JP2010020381A - Rfid reader device - Google Patents

Abstract

The present invention relates to an RFID reader device that transmits an inquiry signal to an RFID tag and reads a response signal from the RFID tag, and aims to suppress power consumption while maintaining communication quality with the RFID tag.
An RFID reader device includes a power amplifying unit for amplifying the power of an inquiry signal, a power amplifying unit with a modulation period for modulating and transmitting a carrier wave with a data signal, and a non-modulating period for transmitting the carrier wave without modulation. A bias control circuit 74 for switching the operation region of 72. The bias control circuit 74 sets the operation region in the linear amplification region of the power amplification unit 72 during the modulation period, and nonlinear amplification of the power amplification unit 72 during the non-modulation period. Set the operation area to the area.
[Selection] Figure 5

Description

  The present invention relates to an RFID reader device that transmits an inquiry signal to an RFID tag and reads a response signal from the RFID tag.

  In recent years, RFID (Radio Frequency IDentification) tags have been used in order to improve the management of logistics and goods. For example, it has been used for product management at distribution factories and shipping warehouses and for distribution by delivery destination. In this application, an RFID tag storing tag information such as a product number and a destination is attached to the article, and the article is conveyed by a conveyor or the like. An RFID reader device is provided in the middle of conveying the conveyor, and the RFID reader device reads tag information of the RFID tag to manage articles.

  The RFID tag includes a tag antenna unit and a tag IC chip. Among these RFID tags, an RFID tag called a passive type generates power by receiving an inquiry signal (radio wave) output from the antenna of the RFID reader device at the tag antenna unit, and operates the tag IC chip with this power. It was.

  In the RFID reader device, a power amplifying unit is provided in the transmitting unit in order to supply sufficient power to the RFID tag, and the output of the inquiry signal is increased by the power amplifying unit. For this reason, the power consumption of the power amplifying unit is large and the heat generation is also large, so that the RFID reader device becomes large by radiating heat with a large heat sink.

Under such circumstances, a technique has been proposed in which power consumption is suppressed by intermittently operating the power amplification unit of the transmission unit, thereby suppressing heat generation (see, for example, Patent Document 1).
JP-A-11-126240

  Since the conventional RFID reader device operates the transmission unit intermittently, the RFID tag power may be insufficient during the period when the output from the transmission unit is stopped, and the operation becomes unstable when the power is insufficient. There was a problem that communication quality deteriorated.

  Accordingly, an object of the present invention is to suppress power consumption while maintaining communication quality with an RFID tag.

  In order to achieve this object, an RFID reader apparatus of the present invention is an RFID reader apparatus that transmits an inquiry signal including a data signal and a carrier wave to an RFID tag and receives a response signal from the RFID tag. A power amplifying unit for amplifying power; and an operation region switching unit for switching an operation region of the power amplifying unit between a modulation period for modulating and transmitting a carrier wave with a data signal and a non-modulating period for transmitting the carrier wave without modulation, The operation region switching unit sets an operation region in the linear amplification region of the power amplification unit during the modulation period, and sets an operation region in the non-linear amplification region of the power amplification unit during the non-modulation period. With such a configuration, the intended purpose is achieved.

  As described above, according to the present invention, the power amplifying unit that amplifies the power of the inquiry signal, the operation of the power amplifying unit with the modulation period in which the carrier wave is modulated and transmitted with the data signal and the non-modulation period in which the carrier wave is transmitted without modulation. An operation region switching unit that switches regions, the operation region switching unit sets the operation region in the linear amplification region of the power amplification unit during the modulation period, and sets the operation region in the nonlinear amplification region of the power amplification unit during the non-modulation period. Set.

  As a result, the inquiry signal is amplified in the class A amplification region with good linearity in the modulation period to maintain the signal quality, and in the non-modulation period, the inquiry signal is amplified in the class AB amplification area to Since efficiency can be improved, power consumption can be suppressed and heat generation can be suppressed while maintaining communication quality with the RFID tag.

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

(Embodiment)
First, an outline of an RFID system in which an RFID reader device according to an embodiment of the present invention is used will be described with reference to FIGS.

