques. A new near-field MRI detector array, the planar strip array (PSA), is presented that eliminates the coupling problems and can be extended to a very large number of detectors and high MRI frequencies. Its basic structure is an array of parallel microstrips with a high permittivity substrate and overlay. The electromagnetic (EM) wavelength can be adjusted with the permittivity, and the strip lengths tuned to a preselected fraction of the wavelength of the MRI frequency. EM wave analysis and measurements on a prototype four-element PSA reveal that the coupling between the strips vanishes when the strip length is either an integer times a quarter wavelength for a standing-wave PSA, or a half wavelength for a travelling-wave PSA, independent of the spacing between the strips. The analysis, as well as phantom and human MRI experiments performed by conventional and parallel-encoded MRI with the PSA at 1.5 T, show that the decoupled strips produce a relatively high-quality factor and signal-to-noise ratio, provided that the strips are properly terminated, tuned, and matched or coupled to the preamplifiers.

Electromagnetic phased arrays for regional hyperthermia : optimal frequency and antenna arrangement

Abstract: This paper investigates the effects of the three-dimensional arrangement of antennae and frequency on temperature distributions that can be achieved in regional hyperthermia using an electromagnetic phased array. It compares the results of power-based and temperature-based optimization. Thus, one is able to explain the discrepancies between previous studies favouring more antenna rings on the one hand and more antennae per ring on the other hand. The sensitivity of the results is analysed with respect to changes in amplitudes and phases, as well as patient position. This analysis can be used for different purposes. First, it provides additional criteria for selecting the optimal frequency. Secondly, it can be used for specifying the required phase and amplitude accuracy for a real phased array system. Furthermore, it may serve as a basis for technological developments in order to reduce both types of sensitivities described above.

Phased array calibration

Abstract: Calibration of a phased array antenna while the antenna is in service can be a complex and time-consuming procedure that affects use of the antenna and imposes an unacceptable overhead on the system. The procedure described herein uses a maximum likelihood algorithm to minimize the number of measurements, thus reducing the impact on the system and shifting the overhead to a remote site.

Transmit/receiver module for active phased array antenna

Abstract: This invention relates to a transmit and receive module for active phased array antenna system based upon a combination of hybrid microwave integrated circuit (MIC) as well as monolithic microwave integrated circuit (MMIC) technology. The module comprises a signal transmit chain having switching means (03) for switching the module to transmittance mode. Means are provided for applying pulsed RF signal to the said module from array manifold. A phase shifter (01) is connected to a digital attenuator (02) and the output of the attenuator (02) is connected to a power amplifier (04). The amplified signals from amplifier (04) are conveyed to a duplexer means (05) connected to said power amplifier (04) and for routing back the received signal through a receiver protector (06) and low noise amplifier means (07). Electronic means are connected to a power conditioner for controlling the operation of the device.

Miniaturized conformal wideband fractal antennas on high dielectric substrates and chiral layers

Abstract: A class of antennas that comprise an electrically conductive fractal pattern disposed on a dielectric substrate and are capable of construction in a size measured in centimeters as compared to previous antennas of the same class that measured in meters. One antenna style has a ground plane that is perpendicular to the substrate and another style has a ground plane that is parallel to the substrate. The substrate has a dielectric constant of in the range of about 10 to 600 or more and may be a ferroelectric, such as barium strontium titanate. A bias voltage applied across the substrate can tune the antenna for operation in a particular frequency range. The antenna can be made especially wideband by placing an absorbing material behind the substrate. The fractal pattern may be any fractal pattern, such as Hilbert curve, Koch curve, Sierpinski gasket and Sierpinski carpet. One style of the antenna uses a fractal pattern that has a plurality of segments arranged in a first configuration and a switch disposed to alter the first configuration to one or more other configurations. The antenna elements may also be arranged in a phased array.

Broadband dual-polarized microstrip notch antenna

Abstract: A dual-polarized radiator for a phased array antenna includes two planar microstrip notch elements that interlock and are perpendicular to each other having their phase centers coincident to provide advantageous operational characteristics when the elements are used to form a wide bandwidth, wide scan angle phased array antenna.

Compensation of chromatic dispersion and dispersion slope using a virtually imaged phased array

Abstract: Chromatic dispersion produced by the virtually imaged phased array (VIPA) is discussed. A newly designed 3-dimensional mirror produces uniform dispersion for each WDM channel with a wide variable dispersion range. The VIPA with the mirror also produces dispersion slope by including a diffraction grating.

