JP2010145358A - Device, system and method for wireless positioning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device, system and method for wireless positioning, which can control gain in a short time when determining two or more wireless terminals respectively existing in each different position. <P>SOLUTION: In a base station 100, a gain controller 109 establishes setting voltage for an amplifier 111 based on the association table prepared in advance depending on relapsed time. Thereby gain of the amplifier 111 can be adjusted without controlling feedback, allowing the gain to be controllable in a short time. Further, the longer elapsed time becomes, the larger gain of the amplifier 111 is set. Accordingly, the smaller electric power received by response pulse signal becomes because the target wireless terminal 200 as its source is in the distance, the larger gain by which the response pulse signal will be amplified. Consequently, response pulse signal level can properly be adjusted in a short time even if two or more target wireless terminals 200 exist. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless positioning device, a wireless positioning system, and a wireless positioning method for measuring the position of a wireless terminal using a wireless signal.

  As one of high-speed wireless transmission technologies, there is a UWB (Ultra Wide Band) communication method which is an impulse wireless method. In the UWB communication system, a pulse signal (hereinafter sometimes referred to as “UWB signal”) is used for communication between a base station (reader) and a wireless terminal. Therefore, the UWB communication method is performed in an ultra-wide band.

  A conventional wireless communication apparatus to which this UWB communication method is applied is disclosed in Patent Document 1, for example. FIG. 12 is a block diagram illustrating a configuration of a wireless communication device disclosed in Patent Document 1. FIG. 13 is a gain control flowchart in the wireless terminal apparatus shown in FIG.

  As shown in FIGS. 12 and 13, in the conventional wireless communication apparatus, the signal processing unit performs pulse signal error determination, and increases or decreases the threshold voltage input to the voltage comparator based on the determination result. That is, gain control is automatically performed by feedback control.

Conventionally, positioning of a wireless terminal (hereinafter sometimes referred to as “UWB positioning”) is performed in a communication system including a base station and a wireless terminal to which the UWB communication scheme is applied. In this UWB positioning, since a pulse signal having a very narrow pulse width is used, the receiving side of the pulse signal can separate incoming waves with high time resolution. Therefore, in UWB positioning, the position of the wireless terminal can be measured with high accuracy. In order to further improve the accuracy of UWB positioning, it is preferable to apply gain control.
JP 2007-116621 A

  However, since the UWB signal has a wide bandwidth and an extremely short pulse width as described above, gain adjustment is difficult. This is because it is difficult to generate a received signal strength (RSSI / Received Signal Strength Indicator) that is a control signal for automatic gain control (AGC) used in a normal radio.

  As described above, the automatic gain control technique disclosed in Patent Document 1 is also difficult to apply to UWB positioning. That is, in the gain control method disclosed in Patent Document 1, it is necessary to perform error determination, and furthermore, since a dedicated symbol is required for synchronization pull-in, it is difficult to control the gain in a short time. This gain control method can be applied to continuous received waves, but cannot be applied to intermittent signals. Therefore, it is not suitable for positioning processing in which signals transmitted from a plurality of wireless terminals having different positions must be processed while gain adjustment is performed in a short time.

  The present invention has been made in view of such points, and when positioning a plurality of radio terminals existing at different positions, a radio positioning apparatus, a radio positioning system, and a radio positioning method capable of controlling gain in a short time The purpose is to provide.

  A radio positioning apparatus according to the present invention is a radio positioning apparatus that measures a position of a terminal using a radio signal, a transmission unit that transmits a transmission signal for positioning, and the transmission signal is received and reflected by the terminal. A reception unit that receives the reception signal, an amplifier that amplifies the reception signal using a gain according to a set voltage, and a timing at which the transmission signal is transmitted from the transmission unit. A configuration is provided that includes a clock unit that measures an elapsed time until a signal is received by the receiving unit, and a gain control unit that sets the set voltage according to the measured elapsed time.

  The wireless positioning system of the present invention includes the wireless positioning device, and a wireless terminal having a function of receiving a transmission signal for positioning transmitted from the wireless positioning device and retransmitting the signal to the wireless positioning device. The structure to comprise is taken.

  A radio positioning method of the present invention is a radio positioning method for measuring a position of a terminal using a radio signal, a transmission step of transmitting a transmission signal for positioning, and the transmission signal is received and reflected by the terminal. A reception step for receiving a reception signal, a clock step for measuring an elapsed time from a timing at which the transmission signal is transmitted to a timing at which the reception signal is received, and the measured progress A configuration is provided that includes a setting step for setting a gain adjustment voltage according to time, and an amplification step for amplifying the reception signal using a gain according to the set gain adjustment voltage.

