JPWO2007099610A1 - Reader device - Google Patents

Abstract

At the time of carrier sense, the control unit 118 shifts the oscillation frequency of the local signal of the local oscillator 117 by Δf to shift the frequency after the reception frequency conversion of the detection target frequency by Δf to shift the HPFs 109 and 110 and the LPFs 111, 112, the received power is averaged for each carrier sense interval, and the averaged power is compared with the specified power. When the averaged power is larger than the specified power, the communication frequency is set.

Description

  The present invention relates to a reader device, and more particularly to a reader device that reads information from an RF tag.

  In recent years, there are many devices that use wireless communication, and the number of devices that use a narrow frequency band and an adjacent frequency band tends to increase. As a device using such a radio frequency band, for example, there are a device using a wireless LAN, an RFID (Radio Frequency Identification) tag system using an electronic tag incorporating an antenna and an IC chip, and the like.

  Wireless LAN devices and RFID tag systems use, for example, high-frequency radio waves such as UHF (Ultra High Frequency) band and operate in cooperation with similar devices that exist at a short distance with relatively low power. There are many things, and there is a demand for a technology that improves the utilization efficiency of radio waves transmitted and received between devices.

  As such a technique, for example, there is a direct conversion type receiver described in Patent Document 1. This receiver is compatible with a packet radio communication system of a carrier sense multiple access system, and a narrowband lowpass filter is inserted into a received signal converted from a radio frequency to a baseband frequency to detect electric field strength. Performing carrier sense determination from the detection result, and inserting a broadband low-pass filter into the received signal converted to the baseband frequency when the carrier is determined from the determination result, and demodulating it. The reception adjacent channel interference characteristics are improved between a plurality of terminals individually belonging to each cell existing in the vicinity of a plurality of frequency cell boundary regions.

Further, there is a wireless tag system described in Patent Document 2. In this wireless tag system, a wireless tag receives a radio wave transmitted from a mobile phone as a general-purpose radio wave transmission source, and the wireless tag is made operable by using the transmission radio wave as an operating power source, and the reader / writer is made to receive the transmission radio wave. Then, while the transmission radio wave is being received, data is written to the radio tag or data is read from the radio tag so that the operation source of the radio tag can be easily transmitted from a radio wave other than the reader / writer. And it can be secured economically.
JP 2003-347946 A JP 2004-54515 A

  However, although the direct conversion method is used in the conventional receiver of Patent Document 1 and the reader / writer of Patent Document 2, when the carrier sense function is provided in these receivers and reader / writers, the following is performed. There is a problem.

  The wireless tag detects and rectifies the RF signal transmitted from the reader device to generate an electromotive force, and responds to the CW (Carrier Wave) signal shown in FIG. In addition, when sending a command to the wireless tag, the reader device performs ASK (Amplitude Shift Keying) modulation and sends a spectrum signal as shown in FIG.

  In the reader device, since the transmission frequency and the reception frequency are the same, when transmitting a CW signal, the frequency becomes 0 Hz, that is, DC after frequency conversion by the direct conversion method, and this DC component interferes with the reception system. In the reader device, in order to remove this DC component, the DC component is cut by HPF (High-Pass Filter) or DC cut capacitor after frequency conversion.

However, if the reader device is provided with a carrier sense function and attempts to detect signal power other than its own station, if the detection target is a CW signal, the DCF is removed along with the removal of the DC component as shown in FIG. Therefore, there arises a problem that power detection of the CW signal cannot be performed correctly. Also, as shown in FIG. 4, even in the case of a modulated spectrum signal (modulated signal), most of the energy of the spectrum signal is in the vicinity of f ₀ , so that the spectrum signal is cut off together with the removal of the DC component by HPF. The power detection cannot be performed correctly.

  An object of the present invention is to provide a reader device that correctly detects the reception power of a CW signal or a spectrum signal by shifting the oscillation frequency of a local signal within the range of a signal pass band of a filter used in a reception system during carrier sensing. It is to be.

  The reader device of the present invention is a reader device that reads information from a wireless tag by wireless communication, and includes an oscillating unit that oscillates a local signal corresponding to a communication channel setting, and a received signal received from the wireless tag by the local signal. Demodulating means for demodulating, filtering means for filtering the demodulated demodulated signal to extract a predetermined frequency band signal, and setting for the oscillating means at the time of carrier sensing for scanning a communication channel between the wireless tag And a control means for supplying the oscillation means with a control signal for shifting the communication channel within the signal pass band of the filter means.

  According to the present invention, at the time of carrier sensing, the reception power of a CW signal or a spectrum signal can be correctly detected by shifting the oscillation frequency of the local signal within the signal pass band of the filter used in the reception system.

