Showing papers on "Feed horn published in 2011"

Lenses for Circular Polarization Using Planar Arrays of Rotated Passive Elements

Abstract: A planar array of passive lens elements can be phased to approximate the effect of a curved dielectric lens. The rotational orientation of each element can provide the required phase shift for circular polarization. The array elements must be designed so that the hand of circular polarization changes as the electromagnetic wave passes through the lens. An element is presented that is based on an aperture-coupled microstrip patch antenna, and two lenses are designed. Each lens has a diameter of 254 mm and contains 349 elements. The elements have identical dimensions but the rotational orientation of each element is selected to provide a specific lens function. The first lens is designed to collimate radiation from a feed horn into a beam pointing 20° from broadside. At 12.9 GHz the aperture efficiency is 48%. The second lens acts as a Wollaston-type prism. It splits an incident wave according to its circular polarization components.

A High-Performance Dual-Mode Feed Horn for Parabolic Reflectors with a Stepped-Septum Polarizer in a Circular Waveguide [Antenna Designer's Notebook]

Abstract: This article describes a circularly polarized feed horn designed to feed shallow, prime-focus or offset-fed parabolic reflectors. Both circular polarization senses are available at two individual coaxial ports. The design provides good circularity, a very clean radiation pattern with excellent sidelobe suppression, outstanding isolation between ports, and needs no adjustments. An L-band example is presented, including both simulation and experimental results. The complete set of dimensions, not previously found in the literature for septum polarizers in circular waveguide, is provided for the practical engineer who desires to duplicate or scale this feed horn to other frequencies.

Stereolithographed MM-wave corrugated horn antennas

Abstract: We describe the fabrication and testing of corrugated horn antennas designed for operation in the W-band (75–110 GHz). These antennas are constructed using stereolithography and plated with copper. They demonstrate return loss < −20 dB across most of the band and main beam patterns nearly identical with electroformed horns of the same design.

Multiple flare-angle horn feeds for sub-mm astronomy and cosmic microwave background experiments

Abstract: Context. The use of large-format focal plane imaging arrays employing multiple feed horns is becoming increasingly important for the next generation of single dish sub-mm telescopes and cosmology experiments. Such receivers are being commissioned on both general purpose, common user telescopes and telescopes specifically designed for mapping intensity and polarisation anisotropies in the cosmic microwave background (CMB). Telescopes are currently being constructed to map the CMB polarisation that employ hundreds of feeds and the cost of manufacturing these feeds has become a significant fraction of the total cost of the telescope. Aims. We have developed and manufactured low-cost easy-to-machine smooth-walled horns that have a performance comparable to the more traditional corrugated feed horns that are often used in focal plane arrays. Our horns are much easier to fabricate than corrugated horns enabling the rapid construction of arrays with a large number of horns at a very low cost. Methods. Our smooth walled horns use multiple changes in flare angle to excite higher order waveguide modes. They are designed using a genetic algorithm to optimise the positions and magnitudes of these flare angle discontinuities. We have developed a fully parallelised software suite for the optimisation of these horns. We have manufactured prototype horns by traditional electroforming and also by a new direct drilling technique and we have measured their beam patterns using a far-field antenna test range at 230 GHz. Results. We present simulated and measured far-field beam patterns for one of our horn designs. They exhibit low sidelobe levels, good beam circularity and low cross-polarisation levels over a fractional bandwidth of 20%. These results offer experimental confirmation of our design technique, allowing us to proceed confidently in the optimisation of horns with a wider operational bandwidth. The results also show that the new manufacturing technique using drilling is successful, enabling the fabrication of large format arrays by repeatedly drilling into a single aluminium plate. This will enable the construction of focal plane arrays at a very low cost per horn. Conclusions. We have developed a new type of high performance feed horn that is fast and easy to fabricate. Having demonstrated the efficacy of our horn designs experimentally, we are building and testing a prototype focal plane array of 37 hexagonally close packed horns. This prototype array will be an important step towards building a complete CMB mapping receiver using these feed horns.

