JP6172989B2 - Oscillator - Google Patents

Description

  The present invention relates to a technical field in an oscillation device including a so-called thermostatic chamber-equipped piezoelectric oscillator that takes out output in a state where the temperature of the piezoelectric oscillator is stabilized after power is turned on.

  A crystal oscillator with a thermostat (OCXO: Oven Controlled Xtal Oscillator) is equipped with a heater to stabilize the oscillation frequency by stabilizing the temperature of the atmosphere in the thermostat where the crystal oscillator, which is a piezoelectric vibrator, is placed. ing. The heater is controlled in power supply so that the temperature detection value of the temperature sensor in the thermostatic chamber becomes the set temperature.

  When the detected temperature of the atmosphere by the temperature sensor is stabilized at the set temperature after the crystal oscillator is turned on, the crystal oscillator outputs a signal indicating that (oven alarm release signal) to the control circuit, and the control circuit A predetermined signal is output to the device (applied equipment of the crystal oscillator). In accordance with this signal, the operation of the host device is started, and the host device operates by taking in the oscillation output from the crystal oscillator. However, even if the temperature sensor detects that the temperature has reached the set temperature, it may take some time for the overall temperature in the thermostat to become uniform, and the oscillation frequency of the crystal oscillator is unstable for a while. May continue. The time from when the power is turned on until the temperature sensor detects that the temperature inside the thermostatic chamber has reached the set temperature, from when the set temperature is detected until the oscillation frequency is actually stabilized These times vary depending on the ambient temperature of the crystal oscillator.

  For this reason, there is a risk that the operation of the host device may be started in a state where the oscillation frequency of the crystal oscillator is not stable. For example, when the host device is a radio wave transmitter of a television broadcasting station, there is a problem that the image is disturbed because the oscillation output of the crystal oscillator is unstable. Further, when the host device is a mobile phone base station, a problem that radio waves cannot be transmitted and received occurs. In order to prevent such a situation, it is conceivable to start the operation of the host device after a sufficient time has elapsed since the inside of the thermostatic chamber reached the set temperature, but the frequency is already in a state where the operation can be started stably. However, the operation efficiency of the host device is reduced because the operation is postponed.

  Japanese Patent Application Laid-Open No. H10-228688 describes a technique in which an offset voltage of a control voltage for an oscillation circuit is controlled according to a temperature detected by a temperature sensor in a crystal oscillation device. Further, Patent Document 2 describes a technique for controlling a constant-temperature bath type voltage-controlled oscillator depending on whether or not the output of the atomic oscillator is stable. However, in these techniques, a technique for solving the above problem is described. Is not listed.

Japanese Patent Laid-Open No. 10-145139 JP 2006-314047 A

  The present invention has been made under such circumstances, and an object of the present invention is to provide an external device with high accuracy when the oscillation frequency of the oscillation device after power-on is stabilized in an oscillation device including a so-called thermostatic oscillator. It is to provide a technology capable of informing.

An oscillation device of the present invention includes an oscillation circuit using a piezoelectric vibrator,
A heater for maintaining the temperature of the atmosphere in which the piezoelectric vibrator is provided at a set temperature;
A temperature sensor that detects the temperature of the atmosphere and outputs a signal corresponding to the detected temperature;
After turning on the power, after receiving a first detection signal indicating that the temperature of the atmosphere has reached the set temperature by the heater from the temperature sensor, it is confirmed that the oscillation frequency output from the oscillation circuit has become stable. A control circuit for informing,
Regarding the correspondence between the second detection signal output from the temperature sensor to the control circuit when the power is turned on and the delay time from when the control circuit receives the first detection signal until the notification is performed, A storage unit that stores the control circuit so that the notification can be performed based on the correspondence;
It is provided with.

For example, a control signal output to the oscillation circuit is supplied from a signal output unit provided in the oscillation device so as to output a signal based on an external signal supplied from the outside of the oscillation device to the oscillation device. A switching unit for switching between a signal and a spare signal for replacement of the signal supplied from the signal output unit , and a detection unit for detecting the presence or absence of an abnormality by detecting the external signal , The control circuit controls the operation of the switching unit according to the detection result of the detection unit. The correspondence relationship includes a first correspondence relationship and a second correspondence relationship in which the correspondence between the second detection signal and the delay time is different from each other , and includes the first correspondence relationship and the second correspondence relationship. The control circuit outputs the notification signal based on the first correspondence when the reference signal is supplied to the oscillation circuit, and the control circuit outputs the notification signal when the preliminary signal is supplied to the oscillation circuit. The notification signal is output based on the correspondence relationship between the two.

