Signal generation device

Abstract

To simplify an operation for calibrating the frequency of an internal reference signal.SOLUTION: A signal generation device comprises: an output oscillator 1 that generates an oscillation signal of a first frequency corresponding to a control voltage; a control unit 9 that controls a second frequency of an internal reference signal; a phase synchronization circuit 2 that generates a signal of the control voltage on the basis of a difference between the first frequency and a frequency of an input signal; and a switch 4 that switches between an internal input mode in which the internal reference signal is input as an input signal to the phase synchronization circuit 2 and an external input mode in which the external reference signal of a predetermined frequency input from the external device is input as an input signal to the phase synchronization circuit; and a measurement unit that measures the control voltage. The control unit 9 controls the second frequency so that the control voltage measured by the measurement unit while the internal reference signal was being input to the phase synchronization circuit 2 in the internal input mode agrees with the control voltage measured by the measurement unit while the external reference signal was input to the phase synchronization circuit 2 in the external input mode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a signal generation device that generates an oscillation signal.

Background Art

[0002] A synchronization circuit that generates a signal synchronized with an internal reference signal generated by an oscillation circuit or the like is known. For example, Patent Document 1 describes synchronizing an output signal output from a voltage controlled oscillator with this internal reference signal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Due to aging deterioration or the like, the accuracy of the frequency of the internal reference signal may decrease. In the technique described in Patent Document 1, when the accuracy of the frequency of the internal reference signal decreases, it is necessary to open the cover of the signal generation device and manually calibrate the frequency of the internal reference signal.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a signal generation device capable of simplifying the operation of calibrating the frequency of an internal reference signal.

Means for Solving the Problems

[0006] The signal generation device according to the first aspect of the present invention includes an output oscillator that generates an oscillation signal having a first frequency corresponding to a control voltage, a control unit that controls a second frequency of an internal reference signal, and a phase synchronization circuit that generates a signal of the control voltage based on a difference between the first frequency and a frequency of an input signal. The signal generation device further includes a switching switch that switches between an internal input mode in which the internal reference signal is input to the phase synchronization circuit as the input signal and an external input mode in which an external reference signal having a predetermined frequency input from an external device is input to the phase synchronization circuit as the input signal, and a measurement unit that measures the control voltage. The control unit controls the second frequency so that the control voltage measured by the measurement unit while the external reference signal is input to the phase synchronization circuit in the external input mode matches the control voltage measured by the measurement unit while the internal reference signal is input to the phase synchronization circuit in the internal input mode.

[0007] The control unit may control the switching switch so as to switch from the external input mode to the internal input mode after a difference between the first frequency and the frequency of the external reference signal becomes less than a threshold value. The signal generation device further includes an internal reference oscillator that generates the internal reference signal, and a storage unit that stores an auxiliary control voltage of a signal for controlling the second frequency of the internal reference signal generated by the internal reference oscillator. The control unit causes the internal reference signal having the second frequency corresponding to the auxiliary control voltage stored in the storage unit in the internal input mode to be input to the phase synchronization circuit, and updates the value of the auxiliary control voltage stored in the storage unit to the value of the auxiliary control voltage when the control voltage measured by the measurement unit while the external reference signal is input to the phase synchronization circuit in the external input mode matches the control voltage measured by the measurement unit while the internal reference signal is input to the phase synchronization circuit in the internal input mode.

Advantages of the Invention

[0008] According to the present invention, there is an effect of simplifying the operation of calibrating the frequency of the internal reference signal.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0010] [Configuration of Signal Generation Device] FIG. 1 shows the configuration of the signal generation device 100 of the present embodiment. The signal generation device 100 includes an output oscillator 1, a PLL (Phase Locked Loop) 2, an output terminal 3, a changeover switch 4, an A / D converter (corresponding to a measurement unit) 5, a D / A converter 6, a VCO (corresponding to an internal reference oscillator) 7, a storage unit 8, and a control unit 9.

[0011] The output oscillator 1 generates an oscillation signal of a first frequency. The output oscillator 1 is, for example, a VCO (Voltage Controlled Oscillator). The output oscillator 1 generates an oscillation signal of a first frequency corresponding to the main control voltage of the signal input from the PLL 2. For example, the higher the main control voltage of the output oscillator 1, the higher the frequency of the generated oscillation signal. The output oscillator 1 outputs the generated oscillation signal to the outside via the output terminal 3.

[0012] The PLL 2 inputs a signal for controlling the first frequency of the signal generated by the output oscillator 1 to the output oscillator 1. The PLL 2 generates a control voltage signal corresponding to the difference between the first frequency of the oscillation signal fed back from the output oscillator 1 and the frequency of the input signal input from the changeover switch 4. The PLL 2 increases or decreases the control voltage of the signal input to the output oscillator 1 so that the first frequency of the oscillation signal approaches the frequency of the input signal.

[0013] The switching switch 4 is an element for outputting one of a plurality of input signal sources. The switching switch 4 switches between an internal input mode and an external input mode based on a control signal input from the control unit 9. In the internal input mode, the internal reference signal generated by the VCO 7 is input to the PLL 2 as an input signal. In the external input mode, an external reference signal generated by an external device (not shown) is input to the PLL 2 as an input signal. The external device is, for example, a rubidium oscillator capable of outputting an oscillation signal with a frequency higher than the second frequency of the internal reference signal.

[0014] The A / D converter 5 converts the main control voltage of the signal that the PLL 2 inputs to the output oscillator 1 into a digital value. The A / D converter 5 is used for measuring this main control voltage. The A / D converter 5 inputs the converted digital value to the control unit 9. The D / A converter 6 converts the digital signal generated by the control unit 9 into an analog signal. The D / A converter 6 inputs a signal for controlling the second frequency of the internal reference signal generated by the VCO 7 to the VCO 7. The auxiliary control voltage of the signal that the D / A converter 6 inputs to the VCO 7 is set by the control unit 9.

[0015] The VCO 7 is an internal reference oscillator that generates an internal reference signal of the second frequency. The VCO 7 generates an internal reference signal of the second frequency corresponding to the auxiliary control voltage of the signal input from the D / A converter 6. For example, the higher the auxiliary control voltage, the higher the second frequency of the internal reference signal generated by the VCO 7. The VCO 7 outputs the generated internal reference signal to the switching switch 4.

[0016] The memory unit 8 is a storage medium including a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The memory unit 8 stores programs executed by the control unit 9. The memory unit 8 stores a predetermined auxiliary control voltage of a signal for controlling the second frequency of the internal reference signal generated by the VCO 7. The predetermined auxiliary control voltage is, for example, an initial value determined by the manufacturer at the time of manufacturing the signal generation device 100. The control unit 9 is, for example, a CPU (Central Processing Unit). The control unit 9 executes various functions by executing the programs stored in the memory unit 8.

[0017] For example, the control unit 9 controls the second frequency of the internal reference signal. By controlling the second frequency of the internal reference signal, the control unit 9 indirectly controls the first frequency generated by the output oscillator 1. More specifically, in the internal input mode, the control unit 9 reads out from the memory unit 8 an auxiliary control voltage of a signal for controlling the second frequency of the internal reference signal, and sets the read auxiliary control voltage to the D / A converter 6. At this time, the D / A converter 6 converts the digital signal generated by the control unit 9 into an analog signal, and inputs the signal of the set auxiliary control voltage to the VCO 7. In this way, the control unit 9 causes the VCO 7 to generate an internal reference signal having a second frequency corresponding to this auxiliary control voltage, and inputs the generated internal reference signal to the PLL 2.

[0018] The control unit 9 controls the changeover switch 4 so as to switch between the internal input mode and the external input mode. For example, in the external input mode, after the difference between the first frequency of the oscillation signal generated by the output oscillator 1 and the external frequency of the external reference signal becomes less than the threshold value (that is, after the PLL 2 is locked), the control unit 9 controls the changeover switch 4 so as to switch from the external input mode to the internal input mode. The threshold value is determined based on, for example, the maximum value of the allowable error at the first frequency of the oscillation signal of the signal generation device 100.

[0019] Incidentally, due to aging deterioration or the like, the accuracy with which the control unit 9 controls the second frequency of the internal reference signal may decrease. The control unit 9 calibrates the auxiliary control voltage set in the D / A converter 6 for the purpose of suppressing a decrease in the accuracy of controlling the second frequency.

[0020] Hereinafter, the processing procedure for calibrating the auxiliary control voltage by the control unit 9 will be described. First, the control unit 9 sets the changeover switch 4 to the external input mode. While the external reference signal is input to the PLL2 in the external input mode, the control unit 9 measures, by means of the A / D converter 5, the main control voltage (hereinafter also referred to as the reference control voltage) of the signal that the PLL2 inputs to the output oscillator 1. The control unit 9 causes the storage unit 8 to store the reference control voltage.

[0021] Next, the control unit 9 reads out the auxiliary control voltage stored in the storage unit 8 and sets the read auxiliary control voltage in the D / A converter 6. The auxiliary control voltage stored in the storage unit 8 is, for example, the auxiliary control voltage used at the time before calibration. After setting the auxiliary control voltage, the control unit 9 switches the changeover switch 4 from the external input mode to the internal input mode. The D / A converter 6 inputs the signal of the auxiliary control voltage set by the control unit 9 to the VCO7, and the VCO7 outputs an internal reference signal having a frequency corresponding to this auxiliary control voltage to the PLL2.

[0022] While the internal reference signal is input to PLL2 in the internal input mode, the control unit 9 measures the main control voltage of the signal input to the output oscillator 1 by means of the A / D converter 5. The control unit 9 controls the second frequency so that the main control voltage measured while the internal reference signal is input to PLL2 in the internal input mode matches the reference control voltage stored in the storage unit 8. In the example of FIG. 1, the control unit 9 controls the second frequency by changing the auxiliary control voltage set in the D / A converter 6. The control unit 9 identifies the auxiliary control voltage corresponding to the main control voltage when the measured main control voltage matches the main control voltage when the external reference signal is input to PLL2 in the external input mode. The control unit 9 updates the value of the auxiliary control voltage stored in the storage unit 8 to the identified value of the auxiliary control voltage.

