Showing papers on "Cassegrain antenna published in 2019"

Broadband Polarization-Conversion Metasurface for a Cassegrain Antenna with High Polarization Purity

Abstract: Though polarization-conversion (PC) metasurfaces have been thoroughly explored in the microwave and optical regimes, they have seldom been used in everyday applications, such as improving the overall performance of antennas for wireless communication. This study not only focuses on the strategy for designing an efficient PC metasurface, but also applies it to construct a high-performance Cassegrain antenna. This metasurface is capable of simultaneous polarization manipulation and arbitrary phase tailoring, while the antenna has the advantages of low profile, high directivity, broad bandwidth, and high polarization purity.

Dual-Band Wireless Fronthaul Using a FSS-Based Focal-Point/Cassegrain Antenna Assisted by an Optical Midhaul

Abstract: This work reports the concept and implementation of a dual-band wireless fronthaul (FH), using a frequency selective surface (FSS)-based focal-point/Cassegrain antenna, assisted by an optical midhaul (MH). Our innovative fiber-wireless architecture enables to achieve simultaneous and extended-reach transmission over two distinct bands, namely C- and Ka-bands. The dual-band wireless FH is ensured by employing a dual-band antenna, consisting of a conventional main reflector (paraboloid) and a subreflector based on a frequency selective surface, which allows integrating a focal-point and a Cassegrain system in the same structure. It presents gain from 30 to 39.4 dBi and bandwidth from 1.1 to 4.3 GHz at 7.45 and 28 GHz, respectively. The optical MH relies on applying a dual-drive Mach-Zehnder modulator for simultaneously modulating both RF signals at the same wavelength and distribute them through a 25 km fiber optical link. Finally, the RF carriers at 7.5 and 28 GHz are radiated by the FSS-based antenna over dozens of meters wireless link. Experimental results demonstrate throughput up to 18 Gbit/s with error vector magnitude in accordance to the 3GPP Release 15 requirements, giving rise to a potential technological solution for increasing the system range, as well as reducing capital expenditure costs, footprint, weight and complexity.

Structure design of a conic lens pair for improving the transmission efficiency of a Cassegrain antenna

Abstract: Central energy loss is a critical factor decreasing the transmission efficiency of a Cassegrain antenna. In this paper, a pair of conic lenses are designed and set in front of a Cassegrain antenna to improve the transmission efficiency of the antenna instead of designing a complicated antenna structure. On the basis of the analysis, the optimized conic lens pair can theoretically improve the transmission efficiency up to 100% at a wavelength of 1550 nm under ideal conditions. After several practical factors are considered, such as the dispersion of the material, the transmissivity and chamfering of the conic lens, and the reflectivity of the mirrors composing the Cassegrain antenna, the conic lens pair can still increase the transmission efficiency of the Cassegrain antenna up to 92.37% at a wavelength of 1550 nm. Compared with designing a complicated antenna, the method proposed here provides a more practical approach to improve the transmission efficiency of a Cassegrain antenna.

High System Gain E-Band Link in a Wideband Aircraft-to-Ground Data Transmission

Abstract: A wireless communication link operating in E-band at 71-76 GHz with 30 dBm of transmit power from a GaN-based solid-state power amplifier and a 3-dB noise Figure of its GaAs-based receiver is employed in a data transmission with up to 9.8 Gbit/s data rate between a plane and a ground station. Flying at a height of 1000 m above ground and at distances between 5 and 12 km from the receiver, a microlight aircraft hosts the payload mounted to its wing. The highly directional link is formed by a 39.7 dBi gain Cassegrain parabolic antenna in the plane-mounted transmitter, and a 48.7 dBi Cassegrain antenna with GPS-based antenna tracking in the ground terminal. Stable data links were established with up to 9.8 Gbit/s data rate employing QPSK, 8-PSK and 16-QAM modulation.

