JPH1065446A - Digital temperature compensation type oscillator and radio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the digital temperature compensation type oscillator from which occurrence of a steep phase fluctuation at a change point of temperature control is eliminated by providing a latch circuit that latches an output of a memory circuit outputting digital data for temperature compensation with an external control signal. SOLUTION: Temperature compensation digital data outputted from a memory 5 are latched by a latch circuit 6 with an external control signal. When the latch circuit 6 latches data, a voltage signal outputted from a D/A converter 7 is a temperature compensation voltage just before latching. A constant voltage without a change independently of an ambient temperature change is given to a voltage controlled crystal oscillator 11 via a filter 9. Thus, the phase of an output frequency of the voltage controlled crystal oscillator 11 is not steeply changed during the operation of the latch circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a temperature compensated oscillator,
In particular, the present invention relates to a digital temperature-compensated oscillator capable of temporarily holding a compensation function by an external control signal, and a radio using the digital temperature-compensated oscillator.

[0002]

[Prior art]

[0003] A temperature-compensated crystal oscillator is widely used as a reference oscillator of a radio device or the like. As a temperature compensation circuit, for example, an analog circuit that changes a load capacitance value of an oscillation circuit by using a resistance change due to the temperature of a thermistor is used. A temperature-compensated crystal oscillator of the type is used in mobile phones and the like.

[0004] In particular, in portable electric appliances and the like, the number of channels has been increased, and as a result, the frequency interval between adjacent channels has become narrower, and the frequency stability required for the reference oscillator has been correspondingly increased. For this reason, a digital temperature-compensated crystal oscillator capable of obtaining an oscillation frequency with higher stability has been proposed and put into practical use.

FIG. 5 is a block diagram showing a specific example of a conventional digital temperature compensation type crystal oscillator. In FIG. 1, reference numeral 1 denotes a temperature detecting unit (for example, a thermistor or a semiconductor temperature sensor) that detects a change in ambient temperature and outputs an analog value corresponding to the temperature, and an AD converter 3 that converts the analog output into digital data. A memory 5 for storing specific temperature compensation data in advance using the digital data as address information, and outputting compensation data for the temperature based on the output data of the AD converter 3;
A DA converter 7 for converting digital data in the memory 5 into an analog signal; a filter 9 for removing noise components of the analog signal; and a voltage controlled crystal oscillator controlled according to a temperature-compensated analog signal output through the filter 9 And 11.

When analog data, for example, a voltage value, output from the temperature detecting section 1 in response to a temperature change is input to the AD converting section 3, it is converted into a predetermined digital signal. The memory 5 stores in advance a digital signal for temperature compensation corresponding to the digital signal from the AD converter 3 as an address, and stores a predetermined digital signal for temperature compensation in accordance with an input from the AD converter 3. It is supplied to the conversion unit 7.

The DA converter 7 supplies an analog signal corresponding to the digital signal from the memory 5 to the voltage controlled crystal oscillator 11 via the filter 9 for removing a noise component.

The voltage controlled crystal oscillator 11 changes the frequency in accordance with the input voltage level, operates based on the temperature compensation signal stored in the memory 5, and changes in response to ambient temperature fluctuation. Function so that a constant frequency is always obtained.

[0009] On the other hand, in the field of digital mobile phones, phase shift keying (PSK) in which a carrier is modulated with a digital signal when wirelessly transmitting digital information.
ng) is the mainstream. FIG. 6 shows an example of a carrier to be modulated in the case of two-phase PSK, digital information which is a signal for modulating the carrier, and a modulated wave which has been modulated. When the value of the digital signal, which is a modulation signal, is 1, the phase of the carrier does not change and the phase becomes 0 °, and the carrier becomes the modulated wave as it is. When the value of the digital signal is 0, the modulated wave phase-modulated according to the digital signal is obtained by changing the phase of the carrier by 180 °. As described above, the digital temperature compensated oscillator is used for a reference oscillator of a mobile phone or the like, and is used, for example, as a reference signal source of a carrier generating means such as a phase modulator as shown in FIG. That is, the output of the temperature-compensated oscillator 22 is supplied to a carrier signal generator 27 composed of a PLL including a phase locked loop 23 and a voltage-controlled oscillator 25, and the output is guided to a phase modulator 29 as a carrier. As described above, the phase is modulated by the digital data. At this time, if the oscillator output fluctuates due to a change in temperature, the phase of the carrier wave itself fluctuates, and it is not possible to obtain the intended phase-modulated wave, so some kind of temperature compensation is necessary. It is common to provide.

However, when the above-mentioned conventional digital temperature-compensated crystal oscillator is used in a communication device of the phase modulation system, a control voltage for temperature compensation output in response to a change in ambient temperature is generated as digital data. Therefore, the voltage data for controlling the oscillation frequency becomes a discrete value having a step shape. Controlling the oscillation frequency of a voltage-controlled crystal oscillator with a discrete voltage in this way corresponds to changes in ambient temperature,
A sharp phase change occurs at the data transition, and as a result, the phase change of the digital temperature-compensated crystal oscillator appears on the carrier wave as it is, causing the original phase modulation information to be erroneous.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to eliminate the drawbacks of the digital temperature-compensated oscillator as described above, and eliminates the occurrence of steep phase fluctuations even at a change point in temperature control. It is another object of the present invention to provide a digital temperature compensated oscillator suitable for a phase modulation type communication device.

