KR20080056599A - Terminating system of interference signal - Google Patents

Abstract

An interference signal cancellation system is provided to process Rx signals stably and execute communication without any interference between communication systems by differentially correcting the phase of an Rx signal on the basis of the band of an interference signal and exactly canceling only the interference signal. An interference signal cancellation system comprises an interference signal cancellation circuit part(110), a phase detector(140), the first mixer(120), an interference signal detection circuit part(150), and a controller(130). The interference signal cancellation circuit part shifts the phase of an Rx signal on the basis of the band of an interference signal, creates a plurality of signals, compensates for the phases of the created signals, combines the phase-compensated signals, and cancels the interference signal. The phase detector receives the Rx signal from the interference signal cancellation circuit part, detects the phase of the Rx signal, and creates the first detection signal based on a phase difference for each frequency band. The first mixer converts the interference-cancelled Rx signal into an IF(Intermediate Frequency) signal. The interference signal detection circuit detects the power levels of channel-by-channel Rx signals and creates the second detection signal. The controller analyzes the second detection signal, confirms a channel where interference has been generated, creates a phase compensation control signal based on the first detection signal, and delivers it to the interference signal cancellation circuit part so that an interference signal can be cancelled only for the interference channel.

Description

Terminating system of interference signal

1 is a block diagram schematically showing the components of an interference signal cancellation system according to an embodiment of the present invention;

FIG. 2 is a block diagram schematically illustrating components of an interference signal canceling circuit unit configured in an interference signal canceling system according to an exemplary embodiment of the present invention. FIG.

FIG. 3 is a diagram illustrating a form in which a phase shifting unit of an interference signal removing circuit unit configured in an interference signal removing system according to an embodiment of the present invention is implemented as a balloon circuit. FIG.

4 is a diagram illustrating a form of a signal processed in an interference signal cancellation circuit unit included in an interference signal cancellation system according to an exemplary embodiment of the present invention.

FIG. 5 is a block diagram schematically illustrating components of a phase detection unit included in an interference signal cancellation system according to an exemplary embodiment of the present invention. FIG.

6 is a diagram illustrating a phase of a signal detected by a phase detector configured in an interference signal cancellation system according to an exemplary embodiment of the present invention.

FIG. 7 is a block diagram schematically illustrating components of an interference signal detecting circuit unit included in an interference signal removing system according to an exemplary embodiment of the present invention. FIG.

<Explanation of symbols for main parts of drawing>

100: interference signal cancellation system 105: the first antenna

110: interference signal cancellation circuit unit 170: LNA

180: first filter 120: first mixer

125: demodulation unit 130: control unit

135: phase synchronization circuit section 140: phase detection section

150: interference signal detecting circuit unit 160: second antenna

The present invention relates to an interference signal removal system for stably communicating by removing interference signals.

Currently, ubiquitous network technology has attracted the attention of many people, ubiquitous network technology means a technology that allows to naturally connect to various networks regardless of time and place.

An example of such a ubiquitous network technology is RFID technology. In general, an RFID system includes a tag attached to an article and a reader having detailed information embedded therein, and a reader reading information of the tag using RF communication. The tag passes the area where the reader is located and transmits the information using RF communication, thus providing a foundation for efficiently managing logistics / distribution such as product distribution, assembly, price change, and sales.

On the other hand, the RFID system is generally implemented through the envelope detection using the Amplitude Shift Keying (ASK) modulation scheme. According to the conventional design scheme, since the bit error rate is reduced, the data recognition rate is low.

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 provides an interference signal removal system capable of stably restoring / processing a tag signal by canceling interference between reception signals or interference between reception signals and noise component signals.

In addition, the present invention provides an interference signal removal system that can efficiently perform the interference signal removal operation by applying a frequency hopping method.

