KR100887853B1 - Radio Frequency IDentification trasmitter/receiver apparatus - Google Patents

Abstract

RFID transmitting and receiving device according to an embodiment includes a receiver for processing a signal received from the antenna; A control unit including a channel coding module for determining a channel bandwidth according to a transmission rate, a filter control module for generating a filter control signal according to the channel bandwidth, and a modulation control module for adjusting a modulation standard of a transmission signal according to the channel bandwidth; A modulation unit for modulating the I transmission signal and the Q transmission signal transmitted from the control unit according to the modulation standard, and the I and Q signals transmitted from the modulation unit at reference intervals based on the frequency band defined by the filter control signal, respectively. And a transmitter including a first filter and a second filter for filtering, and a signal synthesizer for synthesizing the I and Q signals filtered by the first and second filters into a single signal.

According to the embodiment, the interference phenomenon between the RFID channels can be prevented through bandwidth adjustment, carrier signal adjustment according to a modulation standard, Q value adjustment, and the like, and an energy can be smoothly supplied to a tag. In addition, a decrease in reception sensitivity and an increase in signal to noise ratio (SNR) can be prevented.

RFID, Reader, Tag, Pulse-Interval Encoding (PIE), ISO 18000-A, B, Electronic Product Code (EPC), Modulation Index, Q Value

Description

RFID transceiver device {Radio Frequency IDentification trasmitter / receiver apparatus}

An embodiment discloses an RFID transceiver.

Ubiquitous network technology has attracted a lot of attention, and ubiquitous network technology refers to a technology that allows a user to naturally connect to various networks regardless of time and place.

Such a ubiquitous network may be implemented as a short range wireless communication system, for example, an RFID system. The RFID system includes a tag attached to an article and embedded with article information, and a reader for reading the tag information using RF communication.

The tag receives energy by using a signal received from a reader, and since a signal containing data and a signal used as tag energy are transmitted through the same frequency band, supply of energy is not smooth and reception sensitivity is deteriorated.

In addition, since the reader communicates with dozens or hundreds of tags, interference is likely to occur between channels, and nonlinear interference signals caused by excessive peak to average power rating (PAR) adversely affect RFID communication. Brings about.

Conventionally, since the envelope detection standard available for each modulation scheme is not established, it has a different control structure for each system, and there is a difficulty in implementing a standardized RFID transmission system due to the type of modulation scheme and the difference of modulation control criteria.

For example, an RFID transmission system such as a reader targets a tag moving at a high speed, so that the radio wave environment changes severely, and that an RF stage is dependent on the baseband stage because modulation uses the same frequency band. The design of the RFID reader based on the standardized modulation method is considered to be an important aspect due to factors such as signal distortion such as phase inversion, recognition distance, error rate, etc. depending on the separation and synthesis method of the I / Q signal. It is becoming.

The embodiment provides an RFID transceiver that can minimize interference between RFID channels, extend a tag recognition distance, and improve supply of tag energy and a tag recognition rate.

RFID transmitting and receiving device according to an embodiment includes a receiver for processing a signal received from the antenna; A control unit including a channel coding module for determining a channel bandwidth according to a transmission rate, a filter control module for generating a filter control signal according to the channel bandwidth, and a modulation control module for adjusting a modulation standard of a transmission signal according to the channel bandwidth; A modulation unit for modulating the I transmission signal and the Q transmission signal transmitted from the control unit according to the modulation standard, and the I and Q signals transmitted from the modulation unit at reference intervals based on the frequency band defined by the filter control signal, respectively. And a transmitter including a first filter and a second filter for filtering, and a signal synthesizer for synthesizing the I and Q signals filtered by the first and second filters into a single signal.

According to the embodiment, the following effects are obtained.

First, the interference phenomenon between RFID channels can be prevented through bandwidth adjustment, carrier signal adjustment according to modulation standard, and Q value adjustment, and the energy can be supplied smoothly to the tag.

Second, a decrease in reception sensitivity and an increase in signal to noise ratio (SNR) can be prevented.

Third, the modulation depth of the RF signal according to the PIE format can be adjusted for various channels whose bandwidth is adjusted, and the recognition distance of the tag can be precisely adjusted according to the transmission / reception environment.

Fourth, the use channel of the reader can be extended, and there is a wavelength compensation effect according to the distance between the tag and the reader antenna. Therefore, the signal can be processed without canceling the I / Q signal according to the distance.

Fifth, in the RFID / USN system, it is possible to adjust the communication speed and recognition rate, there is an effect that can be implemented a stable system.

An RFID transceiver according to an embodiment will be described with reference to the accompanying drawings. For convenience of description, the RFID transceiver is an RFID reader.

1 is a block diagram schematically illustrating components of an RFID transceiver device 100 according to an embodiment, and FIG. 2 is a graph illustrating a channel bandwidth set according to a transmission speed in an RFID transceiver device 100 according to an embodiment. to be.

Referring to FIG. 1, the RFID transceiver 100 according to the embodiment includes a controller 110, a modulator 120, a first filter 122, a second filter 124, a first mixer 134, and a second. The mixer 136, the signal synthesizer 140, the fifth filter 145, the first PA 150, the transmit antenna 102, the receive antenna 101, and a low noise amplifier (LNA) 155, the sixth filter 160, the signal distribution unit 165, the third mixer 172, the fourth mixer 174, the third filter 182, the fourth filter 186, and the second PA 192. ), A third PA 194, a demodulator 196, a phase locked loop (PLL) 130, a first signal separator 132, and a second signal separator 170.

In addition, the control unit includes a channel coding module 111, a modulation control module 112, a filter control module 113, a slot control module 114, a PLL (Phase Locked Loop) control module 115.

The channel coding module 111 determines a channel bandwidth according to a transmission rate (data rate), and the channel bandwidth may be calculated by the following equation (1).

Channel Bandwidth = Data Rate × Coding Rate × Sideband Filter Rate × 1.25

For example, assuming that the transmission rate is 40 kbps, since the encoding rate is 2 / bit, and the sideband filter rate is 2 in the case of DSB (Double SideBand), the channel bandwidth is calculated as 200 KHz.

This is as illustrated in Figure 2 (a).

In addition, when the transmission rate is 120 KHz, the channel bandwidth is calculated as 600 KHz, and when the transmission rate is 640 KHz, the channel bandwidth is calculated as 3200 KHz.

This is as illustrated in (b) and (c) of FIG. 2, respectively.

For reference, in the case of SSB (Single SideBand), the sideband filter ratio is 1.

When the transmission rate is 40 kbps (KHz) and 120 kbps, the frequency channel of the 900 MHz band can be allocated as shown in Table 1 below.

Channel number (40 kbps) frequency band (120 kbps) frequency band 1 FA 910.8 MHz 910.8 MHz 2 FA 911.0 MHz 911.4 MHz 3 FA 911.2 MHz 912.0 MHz 4 FA 911.4 MHz 912.6 MHz 5 FA 911.6 MHz 913.2 MHz 6 FA 911.8 MHz 913.8 MHz 7 FA 912.0 MHz 914.4 MHz 8 FA 912.2 MHz 915.0 MHz 9 FA 912.4 MHz 915.6 MHz 10 FA 912.6 MHz 11 FA 912.8 MHz 12 FA 913.0 MHz 13 FA 913.2 MHz 14 FA 913.4 MHz 15 FA 913.6 MHz 16 FA 913.8 MHz

The channel coding module 111 may be provided with an interface means (not shown) to receive a transmission rate value desired by an administrator.

3 is a graph illustrating a channel region when the transmission rate is 120 kbps in the RFID transceiver 100 according to the embodiment.

The filter control module 113 generates a filter control signal according to the determination of the channel bandwidth, and generates the filter control signal using the first filter 122, the second filter 124, the third filter 182, and the fourth filter ( 186) respectively.

The first filter 122 to the fourth filter 186 may be provided as a variable filter, for example, a voltage control filter in which a pass frequency characteristic is changed by voltage control.

