Showing papers on "Feed horn published in 1998"

Dual reflector microwave antenna

Abstract: A dual-reflector microwave antenna comprises the combination of a paraboloidal main reflector having an axis; a waveguide and dual-mode feed horn extending along the axis of the main reflector, a subreflector for reflecting radiation from the feed horn onto the main reflector in the transmitting mode, and a shield extending from the outer edge of the main reflector and generally parallel to the axis of the main reflector, the inside surface of the shield being lined with absorptive material for absorbing undesired radiation. The subreflector is shaped to produce an aperture power distribution that is substantially confined to the region of the main reflector outside the shadow of the subreflector. The support for the subreflector is preferably a hollow dielectric cone having a resonant thickness to cause energy passing through said cone to be in phase with energy reflected off of said cone so as to achieve phase cancellation.

Reflector antenna with improved return loss

Abstract: An improved reflector antenna with far improved return loss than prior art subreflector antennas is disclosed herein. The invention uses a circular waveguide antenna feed (1) employing a non-planar subreflector (5) having a radial cavity which reflects the energy from the waveguide onto a rotationally symmetrical main reflector (1). The dimensions of the feed tube, the subflector, and the connection (3) between them are chosen to make the total reflection back into the feed tube very close to zero. The dimensions of the antenna feed are also chosen such that its radiation pattern has an amplitude null along the antenna feed axis. This further improves return loss by minimizing the amount of energy from the main reflector that gets directed back into the feed tube. An alternate embodiment features a feed radiation pattern with an asymmetric amplitude taper for improvement of the sidelobe envelope in a preferred plane.

Designing axially symmetric Cassegrain or Gregorian dual-reflector antennas from combinations of prescribed geometric parameters. 2. Minimum blockage condition while taking into account the phase-center of the feed

Abstract: For pt.1 see ibid., vol.40, no.2, p.76-82 (1998). An easy procedure to design classical Cassegrain or Gregorian dual-reflector antennas has been presented in Granet (1998). This procedure allows the antenna designer to fully define the antenna geometry with different sets of input parameters, depending on the requirements of the antenna size and its performance. In this paper the conditions derived in Granet are extended to take into account the phase-center position of the feed, to achieve the minimum-blockage condition. This procedure can be used as the starting point of a synthesis procedure, where both main reflector and subreflector are shaped to create the desired aperture-field distribution.

Multiband ring focus antenna employing shaped-geometry main reflector and diverse-geometry shaped subreflector-feeds

Abstract: A multiband, shaped ring focus antenna architecture employs only a single or common main reflector, that is shaped such that it can be shared by each of a pair of interchangeable, diversely shaped close proximity-coupled, subreflector-feed pairs designed for operation at respectively different spectral bands. The operational band of the antenna is changed by swapping out the subreflector-feed pairs. Placement of the shaped subreflector in close proximity to the feed horn reduces the diameter of the main shaped reflector relative to a conventional ring focus structure, so as to facilitate installation within a constrained space facility, such as a shipboard-mounted satellite communication system.

Aperture-coupled microstrip antennas using reflector elements for wireless communications

Abstract: The design advantages provided by aperture-coupled microstrip patches can be very useful in wireless communications applications. A way to improve the front-to-back ratio is to place a microstrip antenna element behind the aperture as a reflector. Proximity coupling between the feed line and the reflecting element is negligible due to the thick foam substrate used, allowing use of the reciprocity method of analysis. Also, the directive patch elements are shielded from the reflector by the ground plane. Therefore, only interactions between the reflector and the aperture need to be modeled, resulting in a simple analysis. For aperture-coupled patch designs with a front-to-back ratio of 10 dB or greater, the introduction of a reflecting element has a negligible effect on the input impedance of the antenna. Therefore, a reflector element can readily be incorporated into existing designs.

Lens antenna with tapered horn and dielectric lens in horn aperture

Abstract: A lens antenna having high antenna efficiency, low sidelobe levels, and that is easily assembled. The lens antenna includes a first horn made of a metallic conductor, a second horn made of a high-frequency absorbing plastic material, and a lens for controlling the power distribution at an aperature of the horn. Screws may be used to assemble the first horn, the second horn, and the lens. Though some of the microwave signals input through the circular waveguide of the first horn are reflected on the surface of the lens, most of the microwave signals are absorbed by the second horn. Moreover, because no wave absorber is bonded to an inner wall of a conical horn, nothing screens the microwave signal, the power density distribution at the aperture of the lens is not disrupted. Therefore, it is possible to obtain a desired power density distribution.

