The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> RF Design >> Figure of Merit (FOM), VCO
https://designers-guide.org/forum/YaBB.pl?num=1137460388

Message started by hrkhari on Jan 16^th, 2006, 5:22pm

Title: Figure of Merit (FOM), VCO
Post by hrkhari on 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)²/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

Title: Re: Figure of Merit (FOM), VCO
Post by Geoffrey_Coram on 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?

Title: Re: Figure of Merit (FOM), VCO
Post by hrkhari on 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