对于监视器中的nyquist limit和actual sampling要怎么理解?


#1

对于power监视器中的NYQUIST LIMIT和ACTUAL SAMPLING要怎么理解? 这里进行DFT计算的取样是怎么确定的? 我能理解DESIRED SAMPLING这个参数是最大频率的倍数; 但是对于NYQUIST LIMIT这个参数说明是可能出现的最大频率, 对于这个可能出现的最大频率要怎么理解? :yum:


#2

NYQUIST LIMIT 这参数是最大仿真频率的2倍,是不变的。
http://baike.baidu.com/link?url=dT6p6Lwb-K8OeGDP5_A_h3OswHmhHVMtYs9pIfkR98cu6p0wyauZODUPeApnLRtj5WRYqdqKHsMcsnR21kq6yTeiHeUF-wr-iw_F11a0xLdzvZq8YjcMKMjvpoffoPR1i8IsT2v1cOPNCAnLTCX1ZxrpTPChesAotiWxi-rUK1e480lcdcZwsdceYrQnA-Lt
ACTUAL SAMPLING 字面意思就是实际的采样频率
关于监视器中的几个参数
https://kb.lumerical.com/en/ref_sim_obj_monitors_global_properties.html?zoom_highlightsub=NYQUIST+LIMI

hmtoggle_plus1 Frequency Power/Profile Advanced tab
•This tab only appears for the global monitor settings. It contains advanced global settings for frequency-domain monitors. Only the MIN SAMPLING PER CYCLE can be modified by the user.
•MIN SAMPLING PER CYCLE: This parameter determines the minimum amount of sampling per optical cycle that can be used. By default, it is set at 2 (the Nyquist limit) for optimum efficiency.
•DESIRED SAMPLING: This converts the minimum points per optical cycle into an actual sampling rate in Hz.
•NYQUIST LIMIT: The Nyquist sampling limit is calculated based on the maximum frequencies that may be present in the simulation volume.
•ACTUAL SAMPLING: The actual sampling rate is the rate that will actually be used for the discrete fourier transforms (DFTs), taking into account the desired sampling rate, the Nyquist limit and the time step, dt.
•DOWN SAMPLE TIME: This is the time step downsampling.


#3

谢谢你的回答; Lumerical网站的介绍我看过了, 我也自己测试过, 光源还是监视器的最大频率的两倍等于DESIRED SAMPLING这个参数; 但是NYQUIST LIMIT又是一个大于这个最大频率的数值; 最后使用的实际频率ACTUAL SAMPLING, 又是一个更大的值; 所以搞不明白是怎么得来的?


#4

DESIRED SAMPLING这个参数可能不是最大频率的倍数,而且这些参数用户不能修改,只是做内部诊断使用。用户能修改的只是 MIN SAMPLING PER CYCLE。注意里面还有DOWN SAMPLE TIME,在那几个频率固定的情况下,改变MIN SAMPLING PER CYCLE同时会改变DOWN SAMPLE TIME。 实际的采样频率远高于所指定的NYQUIST LIMIT,估计是为了防止出现问题。


#5

谢了, 我已经解决了

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#6

如果可能请标记为已解决。