JP2006157302A - Oscillation method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillation method and an oscillating apparatus for oscillating a signal with a stable frequency. <P>SOLUTION: An antenna 10 receives signals from a plurality of GPS satellites. A satellite signal reception section 14 generates a plurality of timing signals from reception timings of a plurality of navigation messages, and works out an elevation angle of a satellite corresponding to an acquired and received signal. A statistic processing section 16 applies statistic processing to time components among a plurality of the timing signals and provides an output of the result as a reference signal. In the statistic processing, weighting by the elevating angle of the satellite is carried out. A PLL 18 oscillates to provide a signal on the basis of the reference signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an oscillation technique, and more particularly to an oscillation method and an oscillation device that oscillate a signal having a predetermined frequency.

A wireless communication device or the like internally oscillates a signal having a predetermined frequency and uses the signal for communication. An example of use is timing control and frequency conversion. At that time, the frequency of the signal should be set to a predetermined value, and a PLL (Phase Locked Loop) is used for setting the frequency. An oscillator that oscillates such a signal is generally affected by temperature, and as a result, the frequency of the oscillated signal changes. Therefore, conventionally, the frequency is set by the PLL as usual in a steady state after a predetermined period of time has elapsed after receiving the signal. On the other hand, the frequency is set based on the temperature around the oscillator until a predetermined period elapses after the signal is received. That is, in such a period, the temperature of the oscillator is not stabilized, so that the frequency is controlled based on the temperature, not the frequency controlled by the PLL (see, for example, Patent Document 1).
JP 2000-36739 A

  A global positioning system (hereinafter referred to as “GPS (Global Positioning System)”) has been put to practical use as a system for measuring a position on the earth. The GPS is mainly composed of a plurality of GPS satellites and a GPS receiver on the earth. The GPS receiver receives signals from a plurality of GPS and measures the position by using the propagation delay of these signals. In such GPS, the frequency stability of the oscillator provided in the GPS satellite is higher than the frequency stability of the oscillator provided in the GPS receiver. Therefore, the improvement in frequency stability in the GPS receiver is realized by synchronization with the frequency in the GPS satellite. That is, the GPS receiving device receives a signal from a GPS satellite, further operates a PLL based on timing and frequency components included in the received signal, and oscillates a signal with high frequency stability. One of the timing signals included in the received signal is a pulse signal (hereinafter referred to as “1PPS”) having a period of 1 second.

  Under such circumstances, the present inventor has come to recognize the following problems. When the GPS receiver receives signals from a plurality of GPS satellites, the GPS receiver forms one timing signal from all the received signals. For this reason, if the error with respect to the arrival time of the signal from the GPS satellite increases due to the positional relationship between at least one of the GPS satellites and the GPS receiver, the error in the timing signal generation period also increases. As a result, the accuracy of the frequency of the signal oscillated by the PLL with the timing signal as a reference deteriorates. Factors that increase the error with respect to the arrival time of the signal include the influence of the ionosphere and multipath.

  On the other hand, according to the prior art, if the frequency is set based on the temperature around the oscillator until a predetermined period elapses after reception of the signal, the influence of the temperature in the oscillator is reduced during the period. However, if the frequency of the signal is controlled by a normal PLL after the period has elapsed, the frequency of the signal oscillated by the oscillator changes when a sudden temperature change occurs around the oscillator. Furthermore, if the PLL time constant is set to a long time constant in order to reduce the influence of short-term fluctuations in the timing signal itself, it becomes difficult to follow the change in frequency. As a result, when a sudden temperature change occurs around the oscillator, the frequency of the oscillated signal temporarily deviates greatly.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an oscillation technique for oscillating a highly stable signal.

  In order to solve the above-described problem, an oscillation device according to an aspect of the present invention receives signals from a plurality of transmission devices, and corresponds to each of the received signals and a timing signal corresponding to each of the received signals. A satellite signal receiving unit for deriving a signal received after weighting a time component of the timing signal according to information related to the reliability of the timing signal, and a timing corresponding to each of the information signal related to the reliability corresponding to the timing signal Between the signals, a statistical processing unit that statistically processes a time component of the timing signal and an oscillation unit that oscillates the signal based on the statistically processed timing signal are provided.

  According to this aspect, when statistical processing is performed on a plurality of timing signals, the timing signal after statistical processing can be made highly accurate by using information related to reliability. Therefore, it is possible to stabilize the oscillation signal based on the timing signal. Can increase the sex.

  The satellite signal receiving unit may derive the signal intensity corresponding to each received signal and the elevation angle of the satellite corresponding to each received signal as information on reliability. In this case, a cause that is assumed to affect the timing signal can be used.

  The statistical processing unit may statistically process the time component of the timing signal between timing signals corresponding to each of the received signals, using the signal strength and the elevation angle of the satellite as parameters. In this case, since the signal strength and the elevation angle of the satellite are used as parameters when performing statistical processing, it is possible to consider the cause that is assumed to cause an error in the timing signal.

  The statistical processing unit weights the time component of the timing signal according to the reliability information corresponding to the timing signal, and then statistically processes the time component of the timing signal between the timing signals corresponding to the received signals. May be. In this case, when statistical processing is performed on a plurality of timing signals, the timing signal after statistical processing can be made highly accurate by weighting with information related to reliability, so that the stability of the oscillation signal based on the timing signal is improved. Can be high.

  The satellite signal receiving unit derives signal strengths corresponding to the received signals as information relating to reliability, and the statistical processing unit weights the time components of the timing signal based on the signal strengths. In this case, since the weighting is reduced for a signal with low signal strength, the influence of the timing error can be reduced.

  The plurality of transmission devices are a plurality of satellites, the satellite signal receiving unit derives the elevation angle of the satellite corresponding to each of the received signals as information on reliability, and the statistical processing unit performs timing according to the elevation angle of the satellite. Weights the time component of the signal. In this case, since the weighting is reduced for a signal having a low elevation angle, the influence of the timing error can be reduced.

