JP4828949B2 - Speed detection device and wireless device - Google Patents

Description

  The present invention relates to a speed detection device and a wireless device, and more particularly to a speed detection device and a wireless device that receive a wireless reference signal from a communication partner and detect the speed.

  In mobile communication, stable communication is required in various environments that dynamically change, such as a process in which a wireless terminal moves from a stationary state to a high-speed moving state or a process in which an urban environment shifts to a suburban environment. In particular, in a multipath environment with reflected waves and delayed waves passing through a plurality of transmission paths, fading (instantaneous value fluctuation) occurs due to interference, and thus countermeasures are indispensable in mobile communications.

  The wireless terminal has a speed detection function for countermeasures such as multipath fading, Rayleigh fading accompanying movement, and Doppler fading. As a technique for realizing this speed detection function, there is a technique for estimating a speed range from a correlation value obtained by taking an inner product (cos (Cosine)) of pilot signals transmitted from a base station.

  In mobile communication, an automatic frequency control device (see, for example, Patent Document 1) is mounted to synchronize synchronization with a base station. This automatic frequency control device (Automatic Frequency Control, hereinafter AFC) has the following features.

1. Stable control can be performed for Rayleigh fading and Doppler fading during low-speed movement (including when stationary).
2. Stable control is not possible for Rayleigh fading and Doppler fading during high-speed movement.

  In the method of estimating the speed state from the correlation value based on the inner product, it is determined that the low speed state is obtained when the value of the correlation value based on the inner product is close to 1, and the high speed state is found when the correlation value is close to 0. For this reason, the detection accuracy changes significantly depending on the synchronization tuning accuracy of AFC.

  Since the correlation value by the inner product is a change in phase per unit time of the pilot signal, there is a problem that the tracking performance by AFC, that is, the frequency residual of AFC is detected as it is as the inner product value.

The correlation value, moving speed, and fading due to the inner product have the following relationship.
11. In the case of low-speed movement and Rayleigh fading, since the frequency residual due to AFC is small, the correlation value of the inner product is close to 1 and low-speed detection is possible.

  12 In the case of low speed movement and Doppler fading, the AFC follows the Doppler fading. As a result, the frequency residual is reduced. For this reason, the correlation value of the inner product is close to 1 regardless of the speed, and low speed detection is possible.

13. In the case of high-speed movement and Rayleigh fading, since the frequency residual due to AFC is large, the correlation value of the inner product is close to 0 and high-speed detection is possible.
14 In the case of high speed movement and Doppler fading, the AFC follows the Doppler. For this reason, the frequency residual is reduced, and the correlation value of the inner product is close to 1 regardless of the speed, so that the low speed detection becomes difficult and the high speed detection becomes difficult.
JP 2000-77980 A

However, in the method of estimating the speed range with the correlation value based on the inner product, the above 14. As described above, there is a problem that high-speed detection in a Doppler fading environment is difficult.
The present invention has been made in view of such a point, and an object thereof is to provide a speed detection device and a wireless device capable of obtaining an appropriate speed detection result.

  In the present invention, in order to solve the above problem, a reference signal demodulated from a radio signal received from an antenna as shown in FIG. 1 is demodulated into a digital demodulated signal, and the frequency error of the digital demodulated signal is reduced. Correlation value calculation for converting the phase difference per unit time of the digital demodulated signal with a function that monotonously increases or monotonically decreases in proportion to the phase and calculates a correlation value Means 2 is provided, and a speed detecting device is provided that detects the speed based on the correlation value.

  According to such a speed detection device, the automatic frequency control device 1 demodulates the reference signal received from the communication partner into a digital demodulated signal and performs control so that the frequency error is eliminated. The correlation value calculating means 2 calculates the correlation value by converting the phase difference per unit time of the digital demodulated signal with a function that monotonously increases or monotonously decreases in proportion to the phase. Thereby, even if the frequency error of the digital demodulated signal is reduced by the automatic frequency control device 1, a large correlation value can be obtained.