  1 is a schematic diagram showing a configuration of an RFID system 8 including an RFID reader device and an RFID tag according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a frequency allocation state of signals used in the RFID system 8, and FIG. FIG. 4 is a waveform diagram of a signal transmitted from the RFID reader device 5 used in the RFID system 8, and FIG. 4 is a block diagram showing a configuration of the RFID system 8.

  FIG. 1 shows an example in which the RFID system 8 according to the present embodiment is used in the manufacturing process of the article 1. In this manufacturing process, the article 1 to which the RFID tag 4 is attached is conveyed in the direction of the arrow by a conveying device such as a belt conveyor (not shown). A central control device 2 that controls the entire manufacturing process is provided, controls the RFID reader device 5 via the communication line 3, and the RFID reader device 5 communicates with the RFID tag 4 to manage the article 1. The manufacturing process is managed by reading the number.

  An RFID tag 4 is attached to each of the articles 1, and an RFID reader device 5 is installed at a predetermined position of the transport device in the manufacturing process. The RFID reader device 5 reads the tag information of the RFID tag 4 when the RFID tag 4 attached to the article 1 enters a communicable area. The RFID reader device 5 transmits an inquiry signal to the RFID tag 4 by radio waves by the transmission antenna 6, and receives a response signal returned from the RFID tag 4 by the reception antenna 7. An area indicated by a broken line in FIG. 1 indicates a range of an area in which each RFID reader device 5 can communicate. When a plurality of RFID reader devices 5 are received even if they are close to each other, areas where communication is possible may overlap each other.

  In such a manufacturing process, when the article 1 is conveyed to a predetermined position, an inquiry signal for inquiring a management number is transmitted from the RFID reader device 5 to the RFID tag 4 of the article 1.

  When receiving the inquiry signal, the RFID tag 4 demodulates the inquiry content and returns a response signal such as a management number of the article 1 in response to the inquiry.

  The RFID reader device 5 receives the response signal returned from the RFID tag 4 and identifies the management number of the article 1. In accordance with the identified management number, the central control device 2 controls a manufacturing device (not shown) in the manufacturing process and the like, and performs predetermined processing and assembly on the article 1.

  FIG. 2 shows an example of using frequencies used for communication in the RFID reader device 5. Here, 952 MHz to 954 MHz are allocated for RFID, and 9 channels from CH1 to CH9 are set at intervals of 200 kHz. When a plurality of RFID reader devices 5 are provided close to each other and their communicable areas overlap, signals of different channels are used in each RFID reader device 5 so that signals do not interfere with each other. The For example, the first RFID reader device 5 is set to use CH1, and the adjacent second RFID reader device 5 is set to use CH3. The channel to be used can be controlled by the central control device 2, for example.

  In addition to the UHF band (for example, 952 MHz to 955 MHz) as described above, a frequency of a microwave band (for example, 2.45 GHz) and an HF band (for example, 13.56 MHz) can also be used as the predetermined carrier wave.

  FIG. 3 shows an example of an inquiry signal transmitted from the RFID reader device 5 to the RFID tag 4 in the RFID system 8. This inquiry signal includes a period D for inquiring the RFID tag 4 for a management number and the like, and a period for waiting for receiving a response signal returned from the RFID tag 4 and transmitting a carrier wave for supplying power to the RFID tag 4 S.

  In the period D (hereinafter referred to as “modulation period D”), the RFID reader device 5 transmits an inquiry signal obtained by modulating a carrier wave of a predetermined channel with a data signal toward the RFID tag 4.

  In a period S such as standby (hereinafter, referred to as “non-modulation period S”), the RFID reader device 5 transmits a continuous unmodulated carrier wave that is not modulated toward the RFID tag 4. Normally, the time length of the modulation period D and the non-modulation period S is set to about 10 msec, which is considerably longer, about 5 times or more in the latter. In the RFID tag 4, the response signal is returned to the RFID reader device 5 by changing the reflection state (backscatter) of the unmodulated carrier wave reflected from the tag antenna unit according to the data responding to the unmodulated period S. Details of this response signal will be described later.

  Next, the configuration and operation of the RFID system 8 including the RFID tag 4 and the RFID reader device 5 will be described with reference to FIG.

