JP2010276355A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver determining the propriety of tracking, using separately obtained navigation data. <P>SOLUTION: A receiver may be applied to a GPS receiver or the like. In the receiver, a receiving means receives a satellite signal from a satellite, a frequency conversion means converts the satellite signal to an intermediate frequency, an integration means outputs an integration signal by integrating a reference signal and the converted signal, a reference signal generation means generates the reference signal of a prescribed frequency, and a tracking determination correlation value output means outputs a tracking determination correlation value that is a correlation value between integration signal and the reference signal. A prediction data obtaining means obtains prediction data of the navigation data. The tracking determination means performs comparison processing of comparing the tracking determination correlation value with the prediction data, and performs the tracking determination on the basis of the result of the comparison processing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a receiver that determines a tracking state.

  In general, a satellite signal received from a GPS (Global Positioning System) satellite includes noise. When the receiver performs integration of the converted signal obtained by converting the satellite signal and the PRN code transmitted by the receiver itself, when the satellite signal contains a lot of noise, the receiver It is necessary to lengthen the integration period in order to detect a signal buried in the signal.

  The 1-bit period of the navigation data is 20 msec, which is 20 times the PRN code 1 period (1 msec). Therefore, the receiver must perform integration within 20 msec in order to avoid the influence of code reversal due to the navigation data, and sufficient sensitivity cannot be realized.

  Therefore, a method has been proposed in which the navigation data is estimated by some method and the influence of the data inversion is removed, thereby phase-integrating the satellite signal over a long period of time to increase the sensitivity of the GPS receiver (Patent Document 1). reference).

  In the spread spectrum signal receiving apparatus of Patent Document 1, phase integration is performed using the phase inversion information specified from the estimated navigation data. As a result, the spread spectrum signal receiving apparatus according to Patent Document 1 can specify the code inversion portion, and can achieve integration over a long period while avoiding the influence of the code inversion.

JP 2005-64983 A

  The spread spectrum signal receiving apparatus according to Patent Document 1 can achieve long-term integration using the estimated navigation data, but when the signal power of the satellite signal is extremely low, the satellite signal and the spread spectrum signal receiving apparatus This makes it impossible to detect the phase difference from the signal generated in, and cannot be tracked.

  By the way, if it is determined whether or not the satellite signals acquired from a plurality of satellites are being tracked, it can be determined which satellite signal should be used for positioning, so whether or not tracking can be performed is determined. It is desirable to do. The spread spectrum signal receiving apparatus described in Patent Document 1 is described for achieving high sensitivity using navigation data, but is not described for determining whether or not tracking determination is possible.

  Examples of problems to be solved by the present invention include the above. An object of the present invention is to provide a receiver that determines whether or not tracking is possible using separately acquired navigation data.

  The invention according to claim 1 is a receiver, which is a receiver for receiving a satellite signal, a frequency converter for converting the satellite signal into an intermediate frequency, a signal converted by the frequency converter, a satellite Are integrated with a reference signal for specifying the reference signal, an integration means for generating an integration signal, a reference signal generation means for generating a reference signal of a predetermined frequency, and a tracking that is a correlation value between the integration signal and the reference signal A tracking determination correlation value output means for outputting a determination correlation value, a prediction data acquisition means for acquiring prediction data of navigation data, a comparison process for comparing the tracking determination correlation value and the prediction data, and Tracking determination means for performing tracking determination based on the result of the comparison process.

It is a conceptual block diagram of a receiver. It is a block diagram of a general carrier loop. It is a block diagram of the carrier loop of a prior art document. It is a block diagram of the carrier loop concerning this invention. It is an example of the correlation value when there is no noise. It is an example of the correlation value in the state where signal power is relatively large. It is an example of the correlation value in the state where signal power is relatively small. It is an example of the correlation value in the state where signal power is extremely small. It is a graph which shows the change of signal power. It is an example of a correlation value in case a phase difference is large. It is a figure which shows the relationship between a 1st period and a 2nd period. It is a flowchart of a tracking determination method. It is a figure explaining the start time of a 1st period and a 2nd period.