  In the speed detection apparatus of the present invention, the correlation value is calculated by converting the phase difference per unit time of the digital demodulated signal with a monotonically increasing function or a monotonically decreasing function. As a result, even if the frequency error of the digital demodulated signal is reduced by the automatic frequency control device, a large correlation value can be obtained, and an appropriate speed detection result can be obtained.

Hereinafter, the principle of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an outline of a speed detection device. The speed detection device shown in the figure is mounted on, for example, a wireless device and detects the speed of the wireless device. The speed detection device has an automatic frequency control device 1 and a correlation value calculation means 2.

  The automatic frequency control device 1 demodulates a reference signal demodulated from a radio signal received from an antenna and synchronized with a communication partner into a digital demodulated signal, and performs control so that a frequency error of the digital demodulated signal is eliminated.

  The correlation value calculation means 2 calculates the correlation value by converting the phase difference per unit time of the digital demodulated signal controlled by the automatic frequency control device 1 with a function that monotonously increases or monotonously decreases in proportion to the phase. To do.

  In this way, the correlation value is calculated by converting the phase difference per unit time of the digital demodulated signal with a monotonically increasing function or a monotonically decreasing function. Therefore, even if the frequency error of the digital demodulated signal is reduced by the automatic frequency control device, a large correlation value can be obtained, and an appropriate speed detection result can be obtained.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a diagram illustrating a configuration example of a wireless system to which the speed detection device is applied. In the figure, a mobile terminal 10 such as a mobile phone and a base station 20 are shown.

  The terminal 10 and the base station 20 perform wireless communication by, for example, a W-CDMA (Wideband Code Division Multiple Access) method. For example, the terminal 10 demodulates a radio signal from the base station 20 received from an antenna to obtain a CPICH (Common Pilot Channel) pilot signal (reference signal). The terminal 10 synchronizes with the base station based on the pilot signal, and performs radio data demodulation processing and the like.

The terminal 10 is equipped with AFC in order to synchronize synchronization with the base station 20. Here, the AFC mounted on the terminal 10 will be described in detail.
FIG. 3 is a block diagram of AFC. As shown in the figure, the AFC includes a mixer (frequency converter) 31, a demodulator 32, an oscillator controller 33, and an oscillator 34.

  The above-described pilot signal and a frequency signal having a predetermined frequency are input from the oscillator 34 to the mixer 31. The mixer 31 converts the pilot signal into a pilot signal having a predetermined frequency by mixing the pilot signal and the frequency signal.

  The demodulator 32 demodulates the pilot signal output from the mixer 31 and outputs digital demodulated signals I and Q (hereinafter, demodulated pilot signals). The demodulated pilot signal is output to a speed detection circuit described below.

  The oscillator control unit 33 detects a frequency shift (frequency error) of the demodulated pilot signal within a certain time, and controls (feedback control) the oscillation frequency of the oscillator 34 so that the frequency error is eliminated.

The oscillator 34 changes the frequency of the frequency signal output to the mixer 31 under the control of the oscillator control unit 33.
Next, the AFC operation in Doppler fading and Rayleigh fading will be described. First, the AFC operation in Doppler fading will be described.

  FIG. 4 is a diagram for explaining the AFC operation in Doppler fading. F0 shown in the figure indicates the frequency of the demodulated pilot signal when the terminal 10 is stopped. It is assumed that the frequency f0 of the demodulated pilot signal is changed to the frequency f1 shown in the figure due to Doppler fading due to the movement of the terminal 10. AFC controls so that the frequency of the demodulated pilot signal is changed from f0 to f1.

Note that the distance between the frequencies f0 and f1 in the figure increases as the moving speed of the terminal 10 increases.
The difference between the actual frequency f1 of the demodulated pilot signal and the frequency of the demodulated pilot signal (fn in the figure) during the AFC control is called a frequency residual.

