CN104123571A - Carrier wave offset circuit based on RFID reader-writer, and RFID reader-writer - Google Patents
Carrier wave offset circuit based on RFID reader-writer, and RFID reader-writer Download PDFInfo
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Abstract
The invention is applicable to the field of circuits and particularly relates to a carrier wave offset circuit based on an RFID reader-writer and the RFID reader-writer. In a work process of the RFID reader-writer, a controller adjusts the impedance of an impedance conversion circuit so as to adjust reception signals received by a demodulator. When a power detected by a power detector is lowest, it is represented that an offset effect of reflection signals of the impedance conversion circuit on leakage carrier wave signals are optimal so that it is easier for the demodulator to demodulate correct tag signals.
Description
Technical field
The invention belongs to circuit field, relate in particular to a kind of carrier cancellation circuit and rfid interrogator based on rfid interrogator.
Background technology
As everyone knows, in the course of work of ultrahigh frequency radio frequency identification (RFID) reader, electronic tag is in read write line return signal process, and read write line also needs to launch carrier signal and provides energy to electronic tag.Because the carrier signal of read write line transmitting is very strong, inevitably have portion of carriers signals leakiness to receiving cable, the carrier signal that this part leakage is come is much larger than the return signal of label, thereby causes the receiving sensitivity decline of read write line.In order to overcome this problem, in super high frequency technique field, there is carrier cancellation technology in recent years.Side's ratio juris is to produce a signal equal with leakage carrier amplitude, single spin-echo to be added with leaking carrier phasor, and the interference of carrier signal is even eliminated in weakening, and the signal that label is returned does not exert an influence.The course of work of the method is after to be carrier signal amplify through power amplifier (Power Amplifier, PA), by directional coupler, is coupled the signal of a part of power as the source signal of offseting signal.This source signal is input to Vector Modulation circuit, and Vector Modulation circuit is adjusted the amplitude of input signal and phase place, and generation equates with leakage carrier amplitude, the offseting signal of single spin-echo.The receiving end signal of offseting signal and isolator is added by combiner, and then the carrier signal that weakens and stop a leak is input to demodulator circuit and microcontroller, obtains label data.
Carrier cancellation circuit design scheme above-mentioned is on traditional ultrahigh frequency radio frequency identification (RFID) reader scheme basis, adds the circuit such as Vector Modulation circuit, combiner and isolator.The implementation of the Vector Modulation circuit in this circuit design scheme mainly contains two, and the first is used existing Vector Modulation chip, and it two is to use traditional Vector Modulation circuit; The former shortcoming is that Vector Modulation chip price is more expensive, and single-chip price all will be added combiner and isolator more than hundred yuan, has seriously increased design cost, and traditional Vector Modulation circuit is realized comparatively complexity, and Vector Modulation effect is not obvious again.On the other hand, Vector Modulation algorithm is more complicated also, needs I, Q two-way simulating signal to control simultaneously.The interference of carrier wave so although this design proposal can weaken and stop a leak, there is the shortcoming that cost of hardware design is high, hardware design difficulty is large, software control algorithm is more complicated, debugging difficulty is large in global design, and be not suitable for batch production.
Summary of the invention
The object of the present invention is to provide a kind of carrier cancellation circuit based on rfid interrogator, aim to provide a kind of carrier cancellation circuit based on ultrahigh frequency radio frequency identification (RFID) reader, this carrier cancellation circuit, by changing impedance to reduce or eliminate the impact of leaking carrier wave, demodulates label signal.
The present invention realizes like this, a kind of carrier cancellation circuit based on rfid interrogator, the described carrier cancellation circuit based on rfid interrogator comprises for generating the modulation circuit of carrier signal, the described carrier cancellation circuit external antenna based on rfid interrogator, the described carrier cancellation circuit based on rfid interrogator also comprises:
Be connected with described modulation circuit and there is go side always, for described carrier signal is sent to the directional coupler of described antenna from described straight-through end;
Be connected with the isolation end of described directional coupler, for the isolation end from described directional coupler, obtain reception signal, and from the detuner of described receiving signal demodulation outgoing label signal;
Be connected with the input end coupling of described detuner, for the part signal being coupled to from described reception signal being carried out to the power detector of power detection;
Be connected with described detuner and described power detector, for receiving described label signal, adjust the microcontroller of the impedance of impedance inverter circuit; And
The impedance inverter circuit being connected with described microcontroller with the coupled end of described directional coupler respectively.
