Noise in Receiver

Roberto

I am measuring a receiver operating at around 1 Ghz. I have a Spectrum Analyzer at the output and a RF Generator at the Input. I  decreses the RF level at the Input up to a level that is almost not observable in the Spectrum Analyzer. Surprisingly, the level is below the Noise level predicted as   =-174 + 10 log BW . Any idea about what is wrong?

Alivin

你用中文描述一下吧

kingder

<P>会不会是接收机有较大的增益，将输入信号放大，导致实际输入到频谱分析仪的信号功率接近或者超过噪底了？</P>[br]<p align=right><font color=red>+3 RD币</font></p>

edit

<P>Can you give more details?</P><P>Confusion in receiver BW vs. SA BW? Using noise marker that already compensates BW? Generator level higher than expected due to attenuator leakage?</P>[br]<p align=right><font color=red>+3 RD币</font></p>

52RD的小妖精

I didn't understand your question

HWRD

请问Receiver BW和SA BW 概念有什么不同？

wilsonchen

<P>Hi,</P><P>First you may need to check your target IQ setpoint power seen as S.A, and maybe the output already be smaller than your target when your input approaching to -174+BWLog.</P><P>I believe you already correct RBW/VBW, and maybe your receiver really good!</P><P>You can try to calculate S/N ratio an thus get your receiver NF number.</P><P>Regards,</P><P>wilson</P>[br]<p align=right><font color=red>+5 RD币</font></p>

ayuyu

<P>如果你的signal 不是wideband的，那么很明显你的测试将是有问题的。只有宽带信号才有可能在噪声里被接受和解调（它有个扩频增益）。如果是窄带信号，那么就是你的SP的setup有问题，或者是你的SP的noisefloor太高。我想你应把详细的测试环境告诉大家，这样才有可能知道是何原因。</P>[br]<p align=right><font color=red>+5 RD币</font></p>