KR20010075050A - A contactless capacitive data transmission system and method - Google Patents

Abstract

The contactless capacitive data transmission system utilizes a contactless capacitive data transmission circuit 10 and a corresponding contactless capacitive data reception circuit 70 for electrostatically communicating gap based information. The contactless capacitive data transmission circuit 10 is coupled to an excitation source 12 and electrostatic data coupled to modulate an excitation signal from the excitation source for use as electrostatic transmission data using gaps transmitted as the transmission format. And a generator circuit 14. The contactless capacitive data transmission circuit 10 includes first and second electrostatic antenna elements 16a, 16b coupled to the electrostatic data generation circuit 14. The first and second electrostatic antenna elements 16a, 16b electrostatically modulate the modulated data on a remotely powered electrostatic RFID tag 11 disposed in the vicinity of the non-contact capacitive data receiving circuit 70. Is arranged to transmit.

Description

Contactless capacitive data transmission system and method {A CONTACTLESS CAPACITIVE DATA TRANSMISSION SYSTEM AND METHOD}

<Related application>

This application is filed on February 27, 1998 by Victor Allen Vega et al., Assigned to the applicant of this application, and has an agent control number IND 10153, entitled "Radio Frequency Identification Tag System Using Tags Arranged for Coupling to Ground Is a Continuation-In-Part (CIP) application of US Patent Application No. 09 / 031,848.

The application is also filed on March 12, 1998 by Victor Allen Vega et al., Assigned to the applicant of the present application, and has an agent control number IND 10146, entitled "Radio Frequency Identification Tag Arranged for Magnetically Storing Tag State" Information ", a Continuation-In-Part (CIP) application of US Patent Application No. 09 / 041,480.

In addition, the present application is filed on March 20, 1998 by Victor Allen Vega and assigned to the applicant of the present application, and the agent management number IND 10174, entitled "Radio Frequency Identification Tag with a Programmable Circuit State" Continuation-In-Part (CIP) application of patent application No. 09 / 045,357.

The application is also filed on September 11, 1998 by Victor Allen Vega and John H. Rolin and assigned to the applicant of the present application, and has an agent control number IND 10180, entitled "Method and Apparatus for an Optimized Circuit for Continuation-In-Part (CIP) application of US Patent Application No. 09 / 151,568, entitled "An Electrostatic Radio Frequency Identification Tag."

Remotely powered electronic devices and related systems for programming such devices are known. For example, one type of remotely powered electronic device is a personal identifier and a radio frequency identification (RFID) tag that is often used in automated gate surveillance applications protecting security buildings or areas. Conventional systems require an individual accessing this building to insert or swipe its identification tag into or through the reader of the system to read information from the identification tag. Radio frequency identification (RFID) tags use radio frequency (RF) data transmission technology to conveniently remove information from insertion or swapping by reading information from the radio frequency identification tag over short distances.

Information stored on an RFID tag is typically programmed remotely using a programmer, such as a base station, which transmits an excitation signal to power the radio frequency identifier tag. The base station, or programmer, then transmits the information data to the RFID tag, which programs a storage device such as an electrically erasable programmable ROM (EEPROM), FeRAM, or other memory disposed on the RFID substrate.

Typical techniques for powering and programming radio frequency identification tags are inductive coupling, or a combination of inductive power coupling and capacitive data coupling. One communication system for RFID devices is disclosed in US Pat. No. 5,345,231, entitled “Contactless Inductive Data Transmission System,” filed by Roland Koo et al., Issued September 6, 1994. In such systems, inductive coupling is used, which requires coupling the coil element to the radio frequency tag. The coil element is excited or powered by an excitation signal from the base station to power the radio frequency identifier tag circuit. Once powered, the radio frequency identifier tag can transmit and receive information between the radio frequency identifier tag and the base station using the tag coil. Inductive RFID tags are relatively expensive, especially for applications that may require freely available radio frequency identifier tags, such as inventory management applications, baggage handling applications or other suitable applications. In addition, radio frequency identifier tags that rely on inductive coupling are sensitive to the direction of the radio frequency identifier tag relative to the base station, because the field generated by the excitation signal crosses almost perpendicularly to the coil element for effective coupling. Because you have to. Also, inductively coupled RFID tags are not flexible and can be damaged by printers when printing on tags. In addition, coils on RFID tags can make RFID tags expensive to manufacture.

