JP5633866B2 - Reference signal generating apparatus and reference signal generating method - Google Patents

Description

  The present invention relates to a reference signal generating apparatus and a reference signal generating method for generating a reference signal that is a reference for timing of signals transmitted and received by a communication apparatus.

  In general, a reference signal generation device that generates a reference signal that is a reference of timing of a signal transmitted and received by a communication device such as a wireless base station is synchronized with a GPS (Global Positioning System) satellite. A 1 pps signal is extracted from the signal, and this synchronization signal is synchronized with a crystal oscillator to generate a highly stable reference signal.

  Further, in order to secure holdover characteristics when a synchronization signal transmitted from a GPS satellite cannot be received (to maintain the stability of the frequency of the reference signal even when the synchronization signal cannot be received), OCXO (Oven Control Crystal Oscillator as a crystal oscillator). : A temperature controlled crystal oscillator) is considered (for example, see Patent Document 1).

  FIG. 11 is a diagram showing an example of an internal configuration of a general reference signal generator using OCXO as a crystal oscillator.

  11 includes a GPS module 1100, an OCXO 1200, a CPU 1301, a temperature sensor 1320, a heater 1330, a control unit 1340, a D / A converter 1500, and a counter 1600. It has been.

  The GPS module 1100 receives a synchronization signal transmitted from a GPS satellite and extracts a 1 pps signal from the synchronization signal. In addition, the GPS module 1100 outputs the extracted 1 pps signal to the CPU 1310.

  CPU 1301 outputs predetermined data based on the 1 pps signal output from GPS module 1100 to D / A converter 1500.

  The D / A converter 1500 converts the data output from the CPU 1301 from a digital signal to an analog signal and outputs the converted signal to the OCXO 1200.

  The OCXO 1200 includes an XTAL 1201 that is a crystal oscillator.

  The XTAL 1201 generates a reference signal using the signal output from the D / A converter 1500 and outputs the reference signal to the counter 1600.

  The temperature sensor 1320 measures the temperature inside the OCXO 1200. Further, the temperature sensor 1320 notifies the control unit 1340 of the measured temperature.

  Control unit 1340 instructs heater 1330 to a predetermined temperature based on the temperature notified from temperature sensor 1320.

  The heater 1330 keeps the temperature inside the OCXO 1200 at a temperature instructed by the control unit 1340.

  The temperature sensor 1320 and the heater 1330 may be included in the OCXO 1200.

  The counter 1600 generates a frequency-divided signal based on the reference signal output from the OCXO 1200 and outputs it to the CPU 1301 and the outside.

JP 2002-217713 A

  In the reference signal generator as described above, the internal temperature is maintained at a high temperature of about 90 ° C. so that the accuracy of the reference signal generated by the crystal oscillator is not affected by the external environment.

  Therefore, there is a problem that electric power for keeping the crystal oscillator at such a high temperature is required, and the power consumption of the entire reference signal generating device is increased.

  An object of the present invention is to provide a reference signal generation apparatus and a reference signal generation method that solve the above-described problems.

The reference signal generator of the present invention is
A reference signal generator for generating a reference signal that is a reference for processing timing,
A GPS module for receiving a synchronization signal transmitted from a GPS satellite;
While the GPS module is receiving the synchronization signal, the reference signal is generated using the synchronization signal, and while the GPS module is not receiving the synchronization signal, a preset value is used. An oscillator for generating the reference signal;
While the GPS module is receiving the synchronization signal, the temperature of the oscillator is changed at a temperature higher than a predetermined temperature by a preset temperature, and while the GPS module is not receiving the synchronization signal. And a temperature control unit for fixing the temperature of the oscillator to a temperature at which the GPS module stops receiving the synchronization signal.

Further, the reference signal generation method of the present invention includes:
A reference signal generation method for generating a reference signal that is a reference for processing timing,
A process of receiving a synchronization signal transmitted from a GPS satellite;
Generating the reference signal from an oscillator using the synchronization signal while receiving the synchronization signal;
While not receiving the synchronization signal, processing to generate the reference signal from the oscillator using a preset value;
A process of changing the temperature of the oscillator at a temperature higher than a predetermined temperature by a preset temperature while receiving the synchronization signal;
While the synchronization signal is not received, the temperature of the oscillator is fixed to the temperature when the synchronization signal is not received.

