US 6,611,549 B1 · Frequency switching method, voltage controlled oscillator using same and receiver for spread spectrum communication using same

Abstract

A crystal oscillator which configures a voltage controlled oscillator having a variable oscillation frequency is also used as a crystal oscillator of an oscillator for generating a fixed frequency. Control input is integrated by an integrator, a phase of a frequency-divided signal obtained by dividing a fixed clock by a frequency divider is controlled by the integrated value to vary a frequency. Every time a phase-shifting amount at the time becomes to correspond to one clock, a frequency division ratio at dividing the clock is changed from a predetermined frequency division ratio for one time of frequency division to absorb the phase shifting amount for one clock, thereby operating as a voltage controlled oscillator. Thus, the voltage controlled oscillator having the frequency accuracy of a fixed clock is realized.

Claims8

Dependent claims

A frequency switching method, comprising the steps of:

dividing a frequency of a reference signal at a given frequency division ratio;
detecting whether an integrated value obtained by a control input signal with time exceeds a predetermined range;
changing the frequency division ratio for frequency division of the reference signal by only one time when it is detected that the integrated value has exceeded the predetermined range;
resetting the integrated value to a predetermined initial value;
and
shifting a phase of the divided reference signal with a predetermined amount according to an alteration of the integrated value so that the phase of the divided reference signal is changed continuously.

3 more elements

A receiver for spread spectrum communication, comprising:

spreading code generating means, which receives a signal which is spectrum spread by a transmission side and generates from the received signal the same spreading code as the one used for the spread spectrum by the transmission side;
phase error detecting means, which detects a phase difference between a phase of the spreading code generated by the receiver and a phase of the spreading code for spreading the received signal;
and
control means, which determines the output of the phase error detecting means as control input of a voltage controlled generator, controls a generating speed of the spread signal of the spreading code generating means by the output of the voltage controlled generator, and controls to match a phase of the spread signal generated by the receiver with a phase of the spread signal for spreading the received signal,
wherein the voltage controlled generator comprises a frequency divider, into which a reference signal is input, and which performs frequency division of the reference signal at a predetermined frequency division ratio determined by the frequency dividing control and outputs a divided value;
an integrator, which integrates the phase difference detected by the phase error detecting means with time to output an integrated value and determines the output value to a predetermined value by integration control;
and
integration control means, which when output of the integrator exceeds a predetermined range, controls, according to a direction in which the output of the integrator has exceeded the predetermined range, a frequency division ratio of the frequency divider to change a predetermined frequency division ratio for only the frequency dividing operation of the next one cycle so as to set the output of the integrator to a predetermined value according to the direction in which the output of the integrator has exceeded the predetermined range.

5 more elements

Dependencies are inferred from the claim text.

Frequency switching method, voltage controlled oscillator using same and receiver for spread spectrum communication using same

Life of this patent

Frequency switching method, voltage controlled oscillator using same and receiver for spread spectrum communication using same

Life of this patent

Abstract

Claims8