When there is a frequency drift
in the input signal the estimated output from the observer has error in magnitude and phase.
However Allan variance cannot rule out frequency drift
. Especially when the drift is almost equal to Allan variance for certain averaging time, if we use Allan variance to calculate [[sigma].sup.2.sub.12]([tau]), [[sigma].sup.2.sub.13]([tau]), and [[sigma].sup.2.sub.23]([tau]) and then calculate [[sigma].sup.2.sub.1]([tau]), [[sigma].sup.2.sub.2]([tau]), and [[sigma].sup.2.sub.3]([tau]), the result cannot reflect the real situation of atomic clock.
Active methods mainly include the active frequency drift
(AFD), slip-mode frequency shift (SMS), and Sandia frequency shift (SFS) methods, which can create a continuous trend to change the frequency during islanding [18-20].
Combined with the Eon[TM] film thickness controller, which is capable of real-time correction of any natural frequency drift
in the crystal during heating, any process that requires heated crystals or high measurement accuracy will see exponential improvement, leading to the highest accuracy possible as well as enabling continuous crystal operation without cooling.
Features include a typical -152-dBm DANL; [+ or -] 0.1 ppm annual aging rate, which reduces frequency drift
; one-button PowerSuite operation (CHR OBW, ACPR, SEM, and spectrogram), which makes power measurements and signal monitoring simple and intuitive; an optional 7-GHz tracking generator with a built-in VSWR bridge, which supports transmission and reflection measurements; a demodulation mode to easily and cost-effectively gain more insight into AM, FM, ASK, and FSK signal analysis; and user-definable soft keys, which provide access to seven of the most frequently used measurement setups.
Since the frequency drift
was caused by the extra Au/Cr layer, as shown in Figure 11, the TFBAR device had to be calibrated before the follow-up test.
Products of plastics are formed at higher than ambient temperatures, in addition the product temperature is changing during the technological process and is needed to evaluate the temperature effect to the resonant frequency drift
. There is a need to control polypropylene product manufacturing process at the temperature of (40 ...
Along with the automatic battery switchover for backup power, a power-fail time stamp logs the time and duration of any power failure and, for accurate timekeeping over a broad temperature range, the devices feature a wide digital-trimming range that compensates for crystal frequency drift
7, and the low-frequency offset phase noise may be caused by the frequency drift
as the ratio of dynamic impact force and depth of penetration using the frequency drift
value given by capacitive sensors 3,4,5 and depth of penetration given by inductive sensor 13,14,15.
Subsequent tests conducted at Stanford Univ., Calif., demonstrated a resonator frequency drift
over one year of less than one part per million, which is the limit of the measurement accuracy.