Next, the AFC operation in Rayleigh fading will be described.
FIG. 5 is a diagram for explaining the AFC operation in Rayleigh fading. F0 shown in the figure indicates the frequency of the demodulated pilot signal when the terminal 10 is stopped. It is assumed that the frequency f0 of the demodulated pilot signal is changed to the distribution of the frequencies f1 to f2 shown in the figure due to Rayleigh fading due to the movement of the terminal 10.

  The frequency of the demodulated pilot signal varies between the frequencies f1 and f2 shown in the figure due to Rayleigh fading. AFC operates so as to eliminate the frequency error of the demodulated pilot signal that fluctuates.

In addition, the distance between the frequencies f1 and f2 in the figure increases as the moving speed of the terminal 10 increases.
Also, the difference between the actual frequency of the demodulated pilot signal and the frequency of the demodulated pilot signal during the AFC control is called a frequency residual.

  Returning to the description of FIG. The terminal 10 is equipped with a speed detection circuit for measures against Doppler fading and Rayleigh fading accompanying movement. In particular, the accuracy of the speed detection circuit becomes more important as the relative speed between the terminal 10 and the base station 20 increases. For example, when the terminal 10 moves on a bullet train, if the base station 20 is near the bullet train line, the terminal 10 Therefore, the relative speed of the base station 20 increases, and the accuracy of the speed detection circuit for fading countermeasures becomes more important.

  The speed detection circuit calculates a correlation value based on tan (tangent) of the demodulated pilot signal demodulated by the demodulator 32, compares the correlation value with a threshold value, and detects the speed state of the terminal 10. Here, the principle of speed detection of the speed detection circuit will be described.

  FIG. 6 is a diagram for explaining the principle of speed detection of the speed detection circuit. The phase plane is shown in the figure. On the phase plane, a demodulated pilot signal vector V1 at time tn and a demodulated pilot signal vector V2 at time tn + 1 (tn <tn + 1) are shown. The demodulated pilot signals of vectors V1 and V2 are normalized and have a magnitude of 1.

  When the terminal 10 moves, the phase of the demodulated pilot signal changes as indicated by vectors V1 and V2. Therefore, the moving speed of the terminal 10 is estimated from a correlation value (change in phase per unit time) by tan of the angle θ formed by the vectors V1 and V2.

  For example, if the phase change (θ in the figure) of the demodulated pilot signal per unit time (for example, tn + 1−tn in the figure) is large, the correlation value (tan θ) by tan also becomes large. On the other hand, if the phase change of the demodulated pilot signal per unit time is small, the correlation value by tan is small. This is because tan is a function that monotonously increases according to the angle.

  Therefore, if a threshold value is provided and the correlation value by tan is equal to or less than the threshold value, the moving speed of the terminal 10 can be determined to be in a low speed state, and if the correlation value by tan is larger than the threshold value, the moving speed of the terminal 10 is determined. Can be detected in two stages, high speed. Of course, if many threshold values are provided, the state of the moving speed of the terminal 10 can be detected more finely.

  As described in the prior art, conventionally, the moving speed of the terminal 10 is detected based on the correlation value based on the inner product. That is, the moving speed of the terminal 10 is detected based on the size of the arrow A1 in the figure. Here, the inner product is calculated by | V1 | · | V2 | cos θ. Since | V1 | and | V2 | are 1, the inner product = cos θ. Accordingly, it can be determined that the moving speed of the terminal 10 decreases as the correlation value approaches 1 (the arrow A1 approaches 1), and the correlation value approaches 0 (the arrow A1 approaches 0). It can be determined that the moving speed of the terminal 10 is high.

  Next, the influence of the velocity detection of the correlation value by the inner product due to the AFC frequency residual will be described. The following description will be divided into the effects during low-speed movement and under Rayleigh fading, effects during low-speed movement and under Doppler fading, effects during high-speed movement and under Rayleigh fading, and effects during high-speed movement and under Doppler fading. First, the influence during low-speed movement and under Rayleigh fading will be described.

