Rotman Lens Research Articles

Performance Analysis and Design Considerations of the Near-Field-Focused Rotman Lens Antennas

This study investigates the application of Rotman lens antennas in the near field. The design equations of these antennas have been derived in the near field and demonstrated to be highly effective. By considering specific examples, the shapes of the inner surfaces of these lens antennas have been analyzed and discussed, revealing how practically realizable lens surfaces can be designed. As these Rotman lenses are perfect at only three points in the near field, they exhibit phase errors at other points along a line connecting the three near-field focal points, resulting in deterioration of the near-field patterns. It has been shown that by selecting the lens parameters appropriately, these phase errors can be kept to a minimum, causing only minimal beam deterioration. Compared to far-field-focused Rotman lens antennas, near-field-focused Rotman lens antennas achieve significantly higher power levels, having 3.8 to 6.3 dB improvement for different beams of a 17-element array. The study has demonstrated the potential of Rotman lenses as multiple beamforming antennas for near-field applications.

Development and Simulation of 26 GHz Beamforming Systems and Antenna Array 5G Network Base Stations

This paper focuses on designing a new structure of beamforming networks with an array antenna to control the beams. The 3×4 array antenna structure connects to the 3×3 Rotman lens beamformers to achieve this goal. The middle time delay line is around 14 mm. The design allows the x-axis to cover +25, 0, −25 degrees. Therefore, this work targets fifth generation (5G) application, which necessitates coverage in all directions by other base stations or users. Computer Simulation Technology (CST) microwave software facilitates the simulation process. The design begins with a single microstrip patch antenna, designed to function as an array antenna resonating at 26 GHz. The half-lambda separation (λ/2) among antennas gives 13.8 dBi gain with S11<−10 dB. The final structure for beamforming networks has a gain of 14 dBi. This work uses the Roger 5880 substrate, which has a dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 0.127 mm.

A Volumetric Waveguide-Type Rotman Lens Antenna for Three-Dimensional Millimeter-Wave Beamforming.

In this paper, a volumetric Rotman lens antenna operating at 28 GHz is proposed. The design formula and procedure were derived for the 3-D Rotman lens antenna. The number of tilted beams is 3 × 3. The six rectangular blocks are assembled using a metallic bolt. The input port consists of a waveguide, and the output port is made of an open-ended waveguide. The input and output waveguides are drilled in a flat conducting plate. The input and output port positions are optimized. Simulated and measured results show that the radiating beam is controlled almost exactly as calculated. Compared with the previous two-stage stacked Rotman lens antenna, the proposed Rotman lens antenna can dramatically decrease the antenna volume by approximately 75%.

Design and fabrication of waveguide‐based graded refractive index Rotman lens with an improved insertion loss at Ka‐band

AbstractThe design and optimisation of a five‐cascade layer Rotman Lens based on waveguide with a graded refractive index at Ka‐band frequency are presented. The proposed lens incorporates 5 layers within the cavity, utilises a modified three focal Rotman lens design methodology to achieve perfect phasing for true time delay beam steering, and optimises each layer's parameters such as refractive index, vertex location, and contour angle to improve insertion loss between input ports and output array elements. This approach enhances energy concentration between input and output ports, reducing spillover to dummy ports. The graded layers are formed using periodic cubic metallic posts with varying heights within a parallel plate waveguide. The results show an average improvement in the insertion loss of 16% and a peak improvement of 48% across the bandwidth when compared to conventional Rotman lenses. The normalised average phase error across the array elements for all beam ports excitation is 4 × 10−3 and the peak degradation of the main beam during beam scanning from 0° to ±22° varies from 0.7 to 1 dB at different frequencies operating in the Ka‐band (24–30 GHz) with potential applications for 5G communications. The simulation results demonstrate good agreement with the measurement results.

Design of a novel wide-angle Rotman lens beamformer for 5G mmWave applications

The attachment of 5G with millimeter wave (mmWave) frequencies offers massive capacity and low latency to reveal the full 5G experiences. High directive gain and beamforming are considered essential for mmWave 5G systems. The main requirements of the beamforming network for 5G mmWave applications are the scanning coverage of ± 60° and SLL > 10 dB in a wide operational bandwidth over the standard 5G frequency bands. In this paper, a novel PCB-based wide-angle Rotman lens beamformer is designed, simulated, and successfully measured to meet the mentioned requirements for 5G mmWave applications. A comprehensive improved design methodology is provided for all components of the Rotman lens to reach a wide scanning angle, enhanced sidelobe level, and low scan loss. The end-fire Vivaldi antenna is selected as an array element for easy integration to the beamforming network as well as its capability to use in dual-polarization configuration. The proposed Rotman lens is operational in the 24–30 GHz frequency band covering 5G n257, n258, and n261 frequency bands. The results show a nearly constant 8 beams across the whole bandwidth steering from − 53° to 53° in 15° increments to provide ± 60° coverage with the SLL > 10 dB and scan loss < 1.9 dB. The retrieved novelties from this work contain an effective design methodology for an optimized Rotman lens with wide-scan angle and low phase and amplitude error, non-uniform distribution based array ports, and integration with end-fire antenna for possible dual polarization and 2-D beamforming capabilities. The comparison of the proposed beamformer with the most recent works shows several advantages in terms of integrated structure and performances including bandwidth, wide scanning angle, SLL, and scan loss. With such performances, this beamformer can be used for various mmWave and 5G applications such as advanced antenna systems, massive MIMO systems, and hybrid beamforming systems.

