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In this research study, a metamaterial (MTM) based $1\times4$ linear antenna array is designed with an integrated butler matrix (BM) beamforming network (BFN) to execute the switched-beam antenna array (SAA) operation, which can be employed for sub-6 GHz 5G applications. The proposed SAA is designed and simulated using CST microwave studio and then fabricated using FR4 epoxy glass substrate with the thickness ( $h$ ) = 1.6mm and dielectric constant ( $\varepsilon _{r}$ ) = 4.3. The MTM-BM BFN has shown excellent performance in both simulated and measured results, having return-loss of below 14 dB and insertion-loss at ports 5–8 to be 7 ± 2dB between the frequency range of 3.2-3.75GHz, respectively. Moreover, the phase difference between the output ports of the BM is simulated and measured. The $0.5\lambda $ spaced complementary split-ring resonator (CSRR) based antenna array integrated with MTM-BM BFN achieved a measured gain of 4.8-6.1 dB when each input port of BM was excited. The SAA analysis has been performed to identify the variation of gain and grating lobes; the distance between MTM antennas was altered by $0.3\lambda $ , $0.5\lambda $ , and $0.7\lambda $ , respectively. Depending on the BM input ports excitation, the main beam of the SAA is steered in four different directions −40°, −15°, +15°, and +45°, respectively. These radiation pattern studies have shown that the MTM-BM connected with four linear MTM antennas has successfully generated four beams in four different directions, which can be utilized for 5G applications to improve the channel capacity and enhance the transmission quality.

Current wireless communications urgently need to provide huge data rates, high gain and high directivity radiation pattern beams. Therefore, beamforming networks (BFNs) are introduced to provide these needs. Butler matrix (BM) is a type of beamforming network, which can be realized using fixed network circuits and feeds the antenna array. BM at high frequency suffers from components loss and phase error for massive network, especially when it is implemented using common microstrip structures. Different transmission lines such as waveguide and substrate integrated waveguide (SIW) are studied and introduced to realize Butler matrix. SIW structures are good candidate for the implementation of BM due to its property of low loss transmission line which comprises of properties of microstrip and waveguide technology. However, SIW antennas and structures at millimeter waves have unwanted radiation loss coming from the vias holes. In addition, the vias separation distance is dependent on waveguide size, which leads to a more massive beamforming network at 26-GHz. Hence, this thesis is proposing a more size-friendly and optimal SIW antenna beamforming structure to reduce the vias loss and provides higher bandwidth and gain at 26 GHz. The BM components such as 3 dB coupler, 0 dB crossover, and 45-degree phase shifter are designed by implementing metallic vias determination method. Size and distance of vias are the most important factors in determining the coupling ratio and phase shifts at output ports. Hence, the coupler is designed with different vias width and distance to obtain the correct phase and coupling at output ports. Then, the designed coupler is cascaded to form a 0-dB crossover. The phase shifter is designed with alerting vias distance inside the coupling area of SIW structure. The last component in beamforming is the design of SIW slot antenna based on longitude slot distributions. All the components are integrated to form a $4\times4$ BM with four slot antennas attached to BM networks. Microtrip separation feedline used to for coupler, crossover, BM and BFN. The proposed designs are simulated using CST software and fabricated by PCB LPKF ProtoMat printer. The outcomes of wide bandwidth with more than 1-GHz and high directive gain of more than 10-dB for the beamforming network are achieved. The output power of the BM is between −6-dB to −8-dB at all four ports with phase difference error less than 5°. Four directive beams are achieved at beam scanning of −14°, −41°, 40°, and −14° at port 1 to port 4 respectively. Hence, this $4\times4$ -BM with four slot antenna theses have introduced a successful design of an antenna beamforming network based on SIW technology with significant characteristics at 26-GHz.

