Apple Inc.
Linear frequency ramp generator using multi-point injection

Abstract:

A frequency synthesizer circuit included in a sensor circuit of a computer system may include a voltage-controlled oscillator circuit that may generate an oscillator signal. A three-point injection technique may be used to modulate the frequency of the oscillator signal. The three-point injection includes a low-frequency component that drives a feedback divider, and two high-frequency components that drive the voltage-controlled oscillator circuit. The strengths of the three injection points are aligned using samples of a tune signal generated using results of a comparison of a referenced signal and a frequency divided version of the oscillator signal.