Null Steering Capability Research Articles

A joint array resource allocation and transmit beampattern design approach for multiple targets tracking

In this paper, we consider a joint array resource allocation and transmit beamforming approach to track multiple targets using phased array radar. Firstly, array allocation is accomplished by solving a constrained optimization problem formulated to minimize total tracking Cramer-Rao Lower Bound with antenna number as a constraint. A procedure to solve this problem is developed by checking Karush-Kuhn-Tucker conditions. Based on the allocated array resource, we develop a novel transmit beampattern design with null steering capability. The emitted signal model and objective functions of optimization are presented with a given power budget and null steering constraint. The resulted problem is revealed to be hard to tackle, therefore, we propose a cyclic algorithm scheme for solving it. The scheme separates the optimization into two problems, where each problem is transformed into simpler convex problems. Lastly, the projected gradient decent method with a penalty function is applied for the optimal design of beamforming with null steering. Simulation results show that the proposed array allocation solution provides better tracking accuracy, and the proposed beampattern design method outperforms conventional optimization methods in the optimal beamforming by achieving much deeper null steering and more accurate peak power in the given directions.

Modified CORPS beamforming network with null‐steering capability

This article proposes CORPS beamforming network (BFNs) with both beam and null steering capability. All simulation results are presented for scannable mono-beam configuration but it can be extended to the multi-beam system. Complex inputs are optimised by means of the PSO algorithm to get the array factor with the desired characteristics that are side lobe level (SLL), directivity (D), and null depth. All sub-blocks of the BFN are designed in the centre frequency of 2.4 GHz.

Investigation of Desired Element Pattern Reconfigurability in Small Adaptive Arrays

Pattern reconfigurable antennas implemented in small adaptive arrays can serve as practical solutions in applications, which are limited by available platform space while providing additional degrees of pattern control. This communication integrates the concept of pattern variability directly into an adaptive array optimization routine with a unique pattern reconfigurable antenna element equivalent model, allowing the algorithm to fully leverage the available reconfigurability—which may include individual pattern beam tilts and pattern nulls. Examples showcase the model’s impact on adaptive array performance via the signal-to-interference plus noise ratio metric. The results establish a pathway specifying the design requirements for pattern reconfigurable antennas to improve small adaptive array performance, demonstrating that designers should focus on the null steering capability of the antenna element in many cases.

Overlapped Subarray Architecture of an Wideband Phased Array Antenna with Interference Suppression Capability

This paper presents a novel architecture of combining the linear array of antenna elements, where each antenna element has digitally selectable true time-delays as weights. Use of time-delays for beam-formation inherently makes the phased array network a wideband system. In particular, this technique envisage a new method of sharing antenna elements, by fixed overlapped sub-array architecture, which is able to maintain permissible element spacing to avoid grating lobe in antenna pattern. Moreover, this scheme additionally offers an easier null steering capability to the subarray architecture. This method essentially eliminates the need for intensive computation of complex weight vectors attached to each antenna element.

Wideband beam and null steering using a rectangular array of planar monopoles

This article presents the design of a wideband rectangular array of planar monopoles, which is able to steer its beam and nulls over a wide frequency band using real-valued weights. These weights can be realized in practice by amplifiers or attenuators leading to a low cost development of a wideband array antenna with beam and null steering capability. The weights are determined by applying an inverse discrete Fourier transform to an assumed radiation pattern. This wideband beam and null forming concept is verified by full electromagnetic simulations which take into account mutual coupling effects between the array elements

Experimental two-layer adaptive phase-switched screen

An experimental two-layer planar phase-switched screen is described. The screen is designed to provide controlled phase modulation of electromagnetic energy reflected from its surface, and can be configured to synthesise the time-averaged reflectivity response of a microwave absorber. Measured results are presented to show that the experimental system exhibits dynamic reflectivity null steering capabilities over an 8 to 15 GHz frequency range.

Experimental HF circular array with direction finding and null steering capabilities

The paper describes an HF-circular-array receiving and direction finding system which also offers a capability for null steering. The experimental array consists of four wideband active loop antennas which feed a 4 × 4 Butler matrix. The action of the Butler matrix is to analyse the signals received by the array in terms of phase-mode components. Direction finding can then be carried out by measuring the phase difference between phase-mode outputs of the matrix, and either beam or null formation can be achieved by combining such phase modes with appropriate phase and amplitude weightings. The experimental system uses a microcomputer based adaptive technique for the bearing measurement. The advantage of this technique is that it employs a single unmodified HF receiver and it also offers a capability for null steering by means of software control of the receiving system.