No abstract

An extended-feature, system-driven convex algorithm for the synthesis of uniform-amplitude, irregular planar phased arrays with simultaneous multi-beam optimization for mm-wave 5G base station applications in multiuser scenarios is presented. The inter-user interferences are suppressed by minimizing the maximum side lobe level (SLL) for a beam scanned freely inside a given sector. The aperture size is restricted to the size of the heatsink baseplate dimensions. A minimum guaranteed inter-element spacing in the final layout is predefined, which prevents element overlapping, eases the thermal problem and helps reduce the effects of high mutual coupling. The algorithm performance is tested via the synthesis of a 64element integrated array with at least half a wavelength interelement spacing. The optimized array results show that, compared to their regular counterparts, significant reduction in the SLLs is achieved for a beam scanned inside the defined sector, while keeping the maximum temperature of the array at a reliable level. The effect of mutual coupling on the results is also investigated via full-wave simulations and it is explained how embedded element patterns can potentially be included in the optimization. Superior capabilities of the proposed method are illustrated by comparing the algorithm output to those reported in the state-of-the-art literature.

Utilization of phase-coded waveforms in automotive MIMO radars for short to medium range applications is studied. Performances of three most-promising binary code families (Gold, APAS and ZCZ sequences) are compared. Design tradeoffs of practical implementation of phased-coded waveforms for MIMO radar are analyzed for the first time for a possible future System on Chip implementation. Orthogonality of the waveforms in case of moving targets is analyzed. The implications of the code properties for the Range-Doppler map, as well as the Range-Angular map, are pointed out. Doppler frequency shift impact on such performance indicators as the target peak power and range sidelobe levels in the range-Doppler plane, as well as the range and azimuth sidelobe behavior, and the angular error in the azimuthal plane have been comprehensively studied for the first time. It is shown that the time-staggered transmit scheme with autocorrelation properties only (while introducing azimuthal errors) results in improved performance compared to code division multiplexing with auto-and cross-correlation properties.

Abstract-In this paper, the influence of a lossy ground on the input impedance of dipole and bow-tie antennas excited by a short pulse is investigated. It is shown that the ground influence on the input impedance of transient dipole and bow-tie antennas is significant only for elevations smaller than 1 5 of the wavelength that corresponds to the central frequency of the exciting pulse. Furthermore, a principal difference between the input impedance due to traveling-wave and standing-wave current distributions is pointed out.

Optimization of heat source distribution in two dimensional heat conduction for electronic cooling problem is considered. Convex optimization is applied to this problem for the first time by reformulating the objective function and the non-convex constraints. Mathematical analysis is performed to describe the heat source equation and the combinatorial optimization problem. A sparsity based convex optimization technique is used to solve the problem approximately. The performance of the algorithm is tested by several cases with various boundary conditions and the results are compared with a uniformly distributed layout. These results indicate that through proper selection of the number of grid cells for placing the heat sources and a minimum inter-source spacing, the maximum temperature and temperature nonuniformity in the domain can be significantly reduced. To further assess the capabilities of the method, comparisons to the results available in the literature are also performed. Compared to the existing heat source layout optimization methods, the proposed algorithm can be implemented more easily using available convex programming tools and reduces the number of input control parameters and thus computation time and resources while achieving a similar or better cooling performance.