Showing papers on "Cassegrain antenna published in 2021"

Cassegrain antenna for a laser diode source using an E-A system to improve the transmission efficiency.

Abstract: To solve the serious loss problem for central energy of the Cassegrain antenna, this paper designs a beam-shaping system, named E-A system, to convert the elliptical divergent beam with astigmatism from a laser diode into an annular collimation beam. This E-A system, comprised only of lenses with quadratic surfaces, can simultaneously realize four functions, i.e., aberration correction, beam circularization, beam collimation, and dark hollow beam generation. By adjusting the parameters, the E-A system can be used to shape elliptical astigmatic beams with different parameters. Further, the E-A system can maintain good performance at wavelengths from 500 to 1647 nm. After considering various practical factors, the transmission efficiency of the entire transmitting system can be increased to 93.91% at a wavelength of 1550 nm.

Towards the Exploratory In-Orbit Verification of an E/W-Band Satellite Communication Link

Abstract: This contribution details the motivation and the status of a new satellite mission, which targets the in-orbit verification of a wideband satellite communication link operating in the high millimeter-wave regime at 71–76 GHz. The paper reviews the dynamic link budgets for data links between satellites in low-earth orbits and ground stations on close to sea level, taking into account the expected atmospheric attenuation according to lTU models and supported by successful terrestrial transmission experiments, which confirm the feasibility and attractiveness of exploiting allocated spectrum in E-band for Gigabit satellite feeder links of globe-spanning satellite constellations and high capacity data downlinks in earth observation, even under adverse weather conditions. The scientific payload, hosted by a 6V-Cubsat platform, comprises a high-performance E-band transmitter with GaN-based solid state power amplifiers, an InGaAs-based low-noise receiver and a modern FPGA-based digital processing unit realizing AWG functionality and 4k image/video storage. The ground terminal employs a highly directive Cassegrain antenna with coarse GPS and fine RF tracking and a low-noise receiver.

Focusing characteristics of Bessel-Gaussian beam passing through Cassegrain antenna system in weak turbulence

Abstract: The transmission characteristics of the Bessel-Gaussian (BG) beam propagation in free space and turbulence atmosphere after passing through the Cassegrain antenna system are researched in this paper. The research results show that the half-cone angles of the beam and parameters of the optical system can be used to control the propagation trajectory and the cross-talk among different orbital angular momentum (OAM) modes of the BG beam. The BG beam has a focusing property when propagating in free space after passing through the collimating optical system. The trend of cross-talk among different OAM modes is different for focused BG beam and non-focused beam, and the focusing beam can potentially reduce cross-talk among different OAM modes at the receiver plane.

Optimal Design of Elliptical Beam Cassegrain Antenna

Abstract: An optimal design method of elliptical beam Cassegrain antenna based on differential evolution with global and local neighborhoods algorithm is proposed to achieve high efficiency, low sidelobe, and low profile at Ku/Ka dual band. A rapid shaping method of elliptical beam antenna is given by applying the algorithm of steepest descent. Constraining of the first sidelobe level, antenna efficiency is optimized with only 17 variables, where aperture field distribution functions in the major and minor axis planes are parameterized by Non-uniform rational B-spline curves, and the transition function is expressed with a sinusoidal function. A prototype of optimized antenna with an aperture of 630mm $\times1150$ mm is fabricated and measured. The measured results show that the total efficiency is greater than 54.5%, and the first sidelobe levels are lower than −14.2dB across the Ku/Ka dual-band, which agree well with simulated ones. It is verified that the optimal design method is very effective.

Dual-polarization transmission surface with terminating filter circuit to control electrical characteristics and design method thereof

Abstract: The invention discloses a dual-polarization transmission surface with terminating a filter circuit to control electrical characteristics and a design method of the dual-polarization transmission surface. The transmission surface comprises a dual-polarization receiving antenna array, the filter circuit and a transmitting antenna array, wherein the receiving antenna array is used for transmitting received electromagnetic wave signals to the filter circuit, the filter circuit is used for realizing regulation and control of amplitude, phase and frequency characteristics of a transmission surface,and the transmitting antenna array is connected with a filter circuit terminal. The invention provides a new concept of controlling the electrical characteristics of incident electromagnetic waves byusing a circuit, a single-band or multi-band transmission surface with filtering characteristics can be realized by reasonably designing the circuit, and a frequency selection surface with a reflection band and a transmission band can be obtained; the dichroic mirror can be used as a secondary reflector of the Cassegrain antenna.

Theoretical Design of a Holography Horn for the Surface Accuracy Testing of a Large Cassegrain Antenna at Ku-Band

Abstract: The theoretical design of two optimized horn-options to test the surface accuracy of a large Cassegrain reflector antenna through the use of the holography technique is presented. Two different horn concepts are actually considered: a smooth-walled spline-profile horn and a spline-profile corrugated horn.

A Cassegrain antenna design for terahertz focal plane imaging system

Abstract: A Cassegrain antenna for terahertz focal plane imaging system is proposed in the article. The antenna is designed according to the actual requirements of the THz detector feeds. The antenna is simulated by using CST. The simulation results show good performance with the gain of 56 dBi and the 3 dB bandwidth of 0.26° at 340 GHz. When the feed offset reached maximum at $\delta=15\text{mm}$ , the antenna gain is 54.3dBi. And when the feed is defocused by 1mm laterally, the beam pointing deflection is about 0.12°.

Electrooptic sensing for antenna characterization and propagation investigation at THz band

Abstract: We show the two applications of an electrooptic sensing which is based on a nonpolarimetric frequency down conversion technique at terahertz frequency band. We demonstrate the near-field measurement and far-field characterization of a Cassegrain antenna at 300 GHz. We also demonstrate the visualization of a wave packet propagation in a free space at 120 GHz.

Design of a Transceiver Integrated Multiple-Beam Cassegrain Antenna at 340GHz for Situational Awareness

Abstract: This letter proposes a transceiver integrated multiple-Beam Cassegrain Antenna at 340GHz. The proposed receiving antenna uses a sixteen-channel receiving feed array. Sixteen receiving feeds are misaligned to produce offset beams, and each of them is received individually, which simplifies the structure and provides flexibility for signal processing. The proposed transmitting antenna and receiving antenna are coaxial. The main reflector of the parabolic transmitting antenna is connected with the receiving antenna’s sub reflector, thereby improving the space utilization and the robustness. Sixteen-beam Antenna ensures a large-angle scanning, and works stably within a bandwidth of 25GHz. The main lobe gain is greater than 55dB, 3dB beam-width varies around 0.16° and the sidelobe levels are lower than -24dB for all the beams. The proposed antenna shows an excellent radiation performance which can meet the needs of RF front-end of the situational awareness system.