JPS59207707A - Temperature compensating circuit of tcxo - Google Patents

Abstract

PURPOSE:To obtain a temperature compensating circuit of TCXO for which circuit constant is determined to maintain a fixed value regardless of the change of voltage by impressing voltage to a set of confronting other node from a power source through necessary resistance and supplying to VCXO. CONSTITUTION:Nodes 3 and 4 are connected to a node 5 through resistances R9 and R10 respectively, and the voltage is impressed to the nodes 3 and 4 from the node 5 by the second power source E2, and the potential difference generated between the two nodes is supplied to a voltage controlled crystal oscillator VCXO as output voltage. In a temperature compensating circuit constituted as such, the oscillation frequency at reference temperature is made not to change even when the voltage impressed to the VCXO is adjusted, to enable to adjust the oscillation frequency at optional temperature to become equal to that at reference temperature without calculating a circuit contant. That is, the circuit constant is so set that the potential difference between nodes 3 and 4 does not depend on E2.

Description

[Detailed Description of the Invention] The present invention is a temperature compensated crystal oscillator (hereinafter referred to as TCXO).
This paper relates to improvements in temperature compensation circuits.

As is well known, the temperature compensation circuit of a TCXO combines a resistor including a temperature sensing element with a temperature-resistance coefficient such as a thermistor to cancel the temperature-frequency characteristics of the crystal resonator to which temperature compensation is to be performed, and uses direct current supplied from a constant voltage power supply. Crystal oscillation is performed by applying a total divided voltage to the variable capacitance diode of a voltage controlled crystal oscillator (hereinafter referred to as VCXO). However, the temperature-frequency characteristics of the crystal sensor used in the TCXO are generally shown by a cubic curve. In addition, since the temperature characteristics of the circuit elements are involved, calculating the constants of the temperature compensation circuit not only requires an extremely large amount of man-hours, but also requires additional calculation of the circuit constants in order to write out all compensation results sufficient for variations in the characteristics of individual crystal oscillators. The drawback was that it required repeated measurements for calculation and confirmation, which was extremely time-consuming.

The present invention was devised in order to eliminate the defects of the conventional 1' CXO temperature compensation circuit as described above, and in principle, it is equivalently expressed by a basic bridge circuit, and a pair of opposing pairs thereof are equivalently expressed by a basic bridge circuit. A reference voltage is applied between the nodes, and a resistor including the input terminal resistance of the crystal oscillator circuit is inserted between the opposite pairs of nodes to reduce the potential difference generated between the other pairs of nodes. In the conventional temperature compensation circuit that supplies the output voltage to the VCXO, a voltage is applied from the second power supply to each of the pairs of opposing nodes through a predetermined resistance, and the voltage is applied to the set of opposite nodes at a desired reference temperature. It is an object of the present invention to provide a temperature compensation circuit for a TCXO in which circuit constants are determined so that the voltage applied to the set of other opposing nodes is maintained at a constant value regardless of changes in the second power supply voltage. do.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

First, in order to facilitate understanding of the present invention, a general equivalent circuit of a conventional TCXO temperature compensation circuit is shown in FIG.

In this figure, at least - of the resistors R11 to R.5 constituting the basic bridge circuit must include the equivalent resistance component of the temperature sensing element, but if multiple or all of the resistors have temperature dependence. Even if it is, there is no problem in principle.

In addition, the resistance R.5 between node 3 and node 4 is an equivalent resistance that includes a resistance component of the frequency variable human power terminal of the VCXO such as a variable capacitance diode, and if the input terminal has a resistance between it and the ground. For example, it is possible to consider it as being included in R, 2 and R.4.

Therefore, the reference voltage E1 connected to node 1 causes node 3 to
The potential difference generated between and node 4 is set as the output voltage vcx
The purpose is to fully compensate the temperature-frequency characteristics of the crystal resonator and keep its oscillation frequency constant with respect to temperature.

