JP2020156040A - Radio equipment - Google Patents

Abstract

To provide radio equipment which can stabilize the oscillation frequency of a reference oscillator even in an incapable state of communication with a reference oscillation source.SOLUTION: Moving body radio equipment includes: a reference oscillator 21 which oscillates a reference frequency to output a reference frequency signal; a frequency error detection and correction unit 41 which corrects the oscillation frequency of the reference oscillator 21 using a base station signal (first reference signal) received from a base station which is a reference oscillation source; a GPS receiver 45 which outputs a reference signal (second reference signal) which has a predetermined frequency; and a control unit 43 which, when a base station signal cannot be received, controls the frequency error detection and correction unit 41 to correct the oscillation frequency of the reference oscillator 21 using the reference signal output from the GPS receiver 45.SELECTED DRAWING: Figure 2

Description

The present invention relates to a radio that corrects the oscillation frequency of a reference oscillator using a reference signal received from a reference oscillation source.

In recent years, in wireless communication, the band has been narrowed from the viewpoint of effective use of frequency, and the frequency interval is also shifting from 25 kHz to 12.5 kHz and further to 6.25 kHz. With such a narrowing of the band, the deterioration of the reception performance with respect to the amount of frequency offset becomes large, so that the standard required for the radio is also required to have higher frequency stability.

A reference oscillator having high frequency stability such as OCXO (Oven Controlled Xtal Oscillator) is expensive and large, so that it is not practical to use it for a mobile radio. For this reason, in systems such as digital radio and MCA (Multi-Channel Access system), a reference oscillator with high frequency accuracy is provided on the base station side, and transmission is performed from the base station at an oscillation frequency with high frequency accuracy. Then, the mobile terminal has an AFC (Automatic Frequency Control) function that detects the difference from the own station oscillation frequency based on the received base station signal and follows the oscillation frequency of the base station so that the difference disappears. It is used to maintain the same frequency accuracy as the base station for communication. As shown in Patent Document 1, for example, the reference oscillator on the base station side is periodically calibrated based on a GPS signal from a GPS (Global Positioning System).

Hereinafter, the prior art relating to the mobile radio having the above-mentioned AFC function will be described with reference to FIG.
FIG. 1 is a block diagram showing a configuration example of a mobile radio used on a conventional mobile terminal side having an AFC function. The mobile radio of FIG. 1 includes an antenna 11, an antenna switch unit 12, a receiving RF unit 13, a mixer 14, a receiving IF unit 15, a mixer 16, a receiving baseband unit 17, and a demodulating unit 18. , PLL (Phase Locked Loop) 19, PLL 20, reference oscillator 21, transmission RF unit 22, mixer 23, modulation baseband unit 24, modulation unit 25, frequency error detection / correction unit. A 31 and a control circuit 32 are provided. The control circuit 32 has a control unit 33 and a memory 34.

First, the operation of the receiving system in the mobile radio of FIG. 1 will be described.
The base station signal received by the antenna 11 passes through the antenna switch unit 12 and is input to the receiving RF unit 13. The receiving RF unit 13 removes unnecessary components from the input signal, further amplifies the signal, and then outputs the signal to the mixer 14. The reference oscillator 21 oscillates the reference frequency and outputs the reference frequency signal to the PLL 19 and the PLL 20.

The PLL 19 generates an intermediate frequency (IF) signal based on the input reference frequency signal, and outputs the intermediate frequency (IF) signal to the mixer 14 and the mixer 23 as a local oscillation signal. The mixer 14 mixes the signal input from the reception RF unit 13 with the local oscillation signal input from the PLL 19, converts the frequency to the frequency of the IF signal, and outputs the frequency to the reception IF unit 15. The receiving IF unit 15 performs unnecessary components and amplification on the input signal, and outputs the signal to the mixer 16.

The PLL 20 generates a baseband signal based on the input reference frequency signal and outputs the baseband signal to the mixer 16. The mixer 16 mixes the signal input from the reception IF unit 15 with the local oscillation signal input from the PLL 20 to convert the frequency into the frequency of the baseband signal, and outputs the signal to the reception baseband unit 17. The reception baseband unit 17 removes and amplifies unnecessary components from the input signal, further performs A / D (Analog to Digital) conversion, and then outputs the signal to the demodulation unit 18. The demodulation unit 18 demodulates the input signal and outputs it as received data.

