Wide Scanning Angle Millimetre Wave 1 × 4 Planar Antenna Array on InP at 300 GHz

The design of a uniformly spaced 1 × 4 linear antenna array using epitaxial layers of benzocyclobutene over an InP substrate is demonstrated. The array elements are conjugately matched with a uni-travelling carrier photodiode at the input. The phased array is optimised to counteract mutual coupling effects by introducing metal strips with isolated ground planes for each radiating element. The proposed antenna array can provide a gain of 10 dBi with a gain variation of ±3 dB. The array operates over a bandwidth of 10 GHz (295–305 GHz) with a wide scanning angle of 100° in the broadside.

Impedance matching of planar antenna array elements for terahertz rectenna.

The terahertz frequency band of electromagnetic radiation has many potential practical uses. However it still remains to be underdeveloped because of the difficulties with its generation and detection. Many modern studies suggest using rectennas (rectifying antennas) as a potential efficient terahertz detector. The application of rectennas in the terahertz band is challenging in its own way. In particular an efficient operation of a rectenna device requires applying high values of voltage to the rectifying element. This can be attempted by employing an antenna array. However the terahertz band is the band in which the effects of finite conductance of metals start becoming noticeable. This means that antennas in the array cannot be spaced too far away from each other. For a terahertz antenna one of the most popular kinds of structure is a planar antenna, placed on top of a dielectric layer with a metal reflector beneath it. Placing connecting wires in the same plane as the antenna array can minimize the length of the said wires. But it also leads to the structure becoming too complex to compute as the number of the antennas in the array increase. Placing the connections in a different plane, e.g. behind the reflector, can eliminate the influence of these connections on the antenna array characteristics. This study shows that this method also allows adding antennas to the array in a unified manner regardless of their amount. It is worth noting that using this way it is also possible to achieve a predictable behavior of the output impedance of the antenna array.

Optimal radar cross section estimation in synthetic aperture radar with planar antenna array

The optimization problem of statistical synthesis of the method for radar cross section estimation in synthetic aperture radar with planar antenna array is solved. The desired radar cross section is given as a statistical characteristic of a spatially inhomogeneous complex scattering coefficient of the studying media. In fact it is developed new methods of inverse problems solution not with respect to the restoration of coherent images in the form of spatial distribution of complex scattering coefficient but with respect to the statistical characteristics of inhomogeneous (spatially nonstationary) random processes. The electrophysical parameters of surfaces and their statistical characteristics are considered as functions of spatial coordinates. The maximum likelihood method was chosen as the optimization method. The obtained results make it possible to determine the multichannel structure, the optimal method of surface observation and the potential spatial resolution in aerospace scatterometric radars with antenna array. Optimal operations for processing space-time signals are determined and a modified method for synthesizing antenna aperture is proposed, which in contrast to the classical algorithm for synthesizing antenna aperture that integrates the product of the received signal and the reference signal equal to a single signal additionally implements the decorrelation of signals reflected from the earth's surface, The new operation of the scattered signals decorrelation consists in their integration with the space-time inverse correlation function. To confirm the reliability of the results obtained, simulation modeling of the classical method for the synthesis of coherent images and the proposed optimal one was carried out. From the analysis of the results it flows that propose method has higher quality and smaller size of spackle noise. The results obtained in the article can be used to develop and substantiate the requirements for the tactical and technical characteristics of promising aerospace-based scatterometric radars with planar phased antenna arrays.

Forming broaden dips in the directional pattern of an adaptive spatial filter with planar antenna array.

The adaptive antenna array beamforming is used to suppress jammers by placing antenna directional pattern nulls in the directions of the jammer sources. The performance of the beamformer is known to degrade in rapidly moving jammer environments. This degradation occurs due to the jammer motion that can bring the jammers out of the sharp nulls of the adaptive directional pattern. The directional pattern nulls broadening is an effective means to settle this problem. To broaden the nulls, the first derivative of the pattern in the directions of the jammer sources is set equal to zero. Being applied to the beamformer with a linear array, this technique allows producing broaden nulls in the directional pattern. However, in the case of a two-dimensional planar antenna array, the nulls will broaden only in one angular plane. In order to equally broaden the nulls in all angular directions and in this way to make them symmetrical, some additional constraints on the second partial derivatives of the directional pattern should be imposed. To set these constraints, it is necessary to include additional transformed steering vectors of jammers in the basis of the jammer subspace. These new transformed steering vectors are calculated in accordance with the expressions for the second partial derivatives of the directional pattern. In this paper, the expressions for the transformed steering vectors are derived and a novel beamforming algorithm based on them is proposed. In the adaptive beamforming algorithm based on such an approach unknown steering vectors of jammers are replaced by the eigenvectors of the sample covariance matrix corresponding to the largest eigenvalues. The effectiveness of the proposed method is verified by the computer simulation results. The computational complexity of this algorithm is estimated.