  Another embodiment of the present invention is also an oscillation device. This device adjusts the oscillation frequency with a control voltage, and outputs a phase difference between an oscillation unit that outputs a signal of the adjusted oscillation frequency, a signal output from the oscillation unit, and a signal to be used as a reference. A comparison unit, a loop filter that smoothes the phase difference derived in the phase comparison unit, feeds back the smoothed phase difference to the oscillation unit as a control voltage, and a time constant of the loop filter based on a temperature change around the oscillation unit And a control unit for controlling.

  According to this aspect, since the time constant of the loop filter is controlled according to the temperature change, it is possible to control to follow the change even when the oscillation frequency changes due to a rapid temperature change.

  The control unit may decrease the time constant of the loop filter if the temperature change becomes larger than a predetermined threshold value. The time component of the timing signal between the satellite signal receiving unit that receives signals from a plurality of transmission devices and derives a timing signal for each of the received signals and the timing signal corresponding to each of the received signals And a statistical processing unit that outputs to the phase comparison unit as a signal to be referenced based on the statistically processed timing signal, and the satellite signal receiving unit performs timing with respect to each of the received signals. Information regarding the reliability of the signal may also be derived, and the statistical processing unit may perform the statistical processing after weighting the time component of the timing signal with the information regarding the reliability corresponding to the timing signal. In this case, when statistical processing is performed on a plurality of timing signals, the timing signal after statistical processing can be made highly accurate by weighting with reliability information, so that the stability of the oscillation signal based on the timing signal is improved. Since the time constant of the loop filter is controlled in accordance with the temperature change, even when the oscillation frequency changes due to a sudden temperature change, it can be controlled to follow the change.

  Yet another embodiment of the present invention is also an oscillation device. This device adjusts the oscillation frequency with a control voltage, and outputs a phase difference between an oscillation unit that outputs a signal of the adjusted oscillation frequency, a signal output from the oscillation unit, and a signal to be used as a reference. The correction unit, a loop filter for smoothing the phase difference derived by the phase comparison unit, and the smoothed phase difference are corrected based on a correction value corresponding to a temperature change around the oscillation unit, and the corrected level is obtained. A correction unit that feeds back the phase difference as a control voltage to the oscillation unit, a difference between the phase difference corrected by the correction unit and the phase difference derived by the phase comparison unit while reflecting a temperature change around the oscillation unit An update unit that updates the correction value and outputs the updated correction value to the correction unit.

  According to this aspect, the correction value is updated while reflecting the temperature change around the oscillation unit for the difference between the phase difference corrected by the correction unit and the phase difference derived by the phase comparison unit. A control voltage that reduces the change in the oscillation frequency due to the change can be derived.

  The update unit includes a temperature detection unit that obtains a temperature change around the oscillation unit, a plurality of differences, a change amount deriving unit that derives a change amount with respect to the temperature change of the correction value from the plurality of temperature changes, and a temperature detection unit A correction value deriving unit that updates the correction value based on the acquired temperature change and the change amount derived by the change amount deriving unit and outputs the updated correction value to the correction unit may be provided. In this case, it is possible to derive a highly accurate change amount by considering a plurality of differences and temperature changes, and by adding a temperature change to this, a correction value that is highly accurate and can follow the change can be derived.

  The change amount deriving unit uses the means for deriving a difference between the phase difference corrected by the correcting unit and the phase difference derived by the phase comparing unit, and the change is derived by using the derived difference and the acquired temperature change. Means for deriving an equation including a quantity, and means for deriving a change amount by statistically processing a plurality of equations including the change amount may be included. In this case, since the amount of change is derived by statistically processing the equation at the predetermined timing and the equation at the predetermined timing derived a plurality of times, the accuracy of the amount of change can be increased.

  The time component of the timing signal between the satellite signal receiving unit that receives signals from a plurality of transmission devices and derives a timing signal for each of the received signals and the timing signal corresponding to each of the received signals And a statistical processing unit that outputs to the phase comparison unit as a signal to be referenced based on the statistically processed timing signal, and the satellite signal receiving unit performs timing with respect to each of the received signals. Information regarding the reliability of the signal may also be derived, and the statistical processing unit may perform the statistical processing after weighting the time component of the timing signal with the information regarding the reliability corresponding to the timing signal.

  In this case, when statistical processing is performed on a plurality of timing signals, the timing signal after statistical processing can be made highly accurate by weighting with reliability information, so that the stability of the oscillation signal based on the timing signal is improved. The correction value is updated while reflecting the temperature change around the oscillation unit for the difference between the phase difference corrected by the correction unit and the phase difference derived by the phase comparison unit. A control voltage that reduces the change in the oscillation frequency due to the change can be derived.

  Yet another embodiment of the present invention is an oscillation method. This method statistically processes the time component of the timing signal between timing signals derived corresponding to each of the received signals from a plurality of transmission devices, and oscillates the signal based on the statistically processed timing signal Information relating to the reliability of the timing signal corresponding to each of the received signals is derived, the time component of the timing signal is weighted by the information relating to the reliability corresponding to the timing signal, and then the statistics Process.

  Yet another embodiment of the present invention is also an oscillation method. In this method, in the oscillator, a step of outputting a signal of the adjusted oscillation frequency while adjusting the oscillation frequency by a control voltage, a phase difference between the signal output from the oscillator and the signal to be used as a reference is loop-filtered. And a step of feeding back the smoothed phase difference to the oscillator as a control voltage and a step of controlling a time constant of the loop filter based on a temperature change around the oscillator.

  Yet another embodiment of the present invention is also an oscillation method. In this method, in the oscillator, a step of outputting a signal of the adjusted oscillation frequency while adjusting the oscillation frequency by a control voltage, a phase difference between the signal output from the oscillator and the signal to be used as a reference is loop-filtered. And a step of correcting the smoothed phase difference based on a correction value corresponding to a temperature change around the oscillator, and feeding back the corrected phase difference to the oscillator as a control voltage. The step of updating the correction value while reflecting the temperature change around the oscillator with respect to the difference between the phase difference and the phase difference input to the loop filter, and outputting the updated correction value to the feedback step. Prepare.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, a highly stable signal can be oscillated.

