JP3910951B2 - Distance difference detection method and system, and position detection method and system - Google Patents

Description

  The present invention relates to a method and system for performing distance difference detection and position detection, and more particularly, to a method and system for performing distance difference detection and position detection using spread spectrum technology.

As one of the conventional position detection methods using the spread spectrum technique, there is a method of measuring a range from a plurality of points whose positions are known to a point X whose position is unknown, and detecting the position of the point X from the result. . First, a ranging system used in this position detection method will be described with reference to FIGS.
The ranging system shown in FIG. 16 includes a base station 110 and a mobile station 120. Here, the base station 110 includes an oscillator 111, a spread code generator 112a, a mixer 112b, a transmitter 113, a circulator 114, an antenna 115, a receiver 116, a spread code generator 117a, and a mixer 117b. And a synchronization detector 118 and a distance measuring circuit 119. The mobile station 120 includes an antenna 121, a circulator 122, a receiver 123, a frequency converter 124, and a transmitter 125.

In the base station 110, the carrier signal having the frequency F ₁ generated by the oscillator 110 and the spreading code (PN) generated by the spreading code generator 112a are multiplied by the mixer 112b, whereby the direct spreading radio signal having the frequency F ₁ is obtained. Is transmitted to the mobile station 120.
In the mobile station 120 that has received this transmission, the frequency of the received direct spread radio signal is converted from F ₁ to F ₂ by the frequency converter 124, and is transmitted back to the base station 110 as it is.
In the base station 110 that has received the return transmission, the mixer 112b multiplies the received direct spread radio signal (hereinafter referred to as a received signal) and the spread code (PN) generated by the spread code generator 117a to detect synchronization. The synchronization between the received signal and the spread code is detected using the device 118. The detection of the spread code (reception PN) of the received signal in this way is called synchronous detection.

As shown in FIG. 17, the reception PN is delayed by the number of chips corresponding to the propagation time of the direct spread radio signal from the spreading code (transmission PN) of the direct spread radio signal transmitted from the base station 110. Here, “chip” refers to bits of a spread code.
In the base station 110, the distance measurement circuit 119 compares the transmission PN and the reception PN, counts the number of delay chips, and multiplies the delay chip number by the chip width to obtain the propagation time of the direct spread radio signal. A distance between the base station 110 and the mobile station 120 is obtained from this propagation time (see, for example, Non-Patent Document 1).
Therefore, the shorter the chip width of the spread code, the higher the distance measurement accuracy.

Next, a conventional position detection method using this distance measuring system will be described with reference to FIG. The base station 110 is arranged at points A and B whose positions are known. When detecting the position of the mobile station 120 at the point X whose position is unknown using these base stations 110, first, as shown in FIG. A distance d ₁ between X is obtained. Then, as shown in FIG. 18 (b), using a spreading code PN2, determine the distance d ₂ between points B-X. Then, the position of the point X can be detected by calculating the intersection of the circle with the radius d ₁ centered on the point A and the circle with the radius d ₂ centered on the point B.

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
"Spread spectrum communication and its applications", Marubayashi Moto, Nakagawa Masao, Kono Ryuji, The Institute of Electronics, Information and Communication Engineers, ISBN 4-88552-153-X, pp. 14-17

As described above, in the conventional position detection method, it is necessary to use the synchronization detector 118 in order to synchronously detect the spread code of the received signal in the ranging system.
However, since the synchronization detector 118 has a complicated configuration and the circuit operation speed decreases, the chip width of the spread code cannot be shortened. For this reason, there has been a problem that the distance measurement accuracy by the distance measuring system is low, and as a result, the position detection accuracy is low. There is also a problem that it cannot be applied to position detection within a relatively narrow range such as indoors.

  The present invention has been made to solve such a problem, and an object of the present invention is to improve position detection accuracy and to enable position detection even in a relatively narrow range such as indoors.

  In order to achieve such an object, the distance difference detection method according to the present invention uses a spread radio signal having different polarities generated by spreading a carrier signal using the same spreading code as a first point. And a first step of transmitting in synchronization from each of the second points, a second step of receiving the spread radio signal at the third point, and a third step of despreading the received spread radio signal And a fourth step of detecting a difference in distance from each of the first point and the second point to the third point based on the result of the despreading process.

Here, in the fourth step, the distance difference may be detected based on the waveform of the signal obtained by the despreading process.
More specifically, in the fourth step, the distance difference may be detected based on the time difference between the plus side waveform and the minus side waveform of the signal obtained by the despreading process.
In the first step, a spread radio signal is generated while changing the chip width of the spread code. In the fourth step, a positive waveform and a negative waveform appear simultaneously in the signal obtained by the despreading process. The distance difference may be detected based on the chip width at the time.

  In addition, the distance difference detection system according to the present invention includes a pair of base stations that synchronously transmit each of spread radio signals having different polarities generated by spreading the carrier signal using the same spreading code. A mobile station that despreads the received spread radio signal; and a distance difference detector that detects a difference in distance from each base station to the mobile station based on the result of the despread process. And

Here, the distance difference detector may detect the distance difference based on the waveform of the signal obtained by the despreading process.
More specifically, the distance difference detector may detect the distance difference based on the time difference between the plus side waveform and the minus side waveform of the signal obtained by the despreading process.
In addition, each base station generates a spread radio signal while changing the chip width of the spread code, and the distance difference detector simultaneously shows a plus side waveform and a minus side waveform in the signal obtained by the despreading process. The distance difference may be detected based on the chip width at the time.

