JP2011145111A - Uwb sensor system and reader device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a reader acquire the ID of a radio tag, while assuring a human body detection distance in a degree of several meters of a radar, by using one receiving system. <P>SOLUTION: A UWB transmission part 310 transmits a UW signal representing a unique word inherent in the reader 300 periodically and intermittently, by using an IR-UWB pulse sequence. A UWB receiving part 320 receives an ID signal representing the tag ID of a tag 200, and a human body echo generated when the UW signal is reflected by a human body fitted with the tag 200. A tag-ID detection part 340 detects the tag ID of the tag 200 from the ID signal. A correlation receiving part 330 calculates a delay profile of the received signal. A two-dimensional profile presumption part 370 calculates two-dimensional power spectra in a delay-time region and a Doppler shift region by using the delay profile. A distance-measurement and living-body detection part 380 detects the human body echo by using the two-dimensional power spectra. Here, the UWB transmission part 310 transmits the UW signal, after the tag ID of the tag 200 is detected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to tag ID detection, ranging / positioning, and living body detection using IR-UWB (Impulse Radio-Ultra Wide Band) wireless communication or radar.

  UWB (Ultra Wide Band) wireless, in addition to high-speed communication utilizing its wide bandwidth, wireless communication with low power consumption by intermittent transmission and reception of pulses with high time resolution, distance measurement based on propagation delay time, biological micromotion It is known that the radar can be used as a radar for detecting noise. In particular, UWB radio that transmits and receives pulses (impulses) with high time resolution is a system different from multiband OFDM (Orthogonal Frequency Division Multiplex) for high-speed communication, and is called IR (Impulse Radio) -UWB.

  For example, Patent Literature 1 and Patent Literature 2 disclose a technique for measuring the distance between wireless devices with high accuracy by utilizing the high time resolution of IR-UWB. In addition, a technology for managing identification information (ID: Identification) and a position of a wireless tag device (hereinafter abbreviated as “wireless tag” or “tag”) using the communication function of IR-UWB is, for example, It is disclosed in Patent Document 3 and Patent Document 4.

  Further, sensor technologies for detecting human movement using IR-UWB as a radar are disclosed in Patent Documents 5 and 6. Sensor technology for detecting biological information such as heartbeat and respiration, which is a similar radar application, is disclosed in Patent Literature 7 and Patent Literature 8. Patent Documents 7 and 8 show that a human body echo that is a detection target can be separated from scattered waves from surrounding objects by controlling the pulse reception gate to limit the detection distance.

  By combining the conventional techniques as described above, it is possible to realize a system in which the ID and position of the person with the wireless tag and the biological information of the person with the tag are linked and acquired. For example, a reader device for tag ID detection (hereinafter abbreviated as “reader”) has a distance measuring function or a radar function, so that the ID of the wireless tag, the position, and the living body of the person who has the wireless tag. This suggests that information can be detected simultaneously.

Japanese Patent No. 4329353 JP 2002-51001 A JP 2008-217074 A JP 2006-170891 A Japanese Patent No. 3471803 Japanese Patent No. 3648236 US Pat. No. 5,573,012 US Pat. No. 5,766,208

Takahashi et al., “Measurement of Ka-band UWB radar cross sections of humans and light vehicles”, 2004 Society Conference of IEICE, AS-4-4. M. D. JUDD, “A Simple, Low-Computation Peak Detection Algorithm for the Angle-of-Arrival Spectrum for,” IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS VOL. 28, NO. 4 OCTOBER 1992. Q. Spencer, B. Jeffs, M. Jensen, and A. Swindlehurst, “Modeling the statical time and angle of arrival characteristics of an indoor multipath channel,” IEEE J. Select. Areas Commun., Vol. 18, pp. 347 -360, Mar. 2000. "Adaptive signal processing by array antenna", Science and Technology Publishing, Nobuyoshi Kikuma

  However, there is a large difference in signal level between the transmitted wave from the tag received by the reader and the human body echo received by the reader during radar operation. FIG. 1 shows a tag transmission wave 10, an adult human body echo 20, and an infant human body echo 30 when it is assumed that the tag and the person (adult and infant) having the tag are equidistant from the reader. The reception level of each is shown. However, the frequency used is 10 GHz, the radar cross section (RCS) of the human body is assumed to be about 0 dBm (DEcibel squared meter) for adults according to Non-Patent Document 1, and the transmission output of the tag and reader is 0 dBm. At this time, at a distance of 5 m, the difference between the reception level of the tag transmission wave and the reception level of the human body echo is 25 dB. Further, when the detection target is an infant, the human body RCS is reduced to about −10 dBsm, so that the reception level difference is 25 dB even at a distance of 1.5 m.

  Moreover, the IR-UWB wireless tag is generally an active tag that autonomously transmits a UWB pulse with a built-in battery, and it is sufficiently assumed that the tag transmission and the radar function of the reader operate simultaneously. That is, the reader of the wireless tag having the radar function, which is the premise of the present invention, needs to receive and process the tag transmission wave and the human body echo having a large level difference at the same time.

  Generally, a detector using a diode is often used for a UWB pulse receiving system because its circuit configuration is simple and can be manufactured at low cost. However, the dynamic range in which linearity is maintained in this diode detector is about 25 dB. Therefore, in order to simultaneously receive and process a tag transmission wave and a human body echo whose reception level difference is very large, the reader needs to have two reception systems with different reception power ranges.

  An object of the present invention is to provide a UWB sensor system and a reader device that can acquire the ID of a wireless tag while ensuring a radar human body detection distance of about several meters using a single receiving system. It is.

  The UWB sensor system of the present invention is a UWB sensor system comprising a tag device and a reader device, and the tag device burst-transmits an ID signal indicating the ID of the tag device using an IR-UWB pulse sequence. And a UWB transmission means for transmitting a UW signal indicating a unique word unique to the reader apparatus, which is periodic and intermittent using an IR-UWB pulse sequence. A UWB receiving means for receiving the ID signal and an echo of the UW signal reflected by a human body wearing the tag device; an ID detecting means for detecting the ID of the tag device from the ID signal; Correlation receiving means for calculating a delay profile of a signal, and two-dimensional power in a delay time domain and a Doppler shift domain using the delay profile A two-dimensional profile estimating means for calculating a spectrum, and a living body detecting means for detecting the human body echo using the two-dimensional power spectrum, wherein the UWB transmitting means is configured to detect an ID of the tag device. The UW signal is transmitted.

  The reader apparatus according to the present invention uses a UWB transmission means for transmitting a UW signal that is periodic and intermittent using an IR-UWB pulse sequence and indicates a unique word unique to the reader apparatus, and an ID of the tag apparatus. An ID signal indicating, a UWB receiving means for receiving a human body echo reflected by the human body wearing the tag device, an ID detecting means for detecting the ID of the tag device from the ID signal, and a received signal A correlation receiving means for calculating a delay profile of the signal, a two-dimensional profile estimating means for calculating a two-dimensional power spectrum in a delay time region and a Doppler shift region using the delay profile, and the human body echo using the two-dimensional power spectrum. And a UWB transmission means that detects the ID of the tag device after the ID is detected. Transmitting a UW signal, a configuration.

  According to the present invention, a reader having a radar function can simultaneously acquire the ID of a person having a tag and its biological information by using only one reception system using a diode detector. That is, it is possible to add a radar function to the reader with a small size and low cost while suppressing an increase in circuit scale.