  According to the oscillation device of the present invention, after the oscillation device is powered on, after receiving the first detection signal indicating that the temperature of the atmosphere in which the piezoelectric vibrator is provided by the heater from the temperature sensor has reached the set temperature, A control circuit for notifying that the oscillation frequency has stabilized is provided, and this control circuit delays after receiving the second detection signal output from the temperature sensor when the power is turned on and the first detection signal. The notification is performed according to the correspondence with time. Thereby, it is possible to notify the outside when the oscillation frequency is stabilized with high accuracy. As a result, after the oscillation frequency is stabilized, the host device that uses the oscillation frequency can be operated quickly. That is, the host device can be operated in a stable state and efficiently.

1 is a block diagram of a frequency synthesizer according to an embodiment of the present invention. It is a circuit diagram of OCXO which comprises the said frequency synthesizer. It is the graph which showed the relationship between the temperature of said OCXO, and the signal output. It is explanatory drawing which shows the relationship between the detection temperature around OCXO, and the offset time until a status signal is changed. It is a graph which shows the test result of the evaluation test relevant to this invention. It is a graph which shows the test result of the evaluation test relevant to this invention. It is a graph which shows the test result of the evaluation test relevant to this invention. It is a block diagram of another frequency synthesizer. It is a perspective view of the shield block of the frequency synthesizer. It is a perspective view of another shield block.

  FIG. 1 shows a frequency synthesizer 1 which is an embodiment of the oscillation device of the present invention. The frequency synthesizer 1 includes a PLL integrated circuit unit (PLL-IC) 11, a switch 12, a loop filter 13, an OCXO 20, a fixed voltage supply terminal 14, and a variable resistor 15. The PLL-IC 11 synchronizes, for example, an external reference signal of 10 MHz supplied from the outside of the frequency synthesizer 1 with the frequency signal output from the OCXO 20, and outputs the set frequency signal to the subsequent stage. Specifically, for example, a frequency dividing unit that divides the output signal from the OCXO 20 and the frequency signal corresponding to the phase difference between the phase of the divided output signal and the phase of the external reference signal are extracted and output to the subsequent stage. And a phase comparator.

  A fixed voltage fixed to a predetermined voltage is applied to the fixed voltage supply terminal 14, and this voltage signal is output to the subsequent stage via the variable resistor 15. The switch 12 is provided in the subsequent stage of the variable resistor 15 and the PLL-IC 11, and one of the output from the fixed voltage supply terminal 14 and the output from the PLL-IC 11 is supplied to the loop filter 13. Is done. The output from the loop filter 13 is input to the OCXO 20 as a control signal. The OCXO 20 outputs an internal reference signal having a frequency corresponding to the control signal to the subsequent stage, and this output is fed back to the PLL-IC 11. That is, the PLL-IC 11, the loop filter 13, and the OCXO 20 constitute a PLL (Phase Locked Loup).

  The frequency synthesizer 1 includes a detection circuit 16 including a diode, and the external reference signal is input to the control circuit 4 of the frequency synthesizer 1 through the detection circuit 16. The detection circuit 16 detects the external reference signal, and the control circuit 4 detects the amplitude of the detected signal and determines whether or not the amplitude is within a preset allowable range.

  Switching of the switch 12 is controlled by the control circuit 4. When it is determined that the detected amplitude is within the allowable range, the PLL-IC 11 is connected to the loop filter 13 by the switch 12. When it is determined that the amplitude is out of the allowable range, the fixed voltage supply terminal 14 is connected to the loop filter 13 by the switch 12. That is, the fixed voltage supply terminal 14 is used as a spare signal source for operating the OCXO 20 when the external reference signal is abnormal or a trouble has occurred such that the external reference signal is not supplied to the frequency synthesizer 1.

  At the subsequent stage of the OCXO 20, a PLL-IC 51, a loop filter 52, a VCO (Voltage Controlled Oscillator) 53, and an amplifier (AMP) 54 are connected in this order. The output of the AMP 34 is supplied as the output of the frequency synthesizer 1 to the host device described in the section of the background art, and the host device is operated.

  The output of the VCO 53 is fed back to the PLL-IC 51. The PLL-IC 51 is configured in the same manner as the PLL-IC 11 and synchronizes the internal reference signal supplied from the OCXO 20 with the frequency signal output from the VCO 53, and outputs the set frequency signal to the subsequent stage. That is, the PLL is configured by the PLL-IC 51, the loop filter 52, and the VCO 53.