Example 1
Before describing the present invention in detail, an outline will be described. Embodiment 1 of the present invention relates to a receiving apparatus that receives signals from a plurality of GPS satellites. The receiving apparatus according to the embodiment measures the current position based on signals from a plurality of GPS satellites. Furthermore, the receiving device generates a signal having a predetermined oscillation frequency using a PLL based on a timing signal generated based on signals from a plurality of GPS satellites. At that time, in the receiving apparatus according to the embodiment, in order to oscillate a signal having a small timing error even if the timing signal generated based on the signal from any of the plurality of GPS satellites includes a large timing error, Execute the process. The timing signal corresponds to the aforementioned 1PPS.

  The receiving device also derives the elevation angle for each of the plurality of GPS satellites, and calculates the average of the timing signals while weighting the time component of the timing signal corresponding to each of the plurality of GPS by the elevation angle (hereinafter referred to as the averaged timing). The signal is called the “reference signal”). Further, the receiving apparatus oscillates the signal while using the reference signal as a reference of the PLL. Here, a signal from a satellite with a low elevation angle is more affected by the ionosphere because the passage distance of the ionosphere is longer than a signal from a satellite with a high elevation angle. As a result, a signal from a satellite having a low elevation angle generally has a large timing error. Since the receiving apparatus according to the present embodiment reduces the weighting of such a signal when deriving the reference signal, the timing error in the reference signal can be reduced even if a signal having a large timing error is included.

  FIG. 1 shows a configuration of a receiving apparatus 100 according to Embodiment 1 of the present invention. The receiving apparatus 100 includes an antenna 10, a satellite signal receiving unit 14, a statistical processing unit 16, and a PLL 18. The PLL 18 includes a phase comparison unit 28, a loop filter 30, an oscillation unit 32, and a frequency division unit 34.

  The antenna 10 receives signals from a plurality of GPS satellites (not shown). The satellite signal receiving unit 14 receives navigation messages corresponding to the received signals. In addition, the satellite signal receiving unit 14 outputs a timing signal, which is the satellite time of each satellite calculated based on the received navigation message of each satellite, to the statistical processing unit 16. Furthermore, the satellite signal receiving unit 14 derives the elevation angle of the satellite corresponding to each of the received signals based on the navigation message as information on reliability. That is, a plurality of elevation angles corresponding to a plurality of GPS satellites are derived. Since the method for deriving the elevation angle of the satellite is well known, a description thereof will be omitted. The satellite signal receiving unit 14 outputs a plurality of elevation angles to the statistical processing unit 16.

The statistical processing unit 16 statistically processes the time component of the timing signal between the plurality of timing signals. Here, averaging is performed as statistical processing. The average of time components corresponds to a process of deriving “1.1 seconds” for “1 second” and “1.2 seconds”. When executing the averaging, the statistical processing unit 16 weights the time component of the timing signal using the elevation angle of the satellite corresponding to the timing signal as a parameter. Here, the timing error will be described before weighting. 2A to 2E show the timing of signals to be processed in the statistical processing unit 16. FIG. FIG. 2A shows a reference time. This corresponds to the time in the GPS satellite. FIG. 2B shows a timing signal t _real in the GPS satellite, which has a timing corresponding to FIG.

FIG. 2C shows a timing signal t _SV1 based on the signal received from the first GPS satellite. Note that the timing signal corresponds to the satellite time of each satellite, and the influence of the propagation time from the GPS satellite to the receiving device 100 is excluded. As shown in the figure, t _SV1 has a timing error of Δt ₁ and Δt ₁ ′ with respect to the timing signal t _real . The timing error is based on the influence of multipath and ionosphere. 2D and _2E show timing signals t _SV2 and t _{SVn in} signals received from the second GPS satellite and the N-th GPS satellite. As shown in the figure, t _SV2 and t _SVn have timing errors of Δt 2 and Δt 2 ′ and _{Δtn and Δtn} ′. Since the propagation environment between the first GPS and the Nth GPS is different, the influence of the multipath and the ionosphere is different on the timing signals t _SV1 , t _SV2 , t _SVn . As a result, the timing error for each is also different.

Hereinafter, weighting will be described. Assuming that each of the plurality of timing signals is t _SVi and the elevation angle of the corresponding satellite is ELVi, the timing signal t _SVWi weighted by the elevation angle of the satellite is expressed as follows.
(Equation 1)
t _SVWi = t _SVi × ELVi / 90 °
Here, if the number of a plurality of timing signals, that is, the number of GPS satellites to be received is N, the reference signal t _out is expressed as follows.
(Equation 2)
t _out = _{Σt SVWi} / N
The statistical processing unit 16 outputs the reference signal t _out to the PLL 18 in FIG.

Further, the weighting will be specifically described. FIG. 3 shows an example of processing in the statistical processing unit 16. The figure shows the elevation angle from the first GPS satellite “SV1” to the sixth GPS satellite “SV6”, the timing signal “t _SVi ” before weighting, and the timing signal “t _SVW i” after weighting. It is assumed that the timing signal t _real in the GPS satellite is “0 ns”. The elevation angles are shown as 10 °, 30 °, 40 °, 65 °, 70 ° and 90 °, respectively. The timing signals before weighting are indicated as 80 ns, 65 ns, 60 ns, 50 ns, 29 ns, and 15 ns, respectively. When the weighted timing signal is derived from the elevation angle and the timing signal based on Equation 1, 9 ns, 22 ns, 27 ns, 36 ns, 23 ns, and 15 ns are obtained. Therefore, according to Equation 2, the reference signal is 13 ns. On the other hand, if weighting is not performed and an average value of timing signals before weighting is derived, 50 ns is obtained. As a result, timing errors are reduced by weighting. This is because the timing error increases as the elevation angle of the GPS satellites decreases, but the weighting of timing signals for such GPS satellites is reduced.

