JP2010263503A - Communication apparatus and clock correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication apparatus to be operated by using a highly precise clock signal without using a double oven type OCXO even during a period in which a GPS signal can not be normally received. <P>SOLUTION: A radio base station includes: a generation unit 13 for generating a clock signal CLK from an oscillation pulse signal Pxo generated by a crystal oscillator 11; an error correction part 15 for correcting the frequency error of the clock signal CLK by using a reference pulse signal Pref obtained from the GPS signal received by a GPS receiver 12; a temperature sensor 14 for measuring temperature; and a correction value memory 16 for storing an error correction value indicating the frequency error corrected by the error correction part 15 in association with temperature when the error correction part 15 makes correction. When the reference pulse signal Pref becomes unobtainable, the error correction part 15 acquires an error correction value corresponding to temperature measured by the temperature sensor 14 from a correction value memory 16 and corrects the frequency error using the acquired error correction value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a communication device using a GPS receiver and a clock correction method.

  A communication apparatus such as a radio base station has a clock signal generation apparatus that generates a clock signal for synchronizing operations. A crystal oscillator (XO) is generally used for such a clock signal generation device.

  The crystal oscillator has a characteristic (frequency temperature characteristic) in which the oscillation frequency changes when the temperature changes. For this reason, a communication device that requires a clock signal with a stable frequency is provided with a crystal oscillator with a thermostat (hereinafter referred to as OCXO). OCXO has a crystal oscillator housed in a thermostatic chamber.

  In recent years, a double oven type OCXO having a double thermostatic chamber has been provided (see, for example, Patent Document 1). The double oven type OCXO can generate a clock signal with higher accuracy than the single oven type OCXO having only one thermostatic chamber.

  Further, in a communication apparatus having a GPS (Global Positioning System) receiver, it is possible to correct a frequency error of a clock signal by using an accurate reference pulse signal obtained from a GPS signal received by the GPS receiver.

JP 2005-117189 A

  However, the configuration for correcting the frequency error of the clock signal using GPS is effective when the GPS signal can be normally received. However, if the GPS signal cannot be normally received, the frequency error of the clock signal is not corrected. Cannot be corrected and the accuracy of the clock signal is reduced.

  On the other hand, if a double oven type OCXO is used, a highly accurate clock signal can be generated in a period in which a GPS signal cannot be normally received. However, since the double oven type OCXO has a large size and cost, the communication device There is a problem that the size and cost of the device increase.

  Therefore, an object of the present invention is to provide a communication device and a clock correction method capable of operating using a highly accurate clock signal without using a double oven type OCXO even during a period in which the GPS signal cannot be normally received. To do.

  In order to solve the above-described problems, the present invention has the following features. First, a first feature of the present invention is a communication device (for example, a radio base station 1) having a crystal oscillator (crystal oscillator 11) and a GPS receiver (GPS receiver 12), which is generated by the crystal oscillator. A clock generator (clock generator 13) that generates a clock signal used for synchronization in the communication device from an oscillation pulse signal (oscillation pulse signal Pxo) to be generated, and a reference pulse obtained from a GPS signal received by the GPS receiver An error correction unit (error correction unit 15) that corrects the frequency error of the clock signal using a signal (reference pulse signal Pref), and a temperature measurement unit (temperature) that measures the temperature that affects the oscillation frequency of the crystal oscillator An error correction value indicating the frequency error corrected by the sensor 14) and the error correction unit is compared with the temperature when the error correction unit performs correction. And a correction value storage unit (correction value storage unit 16) for storing the reference pulse signal when the reference pulse signal cannot be obtained, the error correction unit is configured to correct the error corresponding to the temperature measured by the temperature measurement unit. The gist is to acquire a value from the correction value storage unit and correct the frequency error using the acquired error correction value.

  According to such a feature, when the reference pulse signal cannot be obtained, that is, when the GPS signal cannot be normally received, an error correction value corresponding to the temperature measured by the temperature measurement unit is acquired from the correction value storage unit, The frequency error is corrected using the acquired error correction value.

  As described above, the correspondence between the temperature and the frequency error is held, and the frequency error can be corrected using the correspondence. Thereby, even when the GPS signal cannot be normally received, the correction when the GPS signal can be normally received can be reproduced, and an accurate clock signal can be generated without using the double oven type OCXO.