The present invention also provides a kind of rfid interrogator, and described rfid interrogator comprises the above-mentioned carrier cancellation circuit based on rfid interrogator.
In the present invention, in rfid interrogator, controller is adjusted the impedance of impedance inverter circuit, the reception signal receiving to adjust detuner, the power detecting when power detector is for hour, represent that the reflected signal of this impedance inverter circuit is to leaking neutralization effect the best of carrier signal, thereby detuner more easily demodulates correct label signal.
Accompanying drawing explanation
Fig. 1 is the circuit structure diagram of the carrier cancellation circuit based on rfid interrogator that provides of the embodiment of the present invention;
The circuit diagram of a kind of impedance inverter circuit in the carrier cancellation circuit based on rfid interrogator that Fig. 2 provides for the embodiment of the present invention;
The circuit diagram of the another kind of impedance inverter circuit in the carrier cancellation circuit based on rfid interrogator that Fig. 3 provides for the embodiment of the present invention;
Fig. 4 is the physical circuit figure of the carrier cancellation circuit based on rfid interrogator based on impedance inverter circuit described in Fig. 3 that provides of the embodiment of the present invention;
Fig. 5 is after the impedance of the one-period of the impedance inverter circuit that provides of the embodiment of the present invention is adjusted, the cycle traversal trajectory diagram of the reflected signal of impedance inverter circuit.
Embodiment
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.
Fig. 1 shows the structure of the carrier cancellation circuit based on rfid interrogator that the embodiment of the present invention provides, and for convenience of explanation, only shows the part relevant to the embodiment of the present invention, and details are as follows.
A kind of carrier cancellation circuit based on rfid interrogator, the described carrier cancellation circuit based on rfid interrogator comprises for generating the modulation circuit of carrier signal, the described carrier cancellation circuit external antenna based on rfid interrogator, the described carrier cancellation circuit based on rfid interrogator also comprises:
Be connected with described modulation circuit and there is go side always, for described carrier signal is sent to the directional coupler 2 of described antenna from described straight-through end;
Be connected with the isolation end of described directional coupler 2, for the isolation end from described directional coupler 2, obtain reception signal, and from the detuner of described receiving signal demodulation outgoing label signal;
Be connected with the input end coupling of described detuner, for the part signal being coupled to from described reception signal being carried out to the power detector 3 of power detection;
Be connected with described detuner and described power detector 3, for receiving described label signal, adjust the microcontroller 4 of the impedance of impedance inverter circuit 1; And
The impedance inverter circuit 1 being connected with described microcontroller 4 with the coupled end of described directional coupler 2 respectively.
As one embodiment of the invention, if when impedance inverter circuit 1 adopts the variable capacitance of numeral adjustment to adjust impedance, can directly connect described microcontroller 4 and impedance inverter circuit 1.
As another embodiment of the present invention, when if impedance inverter circuit 1 adopts the variable capacitance of simulation adjustment to adjust impedance, also need between described microcontroller 4 and impedance inverter circuit 1, add D/A, this digital to analog converter is for the digital signal of described microcontroller 4 outputs is converted to simulating signal, with control group translation circuit 1.
As one embodiment of the invention, described carrier cancellation circuit also comprises:
Be connected to the power amplifier 7 between the output terminal of described modulation circuit and the input end of described directional coupler 2.
Fig. 2 shows the circuit of a kind of impedance inverter circuit 1 in the carrier cancellation circuit based on rfid interrogator that the embodiment of the present invention provides, and for convenience of explanation, only shows the part relevant to the embodiment of the present invention, and details are as follows.
As another embodiment of the present invention, described impedance inverter circuit 1 comprises:
Variable capacitance C1, variable capacitance C2, variable capacitance C3, filter capacitor C4, filter capacitor C5, filter inductance L1, filter inductance L2, filter inductance L3 and resistance R 1;
The first end of described variable capacitance C1 and the second end connect respectively coupled end and the ground of described directional coupler 2, described filter inductance L1 is in parallel with described variable capacitance C1, described variable capacitance C2, described filter capacitor C4 are connected between the first end of described variable capacitance C1 and the first end of described filter inductance L2 respectively, the first end of filter capacitor C5 described in the second termination of described filter inductance L2, described variable capacitance C3, described filter inductance L3, described resistance R 1 are all connected between the first end and ground of described filter capacitor C5.
