Design of Beamforming Network with Flat-Topped Radiation Patterns

We present a novel printed dual-layer three-way directional coupler, which can be utilized as 3 $\,\times\,$ 3 beamforming network (BFN) to provide orthogonal three-beam switching capability. The three-way directional coupler is a passive component with six input/output ports. The signal injected into the input port is equally distributed into the three output ports, with a constant phase difference of $-$ 120 $^{\circ}$ , 0 $^{\circ}$ , or $+$ 120 $^{\circ}$ . Simulation and measurement results show that within 7% relative bandwidth, good matching, high isolation, equal power division, and constant phase difference have been achieved simultaneously. Utilizing the three-way directional coupler as a 3 $\,\times\,$ 3 BFN, an orthogonal three-beam antenna array for 5.8-GHz application has been designed, fabricated, and tested to verify its capability experimentally.

A novel network is proposed for feeding planar overlapped subarrays with contour flat-topped radiation patterns in modular phased array antennas designed for beam scanning in a limited region of observation. The network comprices one-by-seven power dividers, directional couplers connecting the nearest output ports of adjacent dividers in pairs, blocks with pairs of looped circuits involving directional couplers, and seven-element blocks of radiators. The proposed network allows forming planar overlapped subarrays of seven blocks of radiators. Complex amplitudes of the excitation of the subarray radiators derived from the parameters of the network are determined by two parameters corresponding to the directional couplers connecting the nearest modules and directional couplers standing in the looped circuits. Optimization of the indicated parameters is carried out and some results calculated for the subarray factor characterizing capabilities of the proposed network in shaping the contour flat-topped subarray radiation pattern are presented and discussed.

One of the approaches to the design of phased array antennas (PAA) for beam scanning in a limited region of space is associated with formation of overlapped subarrays with flat-topped radiation patterns of width equal to the width of the scan region. Unlike linear subarrays, for which there exist many technical solutions, planar overlapped subarrays can be formed by two ways. One of them is based on cascade connection of linear subarrays arranged perpendicularly to each other. Another way is based on use of beamforming networks. Since the problems concerning synthesis of overlapped subarrays with flat-topped patterns in planar PAA is not yet sufficiently considered in the literature, the indicated problem remains of interest. The work considers two methods of synthesis of planar overlapped subarrays with flat-topped radiation patterns. One method is a conventional method based on Fourier transform of the required radiation pattern. Another method introduced in the paper is new one. It allows determination of amplitude distribution over subarray aperture with providing maximum level of the subarray factor in the broadside direction and with taking into account power balance distributed over the subarray radiating elements. The proposed method is compared with the conventional method based on the Fourier transform, and advantages of the former method over the latter one are shown. The paper contains results obtained for amplitude distributions for a few cases of subarray excitation and appropriate subarray factors characterizing the capabilities of the new method. The method proposed in the paper can be applied in the further studies concerning development of networks for feeding overlapped subarrays in planar limited-scan PAA of modular construction.

In this article, a multimode composite right/ left-handed (CRLH) substrate-integrated waveguide (SIW) transmission line technology is proposed, which aims to broaden the operating bandwidth of the multiport directional couplers (DCs) and solve the oversize of the beamforming network (BFN). Its core is to etch multiple interdigital slots (IDSs) on the conductor surface of the multimode SIW transmission line, which can control the electromagnetic fields of different modes in the transmission line under the condition of less electromagnetic energy leakage. By adjusting the position and size of the IDSs, the desired phase constants and electromagnetic field distributions of different modes can be obtained simultaneously. Based on the proposed multimode CRLH SIW transmission line, the six-port, the eight-port, and the ten-port DCs are designed, respectively. Compared with the traditional multiport DCs based on the SIW, the bandwidth of the proposed six-port and eight-port DCs is broadened by about 87.3%. Based on the proposed multiport DCs, the miniaturized BFNs and the miniaturized multibeam array antennas (MBAs) can be realized by adding appropriate fixed phase shift. Finally, to verify the feasibility of applying multiport DCs based on the multimode CRLH SIW transmission lines to the miniaturized BFNs and the miniaturized MBAs, a 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 3 BFN, a 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 4 BFN, and a three-port MBA are fabricated, measured, and discussed. Their sizes are reduced by 58%, 49%, and 60%, respectively, compared with their SIW butler matrix (BM) counterparts.