  One aspect of the present invention is a receiver comprising: a receiving unit that receives a satellite signal; a frequency converting unit that converts the satellite signal into an intermediate frequency; a signal converted by the frequency converting unit; Integration means for integrating a reference signal for identification and generating an integrated signal, reference signal generating means for generating a reference signal of a predetermined frequency, and tracking determination that is a correlation value between the integrated signal and the reference signal A tracking determination correlation value output means for outputting a correlation value for prediction, a prediction data acquisition means for acquiring prediction data of navigation data, and a comparison process for comparing the correlation value for tracking determination with the prediction data. Tracking determination means for performing tracking determination based on the result of the processing.

  The above receiver can be applied to, for example, a GPS receiver. The receiver receives the satellite signal from the satellite, the frequency converting unit converts the satellite signal to an intermediate frequency, and the integrating unit integrates the reference signal and the converted signal, thereby obtaining the integrated signal. The reference signal generating means generates a reference signal having a predetermined frequency, and the tracking determination correlation value output means outputs a tracking determination correlation value that is a correlation value between the integrated signal and the reference signal. The predicted data acquisition means acquires predicted data of navigation data. The prediction data here refers to data obtained by predicting navigation data. The tracking determination means performs a comparison process that compares the correlation value for tracking determination and the prediction data, and performs a tracking determination based on the result of the comparison process.

  In general, in a GPS receiver, as a result of the satellite signal passing through the front end, the output intermediate frequency signal is multiplied by the PRN code corresponding to the reference signal, and the code component is removed. A local carrier signal which is two kinds of reference signals whose phases are shifted by 90 degrees with respect to the signal is generated and multiplied by a VCO (Voltage Controlled Oscillator). An output obtained by passing these through a low-pass filter is obtained as an I correlation value and a Q correlation value.

  The GPS receiver detects the phase difference between the satellite signal and the reference signal by passing the I correlation value and the Q correlation value through a phase comparator, and tracks if the phase difference is small for a certain period of time. Judge. When the I correlation value and the Q correlation value are plotted on the coordinate axis, the angle formed by the straight line consisting of the plotted point and origin and the straight line of the I correlation value axis is the phase difference. Further, when tracking, the sign of the I correlation value corresponds to a navigation data bit.

  Since an error occurs in the actual I correlation value or Q correlation value due to the magnitude of the signal power of the satellite signal or the influence of noise included in the satellite signal, the phase difference cannot be acquired appropriately. However, when the phase difference is small, even if an I correlation value different from the actual I correlation value is calculated due to noise, the sign of the calculated I correlation value is the same as the actual navigation data.

  When the phase difference is large and tracking is not possible, the I correlation value including an error tends to have a code different from the actual navigation data due to the influence of noise included in the satellite signal.

  From this, the receiver according to the present invention is obtained from the sign of the correlation value for tracking determination, which is the correlation value between the integrated signal generated from the satellite signal and the reference signal based on the above tendency, and from an external device or the like. Since it is determined whether or not tracking is performed based on a result of comparison with predicted data that is data obtained by predicting navigation data, it is possible to appropriately perform tracking determination.

  In one aspect of the above receiver, the comparison process outputs a result based on a matching rate between the prediction data in the first period which is a predetermined period and the tracking determination correlation value. As described above, the receiver determines whether or not the tracking is performed based on the matching rate between the prediction data and the tracking determination correlation value in the first period, so that the receiver is very small compared to the first period. Even when tracking is not possible in a long period, it is possible to detect the state of tracking properly. The first period is desirably determined dynamically by design. Further, the threshold value of the coincidence rate should be determined dynamically by design, but if it is around 50%, it is preferably 50% or more (for example, 70% to 80%, etc.) because it is not different from the result of random measurement.

  In another aspect of the above receiver, the comparison processing is performed during a second period that is longer than the first period, and the matching rate in the first period is a threshold value of a matching rate. A result based on the number of times that the matching rate threshold is exceeded is output. In this case, the receiver can avoid judging that tracking is not performed due to the low signal power of the satellite signal received within a certain first period, and only the coincidence rate of a certain first period. Thus, the tracking state can be appropriately determined as compared with the case where the tracking state is determined by.

  In general, the magnitude of the power of a satellite signal to be received fluctuates dynamically due to a change in position or a change in time of a moving body equipped with a receiver. Therefore, even if it is determined whether or not the tracking is based only on the comparison result between the prediction data for one period and the code of the correlation value for tracking determination, there is a high possibility that the determination result has an error.

