KR101372060B1 - Radio Frequency IDentification receiver system using demodulation carrier variable - Google Patents

Abstract

RFID receiving system using modulation frequency multiplexing according to the present invention comprises a phase synchronization circuit for generating an oscillation frequency signal; A DCV (Demodulation Carrier Variable) circuit unit for shifting the frequency band of the oscillation frequency signal and converting the oscillation frequency signal into a plurality of oscillation frequency signals; A signal converter for converting the oscillation frequency signal shifted in the frequency band into an intermediate frequency signal by combining with the RF signal; And a control unit for transmitting a control signal for controlling the frequency tuning operation of the DCV circuit unit.

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, 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.

Description

Radio frequency identification receiver system using demodulation carrier variable

1 is a block diagram schematically illustrating the components of an RFID receiving system using modulation frequency multiplexing according to an embodiment of the present invention.

2 is a graph illustrating a spectrum mask of an RFID signal standard applicable to an RFID receiving system using modulation frequency multiplexing according to an embodiment of the present invention.

3 is a block diagram schematically illustrating the components of a phase synchronization circuit unit of an RFID receiving system using modulation frequency multiplexing according to an embodiment of the present invention.

Figure 4 is a block diagram schematically showing the components of the DCV circuit portion of the RFID receiving system using modulation frequency multiplexing according to an embodiment of the present invention.

5 is a block diagram schematically illustrating the components of a signal converter of an RFID receiving system using modulation frequency multiplexing according to an embodiment of the present invention.

6 is a graph illustrating filtering characteristics after a modulation frequency is tuned by an RFID receiving system using modulation frequency multiplexing according to an embodiment of the present invention.

7 is a diagram illustrating a form in which a channel of a tag signal is separated in an RFID receiving system using modulation frequency multiplexing according to an embodiment of the present invention.

Description of the Related Art

100: RFID receiving system

105: antenna 110: first filter

115: LNA 117: Balloon circuit

120: signal conversion unit 125, 127: second filter, third filter

130: phase synchronization circuit section 140: DCV circuit section

150, 152: 1PA, 2PA 154: demodulator

160:

The present invention relates to an RFID receiving system.

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.

Such ubiquitous network technology includes 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.

Meanwhile, a conventional RFID reader is generally implemented through envelope detection using an amplitude shift keying (ASK) modulation scheme. According to the conventional design scheme, a bit error rate is lowered, thereby lowering a data recognition rate.

In addition, since the RFID reader targets a tag moving at a high speed, the radio wave environment is severely changed, and a change in the reception signal is greatly caused by an external environment change. It has a big impact.

For example, when there are many tags in a region where a plurality of RFID readers are installed, tag signals using the same frequency band can be simultaneously received by the RFID readers. In this case, an interference phenomenon occurs between the tag signals, The signal can not be processed and the data recognition rate is further lowered.

In addition, when the transmission signal of another RFID reader or its transmission signal is transmitted to the receiving end of the RFID reader, the transmission signal acts as an interference signal, making it difficult to process the tag (reception) signal.

The RFID frequencies are low frequency (LF) such as 125 KHz and 135 KHz, high frequency (HF) such as 13.56 MHz, ultra high frequency (UHF) in 433 MHz and 900 MHz band and microwave in 2.45 GHz band. The 900 MHz frequency band is expected to be widely used due to its advantages such as small size, long recognition range, and ability to distinguish multiple tags.

However, since the entire frequency bandwidth is narrow and the number of carriers is small, the frequency of the 900 MHz band can be perceived as a problem that the influence of an external interference signal including a transmission signal or a phenomenon of interference between the tag signals is more fatal.

The present invention can stably recover / process a tag signal by eliminating interference between tag signals or interference between tag signals and noise component signals, and provide an RFID receiving system with minimized interference between readers.

The present invention provides an RFID receiving system that can easily improve data recognition rate and perform high-speed and stable communication by adding a simple circuit applicable to a receiving signal path end.

RFID receiving system using modulation frequency multiplexing according to the present invention comprises a phase synchronization circuit for generating an oscillation frequency signal; A DCV (Demodulation Carrier Variable) circuit unit for shifting the frequency band of the oscillation frequency signal and converting the oscillation frequency signal into a plurality of oscillation frequency signals; A signal converter for converting the oscillation frequency signal shifted in the frequency band into an intermediate frequency signal by combining with the RF signal; And a control unit for transmitting a control signal for controlling the frequency tuning operation of the DCV circuit unit.