  A second feature of the present invention relates to the first feature of the present invention, further comprising a time measuring unit (time measuring unit 17) for measuring time, wherein the correction value storage unit stores the error correction value as the error correction. When the reference pulse signal cannot be obtained, the error correction unit measures the time measured by the time measuring unit and the temperature measurement unit. The gist is to acquire the error correction value corresponding to the temperature from the correction value storage unit and correct the frequency error using the acquired error correction value.

  A third feature of the present invention relates to the first or second feature of the present invention, and when the reference pulse signal cannot be obtained, the error correction unit is configured according to the time measured by the time measuring unit. The gist is to change a time interval for correcting the frequency error.

  A fourth feature of the present invention relates to any one of the first to third features of the present invention, wherein the crystal oscillator is a single-oven type crystal oscillator with a thermostat having a single thermostat. The gist.

  A fifth feature of the present invention is that a clock signal for synchronizing operations is generated from an oscillation pulse signal generated by a crystal oscillator, and a temperature that affects the oscillation frequency of the crystal oscillator is measured. Using the reference pulse signal obtained from the GPS signal received by the GPS receiver, correcting the frequency error of the clock signal, and correcting the error correction value indicating the frequency error corrected in the correcting step And the step of associating with the temperature at the time of performing the correction in the step of performing, when the reference pulse signal cannot be obtained, the step of correcting includes the error corresponding to the temperature measured in the step of measuring The gist is to correct the frequency error using a correction value.

  According to the present invention, it is possible to provide a communication device and a clock correction method capable of operating using a highly accurate clock signal without using a double oven type OCXO even during a period in which a GPS signal cannot be normally received.

1 is an overall schematic configuration diagram of a communication system according to an embodiment of the present invention. It is a block diagram which shows the structure of the clock signal generation apparatus which concerns on embodiment of this invention. It is a figure which shows the structural example of the correction value table which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the clock signal generation apparatus which concerns on embodiment of this invention. It is a figure which shows the example of an internal mounting of the base station main-body part which concerns on embodiment of this invention. It is a figure which shows the example of an output of the analysis result of a correction value table.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) overall schematic configuration, (2) configuration of radio base station, (3) operation of clock signal generation device, (4) implementation example of base station main body, (5) operational effects, (6 ) Other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

  However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(1) Overall Schematic Configuration FIG. 1 is an overall schematic configuration diagram of a communication system including a radio base station 1 which is an embodiment of a communication apparatus of the present invention.

  The communication system shown in FIG. 1 includes a radio base station 1 and a radio communication terminal 2. The radio base station 1 performs radio communication with the radio communication terminal 2. The radio base station 1 is a small base station installed on, for example, a utility pole or a building wall. The radio base station 1 synchronizes with other radio base stations and performs an operation (for example, interference suppression operation) in cooperation between the base stations.

  The radio base station 1 includes an antenna unit 105 and a base station body unit 100. The antenna unit 105 and the base station main unit 100 are connected via a cable 190. The base station main body 100 is configured to be small and light so that it can be installed on a utility pole, a building wall surface or the like.

(2) Configuration of Radio Base Station FIG. 2 is a block diagram showing a configuration of the clock signal generation device 10 provided in the base station main body 100.

  As shown in FIG. 2, the clock signal generation device 10 includes a crystal oscillator 11, a GPS receiver 12, a clock generation unit 13, a temperature sensor 14 (temperature measurement unit), an error correction unit 15, and a correction value storage. The unit 16 and the time measuring unit 17 are included.

  The crystal oscillator 11 generates a pulse signal by oscillating at a predetermined oscillation frequency. Hereinafter, the pulse signal is referred to as an oscillation pulse signal Pxo. The crystal oscillator 11 has a characteristic (frequency temperature characteristic) in which the oscillation frequency changes when the temperature of the crystal oscillator 11 changes. In the present embodiment, the crystal oscillator 11 is a single oven type OCXO having one thermostat.

  The temperature sensor 14 measures the temperature. Here, the temperature measured by the temperature sensor 14 is at least one of three types: the temperature of the crystal oscillator 11, the temperature inside the base station body 100, and the temperature outside the base station body 100 (outside temperature). is there. These three types of temperatures affect the oscillation frequency of the crystal oscillator 11. The temperature measured by the temperature sensor 14 is notified to the error correction unit 15.

  When OCXO is used as the crystal oscillator 11, a temperature measuring element provided in advance in the crystal oscillator 11 can be used as the temperature sensor 14.

