In this paper we present detailed design information and measured results of a Solar Power Satellite (SPS) power beaming array based on a 112-element cross-helix “CASSIOPeiA” Solar Power Satellite (SPS) concept, developed under the UK government DESNZ and UK space agency funded “CASSIE” research program. Designed for 2.4 GHz wireless power transmission (WPT), the array has a design goal of beaming 200 W/m2 power density over 6.5 m in an anechoic chamber, transmitting 672 W of RF power with 6 W per element. Experimental validation confirmed retrodirective beam tracking across a 360° azimuth range, with limited coverage also demonstrated in elevation. The array was comprised of 7 layers, each containing 16 elements. Power beaming tests used a 144 element rectenna, able to produce an accurate power density map across the 1m2 aperture, with a peak measured power density of 172 W/m2, reinforcing the feasibility of high-efficiency space-based solar power (SBSP), with accurate, real time, retrodirective tracking.

This paper outlines the theory behind helicoid antenna array beamforming and the practical validation on an 8 & times; 8 helicoid antenna array. Design, simulation, and measurement are presented at 2.45 GHz. A practical method for obtaining the phase steering weights required to perform beam pointing over 360 degrees is presented. A specialised dipole was also developed, achieving 4.9 dBi and low mutual coupling. It was also shown by analysis, simulation and measurement that this type of array, unlike a planar array, does not exhibit beam pointing error, making it highly attractive for retrodirective applications when precision beam pointing is required.

The localization of near-field sources is crucial in wireless communications. Practical arrays have mutual coupling between the elements of the array that can significantly affect the accuracy of localization algorithms. In this paper, we utilize a practical array to evaluate the performance of an iterative method based on oblique projection (IMOP) in estimating the location of near-field sources. The conventional two-dimensional (2D) search method for near-field source localization (TSMNSL) employs a 2D search to estimate the direction of arrival (DOA) and range of the source, resulting in a high computational load. In contrast, the IMOP method uses one-dimensional searches, which significantly reduces computational complexity. The results of numerical and full-wave electromagnetic simulations in this paper show that the performance of DOA and range estimations in the IMOP method is comparable to that in the TSMNSL method. The simulation results further indicate that the computational complexity of the IMOP method is at least 49 times lower than that of the TSMNSL method.

The issues associated with the constant growth in energy demand have led several countries to explore alternative solutions for the development of firm low-carbon energy sources. Space Based Solar Power is a promising system concept, with the potential of providing re-dispatchable clean energy directly from space. The concept is based on gathering energy in space through solar panels and sending it to Earth via a reconfigurable antenna array of millions of Watt-level amplifiers and antennas, operating at a frequency of around 2.496 GHz to form a narrow beam. Power density and losses associated with the electronics can be significant bottlenecks in the development of this technology, since the system needs to be light, compact and resilient to facilitate its deployment in space and prevent critical components failure over a long period of time. The design of a suitable power amplifier topology to drive the individual antenna elements is a critical step to facilitate the deployment of the system. In this paper we present a Class E power amplifier capable of delivering 5 W to a 50 Ohm load with a peak drain efficiency close to 80% for gains between 8 dB and 12 dB and a power density up to 0.63 W/cm(2).

In this paper we provide the test results of a 6-element, high power, phased array antenna used for radiative wireless power transmission. A retrodirective approach is used to target the power transmission in a desired direction. The frequency used for the power transmission is 2.496GHz which lies in the 2.4-2.5GHz ISM frequency band. We used a 6 element array of helical antennas to transmit the electromagnetic power. Retrodirective operation was practically validated for the 6 element array with total transmit power of 60W (10W per element) at up to 84% drain efficiency at the transmit power amplifiers. The tests have been carried out in the Queen’s University Belfast anechoic chamber at the Centre of Wireless Innovation (CWI).

