Showing papers on "Feed horn published in 1980"

Shaped reflector antenna analysis using the Jacobi-Bessel series

Abstract: The physical optics approximation is employed to derive the radiation integral for a doubly curved offset reflector antenna illuminated by an arbitrary source. A novel procedure is presented for expressing the radiation integral in terms of a summation of Fourier transforms of an "effective" aperture distribution which includes the effect of the curvature of the surface. The Jacobi-Bessel series is used to evaluate the Fourier transforms. The vector nature of the far-field pattern is studied by evaluating its three Cartesian components in a unified fashion. The rapid numerical evaluations of the expressions obtained are demonstrated via extensive test cases. In particular, the scattering characteristics of symmetric and offset parabolic, spherical, and shaped reflectors are studied in detail, and comparisons are made with other available data.

Combined radar and infrared scanning antenna

Abstract: An antenna system has a parabolic reflector mounted so that it points generally downwards and a primary aerial is located at the focus of that reflector. Waves from the primary aerial are reflected back by the parabolic reflector to a reflector plate through an aperture in which the primary aerial projects. Scanning in both elevation and azimuth is effected by movement of the reflector plate.

Circularly polarized feed for cylindrical parabolic reflector antennas

Abstract: The feed design described is a linear array of crossed dipoles above a ground plane. The radiation patterns of the longitudinal and the transverse dipoles are made equal by parallel longitudinal rods, referred to as beam forming rods or beam matching rods. When used as a circularly polarized feed for an offset parabolic cylinder antenna, aperture efficiencies (spillover included) as high as 0.89 are potentially available if the field distribution along the array is uniform. The beam patterns of the feed were computed both by the method of moments and the geometrical theory of diffraction and are compared with patterns measured on a model at 1.5 GHz. A method of matching the impedance for both linear polarizations is proposed using parallel impedance matching rods.

Corrugated horn radiator

Abstract: A corrugated horn radiator which includes a transition zone made up of a number of parts between the smooth-wall feed wave guide 1 having a cross-section which is constant and a horn radiator with regular periodic corrugations 10 with the depth of the corrugations being less than one-quarter wave length relative to the lowest frequency to be transmitted. The transition zone starting at the constant diameter feed wave guide comprises a first section which is conical shaped and then joins a second section which is cylindrical in shape and which serves as a phase drift space and then connects to a second conical smoothed walled portion and then connects to an exponential horn having a pair of corrugations with re-entrant ring-shaped ends (6, 7) which are narrower than the regular periodic corrugation structure 10. The pair of corrugations 6 and 7 connect with a corrugated transition section 8 which comprises a plurality of corrugations which have depths that become progressively less as they approach the regular corrugations 10 and wherein the apex angle of the transition portion 8 is greater than the apex angle of the regular corrugation portion 10. The corrugated horn radiator of the invention has good broad band characteristic and favorable broad band cross-polarization characteristics and the corrugated horn radiator can be employed as a horn antenna or as a feed horn for a Cassegrain or focus fed antenna.

High efficiency and low sidelobe design for a large aperture offset reflector antenna

Abstract: A design method giving high efficiency and low sidelobes is discussed for large aperture offset reflector antennas. A new reflector shaping technique using the subreflector and the beam waveguide reflector with the parabolic main reflector is proposed to simplify the main reflector manufacturing process. The effectiveness of the technique is confirmed by the model experiments. One problem with this reflector shaping technique is that the subreflector edge level cannot be controlled independently of the main reflector edge level. By investigating the relation between the gain reduction and the subreflector edge level, which affects the wide-angle sidelobe levels, the realizable characteristics of antennas are studied. In order to decrease the subreflector edge level without reducing the aperture efficiency, a technique using an extended reflector is also proposed. Its effectiveness is shown by theoretical and experimental investigations.

Dielectric-loaded trifurcated horn for H-plane stacked reflector feed array

Abstract: A waveguide horn is described which improves the efficiency of H-plane stacked horn array for reflector feeds. It makes use of dielectric loading for sharpening the H-plane pattern and trifurcation to reduce the large E-plane sidelobes. As a result, there is less energy loss in the spill over and more energy available for the secondary beam. Expressions for the horn radiation patterns are given. The computed patterns show good agreement with those measured.

Dual frequency aerial feed arrangements

Abstract: The invention provides a dual frequency aerial feed arrangement consisting of a main feed horn having on either side of its mouth ground plane members above which are mounted dipole radiators. The ground members are set back from the mouth of the horn and carry upstanding plates extending to a plane including the mouth of the horn the plates providing a corrugation effect with the corrugations aligned with the polarization of the dipole radiators.