Micromachined monolithic reflector antenna system

Abstract: A micromachined reflector antenna system is integrated onto a substrate by firstly etching a reflector aperture surface defining a dish cavity in an oxide layer and secondly rotating a hinge over the reflector aperture surface with the hinge being used as the reflector central feed. The micromachined reflector antenna system can be made with an array of reflector antennas and integrated onto a single substrate with front end receiver circuits operating as a high frequency receiver on a chip with reduced size and cost and operating at hundreds of GHz.

Satellite receiving dish feed horn or LNB cover

Abstract: A protective cover for a satellite receiving dish feed horn or LNB mounted on a support is disclosed. The cover comprises a top, sides and a back, the top and sides each having front and back edges, a forwardly and downwardly directed projection extending from the front edge of the top, and means to fasten the cover to the support or feed horn, such that the cover protects the feed horn or LNB from precipitation while not impeding signal reception.

Broadband omnidirectional microwave parabolic dish--shaped cone antenna

Abstract: An omnidirectional microwave antenna comprises a paraboloidal reflector disposed above the ground and facing downwardly with a substantially horizontal aperture and a substantially vertical axis. A vertically oriented feed horn is located below the paraboloidal reflector on the axis of the paraboloidal reflector and has a phase center located near the focal point of the paraboloidal reflector. A conical reflector having a shaped reflecting surface defined by the parameters of a mathematical equation extends downwardly away from the periphery of the feed horn for reflecting radiation received vertically from the paraboloidal reflector in a horizontal direction away from the conical reflector, and for reflecting horizontally received radiation vertically to the paraboloidal reflector. A radome extends downwardly from the outer periphery of the paraboloidal reflector and includes an absorber material for absorbing radiation propagated laterally from the feed horn and the conical reflector above the aperture of the feed horn.

A Low-Sidelobe, High Frequency Corrugated Feed Horn for CMB Observations

Abstract: We have produced a prototype broadband, low-sidelobe conical corrugated feed horn suitable for measurements of the Cosmic Microwave Blackground (CMB) radiation in the frequency band 120–150 GHz. The antenna is a first prototype for the Low Frequency Instrument array in ESA's PLANCK mission, a space project dedicated to CMB anisotropy mesurements in the 30–900 GHz range. We describe the fabrication method, based on silver electro-formation, and present the two-dimensional antenna beam pattern measured at 140 GHz with a milimeter-wave automated scalar test range. The beam has good symmetry in the E and H planes with a far sidelobe level approaching –60 dB at angles ∼ 80°. An upper limit to the return loss was measured to be –21 dB.

Antenna feed having electrical conductors differentially affecting aperture electrical field

Abstract: A receiving antenna includes a parabolic reflector and a feed horn. The feed horn includes an electrically conductive wall with an edge forming an aperture. The feed horn further includes a plurality of electrical conductors that extend from the edge to the center of the feed horn in a substantially coplanar relationship with the aperture. Each of the electrical conductors differentially affect a first polarized electrical field perpendicular to the edge adjacent the electrical conductor and a second polarized electrical field parallel to the edge adjacent the electrical conductor. In this manner, the electrical conductors can be configured to reduce the effective aperture of the feed horn in a plane, so that a first polarized horn radiation pattern produced by the feed horn can be circularized. The electrical conductors with respect to a vertical plane preferably match the electrical conductors with respect to a horizontal plane, so that first and second polarized horn radiation patterns produced by the feed horn can be simultaneously circularized. Another receiving antenna includes a splash plate and a feed horn that respectively include opposing edges that form an annular aperture. The feed horn further includes a plurality of electrical conductors that extend from the feed horn edge towards the splash plate edge in a coplanar relationship with the aperture. Again, the electrical conductors can be configured to reduce the effective width of the annular aperture in a plane, so that a first polarized horn radiation pattern produced by the feed horn can be circularized, while at the same time a second polarized horn radiation pattern produced by the feed horn can be circularized.

Antenna feed having centerline conductor

Abstract: An antenna feed horn assembly includes a circular feed horn having an electrically conductive wall with an edge defining a circular aperture. The antenna feed horn assembly further includes a circular waveguide mounted to the base of the circular feed horn and including an endplate. An cylindrical rod extends from the center of the endplate towards the center of the feed horn aperture along a longitudinal axis of the antenna feed horn assembly to minimize undesired reflections produced by transitions between electrically conductive material and non-electrically conductive material or dielectric within the antenna feed horn assembly. An antenna feed horn assembly can also include a splash plate opposite the endplate, the center from which another cylindrical rod extends towards the center of the endplate along the longitudinal axis of the antenna feed horn assembly to further minimize undesired reflections.

On-vehicle radar

Abstract: When a transmitted and received radio wave is scanned, even if, for example, a large vehicle is running on an adjacent lane, a preceding vehicle running on the same lane as an own vehicle can be sensed and tracked continually. An on-vehicle radar comprises a transmitter receiver 6 for transmitting and receiving a radio wave with a relatively high frequency, and a signal processor 10 calculating a relative distance to an object and a relative velocity of the object on the basis of a radio wave transmitted by the transmitter receiver, reflected from the object, and received by the transmitter receiver. The transmitter receiver controls the power of a transmitted radio wave so that when a radio wave is to be transmitted in any transmission direction other than a specified transmission direction, the power of the transmitted radio wave will be made lower than that of a radio wave to be transmitted in the specified transmission direction, or even if the power of a received radio wave is larger than a given value, the power of the transmitted radio wave will not be decayed, and that when a radio wave is to be transmitted in the specified transmission direction, if the power of a received radio wave is larger than the given value, the power of the radio wave transmitted by the transmitter receiver will be decayed.

SABOR: description of the methods applied for a fast analysis of horn and reflector antennas

Abstract: The program presented in this paper is intended to provide a valuable aid for teaching antennas to electrical engineers, and to provide fast and accurate pre-designs for professionals. This paper covers the theory and numerical techniques used in SABOR. In summary, this program computes the radiated field of an aperture antenna (horn or reflector), using a common engine based on the Gauss-Legendre quadrature method for evaluating the radiation integrals. For horn, the aperture fields are the usual dominant modes of the feed waveguide, with a quadratic phase correction. For reflectors, the aperture fields are computed using geometrical optics ray tracing from the feed horn. Also, equivalent-reflector concepts are applied for dual-reflector antennas. The paper includes some examples to demonstrate the most important features of the program.

Shaped compact dual reflector antenna for Ku-band satellite pico-terminals

Abstract: Pico-terminals for digital communications satellite systems need compact reflector antennas with a high aperture efficiency but with a controlled side lobe level. Shaped reflectors with an also shaped splash-plate meet both conditions satisfactorily. Such a solution was selected for the antenna of the remote user terminal of a CDMA satellite system (PRODAT project). This paper discusses its design and features.

Calculation of phase centers of feeds for reflectors when the phase variations are large

Abstract: The aperture efficiencies of classical symmetrical front-fed or Cassegrain reflector antennas can be factorized in different sub-efficiencies. Of these, the phase efficiency is the only one which depends on the location of the feed relative to the focal point of the reflector, provided the reflector is in the far-field of the feed. We present an improved formula for calculating the location of the phase center which is valid also when the radiation field of the feed has large phase variations. The new formula is applied to two different versions of the hat feed.

Reflector antenna for analog or digital mobile telephone

Abstract: A rod or dipole antenna (2) has a metallic reflector for receiving and emitting radio waves. A planar or convex radio wave reflector (1) is arranged inside or on the rear side of the telephone, and screens the radio waves emitted from the antenna in a certain angular range alpha, while having a directionality in the remaining angular region of 360 degrees minus alpha for transmitting and receiving. The reflector may by made by metalising the rear of the telephone housing.