  First, the state in which the RFID reader device 5 starts to communicate with the RFID tag 4 will be described. The RFID reader device 5 is controlled by the central control device 2 so as to transmit an inquiry signal such as “Reply management number” to the RFID tag 4. The control signal is transmitted from the interface 51 of the RFID reader device 5 to the control unit 52 via the communication line 3.

  As a result, the control unit 52 reads data necessary for an inquiry from the memory unit 53. The carrier for a predetermined channel is ASK (Amplitude Shift Keying) modulated by the modulator 54 using the data for inquiry, amplified by the transmitter 55, and transmitted to the RFID tag 4 via the transmission antenna 6 as radio waves. .

  Next, the RFID tag 4 includes a tag antenna unit 41 and a tag IC chip 42, and the tag antenna unit 41 receives a radio wave inquiry signal. Then, the received signal is first rectified by the diode 43 to generate a DC voltage (hereinafter referred to as “DC voltage”). The DC voltage is charged in the capacitor 44 and supplied to each part of the tag IC chip 42 as an operation power source, and the tag IC chip 42 is activated. As a result, the control unit 45, demodulation unit 46, modulation unit 47, and memory unit 48 of the tag IC chip 42 are activated. As described above, the passive RFID tag 4 can operate the tag IC chip 42 without mounting a power source such as a battery.

  Since the passive RFID tag 4 uses power generated from a signal received by the tag antenna unit 41, its power supply capacity is small. For this reason, the power consumption of each part is suppressed as much as possible in the tag IC chip 42.

  Next, in response to an instruction from the control unit 45 in the RFID tag 4, when the inquiry data “Respond management number” is demodulated from the radio wave received by the demodulation unit 46, the control unit 45 stores and holds it from the memory unit 48. Read tag number of management number.

  If the tag information stored in the memory unit 48, that is, the management number of the article 1 is “management number A”, the control unit 45 creates response data “management number A” in response to the inquiry. Thus, a response signal is returned by turning on and off the switch 49 (for example, a switch element such as a transistor) via the modulation unit 47.

  That is, when the switch 49 is turned on, the terminal of the tag antenna unit 41 is short-circuited, and when the switch 49 is turned off, the terminal of the tag antenna unit 41 is opened. Thus, whether or not to reflect the unmodulated carrier wave transmitted from the RFID reader device 5 (back scatter) is controlled according to the response data “reference number A”, and the content of the response data is controlled by the RFID reader. A reply can be sent to the device 5.

  Note that the RFID tag 4 has a capacitor 50 for matching impedance so that no reflection occurs when the terminal of the tag antenna unit 41 is opened.

  Next, when the response signal is returned from the RFID tag 4 in this manner, the RFID reader device 5 transmits the response signal received by the receiving antenna 7 to the demodulating unit 57 via the receiving unit 56 and returns the response data. Demodulate. Based on the demodulated response data, the control unit 52 confirms the existence of “management number A”. The RFID reader device 5 stores the information of “management number A” in the memory unit 53 via the control unit 52.

  Then, the information of “management number A” stored in the memory unit 53 is transferred to the central controller 2. The central controller 2 retrieves product information from a database (not shown) stored in the storage unit based on the information of “management number A”, and manages and controls processing, assembly, and the like for the article 1. In the database, various information related to the manufacture of the article 1 is stored as management information.

  Further, the RFID reader device 5 is predetermined when the RFID tag 4 storing the “management number” does not exist even though the control unit 52 inquires the RFID tag 4 that “respond the management number”. Therefore, the control unit 52 determines that the RFID tag 4 does not exist from this “no response”.

  The RFID reader device 5 also includes a clock unit 58 that generates a clock signal for performing modulation and synchronization, and a power source unit 59 for supplying power to each unit. The power supply unit 59 includes, for example, a battery that generates a DC voltage, a power supply circuit that creates a DC voltage from a commercial power supply, and the like.

  In the above description, the RFID system 8 in the manufacturing process has been described as an example. However, in addition to the above, the present invention can be used for various purposes such as storage management at a store and cashier settlement.