  However, if it is determined whether or not the matching rate in the first period exceeds the matching rate threshold during the second period, which is a longer period than the first period, As described above, the receiver can appropriately determine the tracking state even when the magnitude of the power fluctuates dynamically.

  In another aspect of the above receiver, the second period starts at a timing when the coincidence rate during the first period exceeds the coincidence rate threshold. In this case, the receiver can improve the possibility of detecting the tracking state by starting at the timing when the coincidence rate during the first period exceeds the threshold.

  In another aspect of the above receiver, the first period is shorter than a carrier loop integration period. In this case, the receiver can avoid that the tracking determination takes time.

  In another aspect of the above receiver, after the first period starts, another first period starts before the first period ends. In this case, the receiver sets the first period in parallel, and the number of tracking determinations increases, so that the possibility of detecting the tracking state can be improved.

  In another aspect of the above receiver, after the second period is started, another second period is started before the second period ends. In this case, the receiver sets the second period in parallel, and the number of tracking determinations increases, so that the possibility of detecting the tracking state can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Conceptual configuration of receiver of the present invention]
A conceptual configuration of a receiver 100 of the present invention is shown in FIG. In this embodiment, the receiver 100 is a GPS receiver. The receiver 100 includes an antenna 10, a front end 20, a carrier loop 30, and a code loop 50. The satellite signal received by the antenna 10 is converted to a frequency that can be easily processed by the front end 20 and input to the carrier loop 30 and the code loop 50. Hereinafter, the signal converted by the front end 20 is also referred to as an “intermediate frequency signal”. The satellite signal of this embodiment is a satellite signal received from a GPS satellite. It is assumed that there are more carrier loops 30 and code loops 50 than the number of satellites required for positioning.

  The carrier loop 30 is for tracking the phase of the carrier of the satellite signal. On the other hand, the code loop 50 is for tracking the phase of the PRN code of the satellite signal. Both operate simultaneously, and the output of the code loop 50 is connected to the carrier loop 30 to remove an extra code component.

  The accumulator 31 in the receiver 100 accumulates the signal S1, which is an intermediate frequency signal, and the PRN code C1 sent from the code loop 50, and as a result, a signal S2 in which the code component is removed from the signal S1 is generated. Is done. The signal S2 is input to the carrier loop 30.

  The receiver 100 according to the present invention is characterized in that it performs a tracking determination that is a determination as to whether tracking is performed within the carrier loop 30 and outputs a tracking determination result. Below, after explaining the structure of a general carrier loop and the structure of the carrier loop of the spread spectrum signal receiving apparatus of Prior Art Document 1, the structure of the carrier loop 30 according to the present invention will be described.

[General carrier loop configuration]
First, FIG. 2 shows a configuration of a carrier loop 300 that is a general carrier loop. The carrier loop 300 is implemented as a Costas loop.

  The carrier loop 300 includes integrators 32 and 33, low-pass filters 34 and 35, a phase comparator 36, a loop filter 37, a VCO (Voltage Controlled Oscillator) 38, and a π / 2 phase shifter 39.

  In the carrier loop 300, the signal S <b> 2 output from the integrator 31 is input to the integrators 32 and 33.

  The integrator 32 receives a signal LS1 that is a local carrier signal generated by the VCO 38. Further, the signal LS1 generated by the VCO 38 is delayed by π / 2 by the π / 2 phase shifter 39, and the signal LS2, which is the delayed local carrier signal, is input to the integrator 33.

  In the integrator 32, the signal S2 and the signal LS1 are integrated. Further, in the integrator 33, the signal LS2 delayed by the π / 2 phase shifter 39 and the signal S2 are integrated.

  As a result of processing the output result of the integrator 32 by the low pass filter 34, an I correlation value which is a correlation value between the signal S2 and the signal LS1 is obtained. Further, as a result of processing the output result of the integrator 33 by the low-pass filter 35, a Q correlation value which is a correlation value between the signal S2 and the signal LS2 is obtained. Then, the I correlation value and the Q correlation value are input to the phase comparator 36.