The figure for demonstrating the level difference of the tag transmission wave and human body echo which are the conventional subjects The figure which shows the whole structure of the UWB sensor system which concerns on Embodiment 1 of this invention. The figure which shows the transmission frame structure of the UWB sensor system which concerns on Embodiment 1. FIG. Diagram for explaining the principle of radar ranging in the UWB sensor system Diagram showing a two-dimensional power spectrum when a person is stationary A diagram showing the two-dimensional power spectrum when a person is walking The block diagram which shows the internal structure of the tag which concerns on Embodiment 1. FIG. The block diagram which shows the internal structure of the reader which concerns on Embodiment 1. FIG. The figure which shows the measurement result of the pulse waveform of IR-UWB in Embodiment 1 The block diagram which shows the internal structure of the reader which concerns on Embodiment 2 of this invention. The figure which shows the whole structure of the UWB sensor system which concerns on Embodiment 3 of this invention. The block diagram which shows the internal structure of the semi-passive tag which concerns on Embodiment 3. FIG. The figure for demonstrating the control method of the semi-passive tag in Embodiment 3 The figure for demonstrating the echo back system in Embodiment 4 of this invention The figure which shows the internal structure of the semi-passive tag which concerns on Embodiment 4.

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

(Embodiment 1)
1) System Overview FIG. 2 is a diagram showing an overall configuration of the UWB sensor system according to Embodiment 1 of the present invention. The UWB sensor system according to the present embodiment is assumed to be used mainly in an indoor environment. Specifically, as shown in FIG. 2, a person 100 to be detected, a tag 200 worn by the person 100, and a reader 300 are provided. FIG. 2 shows a state in which a fixture 101 that is a radio wave reflector is installed in an indoor environment where the UWB sensor system is used. In an actual environment, various fixtures or walls other than the fixture 101 can serve as a reflector of radio waves. However, in order to make the explanation easy to understand, a representative metal fixture 101 is represented below.

  Tag 200 is worn by person 100 and transmits a bit string of tag ID, which is identification information of tag 200, as pulse sequence 102 of IR-UWB. At this time, the pulse sequence 102 is, for example, a bit string of a tag ID that has been subjected to OOK (On-Off-Keying) modulation, which is a binary ASK (Amplitude Shift Keying) modulation method, and this OOK modulation signal is a burst of a certain time length. Only the interval is transmitted.

  The reader 300 has an operation mode of the ID detection function (hereinafter referred to as “ID detection mode”) and an operation mode of the radar function (hereinafter referred to as “radar mode”). In the ID detection mode, the reader 300 detects the ID of the tag 200. In the radar mode, the position of the person 100 or the living body tremor is detected.

  First, the reader 300 is set to the ID detection mode. The reader 300 receives the pulse series 102 transmitted in burst from the tag 200 and demodulates the bit string of the tag ID by detecting the OOK modulation signal. Here, when the tag ID is acquired and the presence of the tag 200 is confirmed, the reader 300 is changed to the radar mode in order to detect the biological information of the person 100 wearing the tag 200.

  The reader 300 transmits a bit string of a reader UW (Unique Word) that is identification information of the reader 300 as an IR-UWB pulse sequence 104. This pulse sequence 104 is a Low-Duty-cycle signal in which, for example, the time width of a single pulse is 2 ns or less and the pulse transmission cycle is 100 ns. That is, the pulse sequence 104 is, for example, a bit string of the reader UW that is OOK-modulated, and this OOK-modulated signal is transmitted only for a burst period of a certain time length, and further repeatedly transmitted in bursts at a certain period.

  The reader 300 repeatedly transmits the pulse sequence 104 intermittently and periodically, and at the same time, a single pulse of the impulse UWB constituting the pulse sequence 104 is reflected by the person 100 wearing the tag 200 and returns to the reader 300. A so-called human body echo pulse sequence 105 is received.

  Here, for example, when the distance of the person 100 from the reader 300 is 3 m, the arrival time τ of the human body echo that becomes the return propagation is about 20 ns based on the transmission time of each pulse. However, the arrival time τ is calculated from τ = d / c [s] using the speed of light c≈2.998 × 1e8 [m / s] for the return propagation distance d = 6 [m]. That is, the reader 300 can measure the distance between the reader 300 and the person 100 by estimating the arrival time τ of the received pulse.

  FIG. 3 is a diagram showing a transmission frame configuration of the UWB sensor system in the present embodiment.

  In FIG. 3A, a pulse series 102 is a tag ID OOK modulation signal using IR-UWB transmitted from the tag 200, and is composed of tag frames 400-1 and 400-2.

  FIG. 3B is a diagram illustrating a detailed configuration of the tag frames 400-1 and 400-2. The tag frames 400-1 and 400-2 include a preamble part for the reader 300 to detect the tag frames 400-1 and 400-2 and establish synchronization at the time of pulse reception, and a data part composed of a bit string of tag IDs. Consists of

  The preamble part is premised on correlation reception by the reader 300, and for example, as shown in FIG. 3B, the pulse part consists of 32 bits of all “1”, and the data part is, for example, a 128-bit pulse series. If this bit string has been previously encoded with transmission path coding by adding parity check bits, the number of bits of the tag ID is smaller than 128 bits. Note that a predetermined known PN (Pseudo Random) sequence may be used as the preamble portion.

  Further, the tag frame including the preamble part and the data part may be burst transmitted twice, for example, in order to increase the detection rate of the tag ID of the tag 200 in the reader 300. That is, if the tag frame 400-1 and the tag frame 400-2 are configured with the same pulse sequence, the reception error rate of the tag ID can be reduced.

  Here, when the reader 300 set in the ID detection mode detects the tag frames 400-1 and 400-2, the setting of the reader 300 is changed to the radar mode.

  FIG. 3C is a diagram illustrating a detailed configuration of the radar frames 410-1 to 410-80.

  In FIG. 3C, a pulse sequence 104 is a pulse sequence transmitted in bursts from the reader 300 in the radar mode. The pulse series 104 is an OOK modulation signal of the reader UW using the impulse UWB, and constitutes the radar frames 410-1 to 410-80. That is, the pulse sequence 104 is a Low-Duty-cycle signal having a pulse transmission cycle of 100 ns, and the reader 300 burst transmits the pulse sequence 104 composed of a bit string corresponding to the UW length.

  In the radar frame 410-1, a non-signal section 430-1 of a certain time is set after a bit string (pulse sequence 104) corresponding to the UW length is transmitted in bursts. After that, as shown in FIG. 3, the pulse sequence 104 (420-n) and the no-signal section 430-n (n = 1, 2,..., 80) are repeated at a constant cycle, for example, for about 2 seconds.

  By providing the no-signal section 430-n in the radar frame 410-n, the influence of interference on multiple systems using the same frequency band can be reduced. In addition to the tag frame from the tag 200, a tag frame transmitted autonomously by another tag present in the detection area of the reader 300 can be detected. That is, by such time division processing, even when a plurality of tags or their holders exist in the detection area of the reader 300, tag ID detection and tag holder distance measurement can be performed simultaneously.

2) Human Body Detection Principle FIG. 4 is a diagram for explaining the principle of radar ranging in the UWB sensor system according to the present embodiment.

  In order to correlate and receive the pulse sequence 105 of the human body echo, the reader 300 repeatedly adds and averages the arriving signal by the number of bits of the reader UW at a constant delay time τ from the transmission timing of each pulse for a period of 100 ns. In addition, the reader 300 can calculate a delay profile by so-called sliding correlation processing in which the correlation time is received while shifting the delay time τ with a constant time resolution.