  As described above, the RFID system 8 that reads the tag information of the RFID tag 4 is configured by the RFID reader device 5. However, if the communication distance between the RFID reader device 5 and the RFID tag 4 is increased, the RFID reader device 5 A high output inquiry signal must be transmitted, and power consumption in the transmission unit 55 becomes a problem. That is, when the power consumption is large, the power supply unit 59 is consumed greatly, and heat is generated in the transmission unit 55, which causes a problem that the structure for heat dissipation must be enlarged.

  Therefore, in the RFID reader device 5 of the present embodiment, power consumption in the transmission unit 55 is suppressed while maintaining communication quality with the RFID tag 4. For this reason, the RFID reader device 5 reduces the power consumption by switching the operation region of the power amplification unit that amplifies the inquiry signal in the transmission unit 55 between the modulation period D and the non-modulation period S. That is, among the inquiry signals, when a carrier wave modulated with a data signal is amplified, the power amplifier is operated in a linear amplification region that consumes a large amount of power but hardly generates waveform distortion. It is characterized in that overall power consumption is reduced by switching the power amplifying unit to operate in a non-linear amplification region where distortion occurs but efficiency is low and power consumption is low. Details of the power amplifying unit will be described later.

  The reason why the power can be reduced by switching the operation region of the power amplifier in this manner is because the characteristics of the inquiry signal to be transmitted are used. That is, in the non-modulation period S with a long occupation time, the inquiry to be amplified is only a high-frequency carrier wave that is not modulated by the data signal. Therefore, even if waveform distortion occurs in the power amplifier, the generated harmonic component is low-passed. It can be easily removed with a filter or a bandpass filter. Therefore, in this non-modulation period S, the operation of the power amplifying unit can be set to efficient class AB or class B, and power consumption can be reduced.

  However, since the carrier wave is modulated by the data signal in the modulation period D, it is necessary to prevent waveform distortion. In this modulation period D, the power amplification unit is not efficient but is of class A with good linearity. It is necessary to switch to amplification.

  Hereinafter, the principal part of the RFID reader device 5 of the present embodiment will be described in detail with reference to FIGS.

  5 is a block diagram of the transmission unit 55 and the modulation unit 54 used in the RFID reader device 5 according to the embodiment of the present invention. FIG. 6 is a circuit of the power amplification unit 72 in the transmission unit 55 used in the RFID reader device 5. FIG. 7 is a characteristic diagram for explaining the switching state of the operation region of the power amplification unit 72 in the RFID reader device 5, and FIG. 8 is a waveform for explaining the timing of the operation region switching of the power amplification unit 72 in the RFID reader device 5. FIG.

  FIG. 9 is a diagram for explaining the distortion state of the output signal due to the difference in the operation region of the power amplifying unit 72 in the RFID reader device 5. FIG. 9A shows the carrier signal component and the modulation data signal in the output signal. FIG. 9B is a frequency spectrum diagram illustrating an example in which a noise component is included in the output signal of FIG. 9A. FIG. 10 is a diagram for explaining the distortion state of the output signal of the power amplifying unit 72 in the RFID reader device 5, and FIG. 10 (A) is a frequency spectrum diagram showing an example when the output signal has a single frequency. FIG. 10B is a characteristic diagram showing an example of the fundamental wave component and the harmonic component of the output signal. FIG. 11 is a waveform diagram for explaining a method of reducing the generation of harmonics in the RFID reader device 5.

  First, in FIG. 5, in the modulation unit 54, the carrier wave generation circuit 61 generates a carrier wave 100 of a predetermined channel in the 953 MHz band. On the other hand, the data signal generation circuit 62 generates a data signal to be transmitted to the RFID tag 4 based on an instruction from the control unit 52, for example, a data signal 101 “Reply management number”. The modulation unit 54 generates a band-limited signal 102 obtained by band-limiting this data signal using the band-limiting filter 63, amplifies the band-limited signal 102 using an amplifier circuit 66 that can change the amplification factor, and then uses the modulation circuit 64 to generate a carrier wave. Is subjected to ASK modulation to generate an inquiry signal 103 as shown in FIG.

  Then, the transmission unit 55 amplifies the inquiry signal by the power amplification unit 72. The transmission unit 55 amplifies the inquiry signal by the power amplification unit 72, removes the harmonic component of the carrier wave included in the inquiry signal by the matching circuit 79 or the low-pass filter 73, and transmits the signal from the transmission antenna 6 toward the RFID tag 4. To do. The amplitude control unit 65 and the gain control circuit 67 will be described later.

  FIG. 6 shows a specific circuit example of the power amplifying unit 72, and an N-channel MOS-FET (hereinafter referred to as “transistor”) Q is used as an amplifying element. The inquiry signal from the modulation unit 54 is applied to the gate of the amplifying transistor Q via the coupling capacitor Ca and the matching circuit 76 (capacitors Cb and Cc and the coil La). A bipolar transistor may be used instead of the N-channel MOS-FET.

  Further, the operation region switching signal 202 from the bias control circuit 74 as the operation region switching unit is applied as a bias voltage to the gate of the transistor Q via the resistor Ra and the high frequency separation circuit 77 (capacitor Cg and resistor Rb). Then, DC power is supplied to the drain of the transistor Q via the high frequency separation circuit 78 (capacitors Ch, Ci and coil Lb), and the amplified output is supplied to the drain via the matching circuit 79 (capacitors Cd, Ce and coil Lc) and capacitor Cf. Output.

  Note that when a bipolar transistor is used, the bias voltage for controlling the base current is controlled. Further, the resistance value connected to the gate may be changed so as to correspond to the control of the bias voltage.

  5 and 7, the bias control circuit 74 switches the operation region of the power amplifier 72 according to the modulation period D and the non-modulation period S by the operation region switching signal 202. That is, the bias control circuit 74 sets the operation region of the power amplifier 72 to the linear amplification region s in the modulation period D and to the non-linear amplification region d in the non-modulation period S.

  As shown in FIG. 8, the inquiry signal 201 to be transmitted by the RFID reader device 5 has a modulation period D for transmitting a carrier wave modulated with a data signal and a non-modulation period S for transmitting an unmodulated carrier wave. ing. Among these, in the modulation period D, the data signal for inquiry cannot be correctly transmitted to the RFID tag 4 unless the waveform of the signal created by the modulator 54 is faithfully maintained and amplified. That is, the frequency spectrum of the output signal in the modulation period D must be as shown in FIG. The signal shown in FIG. 9A includes a carrier wave component and a frequency component (including a harmonic component) of the data signal for modulation.

  If the linearity of the power amplifier 72 is poor and the waveform is distorted, as shown in FIG. 9B, the signal contains a lot of noise components, and the data signal for inquiry cannot be transmitted correctly.

  Therefore, the RFID reader device 5 according to the present embodiment operates according to the control from the control unit 52, as shown in FIG. 8, the operation region switching signal 202 that becomes high level during the modulation period D and low level during the non-modulation period S. Is applied as a bias voltage from the bias control circuit 74 to the gate of the transistor Q. As a result, during the period when the operation region switching signal 202 is at a high level, the operation region of the transistor Q is set to a class A amplification region (linear amplification region) having good linearity indicated by d in FIG. The output modulated wave Dout can be output in a state where Din is amplified with good linearity and waveform distortion does not occur.

  On the other hand, in the non-modulation period S, the low-level operation region switching signal 202 is applied to the gate of the transistor Q. As a result, the gate bias of the transistor Q is set to a low voltage, the operation region is set to the class AB indicated by s in FIG. 7, the input signal Sin of the unmodulated carrier wave is amplified, and the output signal Sout is output. At this time, since amplification is performed in the non-linear amplification region s, as shown in FIG. 10A, even if the input unmodulated carrier wave Sin having a frequency spectrum of a single frequency is amplified, the amplified output signal Sout will be As shown in B), the output includes harmonic components S2, S3,... In addition to the fundamental component S1. However, since the harmonic components S2, S3,... Have a frequency far away from the fundamental wave component S1, they can be easily removed by the low-pass filter 73, and the unmodulated carrier wave of the fundamental wave component S1. Only Sout can be taken out and transmitted.

  As can be understood from FIG. 7, the drain current of the non-linear amplification region s can be greatly reduced by lowering the bias voltage of the transistor Q compared to the linear amplification region d. Since this drain current always flows by the bias voltage even when the modulation wave Din or the input signal Sin is 0 (idle current), the power consumption in the transistor Q, that is, the power consumption of the power amplifier 72 can be greatly reduced. For example, as shown in FIG. 7, the idle current can be reduced from 0.6 (A) to 0.11 (A). Thereby, the power consumption as a whole can be reduced, and the effect that heat generation can be suppressed can be obtained.