Digital phased array beamforming using single-bit delta-sigma conversion with non-uniform oversampling

Abstract: Digital beamforming based on oversampled delta-sigma (/spl Delta//spl Sigma/) analog-to-digital (A/D) conversion can reduce the overall cost, size, and power consumption of phased array front-end processing. The signal resampling involved in dynamic /spl Delta//spl Sigma/ beamforming, however, disrupts synchronization between the modulators and demodulator, causing significant degradation in the signal-to-noise ratio. As a solution to this, we have explored a new digital beamforming approach based on non-uniform oversampling /spl Delta//spl Sigma/ A/D conversion. Using this approach, the echo signals received by the transducer array are sampled at time instants determined by the beamforming timing and then digitized by single-bit /spl Delta//spl Sigma/ A/D conversion prior to the coherent beam summation. The timing information involves a nonuniform sampling scheme employing different clocks at each array channel. The /spl Delta//spl Sigma/ coded beamsums obtained by adding the delayed 1-bit coded RF echo signals are then processed through a decimation filter to produce final beamforming outputs. The performance and validity of the proposed beamforming approach are assessed by means of emulations using experimental raw RF data.

Bootstrapped, piecewise-asymptotic directivity pattern control mechanism setting weighting coefficients of phased array antenna

Abstract: Weighting coefficients for a phased array antenna are iteratively refined to optimal values by a ‘bootstrapped’ process that starts with a coarse set of weighting coefficients, to which received signals are subjected, to produce a first set of signal estimates. These estimates and the received signals are iteratively processed a prescribed number of times to refine the weighting coefficients, such that the gain and/or nulls of antenna's directivity pattern will maximize the signal to noise ratio. Such improved functionality is particularly useful in association with the phased array antenna of a base station of a time division multiple access (TDMA) cellular communication system, where it is necessary to cancel interference from co-channel users located in cells adjacent to the cell containing a desired user and the base station.

A low-cost 8 to 26.5 GHz phased array antenna using a piezoelectric transducer controlled phase shifter

Abstract: A new phased array antenna of wide bandwidth and good beam scanning angle has been developed using a low cost multiline phase shifter controlled by a piezoelectric transducer (PET) and a stripline fed Vivaldi antenna array. The multiline progressive PET phase shifter has a low perturbation loss of less than 2 dB and a total loss of less than 4 dB up to 40 GHz with a maximum phase shift of 480/spl deg/. The proposed phased array antenna consists of four E- or H-plane Vivaldi antennas, a PET phase shifter, and a power divider. The phased array shows a wide beam scanning capability of /spl plusmn/27/spl deg/ over a wide bandwidth from 8 to 26.5 GHz covering X, Ku, and K bands.

Microelectromechanical phased array antenna

Abstract: An array antenna includes a radiator layer having first and second opposing surfaces and a plurality of radiators disposed on a first surface of the radiator layer. Additionally the antenna includes a microelectromechanical systems (MEMS) layer with a plurality of MEMS phase shifters disposed adjacent to the second surface of the radiator layer, each one of the plurality of MEMS phase shifters electromagnetically coupled to at least one of the plurality of radiators. Finally, a beamformer layer is electromagnetically coupled to the MEMS layer, and a spacer layer is disposed between the MEMS layer and the beamformer layer. A second embodiment is provided from multiple layers and utilizes a plurality of subarray structures which are coupled to form the entire array aperture.

Synthesis of electronically steerable antenna arrays with elements on concentric rings with reduced sidelobes

Abstract: In conventional scanned antenna arrays, the elements are mostly distributed on uniformly spaced grids. The distribution of the array elements on concentric rings has however several advantages to these conventional arrays, notably a lower maximum sidelobe level as the conventional grating lobe mechanism no longer holds. In this paper the authors propose a method to reduce the maximum sidelobe level of an array with a given number of elements. The amplitude of the excitation of the array elements has the same value for all directions. The authors also propose a method for fast array factor computation for concentric ring grid arrays.

Ferroelectric/paraelectric/composite material loaded phased array network

Abstract: The present invention is directed generally to phased array antennas. The invention allows for the realization of a low-cost, ferroelectric material loaded feed manifold for phase shifting an antenna. This type of architecture can take many forms, with the preferred embodiment being waveguide. In an embodiment of the present invention, the Ferroelectric/Paralectric/Composite material loaded feed manifold described herein may solve the space/weight problem by integrating the material into the traditional waveguide feed manifold. A feed structure suitable for receiving and routing electromagnetic energy may include a subassembly including material suitable for shifting phase of electromagnetic radiation when an electrical field is applied. Material having a dielectric constant at least one of equal to and greater than the phase shifting material may also be included.

Low profile phased array antenna

Abstract: An improved phased array antenna having a low profile is disclosed. The antenna has a polarizer and a rotating phased array. MEMS phase shifters are used for electronically controlling relative phase shift between antenna elements and MEMS switches employed to provide beam steering and polarization switching.

Amplification of an optical WDM signal

Abstract: The invention relates to a method for amplifying an optical signal and to an amplifier unit (OFA) to which an optical input signal comprising a plurality of wavelength channel signals each at its dedicated wavelength is supplied. In the method, (a) demultiplexing is carried out to separate each wavelength channel signal from the input signal, (b) a first multiplexing is carried out, combining each separated wavelength channel signal with a separate pump signal, (c) each combination of a wavelength channel signal and pump signal is guided to its dedicated amplifier means (FA 1 . . . FA 4 ), and (d) the pump signals are separated from the amplified wavelength channel signals obtained from the amplifier means and a second multiplexing is carried out, combining the amplified wavelength channel signals into an outgoing WDM signal. To enable a solution based on several parallel amplifiers to be implemented in a simpler manner than heretofore, the same waveguide phased array component is used for processing both the wavelength channel signals and the pump signals at the output end, input end or both ends of the amplifier unit. For the input end, this means that the demultiplexing of the input signal and the first multiplexing are carried out using the same waveguide phased array component (WGA 1 ).

