Showing papers on "Fresnel zone antenna published in 1981"
TL;DR: In this paper, the authors derived bounds for the proper range of spacing of perturbations along the dielectric rod to avoid an intrusion upon a grating lobe when frequency scanning, and some experimental results were reported on sidelobe levels and polarizations in the far field for these antennas made from a material with ϵ r = 2.33 at 81.5 GHz.
Abstract: Dielectric rod leaky-wave antennas have the property of being frequency scannable. Bounds are derived for the proper range of spacing of perturbations along the rod to avoid an intrusion upon a grating lobe when frequency scanning. In addition some experimental results are reported on sidelobe levels and polarizations in the far field for these antennas made from a material with \epsilon_{r}= 2.33 at 81.5 GHz.
56 citations
TL;DR: In this paper, a new pseudosampling expansion, which explicitly takes into account the extra factor in the radiation integral, is developed, and the far field can be exactly reconstructed from the knowledge of approximately one sample per lobe (Shannon-Whittaker theorem applied at Nyquist rate).
Abstract: A new computational approach is presented which allows fast analysis of radiation from large reflector antennas. For an aperture a Fourier transform (FT) relationship does exist between far-field and aperture distribution. Accordingly, the far field can be exactly reconstructed from the knowledge of approximately one sample per lobe (Shannon-Whittaker theorem applied at Nyquist rate). The finite reflector curvature introduces an extra factor in the radiation integral so that the radiation integral is no longer a FT. In order to overcome this difficulty a new pseudosampling expansion, which explicitly takes into account the extra factor, is developed. For parabolic reflector the sampling functions are related to the Fresnel integrals, and the far field can be exactly reconstructed in terms of aperture far-field samples, which can be computed using the fast Fourier transform (FFT). Numerical computations and error analysis show the excellent performance of the method, which can be generalized to deal with arbitrary reflector surfaces and near-field evaluation.
29 citations
01 Nov 1981
29 citations
TL;DR: In this article, the authors used the Jacobi-Bessel 1/R^{P} series to determine the higher order terms of a Barrar-Kay 1/r^{p} expansion of the fields.
Abstract: Many useful applications exist for the efficient computation of Fresnel and near zone fields of large antennas. Even small antennas in beam waveguide systems must be evaluated in the Fresnel zone. Far zone fields computed from measured near zone measurements can be verified by both the measurement and the computation of the Fresnel zone fields. The authors start with the premise that the far field has been computed by a Jacobi-Bessel series. These results are used then to determine the higher order terms of a Barrar-Kay 1/R^{p} expansion of the fields. The leading term of the 1/R^{p} series is the far zone field. Classically, the higher order terms are found by repetitive differentiation, a laborious and often inaccurate procedure particularly since the 1/R^{P} series is slowly convergent-as D^{2}/R ( D is the diameter of antenna source). The approach of the authors via the Jacobi-Bessel 1/R^{P} series determines the higher order terms by simple algebraic recursion. The only restriction on the method is that it be used within the range of validity of the Fresnel small angle (FSA) approximation. However, since the Fresnel approximation is a second order approximation in terms of ( D/R ), the range of validity is quite large. This is demonstrated in detail. The method is applicable to reflector as well as aperture field sources.
27 citations
TL;DR: In this paper, an analysis of the behavior of reflector antennas loaded by a surface impedance along a peripherical rim is carried out in order to ascertain the possibility of improving their performance by such a loading technique.
Abstract: An analysis of the behavior of reflector antennas loaded by a surface impedance along a peripherical rim is carried out in order to ascertain the possibility of improving their performance by such a loading technique. Both single and dual (Cassegrain) reflector antennas are considered. It is shown that an effective control of the radiated field can be achieved by the proper choice of the loading characteristics. In the case of Cassegrain antennas, subreflector loading is sufficient to enhance copolar or crosspolar overall performance.
20 citations
TL;DR: The basic analytical and numerical characteristics of the Jacobi-Bessel series applied to the determination of the Fresnel and Fraunhofer fields radiated by planar apertures and reflector antennas are reviewed.
Abstract: This paper reviews the basic analytical and numerical characteristics of the Jacobi-Bessel series applied to the determination of the Fresnel and Fraunhofer fields radiated by planar apertures and reflector antennas. Only the final formulations are presented here and the reader is referred to the published papers by the authors for specific details. Many useful representative numerical results are generated to demonstrate the applicability of the technique.
15 citations
01 Oct 1981
TL;DR: In this paper, a reflector antenna trade-off study for a multi-beam airborne radiometer is described and two different types of plano-convex lens antennas are compared.
Abstract: A reflector antenna trade-off study for a multi-beam airborne radiometer is described. Two different types of plano-convex lens antennas are compared. Beam broadening characteristics of the antennas are examined and a novel conical scan arrangement introduced. The compatibility of different scanning and tracking techniques is examined.
6 citations
TL;DR: In this article, the diffracted wave field and the irradiance distribution for the case of Fresnel diffraction of a circular Gaussian wave diffracted by a Wood zone plate were investigated.
Abstract: The diffracted wave field and the irradiance distribution are found for the case of Fresnel diffraction of a circular Gaussian wave diffracted by a Wood zone plate.
5 citations
16 Jun 1981
4 citations
01 Mar 1981
TL;DR: In this paper, an algorithm for shaping offset dual reflector antenna surfaces is presented which uses small areas of optimally tilted conic sections reported by Mizugutch for starting up a numerical synthesis of reflector surfaces.
Abstract: Algorithms for shaping offset dual reflector antenna surfaces are presented which use small areas of optimally tilted conic sections reported by Y. Mizugutch for starting up a numerical synthesis of reflector surfaces. A new ray ratio squared method is described for the precise control of antenna aperture amplitude distributions.
3 citations
TL;DR: F Fresnel patterns for linear chirp functions are simply related to the single-slit pattern, developed for use as optical system design criteria.
Abstract: A rotated coordinate system is used to evaluate the irradiance distribution of a Fresnel diffraction pattern. Arbitrary diffracting objects are defined in a bounded input plane. Fresnel patterns for linear chirp functions are simply related to the single-slit pattern. Features of the single-slit pattern are developed for use as optical system design criteria.
01 Oct 1981
TL;DR: In this article, the authors describe a systematic procedure for the design of offset parabolic satellite frequency reuse antennas with multiple feeds, and the amplitudes and phases of the multiple feeds are optimized simultaneously at the two ends of the frequency band to satisfy coverage gain and isolation requirements.
Abstract: This paper describes a systematic procedure for the design of offset parabolic satellite frequency reuse antennas with multiple feeds. Launch vehicle size constraints and the coverage requirements determine the optimum reflector geometry and feed parameters. Then, the amplitudes and phases of the multiple feeds are optimized simultaneously at the two ends of the frequency band to satisfy coverage gain and isolation requirements. Sensitivity analysis of the coverage patterns to feed excitation variations is included in the overall design process.
16 Jun 1981
16 Jun 1981
05 Apr 1981
16 Jun 1981