The figure which shows an example of the CW signal sent by the conventional reader apparatus The figure which shows an example of the modulation signal sent by the conventional reader apparatus The figure which shows the example of interruption | blocking of CW signal by HPF in the conventional reader apparatus The figure which shows the example of interruption | blocking of the modulation signal by HPF in the conventional reader apparatus The block diagram which shows the structure of the reader apparatus which concerns on one embodiment of this invention The figure for demonstrating the principle of the operation | movement which shifts the frequency of the local signal which concerns on this Embodiment. The figure which shows the example in which the signal received from another station at the time of the carrier sense which concerns on this Embodiment is a modulation signal The figure which shows the frequency characteristic of HPF and LPF of the receiving system of the reader apparatus which concerns on this Embodiment The figure which shows the setting range of the local signal frequency in the reader apparatus which concerns on this Embodiment The flowchart which shows the carrier sense process performed by the control part in the reader apparatus which concerns on this Embodiment. The figure which shows an example of the channel arrangement | positioning at the time of the carrier sense which concerns on this Embodiment The figure which shows the specific example of the channel scan operation | movement in the carrier sense process which concerns on this Embodiment The figure which shows the received power of each channel at the time of the carrier sense which concerns on this Embodiment The figure which shows the transmission operation state which concerns on this Embodiment The figure which shows the example which divides | segments an electric power detection area at the time of the carrier sense which concerns on this Embodiment The figure which shows the transmission operation state which concerns on this Embodiment

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

  FIG. 5 is a block diagram showing a configuration of a reader device according to an embodiment to which the present invention is applied.

  In FIG. 5, a reader apparatus 100 includes an antenna 101, a coupler 102, an LPF 103, a mixer 104, an amplifier 105, and a BPF (Band Pass Filter) 106, a transmission system 100A, a BPF 107, an orthogonal demodulation unit 108, and an HPF 109. 110, LPF (Low Pass Filter) 111, 112, amplifiers 113, 114, and A / D converters 115, 116, a local oscillator 117, and a control unit 118.

  The reader apparatus 100 of the present embodiment has a direct conversion communication function by the configuration of the transmission system 100A and the reception system 100B.

  The antenna 101 wirelessly transmits the CW signal and the modulation signal transmitted from the coupler 102 to the wireless tag 200 and outputs a reception signal received from the wireless tag 200 to the coupler 102.

  The coupler 102 performs impedance matching with the antenna 101 connected to the antenna connection terminal 120, transmits a transmission signal input from the transmission system 100A from the antenna 101, and receives a reception signal received from the antenna 101 as the reception system. Output to 100B.

  The LPF 103 of the transmission system 100 </ b> A removes the high frequency noise component of the transmission data input from the control unit 118 and outputs it to the mixer 104.

  The mixer 104 modulates the transmission data input from the LPF 103 with the local signal input from the local oscillator 117, and outputs the modulated signal to the amplifier 105.

  The amplifier 105 amplifies the modulation signal input from the mixer 104 and outputs the amplified signal to the BPF 106. The BPF 106 extracts a signal in a necessary frequency band from the modulation signal input from the amplifier 105 and outputs the signal to the coupler 102.

  The BPF 107 of the reception system 100B extracts a signal of a necessary frequency band from the reception signal input from the coupler 102 and outputs the signal to the quadrature demodulation unit 108.

  The quadrature demodulator 108 includes a phase shifter 108a and mixers 108b and 108c. The phase shifter 108a shifts the phase of the local signal input from the local oscillator 117 by 0 ° to 90 °, supplies the local signal of 0 ° to the mixer 108b, and supplies the local signal of 90 ° to the mixer 108c. To do. The mixer 108 b demodulates the received signal input from the BPF 107 into a baseband signal using the 0 ° local signal input from the phase shifter 108 a, and outputs the demodulated I (real part) signal to the HPF 109. The mixer 108 c demodulates the received signal input from the BPF 107 into a baseband signal using the 90 ° local signal input from the phase shifter 108 a, and outputs the demodulated Q (imaginary part) signal to the HPF 110.

  The HPF 109 and the LPF 111 extract a signal in a necessary frequency band from the I signal input from the quadrature demodulation unit 108 and output the signal to the amplifier 113. The HPF 110 and the LPF 112 extract a signal in a necessary frequency band from the Q signal input from the quadrature demodulation unit 108 and output the signal to the amplifier 114.

  The amplifier 113 amplifies the I signal input from the LPF 111 and outputs it to the A / D converter 115. The amplifier 114 amplifies the I signal input from the LPF 112 and outputs it to the A / D converter 116.

  The A / D converter 115 A / D converts the I signal input from the amplifier 113 and outputs the converted digital signal to the control unit 118. The A / D converter 116 A / D-converts the Q signal input from the amplifier 114 and outputs the converted digital signal to the control unit 118.

  The local oscillator 117 includes a PLL (Phase Locked Loop) circuit 117a and a VCO (Voltage Controlled Oscillator) 117b.

  The PLL circuit 117a outputs an oscillation frequency control signal (voltage signal) to the VCO 117b, and a shift control signal (voltage signal) for shifting the frequency of the local signal oscillated from the VCO 117b by the local shift control signal input from the control unit 118. ) Is output to the VCO 117b.

  The VCO 117b determines the oscillation frequency based on the oscillation frequency control signal (voltage signal) input to the PLL circuit 117a, supplies the local signal to the mixer 104 and the phase shifter 108a, and shift control signal (input to the PLL circuit 117a). The oscillation frequency of the local signal is shifted by the voltage signal.

  The control unit 118 generates transmission data to be transmitted to the transmission system 100A during normal data communication, and outputs data from digital signals respectively input from the A / D converters 115 and 116 of the reception system 100B. A data processing function to be extracted and a local oscillation control function for supplying a local shift control signal for shifting the oscillation frequency of the local signal to the local oscillator 117 at the time of carrier sensing.

  In FIG. 5, the wireless tag 200 includes an antenna 201 and a tag main body 202 including a communication unit that performs communication with the reader device 100 and a nonvolatile memory that stores data.

