Cassegrain antenna

About: Cassegrain antenna is a research topic. Over the lifetime, 3207 publications have been published within this topic receiving 28278 citations.

A generalized diffraction synthesis technique for high performance reflector antennas

Abstract: Stringent requirements on reflector antenna performances in modern applications such as direct broadcast satellite (DBS) communications, radar systems, and radio astronomy have demanded the development of sophisticated synthesis techniques. Presented in the paper is a generalized diffraction synthesis technique for single- and dual-reflector antennas fed by either a single feed or an array feed. High versatility and accuracy are achieved by combining optimization procedures and diffraction analysis such as physical optics (PO) and physical theory of diffraction (PTD). With this technique, one may simultaneously shape the reflector surfaces and adjust the positions, orientations, and excitations of an arbitrarily configured array feed to produce the specified radiation characteristics such as high directivity, contoured patterns, and low sidelobe levels, etc. The shaped reflectors are represented by a set of orthogonal global expansion functions (the Jacobi-Fourier expansion), and are characterized by smooth surfaces, well-defined (superquadric) circumferences, and continuous surface derivatives. The sample applications of contoured beam antenna designs and reflector surface distortion compensation are given to illustrate the effectiveness of this diffraction synthesis technique. >

Lateral-feed displacement in a paraboloid

Abstract: The beam shift and degradation of a paraboloidal reflector with an offset feed is analyzed by the scalar plane wave theory. Higher order coma terms are included with the feed at its optimum axial position. The beam characteristics for a tapered circularly symmetric illumination are presented. The range of validity of the approximate analysis is indicated.

Dual polarized dual band antenna

Abstract: An antenna system is described including a reflector antenna, responsive to radio frequency signals at a first frequency, having a first reflector surface, a second reflector surface and a Cassegrain feed. The antenna system further includes an array antenna having a plurality of antenna elements responsive to radio frequency signals having a second different frequency, wherein a center element is in a common location with the feed of the reflector antenna. With such an arrangement, an improved dual band antenna system is provided. By providing the center element of the array antenna in a common location with the feed of the reflector antenna, a dual band radio frequency antenna system is provided which is more compact with improved radiation characteristics than known similar configured antennas.

A Shared-Aperture Dual-Band Dual-Polarized Filtering-Antenna-Array With Improved Frequency Response

Abstract: In this paper, a novel dual-band dual-polarized array antenna with low frequency ratio and integrated filtering characteristics is proposed. By employing a dual-mode stub-loaded resonator (SLR) to feed and tune with two patches, the two feed networks for each polarization can be combined, resulting in the reduction of the feed networks and the input ports. In addition, owing to the native dual resonant features of the SLR, the proposed antenna exhibits second-order filtering characteristics with improved bandwidth and out-of-band rejections. The antenna is synthesized and the design methodology is explained. The coupling coefficients between the SLR and the patches are investigated. To verify the design concept, a C-/X-band element and a $2 \times 2$ array are optimized and prototyped. Measured results agree well with the simulations, showing good performance in terms of bandwidth, filtering, harmonic suppression, and radiation at both bands. Such an integrated array design can be used to simplify the feed of a reflector antenna. To prove the concept, a paraboloid reflector fed by the proposed array is conceived and measured directivities of 24.6 dBi (24.7 dBi) and 28.6 dBi (29.2 dBi) for the X-polarization (Y-polarization) are obtained for the low- and high-band operations, respectively.

Reconfigurable Folded Reflectarray Antenna Based Upon Liquid Crystal Technology

Abstract: A reconfigurable antenna based on the liquid crystal technology is presented in this paper. The antenna comprises a planar lower reflector with an incorporated feed at its center and a polarizing grid on top as an upper reflector. The lower reflector is utilized to collimate the beam and to twist the polarization. The polarizing grid selects the polarization for the transmission and reflects the orthogonally polarized waves toward the lower reflector. Combining reflector elements with a polarizing grid allows performing additional phase adjustment on the upper reflector for beam steering. Reconfigurability is maintained by the upper reflector, in which a liquid crystal mixture is used as a tunable substrate. The liquid crystal layer is tuned with a bias voltage configuration to obtain an appropriate phase adjustment for the beam steering. As a proof of concept, the beam steering capability of the antenna is demonstrated by steering the main beam to $-6^{\circ}$ , 0 $^{\circ}$ , and 6 $^{\circ}$ at 78 GHz. The measured gain at 78 GHz is 25.1 dB. The proposed antenna configuration is a promising candidate for reconfigurable, high-gain, low-profile, and low-cost antennas.