WO2008140156A1

WO2008140156A1 - Rf reader capable of detecting rf signal and existence of rf card and the method thereof

Info

Publication number: WO2008140156A1
Application number: PCT/KR2007/004561
Authority: WO
Inventors: Sung Wan Kim; Pheong Han Lee; Sung Hun Chun
Original assignee: 3Alogics Co., Ltd.
Priority date: 2007-05-16
Filing date: 2007-09-19
Publication date: 2008-11-20
Also published as: KR100796011B1

Abstract

A radio frequency (RF) reader capable of detecting an RF signal and existence or non-existence of a non-contact card, and method of detecting the RF signal and existence or non-existence of a non-contact card are provided. The RF reader includes a card detection pulse signal generation unit for generating a card detection pulse signal via an antenna; a rectifying unit for receiving at least one of a card detection reflection signal and an RF signal, shifting a level of the at least one signal, and rectifying the level-shifted signal; and a comparator for comparing an output signal of the rectifying unit with at least one reference signal and outputting a result of the comparison as a card detection signal or an RF detection signal. Accordingly, the RF signal, which serves as an obstacle of data communications between RF readers, is detected so as to prevent distortion of data. In addition, existence or non-existence of the non-contact card is easily detected so as to reduce consumption of unnecessary power.

Description

RF READER CAPABLE OF DETECTING RF SIGNAL AND EXISTENCE OF RF CARD AND THE METHOD THEREOF

Technical Field

[1] The present invention relates to a radio frequency (RF) reader, and more particularly, to an RF reader capable of detecting an RF signal or existence or non- existence of a non-contact card and a method of detecting the RF signal or existence or non-existence of the non-contact card. Background Art

[2] Typically, radio frequency identification (RFID) systems may be classified into inductively coupled systems and electromagnetic wave systems according to a wireless connection method. The inductively coupled systems are used in short-distance (within Im) RFID systems. In the inductively coupled systems, an RF signal receiver (for example, a reader) and an RF signal transmitter (for example, an RF tag) perform wireless communications by using a coil antenna.

[3] Inductively coupled RF tags are manipulated almost manually. In other words, energy required for IC chips of RF tags to operate are all supplied by a reader. Accordingly, an antenna coil of the reader generates a strong magnetic field around the antenna coil. The magnetic field emitted by the antenna coil generates an inductive voltage in a coil antenna of an RF tag separated from the reader. The inductive voltage is rectified and then supplied as energy for an IC chip.

[4] The electromagnetic wave systems are used in middle long-distance RFID systems.

In the electromagnetic wave systems, a reader and an RF tag perform wireless communications by using an RF antenna. Since electromagnetic wave RF tags fail to receive a sufficient amount of power for driving IC chips from a reader, there exist also RF tags (e.g., an active type) including an additional battery for long-distance recognition.

[5] However, the reader continuously or periodically generates electromagnetic waves regardless of whether a non-contact card embedded with the RF tag exists. Thus, unnecessary power may be wasted due to the generation of the electromagnetic waves by the reader.

[6] Moreover, when readers perform data communications with each other, an RF signal generated by another RF transmitter provokes signal interference. This leads to distortion of data that is transceived between the readers. Accordingly, the RF signal may hinder the data communications. Therefore, a reader capable of previously detecting the RF signal so as to prevent distortion of data is required. Disclosure of Invention Technical Problem

[7] The present invention provides a radio frequency (RF) reader capable of detecting an RF signal and preventing distortion of data, and a method of detecting existence or non-existence of a non-contact card.

[8] The present invention also provides an RF reader capable of detecting existence or non-existence of a non-contact card and preventing waste of unnecessary power, and a method of detecting existence or non-existence of a non-contact card.

Advantageous Effects

[9] In an RF reader and a method of detecting an RF signal and existence or non- existence of a non-contact card, according to the present invention, the RF signal serving as an obstacle to data communications between RF readers is detected so as to prevent distortion of data.

[10] In addition, existence or non-existence of the non-contact card is easily detected so as to reduce consumption of unnecessary power. Brief Description of the Drawings

[11] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

[12] FIG. 1 is a block diagram of a radio frequency (RF) reader according to an embodiment of the present invention;

[13] FIGS. 2 and 3 are waveforms of an output signal of the RF reader illustrated in FIG.

1 according to whether an RF signal exists;

[14] FIGS. 4 and 5 are waveforms of an output signal of the RF reader illustrated in FIG.

1 according to whether a non-contact card exists;

[15] FIG. 6 is a flowchart of a method of detecting an RF signal, according to an embodiment of the present invention; and

[16] FIG. 7 is a flowchart of a method of detecting whether a non-contact card exists, according to an embodiment of the present invention. Best Mode for Carrying Out the Invention

[17] According to an aspect of the present invention, there is provided a radio frequency

(RF) reader comprising: a rectifying unit receiving a RF signal via an antenna, shifting a level of the RF signal, and rectifying the level-shifted RF signal; and a comparator comparing an output signal of the rectifying unit with a reference signal and outputting a result of the comparison as an RF detection signal.

[18] The rectifying unit may further comprise: a level shifter shifting the level of the RF signal; and a rectifier rectifying the RF signal level-shifted by the level shifter. The RF reader may further comprise a digital-to-analog converter generating the reference signal in response to an N-bit control signal. According to another aspect of the present invention, there is provided an RF reader comprising: a card detection pulse signal generation unit generating a card detection pulse signal via an antenna; a rectifying unit receiving a card detection reflection signal via the antenna, shifting a level of the card detection reflection signal, and rectifying the level-shifted card detection reflection signal; and a comparator comparing an output signal of the rectifying unit with a reference signal and outputting a result of the comparison as a card detection signal for detecting whether a non-contact card exists, wherein the card detection reflection signal is obtained by reflecting the card detection pulse signal by using the non-contact card.

[19] The rectifying unit may comprise: a level shifter shifting the level of the card detection reflection signal; and a rectifying circuit rectifying the card detection reflection signal level-shifted by the level shifter. The RF reader may further comprise a digital-to- analog converter generating the reference signal in response to an N-bit control signal.

[20] According to another aspect of the present invention, there is provided an RF reader comprising: a card detection pulse signal generation unit generating a card detection pulse signal via an antenna; a rectifying unit, when it is detected whether a non-contact card exists, receiving a card detection reflection signal via the antenna, shifting a level of the card detection reflection signal, and rectifying the level-shifted signal so as to generate a rectified first output signal, and when an RF signal is detected, receiving the RF signal via the antenna, shifting a level of the RF signal, and rectifying the level- shifted signal so as to generate a rectified second output signal; and a comparator, when it is detected whether the non-contact card exists, comparing the first output signal with a first reference signal and outputting a result of the comparison as a card detection signal for detecting whether the non-contact card exists, and when an RF signal is detected, comparing the second output signal with a second reference signal and outputting a result of the comparison as an RF detection signal for detecting the R F signal, wherein the card detection reflection signal is obtained by reflecting the card detection pulse signal by using the non-contact card.

[21] The RF reader may further comprise a digital-to-analog converter generating one of the first and second reference signals in response to an N-bit control signal.

[22] According to another aspect of the present invention, there is provided a method of detecting an RF signal, comprising: a rectifying operation of receiving the RF signal via an antenna, shifting a level of the RF signal, and rectifying the level-shifted RF signal; and an operation of comparing a rectified signal generated in the rectifying operation with a reference signal and outputting a result of the comparison as an RF detection signal for detecting the RF signal. [23] According to another aspect of the present invention, there is provided a method of detecting existence or non-existence of a non-contact card, the method comprising: generating a card detection pulse signal via an antenna; receiving a card detection reflection signal via the antenna, shifting a level of the card detection reflection signal, and rectifying the level-shifted card detection reflection signal; and comparing a rectified signal generated in the immediately previous operation with a reference signal and outputting a result of the comparison as a card detection signal for detecting whether a non-contact card exists, wherein the card detection reflection signal is obtained by reflecting the card detection pulse signal by using the non-contact card. Mode for the Invention

[24] The attached drawings for illustrating preferred embodiments of the present invention are referred to in order to gain a sufficient understanding of the present invention, the merits thereof, and the objectives accomplished by the implementation of the present invention. Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements.

[25] FIG. 1 is a block diagram of a radio frequency (RF) reader 10 according to an embodiment of the present invention. Referring to FIG. 1, the RF reader 10 may include a transmitter 20, a card detection signal generator (CDD) 30, an antenna 40, an attenuator 50, a switching unit 60, a rectifying unit 70, a comparator 80, and a digital- to-analog converter (DAC) 90. The switching unit 60, the rectifying unit 70, the comparator 80, and the DAC 90 may be incorporated into a single integrated circuit (IC) chip, but the present invention is not limited thereto.

[26] The transmitter 20 receives and amplifies a data signal generated by a data storage unit (not shown) of the RF reader 10 and outputs the amplified signal as an RF transmission signal Vl. When the RF reader 10 detects existence or non-existence of a non-contact card (not shown), the card detection signal generator 30 generates a card detection pulse signal V3. The card detection pulse signal V3 is a signal for detecting existence or non-existence of the non-contact card. The RF reader 10 detects existence or non-existence of the non-contact card on the basis of a card detection reflection signal V7 obtained by reflecting the card detection pulse signal V3 by using the non- contact card.

[27] The card detection pulse signal V3 may be a power signal lower than the RF transmission signal Vl generated by the transmitter 20. The card detection signal generator 30 may generate the card detection pulse signal V3. More specifically, the card detection signal generator 30 may receive and amplify an oscillation signal generated by a signal oscillator (not shown) and outputs the amplified signal as the card detection pulse signal V3.

[28] Accordingly, the RF reader 10 according to the current embodiment of the present invention is able to easily detect existence or non-existence of the non-contact card without consuming unnecessary power, by including the card detection signal generator 30 generating the card detection pulse signal V3, which consumes a small amount of power regardless of the transmitter 20. The antenna 40 outputs the RF transmission signal Vl or the card detection pulse signal V3 to an RF signal receiver (not shown) and transmits an RF signal Vrf or the card detection reflection signal V7 received from the RF signal receiver to the attenuator 50.

[29] An LC filter (not shown) may be connected between the transmitter 20, the card detection signal generator 30, and the antenna 40, and may low-pass filter the RF transmission signal Vl or the card detection pulse signal V3 generated by the transmitter 20 or the card detection signal generator 30, respectively, and remove noise from the RF transmission signal Vl or the card detection pulse signal V3.

[30] The attenuator 50 receives and attenuates the RF signal Vrf from the RF signal receiver via the antenna 40 so as to generate a first attenuation signal V9, or receives and attenuates the card detection reflection signal V7 so as to generate a second attenuation signal VI l.

[31] The switching unit 60 transmits the first or second attenuation signal V9 or Vl 1 output by the attenuator 50 to the rectifying unit 70 in response to a power-down signal rfl-pwdn. The switching unit 60 may be a transistor which is gated in response to the power-down signal rfl-pwdn, but the present invention is not limited to this example.

[32] A DC remover (not shown) may be connected between the attenuator 50 and the switching unit 60. The DC remover may remove a DC signal from the first or second attenuation signal V9 or Vl 1 output by the attenuator 50 and generate a signal which the DC signal has been removed. When the RF signal Vrf is detected, the rectifying unit 70 receives the first attenuation signal V9, shifts a level of the first attenuation signal V9, rectifies the level-shifted first attenuation signal V9, and generates the rectified signal as a first output signal V 13.

[33] When existence or non-existence of a non-contact card is detected, the rectifying unit 70 receives the second attenuation signal VI l, shifts a level of the second attenuation signal VI l, rectifies the level- shifted second attenuation signal VI l, and generates a rectified signal as the second output signal V 15.

[34] The rectifying unit 70 may receive the RF signal Vrf directly from the antenna 40 without passing through the attenuator 50, shift a level of the RF signal Vrf, rectify the level-shifted signal, and generate the rectified signal as the first output signal V13. When existence or non-existence of a non-contact card is detected, the rectifying unit 70 may receive the card detection reflection signal V7 via the antenna 40, shift a level of the card detection reflection signal V7, rectify the level-shifted signal, and generate a rectified signal as the second output signal V 15.

[35] The rectifying unit 70 may include a level shifting unit 71 and a rectifier 73. The level shifting unit 71 shifts the level of the first attenuation signal V9 or the second attenuation signal VI l and outputs a level-shifted signal. The rectifying unit 70 may include a first diode 71-1 and a DC level generation unit 71-2. Of course, the first diode 71-1 may be an element for shifting the level of the first attenuation signal V9 or the second attenuation signal Vl 1 to the level of a predetermined DC voltage (Vr) generated by the DC level generation unit 71-2, and may be implemented as a transistor or level shifting circuit (not shown).

[36] Of course, the first diode 71-1 may be implemented as not only a general rectifier diode but also a Schottky diode or a MOS diode. The DC level generation unit 71-2 generates the predetermined DC voltage Vr. When the level of the first attenuation signal V9 or the second attenuation signal Vl 1 is small, the first attenuation signal V9 or the second attenuation signal VI l may not be transmitted to the comparator 80 because of a low cut-in voltage of a second diode D.

[37] However, the level shifting unit 71 of the RF reader 10 according to the current embodiment of the present invention shifts (for example, levels up) the level of the first or second attenuation signal V9 or Vl 1 although the first or second attenuation signal V9 or Vl 1 has a low voltage, thereby increasing the reliability of a transmitted signal.

