JP2010085101A - Positioning system, transmitter and receiver applicable for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precise positioning system even under influences of noise and multipath. <P>SOLUTION: In a mobile station 10, each of the first carrier wave and the second carrier wave which is delayed by a predetermined shift is modulated by the first code which is generated by a code generating part 28 and the second code which is delayed by a predetermined time respectively at a modulating part 34, and the modulated signal is synthesized and transmitted by a synthesis part 44. In a base station 12, the reception wave is demodulated by a demodulating part 78 based on the first reference carrier wave and the second reference carrier wave which is delayed by a predetermined phase. The correlative values between the demodulated two signals and the corresponding codes are computed respectively by a correlative operating part 88. The difference between two computed correlative values is computed by a difference amplifier 96, and the reception time of the radio wave is computed by a reception time detecting part 70 based on the difference between two correlative values. The position of the mobile station 10 is computed by a positioning part 100 based on the reception time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention receives a radio wave transmitted from a transmitter by a receiver and estimates a position of one of the transmitter or the receiver based on a reception time as a reception result, and is applied to the positioning system The present invention relates to a transmitter and a receiver that can be used, and more particularly, to a technique that makes it possible to accurately measure a reception time by performing predetermined phase shift keying modulation and demodulation.

  A method has been proposed in which radio waves transmitted by a transmitter are received by a plurality of receivers, and the position of one of the transmitter or the receiver is estimated based on reception times at each of the plurality of receivers. Specifically, for example, a mobile station whose position is moved by being carried and functioned as one of the transmitter or the receiver, and a fixed position at a known position, which functions as the other of the transmitter or the receiver Radio waves are transmitted to and received from a plurality of base stations. Then, the propagation distance of the radio wave is calculated based on the reception time of the radio wave as the reception result, and the position of the mobile station is calculated using the propagation distance as the distance between each of the plurality of base stations and the mobile station. .

  At this time, since the reception time of the radio wave directly affects the calculated position of the mobile station, it is desirable that the reception time is detected with high accuracy. Therefore, for example, the radio wave transmitted from the transmitter is assumed to include a spread code, and the receiver calculates the correlation value between the received spread code and the replica code of the spread code, and based on the occurrence of the maximum value A technique for detecting the reception time has been proposed. Since the spread code has a property of generating a peak having a high correlation value when the phases are synchronized, it is expected that the reception time can be detected with high accuracy according to such a technique.

  Patent Document 1 discloses a positioning system that measures the position of a mobile station in a mobile communication system that performs communication between a plurality of base stations and a mobile station using code division multiple access communication (CDMA). ing.

JP 2004-301850 A

  By the way, the radio waves transmitted from the transmitter are reflected or diffracted by the influence of buildings, walls, features, metallic fixtures, etc. arranged around the transmitter and receiver, and received by a plurality of different propagation times. Multipath to reach the machine may occur. Under the influence of such multipath, the peak of the correlation value may become dull. Further, when noise occurs in wireless communication between the transmitter and the receiver, the peak correlation value may be dull. In such a case, there is a problem that the reception time of the radio wave may not be detected systematically by detecting the time when the peak of the correlation value is generated.

  The present invention has been made against the background of the above circumstances, and its purpose is to receive a radio wave transmitted from a transmitter, and to determine the position of one of the transmitter or the receiver. In the positioning system that is calculated based on the other position of the transmitter or the receiver and the reception time at the receiver, the correlation value peak becomes dull due to the dullness of the correlation value peak at the receiver, such as in the presence of multipath. Even when it is difficult to detect the reception time of radio waves with high accuracy, it is possible to detect the reception time with high accuracy and to calculate the position based on the detected reception time. It is to provide a simple positioning system, a mobile station applicable to the positioning system, and a base station.

  In order to achieve this object, the invention according to claim 1 is as follows: (a) a receiver receives a radio wave transmitted from a transmitter, and the position of one of the transmitter or the receiver is determined by the transmitter or the receiver. A positioning system that calculates based on the other position of the machine and the reception time at the receiver, (b) the transmitter includes a first code and a second code delayed by a predetermined time from the first code. And (c) modulating the first carrier with the first code generated by the code generator, and using the second code generated by the code generator from the first carrier Modulating a second carrier delayed by a predetermined phase and combining the modulated first carrier and second carrier; (d) a transmitter for transmitting the output from the modulator as a radio wave; (E) the receiver A receiver that receives the radio wave transmitted by the transmitter; and (f) a first reference carrier wave for obtaining a first received signal and a second received signal corresponding to the first code and the second code. A demodulator that demodulates the received wave received by the receiver based on the second reference carrier wave delayed by the predetermined phase from the first reference carrier wave; and (g) the demodulator A first correlation value between the first received signal demodulated based on the first reference carrier and the first code, and a second received signal demodulated based on the second reference carrier by the demodulator A correlation calculation unit for calculating a second correlation value with the second code; and (h) a difference calculation unit for calculating a difference between the first correlation value and the second correlation value calculated by the correlation calculation unit. (I) calculated by the difference calculation unit A reception time detector that calculates a reception time at the receiver of the radio wave transmitted from the transmitter based on a difference between the first correlation value and the second correlation value, and (j) the transmitter or the reception And a positioning unit that calculates one position of the transmitter based on the other position of the transmitter or the receiver and the reception time detected by the reception time detection unit.

  The invention according to claim 8 is: (a) a first code and a code generator for generating a second code delayed by a predetermined time from the first code; and (b) generated by the code generator. The first carrier is modulated by the first code, the second carrier generated by the second code generator is used to modulate the second carrier delayed by a predetermined phase from the first carrier, and after the modulation A modulation unit that combines the first carrier wave and the second carrier wave, and (c) a transmission unit that wirelessly transmits an output from the modulation unit, and (d) any one of claims 1 to 7. It is a transmitter characterized by being applicable to a positioning system.

  The invention according to claim 9 includes: (a) a receiving unit that receives a predetermined radio wave; (b) demodulating a received wave received by the receiving unit based on a predetermined first reference carrier wave; A demodulator that demodulates the received wave based on a second reference carrier delayed by a predetermined phase from one reference carrier; (c) a first received signal demodulated by the demodulator based on the first reference carrier; A correlation calculating unit that calculates a first correlation value with one code and a second correlation value between the second received signal demodulated by the demodulating unit based on the second reference carrier wave and a second code; A difference calculation unit that calculates a difference between the first correlation value calculated by the correlation calculation unit and the second correlation value, and (e) the difference calculation unit according to any one of claims 1 to 7 The receiver is applicable to a positioning system.

  According to the positioning system of claim 1 or the transmitter of claim 8 and the receiver of claim 9, in the transmitter, the code generator delays the first code and a predetermined time from the first code. And the second code is generated. In addition, the modulation unit modulates the first carrier with the first code, modulates the second carrier delayed by a predetermined phase from the first carrier with the second code, The first carrier wave and the second carrier wave are combined, and the output from the modulation unit is transmitted as a radio wave by the transmission unit. On the other hand, in the receiver, the receiver receives the radio wave transmitted by the transmitter of the transmitter, and the demodulator receives the first reference carrier and the first reference carrier delayed by the predetermined phase. The received wave is demodulated based on each of the two reference carriers. The correlation calculation unit calculates a first correlation value between the first received signal demodulated by the demodulation unit based on the first reference carrier wave and the first code, and the demodulation unit calculates the second reference value. A second correlation value between the second received signal demodulated based on the carrier wave and the second code is calculated, and a difference between the first correlation value and the second correlation value is calculated by the difference calculation unit. . Further, the reception time of the radio wave transmitted from the transmitter is calculated at the receiver based on the difference between the first correlation value and the second correlation value calculated by the difference calculation unit by the reception time detection unit. Since the position of one of the transmitter or receiver is calculated by the positioning unit based on the other position of the transmitter or receiver and the reception time detected by the reception time detection unit, Even when it is difficult to accurately detect the reception time of a radio wave based on the peak of the correlation value due to the dullness of the correlation value peak, the reception time can be accurately detected and detected. The position can be calculated based on the received time. Further, since the difference between the first correlation value and the second correlation value is calculated, even if common mode noise that is noise due to a noise source existing between the signal line and the ground is generated, the common The influence of mode noise can be removed.

  Preferably, the code generation unit includes a delay time setting unit that selectively sets the predetermined time from a plurality of preset values. In this way, the predetermined time can be changed by the delay time setting unit in accordance with the calculation accuracy of the target position. Also, at this time, even if the predetermined time is changed, the modulation frequency in the modulation unit is not changed, so that it is possible to improve the position calculation accuracy without increasing the power consumption without increasing the signal processing at the transmitter. it can.

  Preferably, the code generation unit generates the second code by delaying the second code by an integer multiple of a value obtained by dividing the chip period of the second code by an arbitrary natural number as the predetermined time. In this way, it is possible to set a plurality of appropriate predetermined times according to the target position calculation accuracy using a common clock signal.

  More preferably, the reception time detection unit detects the time when the difference between the first correlation value and the second correlation value calculated by the difference calculation unit becomes zero of the radio wave transmitted from the transmitter. It is calculated as the reception time at the receiver. In this case, since the difference value between the first correlation value and the second correlation value changes steeply around zero, the waveform of the first correlation value or the second correlation value becomes dull, and its peak Even when the time cannot be detected with high accuracy, the reception time can be detected with high accuracy from the time when the difference between the first correlation value and the second correlation value becomes zero.

