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dB units of carrier to noise density ratio

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BenE View Drop Down
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    Posted: 07/February/2014 at 12:26
originally being an optics physicist with profound rf background, I am rather new to Satcom.

I am confused by the units used for carrier to noise-density ratio C/N_0. As I understand, this is just a signal to noise-density (or more precisely a signal power to noise power spectral density) ratio. Naive-minded as I am, I would use dBc/Hz as units of C/N_0, just like I know it for example from phase noise densities, which basically (leaving SSB and DSB issues aside) can be viewed as the ratio between a carrier (units dBm) and a noise level in 1Hz bandwidth (units dBm, but with the "tag" that this is the noise density integrated over 1Hz BW). Since it is a ratio, one uses dBc instead of dBm, and since it refers to 1 Hz bandwith, one uses /Hz notation, i.e. finally one arrives at dBc/Hz. One might say that it is illogical to mix the dB and per Hz in this notation, but that is the convention which I knew so far for signal to noise density ratios.

Now, for the somewhat special case of a signal to noise density, the carrier to noise density ratio, dBHz or dB-Hz notation seems to be used instead, which confuses me and leaves some rest doubt whether I have really understood C/N_0 correctly. Am I correct that the idea behind the dBHz notation as follows: In linear units, I would have the units [carrier power]/[power noise density]=(W)/(W/Hz)=Hz. If I then convert to dB, I arrive at dB referring to 1Hz, which is denoted as dBHz. Actually this seems to be a more consequent notation than the dB per Hz thing as discussed above.

Best regards and thanks for the help.
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