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# How to calculate noise figure on SINAD of radio spec.?

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#### cliffliu

##### Junior Member level 3
I would like to calculate link budget for two radio communication.
My link budget sheet is using noise figure but the radio receivier capability specification are SINAD of unit.
How to transform SINAD into noise figure?
Thanks

First transform 0.18uV into dBm,and use the following equation to transform:
Pin(0.18uV------>dBm)+174dBm/Hz-12-10logB=NF(dBm)
B-----the bandwidth.
cliffliu said:
I would like to calculate link budget for two radio communication.
My link budget sheet is using noise figure but the radio receivier capability specification are SINAD of unit.
How to transform SINAD into noise figure?
Thanks

My radio each channel is 25KHz.
10*log(((0.18uV * 0.001)^2)/50)= -91.88dBm
NF= -91.88dBm + 174dBm/Hz -12dB -10*log(25KHz)= 26.14dB
Correct?
And then,
Why BW in dB is 10*log(BW)? Not 20*log(BW)?

Thanks you!

Conversion uV to dBm in 50ohms is:
10*LOG(((uV/1000000)^2)/50)+30 = dBm
Sensitivity = 0.18uV = -121.9dBm

The S/N ratio required at the input of a detector depends on the particular measure of receiver sensitivity. For example 12dB SINAD (audio measurement) may require 5dB S/N ratio at detector IF frequency.

NF(dB) = Sensitivity(dBm) + 174 – 10*LOG(BW in Hz) – S/N =
= -121.9 + 174 – 43.97 – 5 = 3.1dB

for Pin=Ps*B Ps:dBm/Hz transform into dBm,you will get the equation:10*log(BW) not 20log(BW)
cliffliu said:
My radio each channel is 25KHz.
10*log(((0.18uV * 0.001)^2)/50)= -91.88dBm
NF= -91.88dBm + 174dBm/Hz -12dB -10*log(25KHz)= 26.14dB
Correct?
And then,
Why BW in dB is 10*log(BW)? Not 20*log(BW)?

Thanks you!

vfone said:
The S/N ratio required at the input of a detector depends on the particular measure of receiver sensitivity. For example 12dB SINAD (audio measurement) may require 5dB S/N ratio at detector IF frequency.

NF(dB) = Sensitivity(dBm) + 174 – 10*LOG(BW in Hz) – S/N =
= -121.9 + 174 – 43.97 – 5 = 3.1dB
Does the S/N required will present on radio specification?
Will be testing on each radio if we want to know the radio S/N?
Or, the 5dB S/N is a general specification.

Thank you!

S/N at the input of the detector is a general specification and is part of the RF system analysis.

can anyone guide me how to obtain the S/N for FM and how to calculate the distortion of 25% for a given 12dB SINAD.

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