Rotman Lens Research Articles

Coplanar rotman lens and antipodal vivaldi antenna array for L- and S-band applications

A 60 × 70 cm2 Rotman lens including seven beam ports and nine Vivaldi antenna elements is designed for 1.5–3.5 GHz frequency range. The radiation pattern is scanned in a ±24° range in seven steps, having side-lobe-levels better than 10 dB. The design is fabricated on a FR4 substrate. Measurements support simulations. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1305–1308, 2015

A Multibeam Dual-Band Orthogonal Linearly Polarized Antenna Array for Satellite Communication on the Move

The design and simulation of a 10 × 8 multibeam dual-band orthogonal linearly polarized antenna array operating at Ku-band are presented for transmit-receive applications. By using patches with different coupling methods as elements, both perpendicular polarization in 12.25–12.75 GHz band and horizontal polarization in 14.0–14.5 GHz band are realized in a shared antenna aperture. A microstrip Rotman lens is employed as the beamforming network with 7 input ports, which can generate a corresponding number of beams to cover −30°–30° with 5 dB beamwidth along one dimension. This type of multibeam orthogonal linearly polarized planar antenna is a good candidate for satellite communication (SatCom).

Fourier Rotman Lens Enabled Directional Modulation Transmitter

A 10 GHz Fourier Rotman lens enabled dynamic directional modulation (DM) transmitter is experimentally evaluated. Bit error rate (BER) performance is obtained via real-time data transmission. It is shown that Fourier Rotman DM functionality enhances system security performance in terms of narrower decodable low BER region and higher BER values associated with BER sidelobes especially under high signal to noise ratio (SNR) scenarios. This enhancement is achieved by controlled corruption of constellation diagrams in IQ space by orthogonal injection of interference. Furthermore, the paper gives the first report of a functional dual-beam DM transmitter, which has the capability of simultaneously projecting two independent data streams into two different spatial directions while simultaneously scrambling the information signals along all other directions.

Corrections to “Dielectric Slab Rotman Lens for Microwave/Millimeter-Wave Applications” [Aug 05 2622-2627

A corrected expression in the above named paper (ibid, vol. 53, no. 8, pp. 2622-2627, Aug. 2005) is presented here.

최소 위상 오차를 갖는 곡선 배열안테나용 Rotman 렌즈의 설계

컨포멀 배열에 적용할 수 있는 곡선 배열안테나용 Rotman 렌즈의 설계 방법을 제안한다. 본 논문에서는 곡선 배열안테나와 연동하여 Rotman 렌즈의 평행판 영역에 존재하는 배열 포트의 위치와, 배열 포트와 배열안테나 소자를 연결하는 전송선의 길이를 구하는 설계식을 유도하고, 이 설계식을 바탕으로 빔 곡선 최적화 절차와 재초점 절차를 통하여 위상 오차를 최소화하고 있다. 제안된 설계식과 설계 절차에 의해 설계된 Rotman 렌즈는 정확히 3초점을 보유한 채 직선 배열안테나뿐만 아니라, 원곡선, 포물선, V자형 곡선 등의 오목하거나 볼록한 배열안테나를 급전할 수 있으며, 최소의 위상 오차를 나타내고 있다. We propose a design method of a Rotman lens for curved array antenna applicable to conformal array. In this paper, design equations are derived to obtain an array curve, transmission line lengths of a Rotman lens in conjunction with a curved array antenna, and the phase error of a Rotman lens based on these design equations is minimized through the beam curve optimization procedure and the refocusing procedure. Rotman lenses designed by the proposed design equations and design procedures still maintain 3 focal points, can feed a convex or concave array antenna with circular curve, parabolic curve, V-shaped curve, etc as well as a straight line array antenna, and have minimal phase error.

Rotman 렌즈의 위상 오차 최소화를 위한 빔 곡선 최적화

본 연구에서는 Rotman 렌즈의 위상 오차를 최소화하는 빔 곡선을 구하는 최적화 방법을 제안하고 있다. 이 방법은 빔 포트로부터 배열안테나의 중심점과 배열안테나를 따라 대칭 또는 비대칭으로 놓인 두 개의 점으로 구성된 동위상점들을 통과하여 대응되는 동위상면까지의 3개의 경로길이는 동일하다는 개념에 근거를 두고 있다. 이 방법을 따르면, 각각의 빔 방향에 대하여 위상 오차를 최소화하는 배열안테나 상의 동위상점 집합을 찾으면 최적의 빔 포트 위치를 직접 구할 수 있다. 시뮬레이션 결과는 제안된 방법이 저 위상 오차를 갖는 Rotman 렌즈의 빔 곡선을 구하는 가장 최적이며 효과적인 방법임을 보여준다. In this paper, we propose an optimization method for obtaining beam curve which minimize the phase errors of Rotman lens. This method is based on idea that 3 path lengths from a beam port through equal phase points, which consist of the center point of array antenna and two points placed symmetrically or asymmetrically along array antenna, to the corresponding phase front are equal. According to this method, the optimal locations of beam ports can be obtained directly by finding each equal phase point set on array antenna to minimize the phase errors for each beam direction. Simulation results show that the proposed method is the most optimal and effective method for determining the beam curve of Rotman lens with low phase errors.