  As described above, in the present invention, the power consumption of the entire reference signal generator can be reduced.

It is a figure which shows one Embodiment of the reference signal generator of this invention. In the reference signal generator shown in FIG. 1, an example of processing from when a GPS module receives a synchronization signal until a value for controlling a frequency is stored in a D / A converter table is described. It is a flowchart. It is a figure which shows an example of the mode of a change of time and a frequency about a time-dependent change of a crystal oscillator. It is a figure which shows the concept of the determination method of the temperature in OCXO in this invention. 2 is a flowchart for explaining processing for determining whether or not holdover is performed in the reference signal generator shown in FIG. 1. It is a flowchart for demonstrating the detail of the process of step S16 shown to the flowchart of FIG. It is a figure which shows the relationship between the temperature difference of the preset temperature of OCXO and ambient temperature, and power consumption. It is a graph which shows an example of transition of power consumption through the year. It is a figure which shows the other form of implementation of the reference signal generator of this invention. It is a figure which shows an example of the internal structure of CPU shown in FIG. It is a figure which shows an example of the internal structure of the common reference signal generator in which OCXO was used as a crystal oscillator.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a reference signal generator according to the present invention.

  As shown in FIG. 1, the reference signal generator 100 in this embodiment includes a GPS module 110, an OCXO 120, a temperature controller 130, a thermometer 140, a D / A converter 150, and a counter 160. Yes.

  The GPS module 110 receives a synchronization signal transmitted from a GPS satellite. Further, the GPS module 110 extracts a 1 pps signal from the received synchronization signal. In addition, the GPS module 1100 outputs the extracted 1 pps signal to the temperature control unit 130.

  The OCXO 120 generates a reference signal using the received synchronization signal while the GPS module 110 receives the synchronization signal, and uses a preset value while the GPS module 110 does not receive the synchronization signal. And an oscillator for generating a reference signal. This reference signal is a signal serving as a reference for processing timing in a communication apparatus such as a radio base station.

  The OCXO 120 is composed of an XTAL 121 that is a crystal oscillator.

  The thermometer 140 measures the temperature outside the reference signal generator 100.

  While the GPS module 110 receives the synchronization signal, the temperature control unit 130 changes the temperature of the OCXO 120 at a temperature higher than the predetermined temperature by a preset temperature. Further, the temperature control unit 130 fixes the temperature of the OCXO 120 to the temperature when the GPS module 110 stops receiving the synchronization signal while the GPS module 110 does not receive the synchronization signal.

  Further, the temperature control unit 130 changes the temperature of the OCXO 120 at a temperature higher than the temperature measured by the thermometer 140 by a preset temperature.

  Further, the temperature control unit 130 changes the temperature of the OCXO 120 at a temperature higher by a preset temperature than the highest temperature among the temperatures measured by the thermometer 140 for a predetermined period.

  The temperature control unit 130 includes a CPU 131, a temperature sensor 132 that measures the temperature inside the OCXO 120, and a heater 133 that sets (maintains) the temperature inside the OCXO 120 at a predetermined temperature. The operation described above is performed. Further, the CPU 131 outputs predetermined data based on the 1 pps signal output from the GPS module 110 to the D / A converter 150.

  The D / A converter 150 converts the data output from the CPU 131 from a digital signal to an analog signal and outputs the converted signal to the OCXO 120.

  The counter 160 generates a frequency-divided signal based on the reference signal output from the OCXO 120 and outputs it to the CPU 131 and the outside.

  Hereinafter, the operation of the reference signal generator 100 shown in FIG. 1 will be described.

  FIG. 2 shows a process from the time when the GPS module 110 receives the synchronization signal until the value for controlling the frequency is stored in the table of the D / A converter 150 in the reference signal generator 100 shown in FIG. It is a flowchart for demonstrating an example.

  First, when a synchronization signal transmitted from a GPS satellite is received by the GPS module 110, a signal synchronized with 1 second of a 1 pps signal (UTC (Universal Time, Coordinated)) from the received synchronization signal. , Hereinafter referred to as a 1 pps signal) is extracted (step S1).

