全双工通信中的射频自干扰消除技术研究

发布时间：2018-07-24 08:14

【摘要】：全双工通信是在同一时刻以相同的频率发送和接收信号的一种信号传输方式,相比于现有的频分双工和时分双工通信方式,理论上能使频谱利用率提升一倍。实现全双工通信必须要消除设备自身发送信号对接收信号造成的自干扰。射频自干扰消除技术是在射频前端进行的自干扰处理,可以避免接收机的放大器或ADC饱和与阻塞,是全双工通信自干扰消除技术中不可或缺的一部分。本文主要针对射频自干扰消除效果与哪些因素有关、如何提高射频自干扰消除效果和带宽这些问题展开研究,所做的主要工作如下:1、论文首先对射频自干扰消除传统方案进行了对比分析。根据仿真结果得出其中的可调衰减器移相器重建方案的消除效果满足本文需求。然后又通过分析影响射频自干扰消除能力的关键因素得出结论:提高调幅精度、移相精度和延时精度可以提高干扰消除能力。这些分析结论为后续的方案设计提供了理论依据。2、本文在传统方案的基础上做了改进,设计了单路宽带射频自干扰消除电路。主要改进是在传统方案的基础上增加了一个相频斜率调整模块,使重建信号与自干扰信号的相频特性在所有频点处相差180°,两个信号相加以达到宽带消除自干扰的目的。仿真结果表明此方案在2.35 GHz~2.45 GHz的频率范围内,自干扰消除效果为32 dB~58 dB。3、论文分析并设计了多路自干扰消除方案。考虑到实际应用场景中的自干扰信号,本文分析了自干扰的多径效应,并设计了双路射频自干扰消除电路。仿真结果表明射频自干扰消除效果为40 dB~60 dB,比单路自干扰消除效果更高。4、结合优化算法的设计与实现,完成了多变量控制的单路和双路射频自干扰消除实验。由于自干扰消除电路中各调整模块含有较多的控制变量,要达到全局最优的消除效果,需要使用优化算法,论文使用了局部搜索和梯度下降两种自适应调整算法对系统进行测试。测试结果表明,对于单音信号,单路方案自干扰消除效果为60.92 dB;对于20 MHz信号,单路方案自干扰消除效果为41.09 dB,双路方案自干扰消除效果为44.63 dB;对于60 MHz信号,单路方案自干扰消除效果为32dB,双路方案自干扰消除效果为36.16 dB。
[Abstract]:Full-duplex communication is a signal transmission mode which transmits and receives signals at the same frequency at the same time. Compared with the existing frequency division duplex and time division duplex communication mode, the spectrum efficiency can be doubled theoretically. In order to realize full duplex communication, the self-interference caused by the signal sent by the device itself must be eliminated. RF self-interference cancellation is a self-interference processing in the RF front-end, which can avoid the saturation and blocking of the amplifier or ADC of the receiver. It is an indispensable part of the full-duplex self-interference cancellation technology. In this paper, we mainly focus on the research on the effect of RF self-interference cancellation and how to improve the effect and bandwidth of RF self-interference cancellation. The main work is as follows: 1. Firstly, the traditional scheme of RF self-interference cancellation is compared and analyzed. According to the simulation results, the elimination effect of the reconstruction scheme of the adjustable attenuator phase shifter meets the requirements of this paper. Then, by analyzing the key factors that affect the ability of RF self-interference cancellation, it is concluded that improving the precision of amplitude modulation, phase shift and delay can improve the ability of interference cancellation. These conclusions provide a theoretical basis for the subsequent scheme design. This paper improves on the traditional scheme and designs a single-channel wideband RF self-interference cancellation circuit. The main improvement is to add a phase frequency slope adjustment module on the basis of the traditional scheme, which makes the phase frequency characteristic of the reconstructed signal and the self-interference signal differ 180 掳at all frequency points, and the two signals are added together to achieve the purpose of wideband elimination of self-interference. The simulation results show that the self-interference cancellation effect is 32 dB~58 dB.3in the frequency range of 2.35 GHz~2.45 GHz. A multi-channel self-interference cancellation scheme is analyzed and designed in this paper. Considering the self-interference signal in practical application scene, the multipath effect of self-interference is analyzed, and a two-channel RF self-interference cancellation circuit is designed. The simulation results show that the radio-frequency self-interference cancellation effect is 40 dB~60 dB, which is higher than single-channel self-interference cancellation effect. Combined with the design and implementation of the optimization algorithm, the experiment of single-channel and two-channel radio frequency self-interference cancellation with multi-variable control is completed. Since each adjustment module of the self-interference cancellation circuit contains more control variables, it is necessary to use the optimization algorithm to achieve the global optimal elimination effect. In this paper, two adaptive adjustment algorithms, local search and gradient descent, are used to test the system. The test results show that the self-interference cancellation effect of single-channel scheme is 60.92 dB for single-tone signal, 41.09 dB for single-channel scheme, 44.63 dB for double-channel scheme for 20 MHz signal, and 44.63 dB for 60 MHz signal. The self-interference elimination effect of single-channel scheme is 32dBand that of double-channel scheme self-interference elimination is 36.16dB.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN911.4

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