The interference signal removing system according to the present invention generates a plurality of signals by shifting the phase of a received signal based on the interference signal band, compensates the phase of the signals, and combines the phase compensated signals to remove the interference signal. Interference signal cancellation circuit; A phase detecting unit receiving a received signal from the interference signal removing circuit unit and detecting a phase of the received signal to generate a first detection signal according to a phase difference for each frequency band; A first mixer converting the received signal from which the interference signal is removed into an intermediate frequency signal; An interference signal detection circuit unit configured to generate a second detection signal by sensing a power level of the received signal for each channel; And analyzing the second detection signal to identify a channel having interference, and generating a phase compensation control signal according to the first detection signal and transferring the signal to the interference signal canceling circuit unit to generate the interference signal only for the channel where the interference has occurred. It includes a control unit to be removed.

Hereinafter, an interference signal cancellation system according to the present invention will be described in detail with reference to the accompanying drawings. In the embodiment of the present invention, the interference signal removal system is an RFID reader that communicates with a plurality of tags. It is assumed that carrier signals in the MHz band are used.

1 is a block diagram schematically illustrating components of an interference signal cancellation system 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 1, an interference signal removal system 100 according to an exemplary embodiment of the present invention may include a first antenna 105, an interference signal cancellation circuit 110, a low noise amplifier (LNA) 170, and a first filter 180. ), The first mixer 120, the demodulator 125, the controller 130, the phase synchronization circuit 135, the phase detector 140, the interference signal detection circuit 150, and the second antenna 160. It is made to include.

First, referring to FIG. 1, the characteristics of the interference signal removal system 100 according to an exemplary embodiment of the present invention will be described.

The interference signal removing circuit unit 110 shifts the phase of the signal received through the first antenna 105 based on the interference signal band, and compensates and synthesizes the phases of the received signal and the phase shift signal so that only the interference signal is combined. To be removed.

That is, a tag signal and an interference signal are present in the signal received through the first antenna 105. When the phase of the received signal is phase shifted to 180 ° based on the interference signal band, the tag signal is preserved. Only the interference signal has a phase difference of 180 degrees.

Therefore, when the received signal and the phase shift signal are combined, the tag signal is preserved and the interference signal is canceled and disappeared.

In addition, the phase detection unit 140 receives the received signal from the interference signal removing circuit unit 110, detects the phase of the received signal, and generates a first detection signal according to a phase difference for each frequency band. The first detection signal is transmitted to the controller 130, and the controller 130 generates a phase compensation control signal.

The interference signal removing circuit unit 110 compensates and synchronizes a phase of a received signal and a phase shifting signal using a phase compensation control signal. Thus, after the synchronization process, the interference signal may be accurately removed.

Accordingly, the interference signal removing circuit unit 110 and the phase detecting unit 140 may be referred to as components that operate together to remove the interference signal.

On the other hand, the interference signal detection circuit 150 is a kind of LBT (Listen Before Talk) circuit for the interference signal removal operation, when the interference signal detection circuit 150 detects the interference channel, the controller 130 Using the phase compensation control signal, the interference signal removing circuit 110 may control the interference signal removing operation only on the channel where the interference occurs.

That is, according to the phase compensation method, the interference signal mixed with the received signal may be removed or the original received signal may be transmitted to the LNA 170 as it is, and the controller 130 may remove the interference signal by the interference signal detection circuit 150. It is possible to select a channel to perform the.

The interference signal detection circuit unit 150 generates a second detection signal by detecting the power level of the received signal, and transmits the second detection signal to the controller 130.

The controller 130 interprets the second detection signal and determines that an interference signal other than the tag signal exists in the received signal when the power level is equal to or greater than the reference value, and applies the phase compensation control signal to operate the interference signal cancellation circuit 110. To pass.

At this time, the interference signal detection circuit 150 monitors the power level of the received signal while moving the band for each frequency hopping channel.

Hereinafter, each component of the interference signal removal system 100 according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram schematically illustrating the components of the interference signal cancellation circuit unit 110 included in the interference signal removal system 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the interference signal removing circuit unit 110 includes a phase shifting unit 111, a first phase compensating unit 112, a first PA 113, a second PA 114, and a first signal synthesizing unit 116. ), A first coupling unit 115, a second coupling unit 117, a second phase compensation unit 118, and a second signal synthesis unit 119.