Differential beamforming using Rotman lens for wireless sensor networks

In this article, an optimal beamforming technique using a low cost intelligent Rotman lens antenna is proposed. The proposed technique enjoys full diversity with high coding gain, has a very low encoding and decoding complexity, and does not require channel knowledge at any transmitting or receiving antenna. From our simulation results, the proposed technique outperforms the best known non-coherent multi-antenna techniques. Furthermore, we prove that the BER expressions obtained from the theoretical analysis enjoy full diversity gain and match our conducted simulations.

Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band.

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.

Miniaturization of Rotman Lens Using Array Port Extension

This letter proposes a miniaturization design of Rotman lens using array port extension technique. The array ports of the proposed 4 × 12 Rotman lens are extended from an initial 4 × 7 Rotman lens through a port extension (PE) network to achieve a smaller equivalent lens body. The initial Rotman lens and the topology for the PE network are designed based on the analysis of phase distributions along the extended array ports when different beam ports are excited. The proposed design allows all the beam pointing angles to be consistent before and after extension at center frequency. A prototype working at X-band was fabricated. The measured results show that all beam ports are matched well, and high isolations between beam ports are achieved from 8 to 12 GHz. The Rotman lens provides a ±29° scanning range with four uniformly distributed beams at 10 GHz. The beam pointing angles remain relatively stable within 20% frequency bandwidth, with the maximum angle distortion of ±3°.

Substrate-Integrated Coaxial Line (SICL) Rotman Lens Beamformer for 5G/B5G Applications

High-band allocations in the millimeter-wave (mm-Wave) frequency spectrum offer high-capacity wireless information transmission as required by fifth generation (5G) communication standards. Among different beamforming structures, the Rotman lens (RL) is an attractive passive-microwave-lens-based beamforming network due to its low fabrication cost, reliability, design simplicity and wide-angle scanning capabilities. Conventionally, the RL is implemented using microstrip line (MSL) technology for which there are inherent radiation losses that become severe when operating in mm-Wave 5G frequency bands. In this context, a novel substrate-integrated coaxial line (SICL)-based RL is designed, fabricated and tested, for accurate beamforming with extremely low feed line insertion loss. This article presents a complete design, development and performance analysis of an SICL-based RL beamformer. By using an SICL, isolation of up to 15 dB is achieved between the input beam ports of the RL, while the mutual coupling is kept at less than 20 dB. The SICL design shows a −10 dB insertion loss between the array and beam ports when compared to the same RL developed using MSL technology having an insertion loss of −15 dB. Due to the use of low-loss SICL technology, a realized gain of up to 14.2 dBi is achieved with an excellent scanning capability of −30 to 30 degrees, verifying for the first time the beamforming capabilities associated with SICL technology. The operational frequency band is 20–45 GHz, while the center operating frequency is 26 GHz making it appropriate for above 6-GHz 5G New Radio (NR) operating bands n257 (26.5 GHz to 29.5 GHz), n258 (24.25 GHz to 27.5 GHz), n261 (27.5 GHz to 28.35 GHz) and n260 (37 GHz to 40 GHz). Owing to the low-loss and stable beamforming performance, the SICL RL is suitable for mm-Wave 5G and is extendable to B5G applications.

Communication Triple-Mode Planar Phased Arrays of Antennas Using Trifocal Rotman Lens as Switchable Mode-Former for Vehicular Radar Applications

A trimode phased array of antennas is presented for vehicular radar applications to provide both short- and long-distance coverages, which radiates various gains and beamwidths at different modes of coverage. The mode forming network is realized by applying the concept of a trifocal Rotman lens beamforming network (RL-BFN), where its beam ports serve as a mode selector. This approach first computes the required excitation phases for the desired radiation patterns at different modes. They are then used to design the trimode RL-BFN such that its outputs produce precisely the desired mode excitation phases. A practical transmitting (TX) antenna array at the 77 GHz band is presented with numerical simulations and measurements of an antenna prototype to validate the conceptual feasibility.

