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Design >> RF Design >> How to convert dBc/Khz to dBc/Hz
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Message started by mtp3 on Jun 23rd, 2015, 11:52am

Title: How to convert dBc/Khz to dBc/Hz
Post by mtp3 on Jun 23rd, 2015, 11:52am
Hi!

I have a phase noise plot for an oscillator in which the phase noise is expressed in dBc/KHz. How can I compare this phase noise to another another oscillator with phase noise in dBc/Hz?

For example What would be a phase noise of -74dBc/Khz @ 10M offset be equal to in dBc/Hz at the same offset?

Thanks
mtp3

Title: Re: How to convert dBc/Khz to dBc/Hz
Post by mtp3 on Jun 24th, 2015, 4:08am
Hi!

Looking in to some definitions of phase noise typically the unit for phase noise is dBc/Hz. A phase noise of say -100dBc/Hz @ 1MHz offset means that the noise of the oscillator is 100dB below the carrier at 1MHz offset from the carrier in a 1Hz bandwidth.

For higher carrier frequencies it might be difficult to measure the noise power in a 1Hz bandwidth hence the unit for phase noise for such cases is dBc/KHz. So if the noise power is say -80dBm in a 1KHz bandwidth at 1MHz offset in order to map to 1Hz bandwidth we have to subtract -30 from the given noise power in 1KHz bandwidth, i.e. the noise power in 1Hz bandwidth would be -110dbm-P(carrier) would give you the phase noise at the same offset from the carrier frequency in a 1Hz bandwidth.

Title: Re: How to convert dBc/Khz to dBc/Hz
Post by baohulu on Jul 9th, 2015, 5:13am
hi.
why not integrated the dbc per hz curve from 1mhz to 1.001mhz?
-30db means the noise focus to 1hz.howerev phase noise has a skirt.  right?





mtp3 wrote on Jun 24th, 2015, 4:08am:
Hi!

Looking in to some definitions of phase noise typically the unit for phase noise is dBc/Hz. A phase noise of say -100dBc/Hz @ 1MHz offset means that the noise of the oscillator is 100dB below the carrier at 1MHz offset from the carrier in a 1Hz bandwidth.

For higher carrier frequencies it might be difficult to measure the noise power in a 1Hz bandwidth hence the unit for phase noise for such cases is dBc/KHz. So if the noise power is say -80dBm in a 1KHz bandwidth at 1MHz offset in order to map to 1Hz bandwidth we have to subtract -30 from the given noise power in 1KHz bandwidth, i.e. the noise power in 1Hz bandwidth would be -110dbm-P(carrier) would give you the phase noise at the same offset from the carrier frequency in a 1Hz bandwidth.

Title: Re: How to convert dBc/Khz to dBc/Hz
Post by nrk1 on Jul 21st, 2015, 6:54pm
-74dBc/kHz =-104dBc/Hz on average.



mtp3 wrote on Jun 23rd, 2015, 11:52am:
Hi!

For example What would be a phase noise of -74dBc/Khz @ 10M offset be equal to in dBc/Hz at the same offset?

Thanks
mtp3

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