  According to the present invention, it is possible to provide a wireless positioning device, a wireless positioning system, and a wireless positioning method capable of controlling gain in a short time when positioning a plurality of wireless terminals existing at different positions.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and the description thereof will be omitted because it is duplicated.

(Embodiment 1)
[Outline of positioning system]
FIG. 1 is a diagram showing a positioning system 10 according to Embodiment 1 of the present invention. In FIG. 1, the positioning system includes a base station (interrogator) 100 and a radio terminal 200 whose position is measured by the base station 100. Here, in order to simplify the description, the number of radio terminals 200 included in the positioning system 10 is one, but the number is not limited to one.

  Base station 100 measures the position of radio terminal 200. An impulse ultra-wide band (UWB) radio signal is used for the measurement of this position.

  Base station 100 first transmits a UWB signal. Radio terminal 200 receives this UWB signal and transmits a response UWB signal based on the received UWB signal. For example, when the passive method is applied to the radio terminal 200, the received UWB signal is reflected as the response UWB signal by being reflected at the antenna end of the radio terminal 200. Further, when the semi-passive method is applied to radio terminal 200, the received UWB signal is amplified again in radio terminal 200 and then re-radiated, so that it is transmitted as a response UWB signal.

  Base station 100 receives the response UWB signal transmitted from radio terminal 200. Then, the base station 100 measures the arrival time and arrival direction of the received UWB signal, and determines the position of the wireless terminal 200 from the measurement result.

  Specifically, base station 100 measures the time required for a round trip, that is, measures the time from when the UWB signal is transmitted to when the response UWB signal corresponding to this UWB signal is received (that is, the arrival time). . Then, the base station 100 obtains the separation distance between the base station 100 and the wireless terminal 200 from the measured round trip time.

  Moreover, the base station 100 calculates | requires an arrival direction as follows. Base station 100 has a plurality of antennas (that is, array antennas). Then, the base station 100 obtains the arrival direction of the reception signal by applying the arrival direction estimation algorithm to the reception signal group received by the plurality of antennas. As this arrival direction estimation algorithm, a group of received signals received by a plurality of antennas is added while changing the phase of each received signal, and a peak of the added value is detected, or a correlation matrix such as MUSIC or ESPRIT is used. A high-resolution estimation method that uses an eigenvector can be used.

  As described above, the base station 100 can specify the position of the radio terminal 200 based on the separation distance and the arrival direction of the received signal.

[Base station configuration]
FIG. 2 is a block diagram showing a configuration of base station 100 according to Embodiment 1 of the present invention. In FIG. 2, a base station 100 includes a transmission control unit 101, a transmission baseband unit 102, a digital-analog conversion (DAC) unit 103, a transmission radio unit 104, a transmission antenna 105, a reception antenna 106, and a reception radio. Unit 107, time measurement unit 108, gain control unit 109, storage unit 110, amplification unit 111, analog-to-digital conversion (ADC) unit 112, and terminal position calculation unit 113.

  The transmission control unit 101 receives transmission enable as an input. When the transmission enable means that a positioning signal is transmitted, the transmission control unit 101 periodically generates a transmission timing signal and outputs the transmission timing signal to the transmission baseband unit 102 and the time measurement unit 108. Here, the transmission control unit 101 outputs a transmission timing signal at a cycle of 100 nanoseconds.

  The transmission baseband unit 102 receives the transmission timing signal output from the transmission control unit 101 as an input, and generates a transmission baseband signal according to the transmission timing signal. This transmission baseband signal is a pulse signal having a width of 1 nanosecond. That is, the transmission baseband signal repeatedly generates a pulse signal at intervals of 100 nanoseconds. Note that the baseband signal generated by the transmission baseband unit 102 is not limited to a pulse signal, and may be a sequence such as a spread code as long as it is a wideband signal.

  The digital-analog conversion (DAC) unit 103 receives the baseband signal generated by the transmission baseband unit 102, converts the digital baseband signal into an analog baseband signal, and converts the obtained analog baseband signal into a transmission radio unit To 104.

  The transmission radio unit 104 receives an analog baseband signal from the DAC 103 and performs a radio transmission process on the analog baseband signal. Specifically, the transmission radio unit 104 converts an analog baseband signal received from the DAC 103 into a radio frequency signal. Then, the transmission wireless unit 104 performs amplification processing and band limitation processing on the wireless signal, and then transmits the wireless signal via the transmission antenna 105.

  A plurality of receiving antennas 106 are provided in the base station 100, and constitute an array antenna as a whole. Accordingly, the same number of reception radio units 107, amplification units 111, and ADC units 112 as the reception antennas 106 are provided. In FIG. 2, only two receiving antennas 106 are illustrated, but the number is not limited to this, and may be two or more.