Next, the operation of frequency correction in the mobile radio of FIG. 1 will be described.
The demodulation unit 18 outputs a part (demodulation signal) of the demodulated received data to the frequency error detection / correction unit 31. The frequency error detection / correction unit 31 outputs a correction value to the reference oscillator 21 based on the input demodulation signal. The reference oscillator 21 corrects the oscillation frequency according to the input correction value, oscillates the reference frequency following the frequency of the signal received by the antenna 11, and outputs the reference frequency signal to the PLL 19 and the PLL 20. The frequency error detection / correction unit 31 also outputs the above correction value to the control unit 33 of the control circuit 32. The control unit 33 writes the correction value (that is, the correction value based on the frequency error) input from the frequency error detection / correction unit 31 to the memory 34.

Next, the operation of the transmission system in the mobile radio of FIG. 1 will be described.
In the control circuit 32, the control unit 33 reads out the correction value stored in the memory 34, outputs the correction value to the reference oscillator 21 via the frequency error detection / correction unit 31, and corrects the oscillation frequency of the reference oscillator 21. To do. The reference oscillator 21 oscillates the corrected reference frequency and outputs a reference frequency signal to the PLL 19. The PLL 19 generates an intermediate frequency (IF) signal based on the input reference frequency signal, and outputs the intermediate frequency (IF) signal to the mixer 14 and the mixer 23 as a local oscillation signal.

The transmission data is input to the modulation unit 25. The modulation unit 25 modulates the input transmission data into a modulation signal, and outputs the modulation signal to the modulation baseband unit 24. The modulation baseband unit 24 performs D / A (Digital to Analog) conversion, removal of unnecessary components, and amplification of the input modulation signal, and then outputs the modulation signal to the mixer 23. The mixer 23 mixes the signal input from the modulation baseband unit 24 with the local oscillation signal input from the PLL 19 and converts the frequency into the frequency of the final transmission signal transmitted from the antenna 11, and outputs the frequency to the transmission RF unit 22. To do. The transmission RF unit 22 removes unnecessary components after mixing of the input signal, amplifies it to the final output, and wirelessly transmits it from the antenna 11 via the antenna switch unit 12.

Japanese Unexamined Patent Publication No. 2000-3507

Even in a system in which the oscillation frequency of a mobile radio is made to follow the oscillation frequency of a base station, there is a need to perform communication even in an area where radio waves from the base station, which is a reference oscillation source, do not reach. In order to meet such needs, it is necessary to directly communicate between mobile radios. In this case, each mobile radio performs communication by correcting the transmission frequency with the frequency correction information (correction value of the reference frequency) that is finally matched.

However, since the mobile radio is a method in which its own oscillation frequency is made to follow the oscillation frequency of the base station, a reference oscillator of the mobile radio whose oscillation frequency is not so stable is used. In this way, the conventional mobile radio has poor stability over time of the reference oscillator itself, so if the elapsed time after correcting the frequency becomes long, the transmission frequency will gradually shift due to the influence of the time change of the reference oscillator itself. To go. In the worst case, there is a risk of exceeding the allowable frequency error.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radio that can stabilize the oscillation frequency of the reference oscillator even when communication with the reference oscillation source is not possible.

In order to achieve the above object, the radio device according to the present invention has the following technical features.
That is, in a radio that corrects the oscillation frequency of its own reference oscillator by using the first reference signal received from the reference oscillation source, a GPS receiver that outputs a second reference signal having a predetermined frequency is provided. When the first reference signal cannot be received, the second reference signal is used to correct the oscillation frequency of the reference oscillator.

As described above, in the radio device according to the present invention, when the first reference signal cannot be received from the reference oscillation source, the oscillation frequency of the reference oscillator is used by using the second reference signal output from the GPS receiver. Is corrected, so that the oscillation frequency of the reference oscillator can be stabilized even when communication with the reference oscillation source is not possible. As a result, even if the radio cannot communicate with the reference oscillation source for a long period of time, it is possible to prevent the transmission frequency from gradually shifting due to the influence of the time-dependent change of the reference oscillator itself.