Chapter 7 - Directional Couplers

A planar millimeter-wave 2-D beam-scanning multibeam array antenna fed by compact 16-way beamforming network (BFN) in multilayered substrate integrated waveguide (SIW) technology is addressed. The BFN is formed by connecting two stacks of sub-BFNs, the E-plane sub-BFN and the H-plane sub-BFN. The H-plane sub-BFN is realized by a traditional H-plane 4 x 4 Butler matrix (BM). The key point of this design is to propose an E-plane 4 x 4 BM which realizes a planar E-plane sub-BFN. These two sets of sub-BFNs can joint directly without resorting to any connectors or connecting networks to form such a compact 16-way BFN with a reduced area of merely 3λ x 12λ. After that, to be compatible with the proposed BFN, a ladder-type 4 x 4 slot antenna array is employed, which is comprised of four linear 1 x 4 slot antenna arrays. Different from traditional array, the four subarrays are distributed in separate layers for the purpose of jointing to the BFN more conveniently. Transition network are also required to connect the BFN with the antenna array. Finally, a compact 2-D scanning multibeam array antenna based on the planar SIW BFN are fabricated and measured, which would be an attractive candidate for 5G application.

This paper presents design methods of tri-beam antenna systems. To produce a forward beam along antenna normal axis, 3×3 Butler matrix network with three directional couplers and four −90 degree phase shifters is proposed. When different input ports are excited, the proposed structure can produce three output signals with equal amplitude and the phase differences of −120 degree, 120 degree and 0 degree, respectively. For verifying the design concept, a tri-beam antenna system based on microstrip structure at 2GHz is proposed. The results indicate that the antenna array can produce −30 degree, 30 degree and 0 degree beam when different input ports are excited. A tri-beam slot antenna array based on substrate integrated waveguide (SIW) operating at 10GHz is designed and realized. The antenna array can produce tri-beam radiation performance with peak directions of −45 degree, 45 degree and 0 degree respectively.

In this paper, we purpose a novel approach to analyze exact cell loss probability of Shared Buffer ATM switch. In a N X N ATM switch whose input ports and output ports share one buffer, the number of arriving cells from input ports at one time slot is less than or equal to N. If these cells were destined to n output ports, no cells will be destined to the remaining N-n output ports. In the extremism, all arriving cells were destined to one output port, no cell will be destined to the other N-1 output ports. So, the arriving cells at each time slot from the input ports are destined to the output ports correlatively, but not independently. For this reason, the analyzing result on the assumption that all output cell queues are independent one another is larger than actual result. We complete our analysis by three steps. First, considering the case that there are cells arriving from input ports but not cells remove from output ports, we can get one-step state transition probability matrix P<SUB>a</SUB>; Second, considering the case that there are cells removing from output ports but not cells arrive from input ports, we can get one-step state transition probability matrix Ps; Third, considering arrival process and service process are independent, the accurate one-step state transition probability matrix P of cell's number in the buffer is derived, and then cell queue length steady probability distribution can be found. We can compute the accurate buffer capacity below certain cell loss probability. Computer simulation proves that the approach is efficient and exact.

Multi-core fiber (MCF) has been one of the main innovations in fiber optics in the last decade. Reported work on MCF has been focused on increasing the transmission capacity of optical communication links by exploiting space-division multiplexing. Additionally, MCF presents a strong potential in optical beamforming networks. The use of MCF can increase the compactness of the broadband antenna array controller. This is of utmost importance in platforms where size and weight are critical parameters such as communications satellites and airplanes. Here, an optical beamforming architecture that exploits the space-division capacity of MCF to implement compact optical beamforming networks is proposed, being a new application field for MCF. The experimental demonstration of this system using a 4-core MCF that controls a four-element antenna array is reported. An analysis of the impact of MCF on the performance of antenna arrays is presented. The analysis indicates that the main limitation comes from the relatively high insertion loss in the MCF fan-in and fan-out devices, which leads to angle dependent losses which can be mitigated by using fixed optical attenuators or a photonic lantern to reduce MCF insertion loss. The crosstalk requirements are also experimentally evaluated for the proposed MCF-based architecture. The potential signal impairment in the beamforming network is analytically evaluated, being of special importance when MCF with a large number of cores is considered. Finally, the optimization of the proposed MCF-based beamforming network is addressed targeting the scalability to large arrays.

The flat-top radiation pattern is necessary to form an appropriate beam in a sectored cellular network and to pro vide users with best quality services. The flat-top pattern offers sufficient power and allows to minimize spillover of signal to adjacent sectors. The flat-top sector beam pattern is relied upon In sectored cellular networks, in multiple-input multiple-output (MIMO) systems and ensures a nearly constant gain in the desired cellular sector. This paper presents a comparison of such optimization techniques as real-coded genetic algorithm (RGA) and particle swarm optimization (PSO), used in cellular networks in order to achieve optimum flat-top sector patterns. The individual parameters of flat-top sector beams, such as cellular coverage, ripples in the flat-top beam, spillover of radiation to the adjacent sectors and side lobe level (SLL) are investigated through optimization performed for 40◦ and 60◦ sectors. These parameters are used to compare the performance of the optimized RGA and PSO algorithms. Overall, PSO outperforms the RGA algorithm.