The CASSIOPeiA Solar power satellite (SPS) helix antenna array concept has been shown to provide a viable concept with no mechanical rotational joints required between the photovoltaic cells and the antenna. The important feature of the CASSIOPeiA antenna is that it can provide 360 degrees azimuth electronic beam steering, pointing a highly directional beam, to a rectenna farm on earth. Modelling of the CASSIOPeiA antenna to date has only included setting up pre-defined phase/amplitude distributions across the array. These results are promising but to model the array for retrodirective operation, the phase distributions across the array need to be determined from phase conjugation of a received pilot tone. This mode of operation, to our knowledge, has never been theoretically validated within the triple dipole beam steering configuration of a large CASSIOPeiA array. In this paper we present the first simulated validation of a 10,000 unit cell (100 × 100) CASSIOPeiA array as a retrodirective antenna, providing a well-defined steerable main beam and good sidelobe suppression.

In this paper, single and cross helix array structures, for solar power satellite WPT applications, have been simulated, with full wave simulations up to 200x100 unit cell (H x W = 6m x 6m) array size. Near field simulations computed the WPT power densities at distances up to 500 m from the array. The results presented, are the first validation that a large cross helix structure can provide enhanced, 360 degree steerable, WPT beamforming capabilities compared to a similarly sized single helix. Previous work has only validated single helix structures. As an example, a 100x100 single helix array with 5W per element was shown to produce a WPT power density of 93 W/m 2 at 500m, whereas a 200x100 cross helix structure, with double the number of elements produced a power density of 315W/m 2 , which is an almost fourfold increase compared to the single helix. This clearly shows the increased aperture to be providing additional beamforming as well as the two times power increase from doubling the number of elements.

When using retrodirective antennas for wireless power transmission it is desirable to have a high-power transmitted signal which is sent back in the same direction as a weak pilot signal to the device being powered. A significant issue arises in the retrodirective WPT transmitter in how to efficiently separate the pilot signal from the transmitted WPT signal, especially when the same antenna is being used for transmit and receive. Traditionally, this is done using either circulators or duplexers, although these components can be bulky and expensive and introduce insertion loss into the transmit path, lowering the transmit power amplifier efficiency. In this article, we propose a new self-mixing PA method using the nonlinear characteristics of a power amplifier to allow a pilot tone signal to be extracted as a lower intermediate frequency (IF) signal with no transmit insertion loss and no requirement for circulators or duplexers. We also present a completely new PLL-based phase conjugating circuit that can extract the low-frequency pilot IF signal and provide a high-power phase conjugated drive signal to the self-mixing PA. The system is experimentally validated as a six-element retrodirective array for wireless power transmission application, where the power amplifier is shown to transmit more than 10 W with efficiencies up to 84%. The self-mixing PA was also confirmed to have very low mixing conversion loss with only 6 dB loss between the received pilot signal and the low frequency IF. We see this work as being essential for applications for retrodirective antennas for space solar satellite applications and other applications where transmission and reception by only a single antenna are required.

In this study we compare helix and patch array antenna characteristics for wireless power transfer (WPT). It will be shown that the helices offer higher link efficiency for a similar beam scanning limit compared to patch antenna elements. We provide 12-by-12 element planar array results for both cases at different element spacings. The frequency band of interest is ISM 2.4-2.5GHz and we do the comparisons in this range. It is concluded that helix elements, when used as an array, offer significant improvements for wireless power link efficiency, whilst also offering a reasonable beam scanning range.

In this paper, we study the input impedance characteristics of axial mode helical antennas to find an effective way for matching it to 50 Ω. The study is done on the important matching parameters such as like wire diameter and helix to the ground plane gap. It is intended that these parameters control the matching without detrimentally affecting the radiation pattern. Using transmission line theory, a simple broadband technique is proposed, which is applicable for perfect matching of antennas with similar design parameters. We provide design curves to help to choose the proper dimensions of the matching section based on the antenna’s unmatched input impedance. Finally, using the proposed technique, a 4-turn axial mode helix is designed at 2.5 GHz center frequency and the measurement results of the manufactured antenna will be included. This parametric study gives a good insight into the input impedance characteristics of axial mode helical antennas and the proposed impedance matching approach provides a simple, useful method for matching these types of antennas.