As a basic operation during normal data communication and carrier sense, the reader device 100 first transmits the CW signal for power supply to the wireless tag 200, and is transmitted from the wireless tag 200 by this power supply. A response signal including data to be received is received. Upon reception of this signal, the frequency of the transmit and receive signals are both frequency is the same as f _0.

  For this reason, in the reader device 100, as shown in FIG. 1, at the time of signal transmission, a part of the transmission signal TX wraps around the reception system via the coupler 102, and the transmission signal TX due to mismatch with the antenna 101 or the like. The reflected wave leaks to and interferes with the receiving system via the coupler 102, and there is a risk of degrading sensitivity when receiving the tag signal. In particular, when the transmission signal is a CW signal, it is necessary to be able to receive the tag signal at the same time. Therefore, HPFs 109 and 110 are inserted into the outputs of the mixers 108b and 108c, and the DC component of the CW transmission signal of the own station is obtained. This prevents the amplifiers 113 and 114 and the A / D converters 115 and 116 from being suppressed.

  However, when trying to receive a CW signal other than the own station in the carrier sense function, there is a problem that the DC component is cut by the HPFs 109 and 110 and the power detection of the CW signal cannot be performed correctly.

  Therefore, the reader device 100 according to the present embodiment is characterized in that the control unit 118 controls the local oscillator 108 so as to shift the frequency of the local signal within the frequency band of the HPF and LPF during carrier sense. .

  The operation at the time of carrier sensing in the control unit 118 of the reader apparatus 100 will be described below with reference to the drawings.

FIG. 6 is a diagram for explaining the principle of the operation of shifting the frequency of the local signal. At the time of carrier sense, by shifting the oscillation frequency of the local signal by Δf, the frequency after the reception frequency conversion of the detection target frequency is shifted by Δf to be within the signal pass band of the HPFs 109 and 110 and the LPFs 111 and 112 of the receiving system 100B. This received power is measured for each carrier sense interval. In the quadrature demodulator 108 that is a reception frequency converter, the reception power is calculated by sqrt ( ^I∧2 + ^Q∧2 ).

  In the example of FIG. 6, the operation of detecting the CW signal power of the other station by shifting the frequency of the local signal by −50 kHz with respect to the channel width of 200 kHz is shown. In this case, the interference to the reception system 100B due to the leak of the transmission signal of the local station becomes 0 Hz (DC) because the frequency of the transmission signal and the frequency of the reception local signal are completely equal, and can be removed by the HPFs 109 and 110.

  Next, FIG. 7 shows an example in which a signal received from another station at the time of carrier sense is a modulated signal. In this example, most of the modulated wave power can be detected with a shift of 100 kHz, but there are portions outside the bands of the HPFs 109 and 110 and LPFs 111 and 112 of the receiving system 100B, and the received power cannot be received accurately. In this case, by narrowing the shift width of the oscillation frequency of the local signal and treating the maximum power detected during the shift as the power of the corresponding channel, accurate power detection is possible even for modulated waves with a wide frequency band. It becomes.

  Next, the frequency setting of the local signal at the time of carrier sense will be described with reference to FIGS.

  FIG. 8 shows the characteristics of the HPFs 109 and 110 and the LPFs 111 and 112 in the receiving system 100B of FIG. In FIG. 8, f_hp is the high cut frequency of the HPFs 109 and 110, f_lp is the low cut frequency of the LPFs 111 and 112, and the range of these f_hp to f_lp is the passband of the baseband filter that processes the received signal.

As shown in FIG. 1, the frequency of the local signal at the time of communication with the wireless tag 200 is set to f _0, and the frequency setting range of the local signal at the time of carrier sense is the HPF 109, 110 and the LPF 111, 112 of FIG. Within the range of the signal pass band, that is, as shown in FIG. 9, f ₀ −f_lp to f ₀ −f_hp or f ₀ + f_lp to f ₀ + f_hp.

  As a result, in the receiving system 100B, the frequency of the signal output from the mixers 108b and 108c is in the range of f_lp to f_hp and is the passband of the baseband filter of FIG. Is possible.

  Next, the control operation in the control unit 118 will be described with reference to the flowchart shown in FIG.

10, when the carrier sense mode is started, the control unit 118 of the reader device 100 generates a transmission command (step S101), and sets a channel (frequency) for transmitting the generated transmission command (step S102). At this time, the channel is set by the following equation (1). FIG. 11 shows an example of channel arrangement.
fch = fch_1 + k × ch_step (1)
k: 0 to n-1 (n is the number of settable channels)
ch_step: Frequency shift width

  Next, the control unit 118 sets the offset setting fcs of the frequency of the local signal based on the channel setting in step S102 by “fcs = fch−Δf or fcs = fch + Δf” (step S103). A corresponding local shift control signal is supplied to the local oscillator 117.

  At this time, the local oscillator 117 oscillates a local signal of “fcs = fch−Δf or fcs = fch + Δf” by the supplied local shift control signal.

  Next, the control unit 118 performs lock wait processing for the supplied local shift control signal until the PLL circuit 117a in the local oscillator 117 is stabilized at a desired frequency (step S104). Then, when a signal transmitted from a station other than its own station is received by the receiving system 100B and ADC data (I, Q data) is taken in by the A / D converters 115 and 116 (step S105), the control unit 118 The power is averaged over the carrier sense interval t (ms) (step S106), and the averaged power Pt is compared with a preset specified power Ps to determine whether the averaged power Pt is greater than the specified power Ps. (Step S107).

