Crystal oscillator with a temperature-compensating analog circuit
First Claim
1. A crystal oscillator of a temperature compensating type, comprising:
- an oscillator circuit comprising;
a crystal element having a natural resonant frequency, said natural resonant frequency being a particular frequency at a particular temperature and having a frequency-temperature response where said natural resonant frequency is accompanied with a frequency fluctuation from said particular frequency which is dependent on a temperature variation from said particular temperature so that a temperature response of a frequency fluctuation ratio to said particular frequency is represented by a first cubic curve of a positive cubic coefficient with an inflection point at said particular temperature, anda varicap diode having a variable capacitance controlled by a varicap control voltage level of a varicap control signal applied thereto,said variable capacitance of said varicap diode having a particular capacitance at a particular varicap control voltage level of said varicap control signal applied thereto and having a capacitance-voltage response such that said variable capacitance varies in inverse proportion to said varicap control voltage level varied,said oscillator circuit oscillating at an oscillating frequency generally determined by said natural resonant frequency and controlled by said varicap diode, andsaid oscillating frequency of said oscillator circuit having a predetermined frequency when said oscillation temperature is at a predetermined oscillation temperature and when said variable capacitance is at a predetermined capacitance, said oscillating frequency having a frequency-capacitance response where said oscillating frequency has a frequency deviation from said predetermined frequency in response to variation of said variable capacitance so that a frequency deviation rate to said predetermined frequency changes in inverse proportion to said variable capacitance varied;
a temperature detecting circuit comprising a temperature sensor disposed in the vicinity of said oscillator circuit, said temperature detecting circuit detecting, as an oscillation temperature, a temperature circumferential of said oscillator circuit to produce, as a detected voltage signal, a voltage signal with a voltage level, as a detection voltage level, said detected voltage signal having a predetermined detection voltage level when said oscillation temperature is at said predetermined oscillation temperature, said detected voltage signal varying, in said detection voltage level, in linear proportion to variation of said oscillation temperature; and
a temperature compensating circuit for analog-processing said detecting voltage signal to produce said varicap control signal having said varicap control voltage level, said varicap control signal having a predetermined varicap control voltage level when said oscillation temperature is at said predetermined oscillation temperature, said varicap control voltage level varying in response to said detected voltage signal varying dependent on variation of said oscillation temperature along a second cubic curve of a predetermined negative cubic coefficient with an inflection point at the predetermined varicap control voltage level, said varicap control signal being applied to said varicap diode to thereby control said variable capacitance to maintain said oscillating frequency stable against variation of said oscillation temperature;
said temperature compensating circuit comprising;
converted voltage signal producing means responsive to said detected voltage signal for producing a converted voltage signal, said converted voltage signal being a zero voltage level when said detected voltage signal represents said predetermined detection voltage level, and having a converted voltage level varying in response to variation of said detection voltage level of said detected voltage signal along a third cubic curve having no turning value with an inflection point at said zero voltage level;
basic voltage signal producing means for producing a basic voltage signal, said basic voltage signal having a predetermined basic voltage level corresponding to said predetermined varicap control voltage level;
set voltage signal producing means for producing a set voltage signal, said set voltage signal having a set voltage level equal to said predetermined detection voltage level; and
varicap control signal producing means for comparing said detected voltage signal and said set voltage signal to produce a voltage difference signal, and combining said voltage differential signal, said converted voltage signal, and said basic voltage signal to produce said varicap control signal which has, as said predetermined varicap control voltage level, a voltage level equal to the basic voltage at said predetermined oscillation temperature.
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Accused Products
Abstract
A temperature-compensated quartz oscillator comprises a stabilized power supply circuit (1) for supplying a constant voltage, an oscillation circuit (2) comprising a quartz resonator (21) and a varicap (22), a temperature detecting circuit (3) for producing a detected voltage signal (VTemp) corresponding to an oscillator part temperature by the use of the temperature-voltage characteristic of a temperature detecting element located in the vicinity of the oscillation circuit (2), and a temperature characteristic compensating portion (4) for producing through analog processing of the detected voltage signal (VTemp) a varicap control voltage signal (VVR) to be supplied to the varicap (22).
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Citations
21 Claims
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1. A crystal oscillator of a temperature compensating type, comprising:
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an oscillator circuit comprising; a crystal element having a natural resonant frequency, said natural resonant frequency being a particular frequency at a particular temperature and having a frequency-temperature response where said natural resonant frequency is accompanied with a frequency fluctuation from said particular frequency which is dependent on a temperature variation from said particular temperature so that a temperature response of a frequency fluctuation ratio to said particular frequency is represented by a first cubic curve of a positive cubic coefficient with an inflection point at said particular temperature, and a varicap diode having a variable capacitance controlled by a varicap control voltage level of a varicap control signal applied thereto, said variable capacitance of said varicap diode having a particular capacitance at a particular varicap control voltage level of said varicap control signal applied thereto and having a capacitance-voltage response such that said variable capacitance varies in inverse proportion to said varicap control voltage level varied, said oscillator circuit oscillating at an oscillating frequency generally determined by said natural resonant frequency and controlled by said varicap diode, and said oscillating frequency of said oscillator circuit having a predetermined frequency when said oscillation temperature is at a predetermined oscillation temperature and when said variable capacitance is at a predetermined capacitance, said oscillating frequency having a frequency-capacitance response where said oscillating frequency has a frequency deviation from said predetermined frequency in response to variation of said variable capacitance so that a frequency deviation rate to said predetermined frequency changes in inverse proportion to said variable capacitance varied; a temperature detecting circuit comprising a temperature sensor disposed in the vicinity of said oscillator circuit, said temperature detecting circuit detecting, as an oscillation temperature, a temperature circumferential of said oscillator circuit to produce, as a detected voltage signal, a voltage signal with a voltage level, as a detection voltage level, said detected voltage signal having a predetermined detection voltage level when said oscillation temperature is at said predetermined oscillation temperature, said detected voltage signal varying, in said detection voltage level, in linear proportion to variation of said oscillation temperature; and a temperature compensating circuit for analog-processing said detecting voltage signal to produce said varicap control signal having said varicap control voltage level, said varicap control signal having a predetermined varicap control voltage level when said oscillation temperature is at said predetermined oscillation temperature, said varicap control voltage level varying in response to said detected voltage signal varying dependent on variation of said oscillation temperature along a second cubic curve of a predetermined negative cubic coefficient with an inflection point at the predetermined varicap control voltage level, said varicap control signal being applied to said varicap diode to thereby control said variable capacitance to maintain said oscillating frequency stable against variation of said oscillation temperature; said temperature compensating circuit comprising; converted voltage signal producing means responsive to said detected voltage signal for producing a converted voltage signal, said converted voltage signal being a zero voltage level when said detected voltage signal represents said predetermined detection voltage level, and having a converted voltage level varying in response to variation of said detection voltage level of said detected voltage signal along a third cubic curve having no turning value with an inflection point at said zero voltage level; basic voltage signal producing means for producing a basic voltage signal, said basic voltage signal having a predetermined basic voltage level corresponding to said predetermined varicap control voltage level; set voltage signal producing means for producing a set voltage signal, said set voltage signal having a set voltage level equal to said predetermined detection voltage level; and varicap control signal producing means for comparing said detected voltage signal and said set voltage signal to produce a voltage difference signal, and combining said voltage differential signal, said converted voltage signal, and said basic voltage signal to produce said varicap control signal which has, as said predetermined varicap control voltage level, a voltage level equal to the basic voltage at said predetermined oscillation temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification