KR100836469B1 - Rfid reader and rfid system - Google Patents

Abstract

RFID reader according to the present invention comprises a plurality of antennas for transmitting and receiving RF signals; A path selector for selecting a transmission or reception path of the RF signal; An RF processor for processing an RF signal transmitted to a transmission or reception path of the path selector; And a controller for controlling path selection of the path selection unit.

RFID, USN, Reader, Tag

Description

RFID reader and RF system {RFID READER AND RFID SYSTEM}

1 is a configuration diagram of a conventional RFID system.

2 is a block diagram of an RFID system according to an embodiment of the present invention.

3 is a detailed configuration diagram of the electronic tag according to the present invention.

4 is a detailed configuration diagram of an RFID reader according to an embodiment of the present invention.

5 is a view showing the operation of the path selection unit of the RFID reader according to an embodiment of the present invention.

6 is a detailed configuration diagram of an RF transmitter of an RFID reader according to an embodiment of the present invention.

7 is a waveform diagram of a signal transmitted and received in a conventional RFID reader.

8 is a waveform diagram of a signal transmitted and received by the RFID reader of the present invention.

9 is a view showing a modulated RF signal in an RFID reader according to an embodiment of the present invention, (a) is a waveform diagram of a DSB or SSB-ASK modulated RF signal, (b) is a PR-ASK modulated RF signal Waveform diagram.

10 is a diagram illustrating a PIE symbol in an RFID reader according to an embodiment of the present invention.

11 is a diagram illustrating a PR-ASK modulated RF envelope in an RFID reader according to an embodiment of the present invention.

12 is a table showing the RF envelope parameters of FIG.

The present invention relates to an RFID reader and an RFID system.

Ubiquitous Sensor Network (USN) technology attaches an electronic tag wherever necessary, and detects not only basic object details but also environmental information such as temperature, humidity, pollution level, and crack information. This means connecting to the network in real time and managing the information. It gives computing and communication functions to all things, creating a ubiquitous environment that can communicate anytime, anywhere.

The ubiquitous sensor network develops around RFID (Radio Frequency Identification) technology that provides recognition information, and as a sensing function is added, the ubiquitous sensor network is developed to form a network between them.

The radio frequency identification (RFID) is a technology for transmitting and receiving information from an electronic tag attached to a thing using radio frequency and providing a service related thereto.

RFID systems use several frequency bands, including low frequency (125 kHz, 135 kHz), high frequency (13.56 MHz), UHF (433 MHz, 860-960 MHz), and microwave (2.45 GHz), and each has a different method of use and application range. Among them, the UHF band is expanding to all areas of life, including distribution and logistics, because it can transmit long-distance signals and relatively high-speed transmission.

1 is a view showing a conventional RFID system.

Referring to FIG. 1, the RFID system 100 includes an RFID reader 101 and an electronic tag 102. The RFID reader 101 includes an internal or external antenna, which emits an active signal to form an electromagnetic field, ie an RF field. When the electronic tag 102 enters the RF field 105, the electronic tag 102 receives an active signal emitted from the antenna of the RFID reader 101, and uses the received active signal in the tag. The stored information is transmitted to the RFID reader 101. Thereafter, the RFID reader 101 receives and analyzes the information transmitted from the electronic tag 102 and acquires unique information of the object on which the electronic tag is mounted.

In addition, the unique information of the object obtained by the RFID reader 101 provides a foundation that can be efficiently used for logistics / distribution management such as distribution, assembly, price change, and sale of the object.

Such RFID technology is expected to be widely used in livestock, medical, aviation, distribution, logistics, manufacturing, etc. due to the development of chip manufacturing, miniaturization, wireless communication, and various solution programs.

However, a change occurs in the propagation environment depending on factors such as the position and speed at which the electronic tag passes through the RF field of the RFID reader, and the packaging material (for example, pallet load) of the product with the electronic tag. As the radio environment changes, the error rate, stability, recognition distance, etc. of the data received by the RFID reader may be different. Therefore, the factors that decrease the recognition rate of the electronic tag and the reliability of the RFID system are caused. do.

As such, technologies for improving the recognition rate of the electronic tag due to internal or external factors of the RFID reader have been developed.

The present invention provides an RFID reader and an RFID system.

The present invention provides an RFID reader capable of arranging a plurality of antennas in one RFID reader.

The present invention provides an RFID reader capable of isolating a transmission or reception path of an RF signal in an RFID reader.

The present invention provides an RFID reader capable of transmitting an electronic tag and an RF signal modulated by various modulation schemes.

The present invention provides an RFID reader and an RFID system capable of transmitting a passive electronic tag and an RF signal modulated by various modulation schemes.

RFID reader according to an embodiment of the present invention comprises a plurality of antennas for transmitting and receiving RF signals; A path selector for selecting a transmission or reception path of the RF signal; An RF processor for processing an RF signal transmitted to a transmission or reception path of the path selector; And a controller for controlling path selection of the path selection unit.

According to an embodiment of the present invention, an RFID reader includes: a phase shifter configured to convert an input RF signal into a first RF signal having a first phase and a second RF signal having a second phase, and modulate the RF signal according to data; A signal selector configured to select the first or second RF signal of the phase shifter according to a modulation scheme; And a controller for controlling a signal output path and a period of the phase shifter and the signal selector according to a coding format.

In addition, the RFID system according to an embodiment of the present invention comprises at least one passive electronic tag; It includes an RFID reader having a plurality of antennas, and performs communication in different modulation schemes according to the electronic tag and the coding format.

An RFID reader and an RFID system using the same according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing an RFID system according to an embodiment of the present invention.

2, the RFID system 200 processes an electronic tag (tag or transponder or label) 201, an RFID reader (Reader or interrogator) 210, and information read from the electronic tag 201. A host computer (not shown).

The electronic tag 201 stores unique information about each object and is printed or attached to the object. For example, the speaker may be manufactured in the form of a speaker and attached to each object passing through the logistics inspection area.

The RFID reader 210 performs wireless communication with at least one electronic tag 201 and reads and decrypts unique information of the electronic tag 201.

The RFID reader 210 includes a plurality of antennas 211 to 214, sequentially transmits RF signals using the plurality of antennas 211 to 214, and receives an RF signal from the electronic tag 201. . Each of the antennas 211 to 214 may be disposed in the moving region of the electronic tag 201. For example, the first and second antennas 211 and 212 communicate in one region (left) where the electronic tag 201 moves, and the third and fourth antennas 213 and 214 move the electronic tag 201. The communication is performed in the other side (right side). In addition, the radiation angles of the first to fourth antennas 211 to 214 may be arranged differently.

Here, the RFID reader 210 performs switching control of the plurality of antennas 211 to 214 at high speed to perform wireless communication with the electronic tag 201 through any one antenna.

The RFID reader 210 radiates an information request signal using a plurality of antennas 211 to 214, and the electronic tag 201 generates tag identification information after receiving the information request signal and generates an RFID reader 210. By transmitting to the RFID reader 210 receives the tag identification information is recognized.

3 is a detailed block diagram of an electronic tag according to an embodiment of the present invention.

Referring to FIG. 3, the electronic tag 201 is classified into an active tag or a passive tag according to whether the electronic tag 201 has its own power source, and includes a low frequency (125 kHz and 135 kHz) and a high frequency. 13.56MHz), UHF band (400MHz ~ 960MHz), microwave (2.45GHz), etc. are used in several frequency bands. Hereinafter, the present invention will be described based on a passive electronic tag operating in the UHF band.

The electronic tag 201 includes an antenna 202, a demodulator 203, a modulator 205, a controller 206, and a memory 207. The antenna 202 may be implemented as a dipole antenna.

The demodulator 203 demodulates the information request signal received from the antenna 202 and transmits the demodulated information request signal to the control unit 206. The control unit 206 uses the data stored in the memory to identify the tag identification information corresponding to the information request signal. Create and perform communication according to the communication protocol. The modulator 205 modulates the generated tag identification information and outputs it through the antenna 202.

The electronic tag 201 receives a signal of the RFID reader to rectify / multiply the RF power to use as a power supply, and transmits a frequency signal received from the RFID reader by reflection modulation to send information.

The electronic tag 201 uses double-sideband amplitude shift keying (DSB-ASK), single-sideband amplitude shift keying (SSB-ASK), and PR using a pulse-interval encoding (PIE) format and a Machester format. Phase-reversal amplitude shift keying (ASK) is used to receive modulated RF signals as operating energy.

4 is a detailed block diagram of an RFID reader according to an embodiment of the present invention.

Referring to FIG. 4, the RFID reader 210 includes a plurality of antennas 211 to 214, a path selector 220, an RF processor 230, a baseband processor 240, a Q-RSSI unit 251, and I. -RSSI unit 252 and control unit 260.