In this article, a new approach to designing 6 $\times $ 6 beamforming networks (BFNs) for producing five or six beams is presented. The configuration of the 6 $\times $ 6 BFNs is designed utilizing planar wideband hybrid couplers and phase shifters. A new type of wideband hybrid coupler is built based on a slotline resonator and microstrip-to-slotline transitions. The proposed coupler design can achieve high level of isolation between the sum and difference ports. Two different formats of wideband 6 $\times $ 6 BFNs are then developed, to generate five and six beams, respectively. A prototype is fabricated and tested, and the experimental results agree with the simulation ones very well, achieving a wide operating bandwidth of more than 30%. Finally, the BFN is verified by feeding a six-element array, and the realized patterns match the predicted ones very well, demonstrating the function of the BFN. The topology of an extended 12 $\times12$ BFN is also given to demonstrate the possibility of creating higher-order BFNs using the presented approach. [ABSTRACT FROM AUTHOR]

In this letter, a wideband two-dimensional (2-D) scanning multibeam array antenna is proposed using a novel beamforming network (BFN). First, a novel three-beam Butler matrix (BM) network, as the core of the BFN, is proposed and described. The BM network comprises a directional coupler, T-shaped power dividers, and coupling baluns, which avoids using crossovers and lossy lumped elements as in a conventional BM network. In addition, a dual-stripline structure is employed to combine multiple components, which considerably reduces the BM network aperture. Then, six three-beam BMs are stacked and interconnected to form a complete 2-D BFN, whose scanning features of two orthogonal planes are controlled by two sets of BMs. Finally, to verify the working principle of the BFN, a 3 × 3 all-metal antenna array is designed and combined with the BFN. Notably, the low-profile antenna element achieves a wide operating bandwidth of 34.5%. Furthermore, a prototype is fabricated and tested, which shows that the antenna realizes switched beams in nine directions, indicating that an excellent 2-D scanning function is realized. [ABSTRACT FROM AUTHOR]

This article presents a novel 4×8 SIW Butler matrix (BM) with sidelobe level (SLL) suppression. The BM operates at 60 GHz and is implemented with a new design to achieve a compact size, which would be attractive for future mmWave wireless systems. This beamforming network uses straight SIW phase shifters with two apertures or two metal posts to pursue a smaller circuit area than with curved line phase shifters. Using a stepwise procedure and analyzing the design equations, the crossover and other components of the BM are also designed and optimized. The reflection and isolation coefficients are lower than -10 dB for all input ports and insertion loss magnitude imbalance is below 2.4 dB within the band from 57 GHz to 67 GHz. The slot array antenna fed by the BM shows an SLL lower than -21 dB for inputs 1 and 4 and lower than -14.5 dB for inputs 2 and 3 and provides beam switching.

Due to the rapid development of wireless communication technologies, the number of wireless users are radically increasing. Currently, ~23 billion wireless devices are connected to the internet, and these numbers are expected to increase manifolds in the years to come. The technology growth of the fifth-generation (5G) wireless systems will be needed to meet this high demand of the network. 5G wireless systems offer data-rates of up to 10Gbps, 1-ms latency, and reduced power consumption. It is a known fact that 5G wireless systems will be exploiting beyond the presently used 3 GHz microwave and millimetre-wave (mm-wave) frequency bands. This is the primary driver in the development of the 5G wireless system. Multi-beam Phased array antenna (PAA) systems are typically used in the deployment of 5G systems for high-gain and directionality. In current 5G and future Beyond 5G (B5G) antenna array systems, beamforming networks (BFNs) such as the Butler Matrix (BM) will play a key role in achieving multi-beam characteristics. So, this paper presents an extensive review of the BM based BFNs, and discusses which type of BM will be suitable for the phased array antenna (PAA) systems in the upcoming 5G and next-generation of B5G wireless systems. Moreover, this paper also summarizes the different types of BM designs based on the number of layers. The BMs are classified into the bi-layer, tri-layer, and four-layer structures. It includes different techniques that have been used to solve the problem of crossing, narrow bandwidth, and size reduction of the BM. From the previous studies, it is found that most of the past research work was performed using the bi-layer BM system, whereas the difficult geometries like tri- and four-layer BM are avoided due to their complex fabrication process. It is also found in this paper that the metamaterial (MTM) based bi-layer BM achieves low insertion-loss and phase-error, excellent bandwidth and compact size, and good S-parameter performance, which makes them an ideal BFN candidate for the upcoming 5G and next-generation B5G systems.