The position detection method according to the present invention selects a plurality of pairs of two different combinations from at least three known positions, and sets one point of each pair as the first point and the other point as the second point. By using the distance difference detection method described above and detecting the difference in distance from each of the first point and the second point to the third point whose position is unknown in each pair, The position of the point 3 is detected.
Here, different spreading codes may be used for detecting the distance difference in each pair.

In addition, the position detection system according to the present invention includes a plurality of pairs of base stations that transmit in synchronization each of the spread radio signals having different polarities generated by spreading the carrier signal using the same spreading code. And by detecting the difference in distance from each base station to the mobile station for each pair of base stations based on the result of the despreading process and the mobile station that performs despreading processing on the received spread radio signal And a position detector for detecting the position of the mobile station based on the position of the station.
Here, the base station performs spreading processing using a different spreading code for each pair of base stations, the mobile station performs despreading processing using a plurality of spreading codes used by the base station, and the position detector The distance difference may be detected based on the spreading code used for the despreading process.

  In the present invention, spread radio signals having different polarities generated by spreading the carrier signal using the same spreading code are transmitted from the base station at the first point and the base station at the second point, respectively. Transmits synchronously and despreads the spread radio signal received by the mobile station at the third point. Based on the result, the difference in distance from each of the first and second points to the third point is calculated. Detect. In the present invention, when the spread radio signal is subjected to despreading processing, it is not necessary to synchronously detect the spread code of the spread radio signal, so that the chip width of the spread code can be shortened. As a result, the distance difference can be detected with high accuracy.

  In the present invention, the position of a point whose position is unknown is detected using the result of distance difference detection by the above-described method. Thereby, the position detection accuracy can be improved as compared with the conventional case. Also, position detection within a relatively narrow range such as indoors is possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing the overall configuration of the position detection system according to the first embodiment of the present invention. This position detection system is composed of a base station 10 (10a, 10b, 10c, 10d) arranged at points A, B, C, and D whose positions are known, and a mobile station 20 at an unknown point X, respectively. ing.

  Each of the base stations 10a, 10b, 10c, and 10d transmits a unique direct spread radio signal, and the mobile station 20 uses the position of the base stations 10a, 10b, 10c, and 10d as a reference based on the received direct spread radio signal. It detects the position of the user, that is, the position of the point X. More specifically, base stations 10a and 10b, base stations 10b and 10c, and base stations 10c and 10d are paired, and in each pair, transmission and reception between the two base stations and the mobile station 20 are performed. A difference in distance from each position of the base station to the position of the mobile station 20 is detected, and the position of the point X is detected from the obtained result.

  In order to perform time synchronization with each other by wired communication, the base stations 10a and 10b are connected by the cable 40a, the base stations 10b and 10c are connected by the cable 40b, and the base stations 10c and 10d are connected by the cable 40a. They are connected by a cable 40c. When performing time synchronization by wireless communication, the cables 40a to 40c may not be connected. Note that the direct spread radio signal is a signal obtained by performing spread processing as it is without converting the frequency of the carrier signal to a higher frequency band.

FIG. 2 is a block diagram illustrating an example of a basic configuration of the base station 10. The base station 10 includes a carrier signal generation unit 11, a spread processing unit 12, a power amplifier (hereinafter referred to as PA) 13, a bandpass filter (hereinafter referred to as BPF) 14, an antenna 15, and a control unit 16. Have.
Here, the carrier signal generation unit 11 is configured by an oscillator that generates a carrier signal having a predetermined radio frequency.
The spread processing unit 12 is a circuit unit that directly generates a spread radio signal by spreading the carrier signal input from the carrier signal generation unit 11 using a spread code and outputs the signal to the PA 13. For example, the spread code It comprises a generator 12a and a mixer 12b.

The spread code generator 12a is a circuit unit that generates a spread code in synchronization with the first clock f1 and outputs it to the mixer 12b. The spreading code PN is a code string composed of “1” and “−1”. The spreading code generator 12a can also generate a plurality of spreading codes, and has means for generating a spreading code selected by a code selection signal input from the control unit 16. The spread code generator 12a further includes means for starting the generation of a spread code in accordance with the code generation start signal input from the control unit 16.
The mixer 12b is a multiplier that multiplies the carrier signal input from the carrier signal generator 11 and the spread code input from the spread code generator 12a. By this processing, a discontinuous portion is generated in the carrier signal, and the frequency spectrum is spread and widened. The direct spread radio signal generated in this way is output to PA 13.

The PA 13 is an amplifier that amplifies the direct spread radio signal input from the spread processing unit 12 and outputs the amplified signal to the antenna 15 via the BPF 14.
The BPF 14 is a filter that passes the frequency band of the direct spread radio signal.
The antenna 15 is an omnidirectional antenna having no directivity.

  The control unit 16 communicates with another base station that makes a pair with the base station 10 via the cable 40, and controls the spread code generator 12a based on the communication result. In the present embodiment, spreading processing is performed using different spreading codes for each pair of base stations. That is, base stations that make a pair perform spreading processing using the same spreading code, and the spreading code is different from the spreading codes used in other base station pairs. In order to perform such processing, the control unit 16 outputs a code selection signal for selecting a predetermined spreading code to the spreading code generator 12a. In addition, a code generation start signal is output to the spread code generator 12a at the same timing so that the base stations that make a pair perform time synchronization and spread processing.

  The basic configuration of the base station 10 is as described above. However, in the present embodiment, direct spread radio signals representing data having different polarities are transmitted between paired base stations. For example, a direct spread radio signal representing data 1 is transmitted from the base station 10a and data-1 is transmitted from the base station 10b. In the configuration shown in FIG. 2, a direct spread radio signal representing data 1 is generated. In order to generate a direct spread radio signal representing data-1, an inverter may be provided at the output stage of the spread code generator 12a, and the spread code whose polarity is inverted by the inverter may be output to the mixer 12b.

By adopting such a configuration, in the paired base stations, the same spreading code is used to perform time synchronization and spread processing of the carrier signal to generate spread radio signals representing data having different polarities, and the mobile station 20 can be transmitted.
In this embodiment, the example of performing the diffusion process by PSK (Phase Shift Keying) has been described, but the diffusion process may be performed by on-off keying or the like.

FIG. 3 is a block diagram illustrating a configuration example of the mobile station 20. The mobile station 20 includes an antenna 21, a BPF 22, a low noise amplifier (hereinafter referred to as LNA) 23, an oscillator 24, a frequency conversion unit 25, a despreading processing unit 26, a storage unit 27, and a position detection unit 28. have.
Here, the antenna 21 is an omnidirectional antenna having no directivity.
The BPF 22 is a filter that passes the frequency band of the direct spread radio signal among the reception signals received by the antenna 21.
The LNA 23 is an amplifier that amplifies a received signal that has passed through the BPF 22, that is, a direct spread radio signal, with low noise.

The oscillator 24 is a circuit unit that generates a local oscillation signal having a predetermined frequency.
The frequency conversion unit 25 multiplies the direct spread radio signal input from the LNA 23 and the local oscillation signal input from the oscillator 24, converts the direct spread radio signal to a frequency band lower than the carrier signal frequency, and performs despread processing. It is composed of a mixer that outputs to the unit 26.
The despreading processing unit 26 despreads the direct spread radio signal input from the frequency conversion unit 25 sequentially using the same spreading code that is used for the spreading processing in the base stations 10a to 10d, and the processing result and The circuit unit outputs a signal indicating the type of the spread code used in the processing to the position detection unit 28.

The storage unit 27 stores a table indicating the relationship between the type of spreading code and a pair of base stations that use the spreading code. In the table, for example, for different spreading codes PN1, PN2, and PN3, the spreading code PN1 and the pair of base stations 10a and 10b are related, and the spreading code PN2 and the pair of base stations 10b and 10c are related. The spread code PN3 is associated with a pair of base stations 10c and 10d. The storage unit 27 further stores the location of the base stations 10a to 10d, that is, the position information (for example, longitude / latitude information) of the points A to D.
The position detection unit 28 refers to the information stored in the storage unit 27 based on the signal indicating the result of the despreading process and the type of the spread code used in the process, and determines the position of the base stations 10a to 10d. The reference position of the mobile station 20 is detected.

Hereinafter, the despreading processing unit 26 will be further described.
First, the configuration of the despreading processing unit 26 will be described. FIG. 4 is a block diagram illustrating a configuration of an asynchronous despreading demodulator that is an example of the despreading processing unit 26. This asynchronous despreading demodulator includes a sample hold control circuit (S / H control circuit) 31, flip-flop circuits 32a to 32f, N sample hold circuits (S / H) 33a to 33g, and a spread code generator. It comprises a multiplier 34, N multipliers 35 a to 35 g, an adder 36, and a peak detector 37. In FIG. 4, N = 7 and seven sample hold circuits 31a to 31g and seven multipliers 35a to 35g are shown. However, N may be an integer of 2 or more.

Here, the sample hold control circuit 31 is a circuit unit that generates a sample hold control signal by dividing the input first clock f1 by 1 / N and outputs the sample hold control signal to the flip-flop circuit 32a and the sample hold circuit 31a. . The clock f1 is a clock having the same frequency as the clock used for generating the spreading code in the base station 10.
The flip-flop circuits 32a to 32f output the sample hold control signal input from the sample hold control circuit 31 to each of the sample hold circuits 31b to 31g while shifting the sample hold control signal to the right in FIG. 4 in synchronization with the clock f1. It is a circuit part which comprises a shift register.
The sample hold circuits 33a to 33g sample and hold the direct spread radio signal input from the frequency conversion unit 25 according to the sample hold control signal, and the held direct spread radio signal to the multipliers 35a to 35g, respectively. It is the circuit part which outputs.

  The spreading code generator 34 generates a spreading code in synchronization with the second clock f2, and N chips with consecutive spreading codes are shifted in the right direction in FIG. 4 in synchronization with the clock f2. It is a circuit part which outputs to each of the multipliers 35a-35g. Note that the frequency of the clock f2 is sufficiently larger than the frequency of the clock f1. The spread code generator 34 can also generate a plurality of spread codes that are the same as those used for the spread processing in the base stations 10a to 10d, and sequentially generate the plurality of spread codes and output them to the multipliers 35a to 35g. At the same time, a signal indicating the type of spreading code output to the multipliers 35 a to 35 g is output to the position detection unit 28.

The multipliers 35 a to 35 g multiply the direct spread radio signal input from the sample hold circuits 31 a to 31 g and the spread code input from the spread code generator 34 for each corresponding signal, and output to the adder 36. It is a circuit part to do.
The adder 36 is a circuit unit that adds the output signals of the multipliers 35 a to 35 g and outputs the sum to the peak detector 37.

  The peak detector 37 is a circuit unit that detects the peak value of the output signal of the adder 36. When the direct spread radio signal input from the frequency conversion unit 25 is a signal representing the data 1 described above, the direct spread radio signal and the spread code are in phase, and the peak value appears on the plus side. On the other hand, in the case of a signal representing the data-1 described above, the phase is reversed and the peak value appears on the minus side. Therefore, the peak detector 37 outputs a plus peak detection signal to the position detection unit 28 when a peak appears on the plus side, and a minus peak detection signal when a peak appears on the minus side.

Despreading processing using spreading codes PN1 to PN3 by the asynchronous despreading demodulator configured as described above will be described.
The sample hold control signal generated by the sample hold control circuit 31 is a signal obtained by dividing the clock f1 by 1 / N. Therefore, by using a shift register composed of flip-flop circuits 32a to 32f and sequentially outputting the sample and hold control signal to each of the N sample and hold circuits 33a to 33g in synchronization with the clock f1, a direct spread radio signal is obtained. Are sequentially sampled and held in the sample hold circuits 33a to 33g in synchronization with the clock f1.
As a result, the direct spread radio signals are input to the multipliers 35 a to 35 g in the order in which they are output from the frequency converter 25.

Since each of the sample hold circuits 33a to 33g samples and holds the direct spread radio signal for one clock every N clocks, the direct spread radio signal input to each of the multipliers 35a to 35g is set every N clocks. Updated to a new signal.
On the other hand, from the spread code generator 34, first, N consecutive chips of the spread code PN1 are input to each of the multipliers 35a to 35g while shifting in synchronization with the clock f2. At this time, a signal indicating the type of the spread code PN1 output to the multipliers 35a to 35g is output to the position detector 28.

  In the multipliers 35a to 35g, the direct spread radio signal input from the sample hold circuits 33a to 33g and the spread code PN1 input from the spread code generator 34 are multiplied for each corresponding signal, and each multiplication result is obtained. Are added by the adder 36 and output to the peak detector 37. Such an operation is repeatedly performed on the direct spread radio signal input every N clocks of the clock f1 and the spread code PN1 input every clock f2.

When the direct spread radio signal is a signal generated using the spread code PN1, the direct spread radio signal and the spread code PN1 are synchronized at least once in the time interval of the spread code length. At this time, if the direct spread radio signal is a signal representing data 1, the direct spread radio signal and the spread code PN1 have the same phase, and a positive peak value appears in the output signal of the adder 36. On the other hand, in the case of a signal representing data-1, the phase is reversed and a peak value appears on the minus side. These peak values are detected by the peak detector 37, and a plus peak detection signal or a minus peak detection signal is output to the position detection unit 28.
On the other hand, when the direct spread radio signal is not a signal generated using the spread code PN1, no peak value appears in the output signal of the adder 36.
Thus, the despreading process using the spread code PN1 is completed.

  Subsequently, similarly to the despreading process using the spreading code PN1, the despreading process using the spreading codes PN2 and PN3 different from the spreading code PN1 is sequentially performed, and the spreading codes PN2 and PN3 used for the despreading process are sequentially performed. When a signal indicating the type and a peak value are detected, a peak detection signal corresponding to the peak value is output to the position detector 28.

Next, a position detection method using the system including the base stations 10a to 10d and the mobile station 20 described above will be described with reference to FIGS. 5-8 is a figure for demonstrating this position detection method.
First, the distance difference L ₁ between the distance between the points A and X and the distance between the points BX is detected as follows.
As shown in FIG. 5A, a direct spread radio signal (shown as PN1) of data 1 generated using the spread code PN1 is transmitted from the base station 10a arranged at the point A. In synchronization with this, a direct spread radio signal (shown as -PN1) of data-1 generated using the same spread code PN1 is transmitted from the base station 10b arranged at the point B.

  Specifically, the base stations 10a and 10b are operated as follows. First, communication is performed between the control unit 16 of the base station 10a and the control unit 16 of the base station 10b via the cable 40a, and the control unit 16 controls the spread code generator 12a in each of the base stations 10a and 10b. Then, the generation of the same spreading code PN1 is started simultaneously. In the base station 10a, the carrier signal is multiplied by the spread code PN1 as it is to generate a direct spread radio signal of data 1 and transmitted from the antenna 15. On the other hand, in the base station 10b, the polarity of the spread code PN1 is inverted by an inverter, and then the carrier signal is multiplied by the mixer 12b, thereby generating a direct spread radio signal of data-1 and transmitting from the antenna 15. Thereby, direct spread radio signals of data 1 or data-1 generated by performing time synchronization using the same spreading code PN1 are transmitted from the base stations 10a and 10b, respectively.

Direct spread radio signals of data 1 and −1 transmitted from the base stations 10 a and 10 b are received by the mobile station 20 at the point X. In the mobile station 20, the despreading processing unit 26 despreads the received direct spread radio signal. When the despreading process is performed using the spread code PN1, the direct spread radio signal and the spread code PN1 are synchronized, and a peak value appears in the output signal of the adder 36. In the case of the direct spread radio signal of data 1, since the phase is the same when the direct spread radio signal and the spread code PN1 are synchronized, a peak value appears on the plus side. In addition, in the case of the direct spread radio signal of data-1, since the phase is opposite, a peak value appears on the minus side. The direct spread radio signal of data 1 and the direct spread radio signal of data- ₁ are shifted by a radio wave propagation time Δt ₁ corresponding to the distance difference L ₁ between the distance between AX and the distance between BX. Since it is received, the output signal of the adder 36 has a waveform as shown in FIG.

