An electromagnetic analysis of a cylindrical homogeneous lens

Radially symmetric lenses are ideally suited for use as multiple-beam antennas. In recent years, several investigations using a geometrical optics approach have indicated that simple lens structures such as homogeneous lenses might be suitable antennas. This paper presents an electromagnetic analysis of a cylindrical homogeneous lens as well as examining in detail the effect upon performance of parameter variations such that engineering and design evaluations can be made. It is shown that a lens with a relative dielectric constant of 3.5 gives the best performance. With the use of simple matching techniques, overall performance comparable to the more complex Luneburg lens is obtained.     

毫米波低副瓣赋形介质透镜天线设计

通过对介质透镜赋形,把初级馈源方向图转变为透镜口径面上所需的场分布函数,便可获得所需要的各种波束。本文给出了一种基于几何光学的简单而实用的透镜赋形方法,通过赋形能实现介质透镜天线低副瓣的要求。     

Compound Fresnel Zone Lens Conformal to Truncated Cone: Antenna Application

A millimeter wave antenna consisting of two Fresnel zone plate lenses, plane and conical, is examined numerically by use of the vector diffraction theory. The lenses are of Wood-Wiltse (double-dielectric) or Soret (half-open) type, and are designed for the frequency of 117 GHz. The lenses are made conformal to a truncated circular cone with a base diameter of 500 mm and a plateau diameter of 250 mm. Designs for two opening semi-angles, 45° and 75° each of them with a particular lens thickness are presented. For the angle of 90° the cone lens becomes a plane ring lens, which in combination with the plateau zone lens forms a plane lens of size equal to the cone base diameter. Illuminated by directive feeds set at a focal distance of 525 mm from the cone apex, the double-dielectric and half-open compound and plane lenses, form three pairs of Fresnel zone lens antennas, the co-polar and cross-polar radiation characteristics of which have been compared numerically. The double-dielectric lens antennas examined are about 5 dB superior in gain to the half-open lens antennas, which has a gain of approximately 45 dBi. Because all lenses are of equal transverse aperture, the corresponding lens antennas exhibit the same ?3 dB beamwidth of about 0.33 degrees. The plane zone lens antenna is very thin and simple. Instead, the antenna comprising a 3-D compound Fresnel zone lens is thicker but can be made conformal to a specific surface shape and possesses more levels of design and optimization freedom.     

Conical Double-Dielectric Fresnel Zone Lens and Antenna

A conical double-dielectric phase-reversal Fresnel-zone plate (FZP) lens is introduced. We present the lens design equations as functions of cone opening angle. As an example, the phase-reversal lens has been applied to four millimeter-wave antennas with different lens opening semi-angles: 45deg, 60deg, and 75deg (conical lenses) and 90deg (plane lens). The radiation characteristics of these antennas have been calculated and contrasted one-to-another, and to those with the same semi-angles and linear dimensions binary (half-open) FZP lens antennas. The double-dielectric FZP conical arrangement can serve as a conical antenna lens and a radome simultaneously     

Nonuniform Luneburg and two-shell lens antennas: radiationcharacteristics and design optimization

Design optimization of radially nonuniform spherical lens antennas is the focus of this paper. In particular, special attention is given to the optimal design of nonuniform Luneburg (1964) lens antennas. One of the important engineering objectives of designing an optimal Luneburg lens antenna is to use as small number of shells as possible while maintaining an acceptable gain and sidelobe performance. In a typical radially uniform design, by reducing the number of shells, the gain is decreased and the grating lobes are increased. This deficiency in the radiation performance of the uniform lens antenna can be overcome by designing the nonuniform lens antenna. This necessitates the optimum selection of each layer thickness and permittivity. A genetic algorithm (GA) optimizer with adaptive cost function is implemented to obtain the optimal design. In this manner, the GA optimizer simultaneously determines the optimal material and its thickness for each shell by controlling the gain and sidelobes envelope of the radiation pattern. Various lens geometries, including air gaps and feed offset from the lens surface, are analyzed by using the dyadic Green's functions of the multilayered dielectric sphere. Many useful engineering design guidelines have been suggested for the optimum construction of the lens. The results have been satisfactory and demonstrate the utility of the GA/adaptive cost-function algorithm. Additionally, the radiation characteristics of a novel two-shell lens antenna have been studied, and its performance is compared to the Luneburg lens     

A Plane-Wave Beam-Steering Lens Design Using Microstrip Switched-Line Phase Shifters

A compact beam-steering lens design appropriate for millimeter-wave and submillimeter-wave applications is experimentally verified with an X-band test model. The lens achieves coupling to plane-wave beams through arrays of patch antennas placed on its two outer surfaces. The isolation between input and output antennas is accomplished by inserting a metal ground plane in the middle of the lens. The two closest patch antennas on the front and the backside are connected together with microstrip circuits that include switched-line phased shifters and interconnecting vias through the lens substrate. Three different X-band 100-element plane-wave microstrip lenses that use passive delay lines instead of actual phase-shifters were fabricated to successfully demonstrate the beam-steering angles of 20 and 40 degrees. From a separate waveguide measurement on the unit-cell element only, the insertion loss of the lens was estimated to be approximately 3.5 dB with bandwidth of 2% at 10 GHz.     