  FIG. 7 is a diagram for explaining the influence of speed detection by the inner product during low-speed movement and under Rayleigh fading. The waveform W1 shown in the figure is a diagram showing the relationship between the AFC frequency residual and the correlation value based on the inner product thereof. Waveform W2 is a diagram illustrating the frequency distribution of the Rayleigh fading of the demodulated pilot signal when the terminal 10 moves at a low speed.

  When the terminal 10 is moving at a low speed, the width of the frequency distribution of Rayleigh fading is small. Therefore, the frequency residual of AFC is also small. That is, the AFC frequency residual is generated in the range of the arrow A11 in the figure.

  The fluctuation of the correlation value due to the AFC frequency residual becomes an arrow A12 in the figure. That is, the fluctuation of the correlation value due to the AFC frequency residual appears in the vicinity of 1. Therefore, the speed detection circuit can appropriately detect the low-speed movement during the low-speed movement and under Rayleigh fading.

Next, the influence during low-speed movement and under Doppler fading will be described.
FIG. 8 is a diagram for explaining the influence of speed detection by the inner product during low-speed movement and under Doppler fading. A waveform W3 shown in the figure is a diagram showing the relationship between the AFC frequency residual and the correlation value based on the inner product thereof. Waveform W4 is a diagram illustrating a frequency distribution of Doppler fading of a demodulated pilot signal when the terminal 10 moves at a low speed. The frequency f0 of the waveform W4 indicates the frequency when the terminal 10 is stopped, and the frequency f1 indicates the frequency when the terminal 10 is moving at a low speed.

  In the case of Doppler fading, the AFC draws the frequency f0 in the figure to the frequency f1 (the frequency f0 is controlled so as to become f1), but the width is small due to low-speed movement, and is shown by the arrow A13. It becomes. The fluctuation of the correlation value due to the inner product due to the frequency residual is small in the vicinity of 1 as indicated by an arrow A14. Therefore, the speed detection circuit can detect low-speed movement appropriately.

  Note that after the AFC pulls the frequency f0 into the frequency f1, the phase difference of the demodulated pilot signal becomes 0 and the correlation value becomes 1. Therefore, after the AFC pulls the frequency f0 to the frequency f1, the speed detection circuit detects the low-speed movement, but the result matches the detection result before the AFC pull-in during the low-speed movement and under Doppler fading. Therefore, it will not be a problem. That is, during low-speed movement and under Doppler fading, the speed detection circuit can properly detect low-speed movement.

Next, the influence during high-speed movement and under Rayleigh fading will be described.
FIG. 9 is a diagram for explaining the influence of speed detection by the inner product during high-speed movement and under Rayleigh fading. A waveform W5 shown in the figure is a diagram showing a relationship between an AFC frequency residual and a correlation value based on its inner product. Waveform W6 is a diagram showing the frequency distribution of Rayleigh fading of the demodulated pilot signal when the terminal 10 moves at high speed.

  When the terminal 10 is moving at a high speed, the width of the frequency distribution of Rayleigh fading increases as indicated by an arrow A15 in the figure. Accordingly, the width of the AFC frequency residual is also increased, and the influence of the correlation value is as indicated by an arrow A16 in the figure. That is, the fluctuation of the correlation value due to the AFC frequency residual becomes large.

Therefore, the speed detection circuit can detect the correlation value near 0 and can detect the high-speed movement of the terminal 10.
Next, the influence during high-speed movement and under Doppler fading will be described.

  FIG. 10 is a diagram for explaining the influence of speed detection by the inner product during high-speed movement and under Doppler fading. A waveform W7 shown in the figure is a diagram showing a relationship between an AFC frequency residual and a correlation value based on an inner product thereof. A waveform W8 is a diagram illustrating a frequency distribution of Doppler fading of a demodulated pilot signal when the terminal 10 moves at high speed. The frequency f0 of the waveform W8 indicates the frequency when the terminal 10 is stopped, and the frequency f1 indicates the frequency when the terminal 10 is moving at high speed.

