Narrow multibeam satellite ground station antenna employing a linear array with a geosynchronous arc coverage of 60°, part II: Antenna design

A dually polarized narrow (< 0.5deg) beam antenna which provides a geosynchronous arc coverage of60degis proposed and analyzed. To track the geosynchronous arc accurately, the properly oriented antenna produces a conically scanned beam by means of a linear array of feed horns with bias cut apertures illuminating a pair of parabolic cylinder reflectors in an imaging arrangement. This design, with reduced size array and singly carved reflectors, is relatively simple to construct. Calculations for a0.35degbeamwidthKuband earth station antenna show a0.05degpointing accuracy with scan loss due to aberrations less than 1 dB and little pattern degradation throughout the scan region. For multiple beam capability, a Rotman lens is proposed and analyzed as a means of exciting the feed array. It allows communication with multiple satellites spaced as close as1deg.     

星载自适应调零天线在LEO卫星中的应用研究

分析了LEO卫星系统对自适应调零天线的需求,针对地基干扰站对LEO卫星实施大功率阻塞式干扰的可行性进行了量化分析。在星载多波束天线的应用背景下,提出了适合LEO卫星的自适应调零天线的构架,给出了系统框图,并对相关问题进行了分析讨论。在此基础上,提出了凝视干扰波束的概念,极大地简化了LEO卫星调零天线在干扰调零后的波束重组的过程,并给出了波束重组过程的示意图。     

Performance of a modified feedback loop adaptive array with TVROsatellite signals

Performance of an experimental adaptive antenna array system is evaluated using television receive-only (TVRO) satellite signals. The experimental system is a sidelobe canceller with two auxiliary channels. Modified feedback loops are used to enhance the suppression of weak interfering signals. The modified feedback loops used two spatially separated antennas, each with an individual amplifier for each auxiliary channel. Thus, the experimental system uses five antenna elements. Instead of using five separate antennas, a reflector antenna with multiple feeds is used to receive signals from various TVRO satellites. The details of the earth station are given. It is shown that the experimental system can null up to two signals originating from interfering TVRO satellites while receiving the signals from a desired TVRO satellite     

基于卫星平面阵列多波束天线波束空间的 自适应调零和干扰源定位技术

 本文建立了卫星平面阵列多波束天线的基本模型,并给出了平面阵列多波束天线的阵元空间和波束空间的基本概念.研究了基于卫星平面阵列多波束天线波束空间的自适应调零和干扰源定位技术并给出了仿真结果.理论分析和仿真结果表明:基于平面阵列多波束天线波束空间的自适应调零和干扰源定位技术可以在卫星通信系统中得以应用,可以极大的提高卫星通信系统的抗干扰能力.     

Protection of FS receivers from the interference produced by HEO FSS satellites in the 18 GHz band: Effect of the roll‐off characteristics of the HEO system satellite antenna beams

This paper focuses on the protection of fixed service (FS) receivers from the aggregate interference produced by the satellites of multiple highly elliptical orbit satellite systems (HEOs). It analyzes the protection given to FS receivers operating in the 18 GHz frequency band by the power flux‐density (pfd) mask contained in Article 21 of the 2003 edition of the Radio Regulations [International Telecommunication Union, 2003.]. This mask establishes the maximum allowable value for the pfd produced by any of the satellites of a non‐geostationary system at the Earth's surface. The protection offered to FS receivers by this mask is analyzed in four interfering environments, each containing three identical HEO systems. Four types of HEO systems, with different orbital characteristics, are considered: three having satellites that operate only in the northern hemisphere and one having satellites that operate in both hemispheres. All satellite antennas are assumed to radiate 0.3° spot beams. Each HEO satellite is modelled so that the maximum pfd it produces at the Earth's surface just meets the RR Article 21 mask and the analysis takes into account the roll‐off characteristics of the satellite antenna beams. To reflect the multiplicity of possibilities concerning the geographical location and technical characteristics of the victim FS receiver (e.g. latitude, longitude, azimuth and elevation of its receiving antenna, antenna gain, receiver noise temperature, etc.) a number of cases were evaluated. The concept of interference in excess [Int. J. Satellite Commun. Networking 2006; 24 : 73–95] was used to combine the results corresponding to FS receivers located at the same latitude and having the same receiving antenna elevation angle but for which the location longitude and the azimuth of the pointing direction of its receiving antenna are randomly chosen. Results are expressed in terms of the cumulative distribution function of the interference in excess. Copyright © 2008 John Wiley & Sons, Ltd.     