  However, as shown in FIG. 7, since the amplification factor is smaller in the non-linear amplification region s than in the linear amplification region d, both the output signals Dout and the transistor Q, that is, by switching the operation region of the power amplification unit 72, Control that keeps the amplitude of Sout the same is necessary.

  For this reason, the RFID reader device 5 in the present embodiment is provided with an amplitude control unit 65 in the modulation unit 54. The amplitude control unit 65 includes an amplification circuit 66 and a gain control circuit 67. The gain control circuit 67 stores a control table. The gain control circuit 67 controls the amplification factor of the amplifier circuit 66 based on the input operation region switching signal VB and the control table. In the control table, correction information for making the amplitude of the output signal the same based on the amplification factor for each operation region of the power amplifier 72 is recorded.

  Accordingly, the amplitude of the input unmodulated wave Sin when operating in the nonlinear amplification region s is controlled to be larger than the amplitude of the input unmodulated wave Din when operating in the linear amplification region d, and the transistors Q, That is, it is possible to control so that the amplitudes of both the output signals Dout and Sout are kept the same even by switching the operation region of the power amplifier 72. FIG. 8 shows a gain signal 203 for controlling the amplification factor output from the gain control circuit 67. The amplification circuit 66 changes the amplification factor according to the voltage level of the gain signal. When the gain signal 203 is increased, the amplification factor of the amplifier circuit 66 is increased. On the other hand, when the gain signal 203 is lowered, the amplification factor of the amplifier circuit 66 is reduced.

  In addition, if the amplification factor of the transistor Q and the amplifier circuit 66, that is, the power amplifier 72 is changed suddenly when switching between the modulation period D and the non-modulation period S, an unnecessary waveform distortion component is generated. As shown, the voltages of the operation region switching signal 202 and the gain signal 203 are gradually changed when the operation region before and after the modulation period D is switched.

  Similarly, as shown in FIG. 11, even when the carrier wave 100 is modulated by the data signal 101, unnecessary modulation distortion is prevented from occurring. That is, when the carrier wave 100 is modulated by the data signal 101, the data signal 101 created by the data signal generation circuit 62 is passed through the band limiting filter 63 to generate a signal with reduced wideness. Thereby, the band limited signal 102 in which the rising edge and the falling edge of the data signal 101 are made gentle is generated. By subjecting the carrier wave 100 to ASK modulation using the band-limited signal 102, an inquiry signal 103 (a signal obtained by modulating the carrier wave with a data signal) having a smooth rise and fall can be created. Here, since the amplifying circuit 66 amplifies the output of the band limiting filter 63, the frequency band necessary for the amplification of the band limiting signal 102 is low, and for example, it may have a band of about several hundreds KHz. As described above, the amplifier circuit 66 can easily amplify the band limited signal 102.

  As described above, according to the RFID reader device 5 in the present embodiment, the operation regions d and s of the power amplification unit 72 of the transmission unit 55 are switched between the modulation period D and the non-modulation period S. The power consumption can be reduced and heat generation can be suppressed.

  The means for switching the operation region of the power amplifying unit 72 is not limited to the one in the present embodiment, and any means may be used.

  Further, any data signal encoding method can be used. For example, a mirror subcarrier system can be used in addition to the FM0 system.

  Further, the present invention can be applied not only to the RFID system 8 using the passive RFID tag but also to the RFID system 8 using the active RFID tag.

  Moreover, although the example in which the amplitude control unit 65 is provided in the modulation unit 54 and the amplification factor of the amplification circuit 66 that amplifies the output of the band limiting filter 63 is changed is described, the present invention is not limited to this. . For example, an amplifier circuit may be provided at the output stage of the modulation circuit 64 and the amplification factor of this amplifier circuit may be controlled. The gain control circuit 67 may monitor the output of the power amplifier 72 and control the amplifier so that the amplitude of the output of the power amplifier 72 is constant.