This paper introduces a novel family of one-dimensional switching matrices, also known as beamforming networks (BFNs), which can be sized for an arbitrary number of beams. It also describes the associated numerical design method, supported by several design examples. The concept is further validated with a full-wave model of a generic 5 × 5 switching matrix designed at 76 GHz. The proposed matrices are obtained by cascading units consisting of a two-way coupler and a phase shifter in a parallel configuration, providing theoretically lossless operation as a direct consequence of the orthogonal BFN topology and equalized path lengths, expected to benefit the frequency bandwidth. The design method is general, also including the configurations equivalent to Butler matrices when the number of beams is a power of two. The obtained planar matrix designs combine some benefits of the well-known Butler and Nolen matrices, namely the parallel topology and the arbitrary number of beams. The minimum number of cascaded units required by the proposed topology, also corresponding to the number of layers, is found to be $N$, where $N$ is the number of beams, which is less than the number of cascaded units for the corresponding “parallel” Nolen matrix, for $N$ larger than three, thus providing a reduction in the number of layers of up to 38% for an 8-beam matrix. This reduction is close to the theoretical upper boundary of 50%, reached for large values of $N$. This significant reduction is expected to have a positive impact on RF performance, and in particular insertion losses, as well as amplitude and phase dispersion over the operating band. Interestingly, the proposed switching matrix configuration reduces to a standard Butler matrix when the number of beams is equal to 4, and demonstrates a reduction in the number of layers of 20% over the corresponding planar Butler matrix for a design with 8 beams. The proposed matrix configuration is a promising solution for the design of low-cost single-layer beam-switching matrices.

A wideband monostatic simultaneous transmit and receive (STAR) antenna subsystem with high isolation and Co-horizontally polarized (Co-HP) omnidirectional radiation is presented. The antenna subsystem consists of a STAR antenna and a beamforming network (BFN). The STAR antenna consists of a planar circular array having four printed dipole elements surrounded by two groups of parasitic strips. The parasitic strips are used to improve the impedance bandwidth (IMBW) and reduce the gain variation in transmit (TX) and receive (RX) modes. To achieve high isolation, the four ports of the STAR antenna are excited with two orthogonal phase modes for TX and RX using the BFN. The BFN is a six-port network consisting of two 180° hybrid couplers, one 90° hybrid coupler, and a Wilkinson power divider. The 180° hybrid coupler is elaborately designed with low imbalances since it is most key to achieve high TX/RX isolation. Measured results show that the proposed STAR subsystem achieves a TX/RX overlapping IMBW of 4.71–6.2 GHz, and a 40 dB TX/RX isolation bandwidth of 4.81–5.88 GHz, while maintaining horizontally polarized omnidirectional radiation patterns for TX and RX over the entire operating frequency band. [ABSTRACT FROM AUTHOR]

The miniaturization design of the beamforming network (BFN) is the key to improving the application value of the multibeam array antenna. The traditional miniaturization method of the BFN mostly solves the miniaturization of the transverse width, while the miniaturization of the longitudinal length is rarely involved. In this article, a coexistence-mode (Co-mode) composite right-/left-handed (CRLH) substrate-integrated waveguide (SIW) transmission line technology is proposed, and this technology aims to solve the problem of miniaturization in the longitudinal length of the Butler matrix (BM). Its core is to introduce a longitudinally extended interdigital slot (IDS), force the SIW to incorporate an interdigital capacitor, and realize the phase constants of the TE10 mode and the TE20 mode reverse change. Then, the coupling region length of the couplers based on the Co-mode CRLH SIW transmission line can be reduced, and the longitudinal miniaturized directional coupler and the longitudinal miniaturized cross coupler are obtained. Finally, three types of $4\times 4$ longitudinal miniaturized BMs based on the Co-mode CRLH SIW transmission line are designed, whose longitudinal lengths are reduced by 32%, 22.1%, and 30.7% compared with those of their SIW counterparts. In addition, a miniaturized multibeam array antenna based on the Co-mode CRLH $4\times 4$ H-plane SIW BM is fabricated and measured, which verifies the applicability of Co-mode CRLH SIW transmission line technology. [ABSTRACT FROM AUTHOR]

