Reflector Antenna Design Research Articles

The EISCAT Svalbard radar: A case study in modern incoherent scatter radar system design

The EISCAT (European incoherent scatter) Svalbard radar (ESR) was officially inaugurated on August 22, 1996. This event marked the successful completion on schedule of the first phase of the EISCAT Svalbard radar project. In contrast to previous incoherent scatter radars, the ESR system design was adapted to make use of commercial off‐the‐shelf TV transmitter hardware, thereby reducing design risk, lead times, and cost to a minimum. Commercial hardware is also used in the digital signal processing system. Control and monitoring are performed by distributed, networked VME systems. Thanks to modern reflector antenna design methods and extreme efforts to reduce the receiver noise contribution, the system noise temperature is only 70 K, thus making the ESR about 30% faster than the much more powerful EISCAT UHF radar in F region experiments! Once the transmitter power is increased to 1 MW, it will become about 2–3 times faster than the UHF radar. State‐of‐the‐art exciter and receiver hardware has been developed in‐house to accommodate the special requirements introduced by operating the radar at the exceptionally high duty cycle of 25%. The RF waveform is generated by a system based on four switchable direct digital synthesizers. Continuous monitoring of the transmitted RF waveform by the receiver system allows removal of klystron‐induced spurious Doppler effects from the data. Intermediate‐frequency sampling at 7.5 MHz is employed, followed by fully digital channel separation, signal detection, and postdetection filtering in six parallel receiver channels. Radar codes for both E and F layer observation have been designed and perfected. So far, more than 40 hours of good quality ionospheric data have been collected and analyzed in terms of plasma parameters. While the tragic loss of the Cluster mission suddenly changed the plans and dispositions of a majority of the ESR user community, the radar has still been in high demand since its inauguration. It is now being operated by EISCAT staff on a campaign basis, to provide ground‐based support data for a number of other magnetospheric satellites, notably Polar and FAST, and will be opened to the EISCAT user community for special program operations later in 1997.

Development of a Low RCS Reflector Antenna

ABSTRACT RCS (Radar Cross Section) reduction by proper shaping is applied to the problem of reducing the RCS levels of a center fed parabolic reflector antenna system such that antenna gain, sidelobe level, and physical size of the reflector are preserved. A detailed numerical - physical investigation of the electromagnetic scattering phenomena associated with parabolic reflector antennas is presented. The electromagnetic scattering phenomenon are identified and categorized according to their contributions to the overall RCS level of the antenna system. The dominant scattering phenomena is used to formulate a low RCS design requirement for the design of low RCS reflector antennas. These antennas have radiation characteristics similar to center fed parabolic antennas, but have greatly reduced RCS levels. A new low RCS reflector antenna system is designed to replace an existing center fed parabolic reflector antenna system. The new antenna is designed by combining a high frequency, ray based, reflector design technique with the low RCS design requirements. The newly designed low RCS reflector antenna system is found to have transmitting characteristics similar to that of the original center fed reflector parabolic antenna but with RCS levels reduced by up to 25 dB.

Design, fabrication, and testing of a paraboloidal reflector antenna and pulser system for impulse-like waveforms

In this paper, we describe an antenna and pulser system designed to radiate an impulse-like waveform. Specifically, we have analyzed, designed, fabricated, and tested a reflector antenna fed by a pair of conical transmission lines. The voltage waveform that feeds the antenna is a fast-rising (10-90% rise of /spl sim/100 ps), slowly decaying (e-fold decay of 20 ns) pulse with a differential amplitude of /spl plusmn/60 kV. The calculated and measured bore-sight-radiated field, at a distance of 304 m, is impulse-like with a peak amplitude of 4.2 kV/m.

A note on reflector-feed element realizability and optimality

Reflector-antenna design has reached a mature state of development. Sophisticated techniques, such as the use of array feeds for the correction of surface distortion, are now available. With sophistication, there is the danger that designers will lose sight of fundamental principles. In reviewing a manuscript submitted to the IEEE Transactions on Antennas and Propagation, on the subject of array feeds for reflector antennas, the author found that the numerical results presented in the manuscript were based on an element-pattern/spacing relationship that was unrealizable. The present note may help to avoid such difficulties, by presenting simple formulas that relate the realizability and optimality of feed antennas to reflector f/D, i.e. the ratio of focal length to diameter. The author discusses the optimality of feed elements in terms of a maximum-gain criteria for the reflector antenna, and considers the question of the realizability of an array-feed element in terms of its minimum aperture (i.e. spacing) requirement.