Circular polarization feed with dual-frequency OMT-based turnstile junction

Abstract: This paper presents the development of a circular-polarization feed comprising an OMT (orthomode transducer) and a corrugated horn. The OMT works in two frequency bands with polarization redundancy providing right- and left-hand circular polarizations (RHCP and LHCP). The operation is done at the typical communication transmitting and receiving C-band frequencies. The feed horn is used to illuminate a reflector antenna, the surface of which is shaped to provide domestic, regional, or global coverage from a geostationary satellite. The challenge in the design consisted in obtaining a mechanically compact feed assembly with low mass, while being compliant with the specified electrical performance requirements, since this device was developed for a satellite application.

W-band prototype of platelet feed-horn array for CMB polarisation measurements

Abstract: We present the design and performance of a 2x2 prototype array of corrugated feed-horns in W-band. The module is fabricated using a so-called "platelet" technique by milling Aluminum plates. This technique is suitable for low-cost and scalable high performance applications. Room temperature Return Loss measurements show a low (<-30 dB) reflection over a 30% bandwidth with a maximum matching of -42 dB at 100 GHz for all four antennas. Beam pattern measurements indicate good repeatability and a low (-25 dB) sidelobe and crosspolarisation levels. This work is particularly relevant for future Cosmic Microwave Background polarisation measurements, which require large microwave cryogenic detector arrays coupled to high performance corrugated feed horns.

L-Band Feed Horn and Orthogonal Mode Transducer for the KAT-7 Radio Telescope

Abstract: The design, simulation and measured performance of a broad bandwidth L-band wide flare angle corrugated conical horn and its orthogonal mode transducer are presented. The feed horn is used on prime focus parabolic reflector antennas of a seven-element interferometer, which is part of the Karoo Array Telescope project. The horn was designed to maximize the sensitivity of the radio telescope over a frequency band of 47.6% relative bandwidth. The orthogonal mode transducer design has low insertion and transmission losses and good isolation, and because of its compact size requires a very small cryogenic cooling system.

W-band prototype of platelet feed-horn array for CMB polarisation measurements

Abstract: We present the design and performance of a 2x2 prototype array of corrugated feed-horns in W-band. The module is fabricated using a so-called ``platelet'' technique by milling Aluminum plates. This technique is suitable for low-cost and scalable high performance applications. Room temperature Return Loss measurements show a low ( < −30 dB) reflection over a 30% bandwidth with a maximum matching of -42 dB at 100 GHz for all four antennas. Beam pattern measurements indicate good repeatability and a low (-25 dB) sidelobe and crosspolarisation levels. This work is particularly relevant for future Cosmic Microwave Background polarisation measurements, which require large microwave cryogenic detector arrays coupled to high performance corrugated feed horns.

Performance of the ALMA Band 10 SIS Receiver Prototype Model

Abstract: We have developed a dual polarization prototype model of the Atacama Large Millimeter/submillimeter Array (ALMA) Band 10 (787-950 GHz) receivers. The front-end optics comprises a pair of ellipsoidal mirrors, a wire grid, and two corrugated feed horns. A waveguide mixer block is attached to each feed horn in which a mixer chip employing Nb/AlOx/Nb juncions and NbTiN/SiO2/Al microstrip tuning circuits is mounted to a WR-1.2 full-height waveguide. A local oscillator (LO) signal receiving horn and a waveguide 10-dB LO coupler are integrated in the block to provide the LO signal to the mixer chip. A fixed-tuned multiplier with a diagonal horn located at the 110-K stage is used to transmit the LO power. The LO signal is then quasi-optically coupled to the mixer receiving horn. A very wide intermediate frequency (IF) system with a bandwidth of 4-12 GHz is employed. The receiver demonstrated double sideband (DSB) noise temperatures of about 160 K (4hν/kB) without any correction for loss in front of the receiver at the LO frequency of 834 GHz at an operating physical temperature of 4 K.

Elliptically Shaped Quad-Ridge Horn Antennas as Feed for a Reflector

Abstract: Quad-ridge horn antennas of various geometries are considered as possible candidates for a wideband reflector antenna feed. It is demonstrated that shaping the sidewalls of the ridge horns significantly improves the radiation characteristics of the horns. The conical quad-ridge horn with an elliptically shaped sidewall shows the most promise as a wideband reflector antenna feed. The radiation patterns are rotationally symmetric, and the 10-dB beamwidth is reasonably constant over a wide frequency range.