  The phase comparator 36 detects a phase difference between the signal S2 and the signal LS1 based on the I correlation value and the Q correlation value (hereinafter, the phase difference is also simply referred to as “phase difference”), and uses the phase difference as a loop filter. 37 to the VCO 38. Thereby, the VCO 38 is controlled so that the phase of the signal LS1 output from the VCO 38 is synchronized with the signal S2. A method for detecting the phase difference using the I correlation value and the Q correlation value will be described later.

  The purpose of the carrier loop is to set the Q correlation value to 0 by controlling the phase of the local carrier, which corresponds to setting the phase difference between the signal S2 as the satellite signal and the signal LS2 as the local carrier signal to 0. To do. When the phase difference is approximately 0, the sign of the I correlation value corresponds to a bit of navigation data. The reason why the phase comparator 36 uses not only the Q correlation value but also the I correlation value is to remove the influence of unknown navigation data using the I correlation value and to integrate simple sine waves. This is to replace it. A state where the phase difference between the signal LS2 output from the VCO 38 and the signal S2 is sufficiently small over a certain period is said to be “tracking”.

  Next, FIG. 3 shows a configuration of a carrier loop 400 which is a carrier loop in the spread spectrum signal receiving apparatus of Patent Document 1. The same components as those of the general carrier loop 300 shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  The carrier loop 400 is configured to use predicted navigation data (hereinafter also referred to as “predicted navigation data”) instead of not using the I correlation value. As an example of the predicted navigation data here, there is a signal obtained by performing a predetermined normalization process on the navigation data acquired in the past. In this case, in the carrier loop 400, the I correlation value can be predicted from the predicted navigation data, so that it is possible to track even a weak signal compared to the conventional case.

[Configuration of carrier loop of the present invention]
Next, the configuration of the carrier loop 30 of the present invention is shown in FIG. The same components as those of the general Costas loop 300 shown in FIG. 2 and the carrier loop 400 of Patent Document 1 shown in FIG.

  The carrier loop 30 has a determination unit 40 added to the above-described Costas loop 300, and obtains predicted navigation data from an external server or the like.

  The determiner 40 compares the code of the input I correlation value with the predicted navigation data, and outputs a result indicating whether tracking is performed based on the comparison result. Note that the output result of the determiner 40 is transmitted to positioning calculation means (not shown) of the receiver 100. The positioning calculation means refers to the result output from the determiner 40 and, if tracking is performed, performs positioning using the satellite signal of the satellite corresponding to the carrier loop 30 being tracked. Thus, by outputting the result of whether or not the determiner 40 is tracking, the receiver 100 can specify the satellite signal used for positioning.

  In the present embodiment, the antenna 10 functions as a receiving unit, the front end 20 functions as a frequency converting unit, the integrator 32 and the LPF 34 function as a tracking determination correlation value output unit, and the determination unit 40 includes a tracking determination unit. Function as. Further, the signal S1 functions as an intermediate frequency signal, the PRN code C1 functions as a reference signal, the signal S2 functions as an integrated signal, the signal LS1 functions as a reference signal, and the predicted navigation data functions as predicted data. , I correlation value functions as a tracking determination correlation value.

  Hereinafter, after describing a method of detecting a phase difference using an I correlation value and a Q correlation value performed in the carrier loop 300 or the like, a characteristic part of the present invention will be described.

[Method of detecting phase difference using correlation value]
A method for detecting the phase difference using the I correlation value and the Q correlation value performed by the carrier loop 300 and the like will be described. When a pure satellite signal without noise is received, the I correlation value and the Q correlation value are plotted on the coordinate axes as shown in FIG. In the graph of FIG. 5, the horizontal axis is an I correlation value axis (hereinafter also referred to as “I axis”), and the vertical axis is a Q correlation value axis (hereinafter also referred to as “Q axis”). An angle (angle Ang1 or angle Ang2) formed by a straight line composed of the plotted point (point P1 or point P2) and the origin and the axis of the I correlation value corresponds to a phase difference between the signal S2 and the signal LS1. That is, if the I correlation value and the Q correlation value are known, the phase difference can be known. The phase comparator 36 uses this to detect the phase difference. The distance D1 that is the distance between the point P1 and the origin and the distance D2 that is the distance between the point P2 and the origin are determined by the signal power, and the distances D1 and D2 become longer as the signal power increases.