  The control circuit 4 sends various data such as a frequency division ratio so that the frequency output from the PLL-ICs 11 and 51 becomes a desired value. Also, in the phase comparator of the PLL-IC 11, the external reference signal and the divided signal from the OCXO 20 are compared, and these signals are synchronized, that is, whether the PLL configured by the PLL-IC 11 is locked. A signal indicating whether or not is transmitted to the control circuit 4. Similarly, in the phase comparator of the PLL-IC 51, the internal reference signal and the signal from the divided VCO 53 are compared, and a signal indicating whether or not the PLL configured by the PLL-IC 51 is locked is a control circuit 4. Sent to. As a result, the control circuit 4 sends information about whether or not each PLL is locked to the host device.

  The stability of the output frequency of the frequency synthesizer 1 is determined by the stability of the signal with which the frequency synthesizer 1 is synchronized. That is, when an external reference signal is input as described above, the frequency synthesizer 1 operates in accordance with the stability of the external reference signal because it is synchronized with the external reference signal. In this way, the output frequency from the frequency synthesizer 1 is more stable when operated by the external reference signal than when operated by the fixed voltage.

  The OCXO 20 that is an internal reference oscillator corresponds to an oscillator with a thermostatic chamber that includes the oscillation circuit 2 and the heater circuit unit 3 for heating the crystal resonator of the oscillation circuit 2 to a set temperature. As shown in FIG. 2, the oscillation circuit 2 includes, for example, a Colpitts circuit and a crystal resonator 21. Reference numeral 22 denotes a transistor constituting an amplifying unit, 23 denotes a buffer amplifier, and VD denotes a variable capacitor. The control voltage supplied to the control voltage terminal 24 adjusts the capacitance of the variable capacitor VD to control the oscillation frequency. A power supply voltage supply terminal 25 supplies DC power to the oscillation circuit 2.

  The heater circuit section 3 is described in brief in FIG. The heater circuit unit 3 includes a thermistor 31 that constitutes a temperature sensor for detecting the temperature of the atmosphere in which the crystal resonator 21 is placed. The oscillation circuit 2 and the heater circuit unit 3 are housed in the common thermostat (container), and the atmosphere in the thermostat is maintained at a temperature higher than the environmental temperature in which the OCXO 20 is disposed. Yes. Immediately after the power supply of the frequency synthesizer 1 is turned on and a voltage is supplied from the power supply voltage supply terminal 25 to the heater circuit unit 3, the ambient temperature is, for example, room temperature, and the resistance value of the thermistor 31 is high. The voltage at the negative terminal is low, and the output voltage of the differential amplifier 32 is large. Therefore, a large current flows through the transistors 33 and 34, and the transistors 33 and 34 generate heat.

  Due to this heat generation, the ambient temperature in the thermostat rises, the resistance value of the thermistor 31 decreases, and the voltage at the negative input terminal of the differential amplifier 32 rises. As a result, the current flowing through the transistors 33 and 34 decreases, the temperature rise and the decrease in the current are in an equilibrium state, and the ambient temperature converges to the set temperature. This set temperature can be determined by circuit constants.

  The value of the collector current of the transistor 33 is detected by the determination unit 35. As shown in FIG. 3, the determination unit 35 determines whether or not the current detection value is equal to or smaller than a preset threshold value. If it is determined that the current detection value is greater than the threshold value, the heater circuit unit 3 increases the temperature. For example, a logic signal having a logic level of “L” (which may be referred to as an oven alarm signal) is output to notify that it is determined to be in the middle. On the other hand, when it is determined that the detected current value is equal to or less than the threshold value, it is determined that the heat generation of the heater circuit unit 3 is stable, that is, the temperature in the thermostatic chamber is stable and the temperature increase is completed. For example, a logic signal having a logic level of “H” (which may be described as an oven alarm release signal) is output. These logic signals “L” and “H” are input to the control circuit 4.

  As described in the background art section, the timing at which the oven alarm release signal is output may be different from the timing at which the output from the oscillation circuit 2 is stabilized. Specifically, the timing at which the output from the oscillation circuit 2 is stabilized means, for example, that the frequency deviation (frequency f0 at the set temperature−actual frequency f) / frequency f0 at the set temperature is −0.1 ppm to +0.1 ppm, and thereafter The timing varies within the range of −0.1 ppm to +0.1 ppm. In other words, it is the timing when the fluctuation of the frequency deviation converges within the range of −0.1 ppm to +0.1 ppm.