  When measuring the temperature in the base station main body 100, a temperature sensor 14 is provided outside the crystal oscillator 11 in the housing 110 (see FIG. 5) of the base station main body 100. When measuring the outside air temperature, the temperature sensor 14 is provided outside the housing 110.

  The GPS receiver 12 outputs 1 PPS (Pulse Per Second), which is a pulse signal with a period of 1 second synchronized with Coordinated Universal Time (UTC). Hereinafter, the pulse signal is referred to as a reference pulse signal Pref. However, although the GPS receiver 12 obtains the reference pulse signal Pref by synchronizing with a plurality of GPS satellites, the reference pulse signal Pref cannot be obtained if synchronization with the GPS satellite is lost. In such a case, generally, generation of a clock signal CLK (referred to as a holdover operation) depending on the accuracy of the crystal oscillator 11 is performed.

  The clock generation unit 13 generates a clock signal CLK used for synchronization in the radio base station 1 from the oscillation pulse signal Pxo generated by the crystal oscillator 11. For example, the clock generator 13 is configured to output a clock signal CLK for one clock each time the oscillation pulse signal Pxo is counted for a predetermined number of pulses. The clock signal CLK generated by the clock generation unit 13 is supplied to the digital unit 102 (see FIG. 5) in the base station main unit 100.

  The timer unit 17 measures the current time. The current time measured by the timer unit 17 is at least one of date and time. The timer unit 17 counts the current time using the clock signal CLK generated by the clock generator 13. The time that the temperature sensor 14 measures is notified to the error correction unit 15.

  The error correction unit 15 corrects the frequency error of the clock signal CLK using the reference pulse signal Pref from the GPS receiver 12. Various existing methods can be used as a method for correcting the frequency error using the reference pulse signal Pref.

  The correction value storage unit 16 includes an error correction value indicating the frequency error corrected by the error correction unit 15, a temperature when the error correction unit 15 performs correction, and a time when the error correction unit 15 performs correction. Is stored. Hereinafter, this table is referred to as a correction value table.

  FIG. 3 is a diagram illustrating an example of the correction value table. In the example of FIG. 3, in each correction value table, time (date and time), error correction value (“1PPS accuracy” in FIG. 3), and temperature (here, outside temperature) are associated with each other. . Further, there is one table every 10 minutes, for example, a correction value table for 24 hours is created. Note that PPB (Parts Per Billion) in FIG. 3 means one billionth. Each correction value table as shown in FIG. 3 is created by the error correction unit 15 and stored in the correction value storage unit 16. The error correction unit 15 also updates the correction value table stored in the correction value storage unit 16.

  The error correction unit 15 performs error correction corresponding to the temperature measured by the temperature sensor 14 and the time measured by the time measuring unit 17 when the reference pulse signal Pref cannot be obtained from the GPS receiver 12, that is, at the time of holdover. A value is acquired from the correction value storage unit 16, and the frequency error of the clock signal CLK is corrected using the acquired error correction value.

(3) Operation of Clock Signal Generation Device FIG. 4 is a flowchart showing the operation of the clock signal generation device 10.

  In step S11, the error correction unit 15 determines whether or not the reference pulse signal Pref from the GPS receiver 12 is obtained. If the reference pulse signal Pref from the GPS receiver 12 has been obtained, the process proceeds to step S12. If not, the process proceeds to step S13.

  In step S12, the error correction unit 15 corrects the frequency error of the clock signal CLK using the reference pulse signal Pref, and creates and updates a correction value table.

  In step S13 to step S15, the holdover operation is performed.

  In step S13, the temperature sensor 14 measures the current temperature, and the timer unit 17 measures the current time (date and time).

  In step S <b> 14, the error correction unit 15 determines whether a correction value table that matches the temperature and time measured in step S <b> 13 exists in the correction value storage unit 16.

  When a correction value table that matches the temperature and time measured in step S13 exists in the correction value storage unit 16, the error correction unit 15 acquires an error correction value from the correction value table in step S14.

  In step S15, the error correction unit 15 corrects the frequency error of the clock signal CLK using the acquired error correction value.

  In step S14, the error correction unit 15 does not have a correction value table that matches both the temperature and time measured in step S13 in the correction value storage unit 16, and matches the temperature measured in step S13. When the correction value table exists in the correction value storage unit 16, an error correction value may be acquired from the correction value table in step S14.