  Preferably, (a) a differential value calculation unit that calculates a differential value of a difference between the first correlation value and the second correlation value calculated by the difference calculation unit, and (b) the reception The time detection unit calculates a reception time at the receiver of the radio wave transmitted from the transmitter based on a time when the differential value calculated by the differential value calculation unit becomes maximum. In this way, the influence of the common mode noise can be removed, and even if the reflected wave due to the multipath effect reaches the receiver before the completion of the direct wave reception at the receiver, The reception time can be calculated with high accuracy.

  Further preferably, the code generation unit generates the second code by shifting the same code as the first code by the predetermined time. In this way, the first code and the second code can be easily generated with a simple configuration using the same code generation unit and delay circuit.

  Further preferably, the code generation unit generates the second code by shifting a code different from the first code by the predetermined time. In this way, when affected by multipath in an environment where multipath occurs, even if one of the first code or the second code is mixed into the other, the correlation value of the other is not mixed. By not being affected, it is possible to reduce the influence of multipath in the difference between the first correlation value and the second correlation value calculated by the difference calculation unit.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining an outline of the configuration of a mobile station positioning system 8 according to an embodiment of the present invention. As shown in FIG. 1, the positioning system 8 includes a mobile station 10 that can move in a preset area, a first base station 12A that is fixed at a known position and has a function of performing wireless communication with the mobile station 10. To four base stations 12D (hereinafter referred to as the base station 12 when the first base station 12A to the fourth base station 12D are not distinguished) and, for example, a CPU, a RAM, a ROM, an input / output interface, etc. It is comprised including the server 14 comprised including what is called a computer provided with. The number of mobile stations 10 is not particularly limited as long as it is one or more. The base station 12 and the server 14 can communicate with each other via a LAN. If the LAN is wired at this time, the base station 12 is connected to the server 14 by the communication cable 18 as shown in FIG. In the mobile station positioning system 8 of the present embodiment, the four base stations 12 of the first base station 12A to the fourth base station 12D, which are a plurality of base stations, receive radio waves transmitted from the mobile station 10, The position of the mobile station 10 is calculated based on the reception result and information about the position of the base station 12 that is known in advance. Accordingly, the mobile station 10 corresponds to the transmitter, and the base station 12 corresponds to the receiver. The mobile station positioning system 8 corresponds to the positioning system.

  FIG. 2 is a functional block diagram for explaining the main part of the functions of the mobile station 10. The code generator 28 includes a PN code generator 30 and a delay circuit 32, and generates a first code and a second code. The PN code generation unit 30 generates a PN (pseudo noise) code which is a kind of spreading code. This code is a code stored in the PN code generation unit 30 in advance. The delay circuit 32 delays and outputs the PN code generated by the PN code generator 30 by a predetermined time. This predetermined time is a delay time set by a delay time setting unit 52 described later. In this way, the code generator 28 outputs two codes: a first code that is a code that is not delayed and a second code that is the same code as that code and is delayed by a predetermined time. Is done.

  FIG. 3 shows an example of two outputs generated by the code generator 28. In FIG. 3, I corresponds to the first code, that is, the code generated by the PN code generating unit 30, and Q is the second code, that is, the code generated by the PN code generating unit 30 and delayed by the delay circuit 32 for a predetermined time. Correspond. ΔT corresponds to the predetermined time in the delay circuit 32. In this way, the code generator 28 generates the second code with a delay (shifted) by a predetermined time ΔT from the first code. T in FIG. 3 is the chip width of the PN code generated by the PN code generator 30.

  The delay time setting unit 52 sets the value of the predetermined time ΔT, which is a time for delaying the PN code in the delay circuit 32. The setting of the predetermined time by the delay time setting unit 52 is determined by transmission from the base station 12, for example. The value of the predetermined time ΔT is set to be a value that is an integral multiple of 1 / n (n is a natural number) of the chip width T of the PN code generated by the PN code generation unit 30, for example.

FIG. 4 is a diagram for explaining the generation of the second code in the delay circuit 32 of the code generator 28. The delay circuit 32 has a plurality of shift registers 33a, 33b, 33c, 33d,... (Hereinafter referred to as “shift register 33” if they are not distinguished from each other). FIG. 4 shows four shift registers 33a, 33b, 33c, and 33d as an example. The shift register 33, for example in response to a rising edge of the inputted clock signal CL (shift pulse), shifts the PN code S _IN is input to the delay circuit 32. Specifically, PN code _{S IN} to the shift register 33a, the output of the shift register 33a by the rise of the clock signal CL, that is, the input signal to the delayed signal output _{S OUT} a, and the shift register 33b. Similarly, the output S _OUT a of the shift register 33a, which is a PN code input to the shift register 33b, is output to the output of the shift register 33b, that is, the delay signal output S _OUT b and the shift register 33c by the rising of the clock signal CL. Input signal. With respect to the shift register 33c and the shift register 33d, delayed output signals S _OUT c and S _OUT d are obtained by the same operation.

Here, the period of the clock signal CL is _{T CL,} as in the 1 / n chip width T of the PN code _{S IN} is input to the delay circuit 32 (n is a natural number), i.e. as _T CL = T / n When set, every time the PN code S _IN is shifted once by the shift register 33, the PN code S _IN is delayed by 1 / n of the chip width T of the PN code S _IN . That is, in FIG. 4, the delayed signal outputs S _OUT a, S _OUT b, S _OUT c, and S _OUT d are each delayed by 1 / n of the chip width T of the PN code S _IN . Specifically, for example, the delay signal output from the shift register 33b outputs _{S OUT} b delay time .DELTA.Tb is, the number of times ΔTb _{= T CL} × m (m is shifted by the delay signal output _{S OUT} b shift register 33 The delay time ΔTc of the delay signal output S _OUT c of the shift register 33c that receives the output S _OUT b of the shift register 33b is ΔTc = T _CL × (m + 1). As described above, the period is _{T CL} of the clock signal CL is, because it is set as _T CL = T / n with a natural number n, the delay time .DELTA.Tb delayed signal output of the shift register 33b is .DELTA.Tb = T The delay time ΔTc of the delay signal output of the shift register 33c is expressed as follows: _CL × m = T × m / n, and ΔTc = T _CL × (m + 1) = T × (m + 1) / n.

Further, the delay circuit 32 has a selector 31 as shown in FIG. 4, and selects one of the outputs S _OUT a, S _OUT b, S _OUT c, and S _OUT d of the plurality of shift registers 33. As an output of the delay circuit 32. In this way, the delay circuit 32 selects and outputs one of the delayed signal outputs shifted by the plurality of different shift registers 33 by the period T _CL of the clock signal CL. In other words, the input signal, which is a PN code generated by the PN code generator 30, can be easily delayed by multiplying the number m of the shift registers 33 shifted by the clock signal cycle T _CL. it can.

  The modulation unit 34 modulates a carrier wave with an input code and outputs the modulated carrier wave. In this embodiment, the modulation unit 34 can perform different modulations with two different inputs. Specifically, the modulation unit 34 includes a carrier wave generation unit 36, a first modulation unit 38, a phase shift unit 40, a second modulation unit 42, and a synthesis unit 44.

  The carrier wave generation unit 36 generates a carrier wave having a predetermined frequency to be used in wireless communication between the mobile station 10 and the base station 12. The carrier wave generated by the carrier wave generation unit 36 is input to the first modulation unit 38 and the phase shift unit 40, respectively. The first modulation unit 38 performs phase modulation on the carrier wave generated by the carrier wave generation unit 36 with the first code generated by the code generation unit 28.

  The phase shifter 40 delays the phase of the carrier wave generated by the carrier wave generator 36 by a predetermined phase, for example, π / 2. The second modulation unit 42 performs phase modulation on the carrier wave delayed by a predetermined phase by the phase shift unit 40 using the second code generated by the code generation unit 28. The carrier wave input from the carrier wave generation unit 36 to the first modulation unit 38 corresponds to the first carrier wave, and the carrier wave input from the carrier wave generation unit 36 to the second modulation unit 42 via the phase shift unit 40 is the second carrier wave. Corresponds to the carrier wave.

  The combining unit 44 combines the carrier wave modulated by the first modulation unit 38 and the carrier wave modulated by the second modulation unit 42 and outputs the combined carrier wave. This output becomes the output of the modulation unit 34. As described above, the phase shift unit 40 delays the input carrier wave by π / 2 and inputs it to the second modulation unit 42, so that the first modulation unit 38, which is two inputs to the synthesis unit 44, is input. And the input from the second modulator 42 are orthogonal to each other. That is, the modulation unit 34 performs quadrature modulation.

  The transmission amplifier 24 amplifies the output of the modulation unit 34 with a predetermined amplification factor, and transmits it by the antenna 22. Here, an antenna suitable for the frequency of the carrier wave generated by the carrier wave generation unit 36 is used. Further, when the distance from the mobile station 10 is the same, the antenna 22 is at least a radio wave so that the base stations 11 and 12 having the same distance from the antenna 22 can receive radio waves with the same strength regardless of the direction from the mobile station 10. An antenna that is omnidirectional with respect to the propagation direction is preferably used. The transmission amplifier 24, the antenna 22, and the like correspond to the transmission unit.