[0012]

In order to achieve the above object, a digital temperature compensated oscillator according to the present invention comprises a temperature detecting section for detecting an ambient temperature in order to compensate for a frequency variation with respect to an ambient temperature variation of the oscillator. An AD converter for converting the analog output of the temperature detector into digital data, and a memory circuit for outputting digital data for temperature compensation using the digital output data of the AD converter as address information. And the digital output data of this memory circuit.
And a D / A converter for converting the data into an analog voltage signal.
A digital temperature-compensated oscillator comprising a voltage-controlled oscillator controlled by an analog voltage output of an A-converter, provided with a holding circuit for holding an output of the memory circuit by an external control signal. The function is such that the holding circuit is made to function before the modulator or the demodulator operates, and the function of the holding circuit is stopped by the external control signal after the operation of the modulation or the demodulator ends. Further, in the wireless device according to the present invention, in a wireless device including a modulator for phase-modulating a carrier wave with a digital signal to be transmitted and a digital temperature compensated oscillator, the digital temperature compensated oscillator detects an ambient temperature. A temperature detector for converting the analog output of the temperature detector into digital data;
A memory circuit for outputting digital data for temperature compensation based on the digital output data of the AD converter, a DA converter for converting the digital output data of the memory circuit into an analog voltage signal, A voltage controlled oscillator controlled by an analog voltage output of a DA converter; and a holding circuit for holding an output of the memory circuit by an external control signal, wherein the memory is controlled by the external control signal while the modulator is activated. The temperature control based on the new temperature compensation data is performed by holding the output of the circuit and clearing the holding circuit while the modulator is not activated. Further, when a malfunction occurs due to a phase change of the digital temperature compensated oscillator during the reception operation, the latch circuit is similarly operated during the reception operation,
The latch circuit is configured to be cleared during the non-receiving operation.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments.

FIG. 1 is a block diagram of a digital temperature compensated crystal oscillator showing one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a temperature detector which detects a change in ambient temperature and outputs an analog value corresponding to the temperature, an AD converter 3 for converting the analog output to digital data, Memory 5 for outputting temperature compensation data in which data is set as address information
A latch circuit 6 for holding digital data in a memory 5 by an external control signal, a DA converter 7 for converting digital data into an analog signal, a filter 9 for removing noise components in the analog signal, and a filter 9
And a voltage-controlled crystal oscillator 11 that is controlled based on a temperature-compensated analog signal output through the control circuit.

According to the above configuration, the temperature compensating digital data output from the memory 5 can be held in the latch circuit 6 by the external control signal, and during the data holding operation in the latch circuit 6, the DA converter 7 Is a temperature compensation voltage immediately before the voltage is held, a constant value that does not change regardless of the ambient temperature change is supplied to the voltage controlled crystal oscillator 11 through the filter 9. Therefore, during the operation of the latch circuit 6, the voltage-controlled crystal oscillator 11
Since the phase of the output frequency does not suddenly change, during operation of the modulator, that is, during transmission, by operating the latch circuit by an external control signal, a phase change due to the output of the digital temperature compensated oscillator itself is obtained. The above-mentioned conventional problems can be solved by preventing such a situation and clearing the latch circuit while the modulator is not operating to perform temperature control using new digital data.

FIG. 2 shows an example of a phase modulator in a radio using the digital temperature-compensated crystal oscillator 21 of the present invention as a carrier reference oscillator for phase modulation. The phase modulator shown in this example includes a digital temperature compensation crystal oscillator 21 having an external control signal input terminal for holding temperature compensation data, a phase synchronization circuit 23 using this oscillator output as a reference signal, and a phase synchronization circuit 23. A carrier signal generator 27 having a voltage controlled oscillator 25 synchronized with a reference signal;
7 comprises a phase modulating section 29 for phase modulating the carrier outputted from the carrier 7. Eliminating steep phase fluctuations of the reference signal by holding the temperature compensation data by the external control signal, and performing phase modulation on a carrier wave that prevents phase fluctuations synchronized with the signal, thereby generating the modulation generated during phase modulation. Errors can be eliminated.

As an example of the external control signal generation timing, for example, a TDMA (Time Division Multiplot) used in a digital mobile communication system is used.
uleAccess), in a communication system in which a specific frequency is used by a plurality of users in a time-division manner, one frequency is allocated and used at regular intervals as shown in FIG.

FIG. 3 (b) shows the transmission / reception timing of the user in slot # 1. During the transmission and reception slots, the latch circuit is turned on to prevent a sharp phase change from occurring. In this case, the latch may be turned off during the idle slot to perform a normal operation of compensating the frequency in accordance with the temperature compensation information corresponding to the change in ambient temperature.

In this example, it is possible to realize a digital temperature-compensated crystal oscillator that is not affected by phase fluctuations at the time of transmission and reception in which temperature compensation is performed every 20 ms and phase modulation and demodulation are performed.