Rotating dual frequency range antenna system

Abstract: Disclosed is an antenna system designed to operate in two frequency rangesimultaneously, namely S-band (1660 to 1700 MHz) and X-band (8500 to 9600 MHz). The system comprises two separate antennas which are conically scanned and share a common parabolic reflector within a radome. The S-band antenna is adapted for passive angle tracking and reception of radiosonde data by means of a balun fed dipole feed system which includes an offset hemispherical reflector which is rotated by a scan motor to provide conical scanning. The X-band antenna comprises an active feed system which includes a stationary feedhorn and a tapered dielectric lens which is coupled to the S-band hemispherical reflector and is rotated therewith about an axis through the vertex of the parabolic reflector. The tapered lens tilts the constant phase front of the X-band radiation pattern thereby producing a displaced phase center near the focus of the antenna to implement its respective conical scanning operation.

Offset Cassegrain Earth Station Antenna for the Japanese Domestic Satellite Communication System

Abstract: Offset reflector antennas have advantages for communication systems because they are not severely subject to blocking. Difficulties mainly arising from structual asymmetries have inhibited the realization of an offset reflector antenna with a large aperture for commercial use. This paper describes the design of an offset Cassegrain earth station antenna for the Japanese domestic satellite communication system. Antenna measurements showed 76 and 69 percent aperture efficiencies at 20 and 30 GHz, respectively, less than -20 dBi wide angle directivity and an 18 K noise temperature in operating conditions. Performances are far superior to conventional axisymmetrical earth station antennas. The antenna was reassembled on a telephone office building after the measurements. The antenna gain was reconfirmed there, using the sun as a radio frequency source. Experiments show that the earth station antenna and a terrestrial antenna can be placed on the same building without serious interference.

Reflector antenna profile measurement using ultrasound

Abstract: A method for the measurement of reflector antenna surface profiles requiring no mechanical contact is described. The technique consists of placing an ultrasonic transmitter at the reflector focus and measuring the phase over the whole of the reflector aperture. Profile errors of order ±0.1 mm have been measured.

Comparison of G/T between dual-reflector and primary-focus antennas

Abstract: Cassegrain operation of moderate-sized antennas at low frequencies often poses difficulties because of the large feed horn required. Primary-focus operation using a two-hybrid-mode feed horn is shown to give a G/T ratio close to that provided by classical Cassegrain operation using a single-hybrid-mode feed.

New technique for efficient pattern computation of aperture and reflector antennas

Abstract: A new and efficient technique for computing secondary patterns of antennas with known aperture distributions is described. The method is extendable to parabolic reflector antennas with given surface current distribution. The fast Fourier transform (f.f.t.) algorithm is used to compute the coefficients of expansion of a series representing the radiation pattern.

Center-fed parabolic reflector antenna cross polarization due to slightly right-left asymmetric feed patterns

Abstract: Slightly right-left (R-L) asymmetric feed pattern effects on a center-fed parabolic reflector antenna cross polarization have been described with some numerical computation examples, noting that measured feed patterns, both in the E plane and in the H plane, are generally not completely R-L symmetric and have a slightly different R-L field intensity which produces asymmetrical reflector surface currents. It is shown from the numerical computations that even a slight feed asymmetry, in both amplitude and phase, gives rise to a cross polarization in the secondary prinicpal planes and that, in particular, phase R-L asymmetry incurs two-dimensional movement of principal- and cross-polarized patterns resulting in the rapid increase of principal-plane cross polarization as well as the maximum cross polarization, principal-pattern beamshift, and the sidelobe variations.

Low sidelobe precise beam aspect ratio scalar horns

Abstract: A new design method for developing either linearly or circularly polarized low sidelobe corrugated sectoral horn antennas is described. These antennas may be designed to provide constant beam aspect ratios (BAR's) ranging from 2:1 to 5:1. Such performance is achieved over bandwidths of up to 21 percent for dual-linear polarization and 17 percent for circular polarization. Potential applications include use in communication satellite reflector systems where beam shaping, frequency reuse, or high adjacent beam isolation is required. Selecting aperture phase distribution rather than simply minimizing aperture phase error is the key to obtaining these results. Mechanical design and performance data are presented to facilitate fabrication of antennas that satisfy a wide range of performance requirements.

Measuring Techniques for the Calibration of Standard Gain Horn Antennas

Abstract: : The main objective of this study is to accurately determine the far- field gain of microwave horn antennas from measured, on-axis, near-field coupling. In order to determine the gain, it is important to first locate the amplitude center of each horn antenna. Two methods of determining far-field horn antenna gain are presented. Both involve determining the amplitude center location. The first method involves only simple calculations based on measured coupling and Friis' transmission formula. The second method is more complicated but results in more accurate gain calculations, especially for larger horns. This second method is based on measured coupling, Friis' transmission formula, and theoretical near-field corrections. Included is a chapter on accurate coupling measurement techniques as well as a chapter on on principal plane radiation patterns of horn antennas.

A prototype DSN X/S-band feed: DSS 13 application status

Abstract: A prototype X/S-band common aperture horn feed for future use at various DSN sites and the Network Consolidation Program is discussed. The final design and fabrication of the second generation feedhorn and combiner is dealt with. The results of the measurements obtained with the second generation, full scale feed configuration are presented.