In this paper, a compact four-layer offset-beam X-band triangular grid microstrip array antenna with proximity coupled feed patch element is presented. The feed network is in the lower substrate and the radiation elements are in the upper substrate of the array antenna structure, which is isolated by the ground plane in the middle substrate. The feed network is in parallel planar format and utilizes a 1x4 phase shifter power divider to realize a progressive phase shift needed to control the beam direction. The isolation of the feed network from patch elements reduces cross-polarization and side-lobe-levels (SLLs). The patch antenna elements are excited by proximity coupling which increases bandwidth, flexibility in the impedance matching, and simplicity of fabrication also reduces spurious response. A triangular arrangement is used to reduce mutual coupling and to limit the grating lobes. Moreover, a 4x4 element array antenna with a fixed scan angle at 30° is designed with 1 GHz impedance bandwidth with a center frequency of 9.5 GHz, peak gain of 15.1 dBi, and side lobe level (SLL) less than -10 dB in principle planes. Besides, the proposed power supply network structure enables easy PIN and varactor diode phase shifters, which can be used to improve antenna performance by providing reconfigurable and tunable scanning.

This paper proposes a low-side lobe lightweight array antenna for X-band applications with center frequency of 9.5 GHz. The proposed array antenna, being composed of 144 (12 x 12) single antenna elements, is designed in a three-layer configuration with total size of the 30 cm x 30 cm. Technically speaking, it is composed of two substrates and three conductive layers on the top, bottom, and between the substrate layers. The main part of the feeding network is located on the bottom side of the antenna structure while the radiating patches are printed on the top side. The ground plane is placed in the middle layer between the two substrates. Isolation of the feed network from the radiating patches, which is realized by the embedded ground plane, yields cross-polarization and side lobe levels (SLLs) reduction. Besides, the feeding system excites the top side patches by connecting to them through vias. Moreover, 1-6 power dividers in the feeding system are connected to each other to form the complete 144-element array configuration. Adopting this technique provides easy development of a planar 2n x 2n element array antenna. To achieve low side lobes, the Dolph-Chebyshev amplitude taper coefficients are used in the design process. (C) 2018 Elsevier GmbH. All rights reserved.

In this paper, a novel frequency reconfigurable monopole antenna with five switchable states including an ultrawideband (UWB) state, three single band states and a dualband state is presented. The frequency reconfigurable capability of the antenna is achieved by using a switchable slotted structure on the ground plane. The antenna which supports most applicable frequency bands above 2 GHz can be used in multi-radio wireless systems. Reflection coefficient and radiation pattern measurements were performed for the fabricated antenna. Good agreement between simulated and measured results was obtained.

A microstrip-fed printed monopole antenna having band-notch characteristics is proposed. The fullband antenna introduces 2.5-10.6GHz bandwidth covering the FCC frequency band for UWB applications. Six inverted L-shaped stubs on the bottom of the substrate, which are connected to the radiating patch through via pins, are used to create flexible multi-band filtering function. Using this technique it is possible to reject one to six different frequency bands.

In this paper a simple rectangular monopole antenna with variable band-notched function is proposed. The antenna is constructed on a FR4-epoxy substrate by thickness of 1.6mm and εr=4.4. The proposed antenna shows Ultra-Wideband (UWB) characteristics from around 3 up to 10.6GHz for VSWR<; 2. Two shorting pins running through the substrate connect the patch to the inverted L-shaped stubs printed on the bottom of the substrate to create multi-filtering function. By changing the stubs' lengths the proposed antenna shows variable single and double filtering characteristics.

In this letter, a simple rectangular monopole antenna with variable band-notched function is proposed. The antenna is constructed on an FR4-epoxy substrate with thickness of 1.6 mm and εr = 4.4. The proposed antenna shows ultrawideband (UWB) characteristics from around 3 up to 10.6 GHz for . Two shorting pins running through the substrate connect the patch to the inverted L-shaped stubs printed on the bottom of the substrate to create multifiltering function. By changing the stubs' lengths, the proposed antenna shows variable single- and double-filtering characteristics.

In the present work, the effect of a central electrical impurity (dipole) on quantum conductance in simple cubic nano-wires (SCNW) has been investigated in the tight-binding (TB) approach and assuming nearest-neighbor interaction by Green's function (GF) method. We illustrate that in the presence of electrical impurity (external potential), the number of channels and energy band of nano-wire decrease. The variation of the energy band and the number of channels depend on the position and amount of the electrical charge (dipole moment) in the SCNW.