  The PLL 18 oscillates a signal based on the reference signal. The phase comparator 28 derives a phase difference between the signal from the frequency divider 34 and the reference signal. Here, the signal from the frequency divider 34 corresponds to the signal output from the oscillator 32. The phase comparison unit 28 outputs the derived phase difference to the loop filter 30. Here, the phase difference forms a pulse signal on the time axis. The loop filter 30 smoothes the phase difference derived by the phase comparison unit 28 and outputs the smoothed phase difference to the oscillation unit 32 as a control voltage. That is, the loop filter 30 cuts the AC component of the pulse signal and converts the pulse signal to DC. Therefore, the loop filter 30 is configured by an integration circuit and a low-pass filter.

  The oscillating unit 32 adjusts the oscillation frequency by the control voltage from the loop filter 30 and outputs a signal having the adjusted oscillation frequency. That is, the oscillation unit 32 has a predetermined free-running frequency, and adjusts the oscillation frequency by applying a control voltage. This adjustment corresponds to the phase adjustment operation with the reference signal. Generally, if the signal phase in the signal of the oscillating unit 32 is advanced, the oscillation frequency is lowered to delay the phase, and if the signal phase is delayed, the oscillation frequency is increased to advance the phase. As a result, the oscillating unit 32 controls the phase of the signal to be oscillated so that the phase difference from the reference signal becomes zero. The frequency divider 34 divides the signal oscillated by the oscillator 32 and outputs the frequency-divided signal to the phase comparator 28.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of an arbitrary computer, and in terms of software, it is realized by a program having a reservation management function loaded in memory. The functional block realized by those cooperation is drawn. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The operation of the receiving apparatus 100 having the above configuration will be described. The satellite signal receiving unit 14 receives signals from a plurality of GPS satellites, and derives a plurality of timing signals and elevation angles, which are reliability information corresponding to them, based on the received signals. The statistical processing unit 16 derives the reference signal by weighting the time components of the timing signal by the elevation angle and then calculating the average of them. The phase comparator 28 calculates the phase difference between the reference signal and the signal from the frequency divider 34, and the loop filter 30 smoothes the phase difference. The oscillating unit 32 oscillates a signal while adjusting the oscillation frequency based on the control voltage output from the loop filter 30. The oscillated signal is input to the phase comparator 28 via the frequency divider 34.

  According to the embodiment of the present invention, when averaging a plurality of timing signals, the reference signal can be made highly accurate by performing weighting by the elevation angle, so that the stability of the oscillation signal based on the reference signal can be increased. . Even if the number of receivable GPS satellites is small, timing signals corresponding to low elevation angles are not excluded from the average target, so the number of timing signals targeted for averaging is not reduced, and the reference signal Reduction in accuracy can be reduced. Further, since the elevation angle can be derived from the navigation message, the processing can be simplified. Further, since the elevation angle is used as a reference for weighting, the influence of the ionosphere and the influence of multipath can be reflected. In addition, since a signal with a low elevation angle has low reliability, the influence of the timing error can be reduced by reducing the weighting. In addition, since the influence of the timing error can be reduced, an accurate reference signal can be derived. In addition, since an accurate reference signal can be derived, the oscillation frequency of the oscillated signal can be stabilized. Further, since the PLL configuration may be a conventional one, a new design can be eliminated. Further, since the conventional PLL configuration may be used, the manufacturing cost can be reduced.

(Example 2)
The second embodiment of the present invention relates to a receiving device that receives signals from a plurality of GPS satellites, as in the first embodiment. Similarly to the first embodiment, the receiving apparatus according to the second embodiment weights the timing signal included in the signal from the GPS satellite even if the elevation angle with respect to any of the plurality of GPS satellites is small. Calculate the average of the timing signal while decreasing. Furthermore, the receiving apparatus according to the second embodiment executes the following process in order to maintain the frequency stability of the signal even when a sudden temperature change occurs around the oscillation unit. The receiving device acquires a temperature change around the oscillation unit. Further, if the temperature change is larger than a predetermined threshold, the receiving apparatus decreases the time constant of the loop filter so that the frequency of the signal follows the rapid temperature change. As a result, the frequency of the signal changes more rapidly than when the time constant of the loop filter is large.

  FIG. 4 shows the configuration of the receiving apparatus 100 according to the second embodiment of the present invention. In FIG. 4, a control unit 36 and a temperature detection unit 38 are added to the receiving apparatus 100 of FIG. 1. As described above, the loop filter 30 smoothes the phase difference derived by the phase comparison unit 28 and outputs the smoothed phase difference to the oscillation unit 32 as a control voltage. In the loop filter 30, the smoothing period is determined by a set time constant. The time constant is generally set to a large value to some extent in order to reduce the influence of short-term fluctuations. When a sudden temperature change occurs around the oscillating unit 32, the oscillation frequency 25 of the oscillating unit 32 changes greatly due to the temperature change. At this time, if the time constant is large, the change cannot be followed.

  For example, it is assumed that the phase comparison between the reference signal and the signal from the frequency divider 34 is performed at 1 second intervals, and the time constant of the loop filter 30 is 100 seconds. The loop filter 30 uses the phase difference as an input value, performs smoothing for a time of a time constant, that is, 100 seconds, and derives a control voltage. Here, if the oscillation frequency in the oscillating unit 32 varies, the phase difference input to the loop filter 30 becomes an extremely large value. The control voltage to be output by the loop filter 30 in the subsequent 100 seconds remains affected by a large value. As a result, a certain period is required until the control voltage reaches a steady state, so that the oscillation frequency varies.