Compact Half-Luneburg Lens Antenna Based on a Glide-Symmetric Dielectric Structure

In this letter, we present a planar half-Luneburg lens antenna based on a glide-symmetric dielectric structure. The proposed half-Luneburg lens antenna provides a compact alternative to planar beamformers such as conventional Luneburg and Rotman lenses, as well as pillbox antennas. Importantly, we demonstrate that the peak gain of the half-Luneburg lens antenna is less than 1 dB lower than the peak gain of a conventional Luneburg lens antenna, despite being almost half the size. The proposed antenna can steer its beam in a 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> range with scan losses lower than 2 dB and side lobe levels below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 10 dB. The proposed design is validated experimentally with a robust and cost-effective implementation using additive manufacturing.

Microstrip Rotman Lens for Mobile Base Station Backbone in Disaster Area Networks

Mobile Cognitive Radio Base Station (MCRBS) is a technology to recover network communication temporarily in disaster areas. The communications can be built by constructing the backbone network, where it is formed by connecting multiple MCRBSs with point-to-point radio communication link considering the best routing algorithm. The MCRBS antenna system should has an ability on producing the beam into specific direction to establish point-to-point radio communication link. However, there is no capable system to support the MCRBS antenna system for directing the beam. Therefore, it requires a system that can assist in focusing the beam of antenna system for the MCRBSs connectivity. In this paper, we propose Rotman Lens that has beamforming capability to support radio backbone communication for multiple MCRBSs connectivity in post-disaster networks. The Rotman Lens is chosen to generate amplitude and phase shift in performing beamforming technique with simultaneous signal transmissions from MCRBS to others without moving the antenna system. In this research, the Rotman Lens was evaluated through a series of computer simulations and laboratory experiments to investigate the lens performance. The final proposed lens provides the experiment results for all beam ports with an average value both return loss and mutual coupling of less than −15 dB and −20 dB, where the magnitude deviation in average value and the maximum error of phase difference are 1.172 dB and 6.014º , respectively. The proposed Rotman Lens is also confirmed to be capable of controlling beam with scanning capability of −27º , −14º , 0º , 14º , 27º to support wireless communication backbone link among MCRBSs in disaster recovery networks

Multibeam SIW Leaky-Wave Antenna with Beam Scanning Capability in Two Dimensions

This paper presents a 2D multibeam antenna (2D-MBA) for two-dimensional scanning of space with fully passive elements using the substrate integrated waveguide (SIW) leaky-wave antenna (LWA) and Rotman lens for telecommunication applications. An LWA structure with 19 slot elements based on SIW in the frequency range of 14.5–22.5 GHz was designed to scan theta angles from −60 to +35 degrees, and a wideband Rotman lens was designed with five inputs, five outputs, and eight dummy ports to scan phi angles from −30 to +30 degrees. Finally, for two-dimensional space scanning, a five-element SIW LWA array was combined with a Rotman lens, and the whole structure was simulated and implemented in full-wave CST software. By optimizing the structure, the return losses of the input ports were below −10 dB, and the maximum measured gain was 20.3 dBi.

Rotman lens: Systematic review of simulation approaches

The beamforming technique is an important factor in designing modern wireless communications systems. While Rotman lens is a vital method to achieve the ability to steer the radiation pattern at the desired locations. Besides, there are many contributions to enhancing the performance of such lens, however, a classification to review this development is required. The main objective in this study objective is to explain and discuss the historical evolution of the Rotman lens as a beamformer based on the simulation methods used to analyze the mathematical model of the Rotman lens. The study shows that the variety of the methods is to achieve accurate simulation results while the simulation time and hardware computer requirements are still a challenge.

Rotman lens: Systematic review of simulation approaches

Rotman lens: Systematic review of simulation approaches

ШИРОКОПОЛОСНОЕ ДОУ НА ОСНОВЕ ПЕЧАТНОЙ ЛИНЗЫ РОТМАНА ДЛЯ МНОГОЛУЧЕВЫХ АНТЕННЫХ РЕШЕТОК

The most well-known beamforming device (DOU) (for linear and flat MAR) is the Rothmanlens, which is of great interest because it allows you to form a fan of MAR rays in a wide spatialsector of angles (wide-angle scanning), has a fairly high efficiency and MAR with a lens Rothmanhas a low level of side lobes. Another advantage of the MAR with a Rothman lens is the weak dependenceof the position of the rays in space on frequency, in contrast to the MAR with a Butlermatrix DOE, in which, at a high efficiency (theoretically 100%), the position of the rays dependson the frequency. However, the previously developed analogs of the Rothman lens are large andrequire additional components in the design, which affects the transmission coefficient of the lensin the operating frequency range from 2 GHz to 20 GHz and the consistency of the device withother components of the transceiver equipment. It follows that the study and modernization of lensstructures in relation to multibeam antenna arrays (MAR) is a topical topic for research. The purposeof the work is to propose a method for calculating the Rotman lens, modernize the lens design,make a lens model and conduct an experimental study of the lens in order to obtain constructivemethods for optimizing the characteristics of the Rotman lenses for use in MAP in the frequencyrange from 2 GHz to 20 GHz. In the results of the article, the dimensions of the lens, themass of the lens, the transmission coefficient, and the simplicity of the design are estimated incomparison with the previously developed analogues. A technique for calculating the geometry ofa Rotman lens is proposed, the SWR of a printed Rotman lens is experimentally studied on a vectornetwork analyzer, constructive methods are obtained for optimizing the characteristics of Rotmanlenses for use in multibeam antenna arrays. A model of a broadband Rotman lens in microstripdesign with a maximum SWR of 1.3 (S21) in the operating frequency range from 2 to 20 GHz wasmade, the lens size was 150x100, and the lens weight was 0.4 kg. According to these parameters,the Rothman lens surpasses the analogues developed earlier.

Gain-Equalized Multibeam Antenna Fed by a Compact Dual-Layer Rotman Lens at K a -Band

This communication presents a gain-equalized <inline-formula> <tex-math notation="LaTeX">$K_{a}$ </tex-math></inline-formula>-band Rotman lens-fed antenna by using phase gradient transmission lines (PGTLs). With PGTLs, the variation trend of the output progressive phase differences among the feeding ports is inverted. The aperture loss of the planar antenna array is then partially compensated by the efficiency of the lens when performing a wide-angle beam scanning. Hence, gain equalization is achieved among multiple beams with an acceptable gain degradation. To reduce the total size, the Rotman lens with PGTLs, the feeding networks, and the antenna array are stacked vertically. Meanwhile, the feeding network is implemented with substrate integrated coaxial lines, suppressing the parallel-plate mode inside the multilayer structure. In order to validate the proposed design, a compact Rotman lens-fed antenna operating at 24.75&#x2013;27.5 GHz (FBW &#x003D; 10.5&#x0025;) is designed and fabricated. The results show that the gain drop of the Rotman lens-fed multibeam antenna is reduced from 4.4 to 1.5 dB at the design frequency of 26 GHz, covering a wide angular range between &#x00B1;56&#x00B0;.

Phased array beamforming networks

The work is devoted to studying multibeam phased array beamforming networks based on the Butler matrix and Rotman lens. The study was performed under conditions similar to those in the telecommunication satellite service area. The microstrip circuit pattern was developed; the amplitude and phase frequency responses were investigated taking into account losses in materials. Array directional patterns for beamforming variants were calculated. Evaluation of adjacent ray overlay within the service area was carried out. Conclusions about acceptability of the proposed beamforming networks were made. Keywords: beamforming network, antenna array, Butler matrix, Rotman lens.

Диаграммообразующие схемы многолучевой антенной решетки

The work is devoted to the study of multibeam phased array beam forming networks, based on Butler matrix and Rotman lens. The study was made with similar conditions of the same telecommunications satellite service area. The microstrip circuit pattern was developed, the amplitude and phase frequency response were investigated, arrays directional patterns for beam forming variants were calculated. Evaluation of adjacent ray overlay inside service area boundary was carried out. Conclusions about acceptability of the proposed beam forming networks were made.

A Beamforming Technique Using Rotman Lens Antenna for Wireless Relay燦etworks

Rotman lens, which is a radio frequency beam-former that consists of multiple input and multiple output beam ports, can be used in industrial, scientific, and medical applications as a beam steering device. The input ports collect the signals to be propagated through the lens cavity toward the output ports before being transmitted by the antenna arrays to the destination in order to enhance the error performance by optimizing the overall signal to noise ratio (SNR). In this article, a low-cost Rotman lens antenna is designed and deployed to enhance the overall performance of the conventional cooperative communication systems without needing any additional power, extra time or frequency slots. In the suggested system, the smart Rotman lens antennas generate a beam steering in the direction of the destination to maximize the received SNR at the destination by applying the proposed optimal beamforming technique. The suggested optimal beamforming technique enjoys high diversity, as well as, low encoding and decoding complexity. Furthermore, we proved the advantages of our suggested strategy through both theoretical results and simulations using Monte Carlo runs. The Monte Carlo simulations show that the suggested strategy enjoys better error performance compared to the current state-of-the-art distributed multi-antenna strategies. In addition, the bit error rate (BER) curves drawn from the analytical results are closely matching to those drawn from our conducted Monte Carlo simulations.