JPH06276020A - Temperature compensated crystal oscillator - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a temperature-compensated crystal oscillator that is compact, low-priced, and high-performance, with easy temperature compensation adjustment. The control signal generators 102 to 107 generate control signals of the temperature detecting means 101 from control characteristics obtained by linearly approximating an ideal control curve for ideally temperature-compensating an oscillation frequency for each of a plurality of divided temperature sections. Oscillation means 1 which is generated based on the output and whose control signal uses the crystal oscillator 11.
The temperature compensation is performed by being applied to the second control terminal 15. In the predetermined input voltage range corresponding to the two continuous temperature sections, the control signal generating means monotonically increases the output voltage from zero to a predetermined maximum value in the first half temperature section and then in the second half temperature section. Then, (N + 1) number of voltage functions (N is an integer of 2 or more representing the number of the temperature intervals) having an inverse V-shaped input / output characteristic in which the output voltage monotonically decreases to zero again and the output voltage becomes zero in other cases. Circuit 1
02 to 106 and a voltage adder 107 that adds all the output voltages thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to automobile telephones,
The present invention relates to a temperature-compensated crystal oscillator used as a frequency reference oscillation source for mobile communication devices such as mobile phones and cordless phones and satellite communication devices.

[0002]

2. Description of the Related Art In recent years, with the spread of mobile communication devices such as car phones, mobile phones, cordless phones and satellite communication devices, the demand for a crystal oscillator used as a frequency reference for these devices has increased.

The temperature stability required for a crystal oscillator is, for example, ± 2.5 ppm or less in a temperature range of −30 ° C. to + 75 ° C. in a terminal of an analog type mobile phone system in North America. Further, in the terminal of the narrow band TDMA digital mobile phone system,
Performance within ± 1.5 ppm is required in the temperature range of -20 ° C to + 85 ° C. Further, in a terminal of a large-capacity analog mobile phone system in Japan, performance of ± 1.0 ppm or less is required in the temperature range of -20 ° C to + 85 ° C. In addition to the demand for frequency-temperature stability, such crystal oscillators for mobile phones can be made smaller,
There is a demand for cost reduction, which is particularly emphasized for mobile phones, and a crystal oscillator having an optimum configuration capable of meeting these requirements is strongly desired.

Since the output frequency-temperature characteristic of the crystal oscillator directly depends on the resonance frequency-temperature characteristic of the crystal unit, when a severe frequency stability is required over a wide temperature range, a temperature compensation circuit is usually required. is there. As the temperature compensation method, an analog method that uses a thermistor or other temperature sensitive element to compensate for impedance changes in the oscillator, and a compensation that is stored in advance in memory based on information obtained from a separately provided temperature-sensing crystal oscillator There is a digital method in which a voltage for compensating the temperature characteristic of a crystal oscillator for oscillation is applied to a variable capacitance element according to data.

A conventional temperature-compensated crystal oscillator will be described below with reference to the drawings. FIG. 19 shows the configuration of a conventional analog temperature-compensated crystal oscillator. In FIG. 19, 11 is a crystal oscillator, 12 is an oscillation circuit, 13 is an output terminal, and 111 is a temperature compensation circuit. The temperature compensation circuit 111 includes a thermistor 112 and a resistor 11.
3 is connected in parallel with the capacitor 114, and the thermistor 115 and the resistor 116 are connected in series.
A circuit section in which 7 are connected in parallel is included. When the ambient temperature changes, the resistance values of the thermistors 112 and 115 change, and as a result, the reactance of the impedance of the entire temperature compensation circuit 111 changes. By utilizing this, the values of the thermistors 112 and 115, the resistors 113 and 116, and the capacitors 114 and 117 are determined in advance so as to compensate the frequency-temperature characteristics of the crystal unit, thereby stabilizing the oscillation frequency against temperature. (See, for example, JP-A-55-125702 and JP-A-56-68002).

On the other hand, FIG. 20 shows the configuration of a conventional digital temperature-compensated crystal oscillator. 20, 11 is a crystal oscillator, 12 is an oscillation circuit, 121 is a temperature sensor, 122 is an analog / digital (A / D) converter, 123 is a storage device, and 124 is a variable reactance circuit. Further, the crystal oscillator 11, the oscillation circuit 12, and the variable reactance circuit 124 constitute a digitally controlled crystal oscillator 120 whose oscillation frequency is controlled by a digital signal. In the digital temperature compensation, the ambient temperature is detected by the temperature sensor 121 and the information is detected by the A / D converter 1.
At 22, the digital signal is converted into a digital signal, and based on the digital signal, the compensation data stored in advance in the storage device 123 is read. Then, according to the compensation data, the variable reactance circuit 12
The reactance value of 4 is changed to stabilize the output frequency of the digitally controlled crystal oscillator 120 against temperature. Compensation data is written in the storage device 123, for example, as a table of 8 bits (256 temperature points) × 7 bits (128 control amounts) (eg, 41st Annual).
Frequency Control Symposium, 1987, pp.435, 'A Digi
tally Compensated TCXO using A Single Chip LSI: by
T.Hara, T.Kudo, S.Uriya, H.Saita, S.Ogou and Y.Kat
suta.)

[0007]

However, the above-mentioned analog-type and digital-type temperature-compensated crystal oscillators have their own problems as described below.

