Question about ADC noise in NF calculation
时间：04-05
整理：3721RD
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Hi,
Here is a new question following previous link. I don't understand the colored word with underline. Could you explain it to me in more detail?
Thanks,
The impact of using gain control rather than a very-high-resolution ADC to maximize dynamic range is this: First, by implementing AGC, very high gain can be used to completely suppress the ADC noise under small signal conditions. In transceivers such as the AD935x, the ADCs contribute just 0.15 dB to the NF at maximum gain. If, instead, a high-resolution ADC were used, at least 0.5 dB of NF would have to be budgeted to the ADC because ADC dynamic range is so expensive. Since path loss with distance is proportional to 30 log(d), the 0.5 dB higher NF of the fixed gain system would reduce the maximum range by about 4%.
How to understand "6.5 dB NF and implementation loss"?
BTW, it should be read in this way?
Here is a new question following previous link. I don't understand the colored word with underline. Could you explain it to me in more detail?
Thanks,
The impact of using gain control rather than a very-high-resolution ADC to maximize dynamic range is this: First, by implementing AGC, very high gain can be used to completely suppress the ADC noise under small signal conditions. In transceivers such as the AD935x, the ADCs contribute just 0.15 dB to the NF at maximum gain. If, instead, a high-resolution ADC were used, at least 0.5 dB of NF would have to be budgeted to the ADC because ADC dynamic range is so expensive. Since path loss with distance is proportional to 30 log(d), the 0.5 dB higher NF of the fixed gain system would reduce the maximum range by about 4%.
How to understand "6.5 dB NF and implementation loss"?
BTW, it should be read in this way?
Hi,
The conclusion is useful and interesting. I want to know how to get it?
Thanks,
If the ADC is allowed to contribute 0.5 dB to the receiver's NF, the ADC noise must be about 10 dB below the other noise sources of the receiver.