The temperature compensation circuit of an actual TCXO generally has a configuration as shown in FIG. 2, but the temperature compensation circuit 2 for the VCXO 1 is a special case of the basic equivalent circuit shown in FIG. It can be thought of as being grounded. In this case, the resistance component of the thermistor R〒 and the fixed resistance R・6.
The combined resistance of R.7 corresponds to R.3 in Figure 1, and VC
It will be understood that the resistance components of the high frequency blocking resistor R.8 and the variable capacitance diode D, which are the input terminal resistances of the XO, can be considered to be included in Rs in FIG.

As mentioned above, in the conventional temperature compensation circuit having such a configuration, setting each constant of the circuit by calculation is extremely time-consuming and extremely difficult to adjust, as is clear from this figure.

In order to solve this problem, the present invention adopts the following circuit configuration.

FIG. 3 is an equivalent circuit showing the basic configuration of the temperature compensation circuit according to the present invention.

That is, nodes 3 and 4 of the conventional circuit shown in FIG. 1 are connected to a fifth node through resistors R. A voltage is applied to node 4, and the potential difference generated between these two cylinders is set as the output voltage vcx.

It is intended to supply

In the temperature compensation circuit of the present invention configured as described above, in order to be able to adjust the oscillation frequency at any temperature to be equal to that at a certain reference temperature without calculating circuit constants, it is necessary to adjust the oscillation frequency at a certain reference temperature. The oscillation frequency at temperature is vc
It is necessary to ensure that the voltage does not change even when the voltage supplied to xo is adjusted. That is, it is not necessary to set the circuit constants so that the potential difference between the nodes 3 and 4 does not depend on E2.

To find this condition, use the principle of superposition in linear circuit networks to transform the circuit in Figure 3 as shown in Figure 4, and find the conditions under which the potential difference between node 3 and node 4 is zero. .

Since Fig. 4 can be rewritten as shown in Fig. 5 using the net-star connection conversion, the condition for making the potential difference between nodes 3 and 4 in Fig. 3 zero is 1 in Fig. 5. Since it is sufficient that the voltage division ratio of the ground voltage at node 3 and node 4 at node 6 is equal, H,t R,4/R,9(1,?,t + R,4)=
R,2R3/R,t o (11,2-4-R,s)
It turns out that it is sufficient to satisfy (1).

7- It should be noted that the above-mentioned equation (1) does not involve the resistor R5, which isometrically includes the input terminal resistance component of the vcxo described above. This means that no matter what the equivalent resistance R.5 is, for example, it may be something like a temperature sensing element whose resistance value changes depending on the temperature, so it is important to consider the circuit design. This is extremely convenient.

Now, the basic equivalent circuit of the present invention shown in FIG. 3 can be modified as follows.

Mountain: Open R.5.

B) In the basic bridge circuit shown in FIG. 3, one or both of the equivalent resistances inserted into the pair of opposing branches are made infinite.

The conditions for eliminating the dependence of the potential difference between node 3 and node 4 of the basic bridge circuit on the second power supply voltage E2 in each of the above cases are shown in the table below.

8- Same, either one or a combination of the above conditions (I) and wholesale is possible.

Figure 6 shows that when the circuit constants are set to satisfy equation (4) in the case of R・3 → (equity) and R・4 → ■ on the above deformed side, the above-mentioned node 3 is 10-1 shows an example of calculating how the potential difference generated between node 4 and node 4, that is, the voltage supplied to vcxo changes.

As is clear from this figure, at the reference temperature of 25°C, vcx
The voltage applied to o remains unchanged, and compensation characteristics having various slopes can be obtained at other temperatures. That is, the second power supply voltage E2 can be adjusted to match the shape corresponding to the temperature-frequency characteristics of the curve 6VCXO.

Similarly, a full voltage is applied to the nodes 3 and 4 from the third power source through appropriate resistors, and after rough adjustment is made by varying the second power source voltage, the third power source voltage is adjusted. It is also possible to make fine adjustments by changing .

Furthermore, if necessary, several stages of similar circuits may be added.

Incidentally, among the modified examples, the R.5f: opened and the R.3
The temperature compensation circuit in which R.4f and R.4f are set to infinity has already been disclosed by the present inventor in Patent Application No. 97240 of 1982, and therefore, this modification is excluded from the scope of the claims of the present invention. It is something that should be done.