  The temperature detection unit 38 acquires the temperature around the oscillation unit 32 or a temperature change. The income cycle may be a predetermined interval. The control unit 36 controls the time constant of the loop filter 30 based on the temperature change acquired by the temperature detection unit 38. That is, the control unit 36 decreases the time constant of the loop filter 30 when the temperature change becomes larger than a predetermined threshold value. For example, when the temperature change becomes larger than a predetermined threshold value, the time constant of the loop filter 30 is switched from 100 seconds to 10 seconds. That is, the magnitude of the time constant is set to 1/10. As a result, the influence of frequency fluctuation can be shortened to 1/10 time. It should be noted that a plurality of threshold values for temperature changes and corresponding time constants may be provided, and switched to any one of a plurality of time constants according to the magnitude of the temperature change. Further, when the magnitude of the temperature change becomes less than the threshold value, the control unit 36 returns the time constant to the original value.

  FIG. 5 is a flowchart showing a procedure of time constant control in the control unit 36. The temperature detection unit 38 acquires a temperature change (S10). If the acquired temperature change is greater than the threshold value (Y in S12) and the time constant has not been changed to a smaller value (N in S14), the control unit 36 changes the time constant to a smaller value (S16). On the other hand, if the time constant is switched to a smaller value (Y in S14), the process is terminated. If the acquired temperature change is not larger than the threshold value (N in S12) and the time constant is changed to a small value (Y in S18), the control unit 36 restores the time constant (S20). . On the other hand, if the time constant has not been changed to a small value (N in S18), the process is terminated.

  The operation of the receiving apparatus 100 having the above configuration will be described. The satellite signal receiving unit 14 receives signals from a plurality of GPS satellites, and derives a plurality of timing signals and elevation angles, which are reliability information corresponding to them, based on the received signals. The statistical processing unit 16 derives the reference signal by weighting the time components of the timing signal by the elevation angle and then calculating the average of them. The phase comparator 28 calculates the phase difference between the reference signal and the signal from the frequency divider 34, and the loop filter 30 smoothes the phase difference. The oscillating unit 32 oscillates a signal while adjusting the oscillation frequency based on the control voltage output from the loop filter 30. The oscillated signal is input to the phase comparator 28 via the frequency divider 34. The temperature detection unit 38 acquires a temperature change around the oscillation unit 32. The control unit 36 performs control so that the time constant of the loop filter 30 is reduced when the temperature change becomes larger than the threshold value.

  According to the embodiment of the present invention, since the time constant of the loop filter is controlled according to the temperature change, it is possible to follow the change of the oscillation frequency due to the rapid temperature change. Further, since the time constant of the loop filter is controlled, the processing can be simplified. Even when a sudden temperature change occurs, the oscillation frequency can be controlled to approach a constant value by detecting the temperature change and using it for control. In addition, even when a temperature change occurs, fluctuations in the oscillation frequency can be reduced. Further, if the temperature change becomes small, the value of the loop filter is returned from the small value to the original value, so that the oscillation frequency can be stabilized. In addition, the influence of temperature change on the oscillation frequency can be reduced. In addition, when averaging a plurality of timing signals, the reference signal can be made highly accurate by weighting with the elevation angle, so that the stability of the oscillation signal based on the reference signal can be increased, and in response to temperature changes. Since the time constant of the loop filter is controlled, it is possible to follow a change in the oscillation frequency due to a rapid temperature change, and the oscillation frequency can be quickly converged even when the subsequent temperature change becomes gentle.

(Example 3)
The third embodiment of the present invention relates to a receiving apparatus that receives signals from a plurality of GPS satellites, as in the first embodiment. Further, similarly to the first embodiment, the receiving apparatus according to the third embodiment weights the timing signal included in the signal from the GPS satellite even if the elevation angle with respect to any of the plurality of GPS satellites is small. Calculate the average of the timing signal while decreasing. Further, as in the second embodiment, the receiving apparatus according to the third embodiment maintains the frequency stability of the signal even when a sudden temperature change occurs around the oscillation unit. However, the processing for maintaining the stability is different from that in the second embodiment.

  The receiving device corrects the phase difference output from the loop filter with the correction value, and then inputs the correction as a control voltage to the oscillation unit. The correction value corresponds to a value for correcting a change in frequency due to a temperature change in the oscillation unit. Such a correction value can be approximated by an equation of a linear function of temperature change. In order to derive such a correction value, the receiving device derives the difference between the corrected phase difference and the phase difference before being input to the loop filter, and the difference value corresponds to the temperature change at that time. To derive a linear function equation. In addition, the least squares method including the difference in phase difference sampled at a plurality of points during the temperature change and a plurality of equations derived from the temperature change is performed, and a statistically processed linear function constant (hereinafter referred to as “change amount”). )). The receiving device derives a correction value using the change amount and the temperature change. In the case of a linear function, the correction value is derived by multiplying the change amount by the temperature change. Since the correction value is derived using the temperature change at the time of executing the correction, the correction value can follow a rapid temperature change. In addition, since the change amount is subjected to statistical processing, the reliability of the correction value can be improved.

  FIG. 6 shows the configuration of the receiving apparatus 100 according to the third embodiment of the present invention. In FIG. 6, a correction unit 40 and an update unit 42 are added to the reception device 100 of FIG. 1. The update unit 42 includes a temperature detection unit 44, a change amount deriving unit 46, and a correction value deriving unit 48. Further, the signal includes a phase difference signal 200, a control voltage 202, a correction parameter 204, and a temperature signal 206.

  The phase comparator 28 derives a phase difference between the signal from the frequency divider 34 and the reference signal, and outputs the result as a phase difference signal 200. The loop filter 30 smoothes the phase difference derived by the phase comparison unit 28 and outputs it to the correction unit 40. The correction unit 40 corrects the smoothed phase difference based on the correction value from the correction unit 40, and outputs the corrected phase difference as the control voltage 202 to the oscillation unit 32. Here, the correction value from the correction unit 40 is a correction value corresponding to a temperature change around the oscillation unit 32, and will be described in detail later. The oscillating unit 32 adjusts the oscillation frequency by the control voltage 202 and outputs a signal having the adjusted oscillation frequency.