First, in the analog method using a thermistor, since the shape of the compensation curve that can be realized is limited, it is not possible to flexibly cope with variations in the resonance frequency-temperature characteristics of the crystal unit, and the temperature compensation accuracy is low. There was a problem. Further, since the thermistor has a large variation in characteristics, the yield is reduced. Therefore, it is necessary to strictly control the variation of the resonance frequency-temperature characteristic of the crystal unit and the circuit element, and the adjustment work becomes complicated, resulting in a high cost. Further, since the thermistor and the like are elements that are not suitable for IC, there is a problem that it is difficult to reduce the size.

On the other hand, in the digital temperature-compensated crystal oscillator, since the frequency is corrected at each temperature point, the compensation data is programmable read-only for a large number of temperature points such as 256 points. Must be written to memory (PROM). Therefore, there is a problem that a great deal of time and labor is required for manufacturing, and as a result, the price is high.

In consideration of such problems of the conventional temperature compensating circuit, the present invention is suitable for use in a mobile phone or the like, in which the temperature compensation adjustment can be easily performed, and the size is small, the price is low and the accuracy is high. An object is to provide a temperature-compensated crystal oscillator.

[0011]

The present invention comprises an oscillating means using a crystal oscillator, the oscillating frequency of which can be adjusted, a temperature detecting means, and a control signal generating means, the control signal generating means comprising: A control signal generated from a characteristic obtained by linearly approximating a plurality of divided temperature sections with respect to an ideal control curve for ideally temperature-compensating the oscillation frequency is generated based on the output of the temperature detecting means, and the control signal is generated. Is a temperature-compensated crystal oscillator in which the oscillation frequency of the oscillation means is controlled to perform temperature compensation.

More specifically, in the predetermined input voltage range corresponding to the two continuous temperature sections, the control signal generating means has an output voltage from zero to a predetermined maximum value according to the input voltage in the first half temperature section. It has a reverse V-shaped input / output characteristic in which it monotonically increases and then monotonically decreases again to zero according to the input voltage in the latter half of the temperature range, and the output voltage becomes zero in the other input voltage range (N + 1).
Each of the voltage function generating circuits has a plurality of (N is an integer of 2 or more representing the number of the temperature sections) voltage function generating circuits and a voltage adder for adding all output voltages of the voltage function generating circuits. The output voltage change relationship is expressed as follows: (i-1) th voltage function when the output voltage of the i-th (i is an integer of 2 or more and N or less) output voltage increases from zero to a maximum value. The output voltage of the generation circuit decreases from the maximum value to zero, and when the output voltage of the i-th voltage function generation circuit decreases from the maximum value to zero, the (i + 1) th voltage function generation circuit. The output voltage of is increased from zero to the maximum value.

[0013]

According to the present invention, since the control signal very close to the ideal control curve can be easily generated by adding the output voltages of the plurality of voltage function generating circuits having a simple structure, the whole circuit structure can be realized. The temperature can be easily and accurately compensated.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a block diagram of a temperature-compensated crystal oscillator according to the first embodiment of the present invention. The temperature-compensated crystal oscillator includes a temperature sensor 101 for detecting temperature, voltage function generation circuits 102, 103, 104, 105, 106, a voltage adder 107 for adding and outputting voltages, and a crystal oscillator 11 for oscillating frequency. Is composed of a stabilized oscillation circuit 12. The oscillation circuit 12 has an output terminal 13 that outputs an oscillation voltage and a control terminal 15 that controls an oscillation frequency.
The control terminal 15 is connected to the variable capacitance diode 14 whose capacitance changes according to the applied voltage.

The temperature sensor 101 generates a voltage proportional to temperature, and the voltage is five voltage function generating circuits 102, 1.
It is input to 03, 104, 105, 106. Each voltage function generating circuit has an inverse V-shaped input / output characteristic in which the output voltage monotonically increases and then monotonically decreases in a preset input voltage range as the input voltage increases. . The output voltage of the voltage function generating circuit is the voltage adder 10
It is input to 7 and all are added. The output terminal of the voltage adder is connected to the control terminal 15 of the oscillation circuit 12 and controls the oscillation frequency so as to stabilize the temperature.

The temperature sensor 101 is, for example, as shown in FIG.
As shown in FIG. 5, a circuit in which a resistor 22 is connected in series to a plurality of diodes 23 connected in series is used. By utilizing the change in the junction potential difference of the diode with respect to the temperature change, when a DC voltage is applied to the terminal 21, the voltage change corresponding to the temperature change can be taken out with the connecting point 24 of the diode and the resistor as the output terminal. it can. Alternatively, FIG.
As shown in (b), a circuit in which a thermistor 25 and a resistor 22 are connected in series can be configured to utilize a change in resistance value with respect to a temperature change. In FIG. 2B as well, similarly to FIG. 2A, by applying a DC voltage to the terminal 21, a voltage change corresponding to a temperature change can be extracted at the output terminal 24.

The operation principle of the first embodiment will be described with reference to the drawings. First, regarding the relationship between the temperature of the temperature sensor 101 and the output voltage, it is assumed that the output voltage Vs changes substantially linearly with respect to the temperature T, as shown in FIG. Here, when the temperature T is T ₁ , T ₂ , T ₃ , T ₄ , T ₅ , and T ₆ , the output voltage V _s of the temperature sensor 101 is V respectively.
Let _s1 , V _s2 , V _s3 , V _s4 , V _s5 , and V _s6 .

