摘要:

The paper discusses some of the particular design problems associated with a multibeam satellite-switched time-domain multiple-access (SS-TDMA) satellite payload. Contiguous beam coverage and frequency reuse between beams are shown to place some important constraints on the antenna performance. The local oscillator, switch matrix and input/output chain designs are dependent on the interbeam switching requirements. These design considerations are referenced to the Olympus Specialised Services Payload, for which a description, performance summary and link budget are presented.

DOI:10.1049/ip-f-1.1986.0055

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A pivotal development in satellite communications has been that of the spacecraft transponder, and the transmit high-power amplifier in particular. The paper examines the successful development of modular solid-state power amplifiers (SSPAs) at L-band offering significant advantages in redundancy and reliability over the travelling-wave-tube amplifier equivalent.

DOI:10.1049/ip-f-1.1986.0056

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper investigates the design of active phased arrays for communications satellites. In particular, consideration is given to the problems occurring when active arrays are required to produce multiple beams. There is a real need to keep the complexity of the array electronics to a minimum, but this conflicts with the desire to obtain the greatest possible freedom of control of the radiation pattern produced. The paper demonstrates a method of coping with the problem. Low-gain elements are used to provide design freedom and they are grouped into subarrays to limit the complexity of the rest of the system. With appropriate configurations of subarrays, greatly improved radiation pattern characteristics can be obtained and frequency reuse between multiple beams becomes feasible. A demonstration model of 108 microstrip patches grouped into 32 subarrays, operating at 12 GHz, has been constructed and verifies that the technique is effective.

DOI:10.1049/ip-f-1.1986.0057

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Bandlimited offset QPSK systems are analysed and attempts are made to find new combinations of transmit and receive filters which give improved performance trade-offs when compared with recently proposed filters such as quadrature overlapped raised-cosine (QORC) and squared raised-cosine (QOSRC), and superposed quadrature amplitude modulation (SQAM). The filters are based on finite impulse responses of up to five symbol periods (ten bit periods) duration. The results indicate that advantages can be gained over QORC, QOSRC and SQAM, if a good performance with linear channels is required as well as low degradation under hard limiting. This probably also implies good performance under soft limiting. The results are presented graphically, showing how the bit error rate performance with each filter pair degrades as the adjacent channel spacing of the system is reduced.

DOI:10.1049/ip-f-1.1986.0058

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper reviews the traffic requirements for two specific services which will benefit by the use of on-board processing: (i) business satellites for European coverage and (ii) land mobile satellites for Europe. Although the traffic requirements are very different for the two services, the proposed architectures are similar in comprising a mixture of baseband switches and transmultiplexers. The paper reviews various architectures for both components, and estimates the chip count and power requirements for the various architectures.

DOI:10.1049/ip-f-1.1986.0059

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A World Administrative Radio Conference has been convened by the International Telecommunication Union to resolve major policy issues in the international regulation of the use of the geostationary satellite orbit (GSO) for radio services. The first session, WARC-ORB(1), met in Geneva in August/September 1985. Major changes were agreed for the regulation of the fixed satellite service, the main purposes of which are to guarantee access for all ITU member nations to the GSO in certain frequency bands and to stimulate the efficiency of use of other bands. Orbit-frequency allotment plans for the bands to which access is guaranteed are to be drawn up at the second session of the conference in 1988. In addition, WARC-ORB(1) agreed a number of technical parameters for feeder links to broadcasting satellites operating under plans drawn up for Europe, Africa, Asia and Australia by the WARC in 1977. Frequency plans for these feeders are also to be drawn up at the second session. The frequency plans for satellite broadcasting for the Americas drawn up by a regional conference in 1983 were approved and incorporated into the ITU Radio Regulations. Significant progress was also made in various other long-term problems of the broadcasting satellite service.

DOI:10.1049/ip-f-1.1986.0060

出版商:IEE    

年代:1986

数据来源: IET

摘要:

In the process of synthesising a satellite communications plan, a large number of possible configurations has to be analysed in a short amount of time. An important part of the process concerns the allocation of channels and polarisations to the various systems. It is, of course, desirable to make these allocations based on the aggregate carrier/interference ratios, but this needs a considerable amount of time, and for this reason the single-entry carrier/interference criterion is usually employed. The paper presents an integer programming model based on an approximate evaluation of the aggregate carrier/interference ratios, which is fast enough to justify its application in the synthesis process. It was developed to help the elaboration of a downlink plan for the broadcasting satellite service (BSS) of North, Central and South America. The official software package of the 1983 Administrative Radio Conference (RARC 83), responsible for the planning of the BSS in region 2, contains a routine based on this model.

DOI:10.1049/ip-f-1.1986.0061

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The European Broadcasting Union (EBU) has recommended the C-MAC/packet system as a European standard for direct broadcast satellite (DBS) TV. The system is based on a time multiplex of compressed analogue vision components and digital sound and data within each line period of the broadcast signal. The paper describes the structure of the signal, outlines the service identification and conditional access systems and gives the performance in a satellite channel.

DOI:10.1049/ip-f-1.1986.0062

出版商:IEE    

年代:1986

数据来源: IET

摘要:

With the advent of high-speed digital signal processing circuits, it is now practicable to transmit television signals by satellite using a variety of digitally derived modulation techniques. By using the concept ofES/NO, the ratio of the energy needed to transmit each sample to the noise spectral density, several different signal formats are critically compared in the paper. It is shown that the wide bandwidths associated with high-definition television may be supported by relatively narrow transponder bandwidths through the use of signal formats using phase-modulated discrete symbols. Furthermore, the bandwidth efficiency is shown to be better than the classical technique of frequency modulation for satellite TV transmission. A digitally implemented system is described and results are given of successful satellite tests using the Eutelsat F1 satellite and the Westar V satellite.

DOI:10.1049/ip-f-1.1986.0063

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Direct broadcasting by satellite (DBS) of television signals to the home has received much attention recently; in contrast, less attention has been paid to sound-only (i.e. radio) broadcasting from satellites. The paper reviews the present range of terrestrial sound broadcasting and explores the possible scope and technical feasibility of using satellites. Satellite broadcasting of sound programmes to receivers of all types, including portable and mobile, situated in national or regional areas, appears technically practicable, but there are problems to be overcome. The most significant are regulatory in nature; in particular there is no appropriate frequency allocation. Various technical details also require further study to produce a system of optimum performance, flexibility and spectrum efficiency.

DOI:10.1049/ip-f-1.1986.0064

出版商:IEE    

年代:1986

数据来源: IET