A Review on the Development of Rotman Lens Antenna

Rotman lenses are the beguiling devices used by the beamforming networks (BFNs). These lenses are generally used in the radar surveillance systems to see targets in multiple directions due to its multibeam capability without physically moving the antenna system. Now a days these lenses are being integrated into many radars and electronic warfare systems around the world. The antenna should be capable of producing multiple beams which can be steered without changing the orientation of the antenna. Microwave lenses are the one who support low-phase error, wideband, and wide-angle scanning. They are the true time delay (TTD) devices producing frequency independent beam steering. The emerging printed lenses in recent years have facilitated the advancement of designing high performance but low-profile, light-weight, and small-size and networks (BFNs). This paper will review and analyze various design concepts used over the years to improve the scanning capability of the lens developed by various researchers.

Analysis of Rotman Lens Antenna for Different Substrates for Circular Contour

This paper presents a trifocal Rotman lens design approach. The effect due to change of substrate on the circular contour is observed. The shape of the beam contour is taken as circular. Different substrates can be used for the fabrication of the lens. Three different materials have been used to fabricate the lens antenna .A three beam prototype feeding five element antenna array working in ISM band has been simulated using RLD1.7.Effects on the performance of the antenna is observed.

Asymmetric Ground Rotman Lens for Multilayer Packages

An asymmetric ground Rotman lens is presented in this letter. A new design of a Rotman lens is proposed to accommodate a whole beamforming system by providing separate ground layers for antennas and circuits. The lens has three dielectric layers and four metallic layers. The prototype of the lens consists of seven array ports, five beam ports, and six dummy ports. The measured return losses show that all the beam ports are matched to better than 12 dB in the band of interest from 23 to 25 GHz. The radiation patterns were measured in a near field measurement system. It shows that the beam directions are $-25^{\circ}$ , $-13.6^{\circ}$ , 0.2 $^{\circ}$ , 12.4 $^{\circ}$ , and 24.5 $^{\circ}$ , respectively and the beam widths are 14 $^{\circ}$ , 13.8 $^{\circ}$ , 13 $^{\circ}$ , 13.4 $^{\circ}$ , and 14.1 $^{\circ}$ , respectively. These results are in good agreement with the simulation. Thus, it is verified that the asymmetric ground lens is one of the best solutions for a compact beamforming system.

Optical transfer function (OTF) of a Rotman lens antenna for imaging applications

This paper presents a new approach to analyzing a Rotman lens for imaging applications. The optical transfer function (OTF) is used to analyze the imaging capability of a Rotman lens. The variations in optical transfer function and the image pattern were calculated with variations in the design parameters due to beam-port spacing, antenna spacing, array size, and so on. As a result, it was found that the cutoff frequency corresponds to the array size in λ , and the resolution is the inverse of the cutoff frequency. The beam-port spacing should be narrow enough to avoid aliasing. For a typical design in which the antenna spacing is λ/2 and the scanning angle is from -45° to 45°, the number of beam ports should be π/2 times greater than the number of array ports to avoid aliasing, and the antenna spacing should be less than 0.707λ to avoid grating lobes. For the first time, a Rotman lens has been analyzed in terms of the optical transfer function. As a result, important criteria for designing a Rotman lens are presented for imaging applications. This analysis will provide guidance to the design and estimation of a focal-plane antenna array, as well as a Rotman lens for imaging and sensing applications.

Design and Performance Analysis of Wide angle Microwave Lens for Wireless Communication

This paper presents analysis of non-focal Rotman lens antenna design. A ten beam prototype feeding an 20-element antenna array working in ISM band has been simulated using RLD v1.7 software. Simulation results show that the designed lens shows good performance in the operating frequency band of 2.4Ghz showing a return loss of -17db.

Fabrication of a 77 GHz Rotman Lens on a High Resistivity Silicon Wafer Using Lift-Off Process

Fabrication of a high resistivity silicon based microstrip Rotman lens using a lift-off process has been presented. The lens features 3 beam ports, 5 array ports, 16 dummy ports, and beam steering angles of ±10 degrees. The lens was fabricated on a 200 μm thick high resistivity silicon wafer and has a footprint area of 19.7 mm × 15.6 mm. The lens was tested as an integral part of a 77 GHz radar where a tunable X band source along with an 8 times multiplier was used as the RF source and the resulting millimeter wave signal centered at 77 GHz was radiated through a lens-antenna combination. A horn antenna with a downconverter harmonic mixer was used to receive the radiated signal and display the received signal in an Advantest R3271A spectrum analyzer. The superimposed transmit and receive signal in the spectrum analyzer showed the proper radar operation confirming the Rotman lens design.