When the transmission signal is transmitted from the modulator 120, the first filter 122 and the second filter 124 filter the frequency band defined by the filter control signal at a reference interval as shown in FIG. 2.

In addition, when the received signal is transmitted from the third mixer 172 and the fourth mixer 174, the third filter 182 and the fourth filter 186 are defined by the filter control signal as shown in FIG. 2. Filter by band as the reference interval.

Referring to FIG. 3, the first filter 122 to the fourth filter 186 perform the variable filtering function as described above, and thus correspond to a predetermined channel bandwidth f3 + f4 based on the center frequency f1. Only a transmission signal or a reception signal is passed, and an area f2 of an interference signal such as a spurious signal may be blocked.

When the channel bandwidth is set by the channel coding module 111, the modulation control module 112 adjusts the carrier signal by changing the modulation index and signal timing specification of each channel for which the bandwidth is set.

As such, by adjusting the carrier signal, the recognition distance of the tag can be controlled and the interference phenomenon between the channels can be eliminated as much as possible.

The function of the modulation control module 112 will be described in detail together with the modulator 120.

Meanwhile, the RFID channel is divided at predetermined time intervals, and the reader performs an iterative identification process to identify the tag. In this way, a channel divided based on the time axis is called a time slot, and a repetitive identification process of a tag is performed based on the time slot. That is, the communication period in which the command and response between the reader and the tag are processed is based on the time slot.

The reader assigns a series of slot numbers to the recognized tags, and the tags initiate communication with the reader when the slot number assigned to the tag matches the progress slot number.

The slot control module 114 includes a slot ounter (not shown) for managing time slots, and the slot counter controls time slot parameters, that is, Q values, to control communication with the tags. .

Since a plurality of tags are allocated channels of different bandwidths and time slots should be set on the allocated channels, the slot control module 114 adjusts the Q value after the channel coding module 111 is operated.

That is, the channel coding module 111 initializes the Q value and assigns a new Q value to tags newly assigned a channel.

4 is a diagram illustrating a timing standard among EPC (Electronic Product Code) standards used in the RFID transceiver 100 according to the embodiment.

Among the timing diagrams, a timing diagram corresponding to the reader signal is shown at the upper side, and a timing diagram corresponding to the tag signal is shown at the lower side.

The command response interval shown in FIG. 4 is performed on one time slot, and the modulation control module 112 performs a function of synchronizing a carrier signal with the timing standard.

The timing specifications are briefly described in Table 2 below.

Interval, command, response type Explanation Ready state Tag can communicate without losing energy Select command Select tags to be added to or deleted from the inventory CW (Continuous Wave) section Correspondence section of tag signal 4th time interval (T4) Minimum spacing between reader commands Arbitrate Status When tag and reader are connected together without tag response Query command Command to send response request signal to tag selected for communication First time interval (T1) The time when communication authority is transferred from the reader to the tag Third time interval (T3) Reader's wait time for response request signal QueryRep command In case of no reply, the command to decrease the reader slot value and resend the response request signal. Reply Status Tag sends response code to reader Second time interval (T2) The time the tag is reserved to demodulate the reader signal RN16 (16-bit random or pseudo-random number) Tag's response code Acknowledgment status As the response code of the tag is transmitted, the reader transmits it and the tag information is transmitted. ACK command Verification code for tag response PC (Protocol Control) bits Information about the physical layer of tag information Electronic Product Code (EPC) bits Tag device information for identification Cyclic Redundancy Check (CRC16) Error Detection Information Open state After a tag is recognized, a series of commands and responses are processed to deliver tag information. Req_RN command Command sent to tag to deliver new RN16 Handle command Command to process new command / response structure after Req_RN command

 The slot control module 114 may configure the transmission signal by including the adjusted Q value in command data, such as command data such as a "query command" and a "QueryRep command".

The PLL control module 115 transmits a control signal to the phase synchronization circuit 130 to generate an oscillation signal synchronized with the bandwidth set by the channel coding module 111.

Accordingly, the RF signal mixed in the first mixer 134 and the second mixer 136 or the baseband signal mixed in the third mixer 172 and the fourth mixer 174 may satisfy the newly set channel bandwidth specification. Will be.

The controller 110 may be implemented using a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit.

The digital signal processed by the controller 110 is separated into two signals of quadrature components such as an in-phase (I) signal and a quadrature-phase (Q) signal, and its magnitude is expressed as a phase function.

The transmission signal of the I signal and the Q signal is transmitted to the modulator 120, and the modulator 120 modulates the transmission signal to transmit the I signal to the first filter 122, and the Q signal to the second filter ( 124).

The modulator 120 includes a D / A converter, a modulation circuit, and the like to modulate the digital signal into a baseband signal.

The modulation control module 112 transmits a control signal for modulation index, phase adjustment, and selection timing of the RF signal to the modulator 120 according to a pulse-interval encoding (PIE) format.

The PIE format may be applied according to UHF RFID Protocol such as ISO 18000-A, ISO 18000-B, Electronic Product Code (EPC) Generation-0, EPC Generation-1, and EPC Generation-2. The example assumes that the EPC Generation-2 protocol is used.

As the modulation standard is applied, the RFID transceiver 100 according to the embodiment has a double sideband-amplitude shift keying (DSB-ASK), a single sideband-amplitude shift keying (SSB-ASK), and phase reversal-amplitude (PR-ASK). Shift demodulation method such as Shift Keying can be used.

5 is a graph illustrating an envelope and a modulation index form of an RF signal modulated by the RFID transceiver 100 according to the embodiment.

FIG. 5 (a) is a graph illustrating an envelope form A of an RF signal detected in the DSB-ASK or SSB-ASK modulation scheme, in which reference numeral "B" and "C" denote the Means the modulation index region.

The modulation index indicates the degree to which the numerical values such as frequency, phase width, and phase change by the modulated signal, means the maximum phase shift (in radians) in the phase modulated wave, and the maximum frequency shift in the frequency modulated wave ( I) divided by the frequency of the modulated signal.

For example, the modulation index can be calculated by a formula of "(B-C) ÷ (B + C)".

FIG. 5B is a graph illustrating the envelope form of the RF signal detected in the case of the PR-ASK modulation scheme, in which the designation code "D" and the designation code "F" are divided into orthogonal component signals. Means the area of.

In addition, the symbol "E" denotes a section in which the quadrature component signal is phase shifted, the symbol "G" denotes the maximum electric field magnitude of the envelope, and the symbol "H" denotes between the rising and falling of the envelope. It means a section.

Here, the modulation depth is calculated as "(B-C) / B" in the case of Fig. 5A, and is calculated as "(G-H) / G" in the case of Fig. 5B.

The modulation unit 120 affects the impedance of the transmission signal as the modulation index is adjusted so that the modulation depth of the PIE signal standard is adjusted. As the modulation depth is adjusted, the response characteristic of the tag is changed so that the recognition range (Detector range) ) Can be increased or decreased linearly. That is, according to the embodiment, linear control of the tag recognition distance is possible by controlling the modulation index.

The modulator 120 may adjust the modulation depth by adjusting a reflection coefficient of a recessed region of the envelope, that is, a section in which signal processing is turned off, and the recognition distance is increased when the envelope of the recessed region extends to the outside. Increases.

FIG. 6 is a data structure diagram illustrating a graph measuring a digital signal waveform processed by the modulator 120 of the RFID transceiver 100 and a symbol of a PIE format.

6A and FIG. 5A, the modulation depths are adjusted so that the digital signal envelopes are not damaged ("1", "2", "3"). , The portion labeled "4").

In addition, referring to FIG. 6B, a symbol "Tari" is displayed, and "Tari" means a reference time interval of a signal transmitted to a tag, and a numerical value of 6.25 μs to 25 μs. Has The symbol " PW " means a pulse width of the selection section of the quadrature component signal, and the pulse width is preferably located at about 50% of the RF modulation signal pulse. The operation of adjusting the modulation depth should be at least in the pulse width region.