  The reception radio unit 107 performs radio reception processing on a signal received via the reception antenna 106. Specifically, the reception radio unit 107 performs frequency conversion processing from a radio frequency to a baseband after performing processing such as amplification processing and band limitation on the received signal. Thereby, a baseband signal is formed. The received signal includes an incoming wave that has been transmitted from the transmission radio unit 104 and reflected by a wall or a fixture, and an incoming wave that has been reflected by the radio terminal 200.

  When the time measurement unit 108 receives the transmission timing signal from the transmission control unit 101, the time measurement unit 108 resets the measurement time measured up to this time and starts the next clock processing. That is, the time measuring unit 108 measures the elapsed time from the transmission timing of a certain pulse signal to the next pulse transmission timing. This elapsed time is used to specify the required round-trip time required for the pulse signal to reciprocate between the base station 100 and the wireless terminal 200. That is, by specifying the elapsed time at the timing when the response pulse signal from the wireless terminal 200 corresponding to the transmission pulse signal is received, the round trip time can be specified. The time measurement unit 108 sequentially outputs elapsed time information to the gain control unit 109.

  The storage unit 110 stores a correspondence table of elapsed time and control voltage values corresponding to each elapsed time. When the control voltage value reference signal including the elapsed time is input from the gain control unit 109, the storage unit 110 outputs a control voltage value corresponding to the elapsed time included in the input control voltage value reference signal. Details of the correspondence table will be described later.

  The amplification unit 111 is a variable gain amplifier, and amplifies the baseband signal received from the reception radio unit 107 in accordance with the gain adjustment signal received from the gain control unit 109. The amplifying unit 111 may be configured to receive a voltage value (analog signal) that is a gain adjustment signal and change the gain according to the voltage value. Alternatively, a configuration may be adopted in which a digital control signal that is a gain adjustment signal is received and the gain is changed in accordance with the digital control signal.

  The gain control unit 109 controls the gain of the amplification unit 111 based on the elapsed time information received from the time measurement unit 108.

  Specifically, the gain control unit 109 forms a control voltage value reference signal including elapsed time information received from the time measurement unit 108, and outputs the formed control voltage value reference signal to the storage unit 110. A control voltage value corresponding to the time is received from the storage unit 110. Then, the gain control unit 109 outputs a gain adjustment signal corresponding to the control voltage value received from the storage unit 110 to the amplification unit 111. The gain control unit 109 forms a gain adjustment signal in a signal format depending on whether the amplification unit 111 has a configuration in which gain adjustment is performed with an analog signal or a configuration in which gain adjustment is performed with a digital signal. That is, as described above, when the amplification unit 111 has a configuration in which gain adjustment is performed with an analog signal, the gain control unit 109 converts the control voltage value received from the storage unit 110 into an analog signal, and is obtained. An analog signal is output to the amplification unit 111 as a gain adjustment signal.

  The ADC unit 112 receives the baseband signal amplified in the amplification unit 111, converts the baseband signal that is an analog signal into a digital signal, and outputs the digitalized baseband signal to the terminal position calculation unit 113 .

  The terminal position calculation unit 113 calculates the position of the wireless terminal 200 based on the digital baseband signal received from the ADC unit 112. Here, the position of the radio terminal 200 is specified by the distance between the base station 100 and the radio terminal 200 and the direction in which the radio terminal 200 is located with reference to the base station 100.

  Specifically, the terminal position calculation unit 113 receives elapsed time information from the time measurement unit 108 and receives a digital baseband signal from the ADC unit 112. The terminal position calculation unit 113 detects a peak corresponding to the received pulse signal that appears in the baseband signal, and specifies an elapsed time at the time of peak detection. The specified elapsed time corresponds to the round trip time. Then, the terminal position calculation unit 113 calculates the separation distance between the base station 100 and the wireless terminal 200 based on the round trip time.

  Further, the terminal position calculation unit 113 uses the phase difference when the response pulse signals transmitted from the wireless terminal 200 are received by the plurality of receiving antennas 106 to determine whether the wireless terminal 200 with reference to the base station 100 is used. Specify the direction in which it is located. As described above, the algorithm used for specifying the direction uses a method of combining signals received by the array antenna and detecting a peak related to the signal level of the combined signal, or an eigenvector of a correlation matrix such as MUSIC or ESPRIT. The high-resolution estimation method calculated by

  The positioning result of the wireless terminal 200 obtained in this way is output to the subsequent stage.