  The transmission / reception switching unit 23 is an antenna sharing device for switching between a radio wave transmission state and a reception state in the mobile station 10. Specifically, when the mobile station 10 is in a transmission state, radio waves can be transmitted by connecting the output of the transmission amplifier 24 to the antenna 22, while the mobile station 10 is in a reception state. Makes it possible to receive radio waves by the antenna 22 by connecting the antenna 22 and an input of a receiving amplifier 26 described later.

  The reception amplifier 26 amplifies the radio wave (reception wave) received by the antenna 22, and a low noise amplifier that can amplify with low noise is preferably used. The demodulator 48 demodulates the reception wave amplified by the reception amplifier 26 using a predetermined carrier wave generated by the carrier wave 36 and extracts a signal wave.

  The controller 50 includes, for example, a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU performs signal processing according to a program stored in the ROM in advance while using a temporary storage function of the RAM. By performing the above, processing such as control related to the operation of the mobile station 10 is executed.

  FIG. 5 is a functional block diagram illustrating the main part of the functions of the base station 12. Among these, the transmission amplifier 64, the transmission / reception switching unit 63, the antenna 62, and the reception amplifier 66 have the same functions as the transmission amplifier 24, the transmission / reception switching unit 23, the antenna 22, and the reception amplifier 26 of the mobile station 10 described above, respectively. is there. The reception amplifier 66, the antenna 62, and the like correspond to the reception unit.

  The transmission signal processing unit 74 generates radio waves to be transmitted from the base station 12. More specifically, a transmission wave is generated by modulating a carrier wave having a predetermined frequency with a signal generated by a controller 72 described later. The transmission wave generated by the transmission signal processing unit 74 is amplified by the transmission amplifier 64 and transmitted from the antenna 62.

  The reception signal processing unit 68 performs demodulation processing on the reception wave received by the antenna 62 and subjected to predetermined amplification by the reception amplifier 66, and extracts a signal wave included in the reception wave. The extracted signal wave is transmitted to a controller 72 and a reception time calculation unit 70 which will be described later.

  FIG. 6 is a functional block diagram for explaining the functions of the received signal processing unit 68 in more detail. The reception signal processing unit 68 includes a demodulation unit 78, a correlation calculation unit 88, and a differential amplifier 96.

  The demodulator 78 performs quadrature demodulation on the received wave. Specifically, the demodulator 78 includes a first demodulator 82, a reference carrier wave generator 80, a phase shift unit 84, and a second demodulator 86. The carrier generation unit 80 generates a reference carrier having the same frequency as the carrier in the received wave, that is, the carrier generated by the carrier generation unit 36 of the mobile station 10. The carrier wave generated by the reference carrier wave generation unit 80 is input to the first demodulation unit 82 and the phase shift unit 84, respectively. The first demodulator 82 demodulates the input received wave with the reference carrier wave generated by the reference carrier wave generator 80. Note that demodulation may be performed after converting the received wave to an intermediate frequency lower than the transmission frequency using a well-known heterodyne method. In this case, the carrier wave generator 80 generates a reference carrier wave having an intermediate frequency.

  The phase shifter 84 delays the phase of the reference carrier generated by the reference carrier generator 80 by a predetermined phase, for example, π / 2. The second demodulator 86 demodulates the input received wave with the reference carrier delayed by a predetermined phase by the phase shifter 84. The reference carrier wave input from the reference carrier wave generator 84 to the first demodulator 82 corresponds to the first reference carrier wave, and is input from the reference carrier wave generator 80 to the second demodulator 86 via the phase shifter 84. The reference carrier corresponds to the second reference carrier.

  As described above, the demodulator 78 demodulates the same received wave with the two reference carriers whose phases are different by π / 2 in the first demodulator 82 and the second demodulator 86, respectively. Corresponds to quadrature demodulation. That is, the output of the first demodulator 82 is an in-phase (I-phase) component signal wave, and the output of the second demodulator 86 is a quadrature (Q-phase) component signal wave. Note that the carrier wave input from the reference carrier wave generation unit 80 to the first demodulation unit 82 corresponds to the first reference carrier wave, and the carrier wave input from the reference carrier wave generation unit 80 to the second demodulation unit 86 via the phase shift unit 84. Corresponds to the second reference carrier.

  The correlation calculation unit 88 generates the two signal waves generated by the demodulation unit 78, that is, the PN code included in each of the I-phase component signal wave and the Q-phase component signal wave, and the PN code generation unit 90. Correlation values with the PN code are calculated respectively. Specifically, the correlation calculation unit 88 includes a PN code generation unit 90, a first correlation value calculation unit 92, and a second correlation value calculation unit 94. The PN code generation unit 90 outputs a previously stored PN code to the first correlation value calculation unit 92 and the second correlation value calculation unit 94. The PN code generated by the PN code generation unit 90 is the same code (replica code) as that generated by the PN code generation unit 30 of the mobile station 10, and is output to the first correlation value calculation unit 92 in this embodiment. The first code to be output and the second code to be output to the second correlation value calculation unit 94 are the same code. The correlation value calculated by the first correlation value calculation unit 92 corresponds to the first correlation value, and the correlation value calculated by the second correlation value calculation unit corresponds to the second correlation value.

  The first correlation value calculation unit 92 and the second correlation value calculation unit 94 respectively calculate the correlation value between the signal wave demodulated by the first demodulation unit 82 and the second demodulation unit 86 and the PN code generated by the PN code generation unit 90. Calculate sequentially. The first correlation value calculation unit 92 and the second correlation value calculation unit 94 have the same configuration, and specifically include a matched filter.

のようにレプリカ符号ａと拡散符号ｂとの相関値Ｒａｂ（ι）を算出する。なお、ａｉおよびｂｉ（ｉ＝１，…，Ｎ）は、それぞれレプリカ符号ａおよび拡散符号ｂのｉ番目のビットの内容であり、ＮはＰＮ符号のビット長である。また、図７に示すように受信信号ｂは１ビット遅延素子により相関値Ｒａｂを算出する毎に１ビットずつシフトされるようにされており、前記（１）式におけるιはこのシフト量の総和を示している。このようにすれば、相関値Ｒａｂ（ι）のピークが生じた際のιの値と受信速度などに基づいて、相関値Ｒａｂ（ι）のピークが生じた際の時刻を信号波の同期時刻として算出することができる。 FIG. 7 is a diagram illustrating an example of a configuration of a matched filter included in each of the first correlation value calculation unit 92 and the second correlation value calculation unit 94. The matched filter calculates an exclusive OR value for each bit of the spread code (received signal) b and the replica code a included in the signal wave obtained by demodulation by the first demodulator 82 or the second demodulator 86, These exclusive OR values are summed by an adder Σ, and further in a correlation calculator

In this way, the correlation value Rab (ι) between the replica code a and the spread code b is calculated. Here, ai and bi (i = 1,..., N) are the contents of the i-th bit of the replica code a and the spreading code b, respectively, and N is the bit length of the PN code. Further, as shown in FIG. 7, the received signal b is shifted by 1 bit every time the correlation value Rab is calculated by the 1-bit delay element, and ι in the equation (1) is the sum of the shift amounts. Is shown. In this way, the time when the peak of the correlation value Rab (ι) occurs based on the value of ι when the peak of the correlation value Rab (ι) occurs and the reception speed, etc., is the synchronization time of the signal wave. Can be calculated as

  FIG. 8 is a diagram illustrating an example of a signal wave input to the first correlation value calculation unit 92 or the second correlation value calculation unit 94 and an output correlation value. When a signal wave is input to the first correlation value calculation unit 92 or the second correlation value calculation unit 94, the PN code included in the signal wave matches the PN code generated by the PN code generation unit 90 (synchronizes). ) The correlation value changes so that the correlation value reaches a peak at time tsync.

  The differential amplifier 96 calculates a difference between two input signals. In this embodiment, the difference between the output of the first correlation value calculation unit 92 and the output of the second correlation value calculation unit 94, specifically For example, an output obtained by subtracting the output of the first correlation value calculation unit 92 from the output of the second correlation value calculation unit 94 is output. The differential amplifier 96 corresponds to the difference calculation unit.

  FIG. 9 is a diagram illustrating the output of the differential amplifier 96 with respect to the output of the first correlation value calculation unit 92 and the output of the second correlation value calculation unit 94 on the same time axis. As described above with reference to FIG. 8, the correlation value outputs of the first correlation value calculation unit 92 and the second correlation value calculation unit 94 are waveforms having a synchronization time as a peak, for example, the examples of FIGS. 8 and 9. In other words, it is monotonically increasing until the synchronization time, and decreases in a minor manner when the synchronization time elapses. As described above, since the predetermined time for delaying the PN code by the delay circuit 32 in the code generation unit 28 of the mobile station 10 is ΔT, the peak of the correlation value output of the first correlation value calculation unit 92 as shown in FIG. The difference between the synchronization time that is the time when the correlation value is output and the synchronization time of the correlation value output of the second correlation value calculation unit 94 is ΔT. On the other hand, when attention is paid to the output of the operational amplifier 96 obtained by subtracting the output of the first correlation value calculation unit 92 from the output of the second correlation value calculation unit 94, the time when the output changes from negative to positive (zero cross) is T + ΔT / 2. is there.