  When determining that the averaged power Ps is smaller than the specified power Pt (step S107: YES), the control unit 118 sets the frequency corresponding to the channel setting set in step S102 in the local oscillator 117 (step S108). Then, transmission processing for the wireless tag 200 is started (step S109), and this processing is terminated.

  In addition, when determining that the average power Ps is greater than or equal to the specified power Pt (step S107: NO), the control unit 118 determines whether or not the channel setting fch set in step S102 is greater than or equal to the number n of channels that can be set. (Step S110).

  If the channel setting fch is less than the number n of channels that can be set (step S110: NO), the control unit 118 returns to step S102, performs the next channel setting, and repeatedly executes the processing from step S103 to step S107. To do.

  If the channel setting fch is equal to or greater than the number of channels n that can be set (step S110: YES), the control unit 118 determines that transmission is not possible (step S111) and ends this processing.

  A specific example of the channel scan operation in the above carrier sense processing will be described with reference to FIG.

  In this case, the received power of each of the channels ch_1, ch_2,..., Ch_k is measured, and when the received power of the other station is less than or equal to the specified power Ps in each carrier sense section t (ms), the oscillation frequency of the local signal is set. Confirm the available channels by changing and repeating the channel scan. In the channel scan, when measuring the power after changing the channel setting, the wait period (the lock weight) is set until the frequency of the PLL circuit 117a is stabilized.

  FIG. 13 shows another operation example. In FIG. 13, (A) is a diagram showing received power of each channel at the time of carrier sense, and (B) is a diagram showing a transmission operation state. In the carrier sense example shown in FIG. 13A, the received power Ps of other stations in the channels ch_1 and ch_2 is equal to or higher than the specified power Pt (Pt ≦ Ps), and the reader apparatus 100 that is the own station in FIG. Cannot be transmitted (TX OFF), but in channel ch_3 in FIG. 8A, the received power Ps of the other station is smaller than the prescribed power Pt (Pt> Ps), so in FIG. Can be transmitted (TX ON).

  Next, the operation when dividing the power detection section of each channel into a plurality will be described with reference to FIG. 14A is a diagram showing a reception power detection section of each channel at the time of carrier sense, and FIG. 14B is a diagram showing a transmission operation state.

  As shown in FIG. 14B, when the received power detection section of each channel is divided into a plurality of times at the time of carrier sensing, when the power detection exceeds the specified power Pt before the power detection of all sections of each channel is completed. By controlling the control unit 118 to immediately shift to power detection for the next channel, it is possible to increase the speed of the carrier sense operation.

  As described above, according to the reader device of the present embodiment, the device configuration is changed or added by controlling the oscillation frequency of the local signal to be shifted within the frequency band of HPF and LPF during carrier sensing. In addition, the received power of the CW signal or spectrum signal can be measured correctly.

  A first aspect of the reader device of the present invention is a reader device that reads information from a wireless tag by wireless communication, and includes an oscillating means that oscillates a local signal according to a communication channel setting, and a received signal received from the wireless tag. At the time of carrier sensing for scanning a communication channel between the wireless tag and a demodulating means for demodulating the local demodulated signal, a filter means for filtering the demodulated demodulated signal to extract a predetermined frequency band signal, And a control means for supplying the oscillation means with a control signal for shifting a communication channel set in the oscillation means within a signal pass band of the filter means.

  According to this configuration, at the time of carrier sensing, the reception power of the CW signal or spectrum signal can be detected correctly by shifting the oscillation frequency of the local signal within the signal pass band of the filter used in the reception system.

  According to a second aspect of the reader apparatus of the present invention, in the reader apparatus according to the first aspect, the control unit detects the reception power of the frequency band signal for each carrier sense section, and average power in the carrier sense section A configuration is adopted in which the setting of the communication channel is changed based on the result of comparing the value and the specified power value.

  According to this configuration, it is possible to reliably detect a communication channel used in another station without changing or adding the configuration of the reader device.

  According to a third aspect of the reader apparatus of the present invention, in the reader apparatus according to the second aspect, when the average power value is smaller than the specified power value, the control unit changes the setting of the communication channel, When the average power value is larger than the specified power value, the communication frequency corresponding to the current communication channel setting is set in the oscillation means.

  According to this configuration, communication can be started according to the communication channel used in another station without changing or adding the configuration of the reader device.

  According to a fourth aspect of the reader apparatus of the present invention, in the reader apparatus according to the third aspect, the control unit divides the carrier sense section into a plurality of parts, and before the power detection ends in the divided whole period, A configuration is adopted in which the setting of the communication channel is changed when the average power value is equal to or greater than the specified power value.

  According to this configuration, it is possible to increase the speed of the carrier sense operation.

  The present invention makes it possible to correctly detect the reception power of a CW signal or a spectrum signal by shifting the oscillation frequency of a local signal within the range of the signal pass band of a filter used in the reception system during carrier sensing. It is useful for wireless tag systems.

  The present invention relates to a reader device, and more particularly to a reader device that reads information from an RF tag.

  In recent years, there are many devices that use wireless communication, and the number of devices that use a narrow frequency band and an adjacent frequency band tends to increase. As a device using such a radio frequency band, for example, there are a device using a wireless LAN, an RFID (Radio Frequency Identification) tag system using an electronic tag incorporating an antenna and an IC chip, and the like.