Hereinafter, an RFID receiving system (hereinafter, referred to as an “RFID receiving system according to the present invention”) using modulation frequency multiplexing according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The RFID receiving system according to the present invention is applied to the receiving path stage of the RFID reader, and various RFID signal bands can be applied, but in the embodiment of the present invention, the UHF signal of 900 MHz band is used.

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

1, an RFID receiving system 100 according to an exemplary embodiment of the present invention includes an antenna 105, a first filter 110, a low noise amplifier (LNA) 115, and a balloon circuit ( 117, the signal converter 120, the second filter 125, the third filter 127, the first PA (Power Amplifier) 150, the second PA 152, the phase synchronization circuit 130, and the DCV (Demodulation). Carrier Variable) circuit unit 140, demodulator 154 and the control unit 160 is made.

The RF signal received from the tag through the antenna 105 is filtered only the signal of the corresponding band by the first filter (which may be provided as a SAW filter) 110, the LNA 115 is attenuated And amplify the RF signal of the lowered power due to the influence of noise.

The balloon circuit 117 separates the signal transmitted from the LNA 115 into an I signal (eg, "E sin ωt") and a Q signal (eg "E cos ωt"), that is, a single input signal is differential signal. To output.

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 117 is connected to the first mixer 122 and the second mixer 124 of the signal converter 120, and the mixers 122 and 124 are dual mixers. 122 synthesizes a plurality of I intermediate frequency signals (frequency band shifted at predetermined intervals) (in the past, synthesized only with I ⁺ and I ⁻ signals), and second mixer 124 is frequency tuned. Synthesized multiple Q intermediate frequency signals (in the past, synthesized only with Q ⁺ and Q ⁻ signals).

At this time, the phase synchronization circuit unit 130 provides an oscillation frequency signal, and the DCV circuit unit 140 generates a plurality of oscillation frequency signals by moving (frequency tuning) the frequency band of the provided oscillation frequency signal at predetermined intervals. In the embodiment of the present invention, the DCV circuit unit 140 is to move the frequency band of the oscillation frequency signal at 200 KHz intervals.

The DCV circuit unit 140 transmits a plurality of frequency-tuned oscillation frequency signals to the signal converter 120, and the first mixer 122 and the second mixer 124 of the signal converter 120 are the oscillation frequency. The signals can be used to synthesize band-separated I intermediate frequency signals and Q intermediate frequency signals.

Unlike the conventional method, when the intermediate frequency signal is separated into bands, even if a tag signal to be received (hereinafter referred to as a "desired tag signal") and other tag signals using the same frequency band as other readers are mixed and received, respectively. It can be processed separately in different bands.

In addition, even when the desired tag signal is mixed with the noise component, the signal of the noise component is moved to another frequency band, thereby stably processing the desired tag signal.

For example, when a transmission signal transmitted by the reader itself or a transmission signal of another reader is transmitted to the receiving path end through the antenna, the transmission signal has a relatively large power value, so that the reception signal is buried in the transmission signal. The signal may act as a noise component signal that adversely affects the reception function.

However, since the frequency band of the transmission signal itself is shifted, the received signal can be stably processed without the phenomenon of radio interference or the distortion of the reference power, and there is no need to adjust the power.

The second filter 125 and the third filter (each of which may be provided as a "LPF; Low Pass Filter") 127 filter the frequency-tuned I intermediate frequency signal and Q intermediate frequency signal, respectively.

The first PA 150 and the second PA 152 amplify the frequency-tuned I intermediate frequency signal and the Q intermediate frequency signal to a magnitude that can be processed in the intermediate frequency band, and the demodulator 154 performs the amplified I signal and Q. The signal is demodulated into a digital signal having a plurality of polarities. The digitally processed signal is transmitted to the controller 160.

2 is a graph illustrating a spectral mask of an RFID signal standard applicable to an RFID receiving system 100 according to an exemplary embodiment of the present invention.

The demodulator 154 performs an amplification process in processing the digital signal. The demodulator 154 differentiates and amplifies the frequency-tuned intermediate frequency signal for each band according to the RFID signal standard shown in FIG. 2.

Referring to FIG. 2, the RFID signal standard defines power level values according to channels divided by 200 KHz bands, and the demodulator 154 includes a desired tag signal that is not band shifted, that is, a signal of 0 channel CH0. Is amplified based on 0 dBm, and the first (200 kHz) band shifted interference signal (eg, mixed other tag signal) CH1 is amplified based on -20 dBm.