  In the above description, a pulse signal having a pulse width of 1 nanosecond is generated in the baseband. However, the present invention is not limited to this, and the pulse signal may be formed at a radio frequency. For example, an amplification circuit provided in the transmission radio unit 104 oscillates at the edge of the baseband signal, so that a pulse signal having a width of 1 nanosecond can be generated. The baseband signal input to the transmission radio unit 104 is not a pulse signal having a width of 1 nanosecond but a pulse signal having a width of about 50 nanoseconds. Therefore, the pulse signal generated by the transmission baseband unit 102 is not a pulse signal having a width of 1 nanosecond but a pulse signal having a width of 50 nanoseconds.

  Further, the pulse signal transmitted from the base station 100 may be an OOK-modulated pulse signal. At this time, the response pulse signal is also an OOK-modulated pulse signal. In this case, a diode may be provided in the reception radio unit 107, and the tangential detection processing using this diode may be performed.

  In the above description, the storage unit 110 is described as being independent of the gain control unit 109, but the storage unit 110 may be included in the gain control unit 109.

[Operation of positioning system]
The operation of the positioning system 10 having the above configuration will be described.

(Transmission of pulse signal by base station 100)
FIG. 3 is a diagram illustrating a pulse signal transmitted from the base station 100 and a response pulse signal (a received signal of the base station 100) corresponding to the pulse signal. In FIG. 3, the vertical axis represents signal power, and the horizontal axis represents time.

  As shown in the upper part of FIG. 3, the base station 100 repeatedly transmits a pulse signal at intervals of 100 nanoseconds. Each pulse signal has a pulse width of 1 nanosecond.

  The transmission period of the pulse signal is not limited to 100 nanoseconds, but is determined by the size of the distance measurement range. For example, the distance that radio waves travel in 100 nanoseconds is about 30 meters. Therefore, when pulses are transmitted at intervals of 100 nanometers, the separation distance can be measured from the base station 100 to a range of about 15 meters, considering that the distance is measured based on the round trip time. Therefore, when the distance measurement range is set to 15 meters, the base station 100 repeatedly transmits a pulse signal at intervals of 100 nanoseconds as shown in the upper part of FIG. The pulse signal is repeatedly transmitted in order to improve the accuracy of the positioning process.

(Reception of response pulse signal by base station 100)
The pulse signal transmitted from the base station 100 is received by the radio terminal 200. The wireless terminal 200 transmits a response pulse signal corresponding to the received pulse signal.

  The lower part of FIG. 3 shows the reception status of response pulse signals in the base station 100. In FIG. 3, it is assumed that there are only three wireless terminals 200 within the distance measurement range. Therefore, there are three response pulse signals (arrival waves 1, 2, 3 in FIG. 3) for one pulse signal transmitted from the base station 100.

  Here, as shown in the lower part of FIG. 3, the received power decreases in the order of the incoming waves 1, 2, and 3. Consider the difference in the received power of the response pulse signal.

  FIG. 4 is a diagram for explaining power attenuation of a propagation signal in a propagation path between the base station 100 and the radio terminal 200.

When the base station 100 and the radio terminal 200 exist in free space, attenuation in the propagation path is defined by the following equation (1).

  In Equation (1), λ represents the wavelength of the center frequency of the transmission signal, d represents the separation distance between the base station 100 and the radio terminal 200, Gt represents the gain of the transmission antenna, and Gr represents the gain of the reception antenna. It is.

  For example, under the precondition that the center frequency of the pulse signal transmitted from the base station 100 is 8 GHz, the separation distance is 3 meters, the gain of the transmission antenna 105 is 0 dBi, and the gain of the reception antenna included in the radio terminal 200 is −3 dBi The amount L by which the transmission pulse signal attenuates before being transmitted from the base station 100 and received by the wireless terminal 200 can be obtained as 63 dB by using the equation (1).

Therefore, the power P _tag of the signal received by the wireless terminal 200 is expressed by the following equation (2).
P _tag = P _tr -L (2)

In equation (2), P _tr is the transmission power of the pulse signal transmitted from the base station 100. If P _tr = 3 dBm under the above preconditions, the received power at the radio terminal 200 is determined to be −60 dBm.

Then, as described above, the radio terminal 200 amplifies the received signal and retransmits it to the base station 100. The retransmitted pulse signal undergoes attenuation calculated from Equation (1) and reaches the base station 100. Therefore, the power of the signal received by the base station 100 can be obtained from the following equation (3).
P _reader = P _tag + Amp _tag -L (3)

In Expression (3), Amp _tag is the gain of the amplifier included in the wireless terminal 200.

For example, assuming that the amplifier included in the wireless terminal 200 is 20 dB, the power P _reader of the signal received by the base station 100 is calculated as −103 dBm from the equation (3).

