基于并行采样的SDR射频直采结构研究

发布时间：2018-06-04 23:27

本文选题：软件无线电 + 射频直接采样　；参考：《哈尔滨工程大学》2015年硕士论文

【摘要】：随着FPGA、DSP等硬件平台的迅猛发展,数字信号的处理速度也不断地增高,数字化处理技术被广泛应用,模拟信号的数字化成为关键。伴随着软件无线电技术的兴起与发展,如何将射频前端的模拟部分高效地数字化处理,成为了大家关注的焦点,在现有的ADC硬件采样频率和采样精度的前提下,将模拟带宽可达到GHz的超宽频带信号采样为数字化信号成为了一个难点。为适应软无平台对宽带信号处理的需求,迫使射频前端结构向前发展,为获得更高输入带宽,对ADC的采样速率和精度提出很高要求。通过多片ADC并行采样的结构,弥补了传统采样方式高采样速率却只能对应不足12 bit采样位数的缺点,可以实现既有足够高的采样数率,又能获得足够高的采样精度,使得射频前端结构进一步接近理想射频直接采样结构。本文对比了目前软件无线电射频前端的三种采样结构,提出采用基于混合滤波器组的并行采样系统来取代多级混频超外差式结构的射频直采系统;推导了完全重构条件和功率互补关系,结合遗传算法设计优化了一个满足功率互补的两通道混合滤波器组,完成了一个基于混合滤波器组的射频直采验证系统仿真。本文首先分析了软件无线电平台的射频前端采样结构的发展背景,简单对比了三种采样结构的原理和优缺点,提出了射频直接采样结构的优势和难点所在;简单概述包括多速率采样、滤波器组、ADC采样的数字信号处理的关键技术,掌握了它们的基本原理。其次对比了三种ADC并行采样结构的原理,重点研究了 HFB系统,推导了信号的完全重构条件和两通道模拟滤波器组的功率互补条件,推导了传递函数系数优化表达式,结合遗传算法的优点,在遗传算法工具箱中优化了传递函数系数,得到具有严格功率互补关系的模拟滤波器组。再其次,通过IFFT算法推导,得到了综合滤波器组设计优化的算法,提出基于遗传算法优化系统延迟参数和滤波器阶数,设计出满足功率互补关系的混合滤波器组,并对比分析了不同类型的HFB结构的误差性能。最后,设计了一个基于BPSK调制信号解调的射频直接采样系统,采用了两通道功率互补的HFB并行采样结构,分析不同信噪比条件下的BPSK解调误码率曲线,验证了 HFB结构在射频直采系统中替代多级混频结构的有效性。
[Abstract]:With the rapid development of FPGA DSP and other hardware platforms, the processing speed of digital signal is also increasing. The digital processing technology is widely used, and the digitalization of analog signal becomes the key. With the rise and development of software radio technology, how to digitalize the analog part of RF front-end has become the focus of attention. Under the premise of sampling frequency and sampling precision of existing ADC hardware, It is difficult to sample the ultra-wideband signal with analog bandwidth up to GHz into digital signal. In order to meet the requirement of wideband signal processing in soft platform, the RF front-end structure is forced to develop forward. In order to obtain higher input bandwidth, the sampling rate and precision of ADC are very high. By using multi-chip ADC parallel sampling structure, the shortcomings of traditional sampling method with high sampling rate but only less than 12 bit sampling bits can be remedied. It can achieve both high sampling rate and high sampling accuracy. The RF front end structure is closer to the ideal RF direct sampling structure. In this paper, three sampling structures of the RF front end of software radio are compared, and a hybrid filter bank based parallel sampling system is proposed to replace the multistage mixed-frequency superheterodyne system. The complete reconstruction condition and power complementary relation are derived. A two-channel hybrid filter bank is designed and optimized with genetic algorithm. A hybrid filter bank based on hybrid filter bank is simulated for RF direct-sampling verification system. In this paper, the development background of RF front-end sampling structure of software radio platform is analyzed, the principle, advantages and disadvantages of three sampling structures are compared, and the advantages and difficulties of RF direct sampling structure are put forward. This paper briefly introduces the key technologies of digital signal processing including multi-rate sampling and filter bank ADC sampling, and grasps their basic principle. Secondly, the principle of three ADC parallel sampling structures is compared, and the HFB system is studied emphatically. The complete reconstruction condition of signal and the power complementary condition of two-channel analog filter bank are derived, and the optimal expression of transfer function coefficient is derived. Combining the advantages of genetic algorithm, the transfer function coefficients are optimized in the genetic algorithm toolbox, and the analog filter banks with strict power complementary relation are obtained. Secondly, through the derivation of IFFT algorithm, the design optimization algorithm of synthetic filter banks is obtained, and a hybrid filter bank based on genetic algorithm is proposed to optimize the system delay parameters and filter order, which satisfies the power complementary relationship. The error performance of different HFB structures is compared and analyzed. Finally, a radio frequency direct sampling system based on BPSK modulation signal demodulation is designed. The BPSK demodulation error rate curve of BPSK demodulation under different SNR conditions is analyzed by using a two-channel parallel sampling structure with complementary power. The effectiveness of replacing multistage mixing structure with HFB structure in RF direct-mining system is verified.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN92;TN713

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