In addition, the demodulator 154 amplifies another interference signal CH2, which is secondly shifted (400 kHz), on the basis of -50 dBm, and as a result, the signals of CH3 and CH4 are shifted by 200 kHz. Amplified by -60dBm and -65dBm respectively.

Therefore, not only the frequency band is separated but also the power of the frequency-tuned signals is differentiated for each channel, so that interference of adjacent channels can be minimized.

The controller 160 includes a communication protocol to control wireless communication with the tag, and processes the signal transmitted from the demodulator 154 into a digital signal on an application layer.

The controller 160 analyzes the code of the device identification information received from the tag. At this time, the controller 160 processes a filtering operation to convert the data format and extract necessary information. The controller 160 may be implemented using a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit.

3 is a block diagram schematically illustrating the components of the phase synchronization circuit unit 130 of the RFID receiving system 100 according to the embodiment of the present invention.

Referring to FIG. 3, the phase synchronization circuit unit 130 includes a TCXO (Temperature Controlled X-tal Oscillator) 131, a frequency detector 132, a divider 136, a charge pump 133, and a loop filter (LPF) 134. ), And includes a VCO (Voltage Controlled Oscillator) 135, and the VCO 135 includes a power supply 135b and a resonator 135a.

The TCXO 131 is a device for controlling the frequency disturbance according to the temperature change generated in the crystal oscillator. The TCXO 131 provides the frequency detector 132 with a reference frequency signal having a frequency of a constant value with respect to the temperature change.

The frequency detector 132 receives the reference frequency signal and detects and compares the oscillation frequency signal output from the VCO 135.

In general, since the oscillation frequency signal provided from the VCO 135 is a high frequency signal and the reference frequency signal provided from the TCXO 131 is a low frequency signal, the divider 136 uses the detected oscillation frequency signal at a low frequency so that the two signals can be compared. The signal is converted into a band and transmitted to the frequency detector 132.

The frequency detector 132 compares the two signals and transmits a control signal corresponding to the frequency difference to the charge pump 133, and the charge pump 133 adjusts the current value according to the control signal.

The charge pump 133 supplies a specific amount of charge to the loop filter 134 by a branch circuit if the voltage of the oscillation frequency signal is greater than that of the reference frequency signal, and charges the loop filter (if the voltage of the oscillation frequency signal is small). 134).

The loop filter 134 may be configured as, for example, a secondary filter including two capacitors and one resistor, and adjusts the voltage of the VCO 135 in response to the amount of charge pushed and pulled by the charge pump 133.

The power supply unit 135b supplies power and the resonator unit 135a adjusts the voltage by the loop filter 134 to provide a stable oscillation frequency signal, and the oscillation frequency signal supplied from the VCO 135 is It is transmitted to the DCV circuit unit 140 through the output terminal "A".

4 is a block diagram schematically showing the components of the DCV circuit unit 140 of the RFID receiving system 100 according to the embodiment of the present invention.

The DCV circuit unit 140 performs a function of tuning the frequency of the oscillation frequency signal and converting the oscillation frequency signal into a plurality of band shifted oscillation frequency signals. Referring to FIG. 4, the transformer 141, the diode unit 142, and Capacitors 143 and 144 are included.

The controller 160 sequentially transmits control signals having differentiated voltages so that the DCV circuit unit 140 can vary the phase of the oscillation frequency signal, and the transformer 141 responds to the feedback current according to the control signal. Perform frequency adjustment operation accordingly.

According to the transformer 141, the phase of the oscillation frequency signal can be shifted in units of 200 kHz band by mainly repeating inversion (inverting into an antiphase signal of the same amplitude).

The input terminal “A” of the transformer 141 is connected to the VCO 135 of the phase synchronization circuit unit 130, and the output terminal “B” is the first mixer 122 and the second mixer 124 of the signal converter 120. ).

The diode unit 142 includes two diodes 142a and 142b, wherein the first diode 142a and the second diode 142b are respectively provided at the first coil end and the second coil end of the transformer 141. Connected and connected to each other.

The input terminal of the first diode 142a is connected to the control signal input terminal C through the first resistor 142c, and the input terminal of the second diode 142b is connected to the control signal input terminal C through the second resistor 142d. ).