When writing to RFID tags using known techniques, such as inductive coupling, integrated circuits are used as the standard read / write identification ICs available from Temic North America Inc. of Basking Ridge, New Jersey. It is possible. In such a system, writing data to an RFID integrated circuit (IC) is done by interpreting an RF field with short gaps. Radio frequency pulses between two gaps encode information of one or zero. The first gap is typically a start gap that triggers a write mode in the RFID IC. Gaps are typically created when electromagnetic energy attenuation is permanently possible. This is designed to facilitate gap detection by the decoder circuit disposed in the RFID tag. The duration of the gap is usually 50 to 400 microseconds, for example the time between two gaps is typically 24 field clock for logic "0" and 56 field clock for logic "1". Although such a transmission method may be useful for an electromagnetic based RFID tag system, there is a problem that systems based on new electrostatic RFID data, such as those disclosed in the related pending applications, do not yet have a defined transmission scheme. Therefore, there is a need for a suitable transmission method for new electrostatic-based systems where expensive induction tank coils and resonant capacitors are removed from RFID tags. New electrostatic based contactless systems do not use tank coils in RFID tags to receive electromagnetic energy, but instead use electrostatic plates or other suitable antennas to transmit and receive fields. This reduces manufacturing costs and relaxes manufacturing limitations, making static-based portable communication devices highly desirable for many applications.

As a result, an electrostatic RFID data transmission system comprising a non-contact capacitive transmission circuit and a corresponding non-contact capacitive data receiving circuit, which can make it easy to record information from a base station to a remotely powered electronic identification tag. need.

The present invention relates generally to a contactless data transmission system, such as systems used to transmit data via Radio Frequency Identification (RFID) tags, and more particularly to a contactless capacitive data transmission system. It is about.

1 is a block diagram illustrating one embodiment of a capacitive data transfer circuit in accordance with the present invention;

2 is a graphic representation of a recording protocol based on static electricity generated by the circuit of FIG.

3 is a block diagram according to another embodiment of a capacitive data transfer circuit according to the present invention;

4 illustrates another embodiment of a contactless capacitive data transfer circuit in accordance with the present invention.

5 illustrates an embodiment of a non-contact capacitive data receiving circuit in accordance with the present invention.

6 illustrates another embodiment of the capacitive data transmission and reception circuit according to the present invention.

Briefly, a contactless capacitive data transmission system utilizes a capacitive data transmission circuit and a capacitive data reception circuit correspondingly electrostatically communicating information. Applicant hereby means that "contactless" means that information and / or data is communicated in a manner other than an electrical connection between the data transmission circuit and the data receiving circuit.

The contactless capacitive data transfer circuit includes an excitation source modulated (via suitable ASK, FSK, or PSK technology) for electrostatic data transfer. The contactless capacitive data transmission circuit comprises a first and a first arrangement arranged for electrostatically transmitting the modulated data to an electrostatic radio frequency identification tag located nearby and remotely powered and incorporating a contactless data receiving circuit. 2 includes an electrostatic antenna element.

In operation, the contactless capacitive data communication system receives electrostatically generated data from the contactless capacitive data transmission circuit, and decodes the electrostatically received data so that the received data represents a logic "1". Or a logic "0". If necessary, the system detects a number of received cycles, the frequency of the received cycles, the duration of the electrostatically received data or the phase of the electrostatically received data to determine whether the received data represents a data packet. .

In one embodiment, the contactless capacitive data reception circuit includes first and second electrostatic antenna elements for receiving data electrostatically from the contactless capacitive data transmission circuit. The non-contact capacitive data receiving circuit is connected to the first and second electrostatic antenna elements to decode the electrostatically received data to determine whether the received data represents a logic "1" or a logic "0". Electrostatic data decoder. In one embodiment, the contactless capacitive data transmission system uses demodulated interrupts as short gaps according to a predetermined gap scheme in the RF fields. The decoder detects a field gap in the electrostatically received data, detects data to be programmed into an integrated circuit disposed on a remotely powered electronic identification tag, and determines valid cycles in the electrostatically received data. do. If desired, one of the electrostatic antenna elements can be at ground potential to create a monopole receiver.