Therefore, the present invention is nothing but a general extension of the invention related to the aforementioned patent application.

Now, no matter what value B.5 takes, clauses 3 and 4
The fact that the potential difference generated between them remains unchanged means that this n
5 is used as a frequency variable element, meaning all scales.

For example, by inserting a variable resistor in parallel with the variable capacitance diode D of the VCXO and applying a voltage between the two cylinders, the load capacitance of the crystal resonator can be varied, so that the oscillation frequency can also be varied. Therefore, it is extremely easy to adjust the oscillation frequency to a desired value at the reference temperature by varying R.5i. Oka, as a result of performing such an operation, it is possible to cause almost no fluctuation in the temperature-applied voltage characteristics of the present temperature compensation circuit.

Figure 7 is a diagram showing the results of a simulation conducted to completely prove this fact, and it can be seen that the temperature-applied voltage characteristics simply shift without changing in reality as R・5 changes. be understood.

By adopting this type of circuit configuration, the oscillation frequency adjustment function and temperature compensation function can be completely separated, which not only simplifies circuit design, but also allows for independent adjustment without changing the temperature compensation characteristics in actual products. This makes fine frequency adjustment extremely easy.

By the way, in order to obtain the second power source E2, a voltage divided by a potentiometer having a sufficiently low resistance compared to the branch resistance is generally applied to the fifth node. For example, embodiments of inventions related to patent applications by prior guest inventors are also configured in this manner.

However, such a configuration consumes a large amount of power, which is extremely inconvenient when applied to modern electronic devices that require energy conservation.

In order to solve this problem, as shown in FIG. 8, by inserting a variable resistor R/V in series between the node 5 and the second power source E2 and adjusting it, the nodes 3 and 4 can be connected to each other. What is necessary is to vary the voltage applied between them. It will be clear that this arrangement has no effect on the oscillation frequency at the reference temperature. This is extremely advantageous in terms of circuit configuration, since it means that it is not necessarily necessary to reduce the impedance by using a potentiometer or an active element with a low resistance value in order to obtain the second power supply voltage E2.

Finally, by further modifying the temperature compensation circuit according to the present invention, V
A means for providing partial compensation at temperatures far from the vicinity of the reference temperature of the CXO will be explained.

As mentioned above, the temperature-frequency characteristic of a crystal resonator is shown by a cubic curve and also has variations. Therefore, it is difficult to use the relatively simple compensation circuit described above over a wide temperature range. It is virtually impossible to fully compensate.

To solve this problem, basically, for example, the EzQ is varied at a point other than the reference temperature to cancel the first-order term of the frequency-temperature characteristic of the crystal oscillator, and further increase the frequency in the high temperature and/or low temperature region. In order to partially compensate for the deviation, the resistance of - or two or more branches in FIG.
It is sufficient to avoid significantly changing the conditions shown in . For this purpose, for example, the resistor inserted in at least one of the branches shown in FIG. 3 may be replaced with a temperature sensing element and a variable resistor connected in parallel or in series with the temperature sensing element.

FIG. 9 is an equivalent circuit showing an embodiment of a partial compensation circuit constructed based on the above-mentioned idea.

That is, this diagram shows R.3 and R.4 of the basic circuit in FIG.
In the case where is set to infinity, the node 3 and the node resistance R,io
It goes without saying that they should be chosen equally.

In the circuit configured as described above, when the resistor R.11 is varied at a temperature much lower than the reference temperature, the potential difference generated between the nodes 3 and 4 in the vicinity of the temperature changes. It can be changed within the range of On the other hand, if this circuit returns to the reference temperature while maintaining the changed state of R·11e,
It was confirmed that although the voltage at the reference temperature slightly changed compared to the initial value, the value was extremely small and did not pose a problem in practice. FIG. 10 is a diagram showing the results of simulating the above operation.

Same 1c! ;te-fLL, fi Wff:tl,i?
! It will be understood that a similar phenomenon occurs at higher temperatures than the reference temperature, such as 111i9Kyf.