[0023] <Procedure for calibrating the target value of the second frequency by the control unit 9> FIG. 2 is a flowchart showing the procedure for calibrating the target value of the second frequency by the control unit 9. The procedure shown in FIG. 2 starts, for example, when an operation to start calibration is performed on the signal generation device 100. First, the control unit 9 sets the changeover switch 4 to the external input mode (S101).

[0024] The control unit 9 determines whether it is in a PLL locked state where the difference between the first frequency of the oscillation signal generated by the output oscillator 1 and the external frequency of the external reference signal input to PLL2 is equal to or less than the threshold value (S102). When the control unit 9 determines that it is in the PLL locked state (YES in S102), the control unit 9 measures the reference control voltage of the signal that PLL2 inputs to the output oscillator 1 by means of the A / D converter 5 (S103). The control unit 9 causes the storage unit 8 to store the reference control voltage.

[0025] Subsequently, the control unit 9 reads out from the storage unit 8 the auxiliary control voltage of the signal for controlling the second frequency of the internal reference signal. The control unit 9 sets the read auxiliary control voltage in the D / A converter 6 (S104).

[0026] Subsequently, the control unit 9 switches the switching switch 4 to the internal input mode (S105). After determining that the PLL is in the locked state where the difference between the first frequency of the oscillation signal generated by the output oscillator 1 and the second frequency of the internal reference signal input to the PLL2 is equal to or less than the threshold value, the control unit 9 measures the main control voltage of the signal input from the PLL2 to the output oscillator 1 using the A / D converter 5.

[0027] The control unit 9 determines whether or not the main control voltage measured when it determines that the PLL is in the locked state matches the reference control voltage stored in the storage unit 8 (S106). When the control unit 9 determines that the measured main control voltage and the reference control voltage match (YES in S106), it specifies the auxiliary control voltage when the two main control voltages match. The control unit 9 updates the value of the auxiliary control voltage stored in the storage unit 8 to the specified value of the auxiliary control voltage (S108) and ends the process.

[0028] When the control unit 9 determines in the determination of S102 that the PLL is not in the locked state (NO in S102), it repeats the determination of S102. When the control unit 9 determines in the determination of S106 that the measured main control voltage and the reference control voltage do not match (NO in S106), it changes the second frequency by changing the auxiliary control voltage set in the D / A converter 6 (S107) and returns to the determination of S106.

[0029] [Effect of the signal generation device 100 of the present embodiment] According to the signal generation device 100 of the present embodiment, the control unit 9 controls the second frequency of the internal reference signal so that a signal having the same main control voltage as the reference control voltage when the external reference signal is input to the PLL2 in the external input mode is input to the output oscillator 1, so that it is possible to suppress a decrease in the accuracy of controlling the second frequency of the internal reference signal.

[0030] As described above, the present invention has been explained using the embodiments. However, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist. For example, all or part of the device can be configured by functionally or physically dispersing and integrating it in an arbitrary unit. Also, new embodiments generated by any combination of a plurality of embodiments are included in the embodiments of the present invention. The effects of the new embodiments generated by the combination have the effects of the original embodiments combined.

Explanation of Signs

[0031] 1 Output oscillator 2 Phase synchronization circuit 3 Output terminal 4 Switching switch 5 A / D converter 6 D / A converter 8 Storage unit 9 Control unit 100 Signal generation device

Claims

1. An output oscillator that generates an oscillation signal of a first frequency corresponding to a control voltage; A control unit that controls a second frequency of an internal reference signal; A phase-locked loop circuit that generates a signal of the control voltage based on a difference between the first frequency and a frequency of an input signal; A switching switch that switches between an internal input mode in which the internal reference signal is input to the phase-locked loop circuit as the input signal and an external input mode in which an external reference signal of a predetermined frequency input from an external device is input to the phase-locked loop circuit as the input signal; A measurement unit that measures the control voltage; Comprising: The control unit controls the second frequency so that the control voltage measured by the measurement unit while the external reference signal is input to the phase-locked loop circuit in the external input mode matches the control voltage measured by the measurement unit while the internal reference signal is input to the phase-locked loop circuit in the internal input mode. A signal generation device.

2. The control unit controls the switching switch so as to switch from the external input mode to the internal input mode after a difference between the first frequency and the frequency of the external reference signal becomes less than a threshold value. The signal generation device according to Claim 1.

3. An internal reference oscillator that generates the internal reference signal; Further comprising a storage unit that stores an auxiliary control voltage of a signal for controlling the second frequency of the internal reference signal generated by the internal reference oscillator, The control unit causes the internal reference signal of the second frequency corresponding to the auxiliary control voltage stored in the storage unit in the internal input mode to be input to the phase-locked loop circuit, and when the control voltage measured by the measurement unit while the external reference signal is input to the phase-locked loop circuit in the external input mode matches the control voltage measured by the measurement unit while the internal reference signal is input to the phase-locked loop circuit in the internal input mode, updates the value of the auxiliary control voltage stored in the storage unit to the value of the auxiliary control voltage at that time. The signal generation device according to Claim 1 or 2.

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