  As described above, according to the present invention, the power amplifying unit that amplifies the power of the inquiry signal, the operation of the power amplifying unit with the modulation period in which the carrier wave is modulated and transmitted with the data signal and the non-modulation period in which the carrier wave is transmitted without modulation. An operation region switching unit that switches regions, the operation region switching unit sets the operation region in the linear amplification region of the power amplification unit during the modulation period, and sets the operation region in the nonlinear amplification region of the power amplification unit during the non-modulation period. Set.

  For this reason, in the modulation period, the inquiry signal is amplified in the class A amplification region having good linearity to maintain the signal quality, and in the non-modulation period, the inquiry signal is amplified in the class AB amplification region to Since the efficiency can be improved, it is useful as an RFID reader device that can reduce power consumption and heat generation while maintaining communication quality with the RFID tag.

1 is a schematic diagram showing a configuration of an RFID system including an RFID reader device and an RFID tag according to an embodiment of the present invention. Explanatory drawing which shows the frequency allocation state of the signal used for the RFID system Waveform diagram of signal transmitted from RFID reader device used in the RFID system Block diagram showing the configuration of the RFID system Block diagram of a transmitter and a modulator used in the RFID reader device according to the embodiment of the present invention Detailed circuit diagram of the power amplifier in the transmitter used in the RFID reader device A characteristic diagram for explaining the switching state of the operation region of the power amplification unit in the RFID reader device Waveform diagram for explaining the switching timing of the operation region of the power amplification unit in the RFID reader device (A) is a frequency spectrum diagram showing an example in which the output signal of the power amplifier in the RFID reader device includes a carrier wave component and a frequency component of a data signal for modulation, and (B) is an output signal of (A). Frequency spectrum diagram showing an example of including noise components (A) is a frequency spectrum diagram showing an example when the output signal of the power amplification unit in the RFID reader device has a single frequency, and (B) is a fundamental wave component of the output signal of the power amplification unit in the RFID reader device. Characteristic diagram showing examples of harmonic components Waveform diagram for explaining a method of reducing the generation of harmonics in the RFID reader device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Goods 2 Central control apparatus 3 Communication line 4 RFID tag 5 RFID reader apparatus 6 Transmission antenna 7 Reception antenna 8 RFID system 41 Tag antenna part 42 Tag IC chip 43 Diode 44,50, Ca-Cg capacitor 45,52 Control part 46, 57 demodulation unit 47, 54 modulation unit 48, 53 memory unit 49 switch 51 interface 55 transmission unit 56 reception unit 58 clock unit 59 power supply unit 61 carrier wave generation circuit 62 data signal generation circuit 63 band limiting filter (first filter)
64 modulation circuit 65 amplitude control unit 66 amplification circuit 67 gain control circuit 72 power amplification unit 73 low-pass filter (second filter)
74 Bias control circuit 76 Matching circuit 79 Matching circuit (second filter)
77, 78 High frequency separation circuit La to Lc Coil Q N channel MOS-FET (transistor)

Claims (6)

An RFID reader device that transmits an inquiry signal including a data signal and a carrier wave to an RFID tag and receives a response signal from the RFID tag,
A power amplifying unit for amplifying the power of the inquiry signal;
An operation region switching unit that switches an operation region of the power amplification unit between a modulation period for modulating and transmitting the carrier wave with the data signal and a non-modulation period for transmitting the carrier wave without modulation;
The operation region switching unit sets the operation region in the linear amplification region of the power amplification unit in the modulation period, and sets the operation region in the non-linear amplification region of the power amplification unit in the non-modulation period. A featured RFID reader device. The RFID reader device according to claim 1, wherein the operation region switching unit switches the operation region by changing a bias voltage of the power amplification unit. 3. The RFID reader device according to claim 1, further comprising a first filter that limits a band of the data signal. The RFID reader device according to any one of claims 1 to 3, further comprising a second filter that limits an output band of the power amplification unit. The RFID reader device according to any one of claims 1 to 4, further comprising an amplitude control unit configured to make an output amplitude of the power amplification unit constant. The amplitude control unit controls an amplification factor of an amplification unit that amplifies an output of the second filter according to an amplification factor of the linear amplification region or the non-linear amplification region of the power amplification unit. The RFID reader device according to claim 5.

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