The path selector 220 includes first to third switching units 221, 222, and 223, and the first switching unit 221 is connected to a plurality of antennas 211 to 214 to transmit or receive an RF signal. The second switching unit 222 is connected to the first switching unit 221 to select a transmission or reception path. In addition, the third switching unit 223 circuitically isolates the transmitting side and the receiving side in order to protect the receiving side in the transmission mode and connects to the receiving path in the receiving mode.

Here, the first switching unit 221 may be connected to the plurality of antennas (211 ~ 214) by performing a high-speed switching operation several times per second sequentially or randomly, thereby monitoring the area in which the electronic tag is moved.

The first to third switching units 221, 222, and 223 may be implemented in various forms. For example, it may be implemented as a semiconductor switch device such as a single pole quadruple throw (SPQT) and a single pole double throw (SPDT), or a logic device such as multiplex / de-multiplex (MUX / DEMUX).

The RF processor 230 includes an RF receiver 231 and an RF transmitter 232, and performs an RF signal modulation and demodulation function.

The RF receiver 231 suppresses a noise component included in a signal received through the third switching unit 223 in the reception mode, amplifies only a signal of a required band, and demodulates the original data into a baseband processor ( 240).

The RF transmitter 232 modulates data input from the baseband processor 240 into an RF signal, amplifies the modulated RF signal with transmission power, and outputs the modulated RF signal to the second switching unit 222.

The baseband processor 240 converts the data demodulated by the RF receiver 231 into a digital signal, or converts the digital data into an analog signal and transmits the digital data to the RF transmitter 232.

Received Signal Strength Indication (Q-RSSI) unit 251 and I-RSSI unit 252 is a circuit for measuring the reception strength of the received quadrature-phase (Q) and in-phase (I) signal, the interference of radio waves This is a circuit to detect and correct the signal strength increases and irregularities due to the occurrence or mixing of noise components.

The control unit 260 is provided with a communication protocol to control the electronic tag and wireless communication, and periodically sends an information request signal to the electronic tag. In addition, the controller 260 analyzes and extracts tag identification information through digital data input from the baseband processor 240 and receives the received signal strengths input from the I-RSSI unit 252 and the Q-RSSI unit 251. According to the control, the transmission power, the modulation method, and the like of the RF transmitter 232 are controlled.

Here, the controller 260 may use a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit.

The controller 260 receives information such as digital data transmitted from the baseband processor 240 and a reception strength of an I / Q signal, and transmits the received information to a host computer. In addition, the switching of the first to third switching units 221, 222, and 223 according to the transmission or reception mode is controlled to control the transmission or reception of the RF signal.

At this time, the control unit 260 transmits a control signal by executing a program reflecting the cycle information, order information, etc. of the switching operation of each switching unit (221, 222, 223).

The operation of the RFID system will be described in detail as follows.

Referring to FIGS. 2 to 4, when the RFID reader is operated, the controller 260 controls the switching operation and the connection period of the second and third switching units 222 and 223 according to the transmission mode or the reception mode.

In the transmission mode, the second and third switching units 222 and 223 of the path selector 220 are connected to the transmission path. In this case, the third switching unit 223 isolates the transmitting side and the receiving side in a circuit, thereby preventing the transmission signal from flowing into the receiving side.

The controller 260 transfers the information request signal to the baseband processor 240, and the baseband processor 240 converts the information request signal into an analog signal and transmits the information request signal to the RF transmitter 232. The RF transmitter 232 modulates an RF signal according to the information request signal and amplifies the RF signal to a transmission level to be radiated to any one antenna through the second switching unit 222 and the first switching unit 221.

In the reception mode, the second and third switching units 222 and 223 of the path selection unit 220 are connected to the reception path, and the RF signal of the electronic tag 201 is connected to the first switching unit 221 through any one antenna. ) And is input to the RF receiver 231 along the receiving paths of the second switching unit 222 and the third switching unit 223.

The RF receiver 231 low-noise amplifies and demodulates the received RF signal and outputs the demodulated signal to the baseband processor 240. The baseband processor 240 converts the demodulated signal into digital data and converts the demodulated signal into digital data. ) And the Q-RSSI unit 251 and the control unit 260.

The I-RSSI unit 252 and the Q-RSSI unit 251 respectively measure the reception strengths of the received I / Q signals, and then transfer them to the control unit 260. The control unit 260 receives the I / Q signals. The intensity is used to detect and correct irregular signal strength due to a mixture of radio wave interference and noise components. In addition, the controller 260 recognizes the digital data input from the baseband processor 240 as tag identification information.

