Time reversal cavity path and its influence on signal to noise ratio
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摘要: 时间反演具有时空聚焦特征,在许多方面有着潜在的应用。其中,基于时间反演腔的系统是一种主要的反演系统,可用于脉冲压缩、波束成形、微扰探测等。时间反演腔通常是一个电大的微波混沌腔,内部电磁波的传播具有明显的多径特征,即时间色散特征。因此,在时间反演过程中,反演腔可对反演信号进行相位补偿,重构出初始信号,从而在初始位置形成脉冲的时间压缩和空间聚焦。为了拓展时间反演腔的实际应用,本文基于多径信道模型研究腔体参数对反演性能的影响,重点分析路径的衰减特征、串扰特征和叠加特征对反演信噪比的影响,并总结给出影响反演信噪比的主要参数以及基本规律。Abstract: Time reversal has the characteristics of spatiotemporal focusing and has potential applications in many field. The reversal system based on time reversal cavity (TRC) is an important reversal system. It can be used for pulse compression, beam forming, perturbation detection and so on. The TRC is usually an electrically large microwave chaotic cavity, and the propagation of electromagnetic wave in it has obvious multipath characteristics. That is, time dispersion characteristics. Therefore, in the process of time reversal, the TRC can compensate the phase of the reversal signal and reconstruct the initial signal, which can give time compression and spatial focusing at the initial position. To enhance the application of TRC, this paper studies the influence of cavity parameters on the reversal signal to noise ratio (SNR) based on the multipath channel model, focusing on the analysis of the influence of path attenuation, crosstalk and superposition. Moreover, it summarizes the main parameters and basic laws affecting the SNR.
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Key words:
- time reversal cavity /
- multipath channel model /
- multipath effect /
- signal to noise ratio
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表 1 腔体损耗的路径统计特征与信噪比的关系
Table 1. Relationship between cavity loss and signal to noise ratio
No. conductivity/(S·m−1) mean standard deviation mainlobe SNR/dB 1 ∞ 0.0056 0.0085 0.45 18.3 2 3.56e+7 0.0044 0.0072 0.26 15.9 3 1e+6 0.0037 0.0065 0.23 15.6 4 1e+5 0.0017 0.0039 0.11 14.9 表 2 不同结构腔体路径统计特征与信噪比的关系
Table 2. Relationship between cavity structure and signal to noise ratio
No. structure mean standard deviation mainlobe SNR/dB 1 0.0049 0.0069 0.43 18.4 2 0.0034 0.0055 0.34 17.6 3 0.0016 0.0017 0.174 12.8 4 0.0012 0.0012 0.16 14.1 表 3 腔体尺寸与信噪比的关系
Table 3. Relationship between cavity size and signal to noise ratio
No. size/(mm×mm) decay time mean standard deviation SNR/dB 1 400×300 1.14 0.0069 0.0136 14.0 2 600×400 1.60 0.0056 0.0085 18.3 3 800×600 2.28 0.0044 0.0058 18.9 -
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