  As shown in FIG. 1, a temperature sensor 41 is provided in the frequency synthesizer 1 separately from the thermistor 31 that is a temperature sensor. The temperature sensor 41 has a role of detecting the temperature of the atmosphere in which the OCXO 20 is provided. For example, the temperature sensor 41 is disposed outside the thermostat and in the vicinity of the thermostat. The temperature sensor 41 is configured by, for example, a temperature detection IC or a thermistor, and is configured to output a temperature detection signal corresponding to the detected temperature to the control circuit 4.

  The control circuit 4 outputs a status signal indicating whether or not the oscillation output of the OCXO 20 is stabilized to the host device. The control circuit 4 receives the oven alarm cancel signal “H” from the OCXO 20 and then outputs an unstable output signal indicating that the oscillation output is not stable when an offset time (delay time) determined as described later has elapsed. Are switched to an output stability status signal indicating that the oscillation output is stabilized and output.

  The memory provided in the control circuit 4 stores a table set for the correspondence between the temperature detected by the temperature sensor 41 when the power is turned on and the offset time. By the way, an external reference signal or a fixed voltage signal is used as an input signal to the frequency synthesizer 1 as described above, but an appropriate offset time varies depending on which input signal is used as shown in an experiment described later. . Therefore, the table is provided for each input signal. Assume that a table used when an external reference signal is input is 42, and a table used when a fixed voltage signal is input is 43.

  The upper part of FIG. 4 shows an example of the table 42. When the temperature detected by the temperature sensor 41 is −20 ° C., 25 ° C., and 60 ° C., the offset time is set to 0 seconds, 9 seconds, and 15 seconds, respectively. Here, the offset time is set based on the test result of the evaluation test described later. When the detected temperature is between −20 ° C. and 25 ° C. and between 25 ° C. and 60 ° C., for example, there is a proportional relationship between the detected temperature and the offset time in each of these temperature ranges, The offset time is determined based on the detected temperature and the proportional relationship. In other words, the offset time corresponding to the detected temperature is read and determined from the solid line graph in the lower part of FIG. In this graph, the horizontal axis and the vertical axis are set as the detected temperature (unit: ° C.) and the offset time (unit: second), respectively.

  In the table 43, for example, when the detected temperature is −20 ° C. and 60 ° C., the offset time is set to 0 seconds and 45 seconds. When the detected temperature is between −20 ° C. and 60 ° C., as in the case of using the table 42, for example, it is assumed that there is a proportional relationship between the detected temperature and the offset time in these temperature ranges. The offset time is determined based on the temperature and the proportional relationship. That is, the offset time corresponding to the detected temperature is read and determined from the chain line graph in the lower part of FIG. The correspondence relationship between the detected temperatures of the tables 42 and 43 and the offset time is determined, for example, for each individual frequency synthesizer 1 by performing an experiment in advance according to the characteristics of the frequency synthesizer 1.

  Next, an operation when the frequency synthesizer 1 is turned on will be described. First, when the user of the frequency synthesizer 1 turns on the power of the synthesizer 1, it is determined in the OCXO 20 whether or not the collector current of the transistor 33 of the heater circuit unit 3 is equal to or less than a threshold value. Here, the atmosphere in which the oscillation circuit 2 is placed is room temperature, and the set temperature is higher than the room temperature. That is, it is determined that the collector current is higher than a threshold value. Then, the OCXO 20 outputs to the control circuit 4 an oven alarm signal (logic signal “L”) indicating that it has been determined that the temperature in the thermostatic chamber is rising toward the set temperature.

  In parallel with the reception of the logic signal, the control circuit 4 detects the temperature of the atmosphere in which the OCXO 20 is provided based on the output of the temperature sensor 41. Further, in parallel with this detection operation, it is determined whether or not the amplitude of the external reference signal input via the detection circuit 16 is within an allowable range. Here, it is assumed that the amplitude is determined to be within an allowable range.

