KR101189286B1 - Radio Frequency IDentification tranceiver system being capable of preventing interference of Receiving signal - Google Patents

Abstract

RFID transmitting and receiving system capable of preventing interference of a received signal according to the present invention includes an antenna stage for receiving a received signal; A phase synchronization circuit unit generating an oscillation frequency signal; A frequency multiplier for generating a signal of a harmonic component by frequency multiplying the oscillation frequency signal; A first mixer which combines the signal of the harmonic component with the received signal and converts the signal into a phase inverted signal; And a second mixer for mixing the phase inverted signal with the oscillation frequency signal to generate a baseband signal.

According to the present invention, since the tag signal can be stably restored / processed by eliminating the interference phenomenon between the tag signals or the interference between the tag signal and the noise component signal, communication can be performed without interference between readers. In addition, RFID communication can be performed by installing a plurality of readers in a limited space, and there is an effect of improving the recognition rate of a tag including a recognition distance and a reception sensitivity.

Description

Radio Frequency IDentification tranceiver system being capable of preventing interference of Receiving signal

1 is a block diagram schematically showing the components of an RFID transceiver system capable of preventing interference of a received signal according to an embodiment of the present invention.

2 is a graph measuring transmission and reception signals of a general RFID transmission and reception system.

3 is a graph measuring a carrier frequency carrying a transmission and reception signal of a typical RFID transmission and reception system.

4 is a diagram illustrating a case where a transmission / reception separation unit of an RFID transmission / reception system capable of preventing interference of a reception signal according to an embodiment of the present invention is implemented as a combiner.

FIG. 5 is a diagram illustrating a frequency multiplied form of an oscillation frequency signal by a frequency multiplier of an RFID transceiver system capable of preventing interference of a reception signal according to an embodiment of the present invention.

Description of the Related Art

100: RFID transceiver system

105: antenna 110: transmission and reception separation unit

115: LNA 120: phase synchronization circuit

125: frequency multiplier 130: channel filter

140: first mixer 145: GA

150: second mixer 165: demodulator

155, 160, 185: first filter, second filter, third filter

170: control unit 175: modulation unit

180: third filter 185: PAM

The present invention relates to an RFID transmission and reception system capable of preventing interference of a received signal.

Nowadays, ubiquitous network technology is attracting attention of many people. Ubiquitous network technology means a technology that makes it possible to connect to various networks smoothly regardless of time and place.

As such ubiquitous network technology, there is RFID technology, and among them, RFID technology introduced in commerce is representative.

In general, a commercial RFID system consists of an RFID tag attached to a product and embedded with details, an RFID reader that reads information of the RFID tag using RF communication, and the RFID tag attached to the product is located at which the RFID reader is located. As it passes the region and transmits the information using RF communication, it provides a foundation for efficient logistics / distribution management such as product distribution, assembly, price change, and sales.

On the other hand, the conventional RFID transmission and reception system is generally implemented through the envelope detection using the Amplitude Shift Keying (ASK) modulation method, according to the conventional design method, there is a disadvantage that the data recognition rate is formed because the bit error rate is lowered.

In particular, in the case of the RFID reader, the radio wave environment is severely changed due to the tag moving at a high speed, and a change in the reception signal is greatly generated according to the external environment change (for example, the tag signal generated when the tag is moved). Phase shift, etc.), in particular frequency interference between RFID readers, has a significant effect on the recognition rate of RFID tags.

For example, when a large number of tags exist in an area where a plurality of RFID readers are installed, tag signals using the same frequency band may be simultaneously received by the RFID readers. In this case, interference between tag signals may occur and the RFID reader may There is a problem that the signal cannot be processed and the data recognition rate is further lowered.

In addition, when the transmission signal of another RFID reader or its own transmission signal is transmitted to the receiving end of the RFID reader, the transmission signal may act as an interference signal, which may make processing of the tag (reception) signal more difficult.

In addition, when the tag is moved, since the supply position of the energy is also changed, this becomes a factor to lower the recognition rate, and there is a problem that the reception sensitivity and the recognition distance are also reduced.

RFID frequencies range from low frequency (LF) such as 125 KHz and 135 KHz, high frequency (HF) such as 13.56 MHz, ultra high frequency (UHF) in the 433 MHz and 900 MHz bands, and microwave in the 2.45 GHz band. The frequency of the 900 MHz band is expected to be widely used due to the advantages of being able to make it small, small, long recognition distance, and distinguishing multiple tags.

However, since the frequency of the 900 MHz band has a narrow overall frequency bandwidth and a small number of carriers, the influence of an external interference signal including a transmission signal or interference between the tag signals can be recognized as a more serious problem.

The present invention can stably recover / process a tag signal by excluding interference between tag signals or interference between tag signals and noise component signals, and minimizes interference between readers. Provides a transmission and reception system.

The present invention also provides an RFID transmission / reception system capable of preventing interference of a reception signal capable of installing / operating a plurality of readers in a limited area by minimizing interference between readers.

In addition, the present invention provides a RFID transmission and reception system capable of varying the modulation frequency through a minimum circuit configuration, improves the data recognition rate and prevents interference of the received signal capable of performing high-speed and stable communication.

RFID transmitting and receiving system capable of preventing interference of a received signal according to the present invention includes an antenna stage for receiving a received signal; A phase synchronization circuit unit generating an oscillation frequency signal; A frequency multiplier for generating a signal of a harmonic component by frequency multiplying the oscillation frequency signal; A first mixer which combines the signal of the harmonic component with the received signal and converts the signal into a phase inverted signal; And a second mixer for mixing the phase inverted signal with the oscillation frequency signal to generate a baseband signal.

Hereinafter, an RFID transmission / reception system (hereinafter referred to as an “RFID transmission / reception system”) capable of preventing interference of a reception signal according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The RFID transmission / reception system is implemented on an RFID reader, and the UHF signal in the 900 MHz band is used as a carrier signal.

1 is a block diagram schematically illustrating the components of an RFID transceiver system 100 according to an embodiment of the present invention.

Referring to FIG. 1, an RFID transceiver system 100 according to an embodiment of the present invention includes an antenna 105, a transceiver 110, a low noise amplifier (LNA) 115, a phase synchronization circuit 120, and a frequency multiplier. (125), channel filter 130, first mixer 140, GA (Gain Amplifier) 145, second mixer 150, first filter 155, second filter 160, demodulator ( 165, a control unit 170, a modulator 175, a third filter 180, and a power amplifier module (PAM) 185.

The antenna 105 is provided in one, not separated according to the transmission and reception signal, and transmits the received signal to the transmission and reception separation unit 110 or radiates the transmission signal transmitted from the transmission and reception separation unit 110 to the atmosphere, where the reception The signal may be received mixed with various interference signals.

2 is a graph measuring transmission and reception signals of a general RFID transmission and reception system 100, and FIG. 3 is a graph measuring carrier frequencies on which transmission and reception signals of a general RFID transmission and reception system 100 are carried.

Referring to FIG. 2, an interference signal for each channel including a transmission signal and a reception signal are mixed together. A signal B between a reference line "C1" and "C2" is a tag signal, that is, an area of a reception signal. , The region above the reference line "C1" and the region below "C2" are regions of the interference signal.

The interference signal may be a signal transmitted from the transmission path end, a signal transmitted and fed back through the antenna 105 and mixed with the received signal, or may be an interference signal between adjacent channels.

When the interference signal is a feedback transmission signal, it has a power range of about 30 dBm, and the reception signal has a power range of about -10 dBm, so that the reception signal is buried in the feedback transmission signal as shown in FIG. It will be difficult to restore.

Referring to FIG. 3, a form in which a carrier frequency of an interference signal and a carrier frequency of a received signal are mixed together and transmitted is illustrated in a frequency domain. The "A" signal measures a carrier frequency signal carrying an interference signal. The " B " signal measures a carrier frequency signal carrying a received signal.

When the reception signal and the interference signal are mixed as described above, it becomes difficult to stably restore the tag signal. According to the present invention, a signal of a harmonic component is generated by multiplying an oscillation frequency signal provided to the modulator 175 and the second mixer 150. By combining the received signal with the received signal, the signal can be converted into a phase inverted signal, thereby eliminating signals causing interference.