Liquid crystal based Rotman lens antenna with switchable monopulse patterns

ABSTRACTAn electronically reconfigurable Rotman lens is described which generates multiple beams that can be switched from monopulse sum to difference radiation patterns when used in conjunction with a six element Vivaldi antenna array. This is achieved by exploiting the voltage‐dependent dielectric anisotropy property of nematic state liquid crystals to provide switched 0° and 180° phase shifts in the array feed lines. The viability of the concept is demonstrated by designing an antenna which exhibits dynamically reconfigurable monopulse radiation patterns over the frequency band 6–10 GHz. Measured and simulated results are shown to be in good agreement. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2721–2726, 2013

A Defocused Rotman Lens With Reduced Conjugate Port Coupling

The Roman lens is suitable as an antenna beam-forming network, but performance suffers from high coupling between symmetrically opposed (or conjugate) ports. A practical technique to reduce this coupling is presented and experimentally validated. It is proposed that the curvature of the lens contour is modified to be sub-optimal in terms of phase errors, but is done in such a way that the defocusing spreads the power and leads to reduced conjugate port coupling. The phase errors thus generated are shown to be of the same order as those found in conventional Rotman lenses. This new, defocused lens is compared to the conventional lens showing improved coupling performance without degradation of the phase performance. A lens is implemented in waveguide and measured results agree well with simulations.

Sidelobe Modulation Scrambling Transmitter Using Fourier Rotman Lens

A means for scrambling the digital modulation content in the sidelobes of a radio transmission from a steerable antenna array is presented. The method uses a Fourier transform beam-forming network simultaneously excited by an RF information stream and orthogonally injected interference streams. The proposed system is implemented using a Fourier Rotman lens and its operational characteristics are validated for a 10 GHz QPSK transmission.

Compact Rotman Lens with Size-Reduced Transition Structures between the Lens Body and the Connecting Lines

This paper introduces a new design for a Rotman lens that has been proposed to minimize its size and provide a suitable design for a compact beamforming system. The size reduction is realized by minimizing the length of the transition structures, which are positioned between the lens body and the connecting lines. The proposed structure is much shorter than a conventional transition structure, which is a tapered line in general. As a result, a 45% size reduction can be achieved by using the proposed transition structure, compared to a typical Rotman lens with linearly tapered lines. Therefore, the proposed Rotman lens will be suitable for compact beamforming systems.

Electronically scanned Rotman lens antenna with liquid crystal phase shifters

The performance of a Rotman lens, which forms fixed beams at 0°, ±15° and ±30°, is augmented using liquid crystal phase shifters to simultaneously steer each beam by up to ±7.5°. Measured results are used to demonstrate that the true time delay property of the antenna and voltage controlled phase shifters can be exploited to provide continuously scanned beams with full coverage over an angular range of ±37.5°, and with operation over the band 6–10 GHz.

A Multibeam Antenna Array Based on Printed Rotman Lens

A compact printable multibeam antenna array is studied in this paper. The antenna system is composed of a printed Rotman lens and an antipodal dual elliptically tapered slot antenna array; both of the two components are studied, respectively, at first, and then integrated on a single printed circuit board to make up the integrated unit of the multibeam antenna array. Measured results of all components are presented.

Improved phase performance for rotman lens

Rotman lenses are used to obtain multiple beams from a single array. Although the beams produced by the feed antennas at focal points have no path length errors, the beams produced by feed antennas at off focal points may have large path length errors. These path length errors cause deterioration in the multiple beams. In this article, two novel methods are introduced to obtain feed curves which reduce the path length errors of off focal feed points significantly, compared with the commonly used circular and elliptical feed curves. The first method obtains feed curve points based on having zero path length error at three chosen points of the radiating array for each beam direction. The second method uses the particle swarm optimization method for obtaining optimum feed points for each beam direction. The results show that there is a very significant drop in the level of the maximum path length errors (in the order of about 1:4). © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 634–638, 2013.

Integration of Array Antennas in Chip Package for 60-GHz Radios

This paper discusses the integration of array antennas in chip packages for highly integrated 60-GHz radios. First, we evaluate fixed-beam array antennas, showing that most of them suffer from feed network complexity and require sophisticated process techniques to achieve enhanced performance. We describe the grid array antenna and show that is a good choice for fixed-beam array antenna applications due to its easy feed network design and manufacture. Then, we examine switched-beam array antennas using the Rotman lens or Butter matrix, illustrating that they allow scanning only in one plane and some miss a link even in the boresight direction. Nevertheless, a switched-beam array antenna uses a conceptually simple switch circuit to select the best signal path and may be a cost-effective approach to implementing steerable antennas in the 60-GHz band. Finally, we describe adaptive beam or phased array antennas and highlight the challenges and practical realizations of phased array antennas in both ceramic and organic chip packages for single-chip 60-GHz radios.