System and method for hybrid geometry feed horn

Abstract: A feed horn and systems and methods of making and using the feed horn are presented. Exemplary feed horns include a first portion comprising a dual mode geometry and a second portion comprising an axial corrugation geometry. The feed horn may operate simultaneously in a plurality of separate frequency bands (e.g., from about 18.3 GHz to about 20.2 GHz and from about 29.1 GHz to about 30.0 GHz) and a plurality of separate waveguide modes (e.g., TE11, TM11 or HE11 modes); simultaneously operating over two bandwidth segments of at least 1900 MHz that are separated by at least 5000 MHz. The feed horn may have a short axial length (e.g. less than 4 wavelengths at 18.3 GHz), and it may be configured to operate in a prime fed offset reflector antenna system. In addition, the feed horn may be formed as a single piece via a single casting pull.

Look-ahead of the bit applications

Abstract: Various embodiments include apparatus and methods of operation with respect to well logging. Apparatus and methods can include a tool having an arrangement of spaced apart transmitter antennas and receiver antennas in transmitter-receiver antenna pairs to make shallow measurements and deep measurements. The signals acquired from the shallow measurements and deep measurements can be processed to provide a look-ahead signal in a drilling operation. The transmitter and receiver antennas can be oriented to cancel or substantially cancel out signals from layers between the transmitter antenna and the receiver antenna in response to the transmitter being operated downhole in a well. Additional apparatus, systems, and methods are disclosed.

Compact parabolic reflector antenna design with cosecant-squared radiation pattern

Abstract: This paper deals with the parametric analysis and proper design of parabolic reflector antennas to obtain pencil-beam, cosecant-squared and inverse cosecant-squared radiation patterns for air and coastal surveillance radars. A novel design is introduced to obtain both pencil-beam and cosecant-squared radiation patterns by using the same modified parabolic reflector antenna structure fed by an H-plane horn feeder which can be adjusted as symmetric or asymmetric feeder by changing the bottom flare angle. The analytical regularization method (ARM) is used as a fast and accurate way to solve the problem of E-polarized wave diffraction by parabolic shaped perfectly electrical conductive (PEC) cylindrical reflector with finite thickness. The numerical procedure is initially verified by the analytical and numerical methods, and the calculated radiation characteristics are presented for the proposed antenna configurations.

Antenna diversity for magnetic induction radio

Abstract: A magnetic induction system is disclosed, which has antenna diversity at the transmitter side, but which does not require a bidirectional link to pass information regarding received signal quality back to the transmitter. The system uses a time division multiplexing access (TDMA) arrangement, to transmit the same, or correlated, information with a level of redundancy, from two, or more, antenna to at least a receiver. The or each receiver is configured to determine a received signal quality from the channel received from one antenna, and, in response to inadequate signal quality, to switch to another antenna. A receiver, and a transmitter for such a magnetic induction system are also disclosed, as is an associated method. A non-limiting application of such a system is in binaural hearing aids, in which antenna diversity is preferred at the transmitter because of space limitations.

Design of Broadband Circular Polarization Truncated Horn Antenna with Single Feed

Abstract: This paper presents the design of a broadband circular polarization truncated horn antenna with single feed. It does not require any complex feeding structure and uses only a coaxial feed extended with a simple electric fleld coupling probe. The corners of the horn are truncated to generate circular polarization modes, and a broad axial ratio bandwidth which is insensitive to the probe feed dimension is achieved. Simulated and measured results of an S band truncated horn antenna are presented. The antenna has a broad 3dB axial ratio bandwidth of 26% with aperture e-ciency of 60%.

Septum Polarizer in a Circular Waveguide

Abstract: rg Abstract This article describes a circularly polarized feed horn designed to feed shallow, prime-focus or offset-fed parabolic reflectors. Both circular polarization senses are available at two individual coaxial ports. The design provides good circularity, a very clean radiation pattern with excellent side lobe suppression, outstanding isolation between ports, and needs no adjustments. An L-band example is presented, including both simulation and experimental results. The complete set of dimensions, not previously found in the literature for septum polarizers in circular waveguide, is provided for the practical engineer who desires to duplicate or scale this feed horn to other frequencies.

