NIST Technical Note 1337: Characterization of Clocks and Oscillators

280 A. L. LANCE, W. D. SEAL, AND F. LABAAR-30-40LINE HARMONICS-60-80~ ·100'"~=- -120;:;­DISCRIMINATOR NOT CALIBRATEDIN THIS FREOUENCY RANGE \RADIOSTA TlON-140·160180-190 1.--1-.--'4'-0-L..JWOO-...l---l...........J....L,-..L.-....J..~.1..1 0"-:4,.--1-.--l..............J-:,--l._...................L;,-........._J......I-'-'1Q70 1FOURIER FREOUENCY I HzlFIG. 221977a.)Phase noise of 6OO-MHz oscillator multiplied to 2.4 GHz (From Lance et al..was about 500 nsec long, as noted by the first null, i.e., the reciprocal of theFourier frequency of 2 MHz is the approximate differential time delay.Note that a shorter delay line (approximately 250 nsec differential) is usedto measure the higher frequency because the delay-line discriminatorcalibration is valid only to a Fourier frequency at approximately 35~~ ofthe Fourier frequency at which the first null occurs, if a linear transferfunction is assumed.The actual transfer function of a delay-line discriminator (classic and rfbridge types) is sinusoidal, as shown in Fig. 23a. The baseband spectrumanalyzer measures power in a finite bandwidth, and as a consequence it ispossible to measure through a transfer-function null if the noise power doesnot change substantially over a spectrum-analyzer bandwidth, The followingpower relations then hold:"J+6w;2IP(w) i"'+6W;2Pmeas(w) = lI~w P(w') dw' :::: - dw' = P(w), (98)w-6w 2 ~w w- 6w. 2TN-231