  The reason why the points are plotted on both the positive and negative of the I axis is due to the unknown navigation data being multiplied. When navigation data is 1, I> 0, and when −1, I <0. In the state where tracking is possible, the navigation data can be detected by looking at the sign of the I correlation value.

  Hereinafter, a correlation value of I> 0 by a satellite signal without noise as shown in FIG. 5 is expressed as “positive true value”, and a correlation value of I <0 is expressed as “negative true value”.

  Actually, since the signal to be processed includes noise, the correlation values are distributed around the true value as shown in FIG. 6 (for example, point P10, point P11, etc.). The magnitude of the spread of this distribution is determined by the noise power, and may be determined by the design of the receiver system and the LPF. The greater the noise power, the greater the distribution spread.

  As described above, since the distance between the true value and the origin is determined by the signal power, the characteristics of the I and Q correlation value distributions are roughly divided into the following three states based on the relative relationship between the noise power and the signal power. Can do.

(State A) State in which signal power is relatively large (State B) State in which signal power is relatively small (State C) State in which signal power is extremely small In state A, as shown in FIG. Distributed. In such a state, a general GPS receiver equipped with the carrier loop 300 refers to the I correlation value to determine whether the plot corresponds to a positive true value or a negative true value. Therefore, it is possible to detect the phase difference from the center of the distribution.

  In the case of state B, the correlation values are distributed as shown in FIG. Correlation values corresponding to positive true values are also distributed in an area where I <0 (for example, point P12). The reverse is also true. In such a situation, it is difficult to detect the phase difference with the above general GPS receiver because it is impossible to determine whether the I correlation value corresponds to a positive true value or a negative true value. It becomes.

  However, if the GPS receiver acquires information about the positive / negative of the corresponding true value of each plot, the center of the distribution can be detected even in the state B, so that the phase difference can be detected.

  As a method of knowing whether the corresponding true value is positive or negative, Patent Document 1 proposes that the navigation data is predicted by some method, and the positive / negative of the plot is not determined from the I correlation value but from the predicted navigation data bit. Has been. As a prediction method, prediction using repetition of navigation data, prediction by acquisition from an external server, and the like have been proposed. As a result, the spread spectrum signal receiving apparatus described in Patent Document 1 is designed to be highly sensitive.

  In state C, the correlation values are distributed as shown in FIG. In such a state, even if the corresponding true value is positive or negative, the point P1 or the point P2 is plotted at a position extremely close to the origin because the signal power is extremely weak. Accordingly, it becomes difficult to appropriately calculate the angle Ang1 or the angle Ang2 shown in FIG. 5, and the general GPS receiver and the spread spectrum signal receiving device described in Patent Document 1 correctly correct the phase difference from the center of the distribution. It becomes difficult to detect.

  When considering a GPS receiver installed in a car navigation system, the intensity of the satellite signal changes dynamically due to changes in the surrounding environment (for example, the passage of time or position change) due to the driving of the car equipped with the car navigation system. To do. FIG. 9 shows an example in which the signal power dynamically changes due to environmental changes such as time passage and position change. The vertical axis represents the intensity of the signal power, and the horizontal axis represents the environmental change.

  In such a change in signal power, the conventional general GPS receiver performs tracking using the satellite signal in the state A, or in the spread spectrum signal receiving device described in Patent Document 1, Tracking is performed using the satellite signal in the state A or the state B.

  Even in a high-sensitivity receiver such as the spread spectrum signal receiver described in Patent Document 1, it is difficult to calculate the phase difference in an environment where the ratio of the state C is large. I can't track. Depending on the prediction method, the predicted navigation data itself may be incorrect. In such a case, the spread spectrum signal receiving apparatus described in Patent Document 1 cannot be tracked. Considering this, it is important to determine whether or not tracking is possible with any GPS receiver.

  In the state A, the GPS receiver can relatively easily determine whether tracking is performed by referring to the relationship between the I and Q correlation values. That is, if the absolute value of the I correlation value is sufficiently larger than the Q correlation value, it can be determined that the tracking is being performed.