By adjusting the electric capacity of variable capacitance C1, variable capacitance C2, variable capacitance C3, adjust the impedance of impedance inverter circuit 1.
Fig. 3 shows the circuit of another impedance inverter circuit 1 in the carrier cancellation circuit based on rfid interrogator that the embodiment of the present invention provides, and for convenience of explanation, only shows the part relevant to the embodiment of the present invention, and details are as follows.
As one embodiment of the invention, described impedance inverter circuit 1 comprises:
The first tunable capacitor chip U1, the second tunable capacitor chip U2, the 3rd tunable capacitor chip U3, filter capacitor C31, filter capacitor C32, filter capacitor C33, filter inductance L34, filter inductance L35, filter inductance L36, resistance R 37 and resistance R 38;
The first end of described filter inductance L34 is the impedance transformation pin RF_F of described impedance inverter circuit 1, described impedance transformation pin RF_F connects the coupled end of described directional coupler 2, the second end ground connection of described filter inductance L34, the clock pin SCL of described the first tunable capacitor chip U1, data pin SDA, strobe pin SEN_A connects respectively described microcontroller 4, the anodal capacitor pin RF+ of described the first tunable capacitor chip U1, negative pole capacitor pin RF-connects respectively the first end of described filter inductance L34, ground, the clock pin SCL of described the second tunable capacitor chip U2, data pin SDA, strobe pin SEN_B connects respectively described microcontroller 4, the anodal capacitor pin RF+ of described the second tunable capacitor chip U2, negative pole capacitor pin RF-connects respectively the first end of described filter inductance L34, the first end of described filter inductance L35, described filter capacitor C31 is connected between the anodal capacitor pin RF+ and negative pole capacitor pin RF-of described the second tunable capacitor chip U2, described filter capacitor C32 is connected between the second end of described filter inductance L35 and the first end of described filter inductance L36, the clock pin SCL of described the 3rd tunable capacitor chip U3, data pin SDA, strobe pin SEN_C connects respectively described microcontroller 4, the anodal capacitor pin RF+ of described the 3rd tunable capacitor chip U3, negative pole capacitor pin RF-connects respectively the first end of described filter inductance L36, ground, described resistance R 37 is in parallel with described filter inductance L36, described filter capacitor C33 is connected between the first end of described filter inductance L36 and the first end of described resistance R 38, the second end of described filter inductance L36, the equal ground connection of the second end of described resistance R 38.
It should be noted that, by the first tunable capacitor chip U1, the second tunable capacitor chip U2, the 3rd tunable capacitor chip U3, adjust the impedance of impedance inverter circuit 1.
In conjunction with Fig. 3, Fig. 4 shows the physical circuit of the carrier cancellation circuit based on rfid interrogator that the embodiment of the present invention provides, and for convenience of explanation, only shows the part relevant to the embodiment of the present invention, and details are as follows.
As one embodiment of the invention, described carrier cancellation circuit also comprises:
Be connected with the output terminal of described power amplifier 7, the input end of described directional coupler 2 respectively, for leaching the filtering circuit 5 of carrier signal, described filtering circuit 5 comprises:
Filter capacitor C41, filter capacitor C42, filter capacitor C43, filter inductance L48 and filtering chip U4;
The first end of described filter capacitor C41, the second end connect respectively described power amplifier 7 output terminal,, described filter inductance L48 is connected between the first end of described filter capacitor C41 and the first end of described filter capacitor C42, the second end ground connection of described filter capacitor C42, described filter capacitor C43 is connected between the first end of described filter capacitor C42 and the filtering input pin RF_IN of described filtering chip U4, and the filtering output pin RF_OUT of described filtering chip U4 connects the input end of described directional coupler 2.
As one embodiment of the invention, described directional coupler 2 comprises:
Capacitance C44, capacitance C45 and the first directional couple chip U6;
The first end of described capacitance C44, the second end meet respectively the filtering output pin RF_OUT of described filtering chip U4, the carrier wave input pin IN of described the first directional couple chip U6, the straight-through pin DIR of described the first directional couple chip U6, coupling pin COU, isolation pin ISO connect respectively the second end of antenna, described capacitance C45, described demodulator circuit, impedance transformation pin RF_F described in the first termination of described capacitance C45.