The phase shifter 111 phase shifts a phase of a signal received through the first antenna 105 to 180 ° based on a band of an interference signal, a phase shift circuit including a strip line, It can be implemented by a balloon circuit or the like.

3 is a diagram illustrating a form in which the phase shifting unit 111 of the interference signal removing circuit unit 110 included in the interference signal removing system 100 according to the embodiment of the present invention is implemented as a balloon circuit, and FIG. FIG. 9 is a diagram illustrating a form of a signal processed by the interference signal removing circuit unit 110 included in the interference signal removing system 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 3, it can be seen that the phase shifter 111 is implemented as a balloon circuit in which elements such as a capacitor and a resistor are connected in parallel. The received signal having a phase of 0 ° and the phase having a phase of 180 ° Branch the transition signals to different lines.

In an embodiment of the present invention, a reception signal is transmitted to an upper line and a phase shift signal is transmitted to a lower line, and the lower line serves as a main power line.

The phase shift signal is corrected in phase through the first phase compensator 112 (the first phase compensator 112 will be described later in detail together with the second phase compensator 118), and the second PA 114 is used. Is then amplified to meet the synthetic specifications.

The received signal is also transmitted to the first PA 113, amplified, and coupled to the first signal synthesis unit 116 on the first coupling unit 115.

The first signal synthesizing unit 116 may include various signal combining circuits and processes primary signal canceling. That is, the first signal synthesizing unit 116 synthesizes the phase-compensated amplified phase shift signal and the coupled received signal so that the interference signal is first removed.

In the diagram of FIG. 4A, the "a1" signal is a tag signal of a reception signal branched through an upper line, and the "a2" signal is an interference signal (eg, a feedback transmission signal) of a reception signal branched through an upper line. to be. (b) In the figure, the " a1 " signal is a tag signal of a phase shift signal branched through the lower line (the tag signal is not phase shifted and can therefore be regarded as substantially the same signal as the tag signal on the upper line); b " signal is an interference signal of the phase shift signal, and it can be confirmed that only the interference signal " b "

4 (c) shows the result of combining (a) the signal (receive signal) and (b) the signal (phase shift signal) in the figure, and the tag signal is stored as a "c1" signal. And the interference signal "c2" is canceled.

Here, even though the interference signal of the received signal and the interference signal of the phase shift signal are canceled, some interference signal "c2" remains. The remaining interference signal "c2" is completely removed through the second signal synthesis unit 119. Can be.

The received signal after the first synthesis, that is, the tag signal, is compensated for phase through the second phase compensator 118 and transmitted to the second signal synthesizer 119 and passed through the first coupling unit 115. By combining with the tag signal and the interference signal, the remaining interference signal is secondarily removed.

However, since the received signal passing through the first coupling unit 115 and the tag signal passing through the second phase compensating unit 118 are signals of the same phase, an interference signal is not removed when synthesized. A delay line A is formed between 117 and the second signal synthesis unit 119.

The delay line A functions as a kind of phase shifter to shift the phase of the received signal (signal of the upper line) out of phase (the signals "d1" and "d2" shown in FIG. 4 (d)). Therefore, when the signal of the upper line and the signal of the lower line are synthesized on the second signal synthesizing unit 119, only the tag signal remains.

The received signal, that is, the tag signal, from which the interference signal is removed through the above process, is amplified by the low noise on the LNA 170 and filtered by the first filter (which may be provided as a SAW filter) 180.

The filtered tag signal is converted into an intermediate frequency signal through the first mixer 120, and the demodulator 125 including an analog to digital converter (ADC) converts the intermediate frequency signal into a digital signal and then controls the control unit ( 130).

The first mixer 122 and the second mixer 124 of the first mixer 120 are dual mixers, and the first mixer 122 has an intermediate frequency signal I ⁺ signal and I ⁻ having a phase difference of 90 degrees. Signal), and the second mixer 124 synthesizes a Q intermediate frequency signal (Q ⁺ signal and Q ^- signal) having a phase difference of 90 degrees.

