摘要:

AbstractThe carrier‐phased array—in which array phasing is derived from the incident modulated signal—is conceptually a very simple means of achieving automatic beam pointing in communications systems. The technique is particularly suitable for satellite reception applications, although careful consideration must be given in a practical design due to problems associated with the low signal levels derived from satellite broadcasts. In this paper, the basic principles of operation of such an array are described and the requirements of a practical system are addressed, resulting in the design and evaluation of an array system suitable for use with BPSK modulated signals from a communications sate

ISSN:0737-2884    

DOI:10.1002/sat.4600080102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe simultaneous demand for increased capacity of communication satellite channels and the demand for such systems to be designed and operate within increasingly stringent economic constraints places severe requirements on the ability to predict, achieve and maintain the reliable operation of these satellite links throughout the United States. The operating frequencies of satellite links are such that the occurrence of rain anywhere along the link will induce attenuation of the signal and is the major source of link reliability degradation. A unified model is presented that describes the relevant static and dynamic statistics of attenuation on an arbitrarily specified satellite link for any location for which there is a long‐term data record of rainfall statistics. In addition to providing accurate, location‐dependent statistical predictions of the reliability of satellite links, the generality of the model also establishes a basis for the design of optimal stochastic control algorithms used to mitigate the deleterious effects of attenuation and thus maintain link reliability. The rain statistics that are required to characterize the location of interest are derived from extreme value statistics theory. A rain‐statistics database has been compiled that allows one to apply the model anywhere in the continental United States with the resolution of 0.5° in latitude and longitude. Comparison of the model predictions is made with available experimental observations and agreement is found to be quit

ISSN:0737-2884    

DOI:10.1002/sat.4600080103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractWith the launch of the European Space Agency's Olympus‐1 satellite, a whole new era of communication experiments in the 20/30 GHz bands will start. Of particular interest will be those experiments concerned with fade countermeasures for the very small aperture terminals (VSATs). Portsmouth Polytechnic's experiment will focus on adaptive modulation as a type of fade countermeasure, and this paper introduces and describes the whole concept. Based on the assumption that the performance of a VSAT operating at 20/30 GHz band will be affected to a major extent by amplitude scintillations and rain fading, the performance of a range of combinations of earth‐station power amplifier and antenna characteristics is presented. An adaptive multi‐phase shift keying technique is then compared with conventional systems in terms of availability and data throughput. It is shown that such a fade countermeasure contributes to increasing both the overall system availability and the total data throughput of a digital communication system, while the inevitable reductions in data rate occur smo

ISSN:0737-2884    

DOI:10.1002/sat.4600080104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper presents and discusses the results of technical tests on land mobile communications conducted in June and July 1989 in Europe using a EUTELSAT satellite. The land mobile communication system under test was that already operated by QUALCOMM in the U.S.A. under the registered name OmniTRACS.The field trial was organized in conjunction with the Signatories who expressed to EUTELSAT an interest in a full‐scale technical investigation of the system. The aim of the field trial was to evaluate the technical characteristics of the system and test its performance in different operating conditions.The results establish the relationship between transmission performance (i.e. essentially the required number of transmission attempts in order to get a message through the communication channel), and the environment of the land mobile, the satellite transponder's mode of operations and the interference condition

ISSN:0737-2884    

DOI:10.1002/sat.4600080105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600080101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY