KR20060011241A - Afe circuit and rfid interrogator using the same - Google Patents

Abstract

An AFE circuit of an RFID reader and an RFID reader using the same are disclosed. The AFE circuit of the RFID reader according to the present invention is a modulator for modulating the input data into 100% ASK or 10% ASK in response to a selection signal for selecting 100% ASK or 10% ASK mode. An antenna driver for transmitting to the fender, and a receiver for demodulating data received from the transponder.

RFID Reader, AFE, ASK, Transponder, Modulation, Demodulation, Clock

Description

AFF circuit of RFID reader and RF reader using it {AFE circuit and RFID interrogator using the same}

1 is a block diagram schematically showing an RFID reader according to the present invention;

FIG. 2 is a diagram illustrating an example of a modulator and an antenna driver of the RFID reader of FIG. 1;

3 shows an example of a circuit for modulating the duty of a clock signal and a modulated duty waveform;

4 shows the simulated wavelengths of input data and output voltage in 100% ASK mode and 10% ASK mode, and

5 is a view schematically showing a receiver of the RFID reader of FIG. 1.

          Explanation of symbols on the main parts of the drawings

10: digital controller 20: AFE circuit

21 modulator 23 antenna driver

25: Demodulator 26: Level Shifter

27: low pass filter 28: amplifier

The present invention relates to an analog front-end (AFE) circuit of a single chipset for a radio frequency identification (RFID) reader and an RFID reader using the same. More specifically, the present invention relates to Type A and Type B of ISO / IEC 14443, ISO15693. The present invention relates to an AFE circuit of a single chipset for an RFID reader supporting both Mode 1 and ISO 18000-3, and an RFID reader using the same.

RFID technology currently applied to contactless IC cards has attracted much attention in a variety of applications, including e-commerce, credit cards, mobile phones, personal digital assistants (PDAs), ID tags, and transportation cards.

RFID is a technology that incorporates the use of electromagnetic or electrostatic coupling within the radio frequencies of the electromagnetic spectrum to identify objects, animals or humans. RFID is increasingly being used in the industry as a technology to replace barcodes. The advantage of RFID is that there is no need for direct contact or scanning over the visible band. An RFID system consists of three elements: an antenna, a transceiver (commonly integrated into a reader), and a tag, also called a transponder.

The antenna uses radio frequency propagation to carry a signal to activate the transponder. When the transponder is activated, the transponder transmits the data it has to the antenna. This data is usually passed to a programmable logic controller (PLC) where some processing takes place, ranging from something as simple as passing through a statement to something as complex as a database-driven sales transaction. Included. Low frequency RFID systems (30 kHz to 500 kHz) are used in short transmission ranges of about 1.8 m or less, while high frequency RFID systems (850 MHz to 950 MHz and 2.4 GHz to 2.5 GHz) provide long range transmission capability of 27 m or more.

International standards for 13.56 MHz RFID include Type A and Type B of ISO14443, ISO15693, and ISO18000-3. Table 1 compares the key parameters between the 13.56 MHz RFID reader and transponder of these standards.

ISO standard 14443 Type A 14443 Type B 15693 18000-3Mode1 Carrier Frequency (Reader → Tag) 13.56 MHz ± 7KHz Modulation method (Reader → tag) 100% ASK 10% ASK Reader chooses between 100% ASK and 10% ASK Coding (Reader → Tag) Crystal miller NRZ  Pulse position modulation Transmission rate (tag → reader) 106K 106K 1.65K or 26.5K Subcarrier frequency (tag → reader) 847 KHz (fc / 16) 847 KHz (fc / 16) 1 Carrier: 423.75K (fs1) 2 Carrier: fs1, 484.28K (fs2) Load Modulation (Tag → Reader) Manchester Coding BPSK 1 subcarrier or 2 subcarrier Manchester coding

ISO14443 is an interface standard between RFID transponders and readers in proximity of within 10cm. The reader uses a transmission frequency of 13.56 MHz, the Industrial Scientific Medical (ISM) frequency band, to transmit power and data. On a Type A interface, the reader uses 100% Amplitude Shift Keying (ASK) modulated data encoded by a modified Miller method. In a type B interface, a 10% ASK modulated signal of NRZ coded bits is sent to the transponder. The transponder uses a sub transmission frequency of 847 KHz, which is FC / 16. The transmit and receive bit rate is 106 Kbps, which is FC / 128. In the Type A interface, the transponder modulates data with Manchester coding, while in the Type B interface, BPSK modulation is performed on the subcarriers.