The peak detector 37 of the despreading processing unit 26 outputs a plus peak detection signal when a plus peak value appears in the output signal of the adder 36, and a minus peak detection signal when a minus peak value appears. Are output to the position detector 28, respectively. In the position detection unit 28, a time difference from the input of the positive peak detection signal to the input of the negative peak detection signal and a time difference from the input of the negative peak detection signal to the input of the positive peak detection signal are calculated. measure. For example, the number of clocks of a fixed period signal generated from when one of the positive peak detection signal and the negative peak detection signal is input to when the other is input is counted, and the obtained clock number is multiplied by the clock period. Thus, the time difference is obtained. For example, in the case of position detection in a narrow area such as indoors, the mobile station 20 receives the direct spread radio signal of data 1 and the direct spread radio signal of data -1 as the shorter time difference Δt ₁ among the above time differences. Corresponds to the time difference. Furthermore, considering that both signals are transmitted in time synchronization from the base stations 10a and 10b, it can be said that the time difference Δt ₁ corresponds to the propagation time difference between the two signals. Therefore, the propagation distance difference L ₁ between the two signals is obtained by multiplying the measured time difference Δt ₁ by the propagation speed of the radio wave.

On the other hand, the spread code generator 34 of the despreading processing unit 26 outputs a signal indicating the type of the spread code PN1 currently used for the despreading process to the position detection unit 28. The storage unit 27 stores a table indicating the relationship between the type of spreading code and the pair of base stations that use the spreading code. By referring to this table, it can be seen from the type of spreading code PN1 that the base stations 10a and 10b are directly transmitting the spread radio signal. Further, by referring to the location information of the base stations 10a and 10b stored in the storage unit 27, that is, the position information of the points A and B, the distance difference between the distance between AX and the distance between BX is L. It turns out that it is ₁ .

Next, the distance difference L ₂ between the distance between the points B-X and the distance between the points C-X is similarly detected.
That is, as shown in FIG. 6 (a), a direct spread radio signal (-PN2) of data-1 generated from a base station 10b arranged at a point B using a spread code PN2 different from the spread code PN1. (Shown). In synchronization with this, a direct spread radio signal of data 1 (illustrated as PN2) generated using the same spread code PN2 is transmitted from the base station 10c arranged at the point C. These two direct spread radio signals are received by the mobile station 20 at the point X, and despread using the spread code PN2. As a result, as shown in FIG. 6B, the time difference Δt ₂ between the plus-side peak value and the minus-side peak value appearing in the output signal of the adder 36 is multiplied by the radio wave propagation speed, and the despreading process is performed. used are referring to the table from the class of the spreading code PN2 is, to detect the distance difference L ₂ and the distance between the distance and the C-X between B-X.

Then, the distance difference L ₃ and the distance between the distance between points C-X and the point D-X, to detect similarly.
That is, as shown in FIG. 7 (a), a direct spread radio signal (PN3 and PN3) of data 1 generated from a base station 10c arranged at a point C using a spread code PN3 different from the spread codes PN1 and PN2. (Shown). In synchronization with this, a direct spread radio signal of data-1 generated using the same spread code PN3 (shown as -PN3) is transmitted from the base station 10d arranged at the point D. These two direct spread radio signals are received by the mobile station 20 at the point X, and despread using the spread code PN3. As a result, as shown in FIG. 7B, the time difference Δt ₃ between the plus-side peak value and the minus-side peak value appearing in the output signal of the adder 36 is multiplied by the radio wave propagation speed, and the despreading process is performed. used are referring to the table from the class of the spreading code PN3 is, to detect the distance difference L ₃ and the distance between the distance and the D-X between C-X.

Next, the position detection unit 28 of the mobile station 20 detects the position of the point X where the mobile station 20 is located from the detection results of the distance differences L _{1 to} L ₃ described above. The principle will be described with reference to FIG.
The fact that the distance difference between the distance between AX and the distance between BX is L ₁ is that the point X is on a hyperbola (solid line in FIG. 8) that focuses on the points A and B, and BX the distance difference between the distance between the distance and the C-X between is L ₂ means that are on hyperbolic point X is a point B, and C focus (dashed line in FIG. 8), C- The distance difference L ₃ between the distance between X and the distance between D−X means that the point X is on a hyperbola (the one-dot chain line in FIG. 8) with the points C and D as the focal point. Therefore, it can be seen that the point X is at the intersection of the three hyperbolic curves.

Therefore, the position detection unit 28 obtains the hyperbolic equation shown by the solid line in FIG. 8 from the position information of the points A and B and the distance difference L _1, and FIG. 8 from the position information of the points B and C and the distance difference L ₂ . A hyperbolic equation indicated by a dotted line is obtained, and a hyperbolic equation indicated by a one-dot chain line in FIG. 8 is obtained from positional information of the points C and D and the distance difference L ₃ . Detect position.

In this embodiment, an example in which a time difference between a positive peak value and a negative peak value appearing in the output signal of the adder 36 of the despreading processing unit 26 is measured and the measurement result is used for distance difference detection. However, the phase difference between the plus-side waveform and the minus-side waveform appearing in the output signal of the adder 36 may be measured, and the measurement result may be used for distance difference detection.
Further, different spreading codes PN1, PN2, and PN3 are used to detect the distance difference used for position detection, but the chip rates may be the same or different. However, when using spreading codes having different chip rates, it is necessary to provide a configuration (frequency divider 63 in FIG. 12) that can cope with a change in chip rate, as in a mobile station 60 described later.

[Second Embodiment]
FIG. 9 is a block diagram showing the overall configuration of the position detection system according to the second embodiment of the present invention. In this figure, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG.
The position detection system shown in FIG. 9 includes a base station 50 (50a, 50b, 50c, 50d) disposed at points A, B, C, and D whose positions are known, and a mobile station 60 at an unknown point X. It is composed of The base stations 50a and 50b are connected by a cable 40a, the base stations 50b and 50c are connected by a cable 40b, and the base stations 50c and 50d are connected by a cable 40c. In addition, when performing time synchronization by radio | wireless communication, it does not need to be connected by cable 40a-40c.

