星载多波束接收机用户检测技术研究

发布时间：2017-12-27 03:14

本文关键词：星载多波束接收机用户检测技术研究　出处：《国防科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：采用低轨卫星与地面用户通信,有利于控制发射成本、缩短通信距离、降低发射功率,因而在诸多领域获得了广泛应用。用户检测作为星地通信的基础,是卫星接收机面临的首要问题,但较低的轨道高度使卫星观测信号存在明显的远近效应和多普勒效应,加大了用户检测的难度。若采用单阵元天线,接收机难以兼顾高信噪比以及大范围覆盖的要求。相比之下,采用阵列天线和多波束接收技术,可形成尖锐波束指向特定方位——对应较高增益、有利于在指定方位上实现星地低功率通信。问题是,阵列天线增益高但波束宽度窄,若要求卫星在覆盖的广大区域内,能够与任何用户建立有效的突发通信,天线该指向哪个方位?接收机该如何检测用户?上述问题可概括为论文研究的基本问题:多波束接收机中如何实现用户检测?围绕这一基本问题,论文重点研究了如下关键技术问题:1、指定方位条件下的用户检测问题。为使用户检测成为现实问题,只能将卫星覆盖区域视为有限个离散点或方位,若已知某个指定方位上存在合法用户,此时用户检测可理解为从实际观测信号中提取出未知信号参数。但若用户存在性未知,则接收机只能通过某种准则来推断观测信号中用户的存在性。受轨道高度、信号发射功率等条件限制,卫星接收机要以有限的计算资源实现上述过程仍面临诸多困难,这使得指定方位条件下的用户检测成为关键问题。2、限定区域条件下的波束配置问题。由于接收阵列的非理想特性,指定点或方位上的波束并非绝对尖锐,在其临近区域内的合法用户也可能被检测到,但检测性能有所劣化。尽管这种劣化可通过加大信号观测时间来改善,但用户检测代价也将随之增大,显然有悖问题研究的初衷。因此要在不影响检测代价的同时解决性能劣化问题,阵列参数优化配置则成为用户检测的关键。3、卫星可视范围内的区域划分问题。由于波束并非绝对尖锐,可将指定点连同其临近区域看成是卫星可视范围内的一个子区域,所有子区域的集合构成了卫星覆盖的二维区域,接收机为每个子区域配置一个波束并进行用户检测。由此引出卫星顶层设计问题:为使用户检测的总代价最小,需要多少个接收波束?每个波束该如何指向?这使得卫星可视范围的区域划分成为关键。为解决上述关键技术问题,论文提出了一种基于置信概率的用户检测方案,提出了一种最小信噪比最大准则的波束优化配置方法,提出了一种结合波束数最少约束和多普勒频移分布特性的区域划分方法。这些技术方案或方法可对应解决上述三个关键技术问题,理论分析和数值计算证明了这些技术的可行性以及有效性,可为多波束接收机用户检测相关载荷的研发与设计提供参考。
[Abstract]:The use of LEO satellite to communicate with the ground users helps control the launch cost, shorten the communication distance and reduce the transmitting power, so it has been widely applied in many fields. As the foundation of satellite to ground communication, user detection is the primary problem faced by satellite receivers. However, the low orbit height has obvious near far effect and Doppler effect on satellite observation signals, which increases the difficulty of user detection. If single array antenna is used, the receiver is difficult to take into account the requirements of high signal to noise ratio and wide range coverage. In contrast, the array antenna and multi beam receiving technology can form sharp beam pointing to a specific position, which corresponds to higher gain and is conducive to the realization of satellite to ground low power communication in specified directions. The problem is, but the high gain antenna array with narrow beam width, if the requirement of the satellite in a vast area covered, to establish effective emergency communications with any user, the antenna pointing position which the receiver? How to detect the user? These problems can be summarized as the research base of this problem: how to realize the multi beam receiver in multiuser detection? Around this problem, the paper focuses on the key technical problems are as follows: 1, the specified user detection range under the condition of the problem. In order to make user detection become a real problem, the satellite coverage area can be regarded as limited discrete points or azimuth. If a legitimate user is known in a specified location, then user detection can be understood as extracting unknown signal parameters from actual observation signals. But if the existence of the user is unknown, the receiver can only infer the existence of the user in the observed signal through a certain criterion. Due to the limitation of orbit height and signal transmission power, the satellite receiver still has many difficulties to achieve the above process with limited computing resources, which makes user detection under the specified location condition a key problem. 2. The problem of beam configuration under the condition of limited area. Due to the non ideal characteristics of the receiving array, the beam on the specified point or azimuth is not absolutely sharp, and the legitimate users in its adjacent area may also be detected, but the detection performance is worse. Although this deterioration can be improved by increasing the time of signal observation, the cost of user detection will also increase, which is obviously contrary to the original intention of the study. Therefore, it is necessary to solve the problem of performance degradation without affecting the detection cost, and the optimization of array parameters is the key to the user detection. 3. The problem of regionalization in the visible range of the satellite. Because the beam is not absolutely sharp, the designated point and its adjacent area can be regarded as a sub region of the satellite visibility range. The set of all sub regions constitutes a two-dimensional area covered by satellite. The receiver configuring a beam for each sub area and user detection. This leads to the problem of satellite top-level design: how many receiving beams do we need to minimize the total cost of detection, and how to point each beam, which makes the partition of the visible range of the satellite become the key. In order to solve the key technical problems mentioned above, this paper proposes a user detection scheme based on probability, proposes a minimum signal-to-noise ratio of beam optimization configuration method of maximum criterion, proposed a shift distribution region partition method combined with the least number of beam constraints and Doppler frequency. These technical solutions or methods can solve the above three key technologies. Theoretical analysis and numerical calculation prove the feasibility and effectiveness of these technologies, which can provide reference for developing and designing related load of multibeam receiver users.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN927.2

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