  Returning to FIG. 5, the reception time calculation unit 70 outputs the reception signal processing unit 68, specifically, the output of the first correlation value calculation unit 92 calculated by the differential amplifier 96 and the second correlation value calculation unit 94. Based on the difference from the output, it is detected as the reception time of the received radio wave. Specifically, the reception time calculation unit 70 receives the time when the difference value between the output of the first correlation value calculation unit 92 and the output of the second correlation value calculation unit 94 calculated by the differential amplifier 96 becomes zero. Detect as time. The reception time calculation unit 70 corresponds to the reception time detection unit.

  By the way, as a method for detecting the reception time of the radio wave based on the correlation value of the PN code, a method is often used in which the time when the correlation value peak occurs is the reception time. In this method, it is necessary to detect the time at which the peak is generated from the correlation value output exemplified as the correlation value calculation unit output in FIG. 8, and in particular, depending on the positioning accuracy required for the mobile station positioning system 8, ns (nano Detection in units of seconds) is required. However, when the wireless communication between the mobile station 10 that transmits the PN code and the base station 12 that receives the PN code is not good, as shown in FIG. An influence occurs (arrow portion in FIG. 10A), and an error is likely to occur in the detection of the time when the waveform peak occurs.

  On the other hand, the radio communication between the mobile station 10 and the base station 12 is not good, and the waveform of the correlation value output in each of the first correlation value calculation unit 92 and the second correlation value calculation unit 94 is shown in FIG. 10B, the waveform of the difference value between the output of the first correlation value calculation unit 92 and the output of the second correlation value calculation unit 94 calculated by the differential amplifier 96 is as shown in FIG. It becomes like this. As shown in FIG. 10B, when the entire waveform is viewed, even if dullness or noise occurs, the change is steep in the vicinity of the zero cross (arrow part in FIG. 10A). As described above, the reception time calculation unit 70 detects the time when the output of the differential amplifier 96 becomes zero as the reception time, so even if the waveform of the correlation value output becomes dull, the accuracy of the reception time Good detection is easy.

  Further, since the output of the differential amplifier 96 is a difference between the output of the first correlation value calculation unit 92 and the output of the second correlation value calculation unit 94, the output of the first correlation value calculation unit 92 and the second output due to disturbance or the like. The influence of the fluctuation component (common mode noise) that occurs in common with the output of the correlation value calculation unit 94 can be removed. Therefore, the value of the reception time calculated by the reception time calculation unit 70 based on the output of the differential amplifier 96 is not easily affected by the common mode noise.

  As shown in FIG. 9, in the output of the differential amplifier 96, the smaller the value of ΔT, the steeper the change in the waveform near the zero cross. Detection is easy and detection accuracy is improved. However, if the value of ΔT is decreased, the differential output itself of the differential amplifier 96 is decreased, and is easily affected by noise. Therefore, the predetermined time ΔT of the delay circuit 32 by the delay time setting unit 52 of the mobile station 10 is determined by selecting an appropriate one from a plurality of preset values in consideration of these effects, for example. Done.

  The controller 72 includes, for example, a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU performs signal processing according to a program stored in the ROM in advance while using a temporary storage function of the RAM. By performing the above, processing such as control related to the operation of the base station 12 is executed.

  The communication interface 76 transmits / receives necessary information to / from the server 14 and other base stations 12 connected by the communication cable 18.

  FIG. 11 is a functional block diagram for explaining a main part of the functions of the server 14. Among these, the communication interface 98 transmits and receives necessary information to and from the base station 12 connected by the communication cable 18. In the present embodiment, the server 14 does not have a wireless communication function, and the mobile station 10 does not have a wired communication function via the communication cable 18. It is transmitted via any one of the base stations 12 configured to have both a wireless communication function and a wired communication function.

  The positioning unit 100 moves based on the reception time of the radio wave from the mobile station 10 calculated by the reception time calculation unit 70 of each base station 12 and information about the position of each base station 12 stored in advance. The position of the station 10 is calculated.

ここで、Ｔｒ１、Ｔｒ２、Ｔｒ３およびＴｒ４（ｓｅｃ）はそれぞれ、第１普通基地局１２Ａ、第２普通基地局１２Ｂ、第３基地局１２Ｃ、および第４普通基地局１２Ｄの受信時刻算出部７０において検出される受信時刻であり、Ｔｓは移動局１０の無線部２２における電波の送信時刻である。すなわち、前記（２）式の右辺は、第１普通基地局１２Ａ、第２普通基地局１２Ｂ、第３普通基地局１２Ｃ、および第４普通基地局１２Ｄのそれぞれと移動局１０との間の電波の伝搬時間に電波の速度ｃを乗ずることによって得られる電波の伝搬距離の二乗を表わしている。前記（２）式はｘ、ｙ、Ｔｓを未知数とした連立方程式である。（２）式よりＴｓを消去すると以下の式（３）となる。

測位部１００は前記（２）式もしくは（３）式を解くことにより、移動局１０の位置（ｘ，ｙ）を算出する。なお、前記（２）式もしくは（３）式を解くにあたり、それらの全ての式を連立させて解く必要はなく、解を算出するのに最低限の数の式により解いてもよい。 FIG. 12 is a diagram for explaining the principle of calculating the position of the mobile station 10 by the positioning unit 100. The coordinates representing the position of the mobile station 10 are (x, y), the coordinates representing the position of the first ordinary base station 12A are (x _B1 , y _B1 ), and the coordinates representing the position of the second ordinary base station 12B are (x _B2 , y _B2 ), the coordinates representing the position of the third ordinary base station 12C are (x _B3 , y _B3 ), and the coordinates representing the position of the fourth base station 12D are (x _B4 , y _B4 ). Is obtained by the following equation (2). Note that the arrangement of base stations 12 in FIG. 12 is different from that in FIG.

Here, Tr1, Tr2, Tr3, and Tr4 (sec) are respectively received by the reception time calculation unit 70 of the first ordinary base station 12A, the second ordinary base station 12B, the third base station 12C, and the fourth ordinary base station 12D. The detected reception time, and Ts is the transmission time of the radio wave in the radio unit 22 of the mobile station 10. That is, the right side of the equation (2) indicates the radio waves between the first ordinary base station 12A, the second ordinary base station 12B, the third ordinary base station 12C, and the fourth ordinary base station 12D and the mobile station 10. Represents the square of the propagation distance of the radio wave obtained by multiplying the propagation time by the radio wave velocity c. The equation (2) is a simultaneous equation with x, y and Ts as unknowns. When Ts is eliminated from the equation (2), the following equation (3) is obtained.

The positioning unit 100 calculates the position (x, y) of the mobile station 10 by solving the equation (2) or (3). In solving the equation (2) or (3), it is not necessary to solve all the equations simultaneously, and the equations may be solved by a minimum number of equations to calculate the solution.

  FIG. 13 is a flowchart for explaining the outline of the control operation in the mobile station positioning system 8 of this embodiment. First, in step (hereinafter, “step” is omitted) SA1, an instruction for performing positioning of the mobile station 10 is issued from the server 14 to each of the base stations 12. This command includes (1) a command to transmit a transmission command to the mobile station 10 from the base station 12 to the mobile station 10 to any one of the plurality of base stations 12, and (2) to each base station 12, A command for receiving a positioning radio wave transmitted from the mobile station 10, calculating a reception time in the reception time calculation unit 70, and causing the server 14 to transmit the command. Among these, the transmission command (1) is a command for causing the mobile station 10 to transmit a radio wave for positioning. Any one of the base stations 12 is a base station 12 arbitrarily selected by the server 14, for example.

  In SA2, each base station 12 waits for an SA1 command from the server 14 to be received. When the SA1 command from the server 14 is received, the determination at this step is affirmed and the subsequent SA3 is executed. On the other hand, if the SA1 command from the server 14 is not received, the determination in this step is denied, SA1 is repeatedly executed, and a standby is performed until the SA1 command from the server 14 is received.

  SA3 is a step executed when the determination of SA2 is affirmed, and it is determined whether or not the command from the server 14 received at SA1 includes the transmission command of (1). If the command from the server 14 received in SA1 includes the transmission command (1), the determination in this step is affirmed and SA4 is executed. On the other hand, when the command from the server 14 received at SA1 does not include the transmission command of (1), SA4 is not executed, and the standby for receiving the radio wave transmitted from the mobile station 10 is performed. Is done.

  In SA4, a transmission command for causing the mobile station 10 to transmit a radio wave for positioning is transmitted from the base station 12 that has received the command (1) to the mobile station 10 by radio. Thereafter, as with the base station that has not received the command (1), standby is performed to receive the radio wave transmitted from the mobile station 10.

  In SA5, the mobile station 10 waits whether an instruction (SA4) for transmitting a radio wave for positioning is received. When the mobile station 10 receives a command for transmitting a radio wave for positioning, the determination in this step is affirmed and the subsequent SA6 is executed. On the other hand, if a command for transmitting a radio wave for positioning is not received, the determination in this step is denied, SA5 is repeatedly executed, and a command for transmitting a radio wave for positioning is received. Wait until

  In SA6 corresponding to the code generation unit 28, the modulation unit 34, and the like of the mobile station 10, a radio wave for positioning is transmitted from the mobile station 10 to each base station 12.