  Actually, the reader 300 performs an averaging operation only when the bit information is 1, since the transmitted pulse series 104 is a known UW OOK modulation signal. Further, the receiving system of the reader 300 can reproduce the pulse waveform by sampling the pulse waveform with a receiving system time width of about 2 ns, for example, at 1 GHz. At this time, the time resolution of the delay profile obtained by the sliding correlation process is 1 ns, and the distance resolution as the radar dynamic ranging operation is 15 cm.

  On the other hand, the environment in which the UWB sensor system according to the present embodiment is used is mainly indoors. For example, a medical facility or a home is assumed as the operating environment. For example, as shown in FIG. 2, in the actual propagation environment, it is difficult to ignore the presence of the fixture 101 at a relatively short distance from the reader 300. That is, the reader 300 simultaneously receives a pulse sequence 106 of a reflected wave reflected by the fixture 101 (hereinafter abbreviated as “fixture reflected wave”) in addition to the pulse sequence 105 of the human body echo.

  The human body echo reflected from the person 100 has a slow fluctuation component caused by respiration. When the impulse UWB signal transmitted from the reader 300 is, for example, a signal having a center frequency of 10 GHz, the fluctuation component due to respiration is observed as a so-called Doppler shift component of about 1 Hz. When the person 100 is a pedestrian, a Doppler shift component of about 10 Hz simultaneously exists in addition to a Doppler shift component of about 1 Hz due to respiration. That is, the human body echo has a power spectrum in the Doppler shift region in a specific delay time in addition to the delay profile that is the power spectrum in the delay time region described above. On the other hand, the reflected wave from the fixture 101 has no Doppler shift, in other words, the Doppler shift is 0 Hz. That is, based on the Doppler shift, the human body echo and the fixture reflected wave can be identified.

  Further, in general, for detecting a human heartbeat, it is necessary that a transmission radio wave reaches the heart in the body and propagates back, so that realization becomes difficult as the frequency used as a radar increases. On the other hand, since human breathing and walking can be detected by fluctuations in the human body surface, the high microwave band and the millimeter wave band are also useful, and the frequency dependence is small. Therefore, the main purpose of the UWB sensor system of the present invention is to detect fluctuation components caused by breathing and walking as biological information.

  5A and 5B are diagrams for explaining the principle of biological microtremor measurement in the UWB sensor system according to the present embodiment. 5A and 5B are diagrams illustrating typical examples of the delay time and the Doppler shift two-dimensional power spectrum obtained when the human body echo and the fixture reflected wave exist simultaneously. FIG. 5A shows a two-dimensional power spectrum when the person 100 is stationary. FIG. 5B shows a two-dimensional power spectrum when the person 100 is walking. Here, it is assumed that the fixture 101 is at a distance of 4 m from the reader 300 and the fixture reflected wave is a totally reflected wave at a distance of 4 m. Further, the reception level of the human body echo is estimated by the radar equation as RCS0 dBsm as shown in FIG. It is assumed that the person 100 is at a distance of 3 m from the reader 300.

  The physical characteristics as described above suggest that human body echoes can be detected with high accuracy by observing the two-dimensional power spectrum even under conditions where strong fixture reflected waves exist. This means that by measuring the fine movement component due to breathing, not only can the distance between the person and the wall be realized, but also the information about the breathing state of the person 100 whose two-dimensional power spectrum is to be detected is also presented. Will be.

  That is, by making it possible to automatically observe the spectrum shape in the Doppler shift region or its temporal variation characteristic, it is possible to realize application in the medical field such as monitoring an apnea state during sleep.

  5A and 5B depict only the principal components of the analytically calculated delay time and Doppler shift, and the actually observed spectrum is further increased by a large number of scattered waves or complicated movements of the human body. In general, the shape is more complicated due to the noise component of the device. In an actual system, an algorithm for extracting a principal component from such a complex spectrum shape is required, and the spectrum peak detection method of Non-Patent Document 2 and the path identification algorithm employed in Non-Patent Document 3 are effective. .

3) Tag Device Configuration FIG. 6 is a block diagram showing an internal configuration of the tag 200 according to Embodiment 1 of the present invention.

  The ID transmission unit 220 includes a UWB pulse generation unit 221 and an amplifier 222.

  The UWB pulse generation unit 221 generates a pulse sequence according to the bit string of the tag ID that is identification information of the tag 200. For example, the UWB pulse generator 221 generates an OOK modulation signal according to the bit string of the tag ID. This OOK modulation signal is an ID signal (tag transmission wave) indicating the tag ID of the tag 200. As described with reference to FIG. 3, the tag 200 generates an OOK modulated signal only for a burst section having a fixed time length.

  The amplifier 222 amplifies the ID signal and transmits it via the antenna 210.

  In this way, the ID transmission unit 220 transmits an ID signal (tag transmission wave) indicating the tag 200 tag ID as the IR-UWB pulse sequence 102.

4) Reader Device Configuration FIG. 7 is a block diagram showing an internal configuration of the reader 300 according to Embodiment 1 of the present invention.

  The antenna 301 transmits and receives IR-UWB RF (Radio Frequency) signals.

  The RF switch 302 is inserted between the transmission / reception system of the antenna 301 and the reader 300, and is shared by one antenna 301 by switching the transmission / reception system.

  The UWB transmission unit 310 includes a transmission pattern generation unit 311, an SRD (Step Recovery Diode) circuit 312, a band pass filter (BPF: Band Pass Filter) 313, and an amplifier (PA: Power Amplifier) 314.

  The transmission pattern generation unit 311 generates, for example, a 10 MHz rectangular signal as a pattern signal corresponding to the transmission pulse series 104. At this time, the transmission output is ON corresponding to the UW bit string by D / A converting the digital signal of the UW bit string of the reader 300 output from the mode setting / control unit 350 described later to an analog signal. A 10 MHz rectangular signal that is turned off is obtained.

  The SRD circuit 312 receives a 10 MHz rectangular signal output from the transmission pattern generation unit 311 and generates a signal in which the edge component is extracted and emphasized, that is, a so-called edge shock excited signal. The signal generated by the SRD circuit 312 is, for example, a UWB signal that extends to the microwave band.

  The band pass filter 313 extracts a required band of the system from the UWB signal output from the SRD circuit 312. This required band determines the pulse width of the IR-UWB to be transmitted.

  The amplifier 314 amplifies the IR-UWB signal power output from the bandpass filter 313 within a range satisfying -41.3 dBm / MHz or less, which is the legal regulation (ARIB STD-T91). The amplified IR-UWB RF signal is transmitted from the antenna 301 via the RF switch 302.

  In this way, the UWB transmission unit 310 transmits a periodic and intermittent UW signal using the IR-UWB pulse sequence.

  The UWB reception unit 320 includes an LNA (Low Noise Amp) 321, a gain adjustment circuit 322, a detection circuit 323, a signal shaping circuit 324, and an A / D conversion unit 325.

  The LNA 321 receives an IR-UWB RF signal received by the antenna 301 and receives the RF signal of the IR-UWB via the RF switch 302 and amplifies the signal power by about 20 dB while satisfying a required NF (Noise Figure) of the system. Normally, the NF required for the LNA 321 is about 3 dB in the microwave band.

  The gain adjustment circuit 322 adjusts the received signal power so as to be within the input dynamic range of the detection circuit 323 at the subsequent stage, in accordance with the assumed power of the received signal output from the LNA 321. Specifically, when the reader 300 is set to the ID detection mode and receives a burst signal from the tag 200, the gain adjustment circuit 322 attenuates the received signal power by about 20 to 25 dB. This is because a level difference of about 20 to 25 dB occurs between the human body echoes 20 and 30 and the tag transmission wave 10 as shown in FIG. When set to, the gain is controlled to be maximum.