  However, when the GPS receiver tries to track the satellite signal in the state B using the predicted navigation data, it is affected by noise, so tracking is determined only by the relationship between the I and Q correlation values. It has been difficult to do so, and no specific tracking determination method has been proposed so far. Further, no specific proposal has been made regarding a determination method in a situation where the signal power dynamically changes as shown in FIG.

[Features of the present invention]
The features of the invention of the present application are divided into the first feature and the second feature, and are described below.

(First feature)
The receiver 100 according to the present invention performs tracking determination based on the matching rate between the predicted navigation data and the code of the I correlation value while tracking is performed using the predicted navigation data. As described above, the receiver 100 performs the tracking determination using the fact that the sign of the I correlation value in the absence of noise corresponds to the navigation data.

  As can be seen from FIG. 7, when the signal power corresponding to the state B is small in phase difference, the correlation value corresponding to the positive true value corresponds to the negative true value in the area of I> 0. The correlation value has a high probability of being distributed in an area of I <0. That is, if the predicted navigation data is correct, there is a high possibility that the predicted navigation data matches the sign of the I correlation value.

  On the other hand, when the phase difference is large in the signal power in the state B, the distribution of correlation values is as shown in FIG. As shown in FIG. 10, since the point P1 or the point P2 is plotted in the vicinity of the Q axis due to the large phase difference, a correlation value corresponding to a positive true value is obtained when affected by noise on the satellite signal. The probability of distribution in an area where I> 0 is low. The reverse is also true. That is, the possibility that the prediction navigation data and the sign of the I correlation value match is reduced.

  Even if the phase difference is small, if the predicted navigation data itself is incorrect, the possibility that the predicted navigation data and the sign of the I correlation value match is low. In such a situation, even if an attempt is made to track using incorrect predicted navigation data, the phase difference becomes large, so it may be judged that tracking is not possible.

  Therefore, the following (1) and (2) can be derived.

  (1) When “the phase difference is small and the predicted navigation data is correct”, there is a high possibility that the predicted navigation data matches the sign of the I correlation value.

  (2) When “the phase difference is large or the predicted navigation data is wrong”, it is unlikely that the predicted navigation data matches the sign of the I correlation value.

  From the above, when the matching rate between the predicted navigation data and the code of the I correlation value in a certain period is higher than the matching rate threshold that is the matching rate threshold, the receiver 100 determines that “continuous in that period. The phase difference is small ”, that is,“ tracking is possible ”. Hereinafter, this period is defined as a “first period”. The longer the first period is, the higher the match rate threshold is, and the higher the coincidence rate threshold is, the smaller the possibility of “false determination” that is actually not tracking but is determined to be tracking determination OK. Become. However, since it is difficult to make a tracking determination despite tracking, it is necessary to appropriately design the length of the first period and the matching rate threshold. In this embodiment, the first period is set to about 100 msec to 150 msec. The coincidence rate threshold value should also be appropriately determined by design, but if it is around 50%, it is preferably 50% or more (for example, 70% to 80%, etc.) because it is not different from the result of random measurement.

  As described above, the determiner 40 of the receiver 100 of the present invention compares the predicted navigation data in the first period and the code of the I correlation value, and performs tracking determination based on the comparison result. In this case, since the receiver 100 performs the tracking determination based on the relationship between the navigation data during tracking and the code of the I correlation value, it is possible to determine whether or not the tracking is appropriately performed. It becomes.

  In addition, since the receiver 100 determines whether or not the tracking is based on the coincidence rate between the predicted navigation data and the code of the I correlation value in the first period, the receiver 100 is very small compared to the first period. Even when the state C is in a short period, it is possible to detect the state of being properly tracked.

(Second feature)
In the receiver 100 of the present invention, the state that “the coincidence rate between the predicted navigation data and the I correlation value code in a certain period is higher than the coincidence rate threshold” is locally multiple times within a longer target period. It is determined that tracking has been performed by detecting the occurrence.

  As shown in FIG. 8, in the state C, the distribution of the I correlation value takes positive and negative almost randomly regardless of the magnitude of the phase difference. That is, even if the predicted navigation data is correct, the matching rate between the predicted navigation data and the sign of the I correlation value is low. Therefore, if the method of the first feature is simply used in an environment in which the signal power dynamically changes, the tracking rate OK is easily reduced when the majority of the first period is in the state C. It may not be possible. If the length of the first period is simply shortened to avoid this, the possibility of erroneous determination increases as described above.