FIG. 4 shows an ideal control curve (broken line) for ideally temperature compensating the temperature-compensated crystal oscillator, and a control curve (solid line) in the embodiment of the present invention in which the control curve is linearly approximated for each divided temperature section. Indicates. When the ambient temperature T changes, the control voltage V _c applied to the control terminal 15 in order to keep the oscillation frequency constant is linearly approximated to the ideal control voltage curve in five divided temperature intervals. It is composed of straight lines.

The great feature of the temperature compensation method of the present invention is that, unlike the conventional method, the curve showing the relationship between the temperature and the oscillation frequency is not approximated by a straight line. The optimum linear approximation is performed on such a control curve, and the meaning of the linear approximation is completely different between the two.

FIG. 5 shows five voltage function generating circuits 10 for realizing the characteristics of the approximate straight line shown by the solid line in FIG.
2, 103, 104, 105 and 106 are temperature sensors 10
1 shows a state of the output voltage V _c to be output with respect to the input voltage V _s from 1. Five voltage function generation circuits 10
The input voltage ranges in which 2, 103, 104, 105 and 106 output the inverted V-shaped output voltage respectively correspond to two continuous temperature sections of each of the divided temperature sections except the voltage function generating circuit 102. Have been assigned. The voltage function generating circuit 102 is set to output the output voltage V _c corresponding to only one temperature section.

As shown in FIG. 5, the voltage function generating circuit 10
2 is from V _s1 to V _s2 , and the voltage function generating circuit 103 is V _s1
From V _s3 to V _s3 , the voltage function generating circuit 104 uses V _s2 to V _s4
Up to V _s3 to V _s5 , and the voltage function generation circuit 106 operates from V _s4 to V _s6 . The output voltage of each voltage function generation circuit is zero in the other input voltage range.

The voltage function generation circuit 102 has a maximum value V _c5 at V _s1 , the voltage function generation circuit 103 has a maximum value V _c4 at V _s2 , and the voltage function generation circuit 104 has a maximum value V _c3 at V _s3. The circuit 105 has a maximum value V _c2 at V _s4 , and the voltage function generating circuit 106 has a maximum value V _c1 at V _s5 . For example, the voltage function generating circuit 104, until the input voltage V _s2 is the output voltage is zero, according to the input voltage increases from V _s2, the output voltage increases monotonically, the input voltage V
_The output voltage reaches the maximum value V _c3 at _s3 , and thereafter, as the input voltage increases to V _s4 , the output voltage monotonously decreases, and when the input voltage increases from V _s4 , the output voltage becomes zero.

Next, the voltage function generating circuits 102, 103, 104, 105, 106 having the above input / output characteristics.
When the output voltage of the temperature sensor 101 is added by the voltage adder 107, the control having the characteristic approximated by a straight line for each of the five divided temperature sections as shown by the solid line in FIG. 4 corresponding to the input voltage from the temperature sensor 101. The voltage V _c is obtained.

According to the above configuration, in FIG. 1, FIG. 4 and FIG. 5, for example, the maximum value V _c4 of the output voltage of the voltage function generating circuit 103 is changed at the temperature T ₂ to adjust it to the required control voltage value. In this case, at the temperature T ₂ , voltage function generating circuits 102, 104, 105, 106 other than the voltage function generating circuit 103 are used.
Since the output voltages of all are zero, the voltage function generation circuit 102
It is only necessary to adjust the temperature compensation, and temperature compensation adjustment is easy. vice versa,
Since the output voltage of the voltage function generating circuit 102 is all zero in the temperature range other than T ₁ to T ₃ , the change in the maximum value V _c4 of the output voltage can be adjusted at other temperatures T ₁ , T ₃ , T ₄ , and T ₅ . It has no effect. That is, the maximum value of the output voltage of the voltage function generating circuit may be adjusted only in the temperature range to which the voltage function generating circuit is assigned, and there is no mutual interference. Further, since the ideal control voltage is approximated by a straight line, temperature compensation may be performed by adjusting only a few temperature points, and a temperature-compensated temperature-compensated crystal oscillator can be easily realized.

A specific circuit in which the temperature-compensated crystal oscillator according to the first embodiment of the present invention is constructed by using an operational amplifier will be described below. 6 and 7 are specific circuit diagrams in which the temperature-compensated crystal oscillator according to the first embodiment of the present invention is configured using an operational amplifier.

First, the crystal oscillator has a frequency of 12.8 MHz.
UM-1 type, which is AT-cut. The oscillator circuit is a Colpitts type oscillator circuit using a silicon bipolar transistor. The oscillation frequency can be changed by changing the voltage applied to the variable capacitance diode, and the oscillation frequency is increased by increasing the positive voltage applied.

The temperature sensor is of a type using the diode shown in FIG. 2 (a), and has three diodes connected in series. By connecting three diodes in series, the slope of the relationship between the temperature of the temperature sensor and the output voltage can be made large, and the characteristics suitable for the temperature sensor of the temperature-compensated crystal oscillator can be obtained. FIG. 8 shows FIG.
9 is a graph showing the relationship between the temperature of a temperature sensor using a diode used in the circuit of FIG. The output voltage of the temperature sensor has a characteristic that it changes linearly with temperature.