The 1.4-m Telescope for the Q/U Imaging Experiment

Abstract: The optical design of the 1.4-m telescope for the Q/U Imaging ExperimenT (QUIET) is described. The telescope is intended to image the polarization of the cosmic microwave background (CMB) with detectors at two frequencies (Q- and W-band) with unprecedented sensitivity. The RF optics uses a classical Dragonian side-fed geometry that employs a paraboloidal main reflector illuminated by a concave hyperboloidal subreflector. The relatively large offset distance and focal length of the main reflector, and the avoidance of caustics between the two reflectors, yield relatively flat reflectors with very low cross-polarization and a wide field of view capability. The antenna is fed by either a 91-element W-band or a 19-element Q-band corrugated platelet feed horn array. The telescope is installed on the CBI platform in Chile, and data taking is underway.

Method for measuring insertion loss of feed network

Abstract: The invention discloses a method for measuring the insertion loss of a feed network. The insertion loss of the feed network comprises feed horn heat loss and network insertion loss. In the method, the method for performing comparison by utilizing a standard gain horn is put forward, and the insertion loss of the feed network to be measured is obtained by measuring the gain of the feed network to be measured and subtracting the gain of the feed network from the gain of the feed horn. The method provided by the invention is simple and feasible, and has a popularization and application value.

Directional radio-signal-detection apparatus and methods of use

Abstract: An apparatus for direction-finding a received radio signal is disclosed. The receiving apparatus selectively receives on a predetermined frequency to match the transmitter frequency. The receiving apparatus comprises of two or three antennas, including one or two loop antennas that work in conjunction with a third reference antenna (whose phase does not vary when its orientation changes relative to the transmitter), such as a dipole, monopole or helical antenna. By comparing the phase between the antennas the direction of the incoming RF signal can be determined. In some embodiments, the windings of the two loop antennas are wound in reverse with respect to each other in order to substantially double the sensitivity of the signal-detection capabilities.

Beam forming method and multiple antenna system using the same

Abstract: Disclosed are a beam forming method and a multiple antenna system using the same. There is provided a multiple antenna system which forms optimal beam patterns through a transmission of a training sequence between a transmitter and a receiver, each including a plurality of antennas, the multiple antenna system comprising: a transmitter selecting antennas to be activated according to a level and transmitting the training sequence to a receiver through the selected antennas; a receiver selecting the antennas to be activated according to the level and transmitting to the transmitter an index of an optimal transmission weight vector significantly reducing a cost function based on the training sequence transmitted from the transmitter, wherein the transmitter selects antennas so that the beam patterns formed by the antennas selected at a q-th level (q: the index of the level) include the beam patterns formed by the antennas selected at a q+1-th level. As a result, the transmission frequency of the training sequence may be reduced.

Performance of a Quad-Ridged Feed in a Wideband Radio Telescope

Abstract: A new quad-ridged, flared horn achieving nearly constant beamwidth and excellent return loss over a 6:1 frequency bandwidth is described. The system performance in two Radio Telescopes: 1) A 12-meter symmetric dual shaped reflector system intended for geodetic very long baseline interferometry and 2) A 15-meter offset dual shaped reflector intended for the SKA is presented showing it to be excellent wideband feed choice.

Synthesis and rigorous analysis of omnidirectional dual-reflector antennas with shaped main reflector described by local conic sections

Abstract: This work presents a formulation for shaping the main reflector of an axis-symmetric dual reflector antenna designed to offer an omnidirectional coverage with an arbitrary radiation pattern in the vertical plane. The subreflector is generated by an axis-displaced confocal conic and the main reflector is shaped to achieve a prescribed far-field radiation pattern. The shaping procedure is based on geometrical optics (GO) principles. For validation of the antenna designs, the wotk employs technique by the accurate method of moments technique.

A new reflector antenna design providing two different patterns

Abstract: Antennas with cosecant squared pattern are designed for air-surveillance radar systems. These permit an adapted distribution of the radiation in the beam and causing a more ideal space scanning. In the practice a cosecant squared pattern can be achieved by a deformation of a parabolic reflector. Moreover, it can be achieved by using multiple feed antennas with normal parabolic reflector surfaces. A fan beam antenna which is a directional antenna producing a main beam having a narrow beamwidth in one dimension and a wider beamwidth in the other dimension can also be used for similar purposes. This pattern can be achieved by a truncated parabolic reflector or a circular parabolic reflector. Frequency selective surfaces (FSSs) have been used in the reflector antenna designs in recent years. A FSS is an array of periodically arranged patches or apertures, showing a particular filtering behavior. Its selectivity in frequency is obtained by the design and allows the transmission of signals in a certain frequency range only. This work is proposed to design a reflector antenna that provides both fan beam and cosecant squared pattern by using a FSS. For the simulation and optimization of the antenna, high frequency simulation software (HFSS) and SUPERNEC antenna simulation programs are used.

Quad-ridge horn antenna analysis and design for Radio Astronomy applications

Abstract: This paper presents the simulation and analysis of a 1-3GHz dual polarization Quad-ridge Horn Antenna (QRHA) to be used for Radio Astronomy applications. The coaxial to waveguide transition is a crucial design aspect of such an antenna. Using the CST Microwave Studio an air cavity coaxial connector to quad-ridge waveguide transition is designed with S11 better than -10 dB for the entire band. The QRHA is characterized for gain, co & cross polarization and edge taper.

Effects of Antenna Cross-Polarization Coupling on the Brightness Temperature Retrieval at L-Band

Abstract: Retrieval of the brightness temperature (TB) at the L-band is studied in the context of the remote sensing of ocean surface salinity. The measurement of antenna temperature and the retrieval of TB are simulated with a radiative transfer model and an observing system model of an orbiting spacecraft. Two sets of antenna gain patterns are used: 1) theoretical analysis and 2) measurements of a 1/10th-size scale model. The latter set notably shows the large cross-polarization coupling from the first Stokes transmit into the third Stokes receive. The large cross-polarization coupling causes an error of up to 4° in the estimate of the Faraday rotation angle (the size of the angle itself is mostly less than 15° in the severe ionospheric condition). By this amount of the error, an additional rotation is introduced to the retrieval of the second and third Stokes TBs in front of the feed horn before the Faraday rotation correction. The additional rotation also degrades the performance of the antenna pattern correction (APC). However, when the Faraday rotation correction is performed by the square sum of the two retrieved Stokes, the retrieved TB below the ionosphere and at the top of the atmosphere after the Faraday correction becomes insensitive to the additional rotation (i.e., being insensitive to the error in the Faraday angle estimate and the rotational error in the APC). The formal proof of the insensitivity is presented. The first and second Stokes TBs at the top of the atmosphere observed at 5.6-s intervals from space may be retrieved with an error smaller than 0.1-K rms without the accurate ancillary information of the gain pattern and the Faraday rotation angle, assuming correct calibration, 0.08 K NEΔT for the radiometer noise, and accurate correction or flagging of the solar and galaxy radiation.

SMAP antenna feed radome: Design, development, and test

Abstract: NASA's proposed Soil Moisture Active and Passive (SMAP) mission would provide global soil moisture content and freeze/thaw state measurements with a minimum repeat period of three days at the equator. To do so, the SMAP instrument would employ a conically scanning synthetic aperture radar (SAR) and a radiometer operating at L-band (1.20 GHz – 1.41 GHz) through a common feed assembly. The proposed mission profile plans to employ a near polar sun-synchronous orbit that would periodically allow for solar impingement upon the internal surfaces of the feed horn, which could result in solar entrapment. If left unaddressed, this solar entrapment would cause the instrument to exceed its tight thermal stability requirements. These thermal stability requirements result from the sensitivity of the radiometer electronics and their proximity to the feed assembly. As a result of these stability requirements, a radome was incorporated into the design to act as a thermal barrier. As such, this paper will discuss the material selection process, design rationale, analysis, and material property test campaign for the SMAP antenna feed radome.12

