Narrowband Antenna Array Research Articles

Spectral self-coherence restoral: a new approach to blind adaptive signal extraction using antenna arrays

A new approach to blind adaptive signal extraction using narrowband antenna arrays is presented. The approach has the capability to extract communication signals from cochannel interference environments using only known spectral correlation properties of those signals, i.e. without using knowledge of the content or direction of arrival of the transmitted signal, or the array manifold or background noise covariance of the receiver, to train the antenna array. The class of spectral self-coherence restoral (SCORE) objective functions is introduced, and algorithms for adapting antenna arrays to optimize these objective functions are developed. Using the theory of spectral correlation, it is shown by analysis and simulation that these algorithms maximize the signal-to-interference-and-noise ratio at the output of the narrowband antenna array when a single communication signal with spectral self-coherence at a known value of frequency separation, along with an arbitrary number of interferers without spectral self-coherence at that frequency separation, are impinging on the array.

Generalised approach to the design of narrowband antenna array processors with broadband capability

A few techniques have been proposed for designing narrowband antenna array processors with a specific broadband capability. In one approach the array processor is designed by imposing on it a set of linear constraints. This set consists of two parts. In the first part, the processor is constrained to have unity gain in the desired look direction at the centre frequency of the frequency band of interest. In the second part, an additional set of linear constraints is used to ensure that the gradient (first-order derivative) of the frequency response of the processor can be approximated to zero, in the minimum meansquare sense, over a specific frequency band. In the paper, it is shown that this approach can be extended to higher orders (n orders) so that other (n−1) sets of new linear constraints can be obtained. With the extended higher order constraints, a generalised formulation is arrived at for this class of constraints. Computer simulation results are given to show the performance characteristics of a higher order processor using linear array geometry.

A unified approach to the design of robust narrow-band antenna array processors

A unified approach to the design of robust narrowband antenna array processors is presented. The approach is based on the idea of minimizing the weighted mean-square-deviation between the desired response and the response of the processor over variations in parameters. Three specific examples of robust design are considered: robustness against directional mismatch, robustness against array geometry errors, and robustness against channel phase errors. Initially, a general quadratic constraint on the weights is developed. However, it is then shown that the quadratic constraint can be replaced by linear constraints or at most linear constraints plus norm constraint. These latter constraints are no more complex than those required for designs which do not incorporate robustness features explicitly. Numerical results show that the proposed approach appears to offer a unified treatment for directly designing narrowband processors which are robust against various types of errors and mismatches between signal model and actual scenario.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An alternative approach for designing narrowband antenna array processors with broadband capability

An alternative approach to the design of narrowband antenna array processors with a specific broadband capability is presented. The approach consists of two parts. In the first part, the processor is constrained to have a unity gain in the desired look direction at the centre frequency of the frequency band of interest. In the second part, an additional set of linear constraints are used to ensure that the gradient of the response of the processor can be approximated to have a zero slope, in the minimum mean-square sense, over the frequency band of interest. Computer simulation results show that the approach is very effective for designing narrowband array processors with broadband capability. The basic approach can also be used to design broadband antenna array processors without the need of presteering time delays.