FIG. 9 is a graph showing the relationship between temperature and control voltage in the temperature-compensated crystal oscillator of the circuits of FIGS. In the figure, the curve connecting the white circles (○) is an ideal temperature compensation control curve that sets the frequency deviation of the oscillator to 0 ppm. The curves connecting the black squares (■) and the black triangles (▲) that sandwich the curve above and below are control curves when the frequency deviation is +1 ppm or -1 ppm, respectively. The outermost curves connecting the white squares (□) and the white triangles (△) show the control curves when the frequency deviation is + 2ppm or -2ppm, respectively.

The control curve when the number of divisions of the temperature section is set to 5 sections is shown by a thick polygonal line. The temperatures at the division points of the temperature section are -32 ° C, -17 ° C, 0 ° C, 47 ° C, 67.
℃, 80 ℃. The control voltage corresponding to the temperature is 1422mV, 1167mV, 1014mV, 1005mV, 819m, respectively.
V is 556 mV. Regarding the method of selecting the temperature section and the method of setting the control curve, the control characteristic is selected so that the maximum value of the frequency deviation due to the deviation from the ideal control curve is minimized in the entire temperature section. As a result, the linearly approximated control curve is sandwiched between the control curves of ± 1 ppm, and it can be understood that temperature compensation can be performed with a frequency deviation of ± 1 ppm or less.

Here, the control characteristic is selected so that the deviation in the entire temperature section is minimized, but as another method, the ideal control curve is matched so that the frequency deviation is zero at both ends of each temperature section. Can also be considered. With this method, the frequency deviation is somewhat large, but the method of setting the control curve is simple and the adjustment is even easier.

FIG. 10 is a graph showing the relationship between the input voltage and the output voltage of the control signal generating means in the temperature-compensated crystal oscillator of the circuits of FIGS.

In the circuits of FIGS. 6 and 7, a voltage function generating circuit having an inverse V-shaped input / output characteristic in a predetermined input voltage range corresponding to two continuous temperature sections is provided with a predetermined voltage corresponding to one temperature section. It is configured by a combination of single-section voltage function generating circuits having linear input / output characteristics in the input voltage range. Then, the output voltage that changes from zero to the maximum value corresponding to the temperature section in the first half of the i-th voltage function generating circuit changes from zero to the maximum value according to the input voltage in the predetermined input voltage range corresponding to the temperature section. The output voltage is generated by the single-section voltage function generating circuit using the operational amplifier, and the output voltage of the single-section voltage function generating circuit is inverted to make the temperature section in the latter half of the (i-1) th voltage function generating circuit. It is also used as the output voltage that changes from the corresponding maximum value to zero.

Further, the first voltage function generating circuit is a single section using an operational amplifier for generating an output voltage which changes from the maximum value to zero according to the input voltage in a predetermined input voltage range corresponding to the first temperature section. It is composed of a voltage function generating circuit. Alternatively, although not used in the circuits of FIGS. 6 and 7, the (N + 1) th (N
Is a temperature division number), and a single-section voltage function using an operational amplifier that generates an output voltage that changes from zero to a maximum value according to the input voltage in a predetermined input voltage range corresponding to the Nth temperature section. It is also possible to use a method of configuring with a generating circuit. By taking these methods, the circuit is somewhat simpler.

Further, in the circuits of FIGS. 6 and 7, the maximum values of the output voltages of the respective voltage function generating circuits are all set equal to each other,
A desired control signal is generated by adjusting the amplification degree of the operational amplifier inserted between the voltage function generating circuit and the voltage adder. Also, the maximum value of the output voltage is specified by utilizing the output voltage saturation characteristic of the operational amplifier. With such a method, a desired control signal waveform can be obtained with a simple circuit configuration.

FIG. 11 is a graph showing the frequency shift with respect to temperature in the temperature-compensated crystal oscillator of the circuits of FIGS. ± 1ppm in the temperature range of -30 ℃ to + 75 ℃
The following characteristics are obtained. In the first embodiment, the ideal control voltage curve is divided into five temperature sections and linear approximation is performed. Generally, the greater the number of divisions, the better the accuracy, and conversely, the smaller the number of divisions, the simpler the circuit configuration. become.

When the number of divisions of the temperature section is 5, for example, the FDMA system large-capacity analog cellular with a channel frequency interval of 12.5 kHz or less which requires performance of ± 1 ppm or less in the range of -20 ° C to + 85 ° C. Ideal for wireless terminals. When the number of divisions of the temperature section is 4, for example, a narrow band TDMA digital cellular radio terminal with a channel frequency interval of about 25 kHz which requires performance of ± 1.5 ppm or less in the range of -20 ° C to + 85 ° C. Is perfect for Further, when the number of divisions of the temperature section is 3, for example, in the range of −30 ° C. to + 75 ° C., an F frequency of 30 kHz or more that requires a performance of ± 2.5 ppm or less is required.
It is suitable for a DMA type analog cellular radio terminal, a wide band TDMA type digital cellular radio terminal having a wide channel frequency interval, and a digital cordless telephone.

FIG. 12 is a graph showing the relationship between temperature and control voltage when the number of divided temperature sections in the temperature-compensated crystal oscillator of the first modification of the first embodiment of the present invention is four. is there. From the figure, the frequency shift with respect to temperature is -3.
It can be seen that the temperature can be reduced to ± 1.5 ppm or less in the range of 0 ° C to + 75 ° C.

