Showing papers on "Cassegrain antenna published in 2020"
TL;DR: In this paper, a planar Cassegrain beam-former with a three-layered folded parallel plate waveguide geometry is investigated for millimeter-wave multiple-input multiple-output (MIMO) applications in 5G mobile communications.
Abstract: A novel wideband planar Cassegrain beam-former with a three-layered folded parallel plate waveguide geometry is investigated. By replacing the convex subreflector of the conventional design with a concave one, a 20% reduction in the size in boresight direction of the planar Cassegrain beam-former can be achieved, while its operating characteristics are not degraded. The direction of the radiation beam can be adjusted independently in the H- or E-plane by laterally offsetting the feed waveguide or bending the waveguide linking with the metallic flare that operates as a radiating structure. By this means, five Cassegrain subarrays with multiple waveguide inputs and different bending angles are stacked to build a high-gain wideband 2-D multibeam antenna array in the Ka -band, whose 3 dB beams cover angular ranges of ±60° in the E-plane and ±18° in the H-plane. A bandwidth of more than 40%, stable multibeam radiation with cross polarization of less than −25 dB, a gain of higher than 20 dBi, and a radiation efficiency of more than 90% are confirmed experimentally by a metallic 3-D printed subarray. With the compact printable geometry and the good operating performance, the presented 2-D multibeam antenna fed by the planar Cassegrain beam-formers is an attractive candidate for millimeter-wave multiple-input multiple-output (MIMO) applications in the fifth-generation (5G) mobile communications.
26 citations
TL;DR: A dual-reflector antenna with a self-supported subreflector based on a Dielectric Rectangular Waveguide along with a hyperboloid and the phase center of the DRW and the antenna optics are defined and validated through the fabrication of a Cassegrain antenna using a 3D printing technique.
Abstract: A dual-reflector antenna with a self-supported subreflector is proposed. The supporting structure is made of dielectric material and it is part of the feeding of the antenna, which is based on Cassegrain optics and works at X-band. The feeding subsystem includes the primary feed, subreflector supporting structure and subreflector surface in a single dielectric piece, resulting in a compact, light and low-cost solution. First, the subreflector and its feeding subsystem, based on a Dielectric Rectangular Waveguide (DRW) along with a hyperboloid, are described, and the phase center of the DRW and the antenna optics are defined. Then, two effective techniques to mitigate the refraction caused by the dielectric were proposed. Finally, the design was validated through the fabrication of a Cassegrain antenna using a 3D printing technique. Measurements and simulations show a very good agreement and an antenna of 26 dBi of directivity with overall very good performances is obtained, validating both the proposed subreflector and the design technique.
17 citations
TL;DR: The simulation results show that LG beam with ring-like distribution is selected to enhance the emission efficiency of Cassegrain antenna and the cross-talk among different orbital angular momentum modes can remarkably reduce through using Casse grain antenna.
Abstract: In this paper, the propagation properties of the Laguerre-Gaussian (LG) beam passing through Cassegrain antenna system in a turbulent atmosphere have been researched. The accurate analytical function for the diffraction field of LG beam passing through Cassegrain antenna, the average intensity, and the cross-talk among different orbital angular momentum (OAM) modes of LG beam passing through Cassegrain antenna in Kolmogorov turbulent have been derived. The simulation results show that LG beam with ring-like distribution is selected to enhance the emission efficiency of Cassegrain antenna. The cross-talk among different OAM modes can remarkably reduce through using Cassegrain antenna. The analysis process can also apply to accurately analyzing the propagation properties of other kinds of beams through different optical systems in turbulent atmosphere.
11 citations
TL;DR: The Bessel-Gaussian (BG) beam is used to avoid the central energy loss of a Cassegrain antenna system and the method proposed can remarkably improve the transmission efficiency of aCasse grain antenna in a practical and uncomplicated approach.
Abstract: With the improvement of the transmission efficiency, the Cassegrain antenna can be widely used in space optical communication. In this paper, the Bessel–Gaussian (BG) beam is used to avoid the central energy loss of a Cassegrain antenna system. The intensity distribution and the phase distribution of the BG beam passing through a Cassegrain antenna are theoretically derived and simulated. At a wavelength of 1550 nm, this method can theoretically improve the transmission efficiency to approach 100% under the situation in which the obscuration ratio is nonzero, and the transmission efficiency can reach more than 80% when obscuration ratio is in the range of from 0 to 0.1252 with $l=4$l=4. The effects of on-axial defocusing on the light field and the transmission efficiency are studied. The method proposed in this paper can remarkably improve the transmission efficiency of a Cassegrain antenna in a practical and uncomplicated approach.
