Transmit beamspace design for direction finding in colocated MIMO radar with arbitrary receive array (original) (raw)
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1 Efficient Transmit Beamspace Design for Search-free Based DOA Estimation in MIMO Radar
2016
In this paper, we address the problem of transmit beamspace design for multiple-input multiple-output (MIMO) radar with colocated antennas in application to direction-ofarrival (DOA) estimation. A new method for designing the transmit beamspace matrix that enables the use of searchfree DOA estimation techniques at the receiver is introduced. The essence of the proposed method is to design the transmit beamspace matrix based on minimizing the difference between a desired transmit beampattern and the actual one while enforcing the constraint of uniform power distribution across the transmit array elements. The desired transmit beampattern can be of arbitrary shape and is allowed to consist of one or more spatial sectors. The number of transmit waveforms is even but otherwise arbitrary. To allow for simple search-free DOA estimation algorithms at the receive array, the rotational invariance property is established at the transmit array by imposing a specific structure on the beamspace matrix. Semidefinite programming relaxation is used to approximate the proposed formulation by a convex problem that can be solved efficiently. We also propose a spatialdivision based design (SDD) by dividing the spatial domain into several subsectors and assigning a subset of the transmit beams to each subsector. The transmit beams associated with each subsector are designed separately. Simulation results demonstrate the improvement in the DOA estimation performance offered by using the proposed joint and SDD transmit beamspace design methods as compared to the traditional MIMO radar technique.
Direction finding for MIMO radar with colocated antennas using transmit beamspace preprocessing
2009 3rd IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), 2009
The problem of direction finding for multiple targets in mono-static multiple-input multiple-output (MIMO) radar systems is considered. Assuming that the targets are located within a certain spatial sector, we focus the energy of multiple (two or more) transmitted orthogonal waveforms within that spatial sector using appropriately designed transmit beamforming. The transmit beamformers are designed so that matchfiltering the received data to the waveforms yields multiple (two or more) data sets with rotational invariance property that allows applying search-free direction finding techniques such as ESPRIT. Unlike previously reported MIMO radar ESPRITbased direction finding techniques, our method is applicable to arbitrary arrays and achieves better estimation performance at lower computational cost.
Partially adaptive transmit beamforming for search free 2D DOA estimation in MIMO radar
2015 23rd European Signal Processing Conference (EUSIPCO), 2015
In this paper, a partially adaptive two dimensional (2D) transmit beamforming approach is proposed to enable search-free azimuth and elevation direction of arrival (DOA) estimation in MIMO radar. Specifically, the 2D transmit array is nonadaptively partitioned into a number of subarrays. Then, a beamspace matrix is adaptively designed for each subarray, such that the beampatterns corresponding to each matrix have the exact same magnitude. By constraining the beams to be transmitted from different subarrays, multiple data invariances are enforced independently of the receive array geometry. The invariances are then exploited by search-free DOA estimation methods. Simulations validate the proposed approach.
Transmit Energy Focusing for DOA Estimation in MIMO Radar with Colocated Antennas
2010
In this paper, we propose a transmit beamspace energy focusing technique for multiple-input multiple-output (MIMO) radar with application to direction finding for multiple targets. The general angular directions of the targets are assumed to be located within a certain spatial sector. We focus the energy of multiple (two or more) transmitted orthogonal waveforms within that spatial sector using transmit beamformers which are designed to improve the signal-to-noise ratio (SNR) gain at each receive antenna. The subspace decomposition-based techniques such as MUSIC can then be used for direction finding for multiple targets. Moreover, the transmit beamformers can be designed so that matched-filtering the received data to the waveforms yields multiple (two or more) data sets with rotational invariance property that allows applying search-free direction finding techniques such as ESPRIT for two data sets or parallel factor analysis (PARAFAC) for more than two data sets. Unlike previously...