  The control circuit 4 operates the switch 12 so as to connect the PLL-IC 11 and the loop filter 13, and an external reference signal is input to the OCXO 20 via the PLL-IC 11 and the loop filter 13, so that the OCXO 20 oscillates. The output of the OCXO 20 is input to the VCO 53 via the PLL-IC 51 and the loop filter 52, and the VCO 53 also oscillates. The oscillation output is amplified by the AMP 54 and output to the host device. In parallel with the output, the control circuit 4 determines the offset time based on the temperature detected by the temperature sensor 41 and the table 42. Further, an output unstable status signal indicating that the frequency synthesizer 1 is not stable is output to the host device.

  Each PLL including the OCXO 20 and the VCO 53 is locked, and a signal indicating that the PLL is locked is output from the control circuit 4 to the host device. Further, when the temperature in the thermostatic chamber of the OCXO 20 increases and approaches the set temperature, the collector current of the transistor 33 starts to decrease. When the collector current becomes equal to or less than the threshold value (t in FIG. 3), it is determined in OCXO 20 that the temperature increase in the thermostatic chamber has been completed, and the oven alarm cancel signal (logic signal “ H ") is output.

  The control circuit 4 waits for the determined offset time after receiving the oven alarm release signal. During this waiting time, the output from the OCXO 20 is stabilized, whereby the output from the frequency synthesizer 1 to the host device is also stabilized. When the offset time has elapsed after receiving the oven alarm signal, the control circuit 4 assumes that the frequency synthesizer 1 has stabilized, and outputs an output stable status signal instead of the output unstable status signal. By receiving this output stability status signal, the host apparatus starts its operation using the output from the frequency synthesizer 1. Note that when this status signal is output, for example, a host device that is already turned on may be configured to automatically operate so as to use the frequency of the synthesizer 1. When it is output, the host device may be turned on to start operation of the host device. In addition, when the status signal is output, the user may turn on the power of the host device.

  The difference between the case where the amplitude of the detected external reference signal is determined to be outside the allowable range and the case where the amplitude is determined to be within the allowable range will be mainly described. Thus, when it is determined that the value is outside the allowable range, the control circuit 4 operates the switch 12 so that the fixed voltage supply terminal 14 and the loop filter 13 are connected. The fixed voltage signal is supplied to the OCXO 20 via the loop filter 13 and the OCXO 20 oscillates, and thereby the VCO 53 also oscillates. The control circuit 4 determines the offset time based on the temperature detected by the temperature sensor 41 and the table 43. Thereafter, as in the case where the external reference signal is input, when the offset time has elapsed since the oven alarm cancellation signal was output, the output stability status signal is output.

  According to the frequency synthesizer 1, after the power is turned on, the heater circuit unit 3 outputs an oven alarm release signal indicating that the temperature of the atmosphere in the thermostatic chamber of the OCXO 20 has reached the set temperature, After the offset time determined based on the temperature of the atmosphere around the OCXO 20 detected by the temperature sensor 41 at the time of input and the table 42 or 43 has elapsed, the control circuit 4 outputs the output frequency of the frequency synthesizer 1 to the host device. Outputs a stable output status signal indicating that is stable. Therefore, it is possible to suppress a time lag until the output stability status signal is output after the output frequency of the OCXO 20 and thus the output frequency of the frequency synthesizer 1 are actually stabilized. Accordingly, it is possible to suppress the operation of the host device that uses the output of the frequency synthesizer 1 from becoming unstable, and to increase the operation efficiency of the host device. Furthermore, since the data of the appropriate table among the tables 42 and 43 is used according to the input signal input to the frequency synthesizer 1 for operating the OCXO 20, the time lag can be more reliably suppressed. .

  For example, the frequency deviation is converged to a range of −0.1 ppm to +0.1 ppm, and the value of the frequency deviation varies depending on performance required for the apparatus. For example, the offset time may be set on the assumption that the frequency is stable when the frequency deviation converges to a range of -1 ppm to +1 ppm or when the frequency deviation converges to a range of -0.01 ppm to +0.01 ppm. Further, since the temperature of the atmosphere in which the OCXO 20 is provided changes due to the heat generated by the OCXO 20, the temperature of the atmosphere is detected by the temperature sensor 41 when the power is turned on. However, depending on the performance of the heater circuit unit 3, it may take a long time for the temperature to rise after the power is turned on. That is, the time when the power is turned on does not indicate only the moment when the power is turned on, but also includes a period during which the temperature detected by the temperature sensor 41 does not change substantially from that moment. For example, immediately after the power is turned on, a period from when the temperature detection value by the temperature sensor 41 is increased by 1 ° C. immediately after the power is turned on is also included when the power is turned on.