8 citations
01 Sep 2020
TL;DR: This paper demonstrates 300 GHz terahertz wireless communication using CMOS transmitter and receiver modules targeting beyond 5G (or 6G), and successfully demonstrates real-time video transfer at a 10 m communication distance using 5G based OFDM at the 300 GHz frequency band.
Abstract: This paper demonstrates 300 GHz terahertz wireless communication using CMOS transmitter and receiver modules targeting beyond 5G (or 6G). In order to support OFDM, a self-heterodyne architecture is introduced, which effectively cancels inter-carrier-interference due to phase noise in multi-carrier modulation. Besides, to extend communication distance, the high-gain antenna of a 40 dBi Cassegrain antenna is designed. As a proof-of-concept, the paper successfully demonstrates real-time video transfer at a 10 m communication distance using 5G based OFDM at the 300 GHz frequency band.
8 citations
TL;DR: The results demonstrate an excellent radiation performance of the proposed antenna, which shows its potential application in high-performance tracking and imaging systems.
Abstract: This letter proposes a multiple-beam Cassegrain antenna with quasi-optical isolator at 200 GHz for target tracking. The proposed antenna is designed with a special topology, in which a multichannel transceiver feed integrated with a quasi-optical isolator is designed and placed in the back of the main reflector, aiming to isolate the transmitting and receiving channels, and to avoid the aperture blockage. Four receiving feeds are laterally defocused to produce offset beams and each of them is received and sampled individually without comparators, which simplifies the structure and provides flexibility for signal processing. An optimization is performed to achieve the best compromise design considering the conflicts induced by its special structure. The fabricated antenna is measured and the results demonstrate an excellent radiation performance of the proposed antenna. Four well-performed offset beams are obtained as expected and the antenna works stably within a bandwidth of 10 GHz. The measured 3 dB beamwidths vary around 0.6° and the sidelobe levels are lower than −12.5 dB for all the beams. The superiorities of the proposed antenna show its potential application in high-performance tracking and imaging systems.
5 citations
01 Sep 2020
TL;DR: In this article, a 1-meter high-speed wireless data transmission, employing a 300-GHz CMOS RF front end and Cassegrain antennas, is demonstrated, and the maximum data rate of 36 Gb/s with QPSK modulation is achieved due to high gain antennas.
Abstract: In this paper, a 1-meter high-speed-wireless data transmission, employing a 300-GHz CMOS RF front end and Cassegrain antennas, is demonstrated. To improve system SNR of the CMOS RF front end, high-gain antennas are designed for the 300-GHz frequency bands. The antenna shows the peak antenna gain of 40 dBi and the 3-dB beamwidth of 1.3 degrees, within the diameter of 6 cm. In the wireless demonstration, the maximum data rate of 36 Gb/s with QPSK modulation is achieved due to high gain antennas.
5 citations
26 Mar 2020
TL;DR: In this paper, a 6 meter in diameter cassegrain antenna is characterized and a sensitivity analysis is performed to establish relationships between design parameters, directivity, side lobe levels, and effects of strut geometry.
Abstract: This paper will characterize a 6 meter in diameter cassegrain antenna. The cassegrain antenna is a special form of a dual reflector antenna which uses a main reflector following a parabolic curve and a sub reflector which follows a hyperbolic curve. Cassegrain style antennas have multiple parameters which can be tuned to achieve specific design goals. Performing a sensitivity analysis will establish relationships between design parameters, directivity, side lobe levels, and effects of strut geometry. The initial design parameters will be assumed based on typical values. Results from the sensitivity analysis will be used to provide a performance band for the 6m Cassegrain at select frequencies.
4 citations
15 Mar 2020
TL;DR: This is the first demonstration of the designed, fabricated and tested offset Cassegrain antenna practical at 220-300 GHz, and antenna embodiment demonstrates notable size and weight.
Abstract: This paper presents a feasibility study of a classical offset dual-reflector configuration for sub-THz high gain wideband antenna demanded for radio links with multi-Gbps throughput. To the best of the authors’ knowledge, this is the first demonstration of the designed, fabricated and tested offset Cassegrain antenna practical at 220-300 GHz. Antenna embodiment demonstrates notable size and weight.