Multibeam (MB) radiations of antenna arrays rely on effective beamforming networks (BFNs). A 2-D fisheye lens-based BFN (FL-BFN) was developed using a half 2-D lens realizable on metal parallel-plate sandwiched substrates to excite a planar antenna array. This FL-BFN implemented the beam and antenna excitation ports on its half-circular circumference and straight boundaries. An optimization scheme was developed to minimize the ray propagation distortion due to an incomplete half-lens propagation path for an offset beam, which results in an aperiodic array of antennas for MB radiations. Excitations for periodic arrays can also be implemented by considering an aperiodic output port establishment. The rule to determine the positions of antenna elements is also shown for easy design. This FL-BFN performance is demonstrated using its output amplitudes and phases to excite a Vivaldi antenna array for MB radiation. Numerical simulations and measurements over a prototype were performed to validate its feasibility with distinguished agreements. [ABSTRACT FROM AUTHOR]

This paper proposes a novel compact 4 × 4 butler matrix (BM) with improved bandwidth based on open-circuit coupled-lines and interdigital capacitor unit-cell to develop composite right/left handed (CRLH) transmission-line (TL) metamaterial structure. The BM is implemented by the combination of compact 3dB quadrature hybrid couplers, 0dB crossover and 45° phase shifter on a single FR4 substrate (εr = 4.3 and h = 1.66 mm). The simulated and measured result shows that the return loss and isolation loss are better than 14 dB at all the ports, good insertion loss of -7 ± 2dB, which cover the frequency range of 3.2 GHz to 3.75 GHz. The phase difference of -45°, 135°, -135° and +45° are achieved with a maximum average phase tolerance of 5°. The overall dimension of the BM is 70mm × 73.7mm, which shows the compactness of the proposed design that is 75% size reduction and 8.2 times improvement in the bandwidth (550MHz) as compared to conventional BM. The CST microwave studio is used to design and perform the simulations. Additionally, the simulated and measured scattering parameters and phase differences show that they are in good agreement. This compact and improved bandwidth of the proposed BM is suitable for 5G antenna array beamforming network.

A waveguide dual-polarization four-way power divider is described. It relies on a novel, broadband, and compact offset twist design, enabling an output port spacing of about 0.7 λ0 at the lowest operating frequency, which represents an improvement by approximately a factor of 2 over previously reported solutions with similar characteristics. With a highly integrated two-probe orthomode transducers (OMTs) and E-plane T-junctions arrangement, the proposed device provides good matching to free space in a small array configuration of open-ended waveguides. The concept is detailed through a specific implementation in the K-band, designed to operate over the frequency range of 17.7–20.2 GHz. The numerical model of the power divider alone achieves a frequency bandwidth up to about 3 GHz with a return loss better than 22 dB. Combined with an OMT for test purposes, the designed prototype demonstrates return loss better than 19 dB over the targeted bandwidth. This concept is of interest for the design of small passive array beamforming networks in the millimeter-wave band. [ABSTRACT FROM AUTHOR]

An antenna array is developed to radiate angularly distributed multibeams. The proposed antenna utilizes a 2-D Luneburg lens as a beamforming network (LL-BFN) to produce rotationally symmetric excitations. The concept is to replace an equivalent circular aperture of Luneburg lens by a circular array of excitation output ports. Thus, in addition to the beam selection ports, antenna excitation ports are also established on the LL-BFN to extract the required phases to feed an external circular array of antennas. As a result, more flexible radiation characteristics can be achieved by the circular array. This concept is demonstrated by both simulation and measurement results of an antenna prototype to validate the feasibility. [ABSTRACT FROM AUTHOR]