  By the way, since the frequency characteristic with respect to the temperature of the OCXO 20 depends on the frequency characteristic with respect to the temperature of the crystal unit 21, the temperature detected by the temperature sensor to determine the offset time is the temperature of the atmosphere closer to the crystal unit 21. Preferably there is. That is, in the above example, when the power is turned on, the inside and outside of the thermostatic bath are assumed to have the same temperature, and the temperature outside the thermostatic bath is detected by the temperature sensor 41. You may make it detect in the inside of a thermostat and detect the temperature inside a thermostat. Accordingly, it is possible to suppress a deviation between the timing at which the output stability status signal is output more reliably and the timing at which the output frequency is actually stabilized. Further, the thermistor 31 of the heater circuit unit 3 may have the role of the temperature sensor 41. That is, for example, based on the collector current of the transistor 33 when the power is turned on, the control circuit 4 may detect the temperature in the thermostatic chamber.

  In the above example, whether or not the external reference signal is abnormal is determined by detecting the amplitude, and the switch 12 is switched. However, the configuration is not limited thereto. For example, the voltage of the external reference signal may be detected, the presence or absence of an abnormality may be determined based on the detected voltage, and the switch 12 may be switched.

(Evaluation Test 1)
Here, the evaluation test that has resulted in the knowledge of the present invention will be described. In this evaluation test, a test frequency synthesizer was used. In the test frequency synthesizer, the tables 42 and 43 and the temperature sensor 41 are not provided. When the oven alarm release signal is output from the OCXO 20, the control circuit 4 promptly outputs a status signal assuming that the oscillation frequency of the frequency synthesizer 1 is stable. Except for such differences, the test frequency synthesizer is configured in the same manner as the frequency synthesizer 1.

  As evaluation test 1-1, a test frequency synthesizer was installed in an atmosphere of −20 ° C., and the power was turned on. Then, the time from when the power was turned on until the oven alarm release signal was output (the oven alarm release time) was measured. Further, the frequency deviation was monitored, and the time until the frequency deviation became −0.1 ppm to +0.1 ppm after the power was turned on was measured. As evaluation test 1-2, a test was performed in the same manner as evaluation test 1-1 except that a test frequency synthesizer was installed in an atmosphere of 25 ° C. As evaluation test 1-3, a test was performed in the same manner as evaluation test 1-1 except that a test frequency synthesizer was installed in an atmosphere of 60 ° C. In these evaluation tests 1-1 to 1-3, the test frequency synthesizer was synchronized with the external reference signal.

  FIG. 5 is a graph showing the relationship between the monitored frequency deviation (unit: ppm) and the elapsed time since the power was turned on (unit: seconds). The horizontal axis and the vertical axis show the elapsed time and frequency deviation, respectively. Each is set. The results of evaluation tests 1-1, 1-2, and 1-3 are shown by chain lines, dotted lines, and solid lines, respectively. In all of the evaluation tests 1-1 to 1-3, as shown in the graph, the oscillation frequency is stable as time elapses.

  FIG. 6 shows an enlarged range in which the frequency deviation is −1.0 ppm to +1.0 ppm in the graph of FIG. 5. In the graph of FIG. 6, the time point when the oven alarm cancel signal is output is indicated by a white circle. In addition, the time points when the frequency deviation converges to −0.1 ppm to +0.1 ppm are indicated by black circle plots. In the evaluation tests 1-1, 1-2, and 1-3, the oven alarm release time is 170 seconds, 75 seconds, and 23 seconds, respectively, and the frequency deviation when the oven alarm release signal is output is 0.04 ppm, respectively. -0.01 ppm and -0.09 ppm. In evaluation tests 1-1, 1-2, and 1-3, the time from when the power is turned on until the frequency deviation converges to −0.1 ppm to +0.1 ppm (convergence time) is 161 seconds and 84 seconds, respectively. It was 38 seconds.

  Therefore, in the evaluation tests 1-1, 1-2, and 1-3, the convergence time-oven alarm release time is calculated to be -9 seconds, 9 seconds, and 15 seconds, respectively. That is, the amount corresponding to this time difference is set as an offset from the output of the oven alarm release signal, and the timing at which the output stability status signal is output is controlled to stabilize the output frequency of the frequency synthesizer 1, A time lag until the output stable status signal is output can be suppressed.