As explained above, the temperature-dependent composite variable resistor in which the temperature sensing element and the variable resistor are connected in parallel or in series is the third
It can be easily deduced that they may be inserted into any branch of the basic circuit shown in the figure, and that it is not necessarily necessary to connect a plurality of sets in series to the same branch.

Since the present invention is configured and functions as explained above, the compensation characteristics can be extremely easily varied in response to the characteristics of the crystal resonator of the VCXO to which temperature compensation is to be performed in the TCXO, and variations in individual characteristics. This makes it possible to extend the compensation characteristics to a wide temperature range away from the vicinity of the reference temperature, thereby stabilizing the oscillation frequency of the crystal oscillator with extremely high accuracy over a wide temperature range. It has a remarkable effect on the above.

Further, according to the present invention, the design and adjustment of the temperature compensation circuit, which conventionally required a very large number of man-hours, can be extremely simplified.

[Brief explanation of drawings]

Fig. 1 is an equivalent circuit diagram showing the basic configuration of a temperature compensation circuit of a conventional TCXO, Fig. 2 is a practical circuit diagram showing a special example thereof, and Fig. 3 is a basic diagram of the temperature compensation circuit according to the present invention. The equivalent circuit diagrams shown in FIG. 4 and FIG. 5 are the equivalent circuit diagrams of FIG.
An equivalent circuit diagram drawn by converting the star connection, FIG. 6 is a simulation diagram showing changes in the supply voltage to the VCXO with respect to temperature in an embodiment of the temperature compensation circuit according to the present invention, and FIG. Simulation results showing that in an embodiment of such a temperature compensation circuit, there is no change in the compensation characteristics over the entire temperature range even if the voltage applied to the VCXO at the reference temperature is varied to change its oscillation frequency. figure,
FIG. 8 is an equivalent circuit diagram showing means for varying the second power supply voltage in the present invention, and FIG. 9 is an equivalent circuit diagram showing the means for varying the second power supply voltage in the present invention.
N are simulation diagrams showing the degree of compensation provided by the circuit of FIG. 9, respectively. In the equivalent circuit valley elements shown in FIGS. 6, 7, 10, and 11, the values of resistance and voltage are respectively different. 1-・・・・・・VCXo, 2・・・・・・
...Temperature compensation circuit. Circuits connected to ■ to ■・・・・・・ Basic bridge circuit, ■ and ■・・・・・・・・・A pair of opposing nodes ■ and ■・・・・・・・・・Resistance including other sets of nodes, input terminal resistance, etc. R・5!
R9 and R710... Input resistance, R・12. R,14・・・・・・・・・
・Equivalent resistance of the temperature sensing element, R, ■・・・・・・・・・
・Resistor inserted in series with the second power source Patent applicant: Toyo Tsushinki Co., Ltd. 19-40-ri Title of invention 21 filed on May 10, 1988 TCXO temperature compensation circuit 3, case of person making corrections Relationship with Patent applicant Postal code 253-01 Telephone 0467-74
-1131 (Representative) 5. Number of inventions increased by amendment None 6. Subject of amendment Detailed description of the invention, drawings and brief explanation of drawings 7/Amendment (7) Contents As attached appendix 1. Detailed description of the invention The explanation has been amended as follows. (a) p -4/ l -7 "... (hereinafter referred to as vc
(hereinafter referred to as VCX)
A variable actance element (referred to as O), e.g. (b) There was an error in the calculation of the conditional expression in the table of p-1,0, so it was corrected as follows. (c) 5 from the bottom of p-1011 "...Among the above modified examples..." was corrected to "...Among the above modified examples..." do. p-1277? -7r capacitance diode D...
" is corrected to "reactance element...". (DL p-14/l-44r is spacious...
``...'' is corrected to ``It's wide...''. (e) p-14/l-181=-.When frequency-temperature, the r-order term is corrected by 1: ``... Frequency-temperature characteristic?The first-order term of the function expressed.'' 2.P-19 amend the brief description of the drawings as follows:
/Resistor inserted in 1-8r” followed by [VR procedural amendment (
Bamaru) 1. Indication of the case 1982 Patent Application No. 821512, Title of invention TCXO temperature compensation circuit 3, Person making the amendment Relationship to the case Patent applicant 5, Number of inventions increased by the amendment None 6, Subject of the amendment `` "Title of the Invention", "Scope of Claims" and "Detailed Description of the Invention" Contents of Amendment (1. The title of the invention is amended as follows: "Temperature Compensation Circuit for Oscillator" (2. Scope of Claims) Correct as follows: "(8) Crystal oscillator circuit Larium/Larithium which should be temperature compensated.
tantalate, lithium niobate. 8. A temperature compensation circuit for an oscillator according to any one of claims 1 to 7, characterized in that the circuit is replaced with a piezoelectric element such as aluminum phosphate or piezoelectric ceramic. (9) Crystal oscillation circuit 2L that should perform temperature compensation. 8. A temperature compensation circuit for an oscillator according to claims 1 to 7, characterized in that the oscillation circuit is replaced with an oscillation circuit using a passive element such as C or 119. ” is added. (3. The detailed description of the invention is amended as follows. (i) p-3/1-20 rTemperature compensation for the present invention...
``...'' [The present invention is an oscillator, especially a temperature compensated oscillator.
"..." I corrected myself. (2) I1 after p-17/l-12 [Although the above description has been made as a representative of the TCXOi oscillator, the present invention does not necessarily have to be limited thereto.・Niobate. It is obvious that it can be applied to temperature compensation for oscillators using passive elements such as LC or R/C oscillators, whose oscillation frequency is affected by the environmental temperature, as well as oscillators using aluminum phosphate or piezoelectric ceramics. Probably. J'(r
insert. that's all