  At this time, when there are a plurality of correction value tables that match the temperature measured in step S13, the error correction unit 15 selects the time closest to the time measured in step S13 from among the correction value tables. The correction value table may be selected, and the error correction value may be acquired from the selected correction value table.

  In addition to the holdover operation in steps S13 to S15, the following processing may be performed. The error correction unit 15 refers to a plurality of correction value tables corresponding to a certain period before and after the time measured in step S13, and when the change amount of the error correction value in the correction value table is less than a predetermined value. Increases the time interval for correcting the frequency error of the clock signal CLK. On the other hand, the error correction unit 15 refers to a plurality of correction value tables corresponding to a certain period before and after the time measured in step S13, and the amount of change in the error correction value in these correction value tables is greater than or equal to a predetermined value. In this case, the time interval for correcting the frequency error of the clock signal CLK is shortened. Thereby, the processing load when the necessity for correction is low can be reduced.

(4) Mounting Example of Base Station Main Body FIG. 5 is a diagram illustrating an internal mounting example of the base station main body 100. However, configurations that are not related to the present invention, such as wiring connecting the electronic components, are omitted.

  As shown in FIG. 5, the base station main body 100 includes a housing 110, a power amplifier unit 101, a digital unit 102, a power supply unit 103, and a crystal oscillator 11.

  The power amplifier unit 101, the digital unit 102, the power supply unit 103, and the crystal oscillator 11 are housed in a housing 110.

  On the outer surface of the housing 110, there are formed heat radiating fins 111 for releasing heat generated by each electronic component (power amplifier unit 101, digital unit 102, power supply unit 103, etc.) in the housing 110 to the outside. Yes.

  Each electronic component (power amplifier unit 101, digital unit 102, power supply unit 103, etc.) generates heat. Heat generated by each electronic component (power amplifier unit 101, digital unit 102, power supply unit 103, etc.) is transmitted to housing 110. The heat transferred to the housing 110 is released from the outer surface of the housing 110 (such as the heat radiating fins 111) into the outside air. As described above, the temperature management is performed on the casing 110 of the base station main body 100.

  The power amplifier unit 101 is configured as an analog circuit. The power amplifier unit 101 includes a power amplifier, a filter circuit, and the like, and mainly performs radio signal amplification processing.

  The digital unit 102 is configured as a digital circuit and performs various signal processing. The digital unit 102 includes a DSP, FPGA, MPU, and the like. The digital unit 102 operates in synchronization with the clock signal from the crystal oscillator 11. The digital unit 102 includes the error correction unit 15 and the correction value storage unit 16 described above.

  The power supply unit 103 is configured as an analog circuit, and supplies power to the power amplifier unit 101, the digital unit 102, and the like.

  In the example of FIG. 5, the power supply unit 103 is located in the lower part inside the housing 110. The power supply unit 103 is directly attached to the bottom wall of the housing 110.

  The power amplifier unit 101 is located in the upper part inside the housing 110. The power amplifier unit 101 is directly attached to the upper wall of the housing 110.

  The digital unit 102 is located at the center inside the housing 110. The digital unit 102 is attached to the power amplifier unit 101.

  The crystal oscillator 11 is located in the lower part inside the housing 110. The crystal oscillator 11 is disposed in contact with the housing 110. Specifically, it is directly attached to the bottom wall of the housing 110.

  The portion of the housing 110 where the crystal oscillator 11 is disposed is located in the vicinity of an electronic component (for example, the power supply unit 103) that operates constantly, and is the portion of the housing 110 that has the least temperature change.

  Of each electronic component (power amplifier unit 101, digital unit 102, power supply unit 103, etc.), the crystal oscillator 11 is disposed in the vicinity of the electronic component having the closest operating temperature range to the operating temperature range of the crystal oscillator 11. Is preferred. The operating temperature range of the crystal oscillator 11 is determined by the specifications of the crystal oscillator 11 and is, for example, about 60 ° C. to 70 ° C.

(5) Effects According to the present embodiment, the error correction unit 15 measures the temperature sensor 14 when the reference pulse signal Pref cannot be obtained, that is, when the GPS receiver 12 cannot normally receive the GPS signal. An error correction value corresponding to the temperature is acquired from the correction value storage unit 16, and the frequency error is corrected using the acquired error correction value.

  As described above, the correspondence between the temperature and the frequency error is held, and the frequency error can be corrected using the correspondence. As a result, even when the GPS signal cannot be normally received, the correction can be performed with the same accuracy as when the GPS signal can be normally received.