As one embodiment of the invention, described carrier cancellation circuit also comprises:
Be connected with the isolation end of described directional coupler 2, the input end of described power detector 3 respectively, for receiving the coupled circuit 6 of signal described in coupling unit, described coupled circuit 6 comprises:
Capacitance C46, capacitance C47, shunt resistance R49, shunt resistance R50 and the second directional couple chip U5;
The first end of described capacitance C46, the second end meets respectively the isolation pin ISO of described the first directional couple chip U6, the coupling input pin of described the second directional couple chip U5, the straight-through output pin DIR of described the second directional couple chip U5, power coupling pin COU, power isolation pin ISO connects respectively the second end of described capacitance C47, the first end of described shunt resistance R49, the first end of described shunt resistance R50, detuner described in the first termination of described capacitance C47, the second end ground connection of described shunt resistance R50, power detector 3 described in the second termination of described shunt resistance R49.
As one embodiment of the invention, described power detector 3 comprises:
Divider resistance R51 and power detection chip U8;
Described divider resistance R51 is connected between the second end and ground of described shunt resistance R49, and the detection input pin P_IN of described power detection chip U8, detection output pin P_OUT connect respectively the second end, the microcontroller 4 of described shunt resistance R49.
As one embodiment of the invention, described microcontroller 4 comprises:
Microcontroller chip U7;
The clock pin SCL of described microcontroller chip U7 meets respectively the clock pin SCL of described the first tunable capacitor chip U1, the clock pin SCL of the second tunable capacitor chip U2, the clock pin SCL of the 3rd tunable capacitor chip U3, the data pin SDA of described microcontroller chip U7 meets respectively the data pin SDA of described the first tunable capacitor chip U1, the data pin SDA of the second tunable capacitor chip U2, the data pin SDA of the 3rd tunable capacitor chip U3, the first strobe pin SEN_A of described microcontroller chip U7, the second strobe pin SEN_B, the 3rd strobe pin SEN_C, restituted signal pin DEM and power detection pin ADC meet respectively the strobe pin SEN_A of described the first tunable capacitor chip U1, the strobe pin SEN_B of the second tunable capacitor chip U2, the strobe pin SEN_C of the 3rd tunable capacitor chip U3, the output terminal of described detuner, the detection output pin P_OUT of described power detection chip U8.
In order to explain better the present invention, in conjunction with Fig. 3, Fig. 4, with the first tunable capacitor chip U1, adopt the first tunable capacitor chip PE64904, the second tunable capacitor chip U2 adopts the second tunable capacitor chip PE64904, the 3rd tunable capacitor chip U3 adopts the 3rd tunable capacitor chip PE64904, the first directional couple chip U6 adopts the first directional couple chip DC0900A05, the second directional couple chip U5 adopts the second directional couple chip HHM2602, it is example that power detection chip U8 adopts power detection chip MAX4003, the principle of work of the carrier cancellation circuit of explanation based on rfid interrogator:
Modulation circuit generates carrier signal, this carrier signal is carried out power amplification through power amplifier 7PA, and by the carrier signal after power amplification, the carrier signal input pin IN by the first directional couple chip DC0900A05 is input to the first directional couple chip DC0900A05 to PA.In the first directional couple chip DC0900A05, straight-through pin DIR, antenna by the first directional couple chip DC0900A05 send carrier signal, meanwhile, the coupling pin COU by the first directional couple chip DC0900A05 is to the carrier signal of impedance inverter circuit 1 transmitting portion coupling; In addition, also has partial carrier wave leakage signal to the isolation pin ISO of the first directional couple chip DC0900A05, simultaneously, impedance Incomplete matching due to antenna end, partial carrier wave signal reflex is returned, the reflected signal reflecting is coupled to the isolation pin ISO of the first directional couple chip DC0900A05, and carrier signal and described reflected signal that part is leaked to the isolation pin ISO of the first directional couple chip DC0900A05 form leakage carrier signal.This leakage carrier signal, antenna reception to the reflected signal of the feedback signal that comprises label signal, impedance inverter circuit form and receive signal, this reception signal is exported by the isolation pin ISO of the first directional couple chip DC0900A05.
