The mutual coupling between antenna elements affects the antenna parameters like terminal impedances, reflection coefficients and hence the antenna array performance in terms of radiation characteristics, output signal-to-interference noise ratio (SINR), and radar cross section (RCS). This coupling effect is also known to directly or indirectly influence the steady state and transient response, the resolution capability, interference rejection, and direction-of-arrival (DOA) estimation competence of the array. Researchers have proposed several techniques and designs for optimal performance of phased array in a given signal environment, counteracting the coupling effect. This paper presents a comprehensive review of the methods that model and mitigate the mutual coupling effect for different types of arrays. The parameters that get affected due to the presence of coupling thereby degrading the array performance are discussed. The techniques for optimization of the antenna characteristics in the presence of coupling are also included.

The estimation of RCS of a phased array depends on various parameters, namely, array geometry, operational frequency, feed network, mutual coupling between the antenna elements and so fourth. This paper presents the estimation of RCS of linear dipole array with series-feed network by tracing the signal path from the antenna aperture into the feed network. The effect of mutual coupling exhibited by the dipole antenna is considered for three configurations namely, side by side, collinear, and parallel in echelon. It is shown that the mutual coupling affects the antenna pattern (and hence RCS) significantly for larger scan angles. Further it is inferred that the RCS of phased array can be optimized by (i) reducing the length of the dipole, (ii) termination of the isolation port of the coupler with a suitable load, and (iii) using suitable amplitude distribution.

The scattering behavior of a phased array depends on its design parameters, feeding network, and the platform over which it is mounted. In this paper, the total scattered fi eld from an unequal-length dipole array is analyzed towards controlling the radar cross section (RCS) of the array. The mutual-coupling effect between the dipole elements is taken into account. The RCS of a non-skewed linear dipole array is analytically estimated by computing the signal refl ections at each level of the antenna system. The closed-form formulation for the RCS estimation of the dipole array is separately presented for both series and parallel feeding networks. An attempt has been made to explain the variations observed in the RCS patterns corresponding to different confi gurations of unequal length dipole arrays arbitrarily arranged. The effects on the array's RCS of optimizing the lengths of the dipoles and of other parameters are discussed. It is shown that the appropriate choice of the lengths of the dipoles can contribute towards the reduction of the array's RCS.

The current focus in defense arena is towards the stealth technology with an emphasis to control the radar cross-section (RCS). The scattering from the antennas mounted over the platform is of prime importance especially for a low-observable aerospace vehicle. This paper presents the analysis of the scattering cross section of a uniformly spaced linear dipole array. Two types of feed networks, that is, series and parallel feed networks, are considered. The total RCS of phased array with either kind of feed network is obtained by following the signal as it enters through the aperture and travels through the feed network. The RCS estimation of array is done including the mutual coupling effect between the dipole elements in three configurations, that is, side-by-side, collinear, and parallel-in-echelon. The results presented can be useful while designing a phased array with optimum performance towards low observability.

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