Synthesis of new variable dielectric profile antennas via inverse scattering techniques: a feasibility study

In this paper, we investigate whether and how one can synthesize given far field patterns by acting on the dielectric profile of a lens antenna. In particular, an approach to design a radiating system consisting of a variable dielectric profile and a single or a low number of feeds is proposed and discussed. To properly take into account physical and practical feasibility issues, the proposed method splits the problem into two steps. The first one is aimed to fix design goals (i.e., the nominal field), in such a way to avoid super-directive or physically unfeasible antennas and properly exploits known properties of electromagnetic fields radiated by finite extent sources. The second step, dealing with the dielectric profile synthesis, is based on suitable modifications of inverse scattering techniques and can take into account constraints on the spatial behavior as well as of dielectric characteristics of the profile to be synthesized. To show the interest of the subject, as well as effectiveness of the proposed approach, the synthesis of new dielectric antennas, such as a high directivity source and a lens radiating a steerable degradation-free Chebyshev pattern, is considered in the two dimensional scalar case.     

The design of radially symmetric lenses

For scanning over wide angles at millimeter wavelengths, an antenna incorporating a radially symmetric lens is an attractive solution if the lens can be realized in a practical form. It is shown that suitable lenses can be constructed very simply, from natural dielectrics if desired, and a design technique for the optimal antenna is presented. Some results are given of analytical and experimental studies of a number of actual antennas operating at wavelengths near 4 mm. These confirm that practical solutions are available. Homogeneous lenses may be used up to antenna gains of about 35 dB, and a lens consisting of a single shell and a core is sufficient for most other practical requirements.     

Design and analysis of multiple-beam reflector antennas

Simplified design and analysis equations are presented for multiple-beam reflector antennas based on the Gaussian-beam analysis of the primary and secondary patterns. The derived equations are useful for the quick design and performance analysis in terms of the coverage-area directivity and the inter-beam isolation of multiple-beam antenna systems. Results of the analysis given in this paper agree well with rigorous computations based on physical-optics analysis of the reflector-antenna radiation patterns. Extension of the analysis to multiple-beam lens antennas, and to shaped/contoured-beam antennas, is also presented     

A novel array antenna for MSAT applications

The issue of reducing the cost of phased array vehicle antennas through the use of a lens feeding arrangement instead of phase shifters at each element is addressed. In particular, the economic viability of a mobile satellite system (MSAT) is largely dependent on the efficient use of the allocated scarce spectrum and orbit as well as the satellite power. The type of vehicle antenna used will play a critical role in achieving this efficiency. A standard design approach for an electronically steered array uses phase shifters at each element to provide beam steering. A method for reducing the required number of phase shifters by using an R-KR lens feed network is outlined. The authors briefly discuss the phase shifter approach to beam steering, examine various lens feed techniques, and describe the R-KR lens approach. The lens feed network architecture is examined, a computer model for simulation of the array is presented, and the results of analysis of a suggested design for the MSAT application are given. In addition, satellite acquisition and tracking considerations are investigated     

Design procedure for a Fresnel-zone plate antenna

A design procedure for two types of Fresnel-zone plate antennas is presented: viz. antennas with absorbing/transparent zones and phase-correcting zones. Design objectives are the optimization of the gain of the lens of the antenna and the side-lobe envelope of its radiation pattern. The design rules are derived from numerical simulations.     

Reference Phase in Diffractive Lens Antennas: A Review

We review a free parameter in the design of Fresnel zone plate lens antennas. Historically, zone plate antennas have been designed with a specific choice for this parameter, which can be taken as a type of phase reference. Two methods of interpreting the parameter have been identified, either in terms of a reference radius or equivalently a reference phase. Here, for simplicity, we treat this variable parameter as a reference phase. Importantly, the reference phase can be chosen to have non-standard values which have been shown to improve important aspects of antenna performance and to add a new functionality to zone plate antennas.     

Full-Wave Analysis of Monopulse Dielectric Lens Antennas at W-band

Lens antenna is a good substitute for the Cassegrain antenna at millimeter-wave frequencies, especially at W-band. On one hand, the antenna design, which is bulky and heavy at low frequencies, becomes compact and light-weighted at W-band. On the other hand, without the blockage caused by the sub-reflector and the feed horns which are unavoidable in a Cassegrain antenna, the lens antennas show better radiation characteristics. In this paper, several lens antennas fed by metal horns are analyzed using a full-wave method-finite element method based on the weak form of the Helmholtz equation (WF-FEM). Numerical results show that the lens antennas presented have low side lobe level (SLL), and good sum and difference performances.     