FIG. 4 is a block diagram of a digital temperature compensated crystal oscillator showing another embodiment of the present invention. FIG.
The same parts as those of the previous embodiment are denoted by the same reference numerals, and description thereof is omitted.

A feature of this embodiment is that, while the above embodiment eliminates a sudden change in phase by holding digital data by an external control signal, this embodiment has a case where analog data is held by an external control signal. It is for explanation. That is, by providing a holding circuit 8 (for example, a sample and hold circuit) for holding an analog signal output from the DA converter 7 by an external control signal, the same effect as in the previous embodiment can be obtained. It is also conceivable to insert an analog data holding circuit such as a sample-and-hold circuit between the temperature detecting section 1 and the AD converting section 3. In this case, however, the temperature stability of the holding circuit itself affects the output. May not be stable, and therefore, even during the holding operation, the address of the memory may be changed via the AD conversion unit, and the phase of the signal output from the voltage controlled oscillator 11 may be changed. . Therefore, if there is such a danger, the holding circuit 8 may be configured as described above.
However, even if there is a slight temperature fluctuation, the fluctuation of the control signal input to the voltage controlled crystal oscillator 11 is suppressed by the filter 9, and there is almost no influence on the phase modulator. However, if the fear or the effect is small, the method described later will be no problem.

It should be noted that the present invention has been described with reference to the digital mobile phone P
The case where the present invention is applied to the reference oscillator of the SK modulation unit has been described as an example, but the present invention is not limited to this, and may be a wired communication system, and is also applicable to analog phase modulation. .

Also, an example using a quartz oscillator as the voltage controlled oscillator constituting the present invention has been described. However, a voltage using a piezoelectric single crystal such as LiNbO3 or LiTaO3 or a piezoelectric ceramic other than quartz, such as LiNbO3 or LiTaO3. You may comprise using a control oscillator, an LC oscillator, a dielectric band oscillator, etc.

[0025]

Since the present invention is constructed as described above, it is possible to suppress a steep phase fluctuation when a digital temperature-compensated crystal oscillator is used as a reference oscillator at the time of phase modulation / demodulation and to prevent a data error at the time of modulation / demodulation. It has a remarkable effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a digital temperature compensated crystal oscillator according to the present invention.

FIG. 2 is a block diagram showing an example of a phase modulator in the wireless device according to the present invention.

FIG. 3 is a diagram for explaining the present invention, wherein (a)
FIG. 3 is a diagram showing a communication system (TDMA) of a digital mobile phone, and FIG.

FIG. 4 is a block diagram showing a configuration of another embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional digital temperature compensated oscillator.

FIG. 6 is a diagram showing a two-phase PSK phase modulation signal of a phase modulator in a wireless device.

FIG. 7 is a block diagram of a phase modulator in a conventional wireless device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Temperature detection part 3 ... AD conversion part 5 ... Memory 7 ... DA conversion part 9 ... Filter 11 ... Voltage control crystal oscillator 21 ... Digital temperature compensation crystal oscillator 22 ... Conventional digital temperature compensation crystal Oscillator 23 Phase synchronization circuit 25 Voltage controlled oscillator 27 Carrier signal generator 29 Phase modulator

Claims (3)

[Claims] A temperature detector for detecting an ambient temperature, an A / D converter for converting an analog output of the temperature detector into digital data, and a temperature compensation based on digital output data of the A / D converter. Circuit for outputting digital data for use in the memory circuit, a D / A converter for converting digital output data of the memory circuit into an analog voltage signal, and a voltage controlled oscillator controlled by the analog voltage output of the D / A converter. A digital temperature compensated oscillator comprising: a holding circuit for holding an output of the memory circuit by an external control signal. 2. A radio apparatus comprising: a modulator for phase-modulating a carrier with a digital signal to be transmitted; and a digital temperature-compensated oscillator. The digital temperature-compensated oscillator includes a temperature detector for detecting an ambient temperature. An AD converter for converting the analog output of the temperature detector into digital data; a memory circuit for outputting digital data for temperature compensation based on the digital output data of the AD converter; DA for converting digital output data of a memory circuit into an analog voltage signal
A converter, a voltage-controlled oscillator controlled by an analog voltage output of the D / A converter, and a holding circuit for holding an output of the memory circuit by an external control signal. A wireless device that holds an output of the memory circuit by a control signal and performs temperature control based on new temperature compensation data by clearing the holding circuit while the modulator is not activated. . 3. A radio apparatus using an output of a digital temperature compensated oscillator during a receiving operation, wherein said digital temperature compensated oscillator includes a temperature detector for detecting an ambient temperature, and an analog output of the temperature detector for digital data. A / D converter for converting the data into digital data, a memory circuit for outputting digital data for temperature compensation based on the digital output data of the A / D converter, and an analog voltage signal DA to convert to
A converter, a voltage controlled oscillator controlled by an analog voltage output of the DA converter, and a holding circuit for holding an output of the memory circuit by an external control signal, wherein the memory is controlled by the external control signal during a reception operation. A wireless device configured to hold an output of a circuit and perform temperature control based on new temperature compensation data by clearing the holding circuit during a non-receiving operation.