Multiband feed using coaxial configuration

Abstract: We present design, analysis and test results of a dual-aperture coaxial multiband feed horn that operates at S, Ku, K and Ka bands. The design objectives are to achieve aperture efficiencies of 85% for S and Ku bands and 60% for K and Ka bands and cross-polarization level of −20 dB within 30 degree off-boresight for all bands. These values are deduced primarily from the reflector geometry, −10 dB reflector edge taper and moderate cross-polarization requirements for the secondary patterns. In our design the Ku, K and Ka bands are launched through a multiflared circular horn while the S band is launched through a coaxial horn. A method of moment based software is developed to analyze the structure including mutual coupling between the apertures. It is found that the aperture impedance significantly affects the S-band performance. For the high frequency bands, the mutual coupling between the circular and coaxial apertures plays an important role. The simulated results including mutual coupling effects agree well with the measured data. The multiband feed design allows a compact, low weight, single offset reflector configuration as opposed to a Cassegrain antenna system that requires two separate feeds and a dichroic subreflector to accommodate such widely separated bands. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.

1 mm Dual-polarization science with CARMA

Abstract: We have constructed dual polarization 1 mm receivers for the CARMA array. A key science goal for these receivers is to map the linearly polarized thermal emission from dust grains in interstellar clouds, which may be used to infer the magnetic-field morphologies in these regions. Polarization fractions of a few percent are typical of this radiation. For an aperture synthesis array like CARMA it is advantageous to measure this weak linear polarization by cross-correlating the signals from circularly polarized feeds. To observe circular polarization, we install a waveguide polarizer between the feed horn and the OMT (orthomode transducer), at a temperature of 4 K, to convert incoming circularly polarized signals into linearly polarized signals. The receivers use waveguide OMTs to split the incoming radiation into orthogonal linear polarizations. The two OMT outputs are coupled to separate SIS (superconductor-insulator-superconductor) mixers and WBA-13 LNAs (low-noise amplifiers).

Design, Characterization, and Calibration of Low-Noise Terahertz Receivers

Abstract: This thesis is focused on the field of instrumentation for radio-astronomy and atmospheric science, and specifically deals with problems such as optical design and its verification, horn antennas and receiver optics’ components, different aspects of measurement systems in order to characterize low-noise THz receivers, and its calibration techniques. Ultra low-noise Terahertz receivers, used in radio-astronomy, are typically coupled to the telescope system through relay optics that provides guiding of the signal to the receiver frontend with minimal loss. Any misalignments, beam truncation, and distortion in the optical system will introduce losses and degrade the overall noise performance of the system. It is therefore critical that the optical design could be verified through measurements. In this thesis the author presents a vector beam measurement system to create possibilities to accurately characterize the optical performance of multi-band receivers over a very wide frequency range. The developed beam measurement system employs a novel circuitry allowing the use of a single reference source, different frequency harmonics of which allow to generate the required RF and LO signals yielding the desired IF, while obtaining perfect phase-coherence and initial phase-noise cancellation. An advantage of such wideband measurement system is that it could be used in different projects, nearly independent on frequency. Implementation of the measurement system, covering 163 GHz to 500 GHz, for the APEX receiver - Swedish Heterodyne Facility Instrument (SHeFI) - and the ALMA Band 5 receiver cartridge is described. Apart from optical characterization, noise-, sideband rejection, amplitude- and phase stability, and gain saturation measurements of the receivers are the measurements performed within the very same measurement setup. The measurement setup includes all necessary hardware and achieves largely automatic measurements with in-built optimization procedures. Another part of the thesis describes the author’s work on design of horn antennas. The feed horn is one of the most critical components in an optical system since it has direct impact on the total system performance. Two horn designs are presented in this thesis, one profiled corrugated feed horn, where particle swarm optimization (PSO) was successfully employed in the design procedure. The PSO drastically reduces the computational time and provides a robust optimization in terms of finding global optimum. A second horn design, implemented within PHOCUS, the Swedish sounding rocket project, is used for two water vapour radiometers, 183 GHZ and 557 GHZ. These antennas are based on the Potter horn and designed to provide FWHM of 5° without any additional focusing elements. Apart from the antenna design, two different calibration systems for both the 183 GHz and the 557 GHz radiometers on the PHOCUS sounding rocket have been suggested, designed, verified and implemented. The calibration systems shall meet challenging requirements associated with the rocket platform such as acceleration, shock, vibrations, limited space, and short flight time.