  In SA7 corresponding to the received signal processing unit 68 of each base station 12, it is determined whether or not a positioning radio wave transmitted from the mobile station 10 has been received. When a radio wave transmitted from the mobile station 10 is received, this determination is affirmed and SA10 is executed. On the other hand, when the radio wave transmitted from the mobile station 10 is not received, the determination in this step is denied and SA8 is executed.

  In SA8, which is executed when the determination in SA7 is denied, it is determined whether or not an elapsed time after issuing a radio wave transmission command to the mobile station 10 in SA4 exceeds a preset timeout time. . If the elapsed time exceeds the timeout time, the determination in this step is affirmed and SA9 is executed. If the elapsed time does not exceed the timeout time, the determination in this step is denied, and the process returns to SA7 to continue receiving radio waves from the mobile station 10.

  In SA9 executed when the determination of SA8 is affirmed, it is assumed that an error has occurred for the base station 12 for which the determination of SA8 has been affirmed because radio waves from the mobile station 10 could not be received. Is done. Specifically, processing such as sending a message indicating that reception has failed to the server 14 is performed.

  SA10 corresponding to the received signal processing unit 68 of the base station 12 is executed when the determination of SA7 is affirmed. In SA10, the received wave received at the base station 12 is demodulated into an in-phase component signal wave and a quadrature component signal wave by quadrature demodulation, and a matched filter is applied to each of the in-phase component signal wave and the quadrature component signal wave. The first correlation value and the second correlation value, which are correlation values with the replica code, are calculated. Then, a difference between the first correlation value and the second correlation value is calculated.

  SA11 corresponding to the reception time calculation unit 70 of the base station 12 is executed when the determination of SA7 is affirmed. In SA11, the time at which the sign of the difference between the first correlation value and the second correlation value calculated in SA10 is switched (zero cross) is detected, and that time is set as the reception time of the radio wave from the mobile station 10.

  In SA12 corresponding to the communication interface 76 of the base station 12, information on the reception time calculated in SA11 is transmitted from the base station 12 to the server 14.

  In SA13, it is determined whether or not information about the reception time of radio waves from the mobile station 10 in each base station 12 has been transmitted from a predetermined number of base stations 12 and received by the server 14. Is done. This predetermined number is a number necessary for calculating the position of the mobile station 10 in SA16. For example, when the movement of the mobile station 10 is in a three-dimensional space, the predetermined number is four. If the information about the height of the mobile station 10 can be obtained by a height detection means (not shown) or the like even in a three-dimensional space. When information about reception intensity is received from the predetermined number or more of base stations 12, the determination in this step is affirmed and SA16 is executed. On the other hand, when the information about the reception time is not received from the predetermined number or more of base stations 12, the determination in this step is denied and the subsequent SA14 is executed.

  In SA14, it is determined whether or not the elapsed time since the command in SA1 has exceeded a preset timeout time. If the elapsed time exceeds the timeout time, the determination in this step is affirmed and SA15 is executed. If the elapsed time does not exceed the timeout time, the determination at this step is denied, SA13 is repeatedly executed, and information about the reception time from the base station 12 is received.

  In SA15 executed when the determination of SA14 is affirmed, the reception intensity of radio waves from the mobile station 10 may be received from the number of base stations 12 necessary to calculate the position of the mobile station 10. If not, error handling is performed. Specifically, for example, information indicating that the calculation of the position of the mobile station 10 has failed is output instead of the output of the position of the mobile station 10 calculated by SA16 described later.

  In SA16 corresponding to the positioning unit 100 of the server 14, based on the information about the reception time of the radio wave from the mobile station 10 in each base station 12 received in SA13, the information about the position of each base station 12, etc. The position of the mobile station 10 is calculated by solving the equation (2) or (3).

  According to the above-described embodiment, in the mobile station 10, the first code generated by the PN code generation unit 30 of the code generation unit 28 and the delay circuit 32 delays the second code by a predetermined time ΔT from the first code. A sign is generated. Further, the modulation unit 34 modulates the first carrier wave generated by the carrier wave generation unit 36 with the first code, generates the second code with the carrier wave generation unit 36, and generates the predetermined phase ( The signal is delayed by π / 2) but modulated, and the modulated signal is synthesized by the synthesizer 44, and the output from the modulator 34 is transmitted wirelessly by the transmission amplifier 24. On the other hand, in the base station 12, the radio wave transmitted from the mobile station 10 is received by the receiving amplifier 66, and the first reference carrier generated by the reference carrier generation unit 80 by the demodulation unit 78 and the first reference by the phase shift unit 84. The received wave is demodulated based on each second reference carrier delayed by the predetermined phase from the carrier. Further, the correlation calculation unit 88 calculates a first correlation value between the first reception signal demodulated by the demodulation unit 78 based on the first reference carrier wave and the first code generated by the PN code generation unit 90, and demodulates the first correlation value. The second correlation value between the second received signal and the second code demodulated by the unit 78 based on the second reference carrier is calculated, and the differential amplifier 96 calculates the difference between the first correlation value and the second correlation value. Calculated. Furthermore, the reception time at the base station 12 of the radio wave transmitted from the mobile station 10 is calculated based on the difference between the first correlation value and the second correlation value calculated by the differential amplifier 96 by the reception time detection unit 70, Since the positioning unit 100 of the server 14 calculates the position of the mobile station 10 based on the position of each base station 12 and the reception time detected by the reception time detection unit 70, the mobile station positioning system 8 Even when it is difficult to accurately detect the reception time of the radio wave based on the peak of the correlation value due to the dullness of the peak of the reception, it is possible to accurately detect the reception time and the detected reception The position of the mobile station 10 can be calculated based on the time. Further, the differential amplifier 96 calculates the difference between the first correlation value and the second correlation value, and the reception time calculation unit 70 calculates the reception time based on the operation thereof, and therefore exists between the signal line and the ground. Even when common mode noise, which is noise from a noise source, is generated, the influence of the common mode noise can be removed.

  In addition, according to the above-described embodiment, the code generation unit 28 includes the delay time setting unit 52 that selectively sets the predetermined time ΔT from a plurality of preset values, so that the mobile station positioning system 8 targets. The predetermined time ΔT can be changed according to the position calculation accuracy. At this time, since the modulation frequency in the modulation unit 34 is not changed even if the predetermined time ΔT is changed, the mobile station 10 does not increase the signal processing speed, thereby increasing the power consumption. The calculation accuracy of the position of the positioning system 8 can be improved.

  Further, according to the above-described embodiment, the code generator 28 delays the second code by an integer m times the value obtained by dividing the chip period T of the second code by an arbitrary natural number n as the predetermined time ΔT. Therefore, it is possible to set a plurality of appropriate predetermined times ΔT according to the calculation accuracy of the position targeted by the mobile station positioning system 8.

  Further, according to the above-described embodiment, the reception time detection unit 70 is transmitted from the mobile station 10 when the difference between the first correlation value and the second correlation value calculated by the differential amplifier 96 becomes zero. Since it is calculated as the reception time of the radio wave at the base station 12, the value of the difference between the first correlation value and the second correlation value changes abruptly around zero, so the waveform of the first correlation value or the second correlation value is Even when it is dull and the peak time cannot be detected accurately, the reception time can be detected accurately from the time when the difference between the first correlation value and the second correlation value becomes zero.

  Subsequently, another embodiment of the present invention will be described. In the following description, portions common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  When the mobile station 10 and the base station 12 are used indoors, there is a so-called multipath problem in which the radio wave transmitted from the mobile station 10 is reflected on a wall surface or the like to be reflected and received by the base station 12. Can occur. FIG. 14 is a diagram illustrating the output of the correlation value calculation unit in the receiver when this multipath occurs. The radio wave including the PN code transmitted from the transmitter is directly transmitted from the transmitter to the receiver, and the reflected wave is reflected from the transmitter to other objects and reaches the receiver. When reaching, the correlation value calculation unit of the receiver calculates a correlation value for each of the PN code included in the direct wave and the PN code included in the reflected wave. In FIG. 14A, the solid line is the correlation value for the direct wave, and the broken line is the correlation value for the reflected wave. Note that ΔTd is the arrival time difference between the direct wave and the reflected wave. Actually, since the correlation value calculated by the correlation value calculation unit of the receiver is the sum of these values, it is as shown in FIG.

  FIG. 15 is a functional block diagram for explaining a main part of functions of the reception signal processing unit 68 of the base station 12 in the present embodiment, and corresponds to FIG. 6 of the above-described embodiment. Compared to the function of the received signal processing unit 68 of the first embodiment shown in FIG. 6, the received signal processing unit 68 shown in FIG. 15 has the first correlation value and the second output that are the outputs of the differential amplifier 96. The difference is that it further includes a differentiator 98 for calculating a differential value of a difference from the correlation value.

  The differentiator 98 calculates a differential value of the difference between the first correlation value and the second correlation value, for example, by calculating a change amount per minute time interval defined in advance. The differentiator 98 corresponds to the differential value calculation unit.