More optimizedly, between power amplifier 7 and the carrier signal input pin IN of the first directional couple chip DC0900A05, introduced filtering circuit 5, the low-pass filter that the filter capacitor C41 comprising by this filtering circuit 5, filter capacitor C42, filter capacitor C43, filter inductance L48 and filtering chip U4 form, has the effect every straight and low-pass filtering.
Detuner carries out demodulation to the reception signal receiving, to obtain label signal; The label signal of the restituted signal pin DEM receiving demodulation device output of microcontroller chip U7.
More optimizedly, between detuner and the isolation pin ISO of the first directional couple chip DC0900A05, introduced coupled circuit 6, the straight-through output pin DIR of the second directional couple chip HHM2602 comprising by this coupled circuit 6 inputs most reception signal to detuner, simultaneously, power coupling pin COU by the second directional couple chip HHM2602 provides part to receive signal to the detection input pin P_IN of power detection chip MAX4003, with power detection chip MAX4003, detect that this part receives the power of signal and the power detection pin ADC to microcontroller chip U7 with the formatted output of analog voltage signal.
The first directional couple chip DC0900A05 is the carrier signal to impedance inverter circuit 1 transmitting portion coupling by coupling pin COU; Microcontroller chip U7 controls choosing of the first tunable capacitor chip PE64904, the second tunable capacitor chip PE64904, the 3rd tunable capacitor chip PE64904 by the first strobe pin SEN_A, the second strobe pin SEN_B, the 3rd strobe pin SEN_C, by data pin SDA, send electric capacity and adjust signal, tunable capacitor chip selected in the first tunable capacitor chip PE64904, the second tunable capacitor chip PE64904, the 3rd tunable capacitor chip PE64904 is adjusted electric capacity, to adjust the impedance of impedance inverter circuit 1; Thereby the amplitude of the carrier signal of the partial coupling of adjustment impedance inverter circuit 1 reflection and phase place are with the reflected signal of feedback impedance translation circuit.Meanwhile, the analog voltage signal of the power detection pin ADC received power detection chip MAX4003 of microcontroller chip U7 output; By that analogy, microcontroller chip U7 controls the electric capacity adjustment of the first tunable capacitor chip PE64904, the second tunable capacitor chip PE64904, the 3rd tunable capacitor chip PE64904, to complete the impedance adjustment (comprising amplitude and phase place) of the impedance inverter circuit 1 of one-period, to change the reflected signal of impedance inverter circuit, meanwhile, the power detection pin ADC received power detection chip MAX4003 of microcontroller chip U7 is at the analog voltage signal of this cycle output; Finally, microcontroller chip U7 controls the first tunable capacitor chip PE64904, the second tunable capacitor chip PE64904, the 3rd tunable capacitor chip PE64904 adjusts electric capacity, take and reaches the minimum value of the analog voltage signal that analog voltage signal that the power detection pin ADC of microcontroller chip U7 receives exports for this cycle.For example: after the impedance that Fig. 5 shows the one-period of impedance inverter circuit 1 is adjusted, the amplitude of the reflected signal of impedance inverter circuit and phase place, in Fig. 5, suppose that b point is for revealing carrier signal, the impedance of adjusting impedance inverter circuit 1 is usingd and is selected e point as the reflected signal of impedance inverter circuit; Thereby, the reflected signal of the impedance inverter circuit that e is ordered can be the largest ground, offset the leakage carrier signal that b is ordered even fully, then, detuner demodulates label signal the most accurately.More optimizedly, allow in advance rfid interrogator away from electronic tag, so that electronic tag does not have feedback to comprise the feedback signal of label signal, to complete the impedance adjustment of the one-period of impedance inverter circuit 1, the power detection pin ADC of microcontroller chip U7 receives analog voltage signal this cycle, power detection chip MAX4003 output, finds out the impedance of the minimum value of analog voltage signal and the impedance inverter circuit 1 of correspondence of this cycle output; Thereby, when follow-up detuner demodulated received signal, can more easily demodulate correct label signal.
As another embodiment of the present invention, the present invention also provides a kind of rfid interrogator, and described rfid interrogator comprises the above-mentioned carrier cancellation circuit based on rfid interrogator.
In embodiments of the present invention, in rfid interrogator, by controller, adjust the impedance of impedance inverter circuit, to adjust the reflected signal of impedance inverter circuit, the reflected signal of this impedance inverter circuit is used for offsetting leakage carrier signal, thereby detuner more easily demodulates correct label signal.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any modifications of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.
