Phased array antennas for mobile communications

An antenna system including antenna elements and a tracking method is considered a key technology in mobile communication systems. A phased array antenna has been considered the most favorite candidate because of many attractive characteristics such as a low and compact profile, high-speed tracking and potentially low cost performance for vehicle antennas in mobile communications. On the other hand, it has several such disadvantages as beam steering error, loss in feed lines and an increase of noise level in a receiving frequency band. Some of phased array antennas have already been used in satellite communications, and some of them are under development. This paper overviewed basic performance and some examples of phased array antennas for especially satellite mobile communications.     

卫星固定站天线控制系统改造的探讨

卫星固定站是指在特定站点的卫星通信地球站,通常是通过同步轨道通信卫星进行卫星业务的通信。卫星固定站大多使用的是2.4 m-7.3 m静中通天线,早期的工程施工中大部分天线未安装自动控制系统,靠手动控制驱动电机进行对星。文章对Ku频段卫星固定站天线控制系统改造进行探讨,提出更好的改造方案。     

The role of technology in influencing future civil communicationssatellites

Technology, both as an enabler and as a driver of new and improved communication satellites, is discussed. A brief look at the beginnings and evolution of satellite communications is given to reveal the continuing influence of technology over the past 25 years. An assessment of the current state of the art which serves as a benchmark representing how far technology has come and as a basis for comparison for future possibilities is presented. A short tutorial on communications satellite basics is presented, followed by an assessment of technologies used for satellite antennas and signal amplification and routing. A discussion of future service requirements follows, and emerging technologies are identified along with possible improved communications capabilities that can result from them. The outlook for the role of technology for future communication satellites is summarized     

On Attaining Lower Sidelobes and New Antenna Envelopes for Better Orbit Spectrum Utilization in Satellite Broadcasting

The orbit spectrum is a natural resource for satellite communications which must be utilized efficiently in order to meet the rapid growth in demand for communication capacity 1,2 and which may become very crowded in the near future. Efficient allocation of this resource has been approached from many different aspects, such as technical, operational, practical and economic. Different methods of improving this utilization efficiency have been proposed, such as reducing the inhomogenity among satellites and defining limitations on system parameters. This report focuses the discussion on a simple method: improving the antenna patterns used in satellite systems, on both the satellite antennas and the ground station antennas. Only broadcasting applications are considered. The discussion includes how the antenna envelope can be improved, how this improvement can be interpreted in terms of orbit spectrum utilization efficiency, and whether this improved envelope is actually realizable and feasible, considering practical aspects.     

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     

Radome crosspolarisation on Intelsat standard 'A' communication satellite antennas

The reduction in size of Intelsat standard 'A' satellite communication antennas from 30.5 m to 15 m in diameter has necessitated the computation of depolarisation effects when the smaller antennas employ metal and dielectric space frame radomes for hardening and protection. Using the standard 15 m antennas enclosed by appropriately scaled-down metal and dielectric space frame radomes, the crosspolar discrimination (XPD) and the boresight shift (BS) have been computed close to antenna axis at 4 and 6 GHz. Comparison with the larger 30.5 m antennas enclosed by 45 m radomes have been made. It is reported that within 0.1 degrees of antenna boresight, the XPD introduced by the radomes does not exceed 33.0 dB as the worst case at 4 GHz. In particular, the Intelsat Specification of 30.7 dB for the XPD within the antenna's tracking beamwidth in clear weather conditions for frequency re-use satellite communication systems is satisfied. The BS is negligibly low.<>     

可重构全息超表面辅助卫星通信关键技术

超密集低地球轨道卫星通信网络能弥补传统地面网络频谱资源稀缺、覆盖范围有限的不足,有潜力提供全球大规模接入的高速率服务。由于卫星的高速移动性,卫星通信对天线性能,如波束控制能力和天线增益等,也提出了更为严苛的要求。因此,对一种新型的超材料天线——可重构全息超表面（reconfigurable holographic surface,RHS）辅助卫星通信展开了研究。RHS采用全息原理对超材料单元进行电控,从而实现波束成形。基于 RHS 的硬件结构和全息工作原理,提出了一种 RHS 辅助多卫星通信方案,该方案同时考虑卫星跟踪和数据传输。同时,设计了全息波束成形优化算法以最大化和速率。仿真结果验证了所提方案的有效性并表明了相较于传统相控阵天线,RHS提供了一种成本效益更高的卫星通信支持方式。     

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.     

一种新型实用的天线控制器的设计

随着卫星通讯技术的不断发展,卫星的数量不断增加,对卫星天线伺服设备的要求也越来越高,为了保证系统的不间断通讯,同时避免对空间微波环境产生不必要的干扰,高可靠的天线控制器起到了重要的作用。特别是大口径的卫星天线,由于其波束宽度窄,对天线的角度控制要求更高。介绍了一种基于系统级单片机的实用型大口径卫星通讯地面站天线控制器的基本设计,阐述了该系统的设计特点,并对主要部分的软硬件实现方式进行了说明。     

Pointing losses in single-axis and fixed-mount earth-station antennas due to satellite movement

There are substantial cost advantages in the use of single-axis or fixed-mount earth-station antennas, thus reducing or eliminating the need for autotracking in earth-stations operating with quasi-stationary satellites. Such cost advantages are more relevant in small antennas where the tracking system represents a larger percentage of the overall cost. In addition, small antennas are particularly suitable to be operated without autotracking, owing to their wider half-power beamwidth. This paper describes a model for calculating the antenna pointing loss as a function of the antenna diameter, operating frequency band, satellite station-keeping tolerances, and the relative geometry between the earth-station and the satellite. The model has been extensively used in the development of INTELSAT's IBS and VISTA services as well as in domestic leases. Although the model has been developed based on orbital mechanics equations, its emphasis is towards earth-station and systems engineering applications. Some example calculations and results obtained through an HP-41 CV programmable calculator are also provided.     