Interference from mobile satellite systems through terrain scattering

The emerging generation of personal communications satellites, built to communicate with handheld telephone units, will generate power flux on earth that is orders of magnitude higher than that of the present satellite service, and its potential interference with terrestrial-based systems is of concern. It is proposed here that the flux scattered from the ground surface into the antenna main beam and near sidelobes may cause higher interference than direct coupling into the antenna. This mechanism, previously observed in terrestrial systems, may not be mitigated by adaptive nulling techniques, and is less angle-dependent. A simple model is developed, to be used as a computational tool for assessing the interference and its functional dependence on governing parameters. In the absence of proper terrain scattering models, examples are evaluated by borrowing results from interference observed in terrestrial microwave links, which indicate the possible severity of the effect.     

Communication satellite processing repeaters

Two kinds of processing repeaters which may find application on communication satellites in the near future are described. The type I repeater allows access only if the transmitted signal contains a predetermined code structure. This serves three purposes: first, unauthorized users are excluded, second, co-channel interfering signals are not retransmitted on the downlink, so as not to waste a portion of the satellite transmitter power, and, third, removal of the interference signal at the satellite avoids having to do this at the ground receiving terminal. Thus such a repeater would find particular application where there are a large number of ground receiving stations. The type 2 repeater routes signals received at its N input terminals to be transmitted at N output terminals, thus acting as a "switchboard in the sky." Two purposes are served: first, the satellite capacity is more fully utilized in the presence of fluctuating traffic demands, and, second, single-frequency transmission and reception are possible for user ground stations, thus simplifying these stations and still allowing communication to any station in the network. It is established when the type 1 repeater is able to increase the satellite communication capability beyond that of a simple repeater and further that fairly simple filtering is sufficient on the satellite. For the type 2 repeater, a proposed frequency control plan minimizes the filtering required on the satellite where frequency division multiplex is used and reduces the amount of switching required on the satellite to N single-pole N-throw switches where time division multiplex is used without the requirement of any memory on the satellite. A summary of present-day translating repeaters, as used in the Intelsats III and IV and DSCS II satellites, is included.     

应用于卫星多波束天线的自适应波束形成算法比较

射频干扰会严重影响卫星通信链路性能,而自适应调零天线是一种有效的卫星抗干扰措施.本文对应用于多波束天线的各种自适应波束形成算法进行对比分析,理论分析与仿真结果皆表明,DMI和RLS算法相对经典的LMS算法而言,在收敛速率和输出信噪干扰比上皆有相当的优越性.这些快速算法适合卫星通信的干扰抑制应用.     

On the power flux‐density limits to protect the fixed service from HEO FSS satellites emissions in the 18 GHz band

This paper focuses on the protection of Fixed Service (FS) receivers from the aggregate interference produced by the satellites of multiple highly elliptical orbit satellite systems (HEOs). It analyzes the protection given to FS receivers operating in the 18 GHz frequency band by different power flux‐density (pfd) masks. These masks establish the maximum allowable pfd produced by each HEO satellite at the Earth's surface. The protections offered by four different pfd masks are analysed in two interfering environments, each containing three HEO systems. Two types of HEO system, with different orbital characteristics, are considered: one having satellites that operate only in the northern hemisphere and another having satellites that operate in both hemispheres. To reflect the multiplicity of possibilities concerning the geographical location and technical characteristics of the victim FS receiver (e.g. latitude, longitude, azimuth and elevation of its receiving antenna, antenna gain, receiver noise temperature, etc.) a large amount of results and curves is usually generated by the studies, making it difficult to draw general conclusions on the protection offered by the pfd masks under analysis. In looking for alternative ways of presenting the obtained results, a new variable was defined: the interference in excess. This new variable was defined in a way so that its probability distribution function reflects the protection given to an FS receiver located at a given latitude with a given receiving antenna elevation angle. It indicates the protection of an FS receiver for which the location longitude and the azimuth of the pointing direction of its receiving antenna are randomly chosen. This allows the large amount of results to be compacted into a small number of more representative curves from which general conclusions on the protection offered by the different pfd masks are easily drawn. Copyright © 2006 John Wiley & Sons, Ltd.     