  Further, in the present embodiment, the accuracy of correcting the frequency error can be further improved by performing correction in consideration of time in addition to temperature.

  Thus, by creating a mechanism for performing stable clock control based on past data in the base station, an expensive OCXO such as a double oven type OCXO is not necessary, and an inexpensive OCXO can be selected. . In addition, since the space for the oven (constant temperature bath) can be reduced, it is easy to secure a space for disposing other electronic components in the base station.

(6) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, a means for analyzing a correction value table stored in the correction value storage unit 16 and outputting (displaying or printing) the analysis result may be further provided. Thereby, the operator can grasp the state of the clock signal generation device 10. An example of outputting (displaying or printing) the analysis result of the correction value table is shown in FIG. By creating a correction value table, it is also possible to collect part characteristic data against environmental changes, and by analyzing the data collected throughout the year, trends in temperature changes and frequency fluctuations become clear. . It is possible to predict fluctuations with respect to changes in temperature from frequency fluctuation information obtained using the distribution of collected data, and it is possible to perform stable operation of the frequencies used for prediction.

  In the above-described embodiment, the correction value table includes time (date and time), but a configuration in which time is omitted is also possible. In this case, the timer 17 can be dispensed with.

  In the above-described embodiment, the crystal oscillator 11 is described as a single oven type crystal oscillator with a thermostat. However, a crystal oscillator having no thermostat may be used as the crystal oscillator 11.

  Further, the present invention is not limited to the case where the clock signal generation device 10 is provided in the radio base station 1. Since many wireless communication terminals in recent years are equipped with a GPS receiver, the clock signal generation device 10 can be provided in the wireless communication terminal 2.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  DESCRIPTION OF SYMBOLS 1 ... Wireless base station, 2 ... Wireless communication terminal, 10 ... Clock signal generator, 11 ... Crystal oscillator, 12 ... GPS receiver, 13 ... Clock generator, 13 ... Generator, 14 ... Temperature sensor, 15 ... Error correction , 16 ... correction value storage unit, 17 ... timing unit, 100 ... base station main unit, 101 ... power amplifier unit, 102 ... digital unit, 103 ... power supply unit, 105 ... antenna unit, 110 ... housing, 111 ... heat dissipation Fin, 190 ... Cable

Claims (5)

A communication device having a crystal oscillator and a GPS receiver,
A clock generator for generating a clock signal used for synchronization in the communication device from an oscillation pulse signal generated by the crystal oscillator;
An error correction unit that corrects a frequency error of the clock signal using a reference pulse signal obtained from a GPS signal received by the GPS receiver;
A temperature measurement unit that measures a temperature that affects the oscillation frequency of the crystal oscillator; and
A correction value storage unit that stores an error correction value indicating the frequency error corrected by the error correction unit in association with the temperature when the error correction unit performs correction;
When the reference pulse signal cannot be obtained, the error correction unit acquires the error correction value corresponding to the temperature measured by the temperature measurement unit from the correction value storage unit, and uses the acquired error correction value. A communication device for correcting the frequency error. It further includes a timekeeping unit that measures time,
The correction value storage unit stores the error correction value in association with the time when the error correction unit performs correction,
When the reference pulse signal cannot be obtained, the error correction unit acquires the error correction value corresponding to the time measured by the time measuring unit and the temperature measured by the temperature measurement unit from the correction value storage unit. The communication apparatus according to claim 1, wherein the frequency error is corrected using the acquired error correction value.   3. The communication apparatus according to claim 1, wherein, when the reference pulse signal cannot be obtained, the error correction unit changes a time interval for correcting the frequency error according to a time measured by the time measuring unit. .   The communication apparatus according to any one of claims 1 to 3, wherein the crystal oscillator is a single oven type crystal oscillator with a thermostat having one thermostat. Generating a clock signal for synchronizing operations from an oscillation pulse signal generated by a crystal oscillator;
Measuring a temperature that affects the oscillation frequency of the crystal oscillator;
Using a reference pulse signal obtained from a GPS signal received by the GPS receiver, correcting the frequency error of the clock signal;
Correlating an error correction value indicating the frequency error corrected in the correcting step with the temperature when the correction is performed in the correcting step,
A clock correction method for correcting the frequency error using the error correction value corresponding to the temperature measured in the measuring step in the correcting step when the reference pulse signal cannot be obtained.

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