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.     

The antenna system of a distress buoy for use in a maritime satellite communication system (MARSAT)

Two different types of antenna systems for a distress buoy for use in the maritime satellite communication system (MARSAT) are described. The buoy radiates signals alternately on the frequencies 2182 kHz (medium frequency (MF) beacon) and 1.65 GHz (Lband beacon). TheLband antennas had to be combined with the MF antenna of a commercial buoy. The antenna systems have been tested with success during the application technology satellite (ATS-6) experiments and during a previous European Space Research Organization (ESRO) balloon communication experiment [1].     

The transmission capacity of multibeam communication satellites

The transmission capacity which can be provided by a geosynchronous multiple-beam satellite employing frequency reuse is studied. Like all communication channels, satellite capacity is limited by available power, transmission bandwidth, and noise. In addition, factors peculiar to satellite links include cochannel interference among neighboring beams, channel nonlinearity, nonuniformly distributed traffic, and for satellites operating at frequencies above 10-GHz, rain attenuation. The effects of these factors upon the capacity of a satellite system are examined in detail. Results for a 12/14-GHz system with assumed satellite parameters compatible with a space shuttle launch and small 5 m earth station antennas show that a capacity of about 30 Gbit/s can be provided if the unavailability due to rain outage is no greater than 0.1 percent, and that about 10 Gbit/s can be provided for an unavailability no greater than 0.01 percent. Efficient utilization of the geosynchronous arc is also explored, and current trends in communication satellites are discussed.     

The development of radial line slot array antenna for direct broadcast satellite reception

Microwave antennas are extensively used in communications systems such as satellite, television and high-speed data transmission due to their wide and absolute bandwidth. Among the variety of microwave antennas, satellite communication commonly adopts an antenna of parabolic dish type, despite some drawbacks. In a primary fed design, there is considerable aperture blockage. An offset parabolic antenna design, which then eliminates the blockage, is susceptible to physical damage as its feed is significantly exposed from the body of reflector. The radial line slot array (RLSA) type antenna is thus designed to cope with the problems encountered in parabolic antennas. RLSA is a planar antenna suitable for direct broadcast satellite (DBS) reception, with advantages including high radiation efficiency (high gain), low profile, low cost and feed rear-mounted. The prototype development started with the selection of the cavity's dielectric material and construction of the feeding structure of coaxial-to-waveguide transition. Within the frequency band of interest, between 10.95 and 11.7?GHz, results, is showed a lower than ?10?dB of return loss. A DBS receiver test-bed had been developed to test the constructed antenna prototypes and it revealed that the prototype has the capability of receiving TV programs from DBS.     

均匀照射赋形反射面天线设计

为提高反射面天线的照射均匀性，利用波束赋形技术设计一款工作在15 GHz的高性能偏置反射面天线.该天线由一个非均匀有理B样条（non-uniform rational B-splines，NURBS）反射面和一个介质棒馈源组成，NURBS反射面通过物理光学法结合Nelder-Mead优化算法来赋形，从而获得理想的天线辐射场.仿真结果表明，赋形后的反射面天线相对旁瓣电平低于-20 dB，增益在-2.7°~2.7°的波束范围内超过20 dBi，且浮动不超过1 dB.该天线具有结构简单、旁瓣低、增益均匀的特点，在卫星通信等领域具有重要作用.     

一种机载UHF 频段小型化宽带全向天线设计

机载的安装环境对机载设备的尺寸和重量提出了更高的要求。全向天线是近距离空间链路信号传输的有效技术手段,设计一种机载重量轻、小型化的全向天线具有非常重要的现实意义。区别于传统马刀天线,所设计的天线在尺寸、重量上得到了很大的缩减;为了满足共形要求,天线采用了微带形式,2 mm 的剖面能够根据载体的具体形式进行共形设计;采用双臂组合单极子形式进行阻抗加载,天线实现了超过50% 的驻波带宽(驻波小于2. 5)。通过测试,天线样机的实测性能与仿真结果吻合很好。     

Combating sun outage in satellite television distribution systems

Two methods of sun outage avoidance in satellite television transmission are discussed. Each method requires two satellites and dual-beam antennas. The two C-band satellites transmit identical programs at the time when the sun outage period occurs. The separation of the spacecraft is dependent on the dual-feed earth station antenna size. For large television receive-only antennas, the separation must be small; for small antennas, or antennas with large beamwidths, the satellite separation can be large. If the separation is larger than 8° on the geosynchronous arc, only one transmit station is required to transmit program information. Scaling this system for Ku-band use is then considered. It is concluded that in a Ku-band direct-broadcasting system with earth station antenna diameters of 1-m and below, the rise in noise temperature due to sun outage is not significant and can be overcome by a modest amount of system margin, equivalent to that normally provided against rain fades