As described above, since attenuation L in the propagation path is a function of distance d, P _reader is also a function of distance d. This will be described more specifically below.

  FIG. 5 is a diagram illustrating an example of a situation of the positioning system 10. In FIG. 5, the positioning system 10 includes a base station 100 and three wireless terminals 200-1, 2, 3.

  Wireless terminal 200-1 is arranged at a position 2 meters away from base station 100. The radio terminal 200-2 is arranged at a position 4 meters away from the base station 100. The radio terminal 200-3 is arranged at a position 7 meters away from the base station 100.

  The transmission power of the signal transmitted from the base station 100 is 3 dBm. The antenna gain of the base station 100 is 0 dBi. Further, the gains of the antennas used by each of the radio terminals 200-1, 2, 3 for transmission / reception are all -3 dBi. The gain of each of the amplifiers included in each of the radio terminals 200-1, 2, and 3 that amplifies the pulse signal before retransmitting is 20 dB. Moreover, the center frequency of the pulse signal transmitted / received between the base station 100 and the radio terminals 200-1, 2, 3 is 8 GHz.

Under the above conditions, the reception power of the response pulse signal transmitted from the radio terminal 200-1 in the base station 100 can be calculated as −96 dBm according to the equation (3). In addition, the reception power of the response pulse signal transmitted from the radio terminal 200-2 in the base station 100 can be calculated as −108 dB by Expression (3). In addition, the reception power of the response pulse signal transmitted from the radio terminal 200-3 in the base station 100 can be calculated as −117 dB by Expression (3). Thus, P _reader can be calculated from the distance d.

Here, the propagation distance of the pulse signal is proportional to the elapsed time. Therefore, for the radio terminal 200 located at a distance d _tag meters away from the base station 100, the base station 100 transmits a pulse signal and reflects in the time until the response pulse signal corresponding to the pulse signal is received, and is reflected again. The time T _tag (that is, the above-described round trip time) until reception by the base station 100 is expressed by the following equation (4).
T _tag = (2 × d _tag ) / c (4)
In Expression (4), c represents the light propagation speed.

Based on this formula (4), when the round trip time T _tag is obtained for the wireless terminals 200-1, 2, 3, they are 13 nanoseconds, 26 nanoseconds, and 46 nanoseconds, respectively.

Therefore, by converting Equation (4) into an equation attached to d _tag and substituting it into Equation (3), the equation for obtaining the power of the signal received by the base station 100 can also be expressed by the elapsed time. it can.

  FIG. 6 is a diagram showing the reception power of the reception pulse signal in the base station 100 with respect to the round trip time in one example of the situation of the positioning system 10 shown in FIG. In FIG. 6, the horizontal axis is the round trip time, and the vertical axis is the received power of the received pulse signal. As can be seen from FIG. 6, the received power of the received pulse signal can be calculated according to the round trip time. Also, the received power of the received pulse signal decreases as the required round-trip time increases.

(Gain adjustment in base station 100)
As described above, the reception power of the reception pulse signal decreases as the required round-trip time increases. That is, the received power of the received pulse signal decreases as the elapsed time measured by the time measuring unit 108 increases.

  Accordingly, in base station 100, gain control section 109 adjusts the gain of amplification section 111 so that all signal levels are the same as a result of amplification of each received pulse signal by amplification section 111.

  As described above, the received power of the received pulse signal decreases as the elapsed time measured by the time measuring unit 108 increases, so the gain control unit 109 increases the gain of the amplifying unit 111 as the elapsed time increases. Enlarge.

  FIG. 7 is a diagram showing a gain (amplification factor) set in the amplification unit 111 in order to adjust the output level of the amplification unit 111 to −20 dB when the response pulse signal is received with the reception power shown in FIG. 6. is there. In FIG. 7, the horizontal axis represents elapsed time, and the vertical axis represents the amplification factor of the amplification unit 111. Thus, when the adjustment target of the output power of the amplification unit 111 is determined, the amplification factor set in the amplification unit 111 can be obtained for each elapsed time.

  FIG. 8 is a diagram illustrating a transmission pulse signal transmitted from the base station 100, a response pulse signal received by the base station 100, and a gain change in the amplification unit 111 of the base station 100.

  Also in the lower part of FIG. 8, the gain of the amplifying unit 111 increases monotonically as the elapsed time increases. However, unlike FIG. 7, in the lower part of FIG. 8, the gain of the amplifying unit 111 is expressed by a linear function of elapsed time.

  Further, the gain of the amplifying unit 111 becomes a predetermined value at each transmission timing of the pulse signal.