5 is a detailed block diagram of a path selection unit according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the first switching unit 221 may include four antenna terminals a according to the first and second control signals Vctrl 1 and Vctrl 2 of the controller 260 input to the first decoder 224. : be).

The second switching unit 222 is connected to the transmitting terminal a-c or the receiving terminal a-b according to the third control signal Vctrl3 of the controller 260 input to the second decoder 225.

The third switching unit 223 is connected to the ground terminal a-b or the receiving terminal a-c according to the fourth control signal Vctrl4 of the controller 260 input to the third decoder 226.

Here, a signal of high power (EIRP = 4W) output from the RF transmitter 232 in the transmission mode is transmitted through the second switching unit 222, and some of the transmission signals (for example, about 5 dBm) are transmitted to the reception path. Can be introduced. In this case, since the third switching unit 223 is connected to the ground terminal GND in the transmission mode, the third switching unit 223 prevents the transmission signal from flowing into the reception terminal ac, thereby protecting the reception circuit and receiving in the transmission mode. In the process of switching to the mode, it is possible to reduce the influx of unwanted components such as spurious due to the RF transmission signal in the reception path. Accordingly, it is possible to recover the more accurate tag signal by preventing the variation of the received signal level input to the RF receiver, resulting in an attenuation effect of 25dB or more for the incoming signal in the transmission mode.

FIG. 7A is a waveform diagram of a transmission and reception signal when the transmission and reception paths are not isolated as in the prior art, and FIG. 7B is a transmission and reception when the transmission and reception paths are isolated in the present invention. Received signal waveform diagram.

Referring to FIG. 7A, when the RF signal Rt is transmitted in the transmission period D1, a level L1 (about 3.2 V) of a noise signal having a predetermined magnitude is introduced into the reception path and received in this state. When switching to the section D2, the received tag signal Rs is detected at an unstable level, thereby lowering the tag recognition rate. D1 and D2 are switching holding times in a transmission or reception mode.

Referring to FIG. 7B, when the RF signal Rt is transmitted in the transmission period D11, the incoming signal flows to the ground (GND) terminal in the receiving path, so that almost no noise signal is introduced and received. Since the tag signal Rs is detected at a stable level even when switching to the section D12, the tag recognition rate can be improved. D11 and D12 are switching holding times according to a transmission or reception mode.

As shown in FIG. 5, a reception filter 227 may be configured between the second switching unit 222 and the third switching unit 223, and the second switching unit 222 and the RF transmitter 232 may be configured. The transmission filter 228 may be configured between the two terminals. Here, the receive and transmit filters 227 and 228 may be implemented as surface acoustic wave (SAW) filters and remove noise components of the signal. An isolator 229 is connected to the output side of the RF transmitter 232. The isolator 229 transmits the attenuated signal in the reverse direction by attenuating the signal transmission direction without attenuation and blocking the reverse direction. You can block. Such isolators may be installed on the receive path.

6 is a detailed block diagram of an RF transmitter according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the RF transmitter 232 includes a PLL unit 233, a signal distributor 234, a phase shifter 235, a signal selector 238, and a power amplifier 239.

When the RF signal is output from the phase locked loop (PLL) unit 233, the signal distributor 234 divides the RF signal into two paths and outputs the first and second RF signals.

The phase shifter 235 includes first and second phase shifters 236 and 237, and the first and second phase shifters 236 and 237 may rotate the first and second RF signals inputted in respective paths by 180 degrees. It will transition to a phase difference. That is, the first phase shifter 236 shifts the phase Sin (2πf ₀ t) of the first RF signal by the first phase φ1, and the second phase shifter 237 performs the phase (2) of the second RF signal. Sin (2πf ₀ t)) is shifted by the second phase φ2 so that the phases φ1 and φ2 of the first and second RF signals S and S 'output from the phase shifter 235 are 180 degrees. It makes a difference.

The phase shifter 235 modulates the data input from the baseband processor into the RF signal and outputs the modulated data.

The signal selector 238 selects one of two signals having different phases and outputs the selected signal, which may be controlled by the controller 260 to output an RF signal having a desired phase. That is, it can be modulated and output in a desired modulation scheme.