  The update unit 42 updates the correction value while reflecting the temperature change around the oscillation unit 32 with respect to the difference between the control voltage 202 and the phase difference signal 200, and outputs the updated correction value to the correction unit 40. The details are as follows. The temperature detection unit 44 acquires a temperature change around the oscillation unit 32. The temperature detection unit 44 outputs the acquired temperature change as the temperature signal 206 to the change amount deriving unit 46 and the correction value deriving unit 48.

  The change amount deriving unit 46 calculates the change amount, that is, the change amount of the correction value with respect to the temperature change, from the plurality of differences obtained by the plurality of control voltages 202 and the plurality of phase difference signals 200 during the temperature change and the plurality of temperature changes. Is derived. That is, the change amount deriving unit 46 derives the change amount by the following three steps. The first step derives the difference between the control voltage 202 and the phase difference signal 200. The second step derives an equation including parameters by associating the derived difference with a temperature change. In the third step, the amount of change is derived by statistically processing an equation at a predetermined timing and equations at a plurality of subsequent timings. An example of such statistical processing is the least square method. That is, the change amount reflects the influence of a plurality of sampling points. As a result, the accuracy of the amount of change is improved.

The process of the change amount deriving unit 46 will be described in more detail. The oscillation frequency in the oscillating unit 32 is determined by the frequency to be controlled by the reference signal and the frequency reflecting the temperature characteristics in the oscillating unit 32, and is shown as follows.
(Equation 3)
f _OUT (t) = f ₀ (t) + f _OCXO (t)
Here, f _OUT (t) represents an oscillation frequency in the oscillation unit 32, f ₀ (t) represents a frequency to be controlled by the reference signal, and f _OCXO (t) represents a frequency reflecting temperature characteristics in the oscillation unit 32. Therefore, even if the temperature changes, if the influence of the frequency f _OCXO (t) can be reduced, the error included in the oscillation frequency f _OUT (t) is reduced. Therefore, Equation 3 is transformed as follows.
(Equation 4)
f _OCXO (t) = f _OUT (t) −f ₀ (t)

Here, in order to derive a correction value for the control voltage to be input to the oscillating unit 32, f _OUT (t) and f ₀ (t) are not handled as they are, and signals corresponding to these are used. Here, the phase difference signal 200 is used as the oscillation frequency f _OUT (t). The phase difference signal 200 indicates the phase difference between the signal from the frequency divider 34 and the reference signal, but has a characteristic that changes in response to a change in the oscillation frequency. Further, here, the control voltage 202 is used as the frequency f ₀ (t). Since the control voltage 202 is a value obtained by correcting f _OCXO (t), it corresponds to f ₀ (t). As described above, in the first step, the change amount deriving unit 46 derives the difference between the control voltage 202 and the phase difference signal 200. This corresponds to calculating the right side of Equation 4, and as a result, f _OCXO (t) is derived. However, the difference at a predetermined timing is affected by noise and the like. Therefore, the change amount deriving unit 46 defines f _OCXO (t) by an equation that is a linear function of temperature as follows in order to execute statistical processing.
(Equation 5)
f _OCXO (t) = A ・ (t−t _st )

Here, A is the amount of change described above. The temperatures t and t _st are included in the temperature signal 206, where t is the temperature after the change and t _st is the temperature before the change. In order to derive the amount of change, the difference between the control voltage 202 and the phase difference signal 200 is associated, and an equation including the amount of change is derived. This corresponds to the second step described above. Further, the change amount deriving unit 46 performs statistical processing including not only a single equation but also a plurality of equations at different sampling points, and derives a change amount. This corresponds to the third step described above. Further, the least square method is used as statistical processing. The change amount deriving unit 46 outputs the change amount derived as described above to the correction value deriving unit 48 as the correction parameter 204.

The correction value deriving unit 48 updates the correction value based on the temperature change included in the temperature signal 206 and the correction parameter 204. The update is performed based on Equation 5, and the correction value updated in this way corresponds to −f _OCXO (t). As a result, it can be said that such an update uses a temperature change acquired at a timing newer than the timing at which the correction parameter 204 is derived. That is, the latest temperature change can be dealt with. The correction value deriving unit 48 outputs the updated correction value to the correction unit 40. The above update is performed at a predetermined timing.

  FIG. 7 shows the configuration of the change amount deriving unit 46. The change amount derivation unit 46 includes a subtraction unit 50, a parameter equation derivation unit 52, and a processing unit 56. The subtracting unit 50 subtracts the control voltage 202 from the phase difference signal 200. That is, it corresponds to the first step described above. Further, this corresponds to the processing of Equation 4. Here, the subtraction is performed at the same time between the phase difference signal 200 and the control voltage 202. The same applies hereinafter. The subtraction unit 50 outputs the subtraction result to the parameter equation derivation unit 52. The parameter equation deriving unit 52 extracts a temperature change from the temperature signal 206 and derives an equation including parameters. This corresponds to the second step described above. The parameter equation deriving unit 52 outputs a parameter, that is, an equation including the above-described change amount, to the processing unit 56.

  The processing unit 56 performs a least square method on an equation including parameters at a predetermined timing, and derives a change amount. This corresponds to the third step described above. Further, the processing unit 56 outputs the change amount as the correction parameter 204.

  The operation of the receiving apparatus 100 having the above configuration will be described. The satellite signal receiving unit 14 receives signals from a plurality of GPS satellites, and derives a plurality of timing signals and elevation angles, which are reliability information corresponding to them, based on the received signals. The statistical processing unit 16 derives the reference signal by weighting the time components of the timing signal by the elevation angle and then calculating the average of them. The phase comparator 28 calculates the phase difference between the reference signal and the signal from the frequency divider 34, and the loop filter 30 smoothes the phase difference. The correction unit 40 corrects the smoothed phase difference with a correction value. The oscillating unit 32 oscillates a signal while adjusting the oscillation frequency based on the control voltage output from the correcting unit 40. The oscillated signal is input to the phase comparator 28 via the frequency divider 34. The change amount deriving unit 46 derives the change amount while reflecting the temperature change with respect to the difference between the phase difference from the phase comparison unit 28 and the control signal from the correction unit 40. The correction value deriving unit 48 derives a correction value from the change amount and the temperature change, and outputs the correction value to the correction unit 40.