Pattern optimization of a reflector antenna with planar-array feeds and cluster feeds

We study pattern optimization of a parabolic reflector with planar-array feeds and cluster feeds. The optimization is carried out within the conjugate gradient method (CGM) in which the optimum weight vector of a linearly constrained minimum variance (LCMV) beam former is used as the initial condition. Optimization with the CGM to determine element weights is found to yield better sidelobe suppression and true settlement of desired scan direction compared to the LCMV beam former and conjugate field matching (CFM) techniques for the continuous beam-scanning case. The proposed method is also applied to multibeam reflector-antenna design.

A novel fast algorithm for physical optics analysis of single and dual reflector antennas

A novel physical optics algorithm to compute the far field of dual reflector antennas is presented. The algorithm can be also used with single reflector antennas and is particularly useful for many reflector antenna design problems where optimization techniques involving iterative analysis are required. It is based on the discretization of the surfaces in a number of quasi-equal area and quasi-squared patches that are substituted by their planar and square equivalents for a fast computation based on analytical beams. A good compromise is found between the number of patches and the complexity of the representation of the fields at any patch. The results demonstrate the accuracy of the algorithm and its efficiency in terms of CPU time consumption.

Analysis of quasiperiodic reflector antenna

A procedure for the design of a planar reflector antenna comprising a quasiperiodic metallic echelette grating is described. The reflector is designed so that the power radiated by the feed is deflected by the various portions of the reflector towards a desired direction. The possibility of steering the main beam by shifting the frequency with nearly no loss in gain is demonstrated. The sensitivity to cell fabrication errors and to improper feed location, which is essential information for the antenna designer, is examined.

Small efficient axially symmetric dual reflector antennas

Two efficient small dual reflector antenna designs are analyzed using the method of moments. One is based on the standard Cassegrain system and the other is a displaced axis design. Both incorporate a low-blockage feed consisting of a dipole radiating in the presence of parasitic elements. In the first case, efficiencies greater than 55% were obtained for 20-wavelength main reflectors; in the second, an efficiency greater than 67% was achieved for a 22-wavelength main reflector. >

Design and performance of a reconfigurable mesh reflector antenna. Part 1: Antenna design

The theory and design of a reconfigurable mesh reflector antenna is described with particular reference to satellite applications. As an example, it is shown that antenna pattern reconfiguration can be achieved for a 50-wavelengthdiameter antenna using 78 actuators with performance very comparable with that prescribed for an antenna fed from an array. The predicted performance relies on an accurate mechanical model for the knitted mesh surface, which is developed here using a network of elastic springs. The effectiveness of the model is demonstrated. Other factors affecting performance, such as boundary constraints and the means to control the mesh surface, are discussed together with tolerances on actuator settings.

Design and performance of a reconfigurable mesh reflector antenna. Part 2: Antenna performance

For pt.1 see ibid., vol.138, no.6, p.485-92 (1991). The paper describes the performance of an electronically controlled reconfigurable mesh reflector antenna operating at a frequency of 10 GHz. The antenna, which is controlled from a personal computer, is capable of being reconfigured to achieve a wide range of antenna patterns. Patterns are measured using the QMW compact antenna range and excellent agreement is obtained between measured and predicted results. Reconfiguration between a high-gain beam and a shaped beam is demonstrated as well as the potential for beam scanning without feed movement.

A comparison of reflector antenna designs for wide‐angle scanning

AbstractConventional reflector antennas are typically designed for up to ±20 beamwidths scan. In this paper, we try to stretch this scan range to some ± 300 beamwidths by varying various parameters of single‐ and dualreflector antennas. It is found that a symmetrical parabolic reflector with f/D = 2 and a single circular waveguide feed has the minimum scan loss (only 0.6 dB at θ0 = 8°, or a 114 beamwidth scan). Reduction of antenna size by means of focal length folding (Cassegrain) of cluster feed implementation is discussed.

Lens antennas with amplitude shaping or sine condition

The paper demonstrates the method of generic curve series to obtain the profiles of dielectric antennas, with design conditions either for the specification of the aperture-amplitude distribution from a given source distribution, or for agreement with the Abbe sine condition. The method has already proved successful in the design of dual reflector antennas, and the extension to refractive media is shown to be straightforward. The method basically involves obtaining two equivalent expressions for a fundamental parameter from the usual optical equations and internal geometry of the lens, and obtaining agreement between them by a computational optimisation procedure using the series of curves. The parameter used in the paper is the internal segment of the ray within the lens. The method applies equally well to lenses with other a priori conditions such as afocal linear magnification or off-axis bifocality.

