Low power sinusoidal LC oscillator with amplitude stabilization

摘要

P:/WPDOCS/KMHSpeafica o rver Ay One/20197604 spec doc-8/31/2007 An electronic circuit presented herein sustains a resonating characteristic on a parallel LC tank circuit for use in RFID (Radio Frequency IDentification) applications or other communication circuits requiring sinusoidal signal generators. The circuit which is 5 integrated into a sinusoidal oscillator tank driver stabilizes the oscillation amplitude by maintaining an optimum energy to compensate the power loss in the tank. The tank driver emits an excitation pulse in every oscillation cycle with the aid of an inbuilt negative feedback loop which optimizes the driving pulse width. The optimized pulse is obtained from the output of a comparator which compares between the RF signal at the tank and an 10 internal voltage reference signal. The reference signal tracks a level-shifted-up envelope of the RF signal for every oscillation cycle after which it is reset to the ground level at the negative peak of the RF signal. This reference signal adapts its comparing level so as to generate the minimum required pulse duration just to sustain the continuous oscillation for maximized power efficiency. 2 RF1 11 2 RF1 11 ................ 16 if17 16 a b Voltage - - 17 Voltage - - 18 - - I. I. 1 * I I -I 1 -1.1. time time Figure 6 19 20 21 22 3 RF1 Envel. Level Shift Buffer Comparator RF1 V Vrl Peak Detect V r. Vrese Driver dr Figure 7