  The detection circuit 323 includes a detector using a diode, and performs envelope detection on the IR-UWB reception signal that is output from the gain adjustment circuit 322. FIG. 8 shows an example of a received waveform of IR-UWB that is actually envelope-detected by the detection circuit 323. This figure shows the result of envelope detection by the detection circuit 323 after adjusting the transmission waveform shown in FIG. 3 to an appropriate signal power.

  The signal shaping circuit 324 adjusts the signal waveform and the signal power before inputting the output signal from the detection circuit 323 to the A / D conversion unit 325 in the subsequent stage. This signal shaping circuit 324 is composed of an LPF and a buffer amplifier, and in order to match the envelope detected pulse waveform to the sampling frequency and input dynamic range of the A / D converter 325, the LPF cutoff frequency and the buffer amplifier The gain of has been optimized.

  The A / D conversion unit 325 converts the output from the signal shaping circuit 324 into a digital signal with a sampling frequency of 1 GHz, for example, as an input signal. This sampling frequency is a parameter related to ranging performance when the reader 300 operates in the radar mode. The frequency of a periodic signal that can be reproduced by 1 GHz sampling is theoretically 500 MHz, and the pulse width of the impulse UWB signal is about 2 ns, although it depends on the signal waveform. The A / D converter 325 outputs the digital signal to the correlation receiver 330 and the tag ID detector 340.

  As described above, the UWB receiving unit 320 receives the ID signal and the human body echo reflected from the human body on which the tag 200 is mounted.

  Correlation receiving section 330 receives the sample value of the pulse waveform obtained by A / D conversion section 325 as an input, and generates a delay profile. As described above with reference to FIG. 4, a delay profile can be calculated by so-called sliding correlation processing in which correlation reception is performed while shifting at a constant time resolution.

  In the initial state, the reader 300 is set to the ID detection mode in order to receive the tag frames 400-1 and 400-2. The tag frames 400-1 and 400-2 include a preamble part for the reader 300 to establish frame synchronization and a data part composed of a bit string of tag ID. Therefore, the reader 300 needs to detect a preamble by correlation reception in order to establish synchronization with the tag frames 400-1 and 400-2.

  Correlation receiving section 330 stores the received data for the length of the tag frame in the internal memory, and shifts the received data in time while the preamble section of tag frames 400-1 and 400-2 at the pulse transmission cycle of tag 200. The delay profile is calculated by averaging the number of bits. For the peak value of the delay profile, a spreading gain for the number of bits of the preamble, for example, 32 bits is secured.

  Tag ID detection section 340 determines the reception timing of the data section in tag frames 400-1 and 400-2 based on the peak value of the delay profile for the preamble section acquired by correlation reception section 330. In addition, the tag ID detection unit 340 performs threshold determination on the received signal that is OOK-modulated at the reception timing, and binarizes the received signal. The data part of the tag frames 400-1 and 400-2 is composed of, for example, 128 bits including a tag ID. The detection unit 340 performs error detection or error correction processing. Also, as shown in FIG. 3, when the tag frame 400-1 and the tag frame 400-2 are the same frame and the same frame is repeated twice, the same processing is performed for two frames. , Tag ID detection errors can be reduced. The tag ID detection unit 340 outputs the tag ID detection result to the mode setting / control unit 350. In addition, the tag ID detection unit 340 outputs the reception timing of the data part in the frames 400-1 and 400-2 to the common memory 360.

  The mode setting / control unit 350 changes the reader 300 to the radar mode when the tag ID is detected by the tag ID detection unit 340. That is, at the same time as setting the gain of the gain adjustment circuit 322 to the maximum value, the digital signal of the UW bit string of the reader 300 is output to the transmission pattern generation unit 311 described above. At the same time, the mode setting / control unit 350 connects the RF switch 302 to the PA 314 in synchronization with the digital signal of the UW bit string. Further, the mode setting / control unit 350 changes the setting of the correlation receiving unit 330 so as to store the reception data corresponding to the radar frame length when the correlation receiving unit 330 executes the sliding correlation process.

  As described above, the pulse sequence 104 transmitted from the reader 300 in the radar mode is a UW OOK modulation signal using IR-UWB, and the pulse sequence 104 is a Low-Duty- having a pulse transmission period of 100 ns. This is a cycle signal, which is a bit string signal corresponding to the UW length. In the radar frame 410-1, after a pulse sequence 104 (pulse sequence 203-1) is transmitted in bursts, a no-signal section 430-1 of a certain time is set, and thereafter, as shown in FIG. i and the no-signal section 430-i (i = 2, 3,..., 80) are repeated at a constant cycle, for example, for about 2 seconds.

  The correlation receiver 330 stores the received data for the length of the radar frame in its internal memory, and adds and averages the number of bits of the radar frame in the pulse transmission cycle of the reader 300 while shifting the received data with time. Calculate the delay profile. This delay profile has a power spectrum with a delay time resolution of, for example, 1 ns and a transmission pulse period of 100 ns as a maximum delay time.

  As shown in FIG. 3, the radar mode reader 300 repeats the same frame 80 times up to the radar frame 410-1, radar frame 410-2,..., Radar frame 410-80 with a transmission period of 25 ms. Send for 2 seconds. The delay profile calculated for each radar frame is output to the common memory 360 and temporarily stored. Therefore, the power spectrum for the Doppler shift of the received signal can be obtained by performing a Fourier transform using the time sample for each transmission period. The frequency resolution of this power spectrum is 0.5 Hz, and the maximum frequency is 20 Hz.

  The common memory 360 temporarily stores a delay profile calculated for each radar frame, and outputs the stored delay profile to the two-dimensional profile estimation unit 370.

  The two-dimensional profile estimation unit 370 executes FFT (Fast Fourier Transform) processing using the power values of the same delay time as a total of 80 time samples in the delay profile obtained every 25 m of the radar frame transmission period. By the conversion process from the time domain to the frequency domain, the power spectrum of the Doppler shift for the same delay time can be estimated. However, in frequency spectrum estimation, it is common to perform a Fourier transform process after obtaining an autocorrelation function for a time sample of a power value. Therefore, also in this embodiment, the two-dimensional profile estimation unit 370 can improve the estimation accuracy by calculating the autocorrelation function in advance and then performing the FFT process. However, if the number of time samples when calculating the autocorrelation function is 80, the total number of samples is ideally about 10 times that, and here, the radar frame is repeated 800 times and transmitted for 20 seconds. Become.

  The distance measurement / biological detection unit 380 receives the power spectrum of the Doppler shift for each delay time generated by the two-dimensional profile estimation unit 370 as an input, and performs a distance measurement based on the delay time and a biological detection process focusing on a specific Doppler shift amount. And execute. Specifically, as shown in FIG. 5, when the frequency used as a radar is 10 GHz, a Doppler shift component of about 1 Hz due to respiration exists in an echo from a stationary person. In addition to the Doppler shift component due to respiration, an echo from a person walking has a Doppler shift component of about 10 Hz, for example, depending on the walking speed. Based on such prior knowledge, focusing on the fluctuation component due to breathing of the human body echo or the fluctuation component due to walking, the distance measurement / biological detection unit 380 detects the main component related to the human body echo from the two-dimensional power spectrum. Then, the distance measurement / living body detection unit 380 calculates the distance measurement result to the human body from the delay time indicated by the detected principal component, and obtains the living body detection result regarding breathing or walking from the Doppler shift.