Measurements of a new Gaussian profile corrugated horn antenna for millimeter wave applications

Abstract: The measurements results of a new design of corrugated horn antenna following the Gaussian expansion are presented in this paper. The performance of two corrugated horn antennas of this kind was verified in the ESTEC Compact Antenna Test Range (CATR) (Canales and Gonzalo, 1997). Very high agreement between measured and predicted results is round.

Primary radiator for parabolic antenna feeding

Abstract: PROBLEM TO BE SOLVED: To provide a primary radiator for parabolic antenna feeding, whose symmetry on the patterns of a face E and a face H in a radiation characteristic is satisfactory, which satisfies the request for characteristics, such as good cross polarized wave characteristic, and a reduced manufacture cost. SOLUTION: In a primary radiator for parabolic antenna feeding, a circular coaxial waveguide 2 having a metallic coaxial bar 5 in the direction of a center axis and transmitting a microwave and a conic flare part 3 connected to the circular coaxial waveguide 2 are installed, and a feed horn 1 which converts a microwave reflected from a parabolic antenna to a transmission mode in the waveguide is provided. The metallic coaxial bar 5 of the circular coaxial waveguide 2 is extended to the flare part 3 of the feed horn 1. COPYRIGHT: (C)1999,JPO

Shaped subreflector for offset Gregorian reflector antenna with a paraboloidal main reflector

Abstract: The shaped dual offset reflector antenna configuration is considered to yield the best radiation pattern performance for FSS ground stations operating in a small angle satellite spacing environment, where the present trend is a continuous tightening of off-axis radiation levels specifications. When properly designed and fitted with a low cross-polarization primary feed, the shaped dual offset reflector antenna radiation pattern can easily meet the present ITU-R recommendation, achieving simultaneously high aperture efficiencies, above 90%, and low levels for the cross-polarization peaks in the azimuth radiation pattern plane. However, widespread utilization of this configuration is still curbed by the higher manufacture costs. In this paper, the possibility of reducing the manufacture costs for the dual offset configuration is explored by utilizing the parabolic offset reflector as the main reflector, and shaping only the subreflector. This solution can be very cost reduction effective, particularly for manufacturers that already have a highly diversified production of single offset antennas. Selected reflectors could then be easily utilized as the main reflector in a dual offset design fitted with a suitably shaped subreflector.

A large deployable antenna with tension truss scheme and its electrical performances

Abstract: A large deployable antenna of 10 m maximum diameter was successfully launched and deployed in space aboard the satellite Halca in February, 1997. The main reflector is composed of a novel deployment scheme of tension truss. The parabolic surface is eventually approximated by triangular facets. The operating frequencies are 1.7 GHz, GHz, and 22 GHz. This paper describes the outline of the antenna emphasizing the measures against the cables entangling and the electrical performances.

Quasi optic lens antenna with corrugated feed horns

Abstract: A quasi-optic lens antenna with corrugated feed-horns in the balanced hybrid mode is investigated here using Gaussian beam-mode analysis. The relationships between beam parameters and geometric parameters of the horns and lens are given. Depending on required highest gain, low sidelobes or truncation, the optimal locations of the lens relative to the horns can be determined.

Transmission capacity of a broadband wireless radio link

Abstract: The transmission performance of a mobile/wireless broadband digital radio system, using the 60 GHz band, is evaluated for different antenna configurations in two indoor scenarios. It is shown that for the same equalization effort the maximum achievable carrier bit rate (CBR) strongly depends on the antenna configuration. A CBR of 40-50 Mbit/s in a medium size room and 20 Mbit/s in a large room using biconic horn antennas at the mobile terminal (MT) and at the base station transceiver (BST) is achievable, while this limit increases up to 100 Mbit/s when using two horn antennas located in the two narrower lateral walls of the room. Moreover, a simple method to estimate the maximum CBR based on the channel time dispersion is presented. Simulation results for several MT positions along the rooms are presented and discussed.

SABOR: a fast analysis tool for horn and reflector antennas

Abstract: SABOR (software de analisis de bocinas y reflectores) is an antenna-analysis approach for the computation of horn- and reflector-antenna performance. The program covers and expands topics already developed with other software. The program can analyze almost any kind of horn (E and H pyramidal horns, circular horns, corrugated horns). The current configuration of SABOR can also analyze centered and offset parabolic reflectors, dual-offset Cassegrain and Gregorian reflectors, and centered Cassegrain systems. For feeding reflectors, the program allows use of the classical cos/sup q/ pattern and any of the horn mentioned above. Usage of real horns improves the accuracy of computed efficiencies and the simulation of the cross-polar radiation.

