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Figure of Merit (FOM), VCO (Read 6436 times)

hrkhari

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Figure of Merit (FOM), VCO
Jan 16^th, 2006, 5:22pm

Hi Guys:

I have a problem here, lets say an integrated LC-CMOS osc has a power comsumption, P=6mW, center frequency, fo=1.8GHz, phase noise L{Δf}=-116dBc/Hz, at offset frequency, Δf=600kHz, according to the formula in determining FOM, given as:

FOM=10log{(fo/Δf)�/L{Δf}.P}

I could get the FOM as 71.12, but it is stated in the journal as 177.8, can anyone assist me in calculting the FOM. Thanks in advance

Rgds

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Geoffrey_Coram

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Re: Figure of Merit (FOM), VCO
Reply #1 - Jan 17^th, 2006, 7:03am

If you convert L{Δf} from dB to 10**(-116/10), and then assume the power in the FOM expression is supposed to be in mW, I get

10*log10((1.8g/600k)**2 / 10**(-116/10) / 6) = 177.7609

Note that P should be in the denominator, 1/(L{Δf} P), so that higher power leads to a lower FOM.

It looks like you were taking the absolute value of L{Δf}, without converting it from dB?

If at first you do succeed, STOP, raise your standards, and stop wasting your time.

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hrkhari Junior Member Offline Posts: 21	Re: Figure of Merit (FOM), VCO Reply #2 - Jan 17^th, 2006, 9:55am Thanks very much Geoffrey, I have another question, does anyone knows how to compute the tuning sensitivity, KVCO of a VCO for a particular tuning voltage. Thanks in advance Rgds
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