  FIG. 16 is a diagram illustrating the outputs of the first correlation value calculation unit 92, the second correlation value calculation unit 94, the operational amplifier 96, and the differentiator 98 under the influence of multipath. In FIG. 16, each of the outputs of the first correlation value calculation unit 92, the second correlation value calculation unit 94, and the differential amplifier 96 has a waveform represented by a bold line. In addition, among the waveforms described together with the outputs of the first correlation value calculation unit 92, the second correlation value calculation unit 94, and the differential amplifier 96, the thin solid line directly reaches the base station 12 from each mobile station 10 directly. A component due to the influence of the wave, and a broken line represent a component due to the influence of the reflected wave that arrives at the base station 12 from each mobile station 10 after being reflected by another object. Further, the waveforms representing the outputs of the differential amplifier 96 and the differentiator 98 indicate a state where the waveforms are dull due to the influence of multipath or the like. The waveform representing the output of the differentiator 98 shows a state in which the arrival time can be detected with high accuracy even from the differential amplifier output waveform having a dull waveform.

  The outputs of the first correlation value calculation unit 92 and the second correlation value calculation unit 94 receive both the direct wave and the reflected wave that arrives with a delay of ΔTd from the direct wave, as described above with reference to FIG. As a result, the output is represented by the thick line in FIG. As a result, the output of the differential amplifier 96 is also different from the case where there is no multipath effect as indicated by a thin solid line, for example. Particularly, the time tz when the output of the differential amplifier 96 is zero-crossed when there is no multipath effect represented by a thin solid line, and the time when the output of the differential amplifier 96 is zero-crossed when there is a multipath effect represented by a thick line. It is different from tz ′. That is, when there is a multipath effect, an error occurs when the time when the output of the differential amplifier 96 crosses zero is defined as the reception time.

  On the other hand, paying attention to the output of the differentiator 98, a change caused by a predetermined time ΔT, which is a delay time of the second code generated by the code generator 28 of the mobile station 10 with respect to the first code, appears in a pulse shape.

  In the present embodiment, the reception time calculation unit 70 of the base station 12 calculates the differential value of the difference between the first correlation value and the second correlation value, which is the output of the reception signal processing unit 68, that is, the output of the differentiator 98. Based on the time change, the reception time of the radio wave from the mobile station 10 is calculated. Specifically, the reception time calculation unit 70 calculates the reception time as follows. FIG. 17 is a diagram showing the change over time of the differential value of the difference between the first correlation value and the second correlation value, which is the output of the differentiator 98. When the output of the differentiator 98 exceeds the threshold value DTH, the reception time calculation unit 70 stores the time Ta, and further detects the peak of the output of the differentiator 98. This is to prevent the mixed noise from being erroneously detected as the reception time, and the value of the threshold value Dth is such that the noise can be prevented from being erroneously detected as the reception time. It is determined in advance in consideration of the size and the size of the peak of the waveform generated according to the actual reception time.

  The reception time calculation unit 70 stores the time Tp at which the peak of the output of the differentiator 98 is detected. Further, the time Tb when the output of the differentiator 98 falls below the threshold value Dth is detected and stored. Then, the time during which the output of the differentiator 98 has exceeded the threshold value Dth is calculated as Tb−Ta based on the stored times Ta and Tb. It is determined whether or not the time Tb-Ta during which the output of the differentiator 98 calculated above exceeds the threshold value Dth exceeds a predetermined threshold value Tth. The time Tp at which the peak of the output of the device 98 is detected is set as the reception time of radio waves from the mobile station 10. On the other hand, when the time Tb-Ta when the output of the differentiator 98 exceeds the threshold value Dth does not exceed the predetermined threshold value Tth, the peak at the time Tp is generated due to the influence of noise or the like. The search for the peak is continued even though it is not the reception time of the radio wave from the mobile station 10. Here, the threshold value Tth is, for example, a second code in the delay circuit 32 of the mobile station 10 so that the peak of the output of the differentiator 98 corresponding to the zero cross of the direct wave can be detected while the peak due to the influence of noise can be excluded. Is set to ΔT / 2, which is a half of a predetermined time ΔT for delaying from the first code.

  FIG. 18 is a flowchart for explaining the outline of the control operation of the reception time calculation unit 70 of the base station 12 in this embodiment. Also in this embodiment, the control operation of the mobile station positioning system 8 is performed as shown in the flowchart of FIG. 13, for example, as in the above-described embodiment, but the flowchart of FIG. 18 is executed instead of step SA11 in FIG. The

  First, in SB1 corresponding to the differentiator 98 of the mobile station 12, the output of the operational amplifier 96 calculated in SA10, that is, the differential value of the difference between the first correlation value and the second correlation value is calculated. If the differentiator is configured by hardware such as a differentiating circuit, this step can be omitted.

  In subsequent SB2, the differential value calculated in SB1 is subjected to A / D conversion. At this time, the sampling rate of the A / D conversion is sufficiently faster than ΔT, for example, more than three times the predetermined time ΔT that is the delay time in the delay circuit 32 of the mobile station 10, that is, the predetermined time ΔT is accurately detected. Sampling speed as high as possible.

  In SB3, data relating to the differential value subjected to A / D conversion in SB2 is stored in a storage device such as a memory (not shown). In SB4, smoothing processing is performed by a smoothing filter in order to remove noise included in the data.

  In SB5, a variable (counter) i indicating the number of times of repeated execution, a variable Dmax indicating the value of the differential value, and a flag P indicating that a peak is being detected are initialized to zero.

  In SB6, 1 is added to the value of the variable i representing the number of repeated executions, and the value Di of the differential value at the time Ti is obtained.

  In SB7, it is determined whether or not the differential value Di exceeds a predetermined threshold value Dth. If the value Di of the differential value exceeds a predetermined threshold value Dth, the determination in this step is affirmed and SB8 is executed in order to detect the peak of the differential value. On the other hand, when the value Di of the differential value falls below a predetermined threshold value Dth, the determination at this step is denied and SB14 and subsequent steps are executed.

  In SB8, it is determined whether the value of the flag P indicating that the peak is being detected is 1. If the value of the flag P is 0, the determination in this step is denied, and it is determined that the peak has not been detected so far, and SB11 is executed after SB9 and SB10 are executed. On the other hand, when the value of the flag P is 1, the determination of this step is affirmed, and SB11 is executed without executing SB9 and SB10, assuming that the peak is already being detected.

  In SB9, the time Ti when the determination in SB7 is affirmed is stored as a time Ta representing the start time of the peak detection period. In SB10, the value of flag P indicating that a peak is being detected is set to 1, and peak detection is started.

  In SB11, it is determined whether or not the differential value Di detected in SB6 is larger than the maximum differential value Dmax in the peak detection period. If the value Di of the differential value is larger than the maximum value Dmax, the determination in this step is affirmed and SB12 is executed. On the other hand, if the value Di of the differential value is smaller than the maximum value Dmax or both are equal, the determination in this step is denied, and SB13 is executed without executing SB12.

  In SB12, the value Di of the differential value is stored as the value of the maximum value Dmax. The time Ti is stored as a variable Tp representing the peak detection time. That is, the time Ti which is the execution time of SB6 is set as a new peak detection time.

  In SB13, it is determined whether or not the value of the variable i representing the number of repeated executions is iend representing the maximum number of repeated executions. When the value of the variable i reaches the maximum value iend, the determination at this step is affirmed, and this flowchart ends. On the other hand, when the value of the variable i has not reached the maximum value iend, SB6 and subsequent steps in this flowchart are repeatedly executed. Here, the maximum value iend is a variable indicating that a peak has been detected for a differential value corresponding to the entire received wave by repetition. Specifically, the code generation unit 28 of the mobile station 10 generates the maximum value iend. This is a value determined by the code length of the PN code, the sampling time of A / D conversion in SB2, and the like. If the determination of SB13 is affirmed and this flowchart is terminated, this corresponds to the fact that the peak of the differential value could not be detected according to this flowchart, that is, the detection of the reception time failed.

  In SB14 executed when the determination of SB7 is negative, it is determined whether the value of the flag P indicating that the peak is being detected is 1. If the value of the flag P is 0, the determination in this step is denied, and it is determined that peak detection has not started yet, and the process proceeds to SB13. On the other hand, when the value of the flag P is 1, the determination in this step is affirmed, and SB15 and subsequent steps are executed to end the peak detection.

  In SB15, the time Ti when the determination of SB7 is denied is stored as a time Tb representing the end time of the peak detection period. In SB16, it is determined whether or not the length of Tb-Ta, which is the peak detection execution time, exceeds a predetermined threshold value Tth. If the length of the peak detection execution time Tb-Ta exceeds the threshold value Tth, the determination in this step is affirmed and SB18 is executed. On the other hand, if the length of the peak detection execution time Tb-Ta is less than the threshold value Tth, or both are equal, the determination in this step is denied and SB17 is executed.

  SB17 is a step executed when the determination of SB16 is negative, that is, when the peak detected at SB15 is detected due to noise. In this step, the value of the flag P indicating whether or not the peak is being executed is changed to 0 indicating that the peak is not being detected. Further, the value of the variable Dmax representing the maximum value of the differential value in the peak detection period is initialized to 0 to prepare for peak detection again.

  SB18 is a step executed when the determination of SB16 is affirmed, that is, when the detection of the peak terminated at SB15 is caused by the delay of the first code and the second code. In this step, the value of the time Tp stored in the SB 12 is output as the time when the peak of the differential value is detected, that is, as the reception time of the radio wave from the mobile station 10.