  Therefore, a longer target period than the first period is set, and a state in which the matching rate is locally increased with the length of the first period is a predetermined number of times (hereinafter, the specified number of times is referred to as “number threshold”). It is also determined that tracking has been completed. According to this, the receiver 100 can shorten the first period to reduce the possibility that the state C is included in the first period, and can also reduce the possibility of erroneous determination. This long target period is expressed as a “second period”. Similarly to the first period, the second period should be determined dynamically by design. In this embodiment, the second period is 1 second.

  An example of this technique is shown in FIG. In this example, an example of a condition that “the tracking determination is OK if the first period in which the matching rate exceeds m (matching rate threshold) is included n (number of times threshold) times or more in the second period” is shown. Yes. In the present embodiment, the tracking determination is OK when the first period exceeding the coincidence rate threshold reaches half or more of the first period measurement count included in the second period.

[Tracking judgment method]
Next, the tracking determination method reflecting the first and second features of the present invention will be described with reference to the flowchart shown in FIG. Note that the flowchart shown in FIG. 12 represents processing from the start to the end of the second period.

  First, the determiner 40 sets the counter to 0 (step S1). This counter is a tracking determination counter during the second period. When the predicted navigation data is input from an external server or the like, the receiver 100 acquires the predicted navigation data (step S2). The receiver 100 calculates the I correlation value by processing the result of integrating the signal S2 and the signal LS1 by the integrator 32 with the low-pass filter 34 (step S3). The predicted navigation data and the I correlation value are input to the determiner 40, and the determiner 40 determines whether the predicted navigation data and the sign of the I correlation value match (step S4).

  If the first period has not ended (step S5; No), and if the second period has not ended (step S11; No), the process moves to step S2.

  When the first period has ended (step S5; Yes), the determiner 40 calculates a match rate in the first period (step S6). When the coincidence rate exceeds the coincidence rate threshold (step S7; Yes), the determiner 40 increments the counter (step S8). When the coincidence rate does not exceed the coincidence rate threshold value (step S7; No), the process proceeds to step S11.

  As a result of incrementing the counter, when the counter exceeds the number-of-times threshold (step S9; Yes), the determiner 40 outputs a value corresponding to the tracking determination OK indicating that tracking is performed, and ends the process.

  In step S11, when the second period has ended (step S11; Yes), the counter does not reach the number-of-times threshold during the second period, which means that the determiner 40 is not tracking. A value corresponding to the tracking determination NG is output (step S12), and the process ends.

  As described above, the receiver 100 receives the satellite signal, the frequency converter for converting the satellite signal into the intermediate frequency, the signal converted by the frequency converter, and the reference for specifying the satellite. Integration means for generating the integrated signal, a reference signal generating means for generating a reference signal of a predetermined frequency, and a tracking determination correlation value that is a correlation value between the integrated signal and the reference signal is output. A tracking determination correlation value output means, a prediction data acquisition means for acquiring prediction data of navigation data, a comparison process for comparing the tracking determination correlation value and the prediction data, and tracking based on the result of the comparison process Tracking determination means for performing determination.

  The receiver 100 according to the present invention, when tracking, the code of the correlation value for tracking determination that is the correlation value between the integrated signal generated from the satellite signal and the reference signal, and the navigation data acquired from an external device or the like Since the tracking determination is performed based on the relevance with the predicted data that is the data that predicts the tracking, the tracking determination can be appropriately performed.

[Other embodiments]
In the above-described embodiment, the case has been described in which the determiner 40 determines whether tracking is performed based on the matching rate between the predicted navigation data and the code of the I correlation value in the first period. However, the present invention is not limited to this, and it may be determined whether or not the tracking is simply performed based on whether or not the predicted navigation data and the sign of the I correlation value match.

  In the above-described embodiment, the determination unit 40 has described the case where it is determined that the number of times the coincidence rate threshold in the first period has been exceeded within the second period has been tracked when the number threshold has been reached. The present invention is not limited to this, and it may be determined that tracking is performed when the matching rate threshold value in the first period is exceeded. In this case, if it is determined whether or not the receiver 100 is tracking based on the coincidence rate between the predicted navigation data and the code of the I correlation value in the first period, it is very small compared to the first period. Even when the state C is in a short period, it is possible to detect the state of being properly tracked.