Hereinafter, the phase detection unit 140 and the phase compensation function related thereto will be described with reference to FIGS. 5 and 6.

5 is a block diagram schematically illustrating the components of the phase detection unit 140 of the interference signal removing system 100 according to an embodiment of the present invention, and FIG. 6 is an interference signal according to an embodiment of the present invention. FIG. Is a diagram illustrating a phase of a signal sensed by the phase detector 140 configured in the removal system 100.

Referring to FIG. 5, the phase detection unit 140 includes a second mixer 142 and a phase detection circuit 144. The second mixer 142 may include an interference signal cancellation circuit 110. It is connected to the second coupling unit 117, and is connected to the local oscillator (LO; Local Oscillator) included in the phase synchronization circuit unit 135.

The second coupling unit 117 couples the received signal passing through the first coupling unit (a state in which the tag signal and the interference signal are still present) to be transmitted to the second mixer 142 and the second mixer. The unit 142 mixes the coupled signal with the local oscillation signal and converts it into an intermediate frequency signal as shown in FIG.

This conversion to the intermediate frequency signal is because phase detection can be more easily processed than the state of the high frequency signal.

The first coupling unit 115 and the second coupling unit 117 may be provided with a branch line coupler having a good signal separation function, for example.

The phase detection circuit 144 detects a phase between signal components (corresponding to each arrow in FIG. 6) existing on the received signal and codes the first detection signal in a digital state, and the controller 130 controls the first signal. The sensing signal is received to calculate the phase difference between signal components.

The control unit 130 generates a phase compensation control signal for synchronization according to the calculation result and transfers the control signal to the first phase compensation unit 112 and the second phase compensation unit 118 of the interference signal removing circuit unit 110. do.

Accordingly, the first phase compensator 112 and the second phase compensator 118 precisely synchronize the phase between the received reception signal and the phase shift signal, and the interference signals present in the two signals are canceled in the same phase region. Can be.

7 is a block diagram schematically illustrating the components of the interference signal detection circuit unit 150 included in the interference signal removal system 100 according to an exemplary embodiment of the present invention. The attenuator 151, the third mixer 152, a low pass filter (LPF) 153, a channel filter 154, and a log amplifier 155 are included.

The amplifier / attenuator 151 adjusts the power value such that the signal received through the second antenna 160 conforms to the signal processing standard of the log amplifier 155, and the third mixer 152 is a phase synchronization circuit unit ( A local oscillation signal is received from the local oscillation circuit included in 135 and synthesized with the received signal to generate an intermediate frequency signal.

In this case, the interference signal detection circuit unit 150 needs to monitor all 15 frequency channels of the received signal. Therefore, the controller 130 controls the phase synchronization circuit unit 135 to differentiate the local oscillation signal for each frequency channel. To be supplied.

As the local oscillation signal is differentiated for each frequency channel, the third mixer 152 may generate an intermediate frequency signal corresponding to 15 frequency channels allocated at 900 KHz intervals from 900 MHz, for example.

The LPF 153 filters the mixed noise component in the mixing process, and the channel filter 153 filters each received signal transmitted for each frequency channel based on, for example, 200 KHz band.

The log amplifier 155 outputs the filtered intermediate frequency signal as a second detection signal in a state where a power level can be detected, that is, a DC voltage state, and outputs the intermediate frequency signal as a DC voltage signal directly proportional to the decibel value. This extends the signal sensitivity range of the power levels that can be received.

The second detection signal transmitted from the log amplifier 155 is transmitted to the control unit 130, and the control unit 130 determines the power level of the second detection signal to determine the existence of the interference signal and the degree of the interference phenomenon. .

As described above, when it is determined that an interference signal exists in a received signal of a predetermined channel, the controller 130 transmits a phase compensation control signal (for synchronization) to the first phase compensator 112 and the second phase compensator 118. To remove the interference signal.