Claims (1)

[Claims] (1) A reference voltage is applied to a pair of opposing nodes of a basic bridge circuit in which a resistor such as a temperature sensing element is inserted in an arbitrary branch on the same side, and the output voltage of a crystal oscillation circuit is vcx
In the temperature compensation circuit of the TCXO supplied to the VCXO, a voltage is applied from the second power supply to each of the pairs of opposing nodes through the required resistances, and the output voltage supplied to the VCXO is set at a specified reference temperature. In this case, the temperature-applied voltage characteristic is maintained constant regardless of changes in the second power supply voltage.
1. A temperature compensation circuit for a TCXO, characterized in that all circuit constants are set so that they can vary in accordance with the temperature-frequency characteristics of the xo. Q) In any one or more branches of the circuit connected to the basic bridge circuit and the other set of nodes and to which the entire voltage is applied from the second power supply, at least one set of resistors is inserted into the branch. By replacing the variable or selective resistor and temperature sensing element connected in parallel or series, and making the total resistance value the same as the initial resistance value at the reference temperature, and varying the resistance value of the variable or selective resistor, 2. A temperature compensation circuit for a TCXO according to claim 1, wherein temperature compensation is partially performed in a high temperature and/or low temperature region outside the vicinity of a reference temperature. (3) connecting a resistor in series with a power source that generates a voltage to be applied to the other set of opposing nodes of the basic bridge circuit;
Claim 1 or 2, characterized in that the same effect is produced when the output voltage of the power supply is varied by varying the series resistance to vary the voltage applied to the other set of nodes. TCXO temperature compensation circuit. (4) The circuit configuration is simplified by opening the resistors including the input terminal resistors of the crystal oscillation circuit inserted between the other sets of nodes of the basic bridge circuit. A temperature compensation circuit for a TCXO according to range 1, 2 or 3. (5) Changing the oscillation frequency at the reference temperature to a desired value by making variable the resistance including the input terminal resistance of the crystal oscillation circuit inserted between the other sets of nodes of the basic bridge circuit. 4. A temperature compensation circuit for a TCXO according to claim 1, 2 or 3, characterized in that: (6) A patent which is characterized in that the circuit configuration is simplified by making one or both of the resistors inserted into either of the two sets of opposing branches of the basic bridge circuit equivalently infinite. A temperature compensation circuit for a TCXO according to claim 1, 2, 3.4 or 5. (7) A temperature compensation circuit for a TCXO according to any one of claims 1 to 6, wherein one or more of the equivalent resistances constituting the circuit include an equivalent resistance component of a temperature sensing element.