[38] The rectifier 73 rectifies an output signal of the level shifting unit 71 and outputs the first or second output signal V13 or V15, which is the rectified signal (e.g., a DC signal).

[39] When the RF signal Vrf is detected, the comparator 80 compares the first output signal V13 with a first reference signal Vref 1 and outputs a result of the comparison as an RF detection signal for detecting the RF signal Vrf. When existence or non- existence of a non-contact card is detected, the comparator 80 compares the second output signal V15 with a second reference signal Vref2 and outputs a result of the comparison as a card detection signal for detecting existence or non-existence of a non-contact card.

[40] For example, when the RF signal Vrf is detected, the comparator 80 may compare the first output signal V13 with the first reference signal Vref 1. If a voltage of the first output signal V13 is less than a voltage of the first reference signal Vrefl, the comparator 80 may output a comparison signal rfl_out having a first logic level (for example, a low level ("0")) as the RF detection signal. On the other hand, if the voltage of the first output signal V13 is greater than the voltage of the first reference signal Vrefl, the comparator 80 may output the comparison signal rfl_out having a second logic level (for example, a high level ("1")) as the RF detection signal.

[41] When existence or non-existence of a non-contact card is detected, the comparator

80 may compare the second output signal V 15 with the second reference signal Vref2. If a voltage of the second output signal V15 is less than a voltage of the second reference signal Vref2, the comparator 80 may output the comparison signal rfl_out having a first logic level (for example, a low level ("0")) as the card detection signal for detecting existence or non-existence of a non-contact card. On the other hand, if the voltage of the second output signal V15 is greater than the voltage of the second reference signal Vref2, the comparator 80 may output the comparison signal rfl_out having a second logic level (for example, a high level ("1")) as the card detection signal for detecting existence or non-existence of a non-contact card.

[42] The card detection reflection signal V7 is obtained by reflecting the card detection pulse signal V3 by using the non-contact card. The DAC 90 may generate the first reference signal Vref 1 or the second reference signal Vref2 in response to an N-bit (where N is a natural number) control signal rfcnt, and the first reference signal Vref 1 or the second reference signal Vref2 may correspond to a constant voltage.

[43] Of course, the first reference signal Vref 1 and the second reference signal Vref2 may have different levels that serve as reference values for use in detecting the RF signal Vrf and existence or non-existence of a non-contact card, respectively. Of course, the first reference signal Vref 1 and the second reference signal Vref2 may have the same level.

[44] FIGS. 2 and 3 are waveforms of an output signal of the RF reader 10 of FIG. 1 according to whether an RF signal exists. Referring to FIGS. 1, 2, and 3, after the power-down signal rfl-pwdn is applied, the rectifying unit 70 receives the first attenuation signal V9, shifts the level of the first attenuation signal V9, rectifies the level-shifted signal, and generates the rectified first output signal V13.

[45] The comparator 80 compares the first output signal V13 with the first reference signal Vref 1 and outputs a result of the comparison, namely, the comparison signal rfl_out, as the RF detection signal for detecting the RF signal Vrf. For example, when there are no RF signals Vrf illustrated in FIG. 2, the comparator 80 may output the comparison result rfl_out having the first logic level (for example, the low level ("0")) as the RF detection signal for detecting the RF signal Vrf. When there is an RF signal Vrf illustrated in FIG. 3, the comparator 80 may output the comparison result rfl_out having the second logic level (for example, the high level ("1")) as the RF detection signal for detecting the RF signal Vrf.

[46] FIGS. 4 and 5 are waveforms of an output signal of the RF reader 10 of FIG. 1 according to whether a non-contact card exists. Referring to FIGS. 1, 4, and 5, after the power-down signal rfl-pwdn is applied, the rectifying unit 70 receives the second attenuation signal VI l, shifts the level of the second attenuation signal VI l, rectifies the level-shifted signal, and generates the rectified second output signal V15.

[47] The comparator 80 compares the second output signal V15 with the second reference signal Vref2 and outputs a result of the comparison, namely, the comparison signal rfl_out, as the card detection signal for detecting whether a non-contact card exists. For example, when there are no non-contact cards illustrated in FIG. 4, the comparator 80 may output the comparison result rfl_out having the second logic level (for example, the high level ("1")) as the card detection signal for detecting whether a non-contact card exists. When there is a non-contact card illustrated in FIG. 5, the comparator 80 may output the comparison result rfl_out having the first logic level (for example, the low level ("0")) as the card detection signal for detecting whether a non- contact card exists.