  The offset time of the table 42 of the frequency synthesizer 1 is set based on the evaluation tests 1-1 to 1-3. In evaluation test 1-3, the time difference between the convergence time and the oven alarm release time is −9 seconds, but the control circuit 4 receives the oven alarm release signal from the OCXO 20 and then outputs the status signal. In 42, the offset time when the temperature detected by the temperature sensor 41 is −20 ° C. is set to 0 second. However, in order to operate the host device in a more stable frequency state, when the offset time is determined by performing an experiment in this way, a time slightly longer than the convergence time-oven alarm release time is set as the offset time. It is also effective to do.

(Evaluation test 2)
As the evaluation test 2-1, the frequency synthesizer for the above test was installed in an atmosphere of 60 ° C., and the frequency deviation after power-on was monitored. In this evaluation test 2-1, the frequency synthesizer was synchronized with an external reference signal. Also, evaluation test 2-2 was performed using a fixed voltage signal instead of using an external reference signal. In this evaluation test 2-2, an experiment was performed under the same conditions as in the evaluation test 2-1, except that the input signal was different.

  FIG. 7 is a graph showing the results of the evaluation tests 2-1 and 2-2. Like the graphs of FIGS. 5 and 6, the horizontal axis represents the elapsed time since power-on, and the vertical axis represents the frequency deviation. It is set. The result of the evaluation test 2-1 is indicated by a dotted line graph, and the result of the evaluation test 2-2 is indicated by a solid line graph. The variable range of the frequency of the OCXO 20 is, for example, −2 ppm to +2 ppm, and it can be seen from the graph that in the evaluation test 2-1, the OCXO 20 can be synchronized with the external reference signal immediately after the power is turned on. And in the evaluation test 2-1, there is no overshoot and the time required for the frequency to stabilize is shorter than the evaluation test 2-2. From these evaluation tests 2-1 and 2-2, it is effective to select one of the tables 42 and 43 and determine the offset time according to whether or not the external reference signal is supplied as in the frequency synthesizer 1 described above. I understand that there is.

  Next, the frequency synthesizer 6 will be described with reference to FIG. This frequency synthesizer 6 includes n (n is an integer) signal generators 60. Each signal generation unit 60 is configured in the same manner, and includes a PLL-IC 61, a filter 62, a VCO 63, an attenuator 64, an amplifier 65, and a filter 66 connected in this order. In FIG. 8, in order to distinguish the signal generation units 60 from each other, the numbers of the signal generation units 60 are denoted by reference numerals 1 to n for the sake of convenience, and are indicated as signal generation units 601, 602... 60 n. . Similarly, each of the above-described units constituting the signal generation units 601 to 60n is denoted by the numerals 1 to n attached to the signal generation unit after the numerals 61 to 66, and the signal generation units 601 and 602 are indicated. ... indicating which of 60n is configured.

  The output of the VCO 63 is fed back to the PLL-IC 61. Thereby, the PLL-IC 61, the filter 62, and the VCO 63 constitute a PLL. Each of the signal generators 601, 602,... 60n is configured to output frequencies in different bands, and the filters 661, 662,... 66n of these signal generators 601, 602,. 67. The output band selection unit 67 supplies any one output of the signal generation units 601, 602... 60 n to the output terminal 68. The frequency synthesizer 6 includes a control unit 71 and a power supply unit 72. The control unit 71 outputs data to each PLL-IC similarly to the control circuit 4. In addition, the output band selection unit 67 is controlled to determine which signal generation unit 60 is to output data. The power supply unit 72 supplies power to each unit of the frequency synthesizer 6.

  As shown in FIG. 9, the frequency synthesizer 6 is configured by arranging circuit components 73 that constitute the signal generation unit 60, the band selection unit 67, the control unit 71, and the power supply unit 72 described above on a substrate 74. . A case 75 is provided on the substrate 74, and the case 75 is configured by forming a plurality of recesses on the lower surface of the thick plate. The circuit component 73 is accommodated in the recess. In the case 75, one recess is formed as described above, and the side wall 81 that surrounds the side periphery of the circuit component 73 and the upper wall 82 that covers the upper side of the circuit component 73 are referred to as a shield block 7. That is, a plurality of shield blocks 7 are formed in the case 75, and each circuit component 73 is partitioned by each shield block 7.

  For example, FIG. 8 shows the components of the frequency synthesizer 6 included in one shield block 7 with one dotted frame. In this example, the signal generators 60 are housed in different shield blocks 7. In the signal generation unit 60, the PLL-IC 61, the filter 62, and the VCO 63 are accommodated in one shield block 7, and the attenuator 64, the amplifier 65, and the filter 66 are accommodated in the other shield block 7. The control unit 71, the power supply unit 72, and the output band selection unit 67 are housed in shield blocks 7 that are independent from each other.

