Showing papers on "Phased array published in 2004"

A fully integrated 24-GHz eight-element phased-array receiver in silicon

Abstract: This paper reports the first fully integrated 24-GHz eight-element phased-array receiver in a SiGe BiCMOS technology. The receiver utilizes a heterodyne topology and the signal combining is performed at an IF of 4.8 GHz. The phase-shifting with 4 bits of resolution is realized at the LO port of the first down-conversion mixer. A ring LC voltage-controlled oscillator (VCO) generates 16 different phases of the LO. An integrated 19.2-GHz frequency synthesizer locks the VCO frequency to a 75-MHz external reference. Each signal path achieves a gain of 43 dB, a noise figure of 7.4 dB, and an IIP3 of -11 dBm. The eight-path array achieves an array gain of 61 dB and a peak-to-null ratio of 20 dB and improves the signal-to-noise ratio at the output by 9 dB.

Phased array metamaterial antenna system

Abstract: An efficient, low-loss, low sidelobe, high dynamic range phased-array radar antenna system is disclosed that uses metamaterials, which are manmade composite materials having a negative index of refraction, to create a biconcave lens architecture (instead of the aforementioned biconvex lens) for focusing the microwaves transmitted by the antenna. Accordingly, the sidelobes of the antenna are reduced. Attenuation across microstrip transmission lines may be reduced by using low loss transmission lines that are suspended above a ground plane a predetermined distance in a way such they are not in contact with a solid substrate. By suspending the microstrip transmission lines in this manner, dielectric signal loss is reduced significantly, thus resulting in a less-attenuated signal at its destination.

Microstrip antenna phased array with electromagnetic bandgap substrate

Abstract: Uniplanar compact electromagnetic bandgap (UC-EBG) substrate has been proven to be an effective measure to reduce surface wave excitation in printed antenna geometries. This paper investigates the performance of a microstrip antenna phased array embedded in an UC-EBG substrate. The results show a reduction in mutual coupling between elements and provide a possible solution to the "blind spots" problem in phased array applications with printed elements. A novel and efficient UC-EBG array configuration is proposed. A probe fed patch antenna phased array of 7/spl times/5 elements on a high dielectric constant substrate was designed, built and tested. Simulation and measurement results show improvement in the active return loss and active pattern of the array center element. The tradeoffs used to obtain optimum performance are discussed.

Ultrasound apparatus and method for augmented clot lysis

Abstract: An apparatus and method for using ultrasound augmented with microbubbles, thrombolytic drugs or other agents for clot lysis wherein at least one ultrasound transducer (20) generates a plurality of acoustic signals and time, amplitude, phase and frequency modulation of the signals to provide more uniform power delivery with fewer gaps in the ultrasound field. Interference patterns from one or multiple transducers (12, 13, 14, 16, 20) are constantly shifted in position. A phased array (30) of transducers (31) may generate a directed beam that is swept over an area or directed to a specific location. In another embodiment, an array of transducers (12, 13, 14, 16, 20, 30) may generate ultrasound at a number of slightly varying frequencies to produce an interference pattern that sweeps in and out through the targeted tissue. A single array may be used to produce both effects simultaneously or separately.

Active device tracking and high-resolution intravascular MRI using a novel catheter-based, opposed-solenoid phased array coil.

Abstract: A novel two-element, catheter-based phased array coil was designed and built for both active MR device tracking and high-resolution vessel wall imaging. The device consists of two independent solenoid coils that are wound in opposite directions, connected to separate receive channels, and mounted collinearly on an angiographic catheter. The elements were used independently or together for tracking or imaging applications, respectively. The array's dual functionality was tested on a clinical 1.5 T MRI scanner in vitro, in vivo, and in situ. During real-time catheter tracking, each element gave rise to a high-amplitude peak in the respective projection data, which enabled reliable and robust device tracking as well as automated slice positioning. In vivo microimaging with 240 μm in-plane resolution was achieved in 9 s using the device and TrueFISP imaging. Therefore, a single device was successfully implemented that met the combined requirements of intravascular device tracking and imaging. Magn Reson Med 51:668–675, 2004. © 2004 Wiley-Liss, Inc.