  Wireless LAN devices and RFID tag systems use, for example, high-frequency radio waves such as UHF (Ultra High Frequency) band and operate in cooperation with similar devices that exist at a short distance with relatively low power. There are many things, and there is a demand for a technology that improves the utilization efficiency of radio waves transmitted and received between devices.

  As such a technique, for example, there is a direct conversion type receiver described in Patent Document 1. This receiver is compatible with a packet radio communication system of a carrier sense multiple access system, and a narrowband lowpass filter is inserted into a received signal converted from a radio frequency to a baseband frequency to detect electric field strength. Performing carrier sense determination from the detection result, and inserting a broadband low-pass filter into the received signal converted to the baseband frequency when the carrier is determined from the determination result, and demodulating it. The reception adjacent channel interference characteristics are improved between a plurality of terminals individually belonging to each cell existing in the vicinity of a plurality of frequency cell boundary regions.

Further, there is a wireless tag system described in Patent Document 2. In this wireless tag system, a wireless tag receives a radio wave transmitted from a mobile phone as a general-purpose radio wave transmission source, and the wireless tag is made operable by using the transmission radio wave as an operating power source, and the reader / writer is made to receive the transmission radio wave. Then, while the transmission radio wave is being received, data is written to the radio tag or data is read from the radio tag so that the operation source of the radio tag can be easily transmitted from a radio wave other than the reader / writer. And it can be secured economically.
JP 2003-347946 A JP 2004-54515 A

  However, although the direct conversion method is used in the conventional receiver of Patent Document 1 and the reader / writer of Patent Document 2, when the carrier sense function is provided in these receivers and reader / writers, the following is performed. There is a problem.

  The wireless tag detects and rectifies the RF signal transmitted from the reader device to generate an electromotive force, and responds to the CW (Carrier Wave) signal shown in FIG. In addition, when sending a command to the wireless tag, the reader device performs ASK (Amplitude Shift Keying) modulation and sends a spectrum signal as shown in FIG.

  In the reader device, since the transmission frequency and the reception frequency are the same, when transmitting a CW signal, the frequency becomes 0 Hz, that is, DC after frequency conversion by the direct conversion method, and this DC component interferes with the reception system. In the reader device, in order to remove this DC component, the DC component is cut by HPF (High-Pass Filter) or DC cut capacitor after frequency conversion.

However, if the reader device is provided with a carrier sense function and attempts to detect signal power other than its own station, if the detection target is a CW signal, the DCF is removed along with the removal of the DC component as shown in FIG. Therefore, there arises a problem that power detection of the CW signal cannot be performed correctly. Also, as shown in FIG. 4, even in the case of a modulated spectrum signal (modulated signal), most of the energy of the spectrum signal is in the vicinity of f ₀ , so that the spectrum signal is cut off together with the removal of the DC component by HPF. The power detection cannot be performed correctly.

  An object of the present invention is to provide a reader device that correctly detects the reception power of a CW signal or a spectrum signal by shifting the oscillation frequency of a local signal within the range of a signal pass band of a filter used in a reception system during carrier sensing. It is to be.

  The reader device of the present invention is a reader device that reads information from a wireless tag by wireless communication, and includes an oscillating unit that oscillates a local signal corresponding to a communication channel setting, and a received signal received from the wireless tag by the local signal. Demodulating means for demodulating, filtering means for filtering the demodulated demodulated signal to extract a predetermined frequency band signal, and setting for the oscillating means at the time of carrier sensing for scanning a communication channel between the wireless tag And a control means for supplying the oscillation means with a control signal for shifting the communication channel within the signal pass band of the filter means.

  According to the present invention, at the time of carrier sensing, the reception power of a CW signal or a spectrum signal can be correctly detected by shifting the oscillation frequency of the local signal within the signal pass band of the filter used in the reception system.

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

  FIG. 5 is a block diagram showing a configuration of a reader device according to an embodiment to which the present invention is applied.

  In FIG. 5, a reader apparatus 100 includes an antenna 101, a coupler 102, an LPF 103, a mixer 104, an amplifier 105, and a BPF (Band Pass Filter) 106, a transmission system 100A, a BPF 107, an orthogonal demodulation unit 108, and an HPF 109. 110, LPF (Low Pass Filter) 111, 112, amplifiers 113, 114, and A / D converters 115, 116, a local oscillator 117, and a control unit 118.

  The reader apparatus 100 of the present embodiment has a direct conversion communication function by the configuration of the transmission system 100A and the reception system 100B.

  The antenna 101 wirelessly transmits the CW signal and the modulation signal transmitted from the coupler 102 to the wireless tag 200 and outputs a reception signal received from the wireless tag 200 to the coupler 102.

  The coupler 102 performs impedance matching with the antenna 101 connected to the antenna connection terminal 120, transmits a transmission signal input from the transmission system 100A from the antenna 101, and receives a reception signal received from the antenna 101 as the reception system. Output to 100B.

  The LPF 103 of the transmission system 100 </ b> A removes the high frequency noise component of the transmission data input from the control unit 118 and outputs it to the mixer 104.

  The mixer 104 modulates the transmission data input from the LPF 103 with the local signal input from the local oscillator 117, and outputs the modulated signal to the amplifier 105.