FIG. 10 is a block diagram illustrating an example of a basic configuration of the base station 50. In this figure, the same components as those in FIG. 2 are denoted by the same reference numerals as those in FIG.
A base station 50 shown in FIG. 10 adds a circulator 51, a demodulator 52, and a frequency divider 53 to the components of the base station 10 shown in FIG. It is what was used.
Here, the circulator 51 is a circuit unit that outputs the direct spread radio signal that has passed through the BPF 14 to the antenna 15 and outputs the reception signal received by the antenna 15 to the demodulator 52.

The demodulator 52 is a circuit unit that demodulates the received signal input from the circulator 51 and outputs the demodulated signal to the control unit 16a. As will be described later, the mobile station 60 transmits a signal obtained by modulating the chip rate control signal in order to change the chip rate of the spreading code generated by the base station 10. The demodulator 52 demodulates this signal to generate the original chip rate control signal and outputs it to the control unit 16a.
In addition to the function of the control unit 16 in FIG. 2, the control unit 16a controls the frequency division ratio 1 / n (n is an integer) of the frequency divider 53 based on the chip rate control signal input from the demodulator 52. It has a function of generating a frequency division control signal and outputting it to the frequency divider 53.

  The frequency divider 53 is a variable frequency divider having a variable frequency division ratio 1 / n, and divides the first clock f1 by the frequency division ratio 1 / n set by the frequency division control signal to generate a third frequency. A clock f3 is generated and output to the spread code generator 12a. Therefore, the frequency of the clock f3 changes according to the change of the division ratio 1 / n of the frequency divider 53. Since the spread code generator 12a generates a spread code in synchronization with the clock f3, the chip rate and the chip width of the spread code change according to the frequency change of the clock f3. For example, by dividing the frequency dividing ratio of the frequency divider 53 by 1/2 and the frequency of the clock f3 by 1/2 of the frequency of the clock f1, the chip rate of the spread code becomes 1/2 and the chip width becomes 2 Double.

FIG. 11 is a block diagram illustrating a configuration example of the mobile station 60. In this figure, the same components as those in FIG. 3 are denoted by the same reference numerals as those in FIG.
A base station 60 shown in FIG. 11 adds a modulator 61 and a circulator 62 to the components of the mobile station 20 shown in FIG. 3 and despreading processing instead of the despreading processing unit 26 and the position detection unit 28. The unit 26a and the position detection unit 28a are used.

Here, the position detection unit 28a refers to the information stored in the storage unit 27 based on the processing result of the despreading process and the signal indicating the type of spreading code used in the process, and the base stations 50a to 50d. 3 is the same as the position detector 28a in FIG. 3 in that it has a function of detecting the position of the mobile station 60 with reference to the position of. However, an algorithm for realizing this function has a part different from the position detection unit 28 in FIG. In addition, the chip rate control signal is output to the modulator 61 in order to transmit a chip rate control signal for controlling the chip rate of the spreading code generated by the base station 10 to the base station 10.
The modulator 61 is a circuit unit that modulates the chip rate control signal input from the position detection unit 28 a and outputs the modulated chip rate control signal to the circulator 62.
The circulator 62 is a circuit unit that outputs a signal input from the modulator 61 to the antenna 21 and outputs a reception signal received by the antenna 21 to the BPF 22.

For example, as shown in FIG. 12, the despreading processing unit 26a is obtained by adding a frequency divider 63 to the components of the despreading processing unit 26 shown in FIG. In FIG. 12, the same components as those in FIG. 4 are denoted by the same reference numerals as those in FIG.
The frequency divider 63 is a variable frequency divider having a variable frequency division ratio 1 / n (n is an integer), and divides the first clock f1 by the frequency division ratio 1 / n set by the frequency division control signal. Then, the third clock f3 is generated and output to the sample hold control circuit 31 and the flip-flop circuits 32a to 32f. The frequency division control signal is a signal input from the position detection unit 28a, and a frequency divider is used so that the frequency of the frequency-divided clock f3 is the same as the chip rate of the spread code generated by the base station 10. The frequency division ratio 1 / n of 63 is controlled. For example, when the chip rate of the spreading code generated by the base station 10 is halved, the frequency dividing rate of the frequency divider 63 is halved and the frequency of the divided clock f3 is halved. To. Thereby, the despreading process according to the change of the chip rate of the spreading code generated in the base station 10 becomes possible.

Next, with reference to FIG. 13 and FIG. 15, a position detection method using the system including the base stations 50 a to 50 d and the mobile station 60 described above will be described. FIG. 13 and FIG. 15 are diagrams for explaining this position detection method.
First, the distance difference L ₁ between the distance between the points A and X and the distance between the points BX is detected as follows.

The chip rate of the spread code PN1 generated by the base stations 50a and 50b arranged at the points A and B is set. Specifically, in the mobile station 60 at the point X, the position detection unit 28a generates and transmits a chip rate control signal for controlling the chip rate of the spreading code PN1 to a low frequency. In each of the base stations 50a and 50b that have received this chip rate control signal, the control unit 16a sets the frequency division ratio of the frequency divider 53 to a small value of 1 / n ₁ based on the chip rate control signal (ie, n ₁ is set to a large value). As a result, the first clock f1 is peripheral ₁ binary 1 / n, the third clock f3 low frequency is outputted to the spread code generator 12a. As a result, the chip rate of the spread code PN1 is set to the same low frequency as the clock f3. At this time, the chip width of the spread code PN1 increases.