Ferroelectric thin film and broadband satellite systems

Abstract: There are several microwave applications where tunable ferroelectric devices could play a key role in improving system performance, or they could provide the key technology that enables a system to be deployed. This article focuses on the Ka-band phased array antennas, but tunable filters, oscillators, and switches could also utilize these materials.

Printed or etched, folding, directional antenna

Abstract: An antenna array formed on a deformable dielectric material or substrate includes a center element and plurality of radial elements extending from a center hub. In the operative mode, the radial elements are folded upwardly into an approximately vertical position, with the center element at the center of the hub and the radial elements circumferentially surrounding the center element. In one embodiment the center element serves an active element of the antenna array and the radial elements are controllable in a directive or reflective state to effect a directive beam pattern from the antenna array. When not in use, the antenna elements are deformed into a plane and can therefore be integrated into a housing for compact storage. In a phased array embodiment, the center element is absent and the plurality of radial elements, are controllable to steer the antenna beam.

Moving target feature extraction for airborne high-range resolution phased-array radar

Abstract: We study the feature extraction of moving targets in the presence of temporally and spatially correlated ground clutter for airborne high-range resolution (HRR) phased-array radar. To avoid the range migration problems that occur in HRR radar data, we first divide the HRR range profiles into low-range resolution (LRR) segments. Since each LRR segment contains a sequence of HRR range bins, no information is lost due to the division, and hence, no loss of resolution occurs. We show how to use a vector auto-regressive (VAR) filtering technique to suppress the ground clutter, Then, a parameter estimation algorithm is proposed for target feature extraction. From the VAR-filtered data, the target Doppler frequency and the spatial signature vectors are first estimated by using a maximum likelihood (ML) method. The target phase history and direction-of-arrival (DOA) (or the array steering vector for an unknown array manifold) are then estimated from the spatial signature vectors by minimizing a weighted least squares (WLS) cost function. The target radar cross section (RCS)-related complex amplitude and range-related frequency of each target scatterer are then extracted from the estimated target phase history by using RELAX, which is a relaxation-based high-resolution feature extraction algorithm. Numerical results are provided to demonstrate the performance of the proposed algorithm.

High capacity broadband cellular/PCS base station using a phased array antenna

Abstract: A high capacity broadband base station employs a wideband radio and phased array processing subsystem. The phased array antenna subsystem contains multiple sets or pairs of alternating receive only and transmit/receive elements distributed in a two dimensional spatial array. Each digital wideband radio performs both receive and transmit channel signal processing. In the receive direction, the digital representation of the entire spectrum for each antenna element is divided into channels for the particular waveform of interest. For a 5 MHz PCS GSM, the digital wideband radio separates twenty-four carriers into twenty-four (200 KHz wide) data streams, each of which is representative of a respective channel, and couples each channel to a digital signal processor. In the transmit direction, the radio combines the digital representations of the twenty-four individual channels supplied by the DSP into a single wideband channel for transmission.

A new architecture for a single-chip multi-channel beamformer based on a standard FPGA

Abstract: A new architecture for a compact medical ultrasound beamformer has been developed. Combination of novel and known principles has been utilized, leading to low processing power requirements and simple analog circuitry. Usage of a field programmable gate array (FPGA) for the digital signal processing provides programming flexibility. First, sparse sample processing is performed by generating the in-phase and quadrature beamformed signals. Hereby only 512 samples are beamformed for each line in an image. That leads to a 15-fold decrease in the number of operations and enables the use of Delta-Sigma (/spl Delta//spl Sigma/) modulation analog-to-digital converters (ADC). Second, simple second-order /spl Delta//spl Sigma/ modulation ADC with classic topology is used. This allows for simple analog circuitry and a very compact design. Several tens of these together with the corresponding preamplifiers can be fitted together onto a single analog integrated circuit. Third, parameter driven delay generation is used, using 3 input parameters per line per channel for either linear array imaging or phased array imaging. The delays are generated on the fly. The delay generation logic also determines the digital apodization by using 2 additional parameters. The control logic consists of few adders and counters and requires very limited resources. Fourth, the beamformer is fully programmable. Any channel can be set to use an arbitrary delay curve, and any number of these channels can be used together in an extendable modular multi-channel system. A prototype of the digital logic is implemented using a Xilinx Virtex-E series FPGA. A 5 MHz center frequency is used along with an oversampling ratio of 14. The sampling clock frequency used is 140 MHz and the number of channels in a single Xilinx 1 million gate FPGA XCV600E is 32. The beamformer utilizes all of the BlockRAM of the device and 33% of its Core Logic Block (CLB) resources. Both simulation results and processed echo data from a phantom are presented.