Wireless power transmission utilizing a phased array of Tesla coils

Abstract: This thesis discusses the theory and design of coupled resonant systems and how they can be linked in a phased array for the wireless transmission of electrical power. A detailed derivation of their operational theory is presented with a strong emphasis on the current and voltage waveforms produced. Formulas are presented relating the features of the waveforms to specific parameters of the system. They provide a theoretical basis for the design of the Tesla coil systems. Unloaded and loaded operating efficiency is considered from both a power and energy perspective with emphasis on maximizing the two quantities. With these design formulas, a working set of two distinct coupled resonant systems were locked in frequency and controllable in phase to produce a phased array capable of wireless power transmission. The operational details and practical design considerations are presented and explained. The measured output waveforms were found to closely agree with the predicted models. Thesis Supervisor: Chathan M. Cooke Title: Lecturer and Principal Research Engineer

Electronically steerable parasitic array radiator antenna

Abstract: The electronically steerable parasitic array radiator antenna consists of one feed radiating element and parasitic radiating elements placed in the near field of the active radiator. A beam is formed due to spatial electromagnetic field coupling among radiating elements. The radiation pattern is electronically controlled by means of the variable capacitance devices (varactors) loading the parasitic elements. Unlike a conventional phased array, only one transmitter and receiver are needed for system configuration. Therefore, adaptive beamforming of low dissipation power and low fabrication cost can be achieved. On the other hand, there is only one output port to observe the signal and the weights can be controlled indirectly via reactors instead of direct control. In addition, due to interelement mutual coupling and the parasitic element being directly connected to the reactive device, the linear adaptive array theory developed to date cannot be applied straightforward. In this paper, the configuration of this antenna, its operating principle and formulation, and its measurement method, control scheme, and applications to signal processing are presented. We describe a mathematical model to simulate the radio frequency behavior of the antenna, the equivalent weight vector used for formulation of the characteristics, the admittance matrix including varactors, the effective element length, the equivalent steering vector method, the method for effectively extending the variable range of the capacitance of the varactor, the reactance circuit to cancel nonlinear distortions, the method for calibration of varactors and radiation pattern by measurement of near field of the radiating element, the learning criteria used to control radiation patterns autonomously in adaptation to the electromagnetic environment, the reactance optimization algorithm, the concept of the reactance domain signal processing and the direction of arrival estimation based on such a process, and diversity reception and spatial correlation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(10): 25–45, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20081

Detection, location, and imaging of fast moving targets using multifrequency antenna array SAR

Abstract: In this correspondence, we generalize the linear antenna array synthetic aperture radar (SAR) from transmitting single-wavelength signals to transmitting multiple-wavelength signals (called multifrequency antenna array SAR). We show that, using multifrequency antenna array SAR, not only the clutters can be suppressed but also the locations of both slow and fast moving targets can be accurately estimated: A robust Chinese remainder theorem (CRT) is developed and used for the location estimation of fast and slowly moving targets. Simulations of SAR imaging of ground moving targets are presented to show the effectiveness of the multifrequency antenna array SAR imaging algorithm.

Time-domain combination of MR spectroscopy data acquired using phased-array coils.

Abstract: A new method for efficiently processing MRS data acquired with phased-array coils is presented. The method consists of performing phase compensation (i.e., redefining the signal phase relative to a common reference) of the signals in the time domain prior to combining the signals. The resulting spectra are equivalent to those obtained by previously published methods for phased-array spectral data processing (i.e., processing the signals individually and then combining them in the frequency domain). The method allows spectra acquired with phased-array coils to be processed as efficiently as those acquired with non-phased-array coils. Both single voxel spectroscopy (SVS) and chemical shift imaging (CSI) data sets may be processed by this method.

Directional piezoelectric phased array filters for detecting damage in isotropic plates

Abstract: Phased array filters using piezoelectric sensors are presented as an approach to detect damage in isotropic plates. Plate dynamics can be described in terms of wave propagation. Boundaries and other discontinuities, such as damage, produce reflections from incident wavefronts. Phased arrays, acting as a directional filter, can be used along with a wave propagation approach to look in different directions on a plate. Damage to the plate can be inferred if there is a significant change in the transient response of the plate. The location of this damaged area can be determined using the phased sensor array response. This paper presents results from simulated damage on an isotropic plate. A piezoelectric sensor array is used to actively interrogate the plate to determine the presence and location of damage using low frequency Lamb waves.