This technical content is a core technical idea of the present invention, which will be described later in detail.

4 is a diagram illustrating a case in which the transmission and reception separation unit 110 of the RFID transmission and reception system 100 according to an embodiment of the present invention is implemented as a combiner.

The transmission and reception separation unit 110 is connected to the antenna 105 to separate the transmission and reception signal, it may be implemented as a branch line coupler as shown in FIG.

The branch line coupler is rectangular in shape, having a 1 / 4λ length between each of the ports P1, P2, P3, and P4, having a phase difference of 90 °, and having an isolation of about 25 dB to 35 dB between transmit and receive signals, 105) has an insertion loss of approximately -3dB.

The first port P1 of the branch line coupler is connected to the antenna 105, and the fourth port P4 is connected to the ground terminal. The second port P2 is connected to the LNA 115 and the third port P3 is connected to the PAM 185.

When a signal is received through the antenna 105, the received signal is input through the first port P1 and is transmitted to the second port P2 and the third port P3 with a phase difference.

The received signal transmitted to the third port P3 is blocked by the impedance component according to the phase difference, and is mostly transmitted to the LNA 115 through the second port P2. When the transmission signal is transmitted from the PAM 185, the transmission signal is input through the third port P3 and distributed to the first port P1 and the second port P2 with a phase difference. The transmission signal transmitted to the second port P2 is blocked by the impedance component according to the phase difference, and most of the signal is transmitted to the antenna 105 through the first port P1.

As such, even when the transmission / reception signal is separated through the transmission / reception separator 110, the interference signal remains in the reception signal.

The LNA 115 low noise amplifies the power of the received signal lowered due to attenuation and noise.

On the other hand, the phase synchronization circuit unit 120 generates an oscillation frequency signal of about 900 MHz band and provides it to the modulation unit 175, the second mixer 150 and the frequency multiplier 125, the modulation unit 175 and The oscillation frequency signal provided to the second mixer 150 is used to generate the baseband transmission signal and the baseband reception signal, and the oscillation frequency signal provided to the frequency multiplier 125 is used to exclude the interference component of the reception signal. .

The frequency multiplier 125 is a device for multiplying an input frequency by an integer (N), including a nonlinear element such as a transistor or a variable capacitance diode, and has an integer multiple of the power of the transmitted oscillation frequency signal using a nonlinear characteristic. Generate a harmonic component signal.

The channel filter 130 filters the noise signal of the harmonic component signal mixed in the frequency sequencing process (for example, may be provided as a SAW filter) and transmits the noise signal to the first mixer 140.

The first mixer 140 may be implemented as a single mixer element such as a mixer diode, for example, by synthesizing the harmonic component signal transmitted from the channel filter 130 and the received signal transmitted from the LNA 115. Convert to a phase inverted signal.

5 is a diagram illustrating a form in which the oscillation frequency signal is multiplied by the frequency multiplier 125 of the RFID transceiver system 100 according to an embodiment of the present invention in a frequency domain.

According to Fig. 5, the first oscillation frequency signal is measured as the "A" signal, and the signal multiplied by twice the frequency, that is, the signal of the 2nd-harmonic component, is measured as the "B" signal. Therefore, the "A" signal is a signal in the 900 MHz band, and the "B" signal is a signal in the 1.8 GHz band.

The first mixer 140 generates a phase inverted signal by mixing (±) the "A" signal and the "B" signal, that is, a signal of 900 MHz band or 2.7 GHz band of (-) phase. The frequency multiplier 125 may generate harmonic component signals of various orders, and thus various phase inverted signals may be generated according to a combination of them. .

For convenience of description, in the embodiment of the present invention, the signal of the second harmonic component is generated by the frequency multiplier 125, and the signals of the 900 MHz band inverted phase are mixed.

The received signal inverted in phase in the first mixer 140 is amplified through the GA 145 and mixed into the baseband received signal through the second mixer 150.