An Adaptive Multiple-Beam Transmitter for Satellite Communications

A multiple-beam satellite communications system that can adaptbeam power to varying beam traffic is proposed. A new type active-array fed, single reflector antenna design and an S band, 5-beamsystem concept including interbeam exchange are described. Basedon these concepts, a high EIRP multiple-beam system with trafficadaptability similar to a single-beam system is realized.

Reflection characteristics of a dielectric slab containing dielectric or perfectly conducting cylindrical gratings

A theory based on Fourier-Bessel expansions and the T-matrix method is presented to compute the reflection and transmission characteristics of dielectric or perfectly conducting cylindrical gratings embedded in a dielectric slab. It is shown that such gratings discriminate quite effectively between TE and TM polarizations even at normal incidence. These results are important in designing semitransparent mirrors for lasers as well as in reflector antenna design.

Dual reflector antennas with amplitude phase or Abbé conditions

The design of dual reflector antennas has been simplified by a method of deriving the secondary reflector from any prescribed main reflector for quite general focusing conditions. Consequently, main reflectors which are constructed from a series of generic curves can be considered, and they and their associated subreflectors optimised to satisfy a given second condition by numerical methods. This is illustrated for antennas obeying the Abbé sine condition or giving a prescribed aperture distribution by optimising the coefficients and parameters of a quite arbitrary series of generic curves.

An offset bifocal reflector antenna design for wide-angle beam scanning

A synthesis procedure and performance results for an offset dual reflector with perfect focusing at \pm 8\deg of beam scan are presented. This bifocal antenna extends the theory of the previously reported symmetric system to an offset design. Approximations, such as the smearing of points into a focal ring, are eliminated, as is blockage. The offset design affords greater design flexibility, although the synthesis is more complex. Computed and experimental results demonstrate the improved beam-scanning performance of this antenna.

Shaped reflector antenna design, B. S. Westcott, Research Studies Press Ltd., Letchwooth, Hertfordshire, England, No. of pages: 186. Price: £23.00

International Journal of Satellite CommunicationsVolume 2, Issue 2 p. 140-140 Book ReviewFree Access Shaped reflector antenna design, B. S. Westcott, Research Studies Press Ltd., Letchwooth, Hertfordshire, England, No. of pages: 186. Price: £23.00 Peter Balling, Peter Balling TICRAA/S, Copenhagen, Denmark (formerly INTELSAT, Washington, DC)Search for more papers by this author Peter Balling, Peter Balling TICRAA/S, Copenhagen, Denmark (formerly INTELSAT, Washington, DC)Search for more papers by this author First published: April/June 1984 https://doi.org/10.1002/sat.4600020215AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume2, Issue2April/June 1984Pages 140-140 RelatedInformation

Systematic design of a dual offset reflector antenna with an elliptical aperture

Systematic design of a dual offset reflector antenna with an elliptical aperture

A spectral-iteration technique for analyzing a corrugated-surface twist polarizer for scanning reflector antennas

An analysis of the corrugated-surface twist polarizer which finds application in the design of scanning reflector antennas is presented. The spectraI-interation technique, a novel procedure which combines the use of the Fourier transform method with an iterative procedure is employed. The first step in the spectral-iteration method is the conversion of the original integral equation for the interface field into a form which is suitable for iteration using a method developed previously. An important feature of the technique is that it takes advantage of the discrete Fourier transform (DFT) type of kernel of the integral equation and evaluates the integral operators efficiently using the fast Fourier transform (FFT) algorithm. Thus, in contrast to the conventional techniques, e.g., the moment method, the spectral-iteration approach requires no matrix inversion and is capable of handling a large number of unknowns. Furthermore the method has a built-in check on the satisfaction of the boundary conditions at each iteration.

Conformal Mapping and Complex Coordinates in Cassegrainian and Gregorian Reflector Antennas

In a Gregorian or Cassegrainian reflector antenna, the complex coordinate u' of an output ray is related to the corresponding input coordinate u by a bilinear transformation, u' = (au + b)/(cu + d). We discuss the properties of this transformation, derive its coefficients a, b, c, d, and give explicitly the conditions that must be satisfied in order that symmetry be preserved. The conditions are expressed directly in terms of the parameters that specify the path of the principal ray, which is the ray corresponding to the feed axis. The results are directly related to well-known properties of stereographic projections, and they are shown to be useful in the design of multi reflector antennas which minimize aberrations and cross-polarization.