The post-processing of ultrasonic array data using the total focusing method

Abstract: The use of ultrasonic arrays for NDT has increased significantly in recent years. This is due to the flexibility of array systems which can be electronically configured to produce plane, focused, steered and steer-focusedbeams. In this way, one array transducer can do the job of many standard single-element transducers. Currently, the approach is to have independently controlled parallel pulser-receiver channels connected to a number of array elements. These channels allow timing delays to be applied to each element on both transmission and reception. In this way a specific set of transmit-receive delays are applied to an array to create a specific beam profile. This paper describes an alternative approach in which the complete raw data set offline domain signals from every transmitter-receiver pair is collected, stored and post-processed. Theoretically, the time taken to acquire this data is approximately the same as that taken to perform a B-scan with the array. The key advantage is that post-processing of the complete raw data set enables any beam profile to be recreated. Additionally, this approach allows novel inspections to be performed which would be impossible with single-element transducers and impractical using the traditional phased array controller methodology. This paper concerns one such post-processing algorithm, the Total Focusing Method (TFM). In the TFM, an image is created in which the beam has been focused on every point within the field of view. This optimises the focusing performance of a given array. The use of the TFM is then demonstrated on a number of test structures and is proposed as a superior alternative to conventional array test techniques.

Phased array knee coil

Abstract: A phased-array knee coil is provided and includes a transmit coil array and a receive coil array having a plurality of coils configured to provide a first imaging mode and a second imaging mode.

A fully integrated 24-GHz eight-element phased-array receiver in silicon

Abstract: This paper reports the first fully integrated 24-GHz eight-element phased-array receiver in a SiGe BiCMOS technology. The receiver utilizes a heterodyne topology and the signal combining is performed at an IF of 4.8 GHz. The phase-shifting with 4 bits of resolution is realized at the LO port of the first down-conversion mixer. A ring LC voltage-controlled oscillator (VCO) generates 16 different phases of the LO. An integrated 19.2-GHz frequency synthesizer locks the VCO frequency to a 75-MHz external reference. Each signal path achieves a gain of 43 dB, a noise figure of 7.4 dB, and an IIP3 of -11 dBm. The eight-path array achieves an array gain of 61 dB and a peak-to-null ratio of 20 dB and improves the signal-to-noise ratio at the output by 9 dB.

A fully integrated 24 GHz 8-path phased-array receiver in silicon

Abstract: A fully integrated 8-channel phased-array receiver at 24 GHz is demonstrated. Each channel achieves a gain of 43 dB, noise figure of 8 dB, and an IIP3 of -11dBm, consuming 29 mA of current from a 2.5 V supply. The 8-channel array has a beam-forming resolution of 22.5/spl deg/, a peak-to-null ratio of 20 dB (4-bits), a total array gain of 61 dB, and improves the signal-to-noise ratio by 9 dB.

Transmitter patterns for multi beam reception

Abstract: Provided herein is a method for use in medical applications that permits (1) affordable three-dimensional imaging of blood flow using a low-profile easily-attached transducer pad, (2) real-time blood-flow vector velocity, and (3) long-term unattended Doppler-ultrasound monitoring in spite of motion of the patient or pad. The pad and associated processor collects and Doppler processes ultrasound blood velocity data in a three dimensional region through the use of a planar phased array of piezoelectric elements. The invention locks onto and tracks the points in three-dimensional space that produce the locally maximum blood velocity signals. The integrated coordinates of points acquired by the accurate tracking process is used to form a three-dimensional map of blood vessels and provide a display that can be used to select multiple points of interest for expanded data collection and for long term continuous and unattended blood flow monitoring. The three dimensional map allows for the calculation of vector velocity from measured radial Doppler. A thinned array (greater than half-wavelength element spacing of the transducer array) is used to make a device of the present invention inexpensive and allow the pad to have a low profile (fewer connecting cables for a given spatial resolution). The full aperture is used for transmit and receive so that there is no loss of sensitivity (signal-to-noise ratio) or dynamic range. Utilizing more elements (extending the physical array) without increasing the number of active elements increases the angular field of view. A further increase is obtained by utilizing a convex non-planar surface.

A spectrally clean transmitting system for solid-state phased-array radars

Abstract: Navy radar operations are being curtailed in a littoral environment. This is due to two factors: the encroachment of cell phone systems into the naval radar bands; in-band interference from other radars. The spectral width of most pulsed radars is significantly wider than necessary with present modulation schemes. Most radars utilize some form of constant envelope pulse with phase or frequency modulation. This causes the spectrum to broaden to several times the information bandwidth. If both the amplitude and phase of the transmitted signal are allowed to change, a significantly narrower bandwidth can be achieved. The paper presents a method to create waveforms with instantaneous bandwidths of 20 MHz confined within -100 dB. The theoretical spectral results of three popular phase modulation schemes (phase shift keying, minimum phase shift keying and derivative phase shift keying) are compared with the spectrally clean results. In addition, the Chireix out-phasing method is presented as an alternative to generating amplitude and phase modulated waveforms. The Chireix method provides a way of improving the efficiency compared to the conventional class A power amplifier. Preliminary results are shown for a spectrally clean waveform.