  According to the embodiment of the present invention, the correction value is updated while reflecting the temperature change around the oscillating unit with respect to the difference between the phase difference signal and the control voltage, thereby reducing the change in the oscillation frequency due to the temperature change. Such a control voltage can be derived. In addition, it is possible to derive a highly accurate change amount by considering a plurality of differences and a plurality of temperature changes. Further, by adding a temperature change to the change amount, a correction value that is highly accurate and can follow the change can be derived. Further, since the change amount is derived from the plurality of differences and the plurality of temperature changes by the least square method, the accuracy of the change amount can be increased. Even if a temperature change occurs, the frequency variation corresponding to the temperature characteristic of the oscillation unit is corrected by the correction unit, so that the variation can be reduced. Further, since the control voltage can be corrected, the oscillation frequency can be stabilized. Also, when averaging multiple timing signals, the reference signal can be made highly accurate by weighting with the elevation angle, so that the stability of the oscillation signal based on the reference signal can be increased, and the phase difference signal and control can be performed. The correction value is updated while reflecting the temperature change in the vicinity of the oscillation unit with respect to the difference from the voltage, so that a control voltage that reduces the change in the oscillation frequency due to the temperature change can be derived.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the first to third embodiments of the present invention, the satellite signal receiving unit 14 specifies the elevation angle of a GPS satellite as information related to reliability. However, the present invention is not limited to this, and for example, the satellite signal receiving unit 14 may derive signal strengths corresponding to the received signals as information on reliability. In order to derive the signal strength, the satellite signal receiving unit 14 may use the RSSI of the received signal. At that time, the statistical processing unit 16 weights the time component of the timing signal according to the signal strength. In this case, the elevation angle portion of Equation 1 is replaced with the signal intensity. According to this modification, since the signal with low signal strength has low reliability, the influence of the timing error can be reduced by reducing the weighting. That is, it is only necessary to reduce the weighting for the timing signal that increases the timing error.

Furthermore, the receiving apparatus 100 may use both the elevation angle and the signal strength of the GPS satellite as information on reliability. For example, a threshold value may be provided for the signal strength, and the timing signal corresponding to a signal strength greater than the threshold value may be weighted by the elevation angle. The timing signal t _SVWiTH weighted according to the elevation angle of the satellite is expressed as follows by the timing signal t _SViTH corresponding to the signal intensity _equal to or higher than the threshold value.
(Equation 6)
t _SVWiTH = t _SViTH × ELVi / 90 °
Further, the reference signal t _outTH is indicated by t _SVWiTH as follows.
(Equation 7)
t _outTH = Σ t _SVWiTH / N
According to this modification, the influence of the timing error can be reduced. That is, it is only necessary to reduce the weighting for the timing signal that increases the timing error.

  In the first to third embodiments of the present invention, the statistical processing unit 16 performs averaging as statistical processing. However, the present invention is not limited to this, and for example, processing such as median may be executed. Even in such a case, weighting may be performed before the processing such as the median is executed. According to this modification, various statistical processes can be used. That is, it is only necessary to reduce the influence of a timing signal having a large timing error.

  In the first to third embodiments of the present invention, the receiving device 100 is applied to GPS. However, the present invention is not limited to this, and the receiving device 100 may be applied to a system other than the GPS. For example, GLONASS or GALILEO. According to this modification, the present invention can be applied to various systems. That is, the receiving device 100 may be a satellite navigation receiving device.

  In the first to third embodiments of the present invention, the statistical processing unit 16 weights the time component of the timing signal according to the elevation angle of the GPS satellite, and then between the timing signals corresponding to each of the received signals, The time component is statistically processed. However, the present invention is not limited to this, and for example, statistical processing may be executed by processing other than weighting while using the elevation angle of a GPS satellite as information on reliability. One of them is timing signal selection. That is, statistical processing may be executed after selecting a timing signal corresponding to the elevation angle of a GPS satellite that is somewhat large. According to this modification, the influence of the timing signal corresponding to the signal having a small elevation angle can be reduced. That is, it is only necessary to reduce the influence of a plurality of timing signals that are assumed to contain many errors.

  In the second and third embodiments of the present invention, the statistical processing unit 16 executes weighting as in the first embodiment. However, the present invention is not limited to this. For example, weighting may not be performed. According to this modification, a well-known GPS receiver can be used for the satellite signal receiver 14 and the statistical processor 16. That is, it is only necessary to reduce the change in the oscillation frequency due to the temperature change.

  In the third embodiment of the present invention, the change amount deriving unit 46 derives the change amount as a linear function of the temperature change. However, the present invention is not limited to this. For example, the amount of change may be derived as a quadratic function or higher order function. According to this modification, the correction value can be adjusted more strictly. That is, it is only necessary to derive a correction value corresponding to a change in the oscillation frequency in the oscillation unit 32.

  In the third embodiment of the present invention, the correction unit 40 may include a parameter storage unit after the processing unit 56. The parameter storage unit stores the amount of change previously obtained by the processing unit 56. Furthermore, when storing the change amount, the parameter storage unit associates it with the value of the temperature change when deriving the change amount. In such a configuration, when the derived change value differs greatly every time, the change amount is derived from the temperature change while referring to the temperature change and change amount table stored in the parameter storage unit. According to the present modification, even when the derived change value differs greatly every time, the change amount can be derived. The change amount may be associated with an absolute temperature.