A Ku-Band Microwave Wireless Energy Transmission System Based on Rectifier Diode

Abstract: This paper demonstrates a Ku-band medium and long distance microwave wireless energy transmission system based on the rectifier diode. The transmitting compact Cassegrain antenna with an aperture of 1.5m forms a more centralized and uniform 2m x 2m field zone, which has more than 80% transmission efficiency. According to the distribution of receiving field, the multiple ways synthesizers connected to rectangular patch arrays are designed. And the results predict that the receiving efficiency of the antenna is directly related to the performance of the system, which reaches 50%, not including the possible insert loss. Besides, the Ku-band rectifying circuit is optimized and measured, and the comparing results show that the practical rectifier diode can obtain more than 40% conversion efficiency at the operating frequency of 12.75GHz. Finally, the microwave wireless energy transmission system is designed, and it finally obtains 4% DC-DC conversion efficiency at a distance of 60m, which is likely to be used in unmanned aerial vehicle hovering charging system, robot charging while working, isolated island wireless power supplying and wireless charging of various sensors.

On the Surface Roughness and Smoothing in the 3D Printed THz Reflectors

Abstract: This paper presents the effect of surface roughness on the performance of the 3D printed near field focused THz Cassegrain antenna configuration. It is found that the roughness affects the focal plane parameters. The nearfield directivity is reduced by ~ 3.5 dB for 60 µm rough surface, there is only a small effect on the focus spot width. A smoothing process, which reduces the conductive coating surface roughness to 4 µm, is also described. The roughness loss is less than 0.1 dB at 300GHz.

Reflector Surface Shaping Method for a Cassegrain Antenna

Abstract: Reflector surface shaping method for a dual reflector antenna has been developed to achieve an objective aperture distribution. The shaping method is composed of three differential equations. Two differential equations determine reflection laws on the main and sub reflectors. The third equation is relating to an objective aperture distribution. The third equation determines the main reflector coordinates. Other equation may be used to determine main reflector coordinates. In this paper, an equivalent parabola equation of a Cassegrain antenna is employed for the third differential equation. Through solving three differential equations by the developed MATLAB program, achievement of a dual reflector surfaces are ensured. The Obtained reflector surfaces become parabola and hyperbola at main and sub reflectors, respactively.

Ka/W dual-frequency dual-polarization high-isolation-degree high-gain Cassegrain antenna

Abstract: The utility model provides a Ka/W dual-frequency dual-polarization high-isolation high-gain Cassegrain antenna. The Ka/W dual-frequency dual-polarization high-isolation high-gain Cassegrain antenna comprises a high-isolation dual-frequency dual-polarization feed source, a feed source horn, an auxiliary reflecting surface, a main reflecting surface and a bracket structure, the feed source horn comprises a first rectangular waveguide, a rectangular circular transition structure, a second rectangular waveguide, a waveguide low-pass filter and a circular waveguide. The rectangular circular transition structure is connected with the first rectangular waveguide and the circular waveguide; an opening is formed in the side face of the first waveguide section, and the waveguide low-pass filter is arranged on the outer side of the opening and connected with the second rectangular waveguide and the first waveguide section. According to the utility model, the improved dual-frequency dual-mode conical feed source horn is adopted, and 35GHz and 94GHz radio frequency signals are radiated by using one feed source horn, so that the antenna radiation patterns of the antenna at two frequency points of 35GHz and 94GHz are ensured to point to the same direction.

A W-band Compact Dual Reflector Cassegrain antenna for Monopulse Tracking Radar

Abstract: A W-band compact Dual Reflector Cassegrain antenna with high gain, pencil beam and good sidelobe level has been designed using High Frequency Structure Simulator (HFSS) IE software. The proposed antenna consist of a Main reflector, Sub reflector and a Feed all together joined with a support structure made of Aluminum. Simulated and Experimental measured results for various antenna parameters show a very good agreement. Effect of support structure has also been studied and optimized to minimize the effect on electrical properties of the antenna.

Conversion of a Telecommunications Antenna into a Radio Telescope: Laser Scanner Measurements of Optics and Dish Surface Quality of a Cassegrain Antenna

Abstract: A number of countries have identified redundant large telecommunications antennas (TA) and indicated their intention to convert them into radio telescopes (RT). As the efficiency of a parabolic dis...

Optimal subreflector position determination of shaped dual-reflector antennas based on the parameters iteration approach

Abstract: A new method based on parameters iteration technique has been developed to determine the optimal subreflector position for shaped Cassegrain antennas to improve the electromagnetic (EM) performance distorted by gravity. Both the features of shaped surface and the relationship between optical path difference (OPD) and far field beam pattern are employed. By describing the shaped dual-reflector surface as a standard discrete parabola set, we can utilize the optical features of the standard Cassegrain system in the classical OPD relationship. Then, the actual far field beam pattern is expressed as the synthesis of ideal beam and error beam by decomposing subreflector adjustment parameters using mechanical-electromagnetic-field-coupling-model (MEFCM). Furthermore, a numerical method for determining optimal subreflector position is presented. The proposed method is based on the iteration technique of subreflector adjustment parameters, and the optimal far field pattern is used as the iteration goal. The numerical solution of optimal adjustment parameters can be obtained rapidly. Results of a 25 m Shaped Cassegrain antenna demonstrate that the adjustment of the subreflector to the optimal position determined by the proposed method can improve the EM performance effectively.

KuKa dual -frenquency cassegrain antenna and antenna system

Abstract: The utility model provides a kuKa dual -frenquency cassegrain antenna and antenna system, wherein, this cassegrain antenna includes principal reflection face, vice plane of reflection, dual -frenquency loudspeaker and feed source network, principal reflection face is used for reflecting the electromagnetic wave signal with vice plane of reflection, the electromagnetic wave signal of dual -frenquency loudspeaker radiation ku frequency channel and ka frequency channel, the electromagnetic wave signal of ku frequency channel is received to ku reception net twine among the feed source network, theelectromagnetic wave signal of ku radiating network transmission ku frequency channel, circle joint, ka polarizer, ka coupler, ka send out and hinder wave filter and ka and receive and hinder the electromagnetic wave signal that the wave filter is used for the transmit and receive ka frequency channel. The utility model provides a but the simultaneous working of kuKa dual -frenquency cassegrain antenna is received at ku, ku launches, ka receives and four frequency channels of ka transmission, need not to switch, and rational in infrastructure, compact, the performance index excellence, and antenna work efficiency is high.

3D-Printed Multi-Beam Planar Dual-reflector Antenna for 5G Millimeter-Wave Applications

Abstract: A novel planar low-profile dual-reflector antenna with multi-beam radiation is proposed in this paper. Different from traditional Cassegrain antenna, the proposed design can realize a compact configuration by employing a concave sub-reflector while maintaining the good antenna performance. An impedance bandwidth of wider than 40%, high isolation between input ports and a gain up to 23 dBi with a variation within 3 dB over the whole operating band are obtained experimentally by the three-dimensional (3-D) printed prototype. In addition, by utilizing multiple input waveguides and multiple new dual-reflector antennas, stable two-dimensional multi-beam radiation can be achieved.

2 2 Axis gimbal assembler for direct LOS stabilization of cassegrain antenna and direct LOS stabilization control apparatus

Abstract: Provided are a two-axis gimbal assembly for gaze stabilization of a Cassegrain antenna and a direct gaze stabilization control apparatus. A Cassegrain antenna in a curved-surface shape transmits a wireless signal to a target, and receives the wireless signal reflected by the target. The two-axis gimbal is provided with the Cassegrain antenna, and comprises an internal gimbal assembly rotating towards a high angle direction and an external gimbal assembly rotating towards an azimuthal angle direction. A MEMS gyroscope is mounted on the internal gimbal assembly of the two-axis gimbal, thereby measuring an angular speed of the Cassegrain antenna around sensing two axes on an inertial flat surface.

Reflector antenna and reflector antenna feed

Abstract: Embodiments of the present invention provide a reflector antenna and a reflector antenna feed. The reflector antenna feed includes a transmit antenna array and a receive antenna array, where the transmit antenna array includes at least two transmit antenna units. The receive antenna array includes at least two receive antenna units. Also, a phase center of the transmit antenna array coincides with that of the receive antenna array, where at least one coupling unit is disposed between at least one group of a transmit antenna unit and a receive antenna unit that are adjacent to each other.