1 illustrates one embodiment of a contactless capacitive data transmission circuit 10 for capacitively transmitting data to a contactless portable communication device, such as an electrostatic radio frequency identification (RFID) tag 11. The contactless capacitive data transmission circuit 10 includes an electrostatic data generation circuit 14 coupled to the first and second electrostatic antenna elements 16a, 16b, such as electrostatic plates. The electrostatic data generation circuit 14 includes an excitation source 12, a gap generation circuit 17, and a controller 24. The contactless capacitive data transmission circuit 10 may be used with low cost electrostatic RFID tag systems or other suitable remote powered devices. The contactless capacitive data transmission circuit 10 may be disposed at, for example, a base station. The RFID tag 11 includes a first electrostatic antenna element 25a T1 and a second electrostatic antenna element 25b T2.

The excitation source 12 may be a piezoelectric crystal based excitation source, inductive excitation source, or other suitable excitation source, and oscillate at about 125 kHz or other suitable frequency. The excitation source 12 is an electrostatic data generation circuit 14. Generate an excitation signal 18 to be modulated by. The electrostatic data generating circuit 14 modulates the excitation signal as the electrostatic transmission data 20. In this embodiment, the electrostatic data generation circuit 14 periodically modulates the peak-to-peak voltage level of the excitation signal 18 using the gap generator and the controller 24 to close the gaps between the data bits and the data bits. Is an amplitude modulator to generate. The controller 24 forms data packets electrostatically transmitted between the contactless capacitive data transmission circuit 10 and the electrostatic RFID tag 11 by modulation of the excitation signal 18.

In this embodiment, excitation signal 18 is controlled such that its peak-to-peak voltage levels are modulated periodically between about 100% and 0%. However, it will be appreciated that any suitable amplitude modulation levels may be used. The controller 24 turns on and off the gap generating circuit 17 to write to the start gap followed by a programmable integrated circuit disposed on the remotely powered electrostatic RFID tag 11. Generates data in a data format in which data fields and field gaps alternate as data. The field gap represents the interval between the information detected by the data bits. The gap generating circuit 17 may be a suitable type of attenuation device or switching device that transforms the excitation signal to form a gap between the data bits.

During operation, the isolation impedance isolates the gap generating circuit 17 from the excitation source 12 such that the excitation source 12 is not improperly loaded while the gap generating circuit 17 is in operation. Controller 24, which may be any suitable logic, generates radio frequency enable signal 23 to enable or disable gap generation circuit 17. The gap generating circuit 17 can function as a switch to open the circuit to prevent the signal from being output, or can function as an attenuation device to shunt the excitation signal, thereby generating gaps in the excitation signal 18 to generate a data packet. do.

2, a recording data format 40 for data packets is shown. The write data format 40 generated by the contactless capacitive data transmission circuit 10 is separated by an initial non-attenuated RF field 41 and start gap 42 followed by field gaps 45. Multiple non-damped excitation cycles 44a, 44b. For example, clock cycles that are not attenuated are detected by the electrostatic RFID tag 11 as data representing logic " 0 ". The initial non-attenuated RF field 41 prepares the integrated circuit for the on-board power circuit to charge up. For example, signals 46a and 46b have longer period periods than signals 44a and 44b, include more cycles of excitation signal 18, and are interpreted to represent logic " 1. " It will be appreciated that the logic can be reversed if necessary.

Referring again to FIG. 1, the contactless capacitive data transmission circuit 10 has a pair of antenna plates E1 and E2 that act as balanced out of phase pairs. It will also be appreciated that arrays of antenna plates may also be used, but for simplicity, only two exemplary antenna plates will be described herein. Alternatively, for example, wire antenna electrostatic elements or comb shaped structures may be employed in place of the antenna plates. In addition, one of the antenna plates is removed or coupled to ground to form a monopole arrangement.

If desired, the non-contact capacitive data transmission circuit 10 may include a reader portion (not shown) which may include a single electrostatic reader antenna plate connected to a receiver for providing input signals to the detector. It may include. The I / O processor receives the signal from the detector and converts these signals for evaluation by the processor, for example confirming that the data recorded in the electrostatic RFID tag 11 was successful. The reader can also be used to read identification data stored in the electrostatic RFID tag 11 with, for example, a contactless capacitive transmission circuit coupled as part of the base station.

3 shows another embodiment of a contactless capacitive data transfer circuit 50 employing frequency modulation instead of amplitude modulation. In this embodiment, an excitation source such as the sine wave source 52 outputs an excitation signal to the multiplier 54, which then receives the enable signal 55. The voltage controlled oscillator (VCO) 56 receives the output from the multiplier and receives the frequency control signal 57 to control the frequency of the signal from the VCO 56. The variable frequency output signal 58 functions as an input of the amplifier 59. The amplifier 59 then outputs a variable frequency output signal 58 to the converter 26. Enable signal 55 may be zero such that no output is derived from multiplier 54. If desired, the contactless capacitive data transmission circuit 50 may be used as an amplitude modulator. In addition, phase modulation can also be used.

As another example, FIG. 4 shows an example of a contactless capacitive data transmission circuit composed of a bipole amplitude modulation circuit employing the switching transistor 60 as a gap generator. According to this, the excitation drive signal 61 generated by the controller may be a simple digital pulse in view of the complete attenuation of the excitation signal 18. Accordingly, the digital input data of the transistor 60 changes the amplitude of the excitation signal 18 by turning on the transistor at an appropriate time for shunting the excitation signal, or by changing the duty cycle with respect to the base of the transistor to change the amplitude. Function to change The circuit includes an attenuation resistor 64 (optional) and a resonance capacitor 66 connected in parallel across the secondary coil. The paralleled capacitors are selected to have a signal that resonates with the frequency of the excitation drive signal 61. The static-based data provided to the electrostatic antenna 16a through the top of the secondary coil is balanced so that it is 180 degrees out of phase with the signal provided through the bottom of the secondary coil 16b. As indicated by the arrow, the electrostatic antenna creates a field, which is used to power and record the electrostatic based RFID tag 11. Those skilled in the art will appreciate that the desired voltage levels of the field will depend on factors such as the distance that the transmission circuit powers the device. Also, for example, it will be appreciated that the desired power levels will be in accordance with the frequency emission requirements of the country in which the transmission circuit will be used.

FIG. 5 shows at least the first and second antenna elements 25a, 25b T1, T2 which electrostatically receive data 20, such as the write data format 40 (see FIG. 2), from the non-contact capacitive data transmission circuit. An embodiment of a non-contact capacitive data receiving circuit 70 having a is shown. The non-contact capacitive data receiving circuit 70 includes an electrostatic data decoder 71 coupled to the first and second electrostatic antenna elements 25a, 25b. The electrostatic data decoder 71 decodes the electrostatically received data 20 to determine whether the received data represents a logic "1" or a logic "0".

The electrostatic data decoder 71 includes a clock extraction circuit 72, a level detection circuit 74, a gap detection circuit 76, a cycle counter 78, and a data interpreter 80. The clock extraction circuit 72 functions as an analog-to-digital converter that receives the data 20 and generates a digital clock signal 82 based on each cycle detected in the received signal. Level detection circuitry 74 also receives data 20 and outputs a digital signal 84 representing detected cycles that are above a threshold. The level detection circuit 74 determines valid cycles in the electrostatically received data 20. The gap detection circuit 76 counts the clock signal 82 to determine whether a field gap or start gap is detected. If a gap is detected, gap detection circuit 76 generates a reset signal 86. The RF cycle counter 78 resets upon detecting the reset signal 86. The data interpreter 80 interprets whether the group of previous cycles is logic "1" or logic "0".

