This invention is directed to a quartz crystal electronic timepiece and in particular to an electronic timepiece adapted to produce a low frequency timekeeping signal of a predetermined frequency in response to one of several high frequency standard signals produced by an oscillator circuit.
The use of quartz crystal vibrators in electronic timepieces has gained wide popularity because quartz crystal oscillator crystals utilizing such vibrators provide a highly stabilized high frequency output. Nevertheless, because such circuits have a high Q, the half-width .DELTA.f of the gain, wherein the gain of the vibrator comes down to 1/.sqroot. 2 represents a very narrow range since .DELTA.f = f/Q. Accordingly, the range of frequencies over which quartz crystal oscillator circuits can produce a stable reference frequency and the amount of deviation from the center frequency f.sub.o which can be tolerated, are extremely limited, if the accuracy of the electronic timepiece is to be maintained.
Also, because the number of divider stages is selected in order to divide the center frequency f.sub.o to a predetermined frequency, such divider circuits are not capable of providing a timekeeping signal of a predetermined frequency when the center frequency of the oscillator circuit deviates from the reference frequency. Accordingly, it is necessary to manufacture the quartz crystal vibrator and circuit incorporating same with extreme accuracy, thereby rendering mass production of integrated circuit electronic timepieces utilizing such vibrators cumbersome hence increasing the cost of manufacturing same.
USPTO Backgrounds
USPTO Backgrounds