[48] FIG. 6 is a flowchart of a method of detecting the RF signal Vrf, according to an embodiment of the present invention. Referring to FIGS. 1 and 6, in operation SlO, the rectifying unit 70 receives the RF signal Vrf via the antenna 40, shifts the level of the RF signal Vrf, and rectifies the level-shifted signal. In operation S 12, the comparator 80 compares the rectified signal V13 with the first reference signal Vrefl and outputs a result of the comparison, namely, the comparison signal rfl_out, as the RF detection signal for detecting the RF signal Vrf.

[49] FIG. 7 is a flowchart of a method of detecting whether a non-contact card exists, according to an embodiment of the present invention. Referring to FIGS. 1 and 7, in operation S20, the card detection signal generator (CDD) 30 generates the card detection pulse signal V3 via the antenna 40. In operation S22, the rectifying unit 70 receives the card detection reflection signal V7 via the antenna 40, shifts the level of the card detection reflection signal V7, and rectifies the level-shifted signal.

[50] In operation S24, the comparator 80 compares the rectified signal V13 with the second reference signal Vref2 and outputs the comparison result rfl_out as the card detection signal for detecting whether a non-contact card exists.

[51] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. Industrial Applicability

[52] The present invention is applicable to an RF reader.

Claims

[1] A radio frequency (RF) reader comprising: a rectifying unit receiving a RF signal via an antenna, shifting a level of the RF signal, and rectifying the level-shifted RF signal; and a comparator comparing an output signal of the rectifying unit with a reference signal and outputting a result of the comparison as an RF detection signal.

[2] The RF reader of claim 1, wherein the rectifying unit comprises: a level shifter shifting the level of the RF signal; and a rectifier rectifying the RF signal level-shifted by the level shifter.

[3] The RF reader of claim 1, further comprising a digital-to-analog converter generating the reference signal in response to an N-bit control signal.

[4] An RF reader comprising: a card detection pulse signal generation unit generating a card detection pulse signal via an antenna; a rectifying unit receiving a card detection reflection signal via the antenna, shifting a level of the card detection reflection signal, and rectifying the level- shifted card detection reflection signal; and a comparator comparing an output signal of the rectifying unit with a reference signal and outputting a result of the comparison as a card detection signal for detecting whether a non-contact card exists, wherein the card detection reflection signal is obtained by reflecting the card detection pulse signal by using the non-contact card.

[5] The RF reader of claim 4, wherein the rectifying unit comprises: a level shifter shifting the level of the card detection reflection signal; and a rectifying circuit rectifying the card detection reflection signal level-shifted by the level shifter.

[6] The RF reader of claim 4, further comprising a digital-to-analog converter generating the reference signal in response to an N-bit control signal.

[7] An RF reader comprising: a card detection pulse signal generation unit generating a card detection pulse signal via an antenna; a rectifying unit, when it is detected whether a non-contact card exists, receiving a card detection reflection signal via the antenna, shifting a level of the card detection reflection signal, and rectifying the level-shifted signal so as to generate a rectified first output signal, and when an RF signal is detected, receiving the RF signal via the antenna, shifting a level of the RF signal, and rectifying the level-shifted signal so as to generate a rectified second output signal; and a comparator, when it is detected whether the non-contact card exists, comparing the first output signal with a first reference signal and outputting a result of the comparison as a card detection signal for detecting whether the non-contact card exists, and when an RF signal is detected, comparing the second output signal with a second reference signal and outputting a result of the comparison as an RF detection signal for detecting the RF signal, wherein the card detection reflection signal is obtained by reflecting the card detection pulse signal by using the non-contact card.

[8] The RF reader of claim 7, further comprising a digital-to-analog converter generating one of the first and second reference signals in response to an N-bit control signal.

[9] A method of detecting an RF signal, comprising: a rectifying operation of receiving the RF signal via an antenna, shifting a level of the RF signal, and rectifying the level-shifted RF signal; and an operation of comparing a rectified signal generated in the rectifying operation with a reference signal and outputting a result of the comparison as an RF detection signal for detecting the RF signal.

[10] A method of detecting existence or non-existence of a non-contact card, the method comprising: generating a card detection pulse signal via an antenna; receiving a card detection reflection signal via the antenna, shifting a level of the card detection reflection signal, and rectifying the level-shifted card detection reflection signal; and comparing a rectified signal generated in the immediately previous operation with a reference signal and outputting a result of the comparison as a card detection signal for detecting whether a non-contact card exists, wherein the card detection reflection signal is obtained by reflecting the card detection pulse signal by using the non-contact card.