If no reset signal is detected, RF cycle counter 78 counts the number of cycles between the gaps and outputs count data 88 to data interpreter 80. Count data is used to determine whether a group of cycles constitutes a logic "1" or a logic "0". Thus, if the data is write data, the cycle counter detects the data to be programmed into the integrated circuit disposed on the RFID tag. Data interpreter 80 is a comparator that detects the duration of each non-attenuated interval between field gaps and determines whether the information is a logic "1" or a logic "0". For example, if count data 88 is within an acceptable range, for example 56, then data interpreter 80 may determine that the information represents a logic " 1. " If the time between the two gaps is, for example, 24 clocks, the data interpreter 80 may determine that the data is logic "0". Also, if necessary, the above-described circuit can be basically overlapped with other electrostatic antenna elements 25b. Information is then output to a controller (not shown), which may be a counter for determining whether the data represents packet data, for example, and also determining the content of the data packet. The controller may be any suitable logic and may be a storage packet and a data packet permitter that determines if the proper format was used. For example, during a write command, the controller can determine whether the data represents the appropriate operational code (op code) data, the appropriate number of bits to be stored as memory data, lock bits, and memory address data and configuration mode data. The configuration mode data may be, for example, data indicating whether the integrated circuit should be in read mode or in write mode, for RFID or for another device, may be the data rate at which the data is communicated, If necessary, it may be another type of mode data. The decoder may also be implemented using digital logic if necessary.

The contactless capacitive data transmission circuit is combined with the contactless capacitive data reception circuit to form a contactless capacitive data transmission system. According to this, the above-described embodiments can be used to non-contactly record data electrostatically coupled from a base station to a tag, for example, to simplify the manufacture of an RFID tag decoder. Those skilled in the art will clearly appreciate other advantages.

Those skilled in the art will appreciate that other variations and modifications in accordance with various aspects of the invention may be implemented and the invention is not limited to the contents described herein. It will be appreciated that any suitable modulation scheme can be used, such as, for example, FSK, PSK or other suitable technique. In addition, the decoders of FIGS. 5 and 6 can be coupled to only one antenna element if necessary, such that a monopole configuration may be used, or a combination of each type of decoder may be used. In addition, a contact programmer can be used to program the RFID during the manufacturing process. Therefore, it is to be understood that the present invention covers all modifications, changes, or equivalents falling within the spirit and scope of the principles and claims disclosed herein.

Claims (25)