  According to the above-described embodiment, the differentiator 98 that calculates the differential value of the difference between the first correlation value and the second correlation value calculated by the differential amplifier 96 is provided, and the reception time detection unit 70 includes the differentiator. Since the reception time at the base station 12 of the radio wave transmitted from the mobile station 10 is calculated based on the time when the differential value calculated by 98 is maximized, the influence of common mode noise, which is the effect of the above-described embodiment, is calculated. In addition to being able to be removed, even when a reflected wave due to the influence of multipath reaches the base station 12 before completion of reception of the direct wave at the base station 12, the reception time can be accurately calculated. .

  Further, according to the above-described embodiment, the code generation unit 28 generates the second code by shifting the same code as the first code by the predetermined time ΔT, so the time change of the first correlation value and the second correlation The time change of the value is the same time change with a predetermined time interval, and preferably the differential value of the difference between the first correlation value and the second correlation value calculated by the differentiator 98 is calculated. Can do.

  FIG. 19 is a functional block diagram for explaining a main part of the functions of the mobile station 10 in another embodiment of the present invention, corresponding to FIG. 2 in the above-described first embodiment. Compared with the mobile station 10 of FIG. 19 and the mobile station 10 of FIG. 2, the configuration of the code generator 128 of the mobile station 10 of FIG. 19 is different from the configuration of the code generator 28 of the mobile station 10 of FIG. ing. The code generator 128 included in the mobile station 10 of the present embodiment includes a clock 129, a delay circuit 32, a first PN code generator 130, and a second PN code generator 131.

  The clock 129 drives the first PN code generator 130 and the delay circuit 32 by outputting a clock signal having a predetermined clock speed. The first PN code generator 130 transmits a first PN code, which is a predetermined PN code, according to the clock signal output from the clock 129. This first PN code corresponds to the first code. The PN code generated by the first PN code generator 130 is input to the first modulator 38.

  The delay circuit 32 delays the input signal by a predetermined time ΔT, similarly to the delay circuit 32 of the first embodiment. In this embodiment, the clock signal input from the clock 129 is output after being delayed by a predetermined time ΔT. The predetermined time ΔT is set by the delay time setting unit 52 as in the first embodiment. The second PN code generation unit 131 transmits a second PN code, which is a predetermined PN code, in response to the clock signal delayed (shifted) by the delay circuit 32. For this reason, the generation of the code by the second PN code generator 131 is delayed by the predetermined time ΔT from the generation of the code by the first PN code generator 130. This second PN code is different from the first PN code and corresponds to the second code. The PN code generated by the second PN code generator 131 is input to the second modulator 42.

  FIG. 20 is a functional block diagram for explaining a main part of the function of the received signal processing unit 68 of the base station 12 in another embodiment of the present invention, corresponding to FIG. 6 in the first embodiment. is there. 20 is compared with the reception signal processing unit 68 in FIG. 6, the configuration of the correlation calculation unit 188 included in the reception signal processing unit 68 in FIG. 19 and the correlation included in the reception signal processing unit 68 in FIG. 6. The configuration of the calculation unit 88 is different. The correlation calculation unit 188 included in the reception signal processing unit 68 of the present embodiment includes a first PN code generation unit 190, a second PN code generation unit 191, a first correlation value calculation unit 192, and a second correlation value calculation unit 194. Is done.

  The first PN code generator 190 and the second PN code generator 191 generate the same PN code as the PN code generated by the first PN code generator 130 and the second PN code generator 131 of the mobile station 10, respectively.

  The first correlation value calculation unit 192 and the second correlation value calculation unit 194 are each configured to include a matched filter in the same manner as the first correlation value calculation unit 92 and the second correlation value calculation unit 94 in the above-described embodiment. . The first correlation value calculation unit 192 displays the correlation value between the signal wave demodulated by the first demodulation unit 82 and the PN code generated by the first PN code generation unit 190, and the second correlation value calculation unit 194 performs the second demodulation. The correlation value between the signal wave demodulated by the unit 86 and the PN code generated by the first PN code generation unit 191 is sequentially calculated. In this way, the correlation value can be calculated using the replica code of the PN code used at the time of transmission for each signal wave demodulated by the first demodulator 82 and the second demodulator 86. . An example of the operation of the mobile station positioning system 8 in the present embodiment is performed according to the flowchart shown in FIG. 13 as in the above-described embodiment.

  According to the present embodiment, the code generator 128 is a first code generated by the first PN code generator 130 and a second code generated by the second PN code generator 131 which is a code different from the first code. Since the delay circuit 32 generates a code shifted by the predetermined time ΔT, when the multipath is affected in the environment where the multipath occurs, either the first code or the second code is changed to the other. Even if it is mixed, the other correlation value is not affected by the mixing, so that it is possible to reduce the multipath effect in the difference between the first correlation value and the second correlation value calculated by the differential amplifier 96. .

  FIG. 21 is a functional block diagram for explaining a main part of the function of the reception signal processing unit 68 of the base station 12 in this embodiment, and corresponds to FIG. 20 of the above-described embodiment. Compared with the function of the reception signal processing unit 68 of the third embodiment shown in FIG. 20, the reception signal processing unit 68 shown in FIG. 21 has the first correlation value and the second correlation value output from the differential amplifier 96. The difference is that it further includes a differentiator 98 for calculating a differential value of a difference from the correlation value.

  The differentiator 98 is the same as the differentiator 98 included in the received signal processing unit 68 of the base station 12 in the second embodiment. For example, by calculating the amount of change per minute time interval defined in advance, A differential value of the difference between the first correlation value and the second correlation value is calculated. The differentiator 98 corresponds to the differential value calculation unit. An example of the operation of the mobile station positioning system 8 in the present embodiment is performed according to the flowcharts shown in FIGS. 13 and 18 as in the above-described embodiment.

  According to the above-described embodiment, the differentiator 98 that calculates the differential value of the difference between the first correlation value and the second correlation value calculated by the differential amplifier 96 is provided, and the reception time calculation unit 70 includes the differentiator. Since the reception time at the base station 12 of the radio wave transmitted from the mobile station 10 is calculated based on the time when the differential value calculated by 98 is maximized, the influence of common mode noise, which is the effect of the above-described embodiment, is calculated. In addition to being able to be removed, even when a reflected wave due to the influence of multipath reaches the base station 12 before completion of reception of the direct wave at the base station 12, the reception time can be accurately calculated. .

  In addition, according to the above-described embodiment, the code generator 128 includes the first code generated by the first PN code generator 130 and the second PN code generator 131 generated by a second PN code generator 131 that is different from the first code. Since two codes and a code shifted by a predetermined time ΔT are generated in the delay circuit 32, when affected by multipath in an environment where multipath occurs, either the first code or the second code is generated. Even if one is mixed in the other, the other correlation value is not affected by the mixing, thereby reducing the influence of multipath in the difference between the first correlation value and the second correlation value calculated by the differential amplifier 96. be able to.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, in the above-described embodiment, the code generated by the code generators 28 and 128 is a PN code, but is not limited thereto. That is, other types of spreading codes may be used as long as the autocorrelation value at the time of synchronization is high and the autocorrelation value and the cross-correlation value at the time of asynchronousness are low.

  The PN codes generated by the PN code generation unit 30, the first PN code generation unit 130, and the second PN code generation unit 131 are PN codes stored in advance, respectively. For example, the PN code generation unit 30, The first PN code generator 130 and the second PN code generator 131 may store a plurality of types of codes and generate one selected from the stored codes. In this aspect, the mobile station 10 notifies the base station 12 of the types of codes generated by the PN code generation unit 30, the first PN code generation unit 130, and the second PN code generation unit 131, and the PN code of the base station. The generation unit 90, the first PN code generation unit 190, and the second PN code generation unit 191 are configured to generate corresponding codes.

  In the mobile station 10, the demodulator 48 receives the carrier wave from the carrier wave generator 36. However, the present invention is not limited to this, and the carrier wave corresponding to the frequency of the transmission carrier wave of the base station 12 is not limited to this. Is entered.

  The differential amplifier 96 subtracts the output of the first correlation value calculator 92 from the output of the second correlation value calculator 94 as the difference between the output of the first correlation value calculator 92 and the output of the second correlation value calculator 94. However, the output of the second correlation value calculator 94 may be subtracted from the output of the first correlation value calculator 92. In this case, the output of the differential amplifier 96 is opposite to that of the above-described embodiment, but the time at which the differential amplifier 96 crosses zero is not changed.

  In the above-described embodiment, the delay time setting unit 52 sets the value of the predetermined time ΔT, which is the time for delaying the PN code in the delay circuit 32, to 1 of the chip width T of the PN code generated by the PN code generation unit 30. / N (n is a natural number) was set to be a value of an integer m times. In addition, when the magnitude of the differential output of the differential amplifier 96 in the base station 12 is appropriately detected and the magnitude of the differential output exceeds a predetermined upper limit threshold value, the delay time setting unit 52 The delay time setting unit 52 may be changed so as to increase ΔT when ΔT is decreased with respect to the delay time, and when the differential output exceeds a predetermined lower threshold. Good.