The second mixer 150 includes a balloon circuit 151, a first mixer 152, and a second mixer 154. The balloon circuit 151 receives a phase-inverted received signal using an I signal (eg, , "E sin ωt") and a Q signal (e.g., "E cos ωt") (i.e., convert a single input signal into a differential signal and output it).

Here, "Balun" is an abbreviation of "Balance-Unbalance", and means a circuit for converting a balanced signal into an unbalanced signal (or vice versa).

The output terminal of the balloon circuit 151 is connected to the first mixer 152 and the second mixer 154. The mixers 152 and 154 are dual mixers, and the first mixer 152 has a 90 degree phase difference. having I baseband signal (I ⁺ signal and the ^I-signal) to synthesize a composite, and the second mixer 154 is the baseband signal Q (Q ⁺ signal and Q signal) having a phase difference of 90 degrees.

The demodulator 165 includes an analog to digital converter (ADC) to demodulate the baseband I signal and the baseband Q signal into digital signals having a plurality of polarities.

The control unit 170 has a communication protocol to control wireless communication with the tag, and processes the signal transmitted from the demodulator 165 as a digital signal on the application layer or modulates the processed digital signal (eg, command data). Transfer to section 175.

The control unit 170 transmits a control signal to the phase synchronization circuit unit 120 to supply a corresponding oscillation frequency signal according to the type of RFID signal channel and the transmission / reception band.

In addition, the controller 170 analyzes the code of the device identification information received from the tag, at this time, to process the filtering operation to convert the data format and extract the necessary information. The controller 170 may be implemented using a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit.

The modulator 175 may include a single mixer or a plurality of mixers, and combines the digital transmission signal transmitted from the control unit 170 with the oscillation frequency signal transmitted from the phase synchronization circuit unit 120 to form an analog signal. Modulation is performed with the transmission signal in the state.

At this time, the modulator 175 modulates according to a pulse-interval encoding (PIE) signal standard according to the UHF RFID Protocol such as ISO 18000-6A, ISO 18000-6B, ISO 18000-6C, and the like.

The PAM 185 includes a power amplifier to amplify the transmission signal in a state capable of outputting, and the amplified signal is transmitted to the tag through the antenna 105.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications not illustrated in the drawings are possible. For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

According to the RFID transmission / reception system capable of preventing interference of a received signal according to the present invention, the tag signal can be stably restored / processed by eliminating the interference phenomenon between the tag signals or the interference between the tag signal and the noise component signal, and thus the inter-readers There is an effect that communication can be performed without interference.

In addition, according to the present invention, it is possible to perform a RFID communication by installing a plurality of readers in a limited space, there is an effect that can improve the recognition rate of the tag, including the recognition distance and reception sensitivity.

In addition, according to the present invention, even when using an RFID frequency band with a narrow bandwidth and a small number of carriers, there is an effect that communication can be performed by minimizing interference between bands.

Claims (6)

An antenna stage for receiving a received signal; A phase synchronization circuit unit generating an oscillation frequency signal; A frequency multiplier for generating a signal of a harmonic component by frequency multiplying the oscillation frequency signal; A first mixer which combines the signal of the harmonic component with the received signal and converts the signal into a phase inverted signal; And And a second mixer for mixing the phase inverted signal and the oscillation frequency signal to generate a baseband signal. The method of claim 1, RFID transmission and reception system capable of preventing interference of a received signal comprising a channel filter connected between the frequency multiplier and the first mixer. The method of claim 1, And a modulation unit configured to modulate the oscillation frequency signal transmitted from the phase synchronization circuit unit with a transmission signal and modulate the received signal. The method of claim 1, wherein the first mixer RFID transmission and reception system capable of preventing interference of a received signal comprising a mixer, a diode. The method of claim 1, The antenna stage is provided as one, RFID transmission and reception system capable of preventing the interference of the received signal comprising a transmission and reception separation unit is connected to the antenna end to separate the transmission and reception signals. The method of claim 1, The oscillation frequency signal is a signal of the 900 MHz band, The signal of the harmonic component is a signal of the 1.8 GHz band, The first mixer is an RFID transceiver system capable of preventing interference of the received signal to generate a signal of the phase inverted 900 MHz band.

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