  A conductive gasket 83 is provided along the side wall 81 between the substrate 74 and the side wall 81. By storing each circuit component 73 in the shield block 7, the noise of the circuit component 73 stored in one shield block 7 affects the circuit component 73 stored in another shield block 7, and spurious is generated. It can be prevented from occurring. Furthermore, by providing the gasket 83, it is possible to more reliably suppress the influence of such noise on the other blocks 7. Even in the case where the contact between the substrate 74 and the case 75 is low due to the structure of the case 75 and the sealing performance of the circuit component 73 is low, the sealing performance can be increased by providing the gasket 83 in this way. Further, as the gasket 83, a gasket having a relatively high thermal conductivity may be used to improve the heat dissipation within the shield block 7. In the figure, 84 is a hole provided in the lower end portion of the side wall 81 and is used for screwing the case 75 to the substrate 74.

  By providing the shield block 7 and partitioning each circuit component 73, it is possible to suppress unnecessary noise generated in each shield block 7 from being coupled to signals of other blocks 7. In particular, as described in JP 2007-267375 A, when noise is applied to a control terminal to which a control voltage is applied in an oscillation device, spurious is likely to occur, but such application of noise is suppressed. As a result, it is possible to suppress the generation of unnecessary waves in each signal generator 60. As a result, the output frequency from the frequency synthesizer 6 is stabilized.

  FIG. 10 shows another example of the shield block 7, and a step is provided at the lower end portion of the side wall 81 of the shield block 7. Due to this step, the side wall 81 is formed with a low wall 81A and a high wall 81B. The hole 84 is provided in the high wall 81B, and the gasket 83 is provided in the low wall 81A. When the shield block 7 is attached to the substrate 74, the gasket 83 is crushed by the substrate 74, the high wall 81B can contact the substrate 74, and the high wall 81B can be screwed as described above. That is, by providing a step on the side wall 81, the side wall 81 can be prevented from being lifted from the substrate 74 due to the thickness of the gasket 83.

  The shield block 7 can be applied to other oscillation devices. For example, the present invention may be applied to the frequency synthesizer 1 described above. Specifically, for example, the OCXO 20 and the VCO 53 can be housed in separate shield blocks 7 to prevent the outputs from interfering with each other. Further, the shield block 7 may be applied to the oscillation device disclosed in Japanese Patent Laid-Open No. 2007-267375.

1 Frequency synthesizer 2 Oscillator circuit 20 OCXO
21 Crystal oscillator 3 Heater circuit section 14 Fixed voltage supply terminal 4 Control circuit 41 Temperature sensors 42 and 43 Table

Claims (3)

An oscillation circuit using a piezoelectric vibrator;
A heater for maintaining the temperature of the atmosphere in which the piezoelectric vibrator is provided at a set temperature;
A temperature sensor that detects the temperature of the atmosphere and outputs a signal corresponding to the detected temperature;
After turning on the power, after receiving a first detection signal indicating that the temperature of the atmosphere has reached the set temperature by the heater from the temperature sensor, it is confirmed that the oscillation frequency output from the oscillation circuit has become stable. A control circuit for informing,
Regarding the correspondence between the second detection signal output from the temperature sensor to the control circuit when the power is turned on and the delay time from when the control circuit receives the first detection signal until the notification is performed, A storage unit that stores the control circuit so that the notification can be performed based on the correspondence;
An oscillation device comprising: A control signal output to the oscillation circuit,
A signal supplied from a signal output unit provided in the oscillation device so as to output a signal based on an external signal supplied to the oscillation device from the outside of the oscillation device, and a signal supplied from the signal output unit A switching unit for switching between a spare signal for replacement of
A detection unit for detecting the presence or absence of abnormality by detecting the external signal ;
With
The oscillation device according to claim 1, wherein the control circuit controls an operation of the switching unit according to a detection result of the detection unit. The correspondence relationship is
Including a first correspondence relationship and a second correspondence relationship in which the correspondence between the second detection signal and the delay time is different from each other ;
The control circuit outputs the notification signal based on the first correspondence when the reference signal is supplied to the oscillation circuit, and the second signal when the preliminary signal is supplied to the oscillation circuit. The oscillation device according to claim 2, wherein the notification signal is output based on the correspondence relationship.

Images