Space communication antenna

Figure 1-7. Examples of plastics in the electrical and electronics field a) snap-in cable set of plugs and adapters, using Amoco s Ardel D-lOO polyarylate b) plastic parts in a sixty-ft.-diameter high-precision, high-frequency antenna c) schematic of a reinforced plastics/ composite radome that protects a 150-ft.-diameter radar antenna from its Maine environment view of reinforced plastics sandwich geodesic radome being assembled the completely assembled radome d) space-communication antenna. The horn of plenty uses an RP sandwich in its reflective panels (glass-fiber-TS polyester skins with a kraft paper-phenolic honeycomb core). It has a two-ply air-inflated Du Pont Hypalon/Dacron fabric elastomeric radome that will protect the antenna from the outside environment for many decades and uses other plastics. This site in Maine was the world s first ground-to-ground conununication satellite.

Deep space network—A system of large communications antennas around the world that provides continuous communications with spacecraft as the earth rotates. When one antenna turns out of range, the next takes over the task of staying in contact with the spacecraft. 

The second proposed antenna for on-body communication is a planar Yagi-Uda, providing end-fire radiation for on-body propagation. In free space, the antenna is matched over the complete 60 GHz band and exhibits a maximum gain of 11.8 dBi at 60 GHz. Human body proximity affects performance depending on the antenna-body separation distance. However, the antenna also performs in a satisfactory way when deployed on a human subject, as well as under bending conditions. 

A large microwave antenna transmits communications for the Kennedy Space Center in Rorida. Corbis-Bettmann)... 

Plastics will continue to be required in space applications from rockets to vehicles for landing on other planets. The space structures, reentry vehicles, and equipment such as antennas, sensors, and an astronaut s personal communication equipment that must operate outside the confines of a spaceship will encounter bizarre environments. Temperature extremes, thermal stresses, micrometeorites, and solar radiation are sample conditions that are being encountered successfully that include the use of plastics. 

The Deep Space Network is an international network of large antennas and communication facilities that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports some Earth-orbiting... 

These studies are often spurred by the government s need to transmit growing amounts of voice, data, and video information through space systems, or to assess whether new technologies have made it possible to do so. To begin such a communications system study, analytical models in the CDC are updated to account for technical advances such as phased array antennas, lightweight centralized... 

The first one is a four-element patch antenna array for off-body communication in the 60 GHz band. The antenna radiating elements were fabricated by laser cutting a 0.07-mm-thick flexible copper foil, deployed on a cotton substrate with a Shieldlt ground plane. Antenna performance was experimentally tested in free space and in... 

Radio astronomy uses techniques for detection of radio signals from space similar to those used by radio communication systems. The radio telescope is basically the antenna that focuses the radio flux onto a detector. Electronic circuitry amplifies the detected signal. As with radio communication, the signal from multiple antennas, or multiple radio telescopes, can he combined electronically to yield more information than that which could be detected by one radio telescope alone. The similarity between the two technologies has permitted many advances in radio astronomy to be used in the field of commercial communication and vice versa. 

A typical problem in the design of a radio frequency communications system requires the calculation of the power available at the output terminals of the receive antenna. Although the gain or loss characteristics of the equipment at the receiver and transmitter sites can be ascertained from manufacturer s data, the effective loss between the two antennas must be stated in a way that allows for the characterization of the transmission path between the antennas. The ratio of the power radiated by the transmit antenna to the power available at the receive antenna is known as the path loss and is usually expressed in decibels. The minimum loss on any given path occurs between two antennas when there are no intervening obstructions and no ground losses. In such a case when the receive and transmit antennas are isotropic, the path loss is known as free space path loss. 

In wireless radio communication, electromagnetic waves are radiated into the atmosphere or free space via a transmitting antenna. For efficient radiation, the antenna length should exceed one-tenth of the wavelength of the electromagnetic wave. The wavelength X is given by... 

Shape control and active flow, the mainly static deformation of space and aerodynamic structures to either improve communication performance of antennas or adapt structures to optimum aerodynamic fluid flow, both achieved by integrated actuation mechanisms. 

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