On the other hand, in the mobile station 60, the position detection unit 28a causes the frequency division rate of the frequency divider 63 of the despreading processing unit 26a to be the same as the frequency division rate of the frequency divider 53 of the base stations 50a and 50b. Set to ₁ . As a result, the first clock f1 is peripheral ₁ binary 1 / n, the base station 50a, the third clock f3 the same frequency as the chip rate of the spreading code PN1 generated by 50b are generated, directly received Used to hold samples of spread radio signals. Thereby, the despreading process at the chip rate of the spread code PN1 can be performed.

  In this state, as shown in FIG. 13 (a), each of the base stations 50a and 50b performs time synchronization using the same spreading code PN1 to generate a direct spread radio signal of data 1 and -1, and an antenna. 15 (illustrated as PN1, -PN1). The operations of the base stations 50a and 50b at this time are the same as those in the first embodiment.

  Direct spread radio signals of data 1 and −1 transmitted from the base stations 50 a and 50 b are received by the mobile station 60. In the mobile station 60, the received direct spread radio signal is despread by the despreading processing unit 26a. When the despreading process is performed using the spread code PN1, the direct spread radio signal and the spread code PN1 are synchronized, and a peak value appears in the output signal of the adder 36. However, when the chip width of the spread code PN1 is larger than the propagation time difference between the direct spread radio signals of the data 1 and -1, the despread processing results of both signals are superimposed and peak only on one side of the plus side or the minus side. The value appears. FIG. 15A shows an example in which a peak value appears only on the plus side.

  From the peak detector 37 of the despreading processing unit 26, when a peak value appears in the output signal of the adder 36, a peak detection signal that distinguishes whether the peak value appears on the plus side or the minus side is located. It is output to the detector 28a. In the example of FIG. 15A, only the plus peak detection signal is output. Thus, when only the peak detection signal on one side is output, the position detection unit 28a generates a chip rate control signal for doubling the chip rate of the spread code PN1, and transmits it from the antenna 21. Further, the frequency detector 63 of the despreading processing unit 26a is controlled by the position detection unit 28a so that the despreading processing at the doubled chip rate is possible.

In each of the base stations 50a and 50b that have received the chip rate control signal, the chip rate of the spreading code PN1 is reset to double. As a result, the chip width of the spread code is halved. The specific setting procedure is the same as the procedure when the chip rate is initially set.
In this state, direct spread radio signals of data 1 and −1 generated by the base stations 50 a and 50 b are transmitted, and these signals are received by the mobile station 60 and despread. As a result, as shown in FIG. 15B, when the peak value appears only on one side in the output signal of the adder 36, the chip rate of the spread code PN1 is doubled again and the chip width is halved. To do.

  In this way, when the chip rate of the spread code PN1 is gradually increased and the chip width of the spread code PN1 becomes smaller than the propagation time difference of the direct spread radio signals of data 1 and -1, the result is shown in FIG. Thus, the peak value of the output signal of the adder 36 appears on both the positive side and the negative side. The chip width when the peak value appears on both sides can be regarded as the propagation time difference between the two signals.

In the position detection unit 28a, when the peak detection signals on both sides are input from the peak detector 37 of the despreading processing unit 26, the chip width of the spread code PN1 at that time is multiplied by the propagation speed of the radio wave to propagate both signals. determine the distance difference L _1.
Further, as in the first embodiment, it is the base stations 10a and 10b that transmit the direct spread radio signal, and the locations of the base stations 10a and 10b, that is, the location information of the points A and B. knowing, it is understood the distance difference between the distance between the distance and the B-X between a-X is L _1.
If the peak value of the output signal of the adder 36 appears only on one side even when the chip rate of the spread code PN1 is maximized, the distance between the distance between AX and the distance between BX It is assumed that the difference is 0, that is, the point X is equidistant from each of the points A and B.

Then, the distance difference L ₂ and the distance between the distance and the point C-X between points B-X, to detect in a similar manner using different spreading codes PN2 the spreading code PN1. The distance difference L ₃ and the distance between the distance and the point D-X between points C-X, to detect in a similar manner using different spreading codes PN3 the spreading codes PN1, PN2.
Next, in the same manner as in the first embodiment, the position of the point X where the mobile station 20 is located is detected from the detection results of the distance differences L _{1 to} L ₃ described above.

In the above embodiment, when the direct spread radio signal is subjected to the despreading process, it is not necessary to synchronously detect the spread code of the direct spread radio signal, so that the chip width of the spread code can be significantly shortened. For this reason, the distance difference can be detected with high accuracy. In addition, even when the distance between the known position and the unknown position is short, the distance difference can be detected.
In addition, by detecting the position of a point whose position is unknown using the result of the distance difference detection described above, the position detection accuracy can be improved as compared with the conventional case. Also, position detection within a relatively narrow range such as indoors is possible.

  In the above embodiment, the mobile station 20 (60) is provided with the position detection unit 28 (28a) that detects the position of the point X. The detection unit may be provided in the base station 10 (50). In this case, the signal indicating the result of the despreading process and the type of the spread code PN used in the process may be transmitted from the mobile station 20 (60) to the base station 10 (50).

Further, when detecting the position of the point X where the mobile station 20 (60) is located, the base stations 10a and 10b (50a and 50b), the base stations 10b and 10c (50b and 50c), and the base stations 10c and 10d (50c and 50d). ) Is shown as an example in which distance difference detection is performed in pairs, but the base stations 10a and 10b (50a and 50b), the base stations 10b and 10c (50b and 50c), and the base stations 10c and 10a (50c and 50a) are shown. You may make it perform the distance difference detection which made each pair. In this case, the base station 10a (50a) needs to be configured to generate a direct spread radio signal of data-1 using the spread code PN3.
For position detection, in principle, distance difference detection using three or more pairs of base stations is necessary. However, when two hyperbolas obtained by distance difference detection are in contact, position detection can be performed only by distance difference detection using two pairs of base stations.