  In the case of Doppler fading, the AFC draws the frequency f0 in the figure to the frequency f1, but its width is largely the width indicated by the arrow A17 due to high-speed movement. In the case of high-speed movement, the fluctuation of the correlation value due to the inner product due to the frequency residual becomes large as indicated by an arrow A18.

  However, until the AFC pulls in the frequency f0 to the frequency f1, the frequency residual of the AFC is large and the correlation value approaches 0 as indicated by an arrow A19. The correlation value approaches 1 as indicated by arrow A20. Therefore, although the terminal 10 is moving at a high speed, the speed detection circuit detects a low-speed movement.

  Therefore, the speed detection circuit can appropriately detect high-speed movement even during high-speed movement and under Doppler fading by taking a correlation value based on tan. The reason will be described below.

  FIG. 11 is a diagram for explaining the influence of speed detection by tan during high-speed movement and under Doppler fading. A waveform W9 shown in the figure is a diagram showing the relationship between the AFC frequency residual and the correlation value based on the inner product thereof. Waveform W10 is a diagram illustrating a frequency distribution of Doppler fading of a demodulated pilot signal when the terminal 10 moves at high speed. The frequency f0 of the waveform W10 indicates the frequency when the terminal 10 is stopped, and the frequency f1 indicates the frequency when the terminal 10 is moving at high speed.

  In the case of Doppler fading, the AFC draws the frequency f0 in the figure to the frequency f1, but its width is largely the width indicated by the arrow A21 due to high-speed movement. In the case of high speed movement, the fluctuation of the correlation value due to tan due to the frequency residual becomes large as shown by an arrow A22.

The absolute value of the correlation value based on tan is small (approaching 0) when the terminal 10 is moving at a low speed, and is increased (approaching +1 or -1) when the terminal 10 is moving at a high speed.
Until the AFC pulls the frequency f0 to the frequency f1, the frequency residual of the AFC is large, and the correlation value becomes a value close to 1 as indicated by an arrow A23. After the pull-in, the AFC frequency residual becomes 0 and the correlation value becomes 0.

  However, in actual AFC control, the frequency error of the demodulated pilot signal is not completely eliminated, and some error occurs. In particular, when the terminal 10 is moving at high speed, 2. As described above, the AFC cannot perform stable control and an error occurs. That is, the frequency residual of AFC fluctuates in the vicinity of 0 even after the pull-in.

  Here, the tan function is a monotonically increasing function, and has a slope even when the frequency residual is close to 0, as shown by the waveform W9. Accordingly, the correlation value greatly fluctuates with respect to the fluctuation of the frequency residual near zero (for example, the correlation value fluctuates by Δx with respect to the fluctuation Δf near the frequency residual of zero in the figure. Note that the actual tan characteristic Has a more rapid change.) On the other hand, in the inner product (cos function), when the frequency residual is 0, the slope is 0. Therefore, the fluctuation of the correlation value is small with respect to the fluctuation of the frequency residual near 0.

That is, with the correlation value based on tan, it is possible to detect high-speed movement in Doppler fading with respect to the correlation value based on the inner product.
Further, even during the AFC frequency pull-in period (even in a portion other than the vicinity of 0 of the frequency residual), the amount of correlation value variation is large compared to the method using the inner product, so that erroneous determination time is minimized. be able to.

  Furthermore, since the correlation value by tan changes between positive and negative, the speed direction can also be detected. For example, when the frequency residual takes a positive value, the correlation value by tan takes a positive value, and it can be determined that the terminal 10 is approaching the base station 20. On the other hand, when the frequency residual takes a negative value, the correlation value by tan takes a negative value, and it can be determined that the terminal 10 is away from the base station 20.

  Note that the frequency residual when the terminal 10 is moving at a low speed becomes smaller than the fluctuation after the frequency pull-in during the high-speed movement. Therefore, even in the correlation value based on tan, the low-speed movement of the terminal 10 can be detected by providing a threshold value that can detect the low-speed movement.