Direct LOS stabilization control apparatus of cassegrain antenna

Abstract: Provided is a direct line of sight (LOS) stabilization control apparatus of a Cassegrain antenna The curved-shaped Cassegrain antenna transmits a radio signal, and receives the radio signal reflected from a target, and a two-axis Gimbal is mounted with the Cassegrain antenna, and includes an inner Gimbal assembly and an outer Gimbal assembly A MEMS gyroscope is mounted to the inner Gimbal assembly of the two-axis Gimbal to directly measure rotation of the Cassegrain antenna causing disturbance and an angular speed caused by the disturbance around two sensing axes on an inertial plane and then output an angular signal A signal processor controls drive of the two-axis Gimbal to compensate of the disturbance of the Cassegrain antenna, based on altitude information and azimuth information of a target which is tracked by the radio signal received by the Cassegrain antenna, and the angular signal directly measured by the MEMS gyroscope

A Low Profile Broadband Cassegrain Reflectarray

Abstract: In this paper, a compact Cassegrain reflectarray with low profile and broad gain bandwidth is presented. The proposed Cassegrain antenna consists of three parts, or more specifically to be a main reflectarray, a sub-reflector and a waveguide feed source. In particular, a highly-polarized microstrip grating is designed as the sub-reflector in order to substantially improve the polarization purity of the final engineered Cassegrain antenna. By employing a 90° polarization convertor, the main reflectarray is not only capable of realizing broad radiation bandwidth but also able to convert wave to its cross-polarized counterpart. By combining the main and sub-reflector, the finally assembled Cassegrain antenna is numerically simulated. The results indicate a 48% 3-dB gain bandwidth (13 – 21.2 GHz), and by introducing a sub-reflector, the F/D ratio is drastically reduced to 0.32.

Dual-band Beam Waveguide Fed Terahertz Antenna for Ground Telescope

Abstract: This paper presents the design of 3 m Cassegrain antenna fed by a dual-band beam waveguide. Antenna has been designed to achieve 60 % aperture efficiency and 90% beam efficiency at 0.225 THz and 0.338 THz bands. Gaussian beam parameters like, beam waist and radius of curvature are computed for fundamental Gaussian beam mode at input and output of mirror equivalent lenses for initial design of multireflector antenna. The simulation results of the beam waveguide antenna are presented for various electrical parameters such as beam-width, cross-polar level, side lobe level and efficiency. The realization, assembly and alignment challenges at terahertz frequencies are also discussed. This antenna has been designed for ground telescope to reveal the properties of molecular clouds in the Milky Way Galaxy for astronomical observations.

Circularly polarized single-pulse Cassegrain antenna

Abstract: The present invention discloses a circularly polarized single-pulse Cassegrain antenna. The circularly polarized single-pulse Cassegrain antenna comprises a main reflection surface and an auxiliary reflection surface which are arranged coaxially, an assembly device connecting the main reflection surface and the auxiliary reflection surface, a feed source and a feed network. The feed source is an integrally formed circularly polarized single pulse feed source, the circularly polarized single pulse feed source comprises four same-structure circularly polarized feed units arranged in 2x2, and feed ports of the four circularly polarized feed units are all connected with the feed network. According to the circularly polarized single-pulse Cassegrain antenna provided by the present invention, the feed source is an integrally formed circularly polarized single pulse feed source, so that without stratified block-by-block processing, the feed source is applicable to various frequency bands, hasa simple structure, and has the characteristics of the bandwidth and the axial ratio; and in addition, the size of the feed source can be made small, the circularly polarized feed units can be smaller than one wavelength, and compared with the prior art, the feed source has the characteristics of miniaturization, can be used for various antennas, and has strong adaptability.

Q/V Band Dual-Beam Dual-Polarization Cassegrain Antenna

Abstract: This paper presents the design and development of Symmetrical Cassegrain Unshaped reflector antenna in Q/V band for high speed communication. It is the first Q/V band antenna on-board ISRO’s Spacecraft. Highlights of the design includes arriving at a compact geometry utilizing existing moulds for realizing metallized CFRP reflectors, dual-feed system with Orthomode Transducer (OMT) that generates dual transmit-receive beams in orthogonal polarizations, high Crosspolar Isolation (XPI) and low plumbing losses. The measured Edge-of-Coverage gain of 43dBi and XPI of -27dB over the Q/V band closely matches with the predicted results.