Further, FIG. 13 shows the relationship between the temperature and the control voltage when the number of divided temperature sections in the temperature-compensated crystal oscillator according to the second modification of the first embodiment of the present invention is three. It is a graph. From the figure, it can be seen that the frequency deviation with respect to temperature can be kept within ± 2.5 ppm in the range of -30 ° C to + 75 ° C.

That is, by determining the number of divisions of the temperature section in accordance with the target temperature range and frequency stability, the present invention enables the optimum circuit configuration for each application.

As described above, with the configuration of this embodiment, temperature compensation can be easily performed, and a compact, low-priced, highly accurate temperature-compensated crystal oscillator can be realized. Therefore,
FDMA analog cellular radio terminal, narrow band TDM
An optimum temperature-compensated crystal oscillator can be provided for each of the A-system digital cellular radio terminal, the wideband TDMA-type digital cellular radio terminal, and the digital cordless telephone.

The second embodiment of the present invention will be described below with reference to the drawings. FIG. 14 is a configuration block diagram of a temperature-compensated crystal oscillator according to the second embodiment of the present invention.
The temperature-compensated crystal oscillator according to the second embodiment includes a temperature sensor 31 for detecting temperature, an A / D converter 32, and an arithmetic unit 3.
3 and programmable read only memory (P
ROM) 34, a D / A converter 35, and an oscillator circuit 12 whose oscillation frequency is stabilized by a crystal oscillator 11. The oscillation circuit 12 has an output terminal 13 that outputs an oscillation voltage and a control terminal 15 that controls an oscillation frequency.
The control terminal 15 is connected to the variable capacitance diode 14 whose capacitance changes according to the applied voltage. This oscillator circuit section is the same as that of the first embodiment.

The present embodiment differs from the first embodiment in that the control signal generating means is realized by digital arithmetic processing. The temperature sensor 31 generates a voltage proportional to temperature and is input to the A / D converter 32. The temperature information is converted into a digital signal and input to the calculator 33. On the other hand, the temperature T _{i of the} division point that divides the temperature section
(I is an integer greater than or equal to 1 and less than or equal to N, N is the number of divisions of the temperature section),
The value of the control voltage value V _{oi at} the temperature T _i is PR
Written in OM. These values are also input to the calculator 33, and the digital value of the control voltage V at the temperature T is calculated according to the following equation.

[0044]

[Equation 1]

The digital value of the control voltage V is input to the D / A converter 35 and converted into an analog output voltage. The output voltage of the D / A converter 35 is connected to the control terminal 15 of the oscillation circuit and controls the oscillation frequency so as to stabilize the temperature.

As described above, in the present embodiment, by realizing the control signal generating means by the digital arithmetic processing, it is possible to have a structure suitable for an IC and downsize. Further, since the temperature at the division point and the control voltage value at that temperature need only be written in the PROM, it can be set relatively freely, and the control characteristics can be flexibly selected.

The third embodiment of the present invention will be described below with reference to the drawings. FIG. 15 is a configuration block diagram of a temperature-compensated crystal oscillator according to the third embodiment of the present invention.
The present embodiment differs from the first embodiment in the configuration of the control voltage output means. The control voltage output means includes five voltage function generating circuits 203, 204, 205, 206, 207 and the voltage function generating circuits 203, 204, 205, 206, 20.
7 is configured by a switching circuit 202 that switches the output according to the output of the temperature sensor 201. Here, each voltage function generating circuit 203, 204, 205, 206, 20
_{Reference numeral} 7 denotes each range (V _s1 to V _s2 , V _s2 to V _s3 , V _s3 to V) of the input voltage from the temperature sensor 201 corresponding to each temperature.
_s4 , V _s4 to V _s5 , V _s5 to V _s6 ), the output voltage is adjusted so as to correspond to the control voltage shown by the solid line in FIG. 16, and the input voltage range other than that is adjusted. The output voltage is set to zero.

The operating principle of the third embodiment will be described below with reference to the drawings. First, the temperature sensor 20
1 is the characteristic shown in FIG. That is, the output voltage V _s changes substantially linearly with respect to the ambient temperature T, and the output voltage V _s when the temperature T is T ₁ , T ₂ , T ₃ , T ₄ , T ₅ , and T _6.
s is V _s1 , V _s2 , V _s3 , V _s4 , V _s5 , and V _s6 , respectively. Here, the relationship between the output voltage V _s of the temperature sensor 201 and the control voltage V _c for keeping the oscillation frequency constant is shown in FIG.
The same as the example shown in. The output of the temperature sensor 201 is the voltage function generating circuits 203, 204, 205, 20.
Switching circuit 202 for switching 6,207
The control line for switching of the switching circuit 202 is also input to the voltage function generating circuits 203, 20.
It is connected to 4, 205, 206, and 207.