For example, when a voltage of about 2V is applied between the first diode 142a and the second diode 142b, and the voltage between the first resistor 142c and the second resistor 142d reaches about 0V or more, the diode (142a, 142b) is operated to tune the frequency of the oscillation frequency circuit, the frequency band can be moved more precisely by the diodes (142a, 142b).

The capacitor units 143 and 144 include a first capacitor 143 and a second capacitor 144 connected to the control signal input terminal C, and together with the first resistor 142c and the second resistor 142d. It performs the function of RC filter and isolates and filters the AC signal included in the control signal of DC component.

5 is a block diagram schematically showing the components of the signal conversion unit 120 of the RFID receiving system 100 according to an embodiment of the present invention.

The first mixer 122 and the second mixer 124 of the signal conversion unit 120 are frequency-tuned oscillation frequency signals (LO I ⁺ signal, LO I ⁻ signal, from the output terminal B of the DCV circuit unit 140, LO Q ⁺ signal, LO Q ⁻ signal), is combined with the RF + signal and RF-signal transmitted from the balloon circuit 117 (E1, E2), respectively IF I ⁺ signal, IF I ^- signal, IF Q ^The signal is converted into a ⁺ signal and an IF Q ⁻ signal and output to the second filter stages F1 and F2 and the third filter stages G1 and G2.

6 is a graph illustrating filtering characteristics after the modulation frequency is tuned by the RFID receiving system 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the frequency f2 of one channel carrying an interference signal is shifted by 200 kHz from the frequency f1 of the zero channel carrying the desired tag signal, thus eliminating interference between two signals. Can be.

FIG. 7 is a diagram illustrating an example in which a channel of a tag signal is separated in the RFID receiving system 100 according to an exemplary embodiment of the present invention.

According to FIG. 7, after processing the desired tag signal of the first 0 channel, the interference signal of one channel tuned to the next frequency is processed. At this time, the interval H1 of 200 kHz exists between the two signals, and the band is shifted. The transmission signal can be processed using the channel region H1 of 200 kHz.

Therefore, according to the present invention, the received signals that are mixed together to cause interference can be separately processed into channels of different bands, and the transmitted signals can also be stably processed separately from the received signals.

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 receiving system using the modulation frequency multiplexing according to the present invention, the tag eliminates the interference between the tag signal or the interference between the tag signal and the noise component signal (including the case where the transmission signal acts as a noise component). Since the signal can be stably restored / processed, communication can be performed without interference between readers.

In addition, according to the present invention, the data recognition rate can be improved through a simple circuit configuration that multiplexes the modulation frequency, and since an additional device is not required, an RFID receiving system can be implemented at low cost and at high speed. .

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 (9)

A phase synchronization circuit unit generating an oscillation frequency signal; A DCV (Demodulation Carrier Variable) circuit unit for shifting the frequency band of the oscillation frequency signal and converting the oscillation frequency signal into a plurality of oscillation frequency signals; A signal converter for converting the oscillation frequency signal shifted in the frequency band into an intermediate frequency signal by combining with the RF signal; And A control unit for transmitting a control signal for controlling the frequency tuning operation of the DCV circuit unit; The DCV circuit part A transformer for performing frequency tuning by receiving the oscillation frequency signal from the phase synchronization circuit unit; RFID receiving system using a modulation frequency multiplexing comprising a diode connected between the transformer and the control signal input terminal of the control unit. delete The method of claim 1, wherein the DCV circuit unit RFID receiving system using a modulation frequency multiplexing comprising a filter connected between the diode and the control signal input terminal. The method of claim 1, And a demodulator configured to receive the intermediate frequency signal from the signal converter and demodulate the digital signal and transmit the demodulated signal to the controller. The method of claim 1, wherein the signal conversion unit RFID reception system using modulation frequency multiplexing comprising two or more mixers. The method of claim 1, wherein the RF signal is RFID reception system using modulation frequency multiplexing which is processed as UHF signal of 900 MHz band. The method of claim 1, wherein the DCV circuit unit RFID receiving system using modulation frequency multiplexing to shift the frequency band of the oscillation frequency signal at intervals of 200 KHz. The method of claim 1, wherein the DCV circuit unit And a frequency band of the oscillation frequency signal corresponding to two or more tag signals or a frequency band of the oscillation frequency signal corresponding to a tag signal and a noise component signal. The method of claim 4, wherein the demodulation unit And a frequency band shifted amplified power of a signal processed into a digital signal according to a power level of a noise signal defined in an RFID signal standard.

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