(2) background technology:
RFID is a REID, and it is a kind of contactless automatic identification technology, and its ultimate principle is to utilize radiofrequency signal and space coupling and transport property, realizes the automatic identification to static or mobile object.Radio-frequency recognition system generally partly is made up of electronic tag, read write line, antenna and main frame etc.The data message of storage destination object in the electronic tag.During system works, read write line is by the radio frequency interface radiated electromagnetic wave, enter the magnetic field of read write line when electronic tag after, receive the radiofrequency signal of read write line, sending out the product information that is stored in the chip by means of the energy that induction current obtained (is Passive Tag, passive label or passive label), the signal that perhaps initiatively sends a certain frequency (is Active Tag, active label or active tag), read write line receives, after reading information and decoding, deliver to CIS and carry out the related data processing, realize the noncontact of electronic tag is read, reach automatic recognition objective object, and obtain the purpose of related data.Reading while write device can also carry out write operation to electronic tag under the control of main frame, rewrite the information that is stored in the label.According to employed electromagnetic wave frequency range, the RFID technology is divided into low frequency (LF), high frequency (HF), ultrahigh frequency (UHF) three classes.Wherein, super high frequency technique has advantages such as decipherment distance is far away, recognition speed is fast, can discern high-speed moving target, data capacity is big, is more suitable for the application in following logistics and supply chain field.
Existing ultrahigh frequency radio frequency identification (RFID) reader " Guangxi Technical College's journal " the 18th volume disclosed a kind of uhf band radio-frequency identification reader/writer of the 1st phase as publishing in March, 2007, mainly form by antenna, radio-frequency module, main control module three parts, radio-frequency module comprises signal isolating device, transmitter unit and receiving element, and main control module comprises that microcontroller is an external interface.At first, because the work of existing read write line is to utilize the backscattered modulation principle, in the overlay area of entire antenna, environmental structure varies, and static is all changing at any time with the object that moves, and there is different phase shifts in the signal that the electronic tag of being read reflexes to read write line, the signal weakening that causes read write line to receive, cause the decipherment distance shortening and the identification angle of read write line to diminish, effectively decipherment distance is only 5~6 meters, and performance is had a greatly reduced quality.Secondly, when two pulse signals very near the time, have and miss one or more possibility, cause the calcellation of putting in order string data easily.Therefore existing read write line adopts one-channel signal to handle mostly, and timesharing realizes the demodulation of 0 ° and 90 ° signal, and there is the not high situation of success ratio equally in this label card for sports type.Even some read write lines have on the market adopted the two-way signal Processing, can solve the problem of loss of data to a certain extent, but all need be on the basis of original single-chip microcomputer, increasing the signal digital treatment facility can realize, so not only make the structure of read write line become complicated, also correspondingly increased the production cost of read write line.
(3) utility model content:
Technical problem to be solved in the utility model provides a kind of decipherment distance ultrahigh frequency RFID label reader-writer far away, simple in structure, lower-cost.
In order to address the above problem, the ultrahigh frequency RFID label reader-writer that the utility model is designed, mainly constitute by control module, transmitter module, receiver module, baseband processing module, the controlled module controls of transmitter module, for read write line provides carrier signal, and export electronic tag to after carrier signal handled, simultaneously, receive the reflected signal that electronic tag returns, be input to receiver module; The reflected signal that receiver module returns electronic tag carries out the direct down coversion demodulation of zero intermediate frequency, realizes the two-way quadrature decoder, output two-way baseband signal; After baseband processing module carries out signal Processing to the two-way baseband signal, the accessible useful signal of controlled module; Control module receives and handles the two-way low frequency signal simultaneously, signal is reverted to the raw information of electronic tag.Because read write line is realized by electromagnetic coupled and signals reverse scattering with communicating by letter of electronic tag, the finite energy that electronic tag obtains, therefore back-scattering modulation technique can only change the every frame internal data of signal and is " 0 " or " 1 ", can't change the frame length of modulation signal.Technical solutions of the utility model adopt the principle of the direct down coversion of zero intermediate frequency to carry out the signal demodulation, to carrier signal and the noncoherent orthogonal transformation of electronic tag return signal process, to demodulate simultaneously 0 ° and 90 ° of two-way baseband signals are sent into simultaneously in the single-chip microcomputer of control module and are handled, when not increasing device, prevented that effectively electronic tag is around in the motion process of environmental change and electronic tag, the label angle that occurred change and cause change the loss of data that causes because of the phasing degree, problems such as signal weakening, thus make effective decipherment distance of read write line reach tens meters.
Transmitter module comprises radio-frequency (RF) local oscillator circuit, amplitude shift key modulation circuit, power amplification circuit and radio frequency interface in the such scheme; The radio-frequency (RF) local oscillator circuit provides the carrier signal of 920~925MHz for read write line; Amplitude shift key modulation part critical piece is a signal attenuator; Attenuator is decayed to carrier signal, reaches the purpose of amplitude shift key modulation; Power amplification is used for the carrier signal after the decay is carried out power amplification; Radio frequency interface is used to launch carrier signal and receives the reflected signal that electronic tag returns.
Receiver module comprises mixer and two frequency mixer in the such scheme; After mixer mixed carrier signal and radiofrequency signal, orthogonal transformation became 0 ° and 90 ° of signals; After two frequency mixer carry out mixing with 0 ° and 90 ° of signals respectively, produce the baseband signal of 0 ° of two-way and 90 °.What mixer was realized is the non-coherent demodulation of carrier signal and radiofrequency signal.
Baseband processing module mainly is made up of filtering circuit, amplifying circuit, shaping circuit and power supply in the such scheme; Filtering circuit carries out bandpass filtering to the two-way baseband signal; Amplifying circuit amplifies baseband signal; Shaping circuit provides final digital signal by using high speed voltage comparator and Schmidt trigger as control module.
In the such scheme control module comprise embedded-type ARM single-chip microcomputer, UART Universal Asynchronous Receiver Transmitter or and/or the TCP/IP unit; The embedded-type ARM single-chip microcomputer is mainly finished coding, decoding, communication and control task; UART Universal Asynchronous Receiver Transmitter or TCP/IP unit are used to realize ARM single-chip microcomputer and compunication.
The utility model has compared with prior art adopted modular design, its more reasonable structure, and it is more clear that function is divided; Adopt the direct down coversion of zero intermediate frequency to carry out the signal demodulation, realize the two-way quadrature decoder, reduced the bit error rate effectively, promoted the reading/writing distance of read write line; Need not to increase extra digital signal processor spare, only adopt single ARM embedded scm can realize the two-way signal Processing, in guaranteed performance, simplified the structure of read write line, reduced production cost.
(5) embodiment:
Below in conjunction with accompanying drawing