A New Unitary Space-Time Code with High Diversity Product

In this paper, we propose new full diversity unitary space-time codes based on Hamiltonian constellation designs. Our proposed constellations can be used for any number of antennas and for any data rate. For two transmitter antennas, the constellations are constructed from cyclic group codes. For a larger number of transmitter antennas, the design employs the direct sum of 2 times 2 Hamiltonian matrices and roots of unity. We give some examples of proposed constellations, and also show that they outperform known design techniques in the literature     

龙伯透镜天线的原理及其研究进展

龙伯透镜天线是一种折射率渐变的透镜天线,可将特定频率的入射波汇聚到透镜表面的某点或将电磁波沿原方向反射,能够实现波束扫描和多波束聚焦,已用于电子对抗、第五代移动通信技术、卫星通信以及军用战机和舰艇.介绍了龙伯透镜天线的基础理论,归纳梳理了球形龙伯透镜天线和变形龙伯透镜天线,总结了三种制备技术,对比了不同类型的透镜天线性能,并分析了馈源对龙伯透镜性能的影响,最后对龙伯透镜天线的发展提出建议.     

Shaped dielectric lenses for wireless millimeter-wavecommunications

Dielectric-lens antennas are effective at producing highly shaped beams that can enhance the performance of wireless broadband communication systems. Beam shaping is used to reduce multipath interference, which causes fading and decay spread, and to enhance gain, so that the received power level is compatible with the requirements of high-data-rate transmission. This paper presents an overview of the design and measured performance of some examples of dielectric lenses that can be used in typical scenarios of wireless broadband communication systems. The paper also addresses the radio coverage produced by these antennas. The lenses are based on a single basic configuration where the feed is embedded in the lens body. This antenna configuration is flexible enough to accommodate different target beam-shaping specifications     

A complete procedure for the design and optimization of arbitrarily shaped integrated lens antennas

This paper proposes a new design methodology of arbitrarily shaped integrated lens antennas (ILAs). First, we describe the design principles and numerical techniques of the optimization iterative loop. The starting lens shape, deduced from a general synthesis method based on geometrical optics principles, is optimized so that the radiation pattern of the ILA complies with an arbitrary amplitude-shaped template. The optimization procedure is local and is based on a multidimensional conjugate gradient method. Then, the capabilities and potentialities of this approach are demonstrated numerically using two examples. In the first one, an ILA radiating a secant-squared beam in one principal plane and a flat-top beam in the orthogonal plane is designed for indoor communications in V-band. In the second example (Gaussian/flat-top beam), we show for the first time that the joint optimization of the feed together with the lens shape is a very promising design methodology. Finally, our design tools are validated experimentally in Q-band through the synthesis and optimization of a peculiar small shaped ILA (28 mm/spl times/28 mm/spl times/15 mm) fed by an aperture-coupled microstrip patch antenna.     

The influence of electromagnetic environment on operation of activearray antennas: analysis and simulation techniques

This paper presents an overview of active array antennas, system-level nonlinear effects in such antennas, and their modeling and simulation techniques. Advantages of active array antennas, in comparison with passive array antennas, are discussed. The influence of nonlinear distortions and interference in active antennas on the overall system performance is considered. Modeling and simulation techniques that can be applied to active array antennas are substantially different from those used for circuits and systems. Analytical and numerical techniques are used for the analysis of active antennas, with the prevailing use of numerical techniques at the present time. Electromagnetic-level and circuit-level simulation techniques are discussed. System-level simulation techniques are considered in detail, with special emphasis on their application to active array antennas. The “instantaneous” quadrature technique is proposed as an effective tool for numerical simulation of active arrays over wide frequency and dynamic ranges in a computationally-effective way     

Gaussian beam techniques for illuminating reflector antennas

Simple design procedures are presented for use when a Gaussian beam is used to illuminate a classical reflector antenna. Displacement of the location of the beamwaist toward the focusing element in the case of electrically small antennas where the aperture is in the near field of the feed was calculated together with modification of the required beamwaist radius. Dual reflector antennas were discussed and design procedures appropriate for systems with large and small focal length to diameter ratio developed. Cases where a reflector or subreflector is electrically small, or in the near field of a feed, are readily treated. For elliptical beam antennas, a simple illumination system using only a scalar horn and a single cylindrical lens can generally be found; this has no ray optics analogue. A configuration of this type is discussed, with a practical case study of a 28-by-80-λ elliptical Cassegrain antenna operating at a wavelength of 3 mm. The design process for designing the feed system is discussed in detail. Despite the small size and relatively large aperture blockage, an aperture efficiency of 0.48 was measured, which compared quite well with the expected efficiency of 0.53, thus verifying the validity of the Gaussian beam design approach