  That is, the gain of the amplifying unit 111 becomes a predetermined value at a certain pulse signal transmission timing, increases as the elapsed time increases, and returns to the default value at the next pulse signal transmission timing. Such gain adjustment processing is repeated as a repetition unit as the pulse signal is repeatedly transmitted.

  As described above, the correspondence between the elapsed time as shown in FIG. 7 or FIG. 8 and the gain set in the amplification unit 111 is stored in the storage unit 110 as a table. Thereby, the gain control unit 109 can appropriately control the output level of the amplification unit 111 according to the elapsed time.

  The elapsed time in the above description includes circuit delays in the digital and analog circuits constituting the base station 100 and the wireless terminal 200. Therefore, the accuracy of gain adjustment and UWB positioning can be improved by estimating the delay time generated in the digital and analog circuits in advance and treating the measured elapsed time minus the delay time as the elapsed time. it can.

(Positioning process in base station 100)
In base station 100, terminal position calculation section 113 calculates the position of radio terminal 200 based on the reception timing of the received pulse signal. As described above, since the level of the received pulse signal is adjusted, the terminal position calculation unit 113 can detect the received pulse signal with high accuracy, and as a result, the accuracy of the positioning process is improved.

  As described above, according to the present embodiment, in base station 100, gain control section 109 sets a set voltage for amplifying section 111 according to the elapsed time based on a correspondence table prepared in advance.

  Thereby, the gain of the amplifying unit 111 can be adjusted without performing feedback control, so that the gain can be controlled in a short time.

  Further, the gain of the amplifying unit 111 is set to increase as the elapsed time increases.

  As a result, the positioning target radio terminal 200 is farther away, and the response pulse signal can be amplified with a larger gain as the reception power of the response pulse signal is smaller. Therefore, even when there are a plurality of positioning target radio terminals 200, the level of the response pulse signal can be adjusted appropriately and in a short time. Since the terminal position can be calculated based on the received pulse signal whose level has been adjusted, the positioning accuracy can be improved.

(Embodiment 2)
[Base station configuration]
FIG. 9 is a block diagram showing a configuration of base station 300 according to Embodiment 2 of the present invention. In FIG. 9, the base station 300 includes a feature extraction unit 301, an incoming wave detection unit 302, and a gain control unit 303.

  The feature extraction unit 301 extracts a feature related to a communication environment in which the base station 300 performs positioning of the radio terminal 200 (that is, a fixed element in the communication environment) by extracting the feature of the received signal. Specifically, the feature extraction unit 301 receives a reception signal received via the reception radio unit 107, the amplification unit 111, and the ADC unit 112 from a cycle (for example, 100 nanoseconds) of transmitting a pulse signal of the base station 300. Are sampled with a sufficiently short sampling period (for example, 1 nanosecond period equal to the pulse width of the transmission pulse signal). Then, the feature extraction unit 301 adds the sample signals separated by the period for transmitting the pulse signal of the base station 300, and averages the number of samples obtained by adding the added values. This addition and averaging process is performed for each sample signal. Thus, an average power value corresponding to each sampling timing (that is, each elapsed time) is obtained in a unit period when the base station 300 repeatedly transmits a pulse signal. A graph in which the power average value is plotted with respect to the sampling timing in this unit period may be referred to as an “elapsed time profile” below.

  The incoming wave detection unit 302 detects an incoming wave (hereinafter sometimes referred to as “fixed incoming wave”) caused by the fixed element based on the elapsed time profile. The incoming wave detection unit 302 detects a fixed incoming wave by specifying a peak appearing in the elapsed time profile. The incoming wave detection unit 302 identifies only peaks having an average power value exceeding a predetermined threshold as peaks corresponding to fixed incoming waves. The incoming wave detection unit 302 outputs the sample timing (that is, the elapsed time) at which the peak corresponding to the fixed incoming wave is detected to the gain control unit 303. Hereinafter, the sample timing at which the peak corresponding to the fixed arrival wave is detected may be referred to as “characteristic timing”.

  The gain control unit 303 controls the gain of the amplification unit 111 based on the elapsed time information received from the time measurement unit 108, similarly to the gain control unit 109 of the first embodiment. However, the gain control unit 303 makes the gain of the amplification unit 111 smaller than the gains at other elapsed times regardless of the control voltage value in the table stored in the storage unit 110 during the elapsed time corresponding to the feature timing. Set. For example, the gain control unit 303 sets the gain of the amplification unit 111 to the minimum value during the elapsed time corresponding to the feature timing.

[Operation of positioning system]
An operation of the positioning system including the base station 300 having the above configuration will be described.