  Further, the distance measurement / biological detection unit 380 reads the tag ID detection result stored in the common memory 360, links the distance measurement result and the biological detection result, and outputs the result as sensor information 390 to the outside of the reader 300. .

  Thus, in the present embodiment, the tag 200 first spontaneously burst transmits the tag ID using the IR-UWB pulse sequence. At this time, the reader 300 is initially set to the tag ID detection mode, and receives the tag transmission wave in bursts to detect the tag ID.

  Next, the reader 300 that has detected the tag ID is changed to the radar mode and periodically and intermittently transmits a reader unique word using an IR-UWB pulse sequence. At this time, the reader 300 calculates the delay profile by performing sliding correlation reception on the basis of the known reader UW for the human body echo that is returned by the human body wearing the tag 200. In addition, the reader 300 performs Fourier transform on the discrete time samples of the delay profile calculated in the burst transmission period, and simultaneously calculates the power spectrum in the Doppler shift region. Using the two-dimensional power spectrum of the delay time region and the Doppler shift region obtained here, the reader 300 detects biological information such as a respiratory fluctuation component of the tag wearer.

  By using such a method, the reader 300 receives the tag transmission wave and the human body echo in a time-sharing manner, so that the gain of the receiving system can be optimally controlled according to each operation mode. As a result, the reader 300 can realize the ID detection and the radar function at the same time only by providing one receiving system.

  As described above, according to the present embodiment, UWB transmission section 310 transmits a UW signal that is periodic and intermittent using an IR-UWB pulse sequence and that indicates a unique word unique to reader 300. The UWB receiver 320 is a signal transmitted in burst from the tag 200, and an ID signal (tag transmission wave) indicating the tag ID of the tag 200 using an IR-UWB pulse sequence, and the UW signal is transmitted to the tag 200. And a human body echo reflected from the human body wearing the tag ID detector 340 detects the tag ID of the tag 200 from the ID signal, the correlation receiver 330 calculates a delay profile of the received signal, The two-dimensional profile estimation unit 370 calculates a two-dimensional power spectrum in the delay time region and the Doppler shift region using the delay profile, and the distance measurement / biological detection unit 380. , To detect the human body echo using a two-dimensional power spectrum of the delay time domain and Doppler shift region. Here, the UWB transmission unit 310 transmits the UW signal after the tag ID of the tag 200 is detected.

  As a result, the reception period in which the ID signal (tag transmission wave) indicating the tag ID of the tag 200 is received does not overlap with the reception period in which the UW signal receives the human body echo reflected by the human body wearing the tag 200. The UWB receiving unit 320 can be used in a time-sharing manner. That is, the reader 300 having a radar function includes only one system of UWB reception processing units using a diode detector, so that ID detection and distance measurement for a person having the tag 200 and the person having the tag 200 can be performed. Biological information can be linked and acquired at the same time.

(Embodiment 2)
In this embodiment, a reader device that can estimate the direction of arrival will be described. Note that the configurations of the UWB sensor system and the tag device according to the present embodiment are the same as those of the first embodiment, and thus description thereof is omitted.

  FIG. 9 is a block diagram showing an internal configuration of the reader according to the present embodiment. In FIG. 9, the same components as those in FIG. The reader 500 according to the present embodiment in FIG. 9 has a configuration in which a correlation receiving unit 510 is provided instead of the correlation receiving unit 330 and an arrival direction estimating unit 530 is added to the reader 300 in FIG. Correlation receiving section 510 calculates a delay profile of the received signal in the same manner as correlation receiving section 330. Further, as described in Embodiment 1, the reader 300 has functions of ID detection, distance measurement, and living body detection, and estimates arrival time (reception timing). Therefore, a configuration unit having the same configuration as that of the reader 300 will be described below as the arrival time estimation unit 520. A method for estimating the arrival time will be described later.

  The arrival direction estimation unit 530 includes antennas 531-1 to 531-4, a reception processing unit 540, a correlation matrix calculation unit 550, and an arrival direction calculation unit 560. The reader 500 determines the direction in which the person 100 or the tag 200 exists. presume.

  IR-UWB signals of human body echoes transmitted from the reader 500 and reflected by the person 100 are received by the four antennas 531-1 to 531-4 constituting the array antenna in the arrival direction estimation unit 530. However, in order to estimate the direction of the incoming radio wave two-dimensionally, that is, to simultaneously estimate azimuth and elevation, it is necessary to arrange three or more antennas constituting the array antenna. Therefore, in this embodiment, the description is made assuming that the number of antennas is four.

  The antennas 531-1 to 531-4 are narrowband antennas that receive a part of the IR-UWB band. When estimating the direction of arrival of radio waves, as a basic principle, the phase error between each antenna system becomes the estimation result error of the direction of arrival estimation, so the phase error between antenna systems is managed within the desired error range by calibration etc. There is a need to. For this reason, in a wideband signal such as UWB, it is necessary to manage the phase accuracy in all bands of the wideband, which is difficult to realize.

  As the simplest example of the narrowband signal, a single continuous wave (hereinafter referred to as “CW: Continuous Wave”) signal included in the IR-UWB signal can be used. The UWB signal in the IR-UWB system is generated when an edge signal having a frequency oscillated by a crystal oscillation circuit on the transmission side passes through a band-pass filter. For example, if the frequency of the crystal oscillator is 10 MHz, the IR-UWB signal has a CW of 10 MHz intervals in the microwave UWB lower band 3.4 to 4.8 GHz or the UWB upper band 7.25 to 10.25 GHz. It can be thought of as a lined signal. Therefore, in this embodiment, for example, an IR-UWB signal can be handled as a 10 GHz CW, and the center frequency of each of the antennas 531-1 to 531-4 constituting the array antenna can be set to a frequency of 10 GHz.

  In addition, although the above assumes the use of microwave UWB, the UWB sensor system in the present embodiment uses a quasi-millimeter 25 GHz band or a millimeter-wave 60 GHz band / 77 GHz band as the IR-UWB radio frequency band. It is also possible to use it.

  A signal received by each antenna is subjected to a windowing process of a reception time of about several ns to several tens of ns using the RF switches 532-1 to 532-4. This windowing process means ON / OFF control of the RF switches 532-1 to 532-4 using the reception timing of the radar frame 410-1 extracted by the correlation receiving unit 510. In other words, in the present embodiment, correlation reception section 510 determines a reception timing by specifying a desired pulse based on the calculated delay profile, and determines the reception time for RF switches 532-1 to 532-4. Timing control signals 7200 to 710-4 for windowing are output.

  Further, the correlation receiving unit 510 can perform ON / OFF control of the RF switches 532-1 to 532-4 using the synchronization timing of the tag frames 400-1 and 400-2. In this case, correlation receiving section 510 generates similar timing control signals 7200 to 710-4 using the detection timing of the preamble part of tag frames 400-1 and 400-2 as the reception timing. Thus, when the RF switches 532-1 to 532-4 receive the data part of the tag frames 400-1 and 400-2, the windowing process based on the detection timing of the preamble part is executed. Become.

  The reception signals of the antennas 531-1 to 531-4 are output to the subsequent reception processing unit 540, for example, multiplied by a reception time window of several ns.

  The reception processing unit 540 includes LNAs 541-1 to 541-4, band pass filters (BPF) 542-1 to 542-4, down converters 543-1 to 543-4, and A / D conversion units 544-1 to 544. -4.

  The received signals windowed by the RF switches 532-1 to 532-4 are amplified by the LNAs 541-1 to 541-4 and output to the bandpass filters 542-1 to 542-4.