  In the above-described embodiment, the determination unit 40 has described the case where another first period does not start until the first period ends after the first period starts. However, the present invention is not limited to this. As shown in FIG. 13, another first period may be started after a certain first period starts and before the first period ends. In this case, the receiver 100 sets the first period in parallel, and the number of tracking determinations increases, so that the possibility of detecting the tracking state can be improved.

  Although not particularly described in the above-described embodiment, as shown in FIG. 13, the second period may be started from the stage where the coincidence rate within the first period exceeds the coincidence rate threshold. In this case, the receiver 100 can improve the possibility of detecting the tracking state by starting at the timing when the matching rate during the first period exceeds the matching rate threshold.

  Although not particularly described in the above embodiment, as shown in FIG. 13, after the second period is started, another second period may be started before the second period is ended. In this case, the receiver 100 sets the second period in parallel, and the number of tracking determinations increases, so that the possibility of detecting the tracking state can be improved.

  Although not particularly described in the above-described embodiment, it is better to set the period of coincidence determination between the sign of the I correlation value and the predicted navigation data shorter than the integration period of the low-pass filter 34. In the spread spectrum signal receiving apparatus according to Patent Document 1, it has been proposed to use the predicted navigation data to make the integration period longer than 20 msec corresponding to 1 bit of the navigation data. When the low-pass filter 34 is used in this way, if the period for determining the coincidence state of the sign of the I correlation value and the predicted navigation data is made the same as the integration period of the low-pass filter 34, tracking determination takes time.

  Therefore, the receiver 100 can also extract the I correlation value for comparison from the middle of the integration of the low-pass filter 34 and use it to apply the method of the present invention. Thereby, the receiver 100 can appropriately perform tracking determination regardless of the design of the low-pass filter. As a specific example, when the receiver 100 is the low-pass filter 34 and the integration period is 100 msec, an I correlation value is extracted for comparison every 10 msec. In this case, the receiver 100 can avoid that the tracking determination takes time.

  In the above-described embodiments, the case where the predicted navigation data is acquired from the external server has been described. However, the present invention is not limited to this, and the navigation data acquired in the past may be used as the predicted navigation data or received. Navigation data output by another carrier loop 30 included in the aircraft 100 may be acquired as predicted navigation data.

  In the above-described embodiment, the case where the receiver 100 is applied as a GPS receiver has been described. However, the present invention is not limited to this, and is, for example, a receiver in a positioning satellite system other than GPS typified by Galileo. Can also be applied.

DESCRIPTION OF SYMBOLS 10 Antenna 20 Front end 30 Carrier loop 40 Judgment part 50 Code loop 100 Receiver

Claims (7)

Receiving means for receiving satellite signals;
A frequency converting means for converting the satellite signal to an intermediate frequency;
Integrating means for integrating the signal converted by the frequency converting means and a reference signal for identifying a satellite, and generating an integrated signal;
Reference signal generation means for generating a reference signal of a predetermined frequency;
A tracking determination correlation value output means for outputting a tracking determination correlation value which is a correlation value between the integrated signal and the reference signal;
Prediction data acquisition means for acquiring prediction data of navigation data;
A receiver comprising: tracking determination means for performing comparison processing for comparing the tracking determination correlation value with the prediction data and performing tracking determination based on a result of the comparison processing.   The receiver according to claim 1, wherein the comparison process outputs a result based on a matching rate between the prediction data in the first period which is a predetermined period and the tracking determination correlation value.   The comparison process is based on the number of times that the match rate in the first period exceeds a match rate threshold value that is a match rate threshold value during a second period that is longer than the first period. The receiver according to claim 2, wherein the result is output.   The receiver according to claim 3, wherein the second period starts at a timing when the coincidence rate during the first period exceeds the coincidence rate threshold.   The receiver according to any one of claims 1 to 4, wherein the first period is shorter than an integration period of a carrier loop.   The receiver according to claim 2, wherein after the first period is started, another first period is started before the end of the first period.   The receiver according to any one of claims 3 to 6, wherein after the second period is started, another second period is started before the second period ends.

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