JPH052002B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a highly stable temperature compensated piezoelectric oscillator. [Prior Art] Crystal oscillators and surface acoustic wave oscillators with high frequency stability have been put into practical use as high-frequency and highly stable carrier wave generation sources and timing signal generation sources for wireless equipment, etc.; Increasing the temperature required additional circuitry for temperature compensation. An example of a conventional temperature compensated piezoelectric oscillator is shown in FIG. 4 and will be described. A conventional voltage oscillator of this type, as shown in FIG.
A digital converter 2, a memory circuit 3 that stores a temperature-compensated digital code corresponding to an address specified by the output digital code of the analog-to-digital converter 2, and a memory circuit 3 that converts the output digital code of the memory circuit 3 into an analog signal. It consists of a digital-to-analog converter 4 and a voltage-controlled oscillator 5 controlled by the output of the digital-to-analog converter 4, and has been put into practical use. [Problems to be Solved by the Invention] In the conventional temperature-compensated piezoelectric oscillator described above, the temperature-voltage conversion characteristic of the temperature detector that converts the ambient temperature into a voltage signal is expressed by the following formula: V=AT+B, where V: voltage; T: temperature, A, B: constants, which are expressed as linear functions, but the frequency-temperature characteristics of a temperature-compensated voltage controlled oscillator are approximated by quadratic, cubic, or higher-order functions.
Before and after the inflection point of the high-order function, even if the ambient temperature changes, the frequency changes little, and is within the permissible value of frequency stability required for a temperature-compensated piezoelectric oscillator. In other words, in the conventional temperature compensated piezoelectric oscillator,
Since even unnecessary temperature information was detected, there was a problem in that the capacity of the analog-to-digital converter and memory circuit increased. [Means for Solving the Problems] The temperature compensated piezoelectric oscillator of the present invention includes a temperature detector, an analog-to-digital converter for converting the analog output of the temperature sensor into a digital code, and this analog-to-digital converter. a memory circuit that stores a temperature-compensated digital code corresponding to an address specified by the output digital code of the memory circuit; a digital-to-analog converter that converts the output digital code of this memory circuit into an analog signal; and an output of this digital-to-analog converter. A temperature compensated piezoelectric oscillator comprising a voltage controlled oscillator controlled by
A function generator that generates a voltage similar to the frequency-temperature characteristic of the voltage controlled oscillator is inserted between the temperature detector and the analog-to-digital converter. [Function] In the present invention, the output of a temperature detector that detects the ambient temperature as a voltage signal is supplied to a function generator that generates a voltage similar to the frequency-temperature characteristic of the voltage controlled oscillator, and the output is expressed as a linear function. The temperature information is converted into a voltage signal represented by a higher-order function and supplied to an analog-to-digital converter. [Example] Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing an embodiment of a temperature compensated piezoelectric oscillator according to the present invention. In FIG. 1, the same reference numerals as in FIG. 4 indicate corresponding parts, and 6 is a function generator that generates a voltage similar to the frequency-temperature characteristic of the voltage-controlled oscillator 5;
This function generator 6 is inserted between the temperature detector 1 and the analog-to-digital converter 2. Further, the oscillator of the voltage controlled oscillator 5 is constituted by a surface acoustic wave element. Next, the operation of the embodiment shown in FIG. 1 will be explained. First, the ambient temperature is detected by a temperature detector 1 including a thermistor, etc., and a voltage signal from the temperature detector 1 is supplied to a function generator 6, which generates a voltage controlled oscillator 5.
is converted into a voltage with similar frequency-temperature characteristics. Next, the voltage signal of the function generator 6 is supplied to the analog-to-digital converter 2 and converted into a digital code, and the converted output is supplied to the memory circuit 3. In order to compensate the frequency-temperature characteristics of the voltage controlled oscillator 5, this memory circuit 3 stores in advance a temperature compensation digital code corresponding to the digital code of the analog-to-digital converter 2, which is a temperature address signal. , when the ambient temperature changes, the address signal also changes, and the memory circuit 3
Read the temperature compensated digital code from. This read temperature compensation digital code is
The signal is supplied to a digital-to-analog converter 4 at the next stage and converted into an analog signal, and the analog signal is supplied to a voltage controlled oscillator 5 to compensate for the frequency-temperature characteristics of the voltage controlled oscillator 5. FIG. 2 shows an example of the input/output characteristics of the quadratic function generator 6. In this second figure, the horizontal axis shows the input voltage of the function generator into which temperature information, which is the output voltage of temperature detector 1, is input.
V _IN , the function generator output voltage V _OUT is plotted on the vertical axis, and T-3, T-2, T-1, T ₀ ,
T ₁ , T ₂ , T ₃ indicate the ambient temperature, V ₀ , V _-1 ...
V _-5 indicates voltage. (a) shows a region of characteristics of the present invention, and (b) shows a region of characteristics of a conventional system.
Further, 0 to 16 indicate the input range of the analog-to-digital converter 2. In the case of this Fig. 2, the frequency-temperature characteristic of the voltage controlled oscillator 5 is expressed by an upwardly convex quadratic function, and when the ambient temperature is in the range of T-1 to _T0 to _T1 , the oscillation frequency changes. Voltage V ₀ ~ V _-1 due to small changes
is converted to Also, the ambient temperature T _-3 ~ T _-2 and T ₂
The range ~T ₃ is converted to a voltage V _-3 ~ V _-4 . In this way, by operating to detect the ambient temperature in response to the amount of change in the oscillation frequency, it is possible to detect the ambient temperature much more easily than in the past (see Figure 2b), which detects the ambient temperature at regular intervals. The number of detection points decreases. Conventional method in the case of this figure 2 (see figure 2 b)
The following table shows the number of temperature detection points of the present invention (see FIG. 2a), that is, the input voltage range of the analog-to-digital converter 2.

