Grating lobe suppression in phased arrays composed of identical or similar subarrays
The grating lobe suppression methods for non-equidistant array antennas composed of identical or similar subarrays are proposed. Subarrays have equidistant rectangular or triangular grid. The grating lobes of an antenna array are reduced due to the irregular arrangement of subarrays. The following methods are considered: relative shift of neighbor subarrays, arranging gaps between subarrays, using different element spacing in different subarrays, rotation of subarrays, and combination of these methods. The methods provide suppression of the grating lobes from −2.6 dB to −11 dB as compared to equidistant arrays while side lobes envelop grows slightly.
Grating lobe suppression in rotationally tilec arrays
Uniform placement of array elements limits its maximum frequency due to the formation of grating lobes. While non-uniform element or subarray spacing have significantly lower grating lobes, it reduces aperture efficiency and leads to arrays that are difficult to design and manufacture. We propose a modular asymmetric convex-shaped subarray to construct the array by rotation and translation, filling the aperture without overlaps or gaps. This new approach can achieve lower grating lobes compared to uniform array geometries. It can also lower design, manufacturing and operation costs by offering interoperable subarrays and provide array size flexibility.
Monte Carlo simulations of magnetovolume instabilities in anti-Invar systems
We perform constant pressure Monte Carlo simulations of a spin-analogous model which describes coupled spatial and magnetic degrees of freedom on an fcc lattice. Our calculations qualitatively reproduce magnetovolume effects observed in some rare earth manganese compounds, especially in the anti-Invar material YMn2. These are a sudden collapse of the magnetic moment which is connected with a huge volume change, and a largely enhanced thermal expansion coefficient.