FIG. 12 shows the tan and cos waveforms. In the figure, the horizontal axis indicates the frequency residual, and the vertical axis indicates the correlation value.
As shown in the figure, the change of the correlation value with respect to the frequency residual of the tan function is larger than the change of the correlation value with respect to the frequency residual of the inner product (cos function). Thereby, the speed detection circuit can appropriately detect the terminal 10 even when the terminal 10 is in a high speed state.

Next, the block configuration of the speed detection circuit will be described.
FIG. 13 is a block diagram of the speed detection circuit. As shown in the figure, the speed detection circuit includes an inner product calculation unit 41, an inner product determination unit 42, a tan calculation unit 43, a tan determination unit 44, and a determination result selection output unit 45.

The inner product calculation unit 41 receives a demodulated pilot signal from the demodulator 32 shown in FIG. The inner product calculation unit 41 calculates a correlation value based on the inner product of the demodulated pilot signals.
The inner product determination unit 42 compares the correlation value based on the inner product calculated by the inner product calculation unit 41 with a threshold value (takes a value of 0 to 1). The inner product determination unit 42 determines the speed state of the terminal 10 based on the comparison result. A plurality of threshold values may be provided as described above.

The tan calculator 43 receives the demodulated pilot signal from the demodulator 32 shown in FIG. The tan calculator 43 calculates a correlation value based on tan of the demodulated pilot signal.
The tan determination unit 44 compares the correlation value by tan calculated by the tan calculation unit 43 with a threshold value (takes a value of 0 to 1). The tan determination unit 44 determines the speed state of the terminal 10 based on the comparison result. A plurality of threshold values may be provided as described above.

The determination result selection output unit 45 selects and outputs one based on the determination result output from the inner product determination unit 42 and the determination result output from the tan determination unit 44.
For example, the determination result selection output unit 45 outputs the determination result of the tan determination unit 44 when the inner product determination unit 42 detects medium speed movement from low speed movement. The determination result selection output unit 45 outputs the determination result of the inner product determination unit 42 when the tan determination unit 44 detects a high-speed movement to a medium-speed movement or a medium-speed movement to a low-speed movement.

  This is because when the terminal 10 is in a low speed state, the correlation value due to the inner product is stable in the vicinity of 1, and when the terminal 10 is in a high speed state, the correlation value due to tan does not change even after the AFC pulls in the frequency. This is because a large and high-speed state can be detected.

  Thus, by selecting and outputting the determination results of the inner product determination unit 42 and the tan determination unit 44, the speed of the terminal 10 can be detected appropriately. Of course, the determination result of the tan determination unit 44 may be output in the entire speed range of the terminal 10. In this case, the speed detection circuit includes only the tan calculation unit 43 and the tan determination unit 44.

Next, the speed detection result with the correlation value by the inner product and the speed detection result with the correlation value by tan will be described.
FIG. 14 is a diagram showing a speed detection result with a correlation value by an inner product and a speed detection result with a correlation value by tan. The left vertical axis in the figure indicates the correlation value. The right vertical axis indicates the moving speed. The horizontal axis indicates time.

A waveform W11 in the figure indicates, for example, the moving speed with respect to the base station when the terminal 10 is moving on the Shinkansen. The moving speed of the terminal 10 is read on the vertical axis on the right side of the figure.
A waveform W12 indicates a correlation value based on the inner product. The correlation value by the inner product is read on the vertical axis on the left side of the figure.

A waveform W13 indicates a correlation value based on tan. The correlation value by tan is read on the vertical axis on the left side of the figure.
A waveform W14 indicates the speed state of the terminal 10 detected by the correlation value based on the inner product.

A waveform W15 indicates the speed state of the terminal 10 detected by the correlation value by tan.
Note that the speed state of the terminal 10 is detected in two stages as shown by the waveforms W14 and W15. A lower level of the waveforms W14 and W15 indicates that the terminal 10 is in a low speed state, and a higher level indicates that the terminal 10 is in a high speed state.