Transmit Radiation Pattern Invariance in MIMO Radar With Application to DOA Estimation
IEEE Signal Processing Letters, 2015
In this letter, we address the fundamental question of how many beamforming vectors exist which generate the same beampattern? The question is relevant to many fields such as, for example, array processing, radar, wireless communications, data compression, dimensionality reduction, and biomedical engineering. The desired property of having the same beampattern for different columns of a beamspace transformation matrix (beamforming vectors) often plays a key importance in practical applications. The result is that at most 2 M−1 − 1 beamforming vectors with the same beampattern can be generated from any given beamforming vector. Here M is the dimension of the beamforming vector. At the constructive side, the answer to this question allows for computationally efficient techniques for the beamspace transformation design. Indeed, one can start with a single beamforming vector, which gives a desired beampattern, and generate a number of other beamforming vectors, which give absolutely the same beampattern, in a computationally efficient way. We call the initial beamforming vector as the mother beamforming vector. One possible procedure for generating all possible new beamforming vectors with the same beampattern from the mother beamforming vector is proposed. The application of the proposed analysis to the transmit beamspace design in multiple-input multiple-output radar is also given.
2011 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2011
In this paper, we consider the problem of direction finding in multiple-input multiple-output (MIMO) radar based on focusing the transmitted pulse energy within certain spatial sector(s). We propose a method for designing the transmit weight matrix based on maximizing the energy transmitted within the desired spatial sector and minimizing the energy disseminated in the out-of-sector area. The proposed transmit energy focusing results in the signal-to-noise ratio increase at the receive array which in turn leads to lower Cramer-Rao bound and improved direction of arrival estimation performance. Simulation results show the substantial improvements offered by the proposed transmit energy focusing based MIMO radar as compared to the traditional MIMO radar and the MIMO radar with receive beamspace post-processing.
Transmit/receive beamforming for MIMO radar with colocated antennas
2009 IEEE International Conference on Acoustics, Speech and Signal Processing, 2009
We propose a new technique for multiple-input multiple-output (MIMO) radar with colocated antennas. The essence of the proposed technique is to partition the transmitting array into a number of subarrays that are allowed to overlap. Each subarray is used to coherently transmit a waveform which is orthogonal to the waveforms transmitted by other subarrays. Coherent processing gain can be achieved by designing a weight vector for each subarray to form a beam towards a certain direction in space. Moreover, the subarrays are combined jointly to form a MIMO radar resulting in higher resolution capabilities. Simulation results show the substantial improvements offered by the proposed technique as compared to previous techniques that validate its effectiveness.
Direction of Arrival Estimation Using a Cluster of Beams in a Cone-Shaped Digital Array Radar
2015 Sensor Signal Processing for Defence (SSPD), 2015
In this paper some potential system and processing advantages of conformal cone shaped digital array radar have been investigated, in particular in relation to potential alternative approaches for angle estimation with respect to the traditional monopulse. First of all potential benefit in terms of reduction of the number of radiating elements is shown when a conical array is considered with respect to a traditional system formed by four planar arrays, if a coverage of 360° must be assured. Secondly, having in mind an innovative digital array system where the received signals are analog to digital converted at element level and the corresponding data are possibly transferred to a central elaboration unit, an alternative approach is investigated for angular estimation. In this paper we derive the theoretical expression of the Cramer Rao Lower Bound for elevation angle estimation using a cluster of beams; we compare the limit performance of the traditional approach for angle estimation based on Sum and Difference beams with the approach based on a crowded cluster of RX beams properly spaced. The approaches show approximately equivalent performance, making the second particularly interesting for those situations where monopulse is known to experience performance degradation, as low elevation angle estimation; in this particular case an example of cluster design is shown, where the direct signal from a low altitude target must compete with a specular multipath.
Two-dimensional transmit beamforming for MIMO radar with sparse symmetric arrays
Multiple-input multiple-output (MIMO) radar using one-dimensional transmit arrays has been thoroughly investigated in the literature. In this paper, we consider the MIMO radar problem in the context of two-dimensional (2D) transmit arrays. In particular, we address the problem of transmit beamforming design using 2D arrays with symmetrically missing elements. This situation is encountered in practice when some of the array elements are assigned for a different purpose, e.g., for communication purposes. We cast the transmit beamforming problem as an optimization problem that minimizes the difference between a desired transmit beampattern and the actual one while satisfying constraints such as uniform transmit power across the array elements, sidelobe level control, etc. Moreover, different transmit beams can be enforced to have rotational invariance with respect to each other, a property that enables efficient computationally cheap 2D direction finding at the receiver. Semi-definite relaxation is used to recast the optimization problem as a convex one that can be solved efficiently using the interior point optimization methods. Simulations are used to validate the proposed method.