Elimination of scan blindness in phased array of microstrip patches using electromagnetic bandgap materials

Abstract: Electromagnetic bandgap (EBG) material is applied in the design of a phased array of rectangular microstrip patches. The surface-waves could be suppressed by the frequency bandgap and, therefore, the scan blindness could be eliminated. A high-impedance surface is chosen as EBG structure, and the numerical simulation is performed by periodic Green's functions plus the moment method. Both the bandgap curve of the EBG structure and the scan characteristics of the phased arrays have been calculated. The elimination of scan blindness is observed.

Scan blindness free phased array design using PBG materials

Abstract: Scan blindness occurs for phased arrays when propagation constants of Floquet modes (space harmonics) coincide with those of surface waves supported by the array structure. In this paper, we studied the possibility of using photonic band-gap (PBG) substrate to eliminate scan blindness. A specially designed printed PBG substrate can suppress surface wave propagation inside its bandgap range, therefore it can be used to eliminate scan blindness. In this paper, we presented a method of moments (MoM) analysis of the scan properties of dipole arrays on PBG substrates with ominidirectional bandgap(s). We found that scan blindness is completely eliminated. The elimination of scan blindness makes PBG materials very attractive in phased array design.

Photonic microwave arbitrary waveform generation using a virtually imaged phased-array (VIPA) direct space-to-time pulse shaper

Abstract: We present the first direct space-to-time pulse shaper using a virtually imaged phased array as the spectral disperser. We use this pulse shaper to demonstrate generation of 10-50-GHz arbitrary microwave waveforms with time apertures as large as 1.0 ns and peak-to-peak amplitudes as high as 400 mV.

Phased array systems in silicon

Abstract: Phased array systems, a special case of MIMO systems, take advantage of spatial directivity and array gain to increase spectral efficiency. Implementing a phased array system at high frequency in a commercial silicon process technology presents several challenges. This article focuses on the architectural and circuit-level trade-offs involved in the design of the first silicon-based fully integrated phased array system operating at 24 GHz. The details of some of the important circuit building blocks are also discussed. The measured results demonstrate the feasibility of using integrated phased arrays for wireless communication and vehicular radar applications at 24 GHz.

Quasi-optic synthetic phased-array terahertz imaging

Abstract: A quasi-optic terahertz (THz) imaging system that utilizes optoelectronic methods for pulsed THz generation and reception and optical methods for image formation is demonstrated and theoretically explained. The system can be used to produce coherent, field amplitude, and energy density images with diffraction-limited resolution in two transverse dimensions. Simultaneous bandwidth-limited resolution is achieved in the depth dimension by means of the ranging capabilities of the system. The system is shown to accurately produce images of several objects to verify diffraction-limited imaging. Imaging power is extended by aperture synthesis to result in transverse resolution the order of a wavelength. Several individual, coherent images are recorded, each synthetically appearing to be formed by a different element of an optical phased array. The multiple images are simply superposed to create a higher-resolution image. Theoretical calculations fully describe the broadband imaging and include aberration and diffraction effects to further verify system performance. Calculated images are a good match with experimental results.

MoM simulation of signal-to-noise patterns in infinite and finite receiving antenna arrays

Abstract: An approach based on the method of moments is presented for the computation of the sensitivity of infinite and finite receiving phased arrays with active beamforming networks. The sensitivity is characterized in terms of signal-to-noise element patterns. Coupling of noise through the array is included in the analysis, as well as noise resulting from losses in the antennas. Simulation results are shown for arrays consisting of tapered-slot antennas made of metallic plates. For finite arrays, the average signal-to-noise ratio per element is not necessarily smaller than in the infinite-arraycase. For an 8/spl times/8 array, the average signal-to-noise element pattern is somewhat more narrow than for the infinite array. At broadside, the sensitivity of relatively small arrays (4/spl times/4 to 8/spl times/8) is described within order 1 dB by the infinite-array solution.

Phased array antenna with discrete capacitive coupling and associated methods

Abstract: A phased array antenna (100) includes a substrate (104), and an array of dipole antenna elements (40) on the substrate (104). Each dipole antenna element (40) comprises a medial feed portion (42), and a pair of legs (44) extending outwardly therefrom, and adjacent legs (44) of adjacent dipole antenna elements (40) include respective spaced apart end portions (46). A respective impedance element is electrically connected between the spaced apart end portions (46) of adjacent legs (44) of adjacent dipole antenna elements (40) for providing increased capacitive coupling therebetween.

Optical true time-delay feeder for X-band phased array antennas composed of 2/spl times/2 optical MEMS switches and fiber delay lines

Abstract: We proposed an optical true time-delay (TTD) feeder for X-band linear phased array antennas (PAAs), which possesses high-speed beam scan capability by selecting different lengths of fiber delay lines with fast 2/spl times/2 optical microelectromechanical system switches. For proof of concept, a 3-bit optical TTD has been built for a 10-GHz linear PAA composed of two antenna elements. Experimental results show that the maximum time-delay error is less than 0.2 ps, corresponding to a radiation angle error of less than 0.84/spl deg/, which is within the equipment resolution. We have also designed a 10-GHz linear PAA composed of eight microstrip patch antenna elements driven by the proposed TTD. The radiation patterns of this PAA have been obtained by simulation.

Phased array antenna interconnect having substrate slat structures

Abstract: A phased array antenna is provided having a plurality of phase shifter devices for phase shifting and beam steering a radiated beam of the phased array antenna. The plurality of phase shifter devices are interconnected with an interconnect structure comprising a plurality of linear array substrate slats. Each linear array substrate slat includes a plurality of radiating elements formed using first and second metal layers of the substrate slat, a plurality of phase shifter devices and a common RF feed conductor for the plurality of radiating elements. The common RF feed conductor is formed on a third metal layer of the substrate slat that is disposed between the first and second metal layers. The common RF feed conductor is configured to include a single location for electrical connections to receive RF signals for the plurality of radiating elements. The phased array antenna also includes bias/control conductors applied to selected areas of the third metal layer, a fourth metal layer applied over the second metal layer and a shielding metal layer applied on the fourth metal layer. The bias/control conductors are configured to include a single location for electrical connections to receive bias voltages and control signals. The fourth metal layer includes circuit connections from the bias/control circuitry to the plurality of phase shifter devices. Each phase shifter device is attached to a radiating element via a mounting location on the shielding metal layer. Accordingly, a phased array antenna interconnect structure is provided that reduces the number of electrical connections required to provide RF signals and bias/control signals to multiple radiating elements and phase shifters, respectively, of the phased array antenna and provides a cost effective phased array antenna architecture that has a single locus of electrical connection for RF and bias control signals embedded in a multi-layer linear array or slat substrate of the phased array antenna.

Mutual coupling method for calibrating a phased array

Abstract: A method for calibrating a phase array antenna comprises performing initial measurements of array antenna elements to ensure that calibration measurements are within the linear dynamic range of receive elements contained within the array. The method includes deriving calibration coefficients from a direct measurement of a forced out of phase condition and detection of deep nulls through adjustment of amplitude and phase settings over a range of frequencies of interest.

Two-dimensional ultrasound phased array design for tissue ablation for treatment of benign prostatic hyperplasia.

Abstract: This paper describes the design, construction and evaluation of a two-dimensional ultrasound phased array to be used in the treatment of benign prostatic hyperplasia. With two-dimensional phased arrays, the focal point position can be controlled by changing the electrical power and phase to the individual elements for focusing and electronically steering in a three-dimensional volume. The array was designed with a steering angle of ±14° in both transverse and longitudinal directions. A piezoelectric ceramic (PZT-8) was used as the material of the transducer, since it can handle the high power needed for tissue ablation and a matching layer was used for maximum acoustic power transmission to tissue. Analysis of the transducer ceramic and cable impedance has been designed for high power transfer with minimal capacitance and diameter. For this initial prototype, the final construction used magnet compatible housing and cabling for future application in a clinical magnetic resonance imaging system for tempera...

Null steering in phased arrays by controlling the positions of selected elements

Abstract: A new technique is presented that is capable of steering nulls in the antenna pattern in the directions of strong interference signals without affecting the main beam. The technique is based on the element position perturbations of selected elements of the antenna array. This technique frees the phase shifters to be used solely for steering the main beam toward the direction of the desired signal. It also freezes the positions of those elements that have insignificant contributions to the nulls. Our results have shown to be comparable to the results obtained from the method of controlling the positions of all elements.