  The present invention can be applied not only to distance difference detection and position detection outdoors, but also to distance difference detection and position detection indoors. Indoor position detection can be used to search for luggage in a warehouse or to search for people in an indoor facility. It can also be used to obtain statistical data on the routes that customers walk in museums and department stores.

It is a block diagram which shows the whole structure of the position detection system which concerns on 1st Embodiment. It is a block diagram which shows an example of the basic composition of a base station. It is a block diagram which shows the example of 1 structure of a mobile station. It is a block diagram which shows the structure of the asynchronous despreading demodulator which is an example of a despreading process part. It is a figure for demonstrating the position detection method which concerns on 1st Embodiment. It is a figure for demonstrating the position detection method which concerns on 1st Embodiment. It is a figure for demonstrating the position detection method which concerns on 1st Embodiment. It is a figure for demonstrating the position detection method which concerns on 1st Embodiment.

It is a block diagram which shows the whole structure of the position detection system which concerns on 2nd Embodiment. It is a block diagram which shows an example of the basic composition of a base station. It is a block diagram which shows the example of 1 structure of a mobile station. It is a block diagram which shows the structure of the asynchronous despreading demodulator which is an example of a despreading process part. It is a figure for demonstrating the position detection method which concerns on 2nd Embodiment. It is a figure for demonstrating the position detection method which concerns on 2nd Embodiment. It is a figure for demonstrating the position detection method which concerns on 2nd Embodiment.

It is a block diagram which shows the structure of the ranging system used for the conventional position detection method. It is a figure which shows the relationship between the spreading code of the transmission signal in a base station, and the spreading code of a received signal. It is a figure for demonstrating the conventional position detection method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a-10d, 50, 50a-50d ... Base station, 11 ... Carrier signal generation part, 12 ... Spreading processing part, 12a ... Spreading code generator, 12b ... Mixer, 13 ... Power amplifier (PA), 14 ... Band Path filter (BPF), 15 ... antenna, 16, 16a ... control unit, 20,60 ... mobile station, 21 ... antenna, 22 ... band pass filter (BPF), 23 ... low noise amplifier (LNA), 24 ... oscillator, 25 ... frequency conversion unit, 26, 26a ... despreading processing unit, 27 ... storage unit, 28, 28a ... position detection unit, 31 ... sample hold control circuit (S / H control circuit), 32a to 32f ... flip-flop circuit (FF) ), 33a to 33g ... sample hold circuit (S / H), 34 ... spread code generator, 35a to 35g ... multiplier, 36 ... adder, 37 ... peak detector 40,40A～40c ... cable, 51 ... circulator, 52 ... demodulator, 53 ... divider, 61 ... modulator, 62 ... circulator, 63 ... divider.

Claims (12)

A first step of transmitting spread radio signals having different polarities generated by spreading the carrier signal using the same spreading code in synchronization with each other from the first point and the second point;
A second step of receiving the spread radio signal at a third point;
A third step of despreading the received spread radio signal;
And a fourth step of detecting a difference in distance from each of the first point and the second point to the third point based on a result of the despreading process. Detection method. The distance difference detection method according to claim 1,
In the fourth step, the distance difference detection method is characterized in that the distance difference is detected based on a waveform of a signal obtained by despreading processing. In the distance difference detection method according to claim 2,
In the fourth step, the difference in distance is detected based on a time difference between a plus-side waveform and a minus-side waveform of a signal obtained by the despreading process. In the distance difference detection method according to claim 2,
In the first step, the spread radio signal is generated while changing a chip width of the spread code,
In the fourth step, the difference in distance is detected based on the chip width when a plus-side waveform and a minus-side waveform appear simultaneously in the signal obtained by the despreading process. Method. A pair of base stations that transmit in synchronization each of the spread radio signals of different polarities generated by spreading the carrier signal using the same spreading code;
A mobile station that despreads the received spread radio signal;
A distance difference detection system comprising: a distance difference detector that detects a difference in distance from each of the base stations to the mobile station based on a result of the despreading process. In the distance difference detection system according to claim 5,
The distance difference detector detects the difference in distance based on a waveform of a signal obtained by a despreading process. The distance difference detection system according to claim 6,
The distance difference detector detects the difference in distance based on a time difference between a plus-side waveform and a minus-side waveform of a signal obtained by despreading processing. The distance difference detection system according to claim 6,
Each of the base stations generates the spread radio signal while changing the chip width of the spread code,
The distance difference detector detects the difference in distance based on the chip width when a positive waveform and a negative waveform appear simultaneously in a signal obtained by despreading processing. system. 5. A plurality of pairs of two different combinations selected from at least three points whose positions are known, one point of each pair being a first point and the other point being a second point, Or detecting a difference in distance from each of the first point and the second point to a third point whose position is unknown in each pair. To detect the position of the third point. The position detection method according to claim 9, wherein
A position detection method, wherein different spreading codes are used to detect the difference in distance in each pair. A plurality of pairs of base stations that transmit each of the spread radio signals having different polarities generated by spreading the carrier signal using the same spreading code,
A mobile station that despreads the received spread radio signal;
Based on the result of the despreading process, by detecting the difference in distance from each of the base stations to the mobile station for each pair of the base stations, the position of the mobile station with respect to the position of the base station is determined. With position detector to detect
A position detection system characterized by comprising: The position detection system according to claim 11, wherein
The base station performs spreading processing using a different spreading code for each pair of base stations,
The mobile station performs despreading processing using a plurality of spreading codes used by the base station,
The position detector detects the difference in distance based on a spreading code used for despreading processing.
A position detection system characterized by that.

Images