  The amplifier 105 amplifies the modulation signal input from the mixer 104 and outputs the amplified signal to the BPF 106. The BPF 106 extracts a signal in a necessary frequency band from the modulation signal input from the amplifier 105 and outputs the signal to the coupler 102.

  The BPF 107 of the reception system 100B extracts a signal of a necessary frequency band from the reception signal input from the coupler 102 and outputs the signal to the quadrature demodulation unit 108.

  The quadrature demodulator 108 includes a phase shifter 108a and mixers 108b and 108c. The phase shifter 108a shifts the phase of the local signal input from the local oscillator 117 by 0 ° to 90 °, supplies the local signal of 0 ° to the mixer 108b, and supplies the local signal of 90 ° to the mixer 108c. To do. The mixer 108 b demodulates the received signal input from the BPF 107 into a baseband signal using the 0 ° local signal input from the phase shifter 108 a, and outputs the demodulated I (real part) signal to the HPF 109. The mixer 108 c demodulates the received signal input from the BPF 107 into a baseband signal using the 90 ° local signal input from the phase shifter 108 a, and outputs the demodulated Q (imaginary part) signal to the HPF 110.

  The HPF 109 and the LPF 111 extract a signal in a necessary frequency band from the I signal input from the quadrature demodulation unit 108 and output the signal to the amplifier 113. The HPF 110 and the LPF 112 extract a signal in a necessary frequency band from the Q signal input from the quadrature demodulation unit 108 and output the signal to the amplifier 114.

  The amplifier 113 amplifies the I signal input from the LPF 111 and outputs it to the A / D converter 115. The amplifier 114 amplifies the I signal input from the LPF 112 and outputs it to the A / D converter 116.

  The A / D converter 115 A / D converts the I signal input from the amplifier 113 and outputs the converted digital signal to the control unit 118. The A / D converter 116 A / D-converts the Q signal input from the amplifier 114 and outputs the converted digital signal to the control unit 118.

  The local oscillator 117 includes a PLL (Phase Locked Loop) circuit 117a and a VCO (Voltage Controlled Oscillator) 117b.

  The PLL circuit 117a outputs an oscillation frequency control signal (voltage signal) to the VCO 117b, and shifts a frequency of the local signal oscillated from the VCO 117b by the local shift control signal input from the control unit 118 (voltage signal). ) Is output to the VCO 117b.

  The VCO 117b determines the oscillation frequency based on the oscillation frequency control signal (voltage signal) input to the PLL circuit 117a, supplies the local signal to the mixer 104 and the phase shifter 108a, and shift control signal (input to the PLL circuit 117a). The oscillation frequency of the local signal is shifted by the voltage signal.

  The control unit 118 generates transmission data to be transmitted to the transmission system 100A during normal data communication, and outputs data from digital signals respectively input from the A / D converters 115 and 116 of the reception system 100B. A data processing function to be extracted and a local oscillation control function for supplying a local shift control signal for shifting the oscillation frequency of the local signal to the local oscillator 117 at the time of carrier sensing.

  In FIG. 5, the wireless tag 200 includes an antenna 201 and a tag main body 202 including a communication unit that performs communication with the reader device 100 and a nonvolatile memory that stores data.

As a basic operation during normal data communication and carrier sense, the reader device 100 first transmits the CW signal for power supply to the wireless tag 200, and is transmitted from the wireless tag 200 by this power supply. A response signal including data to be received is received. In transmission and reception of this signal, the frequency of the transmit and receive signals are both frequency is the same as f _0.

  For this reason, in the reader device 100, as shown in FIG. 1, at the time of signal transmission, a part of the transmission signal TX wraps around the reception system via the coupler 102, and the transmission signal TX due to mismatch with the antenna 101 or the like. The reflected wave leaks to and interferes with the receiving system via the coupler 102, and there is a risk of degrading sensitivity when receiving the tag signal. In particular, when the transmission signal is a CW signal, it is necessary to be able to receive the tag signal at the same time. Therefore, HPFs 109 and 110 are inserted into the outputs of the mixers 108b and 108c, and the DC component of the CW transmission signal of the own station is obtained. This prevents the amplifiers 113 and 114 and the A / D converters 115 and 116 from being suppressed.

  However, when trying to receive a CW signal other than the own station in the carrier sense function, there is a problem that the DC component is cut by the HPFs 109 and 110 and the power detection of the CW signal cannot be performed correctly.

  Therefore, the reader device 100 according to the present embodiment is characterized in that the control unit 118 controls the local oscillator 108 so as to shift the frequency of the local signal within the frequency band of the HPF and LPF during carrier sense. .

  The operation at the time of carrier sensing in the control unit 118 of the reader apparatus 100 will be described below with reference to the drawings.

FIG. 6 is a diagram for explaining the principle of the operation of shifting the frequency of the local signal. At the time of carrier sense, by shifting the oscillation frequency of the local signal by Δf, the frequency after the reception frequency conversion of the detection target frequency is shifted by Δf to be within the signal pass band of the HPFs 109 and 110 and the LPFs 111 and 112 of the receiving system 100B. This received power is measured for each carrier sense interval. In the quadrature demodulator 108 that is a reception frequency converter, the reception power is calculated by sqrt ( ^I∧2 + ^Q∧2 ).