Claims (10)
1. the carrier cancellation circuit based on rfid interrogator, the described carrier cancellation circuit based on rfid interrogator comprises for generating the modulation circuit of carrier signal, the described carrier cancellation circuit external antenna based on rfid interrogator, it is characterized in that, the described carrier cancellation circuit based on rfid interrogator also comprises:
Be connected with described modulation circuit and there is go side always, for described carrier signal is sent to the directional coupler of described antenna from described straight-through end;
Be connected with the isolation end of described directional coupler, for the isolation end from described directional coupler, obtain reception signal, and from the detuner of described receiving signal demodulation outgoing label signal;
Be connected with the input end coupling of described detuner, for the part signal being coupled to from described reception signal being carried out to the power detector of power detection;
Be connected with described detuner and described power detector, for receiving described label signal, adjust the microcontroller of the impedance of impedance inverter circuit; And
The impedance inverter circuit being connected with described microcontroller with the coupled end of described directional coupler respectively.
2. the carrier cancellation circuit based on rfid interrogator as claimed in claim 1, is characterized in that, described carrier cancellation circuit also comprises:
Be connected to the power amplifier between the output terminal of described modulation circuit and the input end of described directional coupler.
3. the carrier cancellation circuit based on rfid interrogator as claimed in claim 1, is characterized in that, described impedance inverter circuit comprises:
Variable capacitance C1, variable capacitance C2, variable capacitance C3, filter capacitor C4, filter capacitor C5, filter inductance L1, filter inductance L2, filter inductance L3 and resistance R 1;
The first end of described variable capacitance C1 and the second end connect respectively coupled end and the ground of described directional coupler, described filter inductance L1 is in parallel with described variable capacitance C1, described variable capacitance C2, described filter capacitor C4 are connected between the first end of described variable capacitance C1 and the first end of described filter inductance L2 respectively, the first end of filter capacitor C5 described in the second termination of described filter inductance L2, described variable capacitance C3, described filter inductance L3, described resistance R 1 are all connected between the first end and ground of described filter capacitor C5.
4. the carrier cancellation circuit based on rfid interrogator as claimed in claim 2, is characterized in that, described impedance inverter circuit comprises:
The first tunable capacitor chip U1, the second tunable capacitor chip U2, the 3rd tunable capacitor chip U3, filter capacitor C31, filter capacitor C32, filter capacitor C33, filter inductance L34, filter inductance L35, filter inductance L36, resistance R 37 and resistance R 38;
The first end of described filter inductance L34 is the impedance transformation pin (RF_F) of described impedance inverter circuit, described impedance transformation pin (RF_F) connects the coupled end of described directional coupler, the second end ground connection of described filter inductance L34, the clock pin of described the first tunable capacitor chip U1, data pin, strobe pin connects respectively described microcontroller, the anodal capacitor pin of described the first tunable capacitor chip U1, negative pole capacitor pin connects respectively the first end of described filter inductance L34, ground, the clock pin of described the second tunable capacitor chip U2, data pin, strobe pin connects respectively described microcontroller, the anodal capacitor pin of described the second tunable capacitor chip U2, negative pole capacitor pin connects respectively the first end of described filter inductance L34, the first end of described filter inductance L35, described filter capacitor C31 is connected between the anodal capacitor pin and negative pole capacitor pin of described the second tunable capacitor chip U2, described filter capacitor C32 is connected between the second end of described filter inductance L35 and the first end of described filter inductance L36, the clock pin of described the 3rd tunable capacitor chip U3, data pin, strobe pin connects respectively described microcontroller, the anodal capacitor pin of described the 3rd tunable capacitor chip U3, negative pole capacitor pin connects respectively the first end of described filter inductance L36, ground, described resistance R 37 is in parallel with described filter inductance L36, described filter capacitor C33 is connected between the first end of described filter inductance L36 and the first end of described resistance R 38, the second end of described filter inductance L36, the equal ground connection of the second end of described resistance R 38.
