How to Convert dbc to db

[Prasath Ayyalraj]

Hello, I need to convert dbc to db (of signal to noise ratio). Can anyone help me on this

 

[lw1ecp]

I suppose you are talking about "decibels relative to carrier". You can find it used to measure the noise power density at a given offset from the carrier. E.g. if the noise power 10kHz away in a 1Hz bandwidth is 80dB below carrier power, then you can say SSB noise there is -80dBc. There's no need to convert to dB, the "c" simply tells you which is the reference.

 

[Prasath Ayyalraj]

Thank you for reply
In the Datasheet of AD9235BRU-40 (ADC) from Analog i am having SNR=68.5 dBc @ 100
MHz. So I am say SNR=-68.5 dB. I Am i right?

 

[axcdd]

Yes its SNR ratio calculated for maximal input/output signal.

 

[FvM]

signal to noise ration should be a positive dB number.

 

[Prasath Ayyalraj]

SO if SNR = +10dB then SNR = -10dBc and
if SNR = -10dB then SNR = +10dBc

Am i right?

 

[axcdd]

nonono ;p

lets give an example: unsigned 10 bit adc => so output is from 0 to 2^(10)-1. The maximum output value 2^(10)-1 is equall to 0 dBc. SNR is in log scale equall to Signal - Noise. Noise in dBc scale is always with '-' as it cant physically be greater then adc resolution ( max output), so SNR is always positive number.

No matter what the scale SNR with '-' means that Noise is much greater then usefull signal.