ISO15693 is intended for proximity cards and can be operated up to 1 meter away. ISO18000-3 is a new standard and the physical layer is compatible with ISO15693. In ISO15693 and ISO18000-3 mode 1, the tag responds to the reader with a subcarrier modulated Manchester code using one subcarrier or two subcarrier modes.

The inductively coupled loop antennas of the reader and transponder form a transformer, which can transmit data by a load modulation scheme that switches its load at a sub-transmission frequency.

However, since the international standard for 13.56 MHz RFID is subdivided as described above, the RFID reader should be provided with corresponding Analog Front-End (AFE) circuits according to the respective specification conditions, and ISO14443 Type A and Type B, ISO15693 There is a problem in that both, and ISO18000-3 mode 1 cannot be met.

The present invention has been made to solve the above problems, RFID reader supporting both ISO / IEC 14443 Type A and Type B, ISO 15693, and ISO 18000-3 Mode 1, which is an international standard for 13.56MHz RFID It is an object of the present invention to provide a single chipset AFE circuit.

The AFE circuit of the RFID reader according to the present invention for achieving the above object, the input data corresponding to the selection signal for selecting the first ASK (Amplitude Shift Keying) or the second ASK mode of the first percent A modulator for modulating with an ASK or a second percentage of ASK, an antenna driver for transmitting the input data modulated by the modulator to a transponder, and a receiver for demodulating data received from the transponder Characterized in that.

Preferably, the modulator modulates the input data to 100% ASK or 10% ASK in response to the selection signal for selecting the 100% ASK or 10% ASK mode.

Preferably, the modulator is 100% of the input data by the operation of the clock signal having a duty of 50% and at least one logic gate and MUX if the selection signal is high (high) Modulate with ASK.

Preferably, the modulator selects a clock mud signal when the input data value is low when the selection signal is low, and selects the clock signal when the input data value is high.

Preferably, the clock mud signal delays the clock signal by a predetermined time and generates an AND operation on the delayed clock signal and the original clock signal.

On the other hand, the AFE circuit of the RFID reader according to the present invention, the input data to the first percent ASK or the second percent ASK in response to the selection signal for selecting the first percent ASK or the second percent ASK mode. An AFE circuitry comprising a modulator to modulate, an antenna driver to transmit the input data modulated by the modulator to a transponder, and a receiver to demodulate data received from the transponder; And a digital controller providing the selection signal, the input data, and the clock signal to the AFE circuit, and receiving the demodulated data from the receiver.

Hereinafter, with reference to the accompanying drawings will be described in detail the AFE circuit and RFID reader using the RFID reader according to the present invention.

1 is a block diagram schematically showing an RFID reader according to the present invention. Referring to the drawings, the RFID reader is largely composed of a digital controller 10 and an analog front-end (AFE) circuit 20. Here, the AFE circuit 20 includes a modulator 21, an antenna driver 23, and a receiver. In the figure, the receiver is subdivided into a demodulator 25, a low pass filter (LPF) 26, a level shifter 27, and an amplifier 28.

The digital controller 10 controls the RFID reader as a whole, and selects 100% ASK or 10% ASK mode for the AFE circuitry 20, input data DIN, and a clock signal CLK of 13.56 MHz. To provide. Here, the input data DIN is data to be transmitted to the transponder, and is modified Miller code data in type A, and non-return to zero (NRZ) code data in type B.

The modulator 21 modulates the input data DIN into 100% ASK or 10% ASK in response to the selection signal for selecting the 100% ASK or 10% ASK mode.

In addition, the antenna driver 23 performs an operation on the carrier to transmit the input data DIN modulated by the modulator 21 to the transponder. As shown in FIG. 2, the modulator 21 and the antenna driver 23 may be implemented by a combination of an AND gate, a NOR gate, an OR gate, and a mux, and an inverter formed by MP and MN.

For example, if the selection signal transmitted from the digital controller 10 is high, the modulator 21 may include a clock signal having a duty of 50%, an AND gate, an OR gate, a NOR gate, and a mux. By modulating the input data DIN to 100% ASK. The inverter formed by the MP and MN drives the Tx node with 100% ASK modulation pulses. At this time, the high frequency harmonics of the Tx node rectangular pulses are removed by the EMC filter 30 in the external antenna portion.

When the selection signal transmitted from the digital controller 10 is low, the modulator 20 selects the clock mud CLK_MOD signal when the input data DIN value is low, and when the input data DIN value is high. Select the clock signal at. Here, the clock mud CLK_MOD signal may be generated by delaying the clock signal for a predetermined time and ANDing the delayed clock signal and the original clock signal as shown in FIG. 3. At this time, the clock signal CLK is delayed by a delay line circuit, and the delay time is controlled by the signal S.