However, if it is determined that the interference signal does not exist in the received signal of the predetermined channel, the phase compensation control signal is transmitted (to invert the received signal which is out of phase with respect to the interference signal band again), and the original received signal remains as it is. It may be maintained to pass through the interference signal removing circuit unit 110.

The controller 130 includes a communication protocol to control wireless communication with a tag, interprets a digital signal, and stores tag information in a memory to manage the communication.

In addition, the controller 130 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 130 may be implemented using a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit.

Although the present invention has been described above with reference to the embodiments, these are only examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains may have an abnormality within the scope not departing from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not illustrated. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

According to the interference signal removing system according to the present invention, since the interference signal can be accurately differentiated based on the band of the interference signal and the phase can be corrected, only the interference signal can be accurately removed, so that the received signal can be stably restored / processed and communicated. There is an effect that communication can be performed without interference between systems.

Further, according to the present invention, the interference circuit can be accurately identified through the sensing circuit and the interference signal cancellation operation is performed only on the interference generated channel, thereby saving operator's resources and improving signal resolution.

In addition, according to the present invention, when using a plurality of communication systems using the same channel or adjacent channels, the degree of freedom of arrangement of the system is secured, and it is not necessary to provide a complicated control system to control the plurality of communication systems. There is.

Claims (12)

An interference signal removing circuit unit for generating a plurality of signals by shifting a phase of a received signal based on an interference signal band, compensating for the phases of the signals, and combining the phase compensated signals to remove the interference signal; A phase detecting unit receiving a received signal from the interference signal removing circuit unit and detecting a phase of the received signal to generate a first detection signal according to a phase difference for each frequency band; A first mixer converting the received signal from which the interference signal is removed into an intermediate frequency signal; An interference signal detection circuit unit configured to generate a second detection signal by sensing a power level of the received signal for each channel; And Analyze the second detection signal to identify the channel in which the interference has occurred, generate a phase compensation control signal according to the first detection signal, and transmit it to the interference signal removing circuit to remove the interference signal only for the channel where the interference has occurred. Interference signal removal system comprising a control unit to make. The method of claim 1, wherein the interference signal cancellation circuit unit A phase shifter for shifting the phase of the received signal and branching the received signal and the phase shift signal to different lines; And A coupling unit for coupling the received signal or phase shift signal from a corresponding line; And And a first signal synthesizing unit which combines the coupled signal with a signal of another line having an antiphase to generate a signal from which an interference signal is removed. The method of claim 2, And a phase compensator coupled between the phase shifter and the first signal synthesizer and compensating a phase between the received signal and the phase shift signal by the phase compensation control signal. The method of claim 2, At least one power amplifier connected to the branch line of the phase shifter. The method of claim 2, And a second signal synthesizing unit configured to synthesize the signal passing through the coupling unit and the output signal of the first signal synthesizing unit to generate a signal from which residual interference signals are removed. The method of claim 5, A second phase compensation connected between the first signal synthesizing unit and the second signal synthesizing unit and compensating for a phase of a signal passing through the coupling unit and an output signal of the first signal synthesizing unit according to the phase compensation control signal; Interference signal cancellation system comprising a. The method of claim 1, The interference signal cancellation circuit unit includes a coupling unit for coupling a received signal, The phase detector includes a second mixer converting the coupled received signal into an intermediate frequency signal; And a phase detection circuit for sensing a phase of the intermediate frequency signal and generating a detection signal according to a phase difference for each frequency band. The method of claim 1, wherein the interference signal cancellation circuit unit And a phase shift signal having a phase difference of 180 ° with the received signal based on the interference signal band. The method of claim 1, And the controller controls the first mixer to process frequency hopping as the channel where the interference occurs is identified. The method of claim 1, wherein the interference signal detection circuit unit A third mixer converting the received signal into an intermediate frequency signal; And And an amplifier unit for converting the power level of the intermediate frequency signal into a detection signal in a DC signal state. The method of claim 10, wherein the control unit And controlling the third mixer to generate the detection signal for each frequency hopping channel. The method of claim 10, And a channel filter connected between the third mixer and the amplifier.

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