Here, the radio device according to the present invention is in a state where it cannot receive the first reference signal, and corrects the oscillation frequency of the reference oscillator using the first reference signal or the second reference signal. When the elapsed time has exceeded a predetermined time, the oscillation frequency of the reference oscillator may be corrected by using the second reference signal.

Further, the radio device according to the present invention may be configured to measure the elapsed time using the time information output from the GPS receiver.

Further, the radio device according to the present invention is in a state where the first reference signal cannot be received, and when an error of a predetermined level or more occurs in the oscillation frequency of the reference oscillator, the second reference signal. May be used to correct the oscillation frequency of the reference oscillator.

According to the present invention, it is possible to provide a radio that can stabilize the oscillation frequency of the reference oscillator even when communication with the reference oscillation source is not possible.

It is a block diagram which shows the structural example of the conventional mobile radio. It is a block diagram which shows the structural example of the mobile radio device which concerns on one Embodiment of this invention. It is a figure explaining the operation of the phase error detection part of the mobile radio of FIG. It is a figure which illustrates the flowchart which concerns on the control process of the frequency correction by the mobile radio of FIG.

An embodiment of the present invention will be described with reference to FIGS. 2 to 4.
FIG. 2 is a block diagram showing a configuration example of a mobile radio device according to an embodiment of the present invention. In FIG. 2, the same components as those in FIG. 1 referred to in the description of the prior art are assigned the same numbers as those in FIG. The mobile radio of FIG. 2 controls the frequency error detection / correction unit 31 of the mobile radio of FIG. 1 and the control circuit 32 having the control unit 33 and the memory 34 with the frequency error detection / correction unit 41. It is replaced with a control circuit 42 having a unit 43 and a memory 44, and a GPS receiver 45 and a phase error detection unit 46 are added.

The control unit 43 controls the GPS receiver 45. The GPS receiver 45 receives radio waves from GPS satellites and outputs GPS signals including position information, time information, and the like to the control unit 43. The phase error detection unit 46 is a circuit used for comparing a high-precision reference signal obtained from the GPS receiver 45 with a reference frequency signal output from the reference oscillator 21, and the details will be described later.

In the mobile radio of FIG. 2, the operation of the receiving system, the operation of the transmitting system, and the operation of the frequency correction in the communication with the base station are the same as those in FIG. 1, and thus the description thereof will be omitted.
Hereinafter, the operation of frequency correction using the reference signal obtained from the GPS receiver 45 will be described.

The phase error detection unit 46 outputs the high-precision reference signal output from the GPS receiver 45 and the reference frequency signal output from the reference oscillator 21 to the frequency error detection / correction unit 41 as a comparison signal. The frequency error detection / correction unit 41 calculates the phase difference from the comparison signal, determines the frequency of the reference frequency signal, and outputs the correction value to the reference oscillator 21. The reference oscillator 21 corrects the oscillation frequency according to the input correction value, and outputs a reference frequency signal having a reference frequency that follows the reference signal of the GPS receiver 45. The frequency error detection / correction unit 41 also outputs the above correction value to the control unit 43 of the control circuit 42. The control unit 43 writes the correction value (correction value based on the frequency error) input from the frequency error detection / correction unit 41 to the memory 44, and also writes the time information output from the GPS receiver 45 to the memory 44. In this way, the control unit 43 writes the correction value and the time information to the memory 44 every time the frequency is corrected based on the reference signal from the GPS receiver 45.

When the mobile radio performs a transmission operation, the transmission data is transmitted after correcting the oscillation frequency of the reference oscillator 21 with the correction value stored in the memory 44. Since the operation of the transmission system is the same as that in FIG. 1 as described above, the description thereof will be omitted.