Lnb device integrated with feed horn

Abstract: PROBLEM TO BE SOLVED: To facilitate the miniaturization of the low noise frequency converter LNB integrated with a feed horn and to reduce the cost. SOLUTION: A feed horn mount 2 is formed to a face of a tip of a synthetic resin made arm 1 toward a parabolic reflecting mirror which is projected in front of the parabolic reflecting mirror, a feed horn 3 formed by pressing a metallic plate is fitted to the mount 2, a screw 6 is inserted to each of holes made to the feed horn 3 and throughholes made to the feed horn mount 2 and threaded to each of lugs 5 placed at both sides of a case of the LNB 4 on the other side of an arm 1 so as to fasten the feed horn 3 and the case of the LNB 4 to the arm 1 and also to take electric continuity between the feed horn 3 and the case of the LNB 4.

Electronic monitoring system especially for small objects

Abstract: The system includes a transportable radio receiver (3) with a display and a transportable transmitter (2) which communicates with the receiver. The radio receiver is adjustable proportionally to the distance between transmitter and receiver with respect to the radio signals received from the transmitter. Preferably, the transmitter is adjustable proportionally to the distance between transmitter and receiver with respect to the radio signals received by the receiver. The receiver has a periodically operating circuit, which activates the display when the radio signal of the transmitter was not received.

Method for reducing cross-polar degradation in multi-feed dual offset reflector antennas

Abstract: A unique feed structure for improving the cross-polarization performance of a reflector antenna system is disclosed. According to the present invention, the feed structure is an array including a number of feeds, which are rotated in a predetermined fashion to yield superior cross polarization performance of the antenna system. The array feed in the center of the feed structure is positioned approximately in the focus of the antenna reflector. The array feeds located on the y-axis are slightly rotated in either a clockwise or a counter-clockwise manner. The magnitude of the rotation is proportional to the distance of the feeds from the x-axis along the y-axis. The rotation of the feeds yields significant performance in cross polarization performance, while having little or no co-polarization effect.

A transmitter that selectively polarizes a radio wave

Abstract: A transmitter provides a radio wave with selectable polarization. The transmitter includes antenna feeds that generate orthogonal radio waves having non-linear polarizations that corresponds to the selectable phase relationships of a first and a second modulating signals. A spacial combination of the non-linear radio waves to produce a linearly polarized radio wave that has an orientation corresponding to a selected phase relationship.

Feed development for advanced Satcom RX-antenna application

Abstract: The paper presents the results of the feed development for the Advanced Satcom Rx-antenna. Two design variants have been developed and described in this paper. The first feed design was used to illuminate a dielectric lens antenna, whereas the second is compatible with a multiple reflector antenna system. Both antenna concepts require the use of a feed cluster. A 19-element feed cluster was designed, built and tested for the dielectric lens. A single feed chain was developed for the reflector system. The feed design issues, as well as the measured results are presented in the paper. Excellent feed performance is demonstrated.

Modeling of blockage effects in axi-symmetric dual reflector systems

Abstract: The simplicity of axi-symmetric reflector systems has led to their use in many terrestrial and satellite communications, especially in pencil beam applications. The major short-comings of a symmetric reflector are the degradation from the blockage and the uncertainty in predicting the degradation very accurately. This uncertainty can be more pronounced in shaped beams used in satellite applications. In a single reflector system with a prime-focus feed, the blockage effects are very small due to the small size of the feed horn. However, in a dual reflector system with a subreflector and the primary feed, the blockage effects can be appreciable due to the relatively large size of the subreflector. The three primary components to the blockage are: a) the blockage of the subreflector radiation by the feed. b) The blockage of the main reflector radiation by the subreflector. c) The blockage of the main reflector radiation by the supporting structure for the subreflector (usually 3 or 4 struts). An accurate and simple technique for determining the blockage effects is presented in this paper. The method does not require any calculation of shadow areas and so is a uniform technique which is valid over all regions of the radiation pattern.