Sidelobe level reduction by improvement of strut shape

From the viewpoint of effective utilization of both the geostationary orbit and the frequency spectrum in the satellite communication system, it is strongly required of an earth station antenna to have low sidelobe characteristics in order to minimize the interference from/to the adjacent satellite and the terrestrial microwave links. The reference diagram of the sidelobe gain for a large antenna recommnended by International Radio Consultative Committee (CCIR) is drawn as follows:G = 32-25 log thetadBi (1 deg leq theta leq 48deg);G = -10dBi (theta > 48deg), whereGis the sidelobe gain relative to an isotropic antenna andthetais an offset angle from the main lobe axis in degrees. In the case of an axisymmetrical Cassegrain antenna operating with circular polarization, the level of the cross-polar sidelobe due to diffraction by the subreflector support struts exceeds that shown in the above reference diagram. By introduction of a new type of strut, the sidelobe gain can be suppressed below that shown in the CCIR reference diagram. In this article, a design method based on geometrical theory of diffraction (GTD) for improving the strut shape is presented. The wide-angle sidelobe gain of the standard "A" earth station antenna, installed in Yamaguchi, Japan, being equipped with the improved strut, can meet that shown in the CCIR reference diagram in all directions for both co- and cross-polar polarizations in the 6 GHz band.     

Stepped-reflector antenna for dual-band multiple beam Satellite communications payloads

A novel stepped-reflector antenna (SRA) suitable for dual-band multiple beam satellite payloads is introduced in this paper. The SRA system produces "flat-top" radiation patterns for receive beams and highly efficient Gaussian patterns for transmit beams over a geographic coverage region as seen by the geo-synchronous satellite. It combines the reflector improvements through the use of SRA with the feed horn advancements through the use of dual-band "high-efficiency horns" in order to realize an efficient multiple beam antenna (MBA) system supporting both downlink transmit and uplink receive signals of communication satellites. It is shown that the SRA provides a congruent set of spot beams on ground for both transmit and receive frequencies with the benefits of significantly improved edge-of-coverage gain, improved co-polar isolation among beams that re-use the same frequency channels, receive beam patterns that are less sensitive to satellite pointing error, and reduced number of reflector antennas when compared to conventional MBAs.     

智能天线应用于卫星移动通信终端抗干扰

智能天线技术可以极大地增强卫星通信系统的抗干扰性能。讨论应用于卫星移动通信终端的智能天线技术,提出了利用智能天线技术的卫星移动通信终端的两种可能的系统实现方案。从计算成本及干扰抑制性能的角度对它们做了初步的比较,仿真结果表明采用这两种实现方案的卫星移动通信终端可以有效抑制下行链路存在的干扰,提高输出信干噪比,取得较为满意的干扰抑制效果。     

VLSI systolic arrays for adaptive nulling [radar]

Presents a case study of the design of a computationally intensive system to do adaptive nulling of interfering signals for a phased-array radar with many antenna elements. The goal of the design was to increase the computational horsepower available for this problem by about three orders of magnitude under the tight constraints of size, weight and power which are typical of an orbiting satellite. By combining the CORDIC rotation algorithm, systolic array concepts, Givens transformations, and restructurable VLSI, we built a system as small as a package of cigarettes, but capable of the equivalent of almost three billion operations per second. Our work was motivated by the severe limitations of size, weight and power which apply to computation aboard a spacecraft, although the same factors impose costs which are worth reducing in other circumstances. For an array of N antennas, the cost of the adaptive nulling computation grows as N³, so simply using more resources when N is large is not practical. The architecture developed, called MUSE (matrix update systolic experiment) determines the nulling weights for N=64 antenna elements in a sidelobe cancelling configuration. After explaining the antenna nulling system, we discuss another DSP computation that might benefit from similar architecture, technology, or algorithms: the solution of Toeplitz linear equations     

A satellite system for CATV

The increasing capacity of CATV systems has generated a demand for more program material than can be economically generated with local facilities. A possible solution is a nationwide satellite distribution system dedicated to CATV which would provide the additional material directly to the CATV head-end. This paper presents a satellite system design that would distribute six TV channels to 10 ft antenna terminals located at the head-end. Since such a system requires thousands of receiving terminals, their cost must be minimized to produce an economically viable system. The system addressed in this paper requires a ground terminal that is comparable to a standard microwave relay terminal in both cost and complexity. The system consists of three satellites, covering the Eastern, Central, and Western portions of the United States. Based on tradeoffs of spectrum availability and low-noise amplifiers, the 12 GHz frequency band has been selected for the satellite to terminal link. The proposed terminal uses a fixed high-efficiency 10 ft antenna with extremely simple but rigid construction. A low-cost tunnel diode amplifier is used for the receiver front end. After the necessary down-conversion, detection of each channel is performed at the standard 70 MHz IF frequency. The required satellites could be launched on an Atlas Centaur launch vehicle using present technology. The satellites would weigh an approximate 1500 Ib and generate 5 kW of dc power.     