3 citations
TL;DR: In this paper, a thermal vacuum deformation measurement platform is presented to provide a space simulation chamber in where not only temperature of specimen are available from − 170 to + 140°C, but also coordinates of measurement points of component can be efficiently measured by using close-photogrammetry.
Abstract: The structure deformation of the spacecraft due to the variation of temperature in space has a significant effect on the performance and stability of the spacecraft. Therefore, a system with high accuracy to identify the deformation is proposed in this study for large components in thermal vacuum using close-range photogrammetry. A novel thermal vacuum deformation measurement platform is firstly presented to provide a space simulation chamber in where not only temperature of specimen are available from − 170 to + 140 °C, but also coordinates of measurement points of component can be efficiently measured by using close-photogrammetry. In addition, an improved deformation computation method based on coordinate optimization registration is proposed. In this method, through combining random sample consensus with singular value decomposition, partial global points whose variations are relatively small can be selected for coordinate registration. Finally, the deformation measurement for the main reflector of a Cassegrain antenna in thermal vacuum is selected as an example to validate the effectiveness of the proposed platform and method. The experimental results show that the platform and method are practical and will provide a foundation for further applications.
2 citations
13 Dec 2020
TL;DR: In this article, a wideband terahertz (THz) Cassegrain circularly polarized (CP) antenna is designed and proposed and achieves a wide impedance bandwidth of 42.8% from 0.11-0.17 THz for the reflection coefficient less than -15 dB.
Abstract: A wideband Terahertz (THz) Cassegrain circularly polarized (CP) antenna is designed and proposed in this paper. By optimizing, the proposed antenna achieves a wide impedance bandwidth of 42.8% from 0.11-0.17 THz for the reflection coefficient less than -15 dB. The axial ratio (AR) is less than or equal 3dB in this frequency band. The maximum gain of the antenna is 27.6dBi at 0.14THz.
15 Mar 2020
TL;DR: The Submillimeter Wave Instrument (SWEI) as mentioned in this paper is a passive heterodyne radiometer/spectrometer for the JUpiter Icy moons Explorer (JUICE) mission.
Abstract: The Submillimeter Wave Instrument is a passive heterodyne radiometer/spectrometer for the JUpiter Icy moons Explorer (JUICE) mission of the European Space Agency. It consists of a 29-cm off-axis Cassegrain antenna and passively cooled Schottky-mixer receivers tunable in the frequency ranges of 530-625 and 1080-1275 GHz. This paper gives an overview of the instrument optics and describes the results of Monte Carlo simulations that have been performed to determine the adverse effect of mounting tolerance of relay optics to the instrument far-field performance. Further, instrument thermal contraction based on predicted mission temperatures has been included in the optical model and its effect on the half power beam width has been evaluated. Finally, the electromagnetic reflection loss of several coating materials has been assessed. A coating protects the mirrors made of AlBeMet from corrosion and potentially reduces the reflection loss by providing a lower surface resistance than the base material.
TL;DR: In this article, computer-aided design methods are used to optimize Cassegrain antenna dimensions in the case that the feed antenna is placed exactly behind the main reflector, and a Conical corrugated hor...
Abstract: In this paper, computer-aided design methods are used to optimize Cassegrain antenna dimensions in the case that the feed antenna is placed exactly behind the main reflector. Conical corrugated hor...
15 Mar 2020
TL;DR: In this article, a novel subreflector design for dual-band Cassegrain antenna systems was proposed, reflecting frequencies in X Band and transmitting in S-Band using the Selective Laser Sintering method.
Abstract: Novel subreflector design for Dual Band Cassegrain Antenna systems was proposed in this paper. Proposed Frequency Selective subreflector, reflecting frequencies in X Band and transmitting in S-Band was designed and manufactured using the Selective Laser Sintering method. Tests were made both on the manufactured unit and on a complete antenna system using GEO satellite beacon signals. It was shown that total antenna efficiencies in both frequency bands using Frequency Selective Surface dichroic subreflector were more than 65 %.
05 Nov 2020
TL;DR: In this article, a pair of lenses is designed and set between the laser source and traditional Cassegrain antenna in order to improve the transmission efficiency of traditional CAs, and the energy distribution after the laser beam passing through the pair of lens is discussed in detail.