Next, the operation of the phase error detection unit 46 will be described in detail with reference to FIG. In the example shown in FIG. 3, the phase error detection unit 46 includes a PLL 47 and a comparator 48.
The reference frequency signal (reference oscillator clock) output from the reference oscillator 21 is a 19.2 MHz sine wave, which is frequency-converted by the PLL 47 into a sine wave of a predetermined frequency (10 kHz in this example) and input to the comparator 48. .. The output of the reference oscillator 21 (10 kHz sine wave) input to the comparator 48 is converted into a 10 kHz pulse wave (for example, a duty 50% square wave) compared with the reference voltage, and is converted into a frequency error detection / correction unit 41. Entered.

Further, the GPS receiver 45 has a function of outputting a TimePlus wave, and can output a pulse wave of a predetermined frequency (10 kHz in this example) of 1PPS (Pulse Per Second) by frequency control. The pulse wave output from the GPS receiver 45 is input to the frequency error detection / correction unit 41 as a reference signal.

The frequency error detection / correction unit 41 compares the 10 kHz pulse wave from the reference oscillator 21 with the reference signal from the GPS receiver 45, calculates a correction value such that these phase errors become 0, and uses the reference. Output to oscillator 21. As a result, the reference oscillator 21 corrects the oscillation frequency according to the correction value input from the frequency error detection / correction unit 41, and outputs a reference frequency signal having a reference frequency that follows the reference signal of the GPS receiver 45. It becomes possible.

FIG. 4 illustrates a flowchart relating to the frequency correction control process by the mobile radio of FIG. 2.
When the power of the mobile radio is turned on (step S10), the control unit 43 acquires the time information (current time) obtained from the GPS receiver 45, and at the time of the previous frequency correction stored in the memory 44. (Step S12), it is determined whether or not T time (for example, several months) has passed since the previous frequency correction (step S14).

If it is determined in step S14 that T time has elapsed since the previous frequency correction, frequency error determination is performed using the reference signal from the GPS receiver 45 (step S16). In this frequency error determination, the frequency error detection / correction unit 41 calculates the frequency error between the 10 kHz pulse wave from the reference oscillator 21 and the reference signal from the GPS receiver 45, and the frequency error is a predetermined threshold value X ( It is determined whether or not it is ppm) or more. Then, when the frequency error is equal to or higher than the threshold value X (for example, a value of about 1 ppm to 1.5 ppm), it is determined that the frequency error has occurred to a level that cannot follow the base station, and the reference from the GPS receiver 45 is obtained. The correction value is calculated using the signal, and the correction value is output to the reference oscillator 21 to correct the oscillation frequency (step S20). Further, the correction value is written to the memory 44, and the time information at that time (that is, the time of the current frequency correction) is written to the memory 44 (step S26).

Further, in step S14, it is determined that the T time has not elapsed since the previous frequency correction, or in step S16, it is determined that the frequency error from the reference signal from the GPS receiver 45 is less than the threshold value X. In that case, frequency correction is performed by following a normal base station. That is, first, the frequency error is determined by the base station signal (step S18). In this frequency error determination, the frequency error detection / correction unit 41 calculates the frequency error between the 10 kHz pulse wave from the reference oscillator 21 and the base station signal received by the antenna 11, and the frequency error is a predetermined threshold A. It is determined whether or not it is (ppm) or more. When the frequency error is equal to or higher than the threshold value A (for example, a value of about 1 ppm to 1.5 ppm), it is determined that the frequency error has occurred to a level that cannot follow the base station, and the base received by the antenna 11 is determined. The correction value is calculated using the station signal, and the correction value is output to the reference oscillator 21 to correct the oscillation frequency (step S20). Further, the correction value is written to the memory 44, and the time information at that time (that is, the time of the current frequency correction) is written to the memory 44 (step S26).

Further, in step S18, if it is determined that the frequency error with the base station signal received by the antenna 11 is less than the threshold value A, the frequency correction is not performed (step S24). In this example, the threshold value X and the threshold value A are set to the same value, but different values may be used.

As described above, the mobile radio of this example has a reference oscillator 21 that oscillates a reference frequency and outputs a reference frequency signal, and a base station signal (first reference signal) received from a base station that is a reference oscillation source. ) Is used to correct the oscillation frequency of the reference oscillator 21, the frequency error detection / correction unit 41, the GPS receiver 45 that outputs a reference signal (second reference signal) having a predetermined frequency, and the base station signal cannot be received. In the case of the state, the control unit 43 that controls the frequency error detection / correction unit 41 so as to correct the oscillation frequency of the reference oscillator 21 using the reference signal output from the GPS receiver 45 is provided.