FIG. 7 is a data table defining graphs and parameters showing RF signal envelope shapes of the PR-ASK modulation standard used in the RFID transceiver 100 according to the embodiment.

The PR-ASK modulation standard shown in (a) of FIG. 7 shows an enlarged reference section (valid regions of the envelope) of the quadrature signal whose modulation depth is adjusted, and the symbols shown in the graph are shown in FIG. b) as defined in the drawing.

In the graph of FIG. 7, the x axis means the time axis and the y axis means the electric field strength axis.

The modulation control module 112 adjusts the modulation index according to the envelope value during the pulse width (PW) section, that is, 0.265 Tari to 0.525 Tari (μs) according to the PR-ASK modulation format.

The first filter 122 and the second filter 124 filter the I signal and the Q signal transmitted from the modulator 120 according to the channel bandwidth, respectively, and the filtered I signal and the Q signal are the first mixer 134. ) And the second mixer 136.

As described above, the phase synchronization circuit 130 generates an oscillation frequency signal under the control of the PLL control module 115, and the oscillation frequency signal is the first signal separation unit 132 and the second signal separation unit 170. Is delivered to.

The oscillation frequency signal is generated as a series of 900 MHz band signal according to the channel bandwidth, as shown in Table 2.

The first signal separator 132 and the second signal separator 170 separate the phase of the oscillation frequency signal into a I signal state and a Q signal state, and may be implemented as, for example, a balloon circuit. .

The first signal separator 132 transmits the oscillation frequency signal in the I signal state to the first mixer 134 and the oscillation frequency signal in the Q signal state to the second mixer 136.

The first mixer 134 mixes the modulated baseband I signal with the oscillation frequency I signal and converts the modulated baseband I signal into an RF I signal, and the second mixer 136 mixes the modulated baseband Q signal with the oscillation frequency Q signal. Convert to RF Q signal.

The signal synthesizing unit 140 synthesizes the RF I signal and the RF Q signal into one RF signal, and the fifth filter 145 filters the noise component generated during the mixing and synthesis process.

The first PA 150 amplifies the filtered RF transmission signal to a transmittable power level, and the amplified transmission signal is transmitted to the tag through the transmission antenna 102.

On the other hand, the RF received signal received through the receiving antenna 101 is transmitted to the low noise amplifier 155, the low noise amplifier 155 amplifies the received signal at a power level that can be processed as a baseband signal while suppressing noise components as much as possible .

The signal distribution unit 165 is a kind of distribution circuit. The signal distribution unit 165 divides the RF reception signal into two signals having the same power size and transfers the RF signal to the third mixer 172 and the fourth mixer 174, respectively.

The second signal separator 170 performs a function similar to that of the first signal separator 132, and transmits the oscillation frequency I signal and the oscillation frequency Q signal to the third mixer 172 and the fourth mixer 174, respectively. To pass.

The third mixer 172 mixes the RF reception signal with the oscillation frequency I signal and converts it into a baseband I signal, and the fourth mixer 174 mixes the RF reception signal with the oscillation frequency Q signal and converts it into a baseband Q signal. Convert.

The third filter 182 and the fourth filter 186 respectively filter the baseband I signal and the baseband Q signal to remove noise components generated during the mixing process.

The second PA 192 and the third PA 194 amplify the baseband I signal and the baseband Q signal, respectively, and the demodulator 196 converts the amplified baseband I signal and the baseband Q signal into a digital I signal, respectively. Demodulate with a digital Q signal.

The demodulated digital I signal and digital Q signal are transmitted to the controller 110 and interpreted as a tag signal.

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.

1 is a block diagram schematically showing the components of an RFID transceiver device according to an embodiment;

2 is a graph illustrating a channel bandwidth set according to a transmission speed in an RFID transceiver device according to an embodiment.

3 is a graph illustrating a channel region when the transmission rate is 120 kbps in the RFID transceiver device according to the embodiment.