Optimum Allocation of Multibeam Communications Satellite Resources

Future communications satellites can be expected to employ multibeam antennas for both receiving (uplink) and transmitting (downlink). The use of multibeam satellite transmitting antennas raises the question of how to assign the transmitted power and antenna gain to each of theNbeams such that optimum use is made of satellite resources. We refer to this problem as the downlink allocation problem; it is part of the larger problem of allocating all satellite network variables. This concise paper deals with both problems. Specifically, we rigorously formulate and solve the downlink problem for an arbitrary number of beams using the Lagrange multiplier technique for constrained extremal problems. We then discuss procedures for incorporating the optimum downlink allocation results into a complete system allocation.     

降雨对于CAPS微小卫星终端通信的影响

中国区域卫星定位系统（CAPS）是卫星导航通信一体化的系统。当利用CAPS微小卫星终端系统进行卫星通信时,所用的天线口径极小,增益低,终端的有效全向辐射功率EIRP。较小,整个通信链路的余量较小。虽然C波段的降雨衰减远没有Ku波段大,但是相对于微小卫星终端的整个卫星通信链路来说,降雨带来的信号衰减、地球站接收天线G／T值的变化以及对卫星通信上、下行链路载噪比的影响也是不可忽视的。文章对这些影响进行了分析,并利用ITU—R给出的降雨衰减预报模式,给出了C波段的降雨衰减的计算方法及结果,并且分析了降雨对CAPS微小卫星通信系统的整个链路余量的影响。     

Optimum Satellite Home Receiving Antenna Size at C Band

The crowding of the orbital arc with the attendant imposition by the FCC of the 20 orbital spacing requirements between satellites will end the trend toward smaller satellite home receiving antennas. Smaller antennas (less than 10 feet in diameter), which are subject to interference from adjacent satellites, will be replaced by larger antennas. In this paper the expected interference is calculated, and the resulting received signal-to-noise ratio is estimated. To ensure interference-free C band' reception under the present 20°, spacing requirement, the results indicate that the receiving antenna diameter should not be smaller than about 11 feet. In high satellite EIRP cases, only by increasing the antenna size to 16 feet or larger is it possible to achieve improvement over an 11 foot antenna. For sizes between 11 and 16 feet, performance degrades in comparison with an 11 foot antenna because the interference falls onto the antenna's side lobes and is not sufficiently attenuated.     

Radio System Interference from Geostationary Satellites

Geostationary communications satellites have a potential for causing interference into terrestrial radio relay systems since present INTELSAT satellites as well as a number of U.S. domestic satellites transmit a downlink frequency in the 4 GHz common carrier band. Use has been made of recently measured spatial antenna radiation patterns of the AT&T KS15676 pyramidal horn-reflector antenna to calculate the interference noise into typical U.S. high density 4 GHz radio relay systems. The model employed uses the maximum allowed CCIR flux from the satellites so that the results are conservative since the flux from deployed satellite repeaters is normally below that level. Although certain cases such as east-west oriented existing systems with one or more direct exposures may experience noticeable interference, no significant noise problem is foreseen from this source even when the geostationary orbit is populated as heavily as one communications satellite every 3°.     

卫星通信抗干扰设计考虑及性能分析

提出了直接序列扩频和自适应调零天线相结合的卫星通信抗干扰设计思路,针对不同干扰条 件和不同卫星转发方式,进行了系统抗干扰性能的理论分析,结果表明,直接序列扩频和自 适应调零天线相结合,经星上再生处理转发可有效提高系统抗干扰能力。相关分析与结论对 工程应用具有一定的参考意义。     

20, 30 GHz Band Cassegrain Earth Station Antenna for the Japanese Domestic Satellite Communication System

An 11.5 m 30/20 GHz band Cassegrain antenna has been developed for a Japanese domestic satellite communication system earth station. In order to form an economical satellite communication network, the earth station antenna is required to be installed on the top of a telephone office building in a large city. Therefore, interference with terrestrial radio relay systems and antenna load on a building become the most important problems to be investigated. Considering the satellite position in geostationary orbit, a limited steerable system combined with a two-jackscrew drive mechanism is employed to lighten and simplify the antenna structure. Measured antenna aperture efficiencies are 72% in 20 GHz band and 68% in 30 GHz band. Measured wide angle radiation patterns satisfy the CCIR recommendation level. TheG/Tof the antenna at the feed horn port is measured to be 53.9 dB/K atEl = 45degat 18.75 GHz. Interference with the 20 GHz band terrestrial radio relay system in extremely near field was experimentally studied. Results show that the terrestrial system's antennas can be installed closely up to about 20 m without serious interference.