FIG. 16 shows the switching circuit 202 and the voltage function generating circuits 203, 204, 205, 206 for the input voltage V _s from the temperature sensor 201, which is necessary to realize the characteristics shown by the solid line in FIG. 3 shows the operation characteristics of 207. The input voltage range in which the five voltage function generating circuits work is assigned to each by the switching circuit 202, and as shown in FIG.
The voltage function generation circuit 203 has V _s1 to V _s2 , the voltage function generation circuit 204 has V _s2 to V _s3 , the voltage function generation circuit 205 has V _s3 to V _s4 , and the voltage function generation circuit 206 has V _s4 to V _s5 . The generation circuit 207 is activated in the input voltage range of V _s5 to V _s6 , and is in the rest state in the other input voltage ranges. Further, the voltage function generating circuits 203, 204, 205, 206, 207 each have an input / output characteristic that the output voltage monotonously decreases with respect to the input voltage during operation. That is, the voltage function generation circuit 203 outputs the output voltages V _c5 to V _{c4 with} respect to the input voltages V _s1 to V _s2 , and the voltage function generation circuit 204 inputs the input voltage V
Output voltages V _c4 to V _c3 for _s2 to V _s3 , voltage function generating circuit 205 outputs voltages V _c3 to V _c2 for input voltages V _s3 to V _s4 , and voltage function generating circuit 206 inputs voltage V _s4
To V _s5 to output voltages V _c2 to V _c1 , and the voltage function generation circuit 207 outputs voltage V _s5 to V _s6 for output voltage V
Change from _c1 to zero.

The outputs of the voltage function generating circuits 203, 204, 205, 206, 207 having the above input / output characteristics are
By switching by the switching circuit 202 based on the output voltage of the temperature sensor 201, the control voltage Vc having the characteristic shown by the solid line in FIG. 4 with respect to the input voltage, that is, the ambient temperature can be obtained.

According to the above configuration, as in the first embodiment, in FIGS. 4, 15 and 16, for example, the maximum value V _c4 of the output voltage of the voltage function generation circuits 203 and 204 at the temperature T ₂ is obtained. When the temperature is changed to a required control voltage value, the output voltages of the voltage function generating circuits 205, 206, 207 other than the voltage function generating circuits 203, 204 are all zero at the temperature T ₂ , so that two voltage function generating circuits are used. 203,2
It is only necessary to adjust 04, and temperature compensation adjustment is easy. Further, since the ideal control voltage is approximated by a straight line, temperature compensation may be performed by adjusting only a few temperature points, and a temperature-compensated temperature-compensated crystal oscillator can be easily realized.

Further, by the switching circuit 202,
Voltage function generating circuits 203, 204, 205 to be operated,
Since 206 and 207 are switched, only one voltage function generating circuit operates at any one time, and the current consumption can be kept low.

The fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 17 is a configuration block diagram of the temperature-compensated crystal oscillator according to the fourth embodiment of the present invention.
This embodiment is different from the first embodiment in that the input / output characteristics of each voltage function generating circuit are different. The basic configuration is similar to that of the first embodiment. That is, the temperature sensor 301 includes voltage function generating circuits 302, 303, 30.
4, 305, 306 are connected to the voltage function generating circuits 302, 303, 304, 305, 306, and a voltage adder 307 is connected. Also, the voltage adder 307
Is connected to the control terminal 15 of the oscillation circuit 12 and the variable capacitance diode 14.

Next, the operating principle of the fourth embodiment will be described with reference to the drawings. First, the temperature sensor 30
1 is the characteristic shown in FIG. That is, the output voltage V _s changes substantially linearly with respect to the ambient temperature T, and the output voltage V _s when the temperature T is T ₁ , T ₂ , T ₃ , T ₄ , T ₅ , and T _6.
s is V _s1 , V _s2 , V _s3 , V _s4 , V _s5 , and V _s6 , respectively. Here, the relationship between the output voltage V _s of the temperature sensor 201 and the control voltage V _c for keeping the oscillation frequency constant is shown in FIG.
The same as the example shown in.

FIG. 18 shows the input voltage V from the temperature sensor 301 which is necessary to realize the characteristics shown by the solid line in FIG.
voltage function generation circuits 302, 303, 304 for _s ,
The operation characteristics of 305 and 306 are shown. The input / output characteristics of the five voltage function generation circuits are as follows:
02, when the input voltage is V _s1 or less, the output voltage is (V _c5 −
V _c4 ) is a constant value, and from V _s1 to V _s2 monotonically decreases from that constant value to zero, and remains at zero above V _s2 . Similarly, in the voltage function generation circuit 303, V _s2
In the following _cases (V _c4 −V _c3 ), from V _s2 to V _s3 , (V
It decreases monotonically from _c4 −V _c3 ) to zero, and is zero at _{Vs3 and} above. In the voltage function generation circuit 304, when V _s3 or less (V _c3
-V _c2 ), V _s3 to V _s4 monotonically decreases from (V _c3 -V _c2 ) to zero, and is zero at V _{s4 and} above. In the voltage function generation circuit 305, when V _s4 or less (V _c2 −V _c1 ), V _s4 to V _s5 monotonically decreases from (V _c2 −V _c1 ) to zero, and zero at V _s5 or more. In the voltage function generation circuit 306, V
_{When s5} or less, V _c1 and V _s5 to V _s6 decrease monotonically from V _c1 to zero, and above that, it is zero.

When the output voltages of the voltage function generating circuits 302, 303, 304, 305, 306 having the above input / output characteristics are added by the voltage adder 307, the input voltage from the temperature sensor 301, that is, the ambient temperature, As a result, the control voltage V _c having the characteristic shown by the solid line in FIG. 4 can be obtained.