In the capacitive data transmission circuit, An excitation source for generating an excitation signal; Electrostatic data generation circuitry coupled to modulate the excitation signal as data for electrostatic transmission; And At least one first antenna element coupled to the electrostatic data generation circuit Including, Wherein said at least one first antenna element is arranged for electrostatically transmitting data to a remotely powered remote frequency identification (RFID) tag located nearby. . 2. The capacitive data transmission circuit as claimed in claim 1, wherein the electrostatic data generation circuit forms data packets which are modulated by at least one of amplitude modulation, frequency modulation and phase modulation to be electrostatically transmitted. 3. The electrostatic data generating circuit of claim 2, wherein the electrostatic data generating circuit comprises an amplitude modulator having a gap generating circuit controlled to periodically modulate the excitation signal to generate gaps between the data bits and the data bits. Capacitive data transmission circuit. 3. The apparatus of claim 2, wherein the electrostatic data generation circuit comprises an amplitude modulator that modulates the excitation signal periodically between about 100% and 0% to generate gaps between data bits and data bits. And at least one op code data and memory address data. 2. The capacitive data transmission circuit of claim 1, wherein the electrostatic data generation circuit comprises a frequency modulator. The data field as claimed in claim 1, wherein the electrostatic data generation circuit is write data for a programmable non-attenuated RF field, a start gap and subsequent programmable integrated circuit disposed on a remotely powered RFID tag. And generating data in a format including field and field gaps. 7. The capacitive data transmission circuit of claim 6, wherein the data fields comprise data representing at least one of opcode data, memory address, memory data, lock bits, and configuration mode data. 2. The capacitive data transmission circuit of claim 1, wherein the at least one first antenna element is an electrostatic plate. The capacitive data transmission circuit according to claim 1, comprising a second electrostatic antenna element. In the capacitive data receiving circuit, At least first and second antenna elements for electrostatically receiving data from the capacitive data transmission circuit; And Electrostatic data coupled to at least one of the first and second antenna elements to decode electrostatically received data to determine whether the received data represents a logic "1" or a logic "0" Decoder Capacitive data receiving circuit comprising a. 12. The gap detection of claim 10, wherein the electrostatic data decoder detects a gap in the electrostatically received data to facilitate determination of whether the received data represents logic "1" or logic "0". And a circuit comprising a circuit. The electrostatic data decoder of claim 10, wherein the electrostatic data decoder is disposed on a remotely powered electrostatic RFID tag, A gap detector coupled to receive the electrostatically received data; A cycle counter coupled to receive the electrostatically received data; And Level Detection Circuit Coupled to Cycle Counter Including, The gap detector detects start gaps and field gaps, the cycle counter detects data to be programmed in an integrated circuit disposed on a remotely powered RFID tag, and the level detection circuit is valid on electrostatically received data. And capacitive data receiving circuitry. 11. The capacitive data receiving circuit according to claim 10, wherein the electrostatic data decoder determines whether the data includes data representing at least one of operation code data, memory address, memory data, and configuration mode data. In the capacitive data transmission system, (a) Capacitive data transmission circuit-this circuit An excitation source for generating an excitation signal; Electrostatic data generation circuitry coupled to modulate the excitation signal as data for electrostatic transmission; And At least one first antenna element coupled to the electrostatic data generation circuit Including, The at least one first antenna element is arranged for electrostatically transmitting data to a remotely powered remote frequency identification (RFID) tag located nearby; And (b) capacitive data receiving circuit-this circuit At least first and second antenna elements for electrostatically receiving data from the capacitive data transmission circuit; And An electrostatic data decoder coupled to the first and second antenna elements to decode electrostatically received data to determine whether the received data represents a logic "1" or a logic "0" Contains- Capacitive data transmission system comprising a. 15. The system of claim 14, wherein said electrostatic data generation circuitry forms data packets that are electrostatically modulated by at least one of amplitude modulation, frequency modulation, and phase modulation. 16. The system of claim 15, wherein said electrostatic data generating circuit comprises an amplitude modulator controlled to periodically modulate said excitation signal to produce gaps between data bits and data bits. . 16. The amplitude modulator of claim 15, wherein the electrostatic data generation circuit has an amplitude modulator with a gap generation circuit that is controlled to modulate the excitation signal periodically between about 100% and 0% to produce gaps between data bits and data bits. Capacitive data transmission system comprising a. 15. The data field as claimed in claim 14, wherein the electrostatic data generating circuit is write data for a programmable non-attenuated RF field, a start gap and subsequent programmable integrated circuit disposed on a remotely powered RFID tag. And generate data in a format including field and field gaps. 15. The system of claim 14, wherein said first and second antenna elements are electrostatic plates. 15. The apparatus of claim 14, wherein the electrostatic data decoder includes a cycle counter that decodes electrostatically received data to determine whether the received data represents a logic "1" or a logic "0". Capacitive data transmission system. 15. The method of claim 14, wherein the electrostatic data decoder is disposed on a remotely powered static RFID tag, A gap detector coupled to receive the electrostatically received data; A cycle counter coupled to receive the electrostatically received data; And A level detection circuit coupled to the cycle counter Including, The gap detector detects start gaps and field gaps, the cycle counter detects data to be programmed in an integrated circuit disposed on a remotely powered RFID tag, and the level detection circuit is valid on electrostatically received data. A capacitive data transfer system, characterized in that for determining cycles. 15. The system of claim 14 including a second capacitive antenna element coupled to the electrostatic data generator. 15. The capacitive data transfer system of claim 14, wherein the capacitive data transfer circuit is contactless. In the capacitive data communication method, Electrostatically receiving data generated from the contactless capacitive data transmission circuit; And Decoding the electrostatically received data to determine whether the received data represents logic "1" or logic "0"; Capacitive data communication method comprising a. The method of claim 24, Detecting a field gap; Detecting data to be programmed into an integrated circuit disposed on the remotely powered electronic identification tag; And Determining valid cycles in the electrostatically received data Capacitive data communication method comprising a.