Reflector radiation pattern from planar near-field measurements of array feed

Abstract: High gain shaped beam antennas for satellite frequency reuse applications are almost exclusively obtained by the use of complex multielement feed arrays to provide pattern control in conjunction with offset reflectors to remove blockage effects. In the design of complex multielement feed arrays for offset reflectors, the element excitations are usually synthesized using the isolated element properties. Proper performance of the array often requires that these theoretical excitations be modified to account for the effects on the feed elements due to the array environment. Near-field planar probing of the fields of the feed array have been found to provide an efficient and accurate method of predicting the secondary performances, including cross polarization and axial ratio. The nearfield measurement technique, moreover, provides an extremely effective method of determining the element performance and for determining the required compensation for desired antenna performance.

Reflecting mirror antenna

Abstract: PURPOSE:To decrease the setting error of the antenna caused by the rotation of the azimuth and then realize the common use of the multifrequency band by setting the two sets of beam transmission systems which are symmetric to the shaft of the azimuth. CONSTITUTION:Central axes 14a and 14b of feed horns 7a and 7b are in agreement with azimuth shaft 10. Flat plate type filters 11a and 11b cross to each other, and the cross line crosses vertically to shaft 9 of angle of elevation. Two sets of beam transmission systems are provided symmetrically to shaft 10. In case the waves of two frequency bands featuring the central frequencies F1 and F2 (F1>>F2) enter main reflecting mirror 1, filter 11a reflects the wave of the frequency band of frequency F1 and gives transmission to the wave of F1. Filter 11b reflects the wsve of F2 and gives transmission to the wave of F1. The wave of F2 is received and branched in the transmission route of main reflecting mirror 1 secondary reflecting mirror 2 filter 11a converging reflecting mirrors 4a, 5a and 6 feed horn 7a.

A measurement technique for modeling the effects of feed support struts on large reflector antennas

Abstract: A measurement technique is described in which frequency scaled models of struts are placed in the near-field region of an offset reflector. In this compact range environment the excitation of the strut model is by plane waves, as would be encountered in the axisymmetrical reflector situation. Far-field radiation patterns are recorded, with and without the strut model in place, and, because of the low sidelobe levels associated with offset reflector antenna systems, it is possible to isolate the far-field response of the strut model. This technique is particularly useful for determining the real effects of structures that are difficult to analyze mathematically, such as latticed struts or metallic geodetic radomes.

Shaping beam antenna

Abstract: PURPOSE:To simplify a feed system and also to manufacture an antenna easily by arranging a radio wave lens, composed of several lenses changing an arrival spherical wave in phase center point, between a feed horn and main reflex mirror. CONSTITUTION:On the Z axis of main reflex mirror 1 composed of one part of a paraboloid which has a rotational symmetric axis on the Z axis and its focus at point F, radio wave lens 10 consisting of partial lenses 11 and 12 and feed horn 2 with its phase center point of a radiation spherical wave at point P are both arranged. Among spherical waves radiated from focus P, waves having penetrating partial lens 11 strike main reflex mirror 1 as spherical waves centering on point F11 and those penetrating lens 12 as waves centering on F12; and they are reflected by main reflex mirror 1 and advance along axes 26 and 27 inclined at constant angles (PSI11) and (PSI12) to the Z axis respectively.

Efficient Small-Size Antenna for FM Radio Reception

Abstract: Functions required for the FM radio receiving system including antenna are mainly interference rejection and sensitivity, and are now demanded to be more improved in the face of an increase of FM broadcasting stations.

Offset J-hook reflector antenna

Abstract: This specification discloses a microwave antenna system using an offset J-hook feed to achieve low sidelobe energy level over the entire radiation space from an electrical circular reflector antenna. An electromagnetic horn is positioned along the central axis of symmetry of a parabolic reflector. A waveguide feed is coupled to the horn and intersects the reflective surface at a position offset from the axis of symmetry.

Performance of offset paraboloid reflectors with offset matched feeds

Abstract: The performance of offset reflector antennas with offset matched feeds is investigated. Mathematical expressions for the reflector pattern calculations are presented, and both scalar aperture and vector current methods are used to compute the patterns. It is found that the scalar aperture method can predict the co-polar patterns accurately, but always yields lower cross-polarization levels than the vector current method. The cross-polarization of the reflector for various feed displacements and polarizations is also investigated. The results indicate that displacing the feed along the reflector axis of symmetry yields lower cross-polarizations and, in particular, when the feed displacement is towards the reflector side, the level of the cross-polarization decreases initially with the feed displacement.

Phase center location of a paraboloidal reflector antenna with an axially defocused feed

Abstract: Formulas for determining phase center locations in the principal E and H planes of a paraboloidal reflector antenna with an axially defocused feed have been developed. The relations between the phase center location and various antenna parameters and the distance from the source to the focus are studied and presented in graphical forms. It has been found that, in general, phase center locations change significantly with the amount of defocusing.

Multi-mode horn antenna simulation

Abstract: Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR) This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes A computer program for the radiation field expressions using the summation of waveguide radiation modes is described The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown The multimode horn antenna provides a low noise feed suitable for radiometric applications