According to the above configuration, in FIG. 4, FIG. 17, and FIG. 18, for example, when adjusting the slope of the output voltage of the voltage function generating circuit 303 in the temperature range from T ₂ to T ₃ , the voltage value Even if (V _c4 −V _c3 ) is changed to the required control voltage value, the voltage function generating circuits 302, 304, 304, other than the voltage function generating circuit 303 are in the temperature range of T ₂ to T ₃ .
Since the output voltages of 305 and 306 are all constant values, the slope of the output voltage can be adjusted only by the voltage function generating circuit 303, and temperature compensation adjustment is easy. When adjusting the temperature-frequency characteristics in the entire temperature range, the voltage function generating circuit 30
Adjustment is performed in the order of 6, 305, 304, 303, 302. Further, since the ideal control voltage is approximated by a straight line, temperature compensation may be performed by adjusting only a few temperature points, and a temperature-compensated temperature-compensated crystal oscillator can be easily realized. Further, the fourth embodiment has a feature that the circuit is simpler than that of the first embodiment.

In the above embodiment, the temperature sensor using a diode and the temperature sensor using a thermistor have been described as examples, but the present invention is not limited to this, and the output voltage may be changed in response to a temperature change. For example, a temperature sensor of another type such as a circuit that uses a transistor to convert a change in current due to a change in temperature into a voltage may be used. In this case, the relationship between the temperature change and the output voltage may not be a linear relationship, but may be a quadratic function, a cubic function, an exponential function, or the like. It should be matched to the characteristics of.

Further, instead of the operational amplifier used in the embodiments of the present invention, a circuit composed of transistors or the like can be used.

[0060]

As is apparent from the above description,
The present invention is, for example, 1p over a temperature range of about 100 ° C.
Compensation data for suppressing the frequency deviation from pm to 2 ppm or less is acquired at about 3 to 5 temperature points, and temperature compensation can be performed independently at each temperature point, so temperature compensation adjustment can be easily performed. .

Therefore, the cost can be reduced and the accuracy can be improved, and the configuration can be realized by only the elements suitable for the IC, and the miniaturization can be realized.

Further, it is possible to provide a small-sized, low-cost temperature-compensated crystal oscillator, which is suitable for a cellular radio mobile phone or a cordless phone.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a temperature-compensated crystal oscillator according to a first embodiment of the present invention.

FIG. 2A is a circuit diagram showing a temperature sensor using a diode in a temperature-compensated crystal oscillator according to an embodiment of the present invention. (B) is a circuit diagram showing a temperature sensor using a thermistor in the temperature-compensated crystal oscillator of the embodiment of the present invention.

FIG. 3 is a diagram for explaining the relationship between the temperature and the output voltage in the temperature sensor according to the embodiment of the present invention.

FIG. 4 is an example of an ideal control curve (broken line) for ideally temperature compensating a temperature-compensated crystal oscillator and a control curve (solid line) in the embodiment of the present invention in which the control curve is linearly approximated for each divided temperature section. FIG.

FIG. 5 is a diagram showing input / output characteristics of the voltage function generating circuit according to the first embodiment of the present invention.

FIG. 6 is an upper half of a specific circuit diagram in which the temperature-compensated crystal oscillator according to the first embodiment of the present invention is configured by using an operational amplifier.

FIG. 7 is a lower half of a specific circuit diagram in which the temperature-compensated crystal oscillator according to the first embodiment of the present invention is configured using an operational amplifier.

FIG. 8 is a graph showing the relationship between the temperature, the output voltage, and the current consumption of the temperature sensor using the diode used in the circuits of FIGS.

9 is a graph showing the relationship between temperature and control voltage when the number of divided temperature sections in the temperature-compensated crystal oscillator of the circuits of FIGS. 6 and 7 is five.

10 is a graph showing the relationship between the input voltage and the output voltage of the control signal generating means in the temperature-compensated crystal oscillator of the circuits of FIGS.

FIG. 11 is a graph showing frequency shift with respect to temperature in the temperature-compensated crystal oscillator of the circuits of FIGS.

FIG. 12 is a graph showing the relationship between temperature and control voltage when the number of divided temperature sections in the temperature-compensated crystal oscillator according to the first modification of the first embodiment of the present invention is four.

FIG. 13 is a graph showing the relationship between temperature and control voltage when the number of divided temperature sections in the temperature-compensated crystal oscillator according to the second modification of the first embodiment of the present invention is three.

FIG. 14 is a configuration block diagram of a temperature-compensated crystal oscillator according to a second embodiment of the present invention.

FIG. 15 is a configuration block diagram of a temperature-compensated crystal oscillator according to a third embodiment of the present invention.

FIG. 16 is a diagram showing input / output characteristics of the voltage function generation circuit and operation characteristics of the switching means in the third embodiment.

FIG. 17 is a configuration block diagram of a temperature-compensated crystal oscillator according to a fourth embodiment of the present invention.

FIG. 18 is a diagram showing input / output characteristics of a voltage function generating circuit according to a fourth embodiment of the present invention.

FIG. 19 is a configuration block diagram of a conventional analog temperature-compensated crystal oscillator.

FIG. 20 is a configuration block diagram of a conventional digital temperature-compensated crystal oscillator.