4 is a diagram illustrating a timing standard among EPC (Electronic Product Code) standards used in an RFID transceiver device according to an embodiment.

5 is a graph illustrating an envelope and a modulation index form of a modulated RF signal in an RFID transceiver device according to an embodiment.

6 is a data structure diagram showing a graph measuring a digital signal waveform processed by a modulator of an RFID transceiver device and a symbol of a PIE format according to an embodiment.

FIG. 7 is a data table defining graphs and parameters illustrating RF signal envelope shapes of a PR-ASK modulation standard used in an RFID transceiver device according to an embodiment. FIG.

Claims (13)

A receiver for processing a signal received from an antenna; A control unit including a channel coding module for determining a channel bandwidth according to a transmission rate, a filter control module for generating a filter control signal according to the channel bandwidth, and a modulation control module for adjusting a modulation standard of a transmission signal according to the channel bandwidth; A modulation unit for modulating the I transmission signal and the Q transmission signal transmitted from the control unit according to the modulation standard, and the I transmission signal and the Q transmission signal transmitted from the modulation unit based on the frequency band defined by the filter control signal. A transmitter comprising a first filter and a second filter for filtering the signal; and a signal synthesizer for synthesizing the I and Q transmitted signals filtered by the first and second filters into a single signal; RFID transceiver device comprising a. delete The method of claim 1, wherein the channel coding module RFID transmission / reception apparatus for determining the channel bandwidth according to the formula " transmission rate × encoding rate × sideband filter rate × 1.25 " The method of claim 1, wherein the first filter and the second filter RFID transceiver device that is a variable filter. The method of claim 1, wherein the modulation control module RFID transmitting and receiving device for generating a control signal for one or more of the modulation index, phase adjustment, signal timing standard and transmitting to the modulator. The method of claim 1, wherein the modulator RFID processing a transmission signal using any one of DSB-ASK (Double SideBand-Amplitude Shift Keying), SSB-ASK (Single SideBand-Amplitude Shift Keying), and PR-ASK (Phase Reversal-Amplitude Shift Keying) Transceiver. 6. The method of claim 5, wherein at least one of modulation index, phase adjustment, signal timing specification is An RFID transceiver device using a pulse-interval encoding (PIE) format according to any one of the UHF RFID protocols of ISO 18000-6A, ISO 18000-6B, and ISO 18000-6C. The method of claim 1, The receiving unit, A phase synchronizing circuit for generating an oscillation frequency signal, a first signal separation unit for separating the oscillation frequency signal into an I signal and a Q signal, and the oscillation frequency I signal and the first filter separated from the first signal separation unit A first mixer for generating an RF I signal by mixing the filtered I signal and the oscillation frequency Q signal separated by the first signal separator and the Q signal filtered by the second filter to mix the RF Q signal Contains a second mixer to create, The control unit includes a PLL control module for transmitting a control signal to the phase synchronization circuit to generate an oscillation frequency signal synchronized with the channel bandwidth. The method of claim 8, The receiving unit, A signal distribution unit for dividing the power of the received signal into two signals; A second signal separator for separating the oscillation frequency signal into an I signal and a Q signal; A third mixer which generates a mixed I signal by mixing the oscillation frequency I signal of the second signal separator and the branched reception signal; And a fourth mixer configured to generate the mixed Q signal by mixing the oscillation frequency Q signal of the second signal separator and the other branched reception signal. The method of claim 9, At least one of the first signal separator and the second signal separator comprises a balloon circuit. The method of claim 9, The receiving unit, A third filter and a fourth filter respectively filtering the mixed I and Q signals at reference intervals through the frequency band defined by the filter control signal; And a demodulator for demodulating the I and Q signals filtered by the third and fourth filters into digital signals and transmitting the demodulated signals to the controller. The method of claim 11, wherein the third filter and the fourth filter RFID transceiver device that is a variable filter. The method of claim 1, wherein the control unit And a slot control module for adjusting a time slot parameter, generating command data reflecting the adjusted time slot parameter, and transmitting a transmission signal including the command data to the modulator.

Images