National Semiconductor Corporation

William J Huff

Lawrence Jarrett Malone

Daniel R Meacham

A method includes identifying a setting for a capacitor bank associated with a voltage-controlled oscillator in a closed-loop phase-locked-loop. The setting represents a combination of one or more capacitors in the capacitor bank. The method also includes estimating a gain introduced by the closed-loop phase-locked-loop when the oscillator operates using the identified setting. The method further includes estimating a response of a loop filter in the phase-locked-loop and identifying one or more coefficients for a digital filter using the identified gain and the identified loop filter response. The digital filter is operable to filter an input signal. In addition, the method includes modulating the filtered input signal using the phase-locked-loop to produce an output signal.

Frequency synthesizer using digital pre-distortion and method

A frequency shift keyed (FSK) receiver for demodulating an incoming transmitted signal comprising: 1) a phase-locked loop for receiving an oscillator reference signal having a frequency F1 and generating a reference carrier frequency signal having a desired frequency N1(F1), wherein N1 may be a non-integer value, the phase-locked loop comprising: a) a phase detector having a first input for receiving the oscillator reference signal and a second input; and b) a frequency divider circuit for dividing an actual frequency of the reference carrier frequency signal by an adjustable integer value N2 applied to a control input of the frequency divider circuit to generate a feedback signal applied to the second input of the phase detector. The FSK receiver further comprises: 2) a frequency discriminator that receives the incoming transmitted signal and the reference carrier frequency signal and generates a correction signal corresponding to a difference between a center frequency of the incoming transmitted signal and the actual frequency of the reference carrier frequency signal; and 3) a delta-sigma modulator controlled by the correction signal operable to generate a sequence of integers having an average value of N2 over a defined time period, wherein the sequence of integers are applied to the control input of the frequency divider circuit.

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La Jolla, CA, United States of America

William J Huff