At this time, the controller 260 controls the switching operation of the signal selector 238 connected to the output terminal of the phase shifter 235, which is a modulation method of pulse-interval encoding (PIE) format and Machester format, which is an RFID standard coding format. RF signals modulated by any one of double-sideband amplitude shift keying (DSB-ASK), single-sideband amplitude shift keying (SSB-ASK), and phase-reversal amplitude shift keying (PR-ASK) can be obtained.

The power amplifier 239 amplifies the modulated RF signal to transmit power and outputs the amplified signal. The RFID transmitter 232 of the present invention may be one or more antennas of the RFID reader.

FIG. 9A is a waveform illustrating a DSB-SSB ASK modulated RF signal, and FIG. 9B is a waveform illustrating a PR-ASK modulated RF signal. The modulation degree in the PR-ASK modulated RF signal is obtained as (A-B) / A, where phase Φ is the first phase φ1 of the first RF signal and phase -φ is the second phase Φ2 of the second RF signal.

Here, the coding format is UHF such as ISO 18000-A, IS0 18000-B, ISO 18000-C, Electronic Product Code (EPC) Class0 (EPC Generation-0), EPC Class1 (EPC Generation-1, EPC Generation-2), etc. The format according to the RFID protocol may be applied, and in the embodiment of the present invention, the coding format according to the EPC Generation-2 UHF RFID Protocol is used. Generation-2 of class 1 of the EPC may be applied to 18000-6, which is a formal standard of ISO.

In addition, the controller 260 may control switching cycles of the phase shifter 235 and the signal selector 238. The switching period is an interval corresponding to the response time of the electronic tag, and is controlled within a pulse width (PW) section, that is, 0.265 Tari to 0.525 Tari according to the PR-ASK modulation format.

As described above, the first or second RF signals S and S ′ having the first or second phases output from the phase shifter 235 are selectively output to be modulated by any one of coding scheme modulation schemes. By adjusting the pulse width of the modulated RF signal, signals of different modulation schemes can be sent to the electronic tag according to the coding format.

10 illustrates PIE symbols. Here, Tari means a reference time interval of a signal transmitted from the RFID reader to the electronic tag, and represents a period of data-0. The RFID reader communicates using a Tari value between 6.25us and 25us. Tari is derived from the ISO / IEC 18000-6 standard.

FIG. 11 is an enlarged view of a phase shift section in an RF envelope according to a PR-ASK modulation scheme. The pulse width PW is obtained by 0.5 * (A + B). The pulse width represents the pulse width of the RF envelope and is located at about 50% of the RF modulated signal pulse.

12 is a parameter of the RF envelope shown in FIG. 11, in which a pulse modulation degree, a rise time tr, a fall time tf, and a pulse width PW are defined.

Accordingly, the controller 260 of the RFID reader performs switching operations of the phase shifter 235 and the signal selector 238 during a pulse width (PW) period, that is, a predefined 0.265 to 0.525 Tari according to the PR-ASK modulation format. Control to output the modulated RF signal. At this time, the output state of the phase shifter 235 and the signal selector 238 is maintained according to the response time of the electronic tag, that is, the pulse width.

The RF transmitter 232 of the RFID reader of the present invention controls the phase shifter 235 and the signal selector 238, and modulates the RF modulated by any one of DSB-ASK, SSB-ASK, and PR-ASK. By outputting a signal, power required by an electronic tag can be transmitted without loss, and communication with the electronic tag can be stably maintained.

The RFID reader according to the present invention can process RF signals using various modulation schemes such as DSB-ASK, SSB-ASK, and PR-ASK and transmit them to an electronic tag, thereby delivering power required by the electronic tag without loss. And, there is an effect that can maintain a stable communication with the electronic tag.

The present invention has been described above with reference to the preferred embodiments, which are merely examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not possible that are not illustrated above. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

According to an embodiment of the present invention, the RFID reader and the RFID system isolate the transmission / reception path of the RF signal from the RFID reader, thereby reducing the error rate of the transmission / reception data and improving the reception sensitivity.

In addition, by arranging a plurality of transmitting and receiving antennas in one RFID reader, the size of the RFID reader can be reduced, and the recognition distance from the electronic tag can be increased.

In addition, it is possible to communicate with the electronic tag by using the RF signal modulated by various modulation methods suitable for the coding format, so that the power required by the electronic tag can be transmitted without loss, and the electronic tag can be stably communicated.

