Isosceles-Trapezoidal-Distribution Edge Tapered Array Antenna with Unequal Element Spacing for Solar Power Satellite

Abstract

The Earth will require sustainable electricity sources equivalent to 3 to 5 times the commercial power presently produced by 2050. Solar Power Satellite (SPS) is one option for meeting the huge future energy demand. SPS can send enormous amounts of power to the Earth as the form of microwave (MW). A highly efficient microwave power transmission (MPT) system is needed for SPS. A critical goal of SPS is to maintain highest Beam Efficiency (BE) because the microwaves from SPS will be converted to utility power unlike the MW from communication satellites. Another critical goal of SPS is to maintain Side Lobe Levels (SLL) as small as possible to reduce interference to other communication systems. One way to decrease SLL and increase BE is the edge tapering of a phased array antenna. However, tapering the excitation requires a technically complicated system. Another way of achieving minimum SLL is with randomly spaced element position but it does not guarantee higher BE and the determination of random element position is also a difficult task. Isosceles Trapezoidal Distribution (ITD) edge tapered antenna was studied for SPS as an optimization between full edge tapering and uniform amplitude distribution. The highest Beam Collection Efficiency (BCE) and lowest SLL (except maximum SLL) are possible to achieve in ITD edge tapering and ITD edge tapered antenna is technically better. The performance of ITD is further improved from the perspective of both Maximum Side Lobe Level (MSLL) and BE by using unequal spacing of the antenna elements. A remarkable reduction in MSLL is achieved with ITD edge tapering with Unequal element spacing (ITDU). BE was also highest in ITDU. Determination of unequal element position for ITDU is very easy. ITDU is a newer concept that is experimented for the first time. The merits of ITDU over ITD and Gaussian edge tapering are discussed.

Analytic design techniques for MPT antenna arrays

“…Moreover, they are not expected to provide high BW PSL BE performances because the thinning and the equally-weights. In order to improve the performances of ADS layouts for MPT, a computationally efficient approach based on the superposition of a tapering on the ADS layout (i.e., using a Gaussian distribution with edge tapering equal to ) [3] is considered. More specifically, the following weighting is used …”

“…Solar Power Satellites (SPS) represent one of the most interesting technological opportunities to provide large scale, environmentally clean and renewable energy to the Earth [1]- [3]. A fundamental and critical component of SPSs is the Microwave Power Transmission (MPT) system, which is responsible for the delivery of the collected solar power to the ground rectenna [2].…”

“…Towards this end, the MPT array must exhibit a narrow main beam width ( ), a high beam efficiency ( BW BE ), and a low peak sidelobe level ( ). Moreover, reduced realization costs and weights are also necessary [3]. To reach these contrasting goals, several design techniques have been investigated including random methods [4] and hybrid deterministic-random approaches [2] [3].…”

“…To reach these contrasting goals, several design techniques have been investigated including random methods [4] and hybrid deterministic-random approaches [2] [3]. On the contrary, well-established design tools based on stochastic optimizers [5][6] are difficult to be employed, due to their high computational costs when dealing with large arrays as those of interest in SPS [3].…”

Planar arrays synthesis for optimal wireless power transmission

“…However, the feeding network is complicated to fabricate and maintain, owing to its "smooth nature" of "quasi-Gaussian" distribution. To reduce the complexity of feeding network, edge tapering methods [9,10] were proposed. In these methods, the innermost elements of the array are fed with constant amplitudes, while a small number of edge elements need different amplitudes.…”