5. the carrier cancellation circuit based on rfid interrogator as claimed in claim 4, is characterized in that, described carrier cancellation circuit also comprises:
Be connected with the output terminal of described power amplifier, the input end of described directional coupler respectively, for leaching the filtering circuit of carrier signal, described filtering circuit comprises:
Filter capacitor C41, filter capacitor C42, filter capacitor C43, filter inductance L48 and filtering chip U4;
The first end of described filter capacitor C41, the second end connect respectively described power amplifier output terminal,, described filter inductance L48 is connected between the first end of described filter capacitor C41 and the first end of described filter capacitor C42, the second end ground connection of described filter capacitor C42, described filter capacitor C43 is connected between the first end of described filter capacitor C42 and the filtering input pin of described filtering chip U4, and the filtering output pin of described filtering chip U4 connects the input end of described directional coupler.
6. the carrier cancellation circuit based on rfid interrogator as claimed in claim 5, is characterized in that, described directional coupler comprises:
Capacitance C44, capacitance C45 and the first directional couple chip U6;
The first end of described capacitance C44, the second end connect respectively the filtering output pin of described filtering chip U4, the carrier wave input pin of described the first directional couple chip U6, the straight-through pin of described the first directional couple chip U6, coupling pin, isolation pin connect respectively the second end of antenna, described capacitance C45, described demodulator circuit, impedance transformation pin (RF_F) described in the first termination of described capacitance C45.
7. the carrier cancellation circuit based on rfid interrogator as claimed in claim 6, is characterized in that, described carrier cancellation circuit also comprises:
Be connected with the isolation end of described directional coupler, the input end of described power detector respectively, for receiving the coupled circuit of signal described in coupling unit, described coupled circuit comprises:
Capacitance C46, capacitance C47, shunt resistance R49, shunt resistance R50 and the second directional couple chip U5;
The first end of described capacitance C46, the second end connects respectively the isolation pin of described the first directional couple chip U6, the coupling input pin of described the second directional couple chip U5, the straight-through output pin of described the second directional couple chip U5, power coupling pin, power isolation pin connects respectively the second end of described capacitance C47, the first end of described shunt resistance R49, the first end of described shunt resistance R50, detuner described in the first termination of described capacitance C47, the second end ground connection of described shunt resistance R50, power detector described in the second termination of described shunt resistance R49.
8. the carrier cancellation circuit based on rfid interrogator as claimed in claim 7, is characterized in that, described power detector comprises:
Divider resistance R51 and power detection chip U8;
Described divider resistance R51 is connected between the second end and ground of described shunt resistance R49, and the detection input pin of described power detection chip U8, detection output pin connect respectively the second end, the microcontroller of described shunt resistance R49.
9. the carrier cancellation circuit based on rfid interrogator as claimed in claim 8, is characterized in that, described microcontroller comprises:
Microcontroller chip U7;
The clock pin of described microcontroller chip U7 connects respectively the clock pin of described the first tunable capacitor chip U1, the clock pin of the second tunable capacitor chip U2, the clock pin of the 3rd tunable capacitor chip U3, the data pin of described microcontroller chip U7 connects respectively the data pin of described the first tunable capacitor chip U1, the data pin of the second tunable capacitor chip U2, the data pin of the 3rd tunable capacitor chip U3, the first strobe pin of described microcontroller chip U7, the second strobe pin, the 3rd strobe pin, restituted signal pin and power detection pin connect respectively the strobe pin of described the first tunable capacitor chip U1, the strobe pin of the second tunable capacitor chip U2, the strobe pin of the 3rd tunable capacitor chip U3, the output terminal of described detuner, the detection output pin of described power detection chip U8.
10. a rfid interrogator, is characterized in that, described rfid interrogator comprises that claim 1 is to the arbitrary described carrier cancellation circuit based on rfid interrogator of claim 9.
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| CN201310143262.9A CN104123571B (en) | 2013-04-23 | 2013-04-23 | A kind of carrier cancellation circuit and RFID reader based on RFID reader |
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| CN201310143262.9A CN104123571B (en) | 2013-04-23 | 2013-04-23 | A kind of carrier cancellation circuit and RFID reader based on RFID reader |
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| CN104123571B CN104123571B (en) | 2017-09-08 |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106710042A (en) * | 2016-12-20 | 2017-05-24 | 盐城工学院 | Detection system and method based on FRID |
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| CN109583252A (en) * | 2018-11-01 | 2019-04-05 | 锐捷网络股份有限公司 | A kind of carrier cancellation circuit and RFID reader |
| CN116566342A (en) * | 2023-05-19 | 2023-08-08 | 深圳飞骧科技股份有限公司 | Self-adaptive impedance adjusting circuit |
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