Here, the Fourier coefficients of the 13.56 MHz frequency component can be selected by changing the duty of the clock applied to Tx. According to the SPICE simulation, when the duty cycle was set at 28%, 20%, and 14%, respectively, it was confirmed that the antenna outputs a modulated ASK value of 10%, 20%, and 30%, respectively. The simulated wavelengths of input data and output voltage at the antenna for the 100% ASK mode and the 10% ASK mode are shown in FIG. 4.                     

5 shows a circuit of a receiver of an AFE circuit. The basic function of the reception circuit is to demodulate the load modulated data received from the transponder by the demodulator 25. The demodulator 25 reproduces the subcarrier modulated pulse signal Rx_out to the digital controller 10. give. Complete binary data is generated in the digital controller 10. The voltage level at the Rx input is adjusted by the voltage divider formed by R _XL1 and R _XL2 and an offset voltage is added by the clamp circuit to shift the negative level signal to 0V. The maximum amplitude of the antenna signal is greater than 30 V. The main purpose of the voltage divider is to protect the mixer from high voltage signals coming from the antenna. The ratio of the voltage divider is about 1/5. Because this circuit uses only one voltage source VDD, the negative input signal is not accepted in the circuit. A mixer composed of CMOS transmission gates synchronizes the carrier of the Rx signal with the clock signal by multiplying the clock signal with the input RF signal. The DC offset level at the mixer output is adjusted to VDD / 2 in the level adjustment circuit 26 before being passed to the filter and comparator.

The low pass filter 27 of the receiver removes high frequency noise, and the cutoff frequency is approximately 800 KHz. A high pass filter with a cutoff frequency of about 1.6 MHz formed by C5, R10 and R11 is used to remove low frequency noise. Since the intermediate band gain of the low pass filter 27 is about 10 and the gain of the inverting amplifier 28 composed of R11 and R12 is about 10, the total gain of the receiving circuit is about 100. Schmitt triggers were used for the comparator 28.

According to the present invention, the AFE circuit of the RFID reader and the RFID reader using the RFID reader can support all of the international standards ISO / IEC 14443 Type A and Type B, ISO 15693, and ISO 18000-3 Mode 1 for 13.56 MHz RFID. Therefore, it is possible to increase the convenience of the user and to solve the conventional hassles that had to be provided with each RFID reader.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone of ordinary skill in the art can make various modifications, as well as such changes are within the scope of the claims.

Claims (10)

A modulator for modulating input data into the first percent ASK or the second percent ASK in response to a selection signal for selecting a first percent ASK (Amplitude Shift Keying) or a second percent ASK mode; An antenna driver for transmitting the input data modulated by the modulator to a transponder; And And a receiver for demodulating data received from the transponder. The method of claim 1, And the modulator modulates input data into 100% ASK or 10% ASK in response to a selection signal for selecting a 100% ASK or 10% ASK mode. The method of claim 2, wherein the modulator, When the selection signal is high, the input signal is modulated to 100% ASK by operation of a clock signal having a duty of 50% and at least one logic gate and a mux. AFE circuitry of RFID reader. The method of claim 2, wherein the modulator, And if the selection signal is low, selects a clock mud signal when the input data value is low, and selects a clock signal when the input data value is high. The method of claim 4, wherein The clock mud signal delays the clock signal by a predetermined time, and generates the AND signal by performing an AND operation on the delayed clock signal and the original clock signal. A modulator for modulating input data into the first percent ASK or the second percent ASK in response to a selection signal for selecting a first percent ASK or a second percent ASK mode, the input data modulated by the modulator An AFE circuitry having an antenna driver for transmitting to a transponder, and a receiver for demodulating data received from the transponder; And And a digital controller for providing said selection signal, said input data, and a clock signal to said AFE circuitry and receiving said demodulated data from said receiver. The method of claim 6, And the modulator modulates the input data into 100% ASK or 10% ASK in response to a selection signal for selecting 100% ASK or 10% ASK mode. The method of claim 7, wherein the modulator, And if the selection signal is high, modulate the input data to 100% ASK by operation of the clock signal having a duty of 50%, at least one logic gate and a inktm. The method of claim 7, wherein When the selection signal is low, selects a clock mud signal when the input data value is low, and selects a clock signal when the input data value is high. The method of claim 9, The clock mud signal delays the clock signal by a predetermined time, and generates the AND by performing an AND operation on the delayed clock signal and the original clock signal.

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