  In the above-described embodiment, the reception time of the radio wave calculated by the reception time calculation unit 70 is the time (T + ΔT / 2) at which the output of the differential amplifier 96 for the correlation value of the direct wave crosses zero. It is not limited to such a definition. For example, when the positioning unit 100 performs positioning of the mobile station 10 by solving the equation (3), it is only necessary that the reception time of the same definition is used in each base station 12. In the case where positioning of the mobile station 10 is performed by solving the above equation, the radio wave transmission time at the mobile station 10 may be defined corresponding to the definition of the reception time at the base station 12. Specifically, the transmission time of this radio wave is defined corresponding to the definition of the reception time in the reception time calculation unit 70 of the base station 12. In this embodiment, the time when the output of the differential amplifier 96 becomes zero cross in the reception time calculation unit 70, that is, the time after T + ΔT / 2 has elapsed since the start of reception of the first code is defined as the reception time. 10 is defined as the transmission time after T + ΔT / 2 has elapsed from the start of transmission of the first code. However, when the reception time calculation unit 70 defines the reception time as T has elapsed since the start of reception of the first code. May be defined as the transmission time after the elapse of T from the start of transmission of the first code in the mobile station 10.

  In the above-described embodiment, the radio wave transmitted from the mobile station 10 may include an identification code for identifying each mobile station 10. In this way, positioning can be performed for each mobile station 10 in an environment where a plurality of mobile stations 10 coexist.

  Further, the time-out reference when performing the control operation of the mobile station positioning system 8 in the above-described embodiment may be different from that described above. Specifically, in the above-described embodiment, in SA8 of the flowchart of FIG. 13, whether or not the elapsed time since the transmission command of the radio wave to the mobile station 10 in SA4 has passed a predetermined timeout time is determined. Although the timeout has been determined, the present invention is not limited to this, and it may be defined by the elapsed time from the positioning start command from the server 14 in SA1. In SA14, the timeout is determined based on whether the elapsed time from the SA1 command exceeds a preset timeout time, which is defined by the elapsed time from the reception of the first reception time from the base station 12. May be.

  In addition, the correlation value used for detecting the reception time in the above-described embodiment is not limited to the one defined by the above equation (1), and may be another definition. What is necessary is just to be able to detect the synchronization between the replica and the received signal by the peak.

  In the above-described embodiment, the PN signal is transmitted from the mobile station 10 and received by each of the plurality of base stations 12, but the present invention is not limited to this mode. That is, a positioning signal is sequentially transmitted from each of the plurality of base stations 12 to the mobile station 10, the reception time of each radio wave is detected at the mobile station 10, and the radio wave propagation time from each base station 12 to the mobile station 10 is determined. The mobile station 10 may be determined based on the calculation.

  In the above-described embodiment, the base station 12 and the server 14 are connected by the communication cable 18 to perform information communication. However, the present invention is not limited to this. For example, a wireless communication function such as a wireless LAN may be used. In that case, it is only necessary that the communication interfaces 76 and 98 have a communication function corresponding to the type of communication.

  In the above-described embodiment, the first reference carrier, that is, the reference carrier inputted from the reference carrier generator 80 to the first demodulator 82 is a radio wave having the same frequency as the first carrier. I can't. For example, the first reference carrier wave may be a radio wave having an intermediate frequency of the frequency of the first carrier wave.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

It is a figure explaining the outline | summary of the mobile station positioning system which is one Example of this invention. It is a functional block diagram explaining the principal part of the function which the mobile station which comprises the mobile station positioning system of FIG. 1 has. It is a figure explaining an example of the code generated by the code generation part of a mobile station. It is a figure explaining the specific example of a structure of the delay circuit of the mobile station of FIG. It is a functional block diagram explaining the principal part of the function which the base station which comprises the mobile station positioning system of FIG. 1 has. It is a functional block diagram explaining the principal part of the function which the received signal processing part of a base station has. It is a figure explaining an example of the composition of the matched filter which constitutes the 1st correlation value calculation part and the 2nd correlation value calculation part. It is a figure explaining an example of the input and output of the matched filter of FIG. FIG. 7 is a diagram illustrating an example of input and output of the differential amplifier in FIG. 6 and calculation of a reception signal by a reception time calculation unit. It is a figure explaining the case where noise etc. are mixed about each of a general correlation value and the output of the differential amplifier of FIG. It is a functional block diagram explaining the principal part of the function which the server which comprises the mobile station positioning system of FIG. 1 has. It is a figure explaining the principle of the positioning in the positioning part of FIG. It is a flowchart explaining an example of the control action in a mobile station positioning system. It is a figure explaining the influence which a multipath has on a correlation value. It is a functional block diagram explaining the principal part of the function which the received signal processing part of the base station in another Example of this invention has, and is a figure corresponding to FIG. It is a figure explaining an example of the input and output of a differentiator of FIG. It is a figure explaining calculation of the reception time by the reception time calculation part in another Example of this invention. It is a flowchart explaining an example of the control action for the reception time calculation in the base station of another Example of this invention, Comprising: It replaces with a part of FIG. 13, and is performed. It is a functional block diagram explaining the principal part of the function which the mobile station in another Example of this invention has, Comprising: It corresponds to FIG. FIG. 7 is a functional block diagram for explaining a main part of functions of a received signal processing unit of a base station in still another embodiment of the present invention, and corresponds to FIG. 6. It is a functional block diagram explaining the principal part of the function which the received signal processing part of the base station in another Example of this invention has, Comprising: It corresponds to FIG. 6, FIG.

Explanation of symbols

10: Mobile station (transmitter)
12: Base station (receiver)
8: Mobile station positioning system (positioning system)
28: Code generation unit 34: Modulation unit 24: Transmission amplifier (transmission unit)
36: Receive amplifier (receiver)
78: Demodulator 88: Correlation calculator 96: Differential amplifier (difference calculator)
70: Reception time calculation unit 100: Positioning unit 52: Delay time setting unit 98: Differentiator (differential value calculation unit)

Claims (9)

The receiver receives the radio wave transmitted from the transmitter, and calculates the position of one of the transmitter or the receiver based on the other position of the transmitter or the receiver and the reception time at the receiver. A positioning system,
The transmitter is
A code generator for generating a first code and a second code delayed by a predetermined time from the first code;
The first carrier wave is modulated by the first code generated by the code generation unit, and the second carrier wave delayed by a predetermined phase from the first carrier wave by the second code generated by the code generation unit. And a modulating unit that combines the modulated first carrier wave and second carrier wave,
A transmission unit for transmitting the output from the modulation unit as a radio wave;
Have
The receiver
A receiver for receiving the radio wave transmitted by the transmitter;
In order to obtain a first received signal and a second received signal corresponding to the first code and the second code, the received wave received by the receiving unit is demodulated based on a first reference carrier, and the first reference carrier A demodulator that demodulates the received wave based on a second reference carrier delayed by the predetermined phase;
A first correlation value between the first received signal demodulated by the demodulator based on the first reference carrier and the first code, and a second reception demodulated by the demodulator based on the second reference carrier A correlation calculation unit for calculating a second correlation value between the signal and the second code;
A difference calculation unit for calculating a difference between the first correlation value and the second correlation value calculated by the correlation calculation unit;
Have
A reception time detection unit that calculates a reception time at the receiver of the radio wave transmitted from the transmitter based on a difference between the first correlation value and the second correlation value calculated by the difference calculation unit;
A positioning unit that calculates one position of the transmitter or receiver based on the other position of the transmitter or receiver and the reception time detected by the reception time detection unit;
A positioning system characterized by comprising: The positioning system according to claim 1, wherein the code generation unit includes a delay time setting unit that selectively sets the predetermined time from a plurality of preset values. The code generation unit generates the second code by delaying from the first code by an integral multiple of a value obtained by dividing the chip period of the second code by an arbitrary natural number as the predetermined time. Item 3. The positioning system according to item 1 or 2. The reception time detection unit receives a time at which the radio wave transmitted from the transmitter is received at the receiver when the difference between the first correlation value and the second correlation value calculated by the difference calculation unit becomes zero. It calculates as time. The positioning system of any one of Claim 1 thru | or 3 characterized by these. A differential value calculation unit that calculates a differential value of a difference between the first correlation value and the second correlation value calculated by the difference calculation unit;
The reception time detection unit calculates a reception time at the receiver of a radio wave transmitted from the transmitter based on a time when the differential value calculated by the differential value calculation unit becomes maximum. The positioning system according to any one of claims 1 to 3. The positioning system according to any one of claims 1 to 5, wherein the code generation unit generates the second code by shifting the same code as the first code by the predetermined time. The positioning system according to any one of claims 1 to 5, wherein the code generation unit generates the second code by shifting a code different from the first code by the predetermined time. A code generator for generating a first code and a second code delayed by a predetermined time from the first code;
A second carrier wave modulated by the first code generated by the code generator and delayed by a predetermined phase from the first carrier by the second code generated by the second code generator. And a modulation unit that combines the modulated first carrier wave and second carrier wave,
A transmitter that wirelessly transmits the output of the modulator;
Have
A transmitter applicable to the positioning system according to claim 1. A receiving unit for receiving a predetermined radio wave;
A demodulator that demodulates the received wave received by the receiver based on a predetermined first reference carrier and demodulates the received wave based on a second reference carrier delayed by a predetermined phase from the first reference carrier;
A first correlation value between the first received signal and the first code demodulated by the demodulator based on the first reference carrier, and a second received signal demodulated by the demodulator based on the second reference carrier And a correlation calculation unit for calculating a second correlation value between the second code and the second code;
A difference calculation unit for calculating a difference between the first correlation value and the second correlation value calculated by the correlation calculation unit;
Have
A receiver applicable to the positioning system according to claim 1.

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