  Then, the 1 pps signal extracted by the GPS module 110 is output from the GPS module 110 to the CPU 131. Here, the synchronization signal transmitted from the GPS satellite is a highly accurate time signal in the long term, but has a short-term fluctuation. Therefore, the OCXO 120 is controlled so as to synchronize with the 1 pps signal extracted by the GPS module 110, and the signal output from the OCXO 120 is divided by using the counter 160 to obtain a 1-second cycle. The standard is 1 pps used in the communication device. As a result, a highly accurate reference signal can always be obtained.

  Then, the CPU 131 compares the 1 pps signal output from the GPS module 110 with the signal obtained by dividing the output signal of the OCXO 120 (with a frequency of 10 MHz) by 1 / 10,000,000 by the counter 160 (step S2). The oscillation frequency of the OCXO 120 is controlled and synchronized. That is, a PLL (Phase Locked Loop) having a comparison frequency of 1 Hz is formed and is very low speed, so that it can be realized by arithmetic control of the CPU without using hardware logic. Here, since the comparison frequency is very low at 1 Hz, the PLL loop band is on the order of mHz.

  A loop filter is configured by the calculation in the CPU 131, and the calculated digital value is converted into an analog signal by the D / A converter 150 and input to the frequency control terminal of the OCXO 120 to control the frequency (step S3).

  This change with time can be understood by changing the control value of the OCXO 120, that is, the set value of the D / A converter 150. Therefore, when the GPS module 110 cannot receive the synchronization signal transmitted from the GPS satellite (at the time of holdover), it is stored in a table for use in estimating the set value of the D / A converter 150 (steps S4 and S5). .

  In addition, it is necessary to match the phase of the 1 pps signal output from the counter 160 with the phase of the 1 pps signal output from the GPS module 110. This is because the preset value is set to the counter 160 from the CPU 131 at the time of startup. Is implemented.

  When the GPS module 110 cannot receive the synchronization signal transmitted from the GPS satellite, the hold mode is set, and the OCXO 120 is not controlled by the PLL, but a fixed value is sent from the CPU 131 to the D / A converter 150 to obtain the frequency. Is fixed.

  Moreover, although the temperature of the OCXO 120 is kept constant, the frequency changes with time.

  Therefore, the CPU 131 controls the output voltage output from the D / A converter 150 so as to compensate for the change with time.

  The control voltage is always acquired when the GPS satellite is captured, and if the synchronization signal transmitted from the GPS satellite cannot be received, the control voltage is estimated by an approximate expression from the data acquired in the past.

  FIG. 3 is a diagram illustrating an example of a change in time and frequency with respect to the change over time of the crystal oscillator.

  As shown in FIG. 3, the frequency moves greatly in the initial state, but the frequency change gradually decreases as time elapses. Further, the oscillation frequency of the XTAL 121 changes with temperature. Therefore, the influence of temperature cannot be ignored for the reference signal generator used for the radio base station.

  Here, since the frequency change due to the influence of the temperature of the XTAL 121 can be eliminated by keeping the temperature in the OCXO 120 constant, control is performed so that the temperature in the OCXO 120 is constant. The temperature at which the OCXO 120 is held is controlled by the CPU 131. Further, there is a temperature sensor 132 that measures the temperature in the immediate vicinity of the XTAL 121, and the measurement value measured by the temperature sensor 132 is notified to the CPU 131. Further, the heater 133 is raised so as to keep the internal temperature of the OCXO 120 constant. As described above, the CPU 131 controls the heater 133 based on the measured value of the temperature sensor 132 so as to reach a preset constant temperature.

  FIG. 4 is a diagram showing a concept of a method for determining the temperature in the OCXO 120 in the present invention.

  The thermometer 140 shown in FIG. 1 measures a long-term ambient temperature, that is, an air temperature. In particular, the outdoor temperature of an outdoor installation device changes greatly within a day, but the internal set temperature of the OCXO 120 is set higher by a predetermined temperature than the maximum ambient temperature of the day so as not to be affected by the ambient temperature. Keep it.

  As shown in FIG. 4, the moving average air temperature (shown by a broken line) of the ambient temperature is taken, and the internal set temperature of the OCXO 120 is set to 20 ° C. higher than this temperature. In order to take a long-term moving average of the ambient temperature, the change in the set temperature of the OCXO 120 is assumed to be very slow on a daily basis. In addition, this 20 degreeC can be suitably changed according to the use condition.

  Here, the CPU 131 performs ON / OFF control of the heater 133 so that the internal temperature in the OCXO 120 becomes constant at the set temperature. As indicated by the solid line in FIG. 4, the set temperature decreases as the ambient temperature decreases depending on the season, so that power consumption can be reduced compared to a conventional apparatus that is always set to a high temperature of about 90 ° C. .

  Next, temperature control in the holdover state will be described.

  FIG. 5 is a flowchart for explaining processing for determining whether or not holdover is performed in reference signal generating apparatus 100 shown in FIG.

  First, a signal is received by the GPS module 110 (step S11), and it is determined by the CPU 131 whether or not a synchronization signal has been captured from the received signal (step S12). This determination may be based on whether or not the above-described 1 pps signal has been extracted.

  When it is determined that the synchronization signal has been captured, the temperature control unit 130 sets the temperature of the OCXO 120 to a set value (variable) corresponding to the ambient temperature measured by the thermometer 140 (step S13), and normal processing is performed. (Step S14). That is, the temperature control unit 130 changes the temperature of the OCXO 120 at a temperature that is higher than the ambient temperature by a preset temperature. In this normal process, the process described using the flowchart shown in FIG. 2 is performed.

  On the other hand, if it is determined in step S12 that the synchronization signal could not be captured, the holdover mode is set, and the temperature control unit 130 has set the OCXO 120 to a holdover (the synchronization signal is no longer received). (Time)) (step S15). Then, a holdover process is performed (step S16).

  FIG. 6 is a flowchart for explaining details of the process in step S16 shown in the flowchart of FIG.

  At the time of holdover, since the frequency synchronization of the OCXO 120 cannot be performed using the 1 pps signal taken out by the GPS module 110, the frequency stability is improved by eliminating the temperature change. Regarding the change with time, the OCXO 120 is controlled based on an approximate expression from data acquired in the past. Although the performance guarantee at the time of holdover is about 24 hours at the longest, the influence of temperature is eliminated, and the stability of frequency is maintained by controlling only the influence of change with time.

  Specifically, current temperature data is acquired (step S21), and the D / A table is read (step S22), so that a change with time is estimated (step S23). The estimated digital value is converted into an analog signal by the D / A converter 150 and input to the frequency control terminal of the OCXO 120 to control the frequency (step S24).

  As described above, in the present invention, power consumption can be reduced by controlling the temperature in the OCXO 120 in accordance with a change in ambient temperature.

  During normal operation, it is synchronized with a synchronization signal transmitted from a GPS satellite. On the other hand, at the time of holdover, the frequency stability can be improved by fixing the temperature in the OCXO 120.

  FIG. 7 is a diagram illustrating the relationship between the temperature difference between the set temperature of the OCXO 120 and the ambient temperature and the power consumption.

  As shown in FIG. 7, the power consumption tends to increase as the temperature difference increases.

  FIG. 8 is a graph showing an example of transition of power consumption throughout the year.

  In general technology, the temperature difference between the internal temperature of the OCXO and the ambient temperature is small in the summer when the ambient temperature is high, and the temperature difference between the internal temperature and the ambient temperature of the OCXO set at around 90 ° C. is large in the winter. Especially in winter, power consumption increases.

  On the other hand, in the present invention, the set temperature of the OCXO 120 is varied according to the ambient temperature throughout the summer and winter, and the difference between the set temperature of the OCXO 120 and the ambient temperature is kept substantially constant. Therefore, power consumption is almost constant throughout the year. As described above, the present invention has an effect of reducing the total annual power consumption.

  FIG. 9 is a diagram showing another embodiment of the reference signal generator of the present invention.

  As shown in FIG. 9, the reference signal generation device 200 in this embodiment includes a GPS module 110, OCXO 120, a temperature control unit 230, a D / A converter 150, and a counter 160.

  The GPS module 110, OCXO 120, D / A converter 150, and counter 160 are the same as those shown in FIG.

  The GPS module 110 acquires position information indicating the position of the reference signal generator 100 from a GPS satellite.

  The temperature control unit 230 changes the temperature of the OCXO 120 by a temperature that is higher by a preset temperature than the temperature corresponding to the position information acquired by the GPS module 110. At this time, the temperature control unit 230 may change the temperature of the OCXO 120 at a temperature that is higher by a preset temperature than the temperature corresponding to the latitude / longitude information in the position information acquired by the GPS module 110. good. At this time, the temperature control unit 230 changes the temperature of the OCXO 120 at a temperature higher by a preset temperature than the temperature corresponding to the altitude information in the position information acquired by the GPS module 110. Also good. These controls are performed by the CPU 231.