In this article, a two-dimensional (2-D) Luneburg lens-based beamforming network (LL-BFN) realizable on parallel-plate-sandwiched substrates is implemented to excite a planar phased array of antennas for near-field focus (NFF) applications of multibeam radiations. The concept is to select a proper position of a cylindrical ring surrounding the 2-D Luneburg lens and intercept the phases on this ring to excite the antenna array for NFF multibeam radiations. The intercepted phases are consistent to that required to excite a planar array for NFF radiation. Due to the circular symmetry characteristics of LL-BFN architecture, the distribution of the resulted multibeams exhibits a spatial shift of focal points when the lens is excited by angularly shifted ports on the LL-BFN. The concept is developed with both the numerical and experimental results shown to validate the feasibility of LL-BFN architecture. Practical implementation of low cost is demonstrated. [ABSTRACT FROM AUTHOR]

Starting from the input reflection coefficient of a 1:N divider/corporate-feed antenna, measured when the outputs are short-circuited, a method is proposed to estimate its losses. When the outputs are in phase, as typically occurs in beamforming network applications, the relationship between such an input reflection coefficient and losses is straightforward and variation of reflection with frequency is smooth. When the phases are different from one another, the input reflection coefficient is always smaller than above and oscillates with frequency. The oscillation amplitudes strongly depend on the phase imbalance, and in some cases, reflection can tend to zero. Nonetheless, it will be shown that a preliminary estimation of the losses is still possible. [ABSTRACT FROM AUTHOR]

A multibeam array antenna (MAA) fed by a Rotman lens with a reduced sidelobe level (SLL) is designed using a substrate integrate waveguide (SIW) technology. The designed MAA is composed of a Rotman lens and a 12 × 8 slot array, which functions as the beamforming network and the radiation part, respectively. To reduce the SLL in E-plane, dual-port excitations (DPEs) are applied, instead of single-port excitations (SPEs), at each feeding port of the Rotman lens. By using DPEs, a more tapered amplitude distribution can be obtained on the array elements as compared to using SPEs; therefore, the SLL is reduced from about −11 to −18 dB. The SLL in H-plane is controlled by introducing a Chebyshev distribution to the designed eight-element slot array. Based on the designed MAA, a fabricated prototype is measured to test the discrepancy between simulation and experiment. [ABSTRACT FROM AUTHOR]

In this paper, a compact $4\times6$ Butler matrix (BM) based on microstrip lines is designed and applied to a linear antenna array. The proposed design creates four beams in four different directions within the 27.5 and 28.5 GHz band. One of the advantages of this BM is a reduction in the size of the beamforming network (BFN). In order to attain this objective, the basic microstrip-based $4\times4$ BM is designed, and then modified to a $4\times6$ BM through a dual-substrate structure to avoid crossing lines using microstrip-to-slotline transitions. The BFN is cascaded with a six-element linear antenna array with endfire radiating elements. The array can be conveniently integrated into the BFN. The resulting design benefits from low-loss characteristics, ease of realization, and low fabrication cost. The array is fabricated and tested, and the experimental results are in good agreement with the simulated ones. The multi-beam antenna size is $5.6 \lambda \times 4.6 \lambda $ including feed lines and feed network, while the new BM design is only $3.5\lambda _{0} \times 1.4\lambda _{0} $ , which is almost half as large as the traditional one. The measured radiation patterns show that the beams cover roughly a spatial range of 90° with a peak active gain of 11 dBi. [ABSTRACT FROM AUTHOR]

This paper presents a $2 \times 2$ multibeam array employing a novel wideband linearly polarized cavity-backed patch antenna for fifth-generation (5G) wireless communication technology. The antenna array comprises four layers stacked on top of one another. The proposed antenna element is composed of three substrate layers and excited using a substrate-integrated waveguide aperture-coupled feed. The antenna element exhibits −10 dB impedance bandwidth of 36.2% from 53 to 76.4 GHz with very flat gain and excellent radiation characteristics. A prototype is fabricated and tested. The compact 2-D scanning multibeam $2 \times 2$ antenna array is demonstrated at 60 GHz, where the proposed antenna element is utilized as a radiating element. By employing a novel compact beamforming network (BFN) in the design, the proposed array achieves a size reduction of more than 28% compared to an array fed with the conventional BFN, without degradation in the array performance. A wide bandwidth larger than 27% for $\vert \text{S}_{\mathbf {11}}\vert < -10$ dB and a peak gain of 12.4 dBi is achieved. The array shows a good symmetrical radiation pattern in the two perpendicular planes. Verified by prototype measurements, the proposed antenna element and multibeam array with features of a compact structure, low cost, wide bandwidth, and superior radiation performance would be practically attractive for 5G applications. [ABSTRACT FROM AUTHOR]