  In the example of FIG. 6, the operation of detecting the CW signal power of the other station by shifting the frequency of the local signal by −50 kHz with respect to the channel width of 200 kHz is shown. In this case, the interference to the reception system 100B due to the leak of the transmission signal of the local station becomes 0 Hz (DC) because the frequency of the transmission signal and the frequency of the reception local signal are completely equal, and can be removed by the HPFs 109 and 110.

  Next, FIG. 7 shows an example in which a signal received from another station at the time of carrier sense is a modulated signal. In this example, most of the modulated wave power can be detected with a shift of 100 kHz, but there are portions outside the bands of the HPFs 109 and 110 and LPFs 111 and 112 of the receiving system 100B, and the received power cannot be received accurately. In this case, by narrowing the shift width of the oscillation frequency of the local signal and treating the maximum power detected during the shift as the power of the corresponding channel, accurate power detection is possible even for modulated waves with a wide frequency band. It becomes.

  Next, the frequency setting of the local signal at the time of carrier sense will be described with reference to FIGS.

  FIG. 8 shows the characteristics of the HPFs 109 and 110 and the LPFs 111 and 112 in the receiving system 100B of FIG. In FIG. 8, f_hp is the high cut frequency of the HPFs 109 and 110, f_lp is the low cut frequency of the LPFs 111 and 112, and the range of these f_hp to f_lp is the passband of the baseband filter that processes the received signal.

As shown in FIG. 1, the frequency of the local signal at the time of communication with the wireless tag 200 is set to f _0, and the frequency setting range of the local signal at the time of carrier sense is the HPF 109, 110 and the LPF 111, 112 of FIG. within the signal passband, that is, as shown in FIG. _9, the f ₀ -f_lp ~f 0 -f_hp or _{f 0} + _{f_lp~f} 0 + _{f_hp.}

  As a result, in the receiving system 100B, the frequency of the signal output from the mixers 108b and 108c is in the range of f_lp to f_hp and is the passband of the baseband filter of FIG. Is possible.

  Next, the control operation in the control unit 118 will be described with reference to the flowchart shown in FIG.

10, when the carrier sense mode is started, the control unit 118 of the reader device 100 generates a transmission command (step S101), and sets a channel (frequency) for transmitting the generated transmission command (step S102). At this time, the channel is set by the following equation (1). FIG. 11 shows an example of channel arrangement.
fch = fch_1 + k × ch_step (1)
k: 0 to n-1 (n is the number of settable channels)
ch_step: Frequency shift width

  Next, the control unit 118 sets the offset setting fcs of the frequency of the local signal based on the channel setting in step S102 by “fcs = fch−Δf or fcs = fch + Δf” (step S103). A corresponding local shift control signal is supplied to the local oscillator 117.

  At this time, the local oscillator 117 oscillates a local signal of “fcs = fch−Δf or fcs = fch + Δf” by the supplied local shift control signal.

  Next, the control unit 118 performs lock wait processing for the supplied local shift control signal until the PLL circuit 117a in the local oscillator 117 is stabilized at a desired frequency (step S104). Then, when a signal transmitted from a station other than its own station is received by the receiving system 100B and ADC data (I, Q data) is taken in by the A / D converters 115 and 116 (step S105), the control unit 118 The power is averaged over the carrier sense interval t (ms) (step S106), and the averaged power Pt is compared with a preset specified power Ps to determine whether the averaged power Pt is greater than the specified power Ps. (Step S107).

  When determining that the averaged power Ps is smaller than the specified power Pt (step S107: YES), the control unit 118 sets the frequency corresponding to the channel setting set in step S102 in the local oscillator 117 (step S108). Then, transmission processing for the wireless tag 200 is started (step S109), and this processing is terminated.

  In addition, when determining that the average power Ps is greater than or equal to the specified power Pt (step S107: NO), the control unit 118 determines whether or not the channel setting fch set in step S102 is greater than or equal to the number n of channels that can be set. (Step S110).

  If the channel setting fch is less than the number n of channels that can be set (step S110: NO), the control unit 118 returns to step S102, performs the next channel setting, and repeatedly executes the processing from step S103 to step S107. To do.

  If the channel setting fch is equal to or greater than the number of channels n that can be set (step S110: YES), the control unit 118 determines that transmission is not possible (step S111) and ends this processing.

  A specific example of the channel scan operation in the above carrier sense processing will be described with reference to FIG.

  In this case, the received power of each of the channels ch_1, ch_2,..., Ch_k is measured, and when the received power of the other station is less than or equal to the specified power Ps in each carrier sense section t (ms), the oscillation frequency of the local signal is set. Confirm the available channels by changing and repeating the channel scan. In the channel scan, when measuring the power after changing the channel setting, the wait period (the lock weight) is set until the frequency of the PLL circuit 117a is stabilized.

  FIG. 13 shows another operation example. In FIG. 13, (A) shows the received power of each channel at the time of carrier sense, and (B) shows the transmission operation state. In the carrier sense example shown in FIG. 13A, the received power Ps of other stations in the channels ch_1 and ch_2 is equal to or higher than the specified power Pt (Pt ≦ Ps), and the reader apparatus 100 that is the own station in FIG. Cannot be transmitted (TX OFF), but in channel ch_3 in FIG. 6A, the received power Ps of the other station is smaller than the prescribed power Pt (Pt> Ps), so in FIG. Can be transmitted (TX ON).

  Next, the operation when dividing the power detection section of each channel into a plurality will be described with reference to FIG. 14A is a diagram showing a reception power detection section of each channel at the time of carrier sense, and FIG. 14B is a diagram showing a transmission operation state.