This paper presents a model that can be easily used to resolve the energy hub operation problem. The proposed model considers the uncertainty in the input and output ports. The energy hub optimum operation problem needs to be resolved in order to supply several energy loads in combination at the minimum total energy cost. In this study, mixed-integer linear programming was applied to formulate this optimization problem. The power balance, energy storage, and converter limitations of the input and output ports were included as equality and inequality constraints. The total cost of an energy hub was determined by the price of energy carriers. Eventually, deterministic and stochastic versions of the proposed model were tested in a case study. In the test system, electricity, gas, and wind generation were used in the input port, and the output port contained the electrical and thermal load. The results demonstrated that a stochastic model based on different scenarios was more realistic than a deterministic model. However, the total operating cost of an energy hub decreased more in the stochastic model compared to the deterministic model.

Spatial division represents a popular approach to increasing capacity in modern wireless networks. This paper presents a study of a simplified beamforming network based on a Fourier transform network with the number of output ports lower than the number of the elements in the antenna array. It is shown that connecting the output ports of Fourier transform network via power dividers to several array elements in phase, thus implementing a nearest-neighbor phase interpolation, preserves the gain and width of the beams in a narrow scanning sector. Therefore, in applications where few orthogonal beams are required to span a narrow spatial sector, the proposed approach can offer reduction of the hardware complexity. The simulated radiation patterns for a phase interpolation Fourier beamforming network are demonstrated. The antenna radiation patterns have been measured, using a Fourier Rotman lens with 2-way Wilkinson power dividers, which confirmed the simulated trends.

A formulation for design of continuous, hinge-free compliant mechanisms is developed and examined within a continuum structural topology optimization framework. The formulation makes use of two distinctly different sets of springs, the first of which are artificial springs of relatively large stiffness attached to the input and output ports of the mechanism model, and the second of which are springs attached only to the output port with smaller stiffnesses that represent the resistance of the workpiece as it is manipulated by the mechanism. The proposed formulation involves solving two nested optimization problems. In the inner problem the arrangement of a constrained amount of structural material is optimized to maximize the mechanism's mutual potential energy in response to a force loading at the input port while working against the stiff artificial springs on the input and output ports. As the relative stiffness of the artificial springs increases, the material continuity of the mechanism also increases to the point where de facto ‘hinge’ regions are eliminated. In the outer problem, the artificial springs are removed and one solves for an appropriate amount of structural material that yields the desired finite deformation compliance characteristics of the mechanism when working against the real workpiece resistance. Different aspects of the proposed formulation are demonstrated on a number of examples and discussed. Copyright © 2004 John Wiley & Sons, Ltd.

In this paper, the performance analysis on hybrid plasmonic waveguide (HPW)-based symmetrical directional coupler (DC) is proposed, which contains two parallel arms. In this analysis, one HPW arm performs as an input port and bar (parallel) output port; another HPW arm doings as a cross output port. The principle of DC is satisfied by the coupling of transverse magnetic field (TM) from the bar port to cross port. In the proposed DC, the mode characteristic parameters such as normalized mode area and propagation length are calculated by finite element method (FEM), and performance of the device is analyzed by certain parameters such as propagation loss, cross-talk, insertion loss, and coupling ratio. Hence, the proposed DC is designed with low cross-talk, low insertion loss, low propagation loss, and high propagation length, which could be appropriate for ultra-dense photonic integrated circuits (PICs).KeywordsOptical waveguidesDirectional couplerFinite element method

본 논문에서는 기판 집적 도파관(Substrate Integrated Waveguide: SIW) 기술을 이용한 위성통신용 전력 분배기를 제안하였다. 출력 구형 도파관의 크기를 변화시키지 않고, 가이딩 포스트의 위치를 조절하여 등분 비등분의 전력 분배 비율을 조절하였다. 또한, 방사형 도파관의 기본적인 특성과 입력부, 전력 분배의 과정을 자세히 설명하였다. 방사형 도파관의 신호 여기 방법으로 전류 프로브를 사용하여 동축 케이블로 구현하였으며, 출력부는 마이크로스트립 선로를 천이 구조를 이용하여 SMA 커넥터를 이용하였다. 설계된 4분기 전력 분배기는 등분/비등분으로 동작할 수 있으며, 설계 결과를 시뮬레이션과 제작으로 검증하였다. 등분/비등분 전력 분배기의 측정된 결과는 VSWR 2:1을 기준 대역특이 약 2.1 GHz와 3 GHz이다. Equal/unequal 4-way power divider suitable for satellite communication using SIW technology is presented in this paper. The control of positions of guiding posts provides equal or unequal power division ratios by maintaining the width of the SIW unchanged. In addition, the detailed descriptions for the proposed power divider include the general characteristics of radial waveguide, feeding part using coaxial cable, simple SIW structure, power-guiding posts, and transition for measurement. The comparison between the simulated and measured data shows a good agreement at a center frequency of 10 GHz. The measured input impedance bandwidths for equal and unequal power divisions are about 2.1 GHz and 3 GHz under the condition of less than VSWR 2:1, respectively.