Engineering topics
Publications and source records attributed to Chakraborty, Dayamoy.
Proposed control subsystem adjusts power radiated by uplink transmitter in Earth station/satellite relay station/ Earth station communication system. Adjustments made to compensate for anticipated changes in attenuation by rain. Raw input is a received downlink beacon singal, amplitude of which affected not only by rain fade but also by scintillation, attenuation in atmospheric gases, and diurnal effects.
The Jet Propulsion Laboratory under the auspices of NASA carries out radiowave propagation studies for satellite communications. As a prelude to the ACTS experiments, it was considered prudent to gather experience in 20/30 GHz propagation using the Olympus satellite beacons at 12, 20, and 30 GHz. Therefore, NASA funded an experiment program with Virginia Tech under JPL management to develop hardware and to collect data for the Olympus campaign. The paper reviews the results of the Olympus campaign. The experience gathered from this campaign is beneficial to the forthcoming ACTS propagation program which is also discussed in this paper.
The purpose of the Advanced Communications Technology Satellite (ACTS) is to demonstrate the feasibility of the Ka-band (20 and 30 GHz) spectrum for satellite communications, as well as to help maintain U.S. leadership in satellite communications. ACTS incorporates such innovative schemes as time division multiple access (TDMA), microwave and baseband switching, onboard regeneration, and adaptive application of coding during rain-fade conditions. The success or failure of the ACTS experiment will depend on how accurately the rain-fade statistics and fade dynamics can be predicted in order to derive an appropriate algorithm that will combat weather vagaries, specifically for links with small terminals, such as very small aperture terminals (VSAT's) where the power margin is a premium. This article describes the planning process and hardware development program that will comply with the recommendations of the ACTS propagation study groups.