  FIG. 10 is a diagram showing a positioning system 20 according to Embodiment 2 of the present invention. In FIG. 10, the positioning system 20 includes a base station 300 and a radio terminal 200. The positioning system 20 is used in an environment surrounded by walls corresponding to the fixed elements.

  First, in the positioning system 20, a feature timing specifying process is performed prior to the positioning operation.

  That is, base station 300 periodically and repeatedly transmits a pulse signal as in the positioning operation. Here, a pulse signal is transmitted at a period of 100 nanoseconds.

  Radio terminal 200 that has received the pulse signal transmitted in this way transmits a response pulse signal corresponding to the received pulse signal, as described in the first embodiment.

  Base station 300 receives the response pulse signal. Here, the received signal of the base station 300 includes a signal reflected by a fixed element such as the wall in addition to the response pulse signal.

  The feature extraction unit 301 of the base station 300 performs fixed element extraction processing in the communication environment. The feature extraction unit 301 samples the received signal at the sampling period, adds the sample signals separated by the same period as the transmission period of the pulse signal, divides the obtained addition value by the added number of samples, and averages it . FIG. 11 shows an elapsed time profile in which the average power value obtained by this addition and averaging process is plotted with respect to the sampling timing.

  Here, since radio terminal 200 is normally moving, the average value for the sample signal corresponding to the response pulse signal becomes small. On the other hand, since the fixed element in the communication environment does not move, the average value for the sample signal corresponding to the pulse signal reflected there is relatively large.

  From this, the peak corresponding to the pulse signal reflected by the fixed element in the communication environment is emphasized in the elapsed time profile obtained by the addition and averaging processing of the sample signals in the feature extraction unit 301. The characteristic about is reflected. In FIG. 11, two peaks (P1 and P2 in FIG. 11) appear and correspond to pulse signals reflected by the walls through the path 401 and the path 402 in FIG. 11, respectively.

  The incoming wave detection unit 302 detects a fixed incoming wave by applying a predetermined threshold to the elapsed time profile. Regarding the elapsed time profile of FIG. 11, two fixed incoming waves corresponding to the peaks P1 and P2 are detected. Then, the sample timing corresponding to the detected fixed arrival wave is passed to the gain control unit 303 as the feature timing. The above is the process for specifying the feature timing.

  After the feature timing specifying process, a positioning process (including all of the transmission of the pulse signal, the reception of the response pulse signal, and the positioning process described in the first embodiment) is performed.

  The gain control unit 303 basically adjusts the gain of the amplification unit 111 according to the correspondence table stored in the storage unit 110, similarly to the gain control unit 109 of the first embodiment. However, the gain control unit 303 sets the gain of the amplification unit 111 to be smaller than the gains at other elapsed times during the elapsed time corresponding to the feature timing. As a result, the amplitude of the fixed arrival wave included in the received signal is made relatively smaller in the amplification unit 111 than the amplitude of the response pulse signal. Therefore, the terminal position calculation unit 113 can accurately separate the response pulse signal and the fixed incoming wave, and as a result, can accurately identify the position of the wireless terminal 200.

  In the above description, addition and averaging processes are performed in the feature extraction unit 301, but an elapsed time profile having the same characteristics as in FIG. 11 can be obtained only by the addition process.

  Further, base station 300 may transmit a reference signal, and a response signal obtained by ASK modulating the reference signal received by wireless terminal 200 may be transmitted. At this time, a series is added to the response signal so that it can be understood that the wireless terminal 200 has returned. The base station 300 determines whether or not a sequence is added to the received signal, so that the received signal is a response signal from the radio terminal 200 or a signal reflected by the fixed element. Can be determined. Even in this way, a fixed incoming wave can be specified.

  As described above, according to the present embodiment, in base station 300, gain control section 303 changes the gain of amplification section 111 only in the elapsed time corresponding to the feature timing detected by incoming wave detection section 302. Set smaller than the gain in elapsed time.

  Thereby, since the signal reflected by the fixed element which becomes a noise component in the positioning process can be made relatively smaller than the response pulse signal, the response pulse signal can be detected with high accuracy. Therefore, the terminal position calculation unit 113 can accurately separate the response pulse signal and the fixed incoming wave, and as a result, can accurately identify the position of the terminal 200.

  The wireless positioning device, the wireless positioning system, and the wireless positioning method of the present invention are useful as those capable of controlling gain in a short time when positioning a plurality of wireless terminals existing at different positions.