A novel beamforming network (BFN) applicable to a 2 × 2 array antenna is proposed in this letter. It provides four coexisting squint beams tilted away from the array's boresight and is particularly suitable for ceiling-mount access points. The principle novelty lies in the BFN, which comprises four rat-race couplers and two 90° delay lines. With this circuit, four phase offsets, which are −90°, 0°, 0°, and 90°, can be assigned to the four antennas from the four beam ports in a rotating order. To demonstrate its applicability to ceiling-mount antennas, a 2 × 2 clover-leaf array was devised. Simulations and measurements were conducted to verify the tilting beam feature. A comprehensive coverage with elevated gains can be achieved by merging receptions from the four beams, which are applicable to up-to-date multitransceiver devices. [ABSTRACT FROM AUTHOR]

This paper reports a novel methodology to design broadband orthomode transducers with two arbitrarily spaced ports carrying orthogonal linear polarizations. The component is based on a combination of two Bøifot junctions through a series of power dividers that act as an embedded first level of the beamforming network of a radio frequency system. By controlling the separation between the ports, this original component can be used in different applications such as antenna arrays for satellite connectivity-on-the-move (where the spacing between ports must be as small as possible) or multibeam sparse arrays (where the spacing between ports may change along the array lattice). In order to verify the proposed design methodology, two identical prototypes have been produced using additive manufacturing. A complete set of measurements (standalone and back-to-back) have been carried out producing satisfactory results that are in very good agreement with the simulations. [ABSTRACT FROM AUTHOR]

A simple and low-cost single substrate layer Luneburg lens-based beamforming network (BFN) operating in $W$ -band is proposed. A multibeam antenna is then realized using the novel BFN and fabricated using a low-cost printed circuit board process. The Luneburg lens is realized by drilling holes in a substrate, and to extend the refractive index variation, a high dielectric constant substrate is embedded at the lens center. The lens is excited by radially placed open-ended substrate integrated waveguides (SIWs) at the lens circumference, feeding a subset of antenna ports placed on the opposite side of the lens. The proposed BFN thus provides half-power beamwidth (HPBW) and beam steering angle flexibility for multibeam antennas. An antenna generating seven beams was prototyped at 79.5 GHz to validate this BFN, providing measured beam steering of approximately ±41° with a broadside HPBW of 10°. The bandwidth of the proposed BFN is determined by the single-mode operation of the SIW. The fabricated multibeam antenna impedance bandwidth is, however, about 2% at 79.5 GHz because of the radiating elements. The radiating elements are series fed slot arrays placed on SIWs. [ABSTRACT FROM AUTHOR]

A folded Cassegrain lens in substrate-integrated waveguide (SIW) is presented in this letter. The proposed folded Cassegrain lens is composed of three layers. The input ports and the output ports are allocated in the bottom layer and the top layer, respectively. The stimulated cylindrical wave from the bottom layer is transferred into planar wave and then transmits to the top layer after the reflection and the coupling of the proposed lens. In contrast to the previously reported reflector lens, such topology can efficiently suppress the blockage issue and maintain the inherent symmetry simultaneously. To demonstrate its feasibility, a multibeam array based on the SIW folded Cassegrain lens is designed. Finally, fabrication and measurement are conducted, and satisfactory agreement is exhibited. [ABSTRACT FROM AUTHOR]

A novel design of multibeam array antenna without feeding network is presented in this communication. This array antenna consists of $3\times 3$ microstrip patches as radiators. In this design, a feeding network is avoided where each patch is fed by a probe. Furthermore, whatever patch is excited, the input power can be coupled to all patches through four microstrip lines located between the radiating elements. In addition, nine radiation beams can be implemented depending on different field distributions that are generated by exciting each patch individually. The proposed antenna has a simple single-layered structure and does not suffer from a complex feeding network compared with traditional multibeam antennas. The experimental results demonstrate that the scanning ranges of the nine beams are ±24° and ±45° in the vertical and horizontal directions, respectively. Moreover, measured gain for the nine beams of the implemented antenna varies from 9.06 to 10.45 dBi. [ABSTRACT FROM AUTHOR]