  Assume that the speed of the terminal 10 has changed from 0 km / h to 240 km / h, as shown by the waveform W11. In this case, the correlation value based on the inner product changes as shown by the waveform W12. On the other hand, the correlation value by tan changes as shown by the waveform W13.

  As shown by the waveforms W12 and W13, the correlation value based on tan follows the change in the moving speed of the terminal 10 faster than the correlation value based on the inner product. This is because the fluctuation of the correlation value with respect to the frequency residual of the tan function is large in the fluctuation of the correlation value with respect to the frequency residual of the inner product (cos function).

Therefore, as shown at time t in the figure, the speed detection of the correlation value by tan is output faster than the speed detection of the correlation value by the inner product.
Thus, the correlation value by tan of the demodulated pilot signal is calculated, and the speed state of the terminal 10 is detected. As a result, high-speed movement of the terminal 10 can be detected even in a Doppler fading environment.

  In the above description, the speed of the terminal 10 is detected from the demodulated pilot signal. However, the signal is not limited to the demodulated pilot signal as long as it is a signal for synchronizing with the base station 20. Also, the communication method is not limited to W-CDMA.

  The function for calculating the correlation value is not limited to the tan function, and may be a function that monotonously increases or monotonously decreases in proportion to the phase (phase difference of the demodulated pilot signal).

It is the figure which showed the outline | summary of the speed detection apparatus. It is the figure which showed the structural example of the radio | wireless system to which a speed detection apparatus is applied. It is a block block diagram of AFC. It is a figure explaining the operation | movement of AFC in Doppler fading. It is a figure explaining the operation | movement of AFC in Rayleigh fading. It is a figure explaining the principle of the speed detection of a speed detection circuit. It is a figure explaining the influence of the speed detection by the inner product at the time of low speed movement and under Rayleigh fading. It is a figure explaining the influence of the speed detection by the inner product at the time of low speed movement and under Doppler fading. It is a figure explaining the influence of the speed detection by the inner product at the time of high-speed movement and under Rayleigh fading. It is a figure explaining the influence of the speed detection by the inner product at the time of high-speed movement and under Doppler fading. It is a figure explaining the influence of the speed detection by tan at the time of high-speed movement and under Doppler fading. It is the figure which showed the waveform of tan and cos. . It is a block block diagram of a speed detection circuit. It is the figure which showed the speed detection result in the correlation value by an inner product, and the speed detection result in the correlation value by tan.

Explanation of symbols

1 Automatic frequency controller 2 Correlation value calculation means

Claims (5)

A correlation value calculating means for calculating a correlation value by converting a phase difference per unit time of a digital demodulated signal demodulated from a radio signal received from an antenna by a tangent function;
A speed detection apparatus that detects a speed based on the correlation value.   Further comprising automatic frequency control means for demodulating the digital demodulated signal demodulated from the radio signal received from the antenna, and controlling so that the frequency error of the digital demodulated signal is eliminated;
  The correlation value calculating means uses a digital demodulated signal controlled by the automatic frequency control means as the digital demodulated signal.
  The speed detection apparatus according to claim 1.   A comparison means for comparing the correlation value with a threshold value;
  A speed state determining means for determining a speed state according to a comparison result between the correlation value and the threshold value;
  The speed detection device according to claim 1, further comprising:   Inner product correlation value calculating means for calculating the correlation value by converting the phase difference with a cosine function;
  An inner product speed state determining means for determining a speed state based on the correlation value calculated by the inner product correlation value calculating means;
  Speed state determining means for determining a speed state based on the correlation value calculated by the correlation value calculating means;
  Based on the speed state determined by the inner product speed state determination unit and the speed state determined by the speed state determination unit, the speed state determined by one of the inner product speed state determination unit and the speed state determination unit is Speed state selection means for selecting and outputting;
  The speed detection device according to claim 1, wherein:   A correlation value calculating means for calculating a correlation value by converting a phase difference per unit time of a digital demodulated signal demodulated from a radio signal received from an antenna by a tangent function;
  A wireless device that detects a speed based on the correlation value.

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