  A modification in which Embodiments 1 to 3 of the present invention are arbitrarily combined is also effective. According to this modification, it is possible to obtain an effect obtained by combining the first to third embodiments.

It is a figure which shows the structure of the receiver which concerns on Example 1 of this invention. 2A to 2E are diagrams showing signal timings to be processed in the statistical processing unit of FIG. It is a figure which shows an example of the process in the statistical process part of FIG. It is a figure which shows the structure of the receiver which concerns on Example 2 of this invention. It is a flowchart which shows the procedure of the time constant control in the control part of FIG. It is a figure which shows the structure of the receiver which concerns on Example 3 of this invention. It is a figure which shows the structure of the fluctuation amount derivation | leading-out part of FIG.

Explanation of symbols

  10 antennas, 14 satellite signal reception units, 16 statistical processing units, 18 PLL, 28 phase comparison units, 30 loop filters, 32 oscillation units, 34 frequency division units, 36 control units, 38 temperature detection units, 40 correction units, 42 updates Unit, 44 temperature detection unit, 46 change amount deriving unit, 48 correction value deriving unit, 100 receiving device.

Claims (13)

A satellite signal receiving unit that receives signals from a plurality of transmission devices, derives timing signals corresponding to the received signals, and information on reliability of the timing signals corresponding to the received signals;
A statistical processing unit that statistically processes the time component of the timing signal between the timing signals corresponding to each of the received signals, while using information related to the reliability corresponding to the timing signal;
An oscillation unit that oscillates a signal on the basis of a statistically processed timing signal,
An oscillation device comprising:   The satellite signal receiving unit derives, as the reliability information, a signal intensity corresponding to each received signal and an elevation angle of the satellite corresponding to each received signal. Oscillation device.   3. The oscillation according to claim 2, wherein the statistical processing unit statistically processes a time component of the timing signal between timing signals corresponding to each of the received signals, using the signal intensity and the elevation angle of the satellite as parameters. apparatus.   The statistical processing unit weights the time component of the timing signal based on the reliability information corresponding to the timing signal, and then statistically analyzes the time component of the timing signal between the timing signals corresponding to the received signals. The oscillation device according to claim 1, wherein the oscillation device is processed. The satellite signal receiving unit derives signal strength corresponding to each of the received signals as information on the reliability,
The oscillation device according to claim 4, wherein the statistical processing unit weights the time component of the timing signal according to the signal strength. The plurality of transmission devices are a plurality of satellites,
The satellite signal receiving unit derives the elevation angle of the satellite corresponding to each of the received signals as information on the reliability,
6. The oscillation device according to claim 4, wherein the statistical processing unit weights a time component of the timing signal according to an elevation angle of the satellite. An oscillation unit that outputs a signal of the adjusted oscillation frequency while adjusting the oscillation frequency by the control voltage;
A phase comparison unit for deriving a phase difference between a signal output from the oscillation unit and a signal to be used as a reference;
A loop filter for smoothing the phase difference derived in the phase comparison unit and feeding back the smoothed phase difference as a control voltage to the oscillation unit;
A control unit for controlling a time constant of the loop filter based on a temperature change around the oscillation unit;
An oscillation device comprising: An oscillation unit that outputs a signal of the adjusted oscillation frequency while adjusting the oscillation frequency by the control voltage;
A phase comparison unit for deriving a phase difference between a signal output from the oscillation unit and a signal to be used as a reference;
A loop filter for smoothing the phase difference derived in the phase comparison unit;
A correction unit that corrects the smoothed phase difference based on a correction value corresponding to a temperature change around the oscillation unit and feeds back the corrected phase difference as a control voltage to the oscillation unit;
The correction value is updated while reflecting the temperature change around the oscillation unit for the difference between the phase difference corrected by the correction unit and the phase difference derived by the phase comparison unit, and the updated correction value An update unit for outputting to the correction unit;
An oscillation device comprising: The update unit
A temperature detection unit for acquiring a temperature change around the oscillation unit;
A change amount deriving unit for deriving a change amount with respect to a temperature change of the correction value from the plurality of differences and the plurality of temperature changes;
A correction value deriving unit that updates a correction value according to the temperature change acquired in the temperature detection unit and the change amount derived in the change amount deriving unit, and outputs the updated correction value to the correction unit;
The oscillation device according to claim 8, further comprising: The change amount derivation unit includes:
Means for deriving a difference between the phase difference corrected in the correction unit and the phase difference derived in the phase comparison unit;
Means for deriving an equation including the amount of change by using the derived difference and the obtained temperature change;
10. The oscillation device according to claim 9, further comprising means for deriving a change amount by statistically processing a plurality of equations including the change amount. An oscillation method that statistically processes time components of timing signals between timing signals derived corresponding to each of received signals from a plurality of transmission devices, and oscillates the signals based on the statistically processed timing signals. There,
It also derives information on the reliability of the timing signal corresponding to each received signal, weights the time component of the timing signal with the information on the reliability corresponding to the timing signal, and then performs statistical processing. How to oscillate. In the oscillator, adjusting the oscillation frequency with the control voltage and outputting a signal of the adjusted oscillation frequency;
Smoothing a phase difference between a signal output from the oscillator and a signal to be used as a reference by a loop filter, and feeding back the smoothed phase difference to the oscillator as a control voltage;
Controlling a time constant of the loop filter based on a temperature change around the oscillator;
An oscillation method comprising: In the oscillator, adjusting the oscillation frequency with the control voltage and outputting a signal of the adjusted oscillation frequency;
Smoothing a phase difference between a signal output from the oscillator and a signal to be used as a reference by a loop filter;
Correcting the smoothed phase difference based on a correction value corresponding to a temperature change around the oscillator, and feeding back the corrected phase difference to the oscillator as a control voltage;
The correction value is updated while reflecting the temperature change around the oscillator with respect to the difference between the corrected phase difference and the phase difference input to the loop filter, and the updated correction value is output to the feedback step. Steps,
An oscillation method comprising:

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