Claims (23)

A plurality of antennas for transmitting and receiving RF signals; A path selector which selects and connects any one of a plurality of antennas and one of a transmission path and a reception path of the RF signal; An RF processor for processing an RF signal transmitted to a transmission path or a reception path selected by the path selection unit; RFID reader including a control unit for controlling the path selection of the path selection unit. A plurality of antennas for transmitting and receiving RF signals; A path selector configured to select one of a transmission path and a reception path of the RF signal; An RF processor for processing an RF signal transmitted to a transmission path or a reception path selected by the path selection unit; A control unit for controlling the path selection of the path selection unit, The plurality of antennas include a first and a second antenna for transmitting and receiving the RF signal at one side of the movement region of the electronic tag, and a third and fourth antennas for transmitting and receiving the RF signal at the other side of the movement region of the electronic tag. A plurality of antennas for transmitting and receiving RF signals; A path selector configured to select one of a transmission path and a reception path of the RF signal; An RF processor for processing an RF signal transmitted to a transmission path or a reception path selected by the path selection unit; A control unit for controlling the path selection of the path selection unit, The path selector includes a first switching unit sequentially connected to a plurality of antennas, and a second switching unit connected to the first switching unit to select a transmission path or a reception path of an RF signal. The method according to any one of claims 1 to 3, And the path selector is sequentially connected to the plurality of antennas. The method according to claim 1 or 3, The plurality of antennas may include: first and second antennas for transmitting and receiving the RF signal at one side of the moving region of the electronic tag; RFID reader including a third and fourth antenna for transmitting and receiving the RF signal at the other side of the moving area of the electronic tag. The method of claim 1, The path selector includes a first switching unit sequentially connected to a plurality of antennas; And a second switching unit connected to the first switching unit and configured to select one of a transmission path and a reception path of the RF signal. The method according to claim 3 or 6, wherein And the path selector comprises a third switch configured to connect a ground terminal or a receive path to a signal input through the second switch in accordance with a transmission mode or a reception mode. The method of claim 7, wherein The RFID reader of the first to third switching unit is implemented by a semiconductor switch element. The method according to any one of claims 1 to 3, The RF processor may include: an RF receiver for suppressing and amplifying a noise signal of an RF signal received through the path selector and demodulating the amplified signal into original data; And an RF transmitter for modulating the transmitted RF signal according to data and outputting the modulated RF signal to the path selector. The method according to any one of claims 1 to 3, And a baseband processor converting the received RF signal of the RF processor into digital data and transmitting the digital signal to the controller, and converting the digital data of the controller into an analog signal. The method of claim 9, The RF transmitter is an RFID reader that operates in any one of the modulation scheme of the encoding processing DSB-ASK, SSB-ASK, PR-ASK selectively. The method of claim 9, The RF transmitter is an RFID reader that satisfies the modulation format of EPC Class 1 or ISO 18000-6 UHF RFID Protocol. The method of claim 9, The RF transmitter includes a PLL unit for generating an RF signal; A phase shifter configured to convert the input RF signal into a first RF signal having a first phase and a second RF signal having a second phase, and to modulate the received RF signal according to data; And a signal selector configured to select and output a first RF signal or a second RF signal modulated by the phase shifter. The method of claim 13, And the phase shifter adjusts the first phase of the first RF signal and the second phase of the second RF signal to have a 180 degree phase difference with each other. The method of claim 13, The pulse width of the RF signal output by the phase shifter and the signal selector has a 0.265 ~ 0.525 Tari. The method of claim 9, The RFID processing unit communicates using a Tari value between 6.25 ~ 25us. The method of claim 15, The pulse width is measured at 50% point on the pulse. A phase shifter configured to convert the input RF signal into a first RF signal having a first phase and a second RF signal having a second phase, and modulate the RF signal according to data; A signal selector configured to select the first RF signal or the second RF signal of the phase shifter according to a modulation scheme; And a controller configured to control a signal output path and a period of the phase shifter and the signal selector according to a coding format. The method of claim 18, The control unit is an RFID reader that operates in any one of the modulation scheme of DSB-ASK, SSB-ASK, PR-ASK selectively. The method of claim 18, And the phase shifter adjusts phases of the first RF signal and the second RF signal by 180 degrees. One or more passive electronic tags; An RFID system comprising a RFID reader having a plurality of antennas and performing communication in different modulation schemes according to the electronic tag and the coding format. The method of claim 21, The RFID reader includes a path selection unit for selectively outputting any one of a transmission path and a reception path of the RF signal. The method of claim 21 or 22, The RFID reader includes an RF transmitter for outputting an RF signal modulated by any one of the modulation scheme of DSB-ASK, SSB-ASK, PR-ASK selectively.

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