  The windowed received signal passes through the bandpass filters 542-1 to 542-4 and is subjected to interference cancellation, and then is subjected to IF (Intermedeate Frequency) signals or IQ (In-Phase) by the down converters 543-1 to 543-4. / Quadrature-Phase) converted to baseband signal. For example, the IF signal is converted into an IF signal of 10 MHz. In this case, the local signal is a signal separated by 10 Mz above or below 4 GHz / 8 GHz, and it is desirable to use an image rejection mixer in order to remove adjacent images. When converted to an IQ baseband signal, since there is no image signal, the adjacent CW signal is cut by a baseband filter having a cutoff frequency of about 5 MHz.

  The IF signals or IQ baseband signals generated by the down converters 543-1 to 543-4 are input to the A / D conversion units 544-1 to 544-4, converted into digital signals, and then to the correlation matrix calculation unit 550. Entered.

  The A / D converters 544-1 to 544-4 receive these four IF signals or eight IQ baseband signals as input, and are discrete-time sample values that are associated with the antennas 531-1 to 531-4. The digital signal is converted into four or eight digital signals.

  Correlation matrix calculation section 550 calculates correlation matrix RXX based on the received signals of antennas 531-1 to 531-4 constituting the array antenna. That is, a correlation matrix RXX for the array antenna is calculated using digital signals associated with the antennas 531-1 to 531-4.

  When the pulse is an OOK-type IR-UWB, since the signal has a DC component, the covariance for subtracting the signal average component from the correlation matrix is generally calculated. In addition, when the pulse is bi-phase IR-UWB, since the signal does not have a DC component, a correlation matrix may be generally used. The correlation matrix or covariance matrix is stored in the memory in the correlation matrix calculation unit 550.

  Further, the arrival direction calculation unit 560 receives the correlation matrix RXX as an input, and executes, for example, processing related to eigenvalue decomposition of a matrix necessary for the MUSIC (MUltiple SIgnal Classification) method or inner product with the array manifold, and Output direction estimation results. However, as the algorithm used for direction estimation, a beamformer method, a CAPON method, and the like are useful in addition to the MUSIC method. However, in the present embodiment, these algorithms are not limited. Note that the estimation algorithms such as the beam former method and the CAPON method are described in detail in Non-Patent Document 4.

  By the way, as shown in FIG. 3, the direction-estimated incoming radio wave is either the human body echo pulse sequence 106 or the tag transmission wave pulse sequence 102. When the array antenna receives these IR-UWB pulse sequences, it uses the reception timing determined in the correlation reception of the radar frame or the tag frame, and performs a windowing process of a reception time of about several ns to several tens of ns. Is running. In this windowing process, a specific IR-UWB pulse signal can be cut out and received as a desired path from a multipath whose existence cannot be ignored in the indoor propagation environment assumed by the UWB sensor system of the present invention. That is, when such windowing is not performed, multiple multipaths are received simultaneously. In this case, in principle, more antennas are required than the number of multipaths in order to separate these many incoming radio waves and estimate the direction.

  Therefore, the reader 500 according to the present embodiment narrows the band of the IR-UWB reception signal in the array antenna and the function of determining the reception timing by correlation reception of the IR-UWB reception signal and estimating the delay time thereof. By simultaneously having the function of estimating the direction of the incoming radio wave so that the phase is detected, the arrival direction estimation of IR-UWB with high accuracy can be realized with a small number of antennas.

  As described above, according to the present embodiment, correlation reception section 510 generates a timing control signal that adjusts the reception timing of the pulse sequence based on the delay profile. The RF switches 532-1 to 532-4 control the reception time windows of the array antennas 531-1 to 531-4 using the timing control signal, and the reception processing unit 540 includes the RF switches 532-1 to 532-2. 4, each reception signal via 4 is narrowed and sampled, and correlation matrix calculation section 550 calculates a correlation matrix for array antennas 531-1 to 531-4 using the sampling signal obtained by reception processing section 540. The arrival direction calculation unit 560 estimates the direction of the pulse sequence that arrives in the reception time window using the correlation matrix.

  As a result, the reader 500 can estimate the two-dimensional direction in which the person 100 or the tag 200 exists in addition to the ID detection of the tag 200. Therefore, the UWB sensor system according to the present embodiment can detect tag ID, three-dimensional positioning, and biological information by combining the functions of ranging and biological information detection of the person 100 holding the tag 200 shown in the first embodiment. Detection is realized at the same time.

(Embodiment 3)
In the present embodiment, a case will be described in which a wireless tag configuring a UWB sensor system is a battery-driven semi-passive tag that transmits a tag ID signal as a re-radiation pulse only when a beacon signal is received from a reader. Specifically, in the present embodiment, when a semi-passive tag is used, a control method for enabling a reader to simultaneously detect a tag transmission wave and a human body echo using one UWB reception system. explain.

  FIG. 10 is a diagram showing an overall configuration of a UWB sensor system using the semi-passive tag 600 according to the present embodiment. In FIG. 10, a semi-passive tag 600 receives IR-UWB beacon signals transmitted from a reader 700 continuously or periodically. This beacon signal is, for example, the pulse sequence 104 included in the radar frames 410-1 to 410-80 shown in FIG. 3, and is transmitted in bursts intermittently and periodically.

  The internal configuration of the reader 700 according to the present embodiment is the same as that of the reader 300 according to the first embodiment or the reader 500 according to the second embodiment, and a description thereof will be omitted. In reader 700 according to the present embodiment, UWB transmission section 310 transmits a beacon signal in addition to the UW signal.

  FIG. 11 is a block diagram showing an internal configuration of the semi-passive tag 600 according to the present embodiment.

  The semi-passive tag 600 includes an antenna 610, a circulator 620, a reception unit 630, a control unit 640, and an ID transmission unit 650.

  The receiving unit 630 includes an LNA 631, a detector 632, a comparator 633, and a received power estimation unit 634.

  The LNA 631 amplifies the IR-UWB signal received by the antenna 610 and passed through the circulator 620. The amplification degree in the LNA 631 is sufficient to operate the detector 632 and the comparator 633 in the subsequent stage.

  The detector 632 detects an envelope of the amplified IR-UWB signal using a diode, and outputs the signal after the envelope detection to the comparator 633 and the received power estimation unit 634.

  The comparator 633 digitizes the signal after the envelope detection. The signal generation timing of the transmission pulse re-radiated from the semi-passive tag 600 is generated by the digital binarized signal. The comparator 633 outputs the generated signal generation timing to the control unit 640. Note that the semi-passive tag 600 can detect the reader UW based on the digital binarized signal.

  Received power estimation section 634 estimates received signal power using the signal after envelope detection.

  In this way, the receiving unit 630 receives a pulse sequence from the reader 700, and executes processing such as reception power estimation and UW (Unique Word) detection of the reader 700.

  The control unit 640 generates a transmission timing control signal and a transmission level control signal for controlling transmission timing and transmission power based on the information acquired by the receiving unit 630. A method for generating a control signal in the control unit 640 will be described later.

  The ID transmission unit 650 includes a buffer amplifier 651, a step recovery diode 652, and a band pass filter 653.

  The buffer amplifier 651 receives the transmission timing control signal, the tag ID bit string, and the transmission level control signal from the control unit 640. The buffer amplifier 651 is switched ON / OFF at a frame period depending on whether each bit of the tag ID (consisting of a plurality of bits) is 1 or 0. The frame start timing is based on a transmission timing control signal from the control unit 640. Thereby, the tag ID is superimposed on the comparator output. Further, the buffer amplifier 651 sets the amplification degree according to the transmission level control signal from the control unit 640.