〔Effect of the invention〕

As explained above, according to the present invention, the voltage range supplied to the analog-to-digital converter can be reduced, so when trying to obtain the same frequency stability of the temperature-compensated piezoelectric oscillator, the analog The capacity of digital converters and memory circuits can be reduced by more than half. Furthermore, if conventional analog-to-digital converters and memory circuit capacities are used, it goes without saying that the frequency stability of the temperature compensated piezoelectric oscillator can be improved by more than twice. As described above, according to the present invention, it is possible to realize a temperature-compensated piezoelectric oscillator that is excellent in terms of performance and cost, and therefore has extremely large practical effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a temperature compensated piezoelectric oscillator according to the present invention, and FIGS. 2 and 3 are diagrams of a quadratic function generator and a cubic function generator used to explain the operation of FIG. FIG. 4 is a block diagram showing an example of a conventional temperature compensated piezoelectric oscillator. DESCRIPTION OF SYMBOLS 1... Temperature detector, 2... Analog-digital converter, 3... Memory circuit, 4... Digital-analog converter, 5... Voltage controlled oscillator, 6... Function generator.

Claims (1)

[Claims] 1. A temperature detector, an analog-to-digital converter that converts the analog output of the temperature sensor into a digital code, and a temperature corresponding to an address specified by the output digital code of the analog-to-digital converter. Temperature compensation comprising a memory circuit for storing a compensation digital code, a digital-to-analog converter for converting the output digital code of the memory circuit into an analog signal, and a voltage-controlled oscillator controlled by the output of the digital-to-analog converter. type piezoelectric oscillator, the temperature sensor and the analog
A temperature-compensated piezoelectric oscillator, characterized in that a function generator that generates a voltage similar to the frequency-temperature characteristics of the voltage-controlled oscillator is inserted between the digital converter and the digital converter. 2. The temperature compensated piezoelectric oscillator according to claim 1, wherein the oscillator of the voltage controlled oscillator is constituted by a surface acoustic wave element.