As described above, in the mobile radio of this example, when the base station signal (first reference signal) from the base station which is the reference oscillation source cannot be received, the reference signal (reference signal) from the GPS receiver 45 ( Since the oscillation frequency of the reference oscillator 21 is corrected using the second reference signal), it is possible to stabilize the oscillation frequency of the reference oscillator 21 even when communication with the base station is not possible. As a result, even if the radio cannot communicate with the base station for a long period of time (for example, several months), the transmission frequency gradually shifts due to the influence of the time-dependent change of the reference oscillator 21 itself and deviates from the allowable frequency error. It can be prevented from being stored. Therefore, for example, in an area where communication with a base station is not possible, when it is used for a long period of time for communication with another mobile radio wave, or when it is used for communication with another mobile radio wave after long-term storage, etc. It is possible to suppress the risk of transmitting radio waves with frequencies that are not expected.

In the above embodiment, the elapsed time from the correction of the oscillation frequency of the reference oscillator 21 exceeds the predetermined time, and the oscillation frequency of the reference oscillator 21 has an error of a predetermined level or more. In some cases, the frequency correction using the GPS receiver 45 is performed, but when one of these is satisfied, the frequency correction using the GPS receiver 45 may be performed. That is, it suffices if the timing at which frequency correction using the GPS receiver 45 is required can be appropriately determined. As a result, it is possible to prevent the frequency correction using the GPS receiver 45 from being performed at an ineffective timing, so that the processing load on the mobile radio can be reduced.

Further, in the above embodiment, the base station is used as the reference oscillation source for transmitting the first reference signal, but the reference oscillation source is not limited to the base station, and other reference oscillators having high frequency stability are provided. It may be a wireless communication device.

Although the present invention has been described in detail above, it goes without saying that the present invention is not limited to the above configuration and may be realized by a configuration other than the above.
Further, the present invention provides, for example, a method or method for executing the process according to the present invention, a program for realizing such a method or method by a computer having hardware resources such as a processor or memory, and such a program. It is also possible to provide it as a storage medium for storing.

The present invention can be used in various radios that correct the oscillation frequency of the reference oscillator by using the reference signal received from the reference oscillation source.

11: Antenna, 12: Antenna switch section, 13: Reception RF section, 14: Mixer, 15: Reception IF section, 16: Mixer, 17: Reception base band section, 18: Demodulation section, 19: PLL, 20: PLL, 21: Reference oscillator, 22: Transmission RF section, 23: Mixer, 24: Modulation baseband section, 25: Modulation section, 31: Frequency error detection / correction section, 32: Control circuit, 33: Control section, 34: Memory, 41: Frequency error detection / correction unit, 42: Control circuit, 43: Control unit, 44: Memory, 45: GPS receiver, 46: Phase error detection unit, 47: PLL, 48: Comparator

Claims (4)

In a radio that corrects the oscillation frequency of its own reference oscillator using the first reference signal received from the reference oscillation source,
Equipped with a GPS receiver that outputs a second reference signal with a predetermined frequency
When the first reference signal cannot be received, the radio is characterized in that the oscillation frequency of the reference oscillator is corrected by using the second reference signal. In the radio according to claim 1,
In a state where the first reference signal cannot be received, the elapsed time from the correction of the oscillation frequency of the reference oscillator using the first reference signal or the second reference signal exceeds a predetermined time. If so, the radio is characterized in that the oscillation frequency of the reference oscillator is corrected by using the second reference signal. In the radio according to claim 2,
A wireless device characterized in that the elapsed time is measured using the time information output from the GPS receiver. In the radio according to any one of claims 1 to 3.
When the first reference signal cannot be received and an error of a predetermined level or more occurs in the oscillation frequency of the reference oscillator, the second reference signal is used to determine the oscillation frequency of the reference oscillator. A radio that is characterized by making corrections.

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