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[问答]

N8241A加载信号的频谱是错误的

嗨用户,我正在使用N8241A arb播放LTE信封,我遇到频谱问题。
我使用ADS提取标准信封,然后将文件转换为二进制格式并将其输入到Arb。
当我监测信号的频谱(预期的10MHz)时,我得到的频率超过300 MHz。
Arb的采样时钟为1.25GS / s,文件I加载的时间步长为6.5e-8s。
你能建议吗?
谢谢。

以上来自于谷歌翻译


     以下为原文

  Hi users,  


I am playing an LTE envelope using the N8241A arb and I am experiencing trouble with the spectrum.

I extracted the standard envelope using ADS and then I convert the file to a binary format and input this to the Arb.  

When I monitor the spectrum of the signal (10MHz expected) I get more than 300 MHz BW.

The sampling clock of the Arb is 1.25GS/s and the time step of the file I load is 6.5e-8s.  

could you advise ?

thanks.   
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孔喆

2019-7-9 13:48:51
您好Jon,从您的消息中,波形的ΔT为6.5e-8。
产生15.38 MHz的采样率,这是您对LTE信号的期望。
要使用N8241A,您需要重新采样波形以匹配该ARB中的一个可用采样率。
采样率是1.25 GHz时钟的整数除法,最低采样率是1.25e9 / 1024。
您还可以提供频率介于100 MHz和1.25 GHz之间的外部时钟。
您也可以按相同的比例分割外部时钟。
因此,您有两种方法可以解决问题:将波形数据重采样到与1.25 GHz内部时钟相关的速率;
或者提供LTE符号率的倍数的外部时钟。
麦克风

以上来自于谷歌翻译


     以下为原文

  Hello Jon,

From your message, the delta T for your waveform is 6.5e-8.  The produces a sample rate of 15.38 MHz, which is what you would expect for an LTE signal.  to use the N8241A, You will need to resample to the waveform to match one of the available sample rates in that ARB.  The sample rates are integer divisions of the 1.25 GHz clock and the lowest sample rate is 1.25e9/1024.  You can also supply an external clock of frequency between 100 MHz and 1.25 GHz.  You can also divide down the external clock by the same ratios.

So, you have two choices to resolve the problem:  Resample the waveform data to a rate related to the 1.25 GHz internal clock; or provide an external clock that is a multiple of the LTE symbol rate.

Mike
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