The figure which shows the positioning system which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the base station which concerns on Embodiment 1 of this invention. The figure which shows the pulse signal transmitted from a base station, and the response pulse signal (received signal of a base station) corresponding to the said pulse signal Diagram for explaining power attenuation of a propagation signal in a propagation path between a base station and a wireless terminal Diagram showing an example of a positioning system situation FIG. 5 is a diagram showing the reception power of the received pulse signal at the base station with respect to the round trip time in one example of the positioning system shown in FIG. The figure showing the gain (amplification factor) set in the amplifying unit in order to adjust the output level of the amplifying unit to −20 dB when the response pulse signal is received with the received power shown in FIG. The figure which shows the gain change in the transmission pulse signal transmitted from a base station, the response pulse signal received by a base station, and the amplification part of a base station The block diagram which shows the structure of the base station which concerns on Embodiment 2 of this invention. The figure which shows the positioning system which concerns on Embodiment 2 of this invention. The figure which shows the elapsed time profile which plotted the electric power average value obtained by addition and an average process with respect to sampling timing Block diagram showing the configuration of a conventional wireless communication device Gain control flowchart in the wireless terminal device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 Positioning system 100,300 Base station 101 Transmission control part 102 Transmission baseband part 103 Digital analog conversion part 104 Transmission radio | wireless part 105 Transmission antenna 106 Reception antenna 107 Reception radio | wireless part 108 Time measurement part 109,303 Gain control part 110 Storage Unit 111 amplifying unit 112 analog-digital conversion unit 113 terminal position calculation unit 200 wireless terminal 301 feature extraction unit 302 incoming wave detection unit

Claims (11)

A wireless positioning device that measures the position of a terminal using a wireless signal,
A transmission means for transmitting a transmission signal for positioning;
Receiving means for receiving a reception signal generated by receiving and reflecting the transmission signal at the terminal;
An amplifier that amplifies the received signal using a gain according to a set voltage;
Clock means for measuring an elapsed time from a timing at which the transmission signal is transmitted from the transmission means to a timing at which the reception signal is received by the reception means;
A gain control means for setting the set voltage according to the measured elapsed time;
A wireless positioning device comprising: Storage means for storing the relationship between the elapsed time and the gain in the amplifier;
The gain control means reads out a gain value corresponding to the elapsed time output from the clock means from the storage means, and sets it as a gain in the amplifier.
The wireless positioning device according to claim 1. The receiving means is an array antenna having a plurality of antenna elements,
The radio positioning apparatus according to claim 1, further comprising a terminal position calculating unit that calculates an arrival direction of the received signal using a signal group received by the plurality of antenna elements. The transmission means generates and transmits a UWB pulse signal,
The receiving means receives the pulse signal.
The wireless positioning device according to any one of claims 1 to 3. Feature extraction means for extracting features of the received signal received by the reception means;
An arrival wave detection means for detecting the arrival timing of the arrival wave from the characteristics of the extracted received signal;
The gain control means sets the gain in the amplifier to a value smaller than values at other timings only at the arrival timing of the incoming wave detected by the incoming wave detection means.
The wireless positioning device according to any one of claims 1 to 4. A radio positioning device according to any one of claims 1 to 5,
A wireless terminal having a function of receiving a transmission signal for positioning transmitted from the wireless positioning device and retransmitting the signal to the wireless positioning device;
A wireless positioning system. A wireless positioning method for measuring the position of a terminal using a wireless signal,
A transmission step of transmitting a transmission signal for positioning;
A reception step of receiving a reception signal generated by receiving and reflecting the transmission signal at the terminal;
A clock step of measuring an elapsed time from a timing at which the transmission signal is transmitted to a timing at which the reception signal is received;
A setting step of setting a gain adjustment voltage according to the measured elapsed time;
An amplification step of amplifying the received signal using a gain according to the set gain adjustment voltage;
A wireless positioning method. The step of setting, in accordance with the measured elapsed time, reading a corresponding gain value from a table storing a relationship between the elapsed time and the gain;
Setting the gain adjustment voltage according to the read gain value; and
The wireless positioning method according to claim 7. In the reception step, the reception signal is received by an array antenna having a plurality of antenna elements,
The radio positioning method according to claim 7 or 8, further comprising a terminal position calculating step of calculating an arrival direction of the received signal using a signal group received by the plurality of antenna elements. In the transmission step, a UWB pulse signal is transmitted,
In the receiving step, the pulse signal is received;
The wireless positioning method according to any one of claims 7 to 9. A feature extraction step of extracting features of the received signal received in the reception step;
An incoming wave detection step of detecting the arrival timing of the incoming wave from the characteristics of the extracted received signal,
The gain used in the amplification step is set to a value smaller than the value at other timings only at the arrival timing of the arrival wave detected in the arrival wave detection step.
The wireless positioning method according to any one of claims 7 to 10.

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