[Explanation of symbols]

11 Crystal Resonator 12 Oscillation Circuit 13 Output Terminal 14 Variable Capacitance Diode 15 Control Terminal 101 Temperature Sensor 102, 103, 104, 105, 106 Voltage Function Generation Circuit 107 Voltage Adder

Claims (15)

[Claims] 1. An oscillating means using a crystal oscillator, the oscillating frequency of which can be adjusted, a temperature detecting means, and a control signal generating means, wherein the control signal generating means ideally controls the oscillating frequency to a temperature. A control signal obtained from a characteristic that is linearly approximated for each of a plurality of divided temperature sections with respect to an ideal control curve to be compensated is generated based on the output of the temperature detecting means, and the oscillation frequency of the oscillating means is generated by the control signal. A temperature-compensated crystal oscillator in which temperature compensation is performed by controlling the temperature. 2. The control characteristic according to the control signal is selected so that the maximum value of the frequency deviation due to the deviation from the ideal control curve is minimized in the entire temperature section. Temperature compensated crystal oscillator. 3. The temperature compensation according to claim 1, wherein the control characteristic of the control signal is selected so as to match the ideal control curve at both ends of each temperature section so that the frequency deviation becomes zero. Crystal oscillator. 4. The temperature-compensated crystal oscillator according to claim 1, wherein the number of divided temperature sections is five. 5. The temperature-compensated crystal oscillator according to claim 1, wherein the number of divided temperature sections is four. 6. The temperature-compensated crystal oscillator according to claim 1, wherein the number of divided temperature sections is three. 7. The temperature detecting means applies a DC voltage to a circuit in which a plurality of series-connected diodes and resistors are connected in series, and uses a connection point between the diodes and the resistors as an output terminal. A temperature-compensated crystal oscillator according to claim 1. 8. The switching means for switching the control signal generating means by selecting a plurality of voltage function generating circuits that monotonically change the output voltage according to an input voltage and the voltage function generating circuit that operates in each of the temperature intervals. The temperature-compensated crystal oscillator according to claim 1, further comprising: 9. The control signal generating means changes an output voltage from a predetermined first voltage value to a predetermined second voltage value in accordance with an input voltage in a predetermined input voltage range corresponding to the specific temperature section.
A plurality of voltage function generating circuits having an input / output characteristic that monotonically changes to a voltage value of, and holds an output voltage at each of the predetermined voltage values in an input voltage range corresponding to other temperature sections, and the voltage function. The temperature-compensated crystal oscillator according to claim 1, further comprising a voltage adder for adding all output voltages of the generation circuit. 10. The control signal generating means comprises two consecutive
In the predetermined input voltage range corresponding to the two temperature sections, the output voltage monotonically increases from zero to a predetermined maximum value according to the input voltage in the first half temperature section, and then again from the maximum value to zero according to the input voltage in the second half temperature section. (N + 1) (N is an integer greater than or equal to 2 representing the number of the temperature intervals) voltage-function generating circuits having input / output characteristics such that the output voltage decreases monotonically until the output voltage becomes zero in the other input voltage range. A voltage adder that adds all the output voltages of the voltage function generating circuit, and the relationship of the output voltage change of each of the voltage function generating circuits is the i-th (i is an integer of 2 or more and N or less) of the voltage function. When the output voltage of the generating circuit increases from zero and reaches the maximum value, the output voltage of the (i-1) th voltage function generating circuit decreases from the maximum value to zero, and the i-th voltage function The output voltage of the (i + 1) th voltage function generating circuit is increased from zero to a maximum value when the output voltage of the raw circuit decreases from the maximum value to zero. The temperature-compensated crystal oscillator according to 1. 11. An output voltage that changes from zero to a maximum value corresponding to the first half temperature section of the i-th voltage function generating circuit is changed from zero to maximum according to the input voltage in a predetermined input voltage range corresponding to the temperature section. An output voltage that changes to a value is generated by a single-section voltage function generation circuit using an operational amplifier, and the output voltage of the single-section voltage function generation circuit is inverted to generate the (i-1) th voltage function generation circuit. 2. The output voltage is also used as an output voltage changing from a maximum value corresponding to a temperature section in the latter half of the above to zero.
The temperature-compensated crystal oscillator according to 0. 12. The first voltage function generating circuit is set to 1
A single-interval voltage function generating circuit using an operational amplifier that generates an output voltage that changes from a maximum value to zero in accordance with an input voltage in a predetermined input voltage range corresponding to the th temperature section. 10. The temperature-compensated crystal oscillator according to 10. 13. An operational amplifier for generating the (N + 1) th voltage function generating circuit for generating an output voltage which changes from zero to a maximum value according to the input voltage in a predetermined input voltage range corresponding to the Nth temperature section. 3. The single-section voltage function generating circuit used is constructed.
The temperature-compensated crystal oscillator according to 0. 14. The maximum value of the output voltage of each of the voltage function generating circuits is set to be equal to each other, and the amplification degree of an operational amplifier inserted between the voltage function generating circuit and the voltage adder is adjusted. 11. The temperature-compensated crystal oscillator according to claim 10, wherein the desired control signal is generated by: 15. The voltage function generating circuit is composed of an operational amplifier, and the maximum value of the output voltage is defined by utilizing the output voltage saturation characteristic of the operational amplifier.
4. The temperature-compensated crystal oscillator according to 4.