Phased array

About: Phased array is a research topic. Over the lifetime, 19428 publications have been published within this topic receiving 229231 citations. The topic is also known as: Phased Array Radar, PAR.

Phased array acoustic systems with intra-group processors

Abstract: The disclosed ultrasound imaging apparatus and method use a transducer array with a very large number of transducer elements or a transducer array with many more transducer elements than beamformer channels. The imaging apparatus includes a transmit array including a multiplicity of transducer elements allocated into several transmit sub-arrays, and a receive array including a multiplicity of transducer elements allocated into several receive sub-arrays. The apparatus also includes several intra-group transmit processors, connected to the transmit sub-arrays, constructed and arranged to generate a transmit acoustic beam directed into a region of interest, and several intra-group receive processors connected to the receive sub-arrays. Each intra-group receive processor is arranged to receive, from the transducer elements of the connected sub-array, transducer signals in response to echoes from the transmit acoustic beam. Each intra-group receive processor includes delay and summing elements constructed to delay and sum the received transducer signals. The apparatus also includes a receive beamformer including several processing channels connected to the intra-group receive processors, wherein each processing channel includes a beamformer delay constructed and arranged to synthesize receive beams from the echos by delaying signals received from the intra-group receive processor, and a beamformer summer (a summing junction) constructed and arranged to receive and sum signals from the processing channels. An image generator is constructed and arranged to form an image of the region of interest based on signals received from the receive beamformer. The apparatus is practical in size, cost and complexity and is sufficiently fast to provide two-dimensional or three-dimensional images of moving body organs.

Frequency Diverse MIMO Techniques for Radar

Abstract: It has been shown over several decades of radar research that the exploitation of diversity in a number of domains (space, frequency, time, polarization, and, recently, waveform) can provide increased agility, flexibility, robustness, and capabilities to the radar system. However this is often achieved either through efforts in system design, increased hardware complexity, or by employing additional resources. A conventional antenna array is considered with the intention of introducing, not major, but minor mismatches, in particular in the carrier frequencies and, eventually in the codes at the element level. The starting point of this analysis is the frequency diverse array (FDA), which has been demonstrated to generate a range-angle pattern. Through a reconsideration of the organization of the array, which we have termed the wavelength array (WA), a new pattern, "orthogonal" to that of the standard phased array, can be achieved. The bistatic combination of a WA and a receiver leads to the frequency diverse bistatic system (FDBS), which can be a significant application of this concept. In a second stage the analysis focuses on the effects of introducing waveform diversity in such a system. In particular, if the elements of an electronically steered array (ESA) simultaneously transmit a number of pseudonoise (PN) codes at slightly different carrier frequencies, the coherent summation of the codes gives rise to a waveform whose shape is a function of both angle and range. In fact this is the consequence of applying the multiple-input multiple-output (MIMO) technique to the FDA, which has the result of associating a waveform to each point range/angle of the space, with the possibility of recovering this information in receive after appropriate processing.

Joint Range and Angle Estimation Using MIMO Radar With Frequency Diverse Array

Abstract: Phased array is widely used in radar systems with its beam steering fixed in one direction for all ranges. Therefore, the range of a target cannot be determined within a single pulse when range ambiguity exists. In this paper, an unambiguous approach for joint range and angle estimation is devised for multiple-input multiple-output (MIMO) radar with frequency diverse array (FDA). Unlike the traditional phased array, FDA is capable of employing a small frequency increment across the array elements. Because of the frequency increment, the transmit steering vector of the FDA-MIMO radar is a function of both range and angle. As a result, the FDA-MIMO radar is able to utilize degrees-of-freedom in the range-angle domains to jointly determine the range and angle parameters of the target. In addition, the Cramer–Rao bounds for range and angle are derived, and the coupling between these two parameters is analyzed. Numerical results are presented to validate the effectiveness of the proposed approach.

Range Compression and Waveform Optimization for MIMO Radar: A CramÉr–Rao Bound Based Study

Abstract: A multi-input multi-output (MIMO) radar system, unlike standard phased-array radar, can transmit via its antennas multiple probing signals that may be correlated or uncorrelated with each other. This waveform diversity offered by MIMO radar enables superior capabilities compared with a standard phased-array radar. One of the common practices in radar has been range compression. We first address the question of ldquoto compress or not to compressrdquo by considering both the Cramer-Rao bound (CRB) and the sufficient statistic for parameter estimation. Next, we consider MIMO radar waveform optimization for parameter estimation for the general case of multiple targets in the presence of spatially colored interference and noise. We optimize the probing signal vector of a MIMO radar system by considering several design criteria, including minimizing the trace, determinant, and the largest eigenvalue of the CRB matrix. We also consider waveform optimization by minimizing the CRB of one of the target angles only or one of the target amplitudes only. Numerical examples are provided to demonstrate the effectiveness of the approaches we consider herein.

Space-time processing for multichannel synthetic aperture radar

Abstract: Synthetic aperture radar (SAR) provides high-resolution images of a non-moving ground scene, but fails to indicate the presence and position of moving objects. As in airborne MTI (moving-target indication) systems the solution to this problem is to use an array of antennas or subapertures and several receiving channels ('MSAR', or multichannel SAR), and to apply multichannel clutter suppression. One of the most efficient methods is adaptive space-time processing (STAP), which can be simplified to frequency-dependent spatial processing in the Doppler domain. Some of these techniques applied to SAR are reviewed and illustrated with data gathered by the German experimental multichannel SAR system 'AER-II'.