Abstract: Since the central part of laser beam cannot be transmitted through the traditional Cassegrain antenna, thus a large energy loss is caused. To improve the transmission efficiency of traditional Cassegrain antenna, a pair of lenses is designed and set between the laser source and traditional Cassegrain antenna in this paper. The parameters of the pair of lenses and Cassegrain antenna system is determined and the energy distribution after the laser beam passing through the pair of lenses is discussed in detail. Based on three dimensional vector refraction and reflection theory, the ray tracing of the entire communication system and the chart of the transmission efficiency are simulated with MATLAB. From the chart, it can be concluded that proper laser beam shaping can improve the transmission efficiency of the entire communication system up to 100% at the wavelength of 1550 nm under ideal condition. After taking several practical factors such as the reflectivity of the mirror composing the Cassegrain antenna, the transmissivity and chamfering of the pair of lenses and the dispersion of the material into account, the transmission efficiency of the entire system can still be increased to 95.54% at the wavelength of 1550 nm. Compared with designing complex antenna systems, the method presented in this paper is more practical and convenient for optical communication.
Patent•
10 Apr 2020
TL;DR: In this article, a rope-driven umbrella-shaped Cassegrain antenna main and auxiliary surface stable unfolding mechanism was proposed, which consisted of a central hub, radiation ribs, a feed source horn, an auxiliary surface, a spring, a main surface rope, and a winding mechanism.
Abstract: The invention relates to a rope-driven umbrella-shaped Cassegrain antenna main and auxiliary surface stable unfolding mechanism. The mechanism comprises a central hub, radiation ribs, a feed source horn, an auxiliary surface, a spring, a main surface rope, an auxiliary surface rope and a winding mechanism, and the central hub is a fixed component; one end of each radiation rib is hinged with the central hub; the feed source horn and the center hub are coaxially and fixedly connected to the upper surface of the interior of the center hub; the secondary surface is coaxially connected with the feed source horn; the spring sleeves the feed source horn, is in contact with the bottom of the auxiliary surface and pops up the auxiliary surface when the antenna is unfolded; the main surface rope penetrates through the slots of the radiation ribs and the holes in the side surface of the central hub, and two ends of the main surface rope are fixedly connected with the radiation ribs and the auxiliary surface respectively; the auxiliary face rope penetrates through the hole in the bottom face of the center hub, and the two ends of the auxiliary face rope are fixedly connected with the auxiliary face and the winding mechanism. According to the invention, the unfolding process is stable, the impact on the antenna is small, the radiation ribs are unfolded while the auxiliary surface is unfolded, the unfolding synchronism of the antenna is good, and the antenna can be folded automatically for multiple times.
01 Aug 2020
TL;DR: In this article, the near-field antenna pattern of a Cassegrain antenna at 300 GHz was measured based on non-polarimetric electrooptic (EO) frequency down conversion technique combined with a self-heterodyne system.
Abstract: Near-field antenna pattern of a Cassegrain antenna at 300 GHz was measured based on non-polarimetric electrooptic (EO) frequency down conversion technique combined with a self-heterodyne system. Measured near-field pattern of the antenna, whose diameter and designed antenna gain are 152 mm and 48 dBi, respectively, was converted to the farfield pattern to characterize the radiation pattern of the antenna. The full width at a half maximum of the antenna is obtained 0.46 deg. and 0.40 deg. for E-plane and Hplane, respectively.
Patent•
24 Nov 2020
TL;DR: In this paper, a polarization reconfigurable vortex multi-beam metasurface Cassegrain antenna, which comprises an anisotropic main reflector, an auxiliary reflector and a support structure and a feed source, is presented.
Abstract: The invention discloses a polarization reconfigurable vortex multi-beam metasurface Cassegrain antenna, which comprises an anisotropic metasurface main reflector, an active metasurface auxiliary reflector, a support structure and a feed source, and realizes the fusion design of the anisotropic metasurface main reflector and a polarization conversion active metasurface auxiliary reflecting surface.According to the polarization reconfigurable vortex multi-beam metasurface Cassegrain antenna, the capacitance value of a varactor on the active metasurface auxiliary reflector is adjusted, and electromagnetic waves in different polarization states are generated to excite the anisotropic metasurface main reflector, so that the polarization mode of each beam of the vortex multi-beam metasurface antenna is reconfigurable, multiplexing of vortex beams in different polarization modes in a single channel is realized, and the communication capacity of the existing vortex multi-beam metasurface antenna is increased.