  As shown in FIG. 14B, when the received power detection section of each channel is divided into a plurality of times at the time of carrier sensing, when the power detection exceeds the specified power Pt before the power detection of all sections of each channel is completed. By controlling the control unit 118 to immediately shift to power detection for the next channel, it is possible to increase the speed of the carrier sense operation.

  As described above, according to the reader device of the present embodiment, the device configuration is changed or added by controlling the oscillation frequency of the local signal to be shifted within the frequency band of HPF and LPF during carrier sensing. In addition, the received power of the CW signal or spectrum signal can be measured correctly.

  A first aspect of the reader device of the present invention is a reader device that reads information from a wireless tag by wireless communication, and includes an oscillating means that oscillates a local signal according to a communication channel setting, and a received signal received from the wireless tag. At the time of carrier sensing for scanning a communication channel between the wireless tag and a demodulating means for demodulating the local demodulated signal, a filter means for filtering the demodulated demodulated signal to extract a predetermined frequency band signal, And a control means for supplying the oscillation means with a control signal for shifting a communication channel set in the oscillation means within a signal pass band of the filter means.

  According to this configuration, at the time of carrier sensing, the reception power of the CW signal or spectrum signal can be detected correctly by shifting the oscillation frequency of the local signal within the signal pass band of the filter used in the reception system.

  According to a second aspect of the reader apparatus of the present invention, in the reader apparatus according to the first aspect, the control unit detects the reception power of the frequency band signal for each carrier sense section, and average power in the carrier sense section A configuration is adopted in which the setting of the communication channel is changed based on the result of comparing the value and the specified power value.

  According to this configuration, it is possible to reliably detect a communication channel used in another station without changing or adding the configuration of the reader device.

  According to a third aspect of the reader apparatus of the present invention, in the reader apparatus according to the second aspect, when the average power value is smaller than the specified power value, the control unit changes the setting of the communication channel, When the average power value is larger than the specified power value, the communication frequency corresponding to the current communication channel setting is set in the oscillation means.

  According to this configuration, communication can be started according to the communication channel used in another station without changing or adding the configuration of the reader device.

  According to a fourth aspect of the reader apparatus of the present invention, in the reader apparatus according to the third aspect, the control unit divides the carrier sense section into a plurality of parts, and before the power detection ends in the divided whole period, A configuration is adopted in which the setting of the communication channel is changed when the average power value is equal to or greater than the specified power value.

  According to this configuration, it is possible to increase the speed of the carrier sense operation.

  The present invention makes it possible to correctly detect the reception power of a CW signal or a spectrum signal by shifting the oscillation frequency of a local signal within the range of the signal pass band of a filter used in the reception system during carrier sensing. It is useful for wireless tag systems.

The figure which shows an example of the CW signal sent by the conventional reader apparatus The figure which shows an example of the modulation signal sent by the conventional reader apparatus The figure which shows the example of interruption | blocking of CW signal by HPF in the conventional reader apparatus The figure which shows the example of interruption | blocking of the modulation signal by HPF in the conventional reader apparatus The block diagram which shows the structure of the reader apparatus which concerns on one embodiment of this invention The figure for demonstrating the principle of the operation | movement which shifts the frequency of the local signal which concerns on this Embodiment. The figure which shows the example in which the signal received from another station at the time of the carrier sense which concerns on this Embodiment is a modulation signal The figure which shows the frequency characteristic of HPF and LPF of the receiving system of the reader apparatus which concerns on this Embodiment The figure which shows the setting range of the local signal frequency in the reader apparatus which concerns on this Embodiment The flowchart which shows the carrier sense process performed by the control part in the reader apparatus which concerns on this Embodiment. The figure which shows an example of the channel arrangement | positioning at the time of the carrier sense which concerns on this Embodiment The figure which shows the specific example of the channel scan operation | movement in the carrier sense process which concerns on this Embodiment The figure which shows the received power of each channel at the time of the carrier sense which concerns on this Embodiment The figure which shows the transmission operation state which concerns on this Embodiment The figure which shows the example which divides | segments an electric power detection area at the time of the carrier sense which concerns on this Embodiment The figure which shows the transmission operation state which concerns on this Embodiment

Claims (4)

A reader device that reads information from a wireless tag by wireless communication,
An oscillating means for oscillating a local signal according to the communication channel setting;
Demodulation means for demodulating a received signal received from the wireless tag with the local signal;
Filter means for filtering the demodulated demodulated signal to extract a predetermined frequency band signal;
Control means for supplying a control signal to the oscillating means for shifting the communication channel set in the oscillating means within the signal pass band of the filter means at the time of carrier sense for scanning the communication channel with the wireless tag; A reader device provided.   The control means detects the reception power of the frequency band signal for each carrier sense interval, and changes the setting of the communication channel based on a result of comparing an average power value and a specified power value in the carrier sense interval. The reader device according to claim 1.   The control means changes the setting of the communication channel when the average power value is smaller than the specified power value, and corresponds to the current communication channel setting when the average power value is larger than the specified power value. The reader device according to claim 2, wherein a communication frequency is set in the oscillating means. The control unit divides the carrier sense section into a plurality for each communication channel, and when the average power value is equal to or higher than the specified power value before the power detection is completed in all the divided periods, 4. The reader device according to claim 3, wherein the communication channel setting is changed.

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