  That is, the CPU 231 reads out and uses the average temperature information for each region from the table based on the latitude / longitude information and the year / month information acquired by the GPS module 110. If the average temperature database for each region is set up in Japan, a very small region is not necessary, and a database in which the whole country is divided into about 10 blocks is practically sufficient. Further, the CPU 231 may perform altitude correction (0.6 ° C./100 m) based on the altitude information acquired by the GPS module 110 and calculate the average temperature.

  FIG. 10 is a diagram showing an example of the internal structure of the CPU 231 shown in FIG.

  As shown in FIG. 10, the CPU 231 shown in FIG. 9 is provided with a GPS information acquisition unit 232, a regional average temperature database 233, and an altitude correction unit 234.

  The GPS information acquisition unit 232 acquires information (latitude / longitude information, year / month information, altitude information, etc.) acquired by the GPS module 110.

  The regional average temperature database 233 is a database that stores in advance temperature information corresponding to latitude / longitude information and year / month information. The regional average temperature database 233 searches for the average temperature corresponding to the latitude and longitude information and year / month information acquired by the GPS information acquisition unit 232 as search keys. The regional average temperature database 233 outputs the searched average temperature to the altitude correction unit 234.

  The altitude correction unit 234 corrects the average temperature output from the regional average temperature database 233 based on the altitude information acquired by the GPS information acquisition unit 232. This correction method may acquire data of changes in temperature with respect to altitude in advance and correct based on the acquired data.

  Note that the processing performed by the components illustrated in FIG. 10 may be realized by hardware or may be realized by software (computer program).

  The present invention is particularly useful for applications requiring low power consumption, such as WCDMA (Wideband Code Multiple Access) and WIMAX (Worldwide Interoperability for Microwave Access) radio base stations.

100,200 Reference signal generator 110 GPS module 120 OCXO
130, 230 Temperature controller 131, 231 CPU
132 Temperature Sensor 133 Heater 140 Thermometer 150 D / A Converter 160 Counter 232 GPS Information Acquisition Unit 233 Regional Average Temperature Database 234 Altitude Correction Unit

Claims (4)

A reference signal generator for generating a reference signal that is a reference for processing timing,
A GPS module for receiving a synchronization signal transmitted from a GPS satellite;
While the GPS module is receiving the synchronization signal, the reference signal is generated using the synchronization signal, and while the GPS module is not receiving the synchronization signal, a preset value is used. OCXO for generating the reference signal;
While the GPS module is receiving the synchronization signal, the temperature of the OCXO is changed at a temperature higher than a predetermined temperature by a preset temperature, and while the GPS module is not receiving the synchronization signal. , have a temperature control unit for fixing the temperature of the OCXO to a temperature at which the GPS module stops receiving the synchronization signal,
The GPS module acquires position information of the reference signal generator from the GPS satellite;
The temperature control unit is a reference signal generating device that changes the temperature of the OCXO at a temperature higher than a temperature corresponding to the position information by a preset temperature . The reference signal generator according to claim 1 ,
The reference signal generator according to claim 1, wherein the temperature control unit changes the temperature of the OCXO at a temperature higher than a temperature corresponding to latitude / longitude information in the position information by a preset temperature. The reference signal generator according to claim 1 ,
The reference signal generator according to claim 1, wherein the temperature controller changes the temperature of the OCXO by a temperature that is higher than a temperature corresponding to altitude information in the position information by a preset temperature. A reference signal generation method for generating a reference signal that is a reference for processing timing,
A process of receiving a synchronization signal transmitted from a GPS satellite;
Generating the reference signal from the OCXO using the synchronization signal while receiving the synchronization signal;
A process of generating the reference signal from the OCXO using a preset value while the synchronization signal is not received;
A process of changing the temperature of the OCXO at a temperature higher than a predetermined temperature by a preset temperature while receiving the synchronization signal;
A process of fixing the temperature of the OCXO to the temperature when the synchronization signal is no longer received while not receiving the synchronization signal ;
Processing for obtaining position information of the device comprising the OCXO from the GPS satellite;
A reference signal generation method for performing a process of changing the temperature of the OCXO at a temperature higher than a temperature corresponding to the position information by a preset temperature .

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