  The step recovery diode 652 generates an impulse through the current when the output of the buffer amplifier 651 falls.

  The bandpass filter 653 limits the band so that the impulse generated by the step recovery diode 652 satisfies the UWB spectrum mask.

  The impulse after the band limitation is radiated from the antenna 610 through the circulator 620.

  In this way, the ID transmission unit 650 adjusts the transmission timing and transmission power of the tag ID based on the transmission timing control signal and the transmission level control signal, and transmits the IR-UWB ID signal (tag transmission wave). To do. The transmitted ID signal (tag transmission wave) is, for example, a pulse sequence of the tag frames 400-1 and 400-2 shown in FIG. 3, and two frames are continuously transmitted.

  FIG. 12 is a diagram for explaining a control method of the semi-passive tag 600 according to the third embodiment of the present invention. The re-radiation pulse received from the semi-passive tag 600 and the reflected pulse from the human body are received by the reader 700. The arrival time difference is shown. Here, the re-radiation pulse is an ID signal (tag transmission wave) indicating the tag ID of the semi-passive tag 600.

  As shown in FIG. 12, the re-radiation pulse from the semi-passive tag 600 is controlled by the control unit 640 so that the arrival time is given a certain delay with respect to the reflected pulse from the human body. The reader 700 can receive the data. Moreover, since the control part 640 also controls transmission power simultaneously, in the reader | leader 700, the re-radiation pulse from the semi-passive tag 600 and the reflected pulse from a human body can be made into comparable reception power.

  Specifically, control unit 640 generates a transmission level control signal for controlling the transmission power of the re-radiation pulse based on the reception power estimation result acquired by reception power estimation unit 634 of reception unit 630. In addition, the control unit 640 determines a transmission timing that gives a delay of about several ns to several tens ns, and outputs a transmission timing control signal corresponding to the determined transmission timing to the ID transmission unit 650. As a result, the semi-passive tag 600 transmits a tag frame whose transmission timing and transmission power are controlled.

  In this way, the control unit 640 controls the transmission timing and transmission power of the semi-passive tag 600, so that a re-radiation pulse (tag transmission wave) from the semi-passive tag 600 and a reflected pulse from the human body are required. The signals are received with a delay time difference and with the same reception power. Therefore, the reception power difference between the re-radiation pulse (tag transmission wave) and the human body echo is reduced, and the reader 700 does not receive the restriction on the dynamic range of the diode detector in the UWB reception unit 320, and the tag transmission wave and the human body echo are transmitted. It will be possible to receive. Furthermore, by controlling the transmission timing of the tag transmission wave by the control unit 640, an arrival time difference that can sufficiently separate the tag transmission wave and the human body echo is given on the delay profile.

  As described above, according to the present embodiment, the reader 700 transmits a beacon signal using an IR-UWB pulse sequence, and the semi-passive tag 600 uses a IR-UWB pulse sequence. An ID transmission unit 650 that burst transmits an ID signal indicating an ID of 600, a reception unit 630 that receives a beacon signal, and an ID signal based on the received power of the beacon signal when the reception unit 630 receives the beacon signal. And a control unit 640 for controlling the transmission power of the receiver. Thereby, since the transmission power of the tag ID transmitted from the semi-passive tag 600 can be controlled, the reception power of the tag transmission wave and the human body echo can be kept within the dynamic range of the UWB reception system of the reader. As a result, the reader 700 can acquire the ID of the wireless tag while ensuring the radar human body detection distance of about several meters using one receiving system.

  In the above description, the case where the beacon signal transmitted continuously or periodically from the reader 700 is an OOK modulation signal of the reader UW using the impulse UWB has been described. However, the present invention is not limited to this. The beacon signal may be transmitted in bursts periodically.

(Embodiment 4)
In the present embodiment, as in the third embodiment, a case where the wireless tag configuring the UWB sensor system is a semi-passive tag will be described. The overall configuration of the UWB sensor system according to the present embodiment is the same as that shown in FIG. The semi-passive tag according to the present embodiment uses an IR-UWB echo back method.

  First, an IR-UWB echo back method will be described.

  In the echo back method, the tag receives a pulse sequence continuously transmitted from a reader, superimposes the ID information of the terminal itself on the received pulse sequence, and transmits the pulse sequence as a re-radiation pulse. When transmitting the re-radiation pulse, the tag operates as if it is a reflector for a single pulse, and as a result, a pulse sequence synchronized with the reference clock of the reader is transmitted from the tag. Thus, in the echo back method, it is not necessary to regenerate the reference clock inside the tag, so that the transmission timing of the re-radiation pulse transmitted from the tag can be stabilized. That is, in the third embodiment, as shown in FIG. 11, the semi-passive tag 600 includes the control unit 640 that generates the transmission timing control signal and the transmission level control signal, whereas in the present embodiment, the tag Since the echo back method is used, as described later, the control unit 640A is equivalent to generating a control signal with constant transmission timing and controlling transmission power.

  FIG. 13 is a diagram for explaining the echo back method, and shows a transmission frame configuration of a tag ID signal using IR-UWB.

  The tag amplifies the pulse sequence received by the antenna and re-radiates the amplified pulse sequence. At this time, the tag ID is superimposed on the re-radiated pulse series. For example, depending on whether each bit of the tag ID (consisting of a plurality of bits) is 1 or 0, the tag ID is set as a bit string that is ASK modulated in the frame period by switching the amplifier in the tag on / off in the frame period Can be superimposed. However, one frame is a pulse sequence that is OOK-modulated on the basis of a reader-specific UW consisting of, for example, 128 bits. In this way, the tag operates like a reflector for a single pulse, and re-radiates with its own ID information superimposed on the pulse sequence.

  The reader receives the pulse sequence re-radiated from the tag, and executes a sliding correlation reception process with a known UW. Such correlation reception can ensure a coding gain according to the length of the UW.

  As described above, the reader can estimate the arrival time of the tag return wave using the correlation value obtained by the correlation reception by using the method in which the tag echoes the received pulse and transmits the ID information. That is, the reader can measure the distance between the reader and the tag. This arrival time estimation process means that the pulse sequence received by the tag is re-radiated based on the time when the reader transmitted the pulse sequence, and the elapsed time until the time when the reader receives the pulse sequence again is estimated. . Based on this arrival time estimation result and the speed of light, the distance from the reader to the tag can be calculated.

  Furthermore, the reader detects the tag ID superimposed on each pulse sequence by performing bit determination of the pulse sequence re-radiated from the tag.

  In such an echo back scheme assumed in the fourth embodiment, the delay time is estimated by re-radiating the IR-UWB signal transmitted from the reader as if the tag is reflected by the object. Guarantees accuracy. Therefore, it is possible to measure the distance of the wireless tag with one reader, and the distance measurement accuracy is high.

  Since the internal configuration of the reader 800 according to the present embodiment is the same as that of the reader 500 according to the second embodiment, description thereof is omitted. In reader 800 according to the present embodiment, UWB transmission section 310 transmits a beacon signal in addition to the UW signal. Further, as will be described later, the arrival time estimation unit 520 estimates an internal processing delay of a semi-passive tag 600A described later, and uses the estimated internal processing delay amount for an arrival time estimation result for the semi-passive tag 600A. Execute correction processing.

  FIG. 14 is a block diagram showing an internal configuration of the semi-passive tag according to the fourth embodiment. 14, the same components as those in FIG. 11 are denoted by the same reference numerals, and description thereof is omitted. A semi-passive tag 600A according to the present embodiment in FIG. 14 includes a control unit 640A in place of the control unit 640 with respect to the semi-passive tag 600 in FIG.