Blooming in data-communication applications is beyond all expectations. Smart antennas as now regarded as one of enabling technologies for next-generation wireless communication systems with its promised performance on enhancing network capacity. This paper presents a detailed analysis of the classes of smart antenna systems (SASs), including adaptive arrays, multibeam multiple-input–multiple-output (MB-MIMO) antennas, and diversity-antenna systems. This study also demonstrates practical examples of communication system with developed smart antennas, and shows that using smart antennas instead of traditional antennas highly improves the system performance. [ABSTRACT FROM PUBLISHER]

The investigation of the multimode beamforming network (BFN) has been developed from its scattering matrix (S-matrix) analysis. A substrate integrated waveguide (SIW) BFN is designed and fabricated on a single Rogers 5880 substrate. This device is not only marked by features of conventional BFN, such as Butler matrix, but also has additional benefits, e.g. more compact configuration and higher radiation efficiency. Measured and simulated results based on the proposed structure are in a good agreement, which indicates that this novel type of BFN has good characteristics and presents an excellent candidate in the development of intelligent microwave and millimeter-wave multibeam antenna systems. [ABSTRACT FROM AUTHOR]

A new type of substrate integrated waveguide (SIW) multibeam antenna is proposed for mobile satellite communications using beam switching and diversity techniques. It employs an SIW Rotman lens as the beamforming network. The prototype of a single multibeam antenna is implemented at 28.5 GHz with seven input ports and an antenna array constructed by nine SIW linear slot arrays, which can generate a corresponding number of beams along one dimension. Several such antennas are grouped in two different ways to cover a 2-D solid angle with multiple beams. Experiment results show that the 2-D solid angle around (-40deg, 40deg) X (-35deg, 35deg) or (-25deg, 25deg) x (-35deg, 35deg) are covered with 20 or 25 beams with 5 -dB beamwidth, respectively. It is demonstrated that this type of printed multibeam antenna is a good choice for communication applications where mobility and high gain are simultaneously required. [ABSTRACT FROM PUBLISHER]

This paper presents a compact SIW beamforming network (BFN) for feeding a four-beam slot array antenna, which can be used in 5G mobile applications. The proposed BFN is realized with a new 4 × 4 multi-aperture coupler (MAC) and a 4 × 4 "equal length unequal width" phase shifter. The antenna operates in the range of 28–32 GHz, and generates four beams with the maximum gain of 11.2 dBi in the directions of ±15° and ±49°. To validate the design procedure and the simulation results, the proposed antenna is fabricated and tested. The measured results show that the return loss for the input ports is more than 10 dB, and the isolations between them are more than 13 dB, across the operating frequency band. The overall occupied area of the antenna structure, including the proposed BFN, is 56.5 mm × 21 mm, which shows 33% size reduction compared to similar designs. [ABSTRACT FROM AUTHOR]

The growing complexity of satellite and mobile communication systems means that there are increasing needs for antenna arrays with multiple-beam capability. Conventional beamforming-network (BFN) configurations can be realized by different types of transmission lines, such as a microstrip line or waveguide. However, each of these has its own obvious defects. As part of a new generation of high-frequency integrated circuits, called substrate integrated circuits (SICs), substrate-integrated-waveguide (SIW) technology combines the benefits of both planar transmission-line and non-planar-waveguide technologies. It presents an excellent solution for the design and implementation of high-frequency beamforming networks, including for use at millimeter wavelengths. This paper overviews the state-of-the-art of substrate-integrated-waveguide techniques in the design and realization of innovative beamforming networks, and multibeam antenna arrays for low-cost satellite and mobile systems. Different classes of substrate-integrated-waveguide-based structures are theoretically and experimentally studied and demonstrated, to offer unprecedented performance and opportunities for specific space-and ground-based applications. [ABSTRACT FROM PUBLISHER]