  Similarly to the control unit 640, the control unit 640A generates a transmission level control signal for controlling the transmission power of the re-radiation pulse based on the reception power estimation result acquired by the reception power estimation unit 634 of the reception unit 630. To do. The control unit 640A outputs the generated transmission level control signal to the buffer amplifier 651.

  Also in the UWB sensor system using the semi-passive tag 600A configured as described above, as shown in FIG. 12, the semi-passive is between the re-radiation pulse from the semi-passive tag 600A and the reflected pulse from the human body. An arrival time difference corresponding to the internal processing delay amount of the tag 600A occurs. In other words, this arrival time difference indicates the internal processing delay amount of the semi-passive tag 600A. That is, the internal processing delay amount of the semi-passive tag 600A can be estimated using the arrival time of the reflected pulse from the human body.

  Therefore, the arrival time estimation unit 520 of the reader 800 performs correction processing on the arrival time estimation result for the semi-passive tag 600A using the estimated internal processing delay amount. Specifically, the two-dimensional profile estimation unit 370 calculates a two-dimensional power spectrum using a delay time difference between the re-radiated beacon signal and the human body echo reflected by the human body wearing the semi-passive tag 600A. to correct. As will be described later, the distance measurement / biological detection unit 380 measures the distance to the semi-passive tag 600A based on the corrected two-dimensional power spectrum.

  As described above, when the echo-back type semi-passive tag is used, the re-radiation pulse of the semi-passive tag 600A and the reflected pulse from the human body of the wearer of the semi-passive tag 600A are also avoided in the semi-passive tag 600A. The internal processing delay that cannot be corrected can be corrected on the reader side that executes the distance measuring process.

  As described above, in the present embodiment, the semi-passive tag 600A superimposes the tag ID on the beacon signal transmitted from the reader 800 using the IR-UWB pulse sequence, and outputs the beacon signal on which the tag ID is superimposed. Re-radiate. In the reader 800, the two-dimensional profile estimation unit 370 uses the delay time difference between the re-radiated beacon signal and the human body echo reflected by the human body wearing the semi-passive tag 600A. The distance measurement / biological detection unit 380 measures the distance to the semi-passive tag 600A based on the corrected two-dimensional power spectrum. As a result, the reader 800 side can also absorb fluctuations in the amount of internal processing delay of the semi-passive tag 600A caused by temperature changes and the like, and tag distance measurement accuracy can be guaranteed.

  The UWB sensor system and reader device according to the present invention can be obtained by linking the ID, position and biological information of a person with a wireless tag to the reader, and can be used for safety assurance and health management in a dangerous work environment. It is particularly useful. Further, it can be applied to medical uses such as monitoring an apnea state during sleep at home or in a hospital.

100 people 101 fixture 200 tag 220, 650 ID transmission unit 221 UWB pulse generation unit 222, 314 amplifier 300, 500, 700, 800 reader 210, 301, 531-1 to 531-4, 610 antenna 302, 532-1 to 532 -4 RF switch 310 UWB transmission unit 313, 542-1 to 542-4, 653 Band pass filter 312 SRD circuit 311 Transmission pattern generation unit 320 UWB reception unit 321, 541-1 to 541-4, 631 LNA
322 Gain adjustment circuit 323 Detection circuit 324 Signal shaping circuit 325, 544-1 to 544-4 A / D conversion unit 330, 510 Correlation reception unit 340 Tag ID detection unit 350 Mode setting / control unit 360 Common memory 370 Two-dimensional profile estimation Unit 380 distance measurement / biological detection unit 390 sensor information 520 arrival time estimation unit 530 arrival direction estimation unit 540 reception processing unit 543-1 to 543-4 down converter 550 correlation matrix calculation unit 560 arrival direction calculation unit 600, 600A semi-passive tag 620 Circulator 630 Receiver 632 Detector 633 Comparator 634 Received power estimator 640, 640A Controller 651 Buffer amplifier 652 Step recovery diode

Claims (9)

A UWB sensor system comprising a tag device and a reader device,
The tag device is
ID transmission means for burst-transmitting an ID signal indicating the ID of the tag device using an IR-UWB pulse sequence,
The reader device is
UWB transmission means for transmitting a UW signal that is periodic and intermittent using an IR-UWB pulse sequence and that indicates a unique word unique to the reader device;
UWB receiving means for receiving the human body echo reflected by the human body wearing the tag device with the ID signal and the UW signal;
ID detecting means for detecting the ID of the tag device from the ID signal;
Correlation receiving means for calculating a delay profile of the received signal;
Two-dimensional profile estimation means for calculating a two-dimensional power spectrum in the delay time region and the Doppler shift region using the delay profile;
A living body detecting means for detecting the human body echo using the two-dimensional power spectrum,
The UWB transmission means transmits the UW signal after the ID of the tag device is detected.
UWB sensor system. The living body detection means measures a distance to the tag device based on the two-dimensional power spectrum;
The UWB sensor system according to claim 1. When the ID detection unit detects the ID of the tag device, the operation mode is changed from the initial ID detection mode for receiving the ID signal to the radar mode for receiving the human body echo, and the UWB transmission is performed. The means further comprises mode setting / control means for controlling to start transmission of the UWB signal.
The UWB sensor system according to claim 1. The mode setting / control unit generates a control signal for gain adjustment in the UWB reception unit when the operation mode is changed,
The UWB receiving means includes gain control means for adjusting the gain of the received signal according to the operation mode with the control signal as an input.
The UWB sensor system according to claim 3. The correlation receiving unit generates a timing control signal for adjusting a reception timing of a pulse sequence based on the delay profile,
The reader device is
An array antenna for receiving the UW signal;
An RF switch for controlling a reception time window of the array antenna using the timing control signal;
Reception processing means for performing sampling processing by narrowing each reception signal via the RF switch;
Correlation matrix calculation means for calculating a correlation matrix for the array antenna using a sampling signal obtained by the reception processing means;
Direction of arrival estimation means for estimating the direction of the pulse sequence that arrived in the reception time window using the correlation matrix;
The UWB sensor system according to claim 1. The UWB transmission means transmits a beacon signal,
The tag device is
Receiving means for receiving the beacon signal;
Control means for controlling the transmission power of the ID signal based on the reception power of the beacon signal;
The ID transmitting unit superimposes the receiving unit the tag device ID, re-radiates the beacon signal on which the tag device ID is superimposed as the ID signal,
The UWB sensor system according to claim 1. The control means further controls the transmission timing of the ID signal based on the reception timing of the beacon signal.
The UWB sensor system according to claim 6. The two-dimensional profile estimation means corrects the two-dimensional power spectrum using a delay time difference between the re-radiated beacon signal and a human body echo reflected by the human body on which the beacon signal is attached.
The living body detection means measures the distance to the tag device based on the corrected two-dimensional power spectrum;
The UWB sensor system according to claim 6. UWB transmission means for transmitting a UW signal that is periodic and intermittent using an IR-UWB pulse sequence and that indicates a unique word unique to the reader device;
An ID signal indicating an ID of the tag device, and a UWB receiving means for receiving a human body echo reflected from the human body on which the tag device is mounted, the UW signal;
ID detecting means for detecting the ID of the tag device from the ID signal;
Correlation receiving means for calculating a delay profile of the received signal;
Two-dimensional profile estimation means for calculating a two-dimensional power spectrum in the delay time region and the Doppler shift region using the delay profile;
A living body detecting means for detecting the human body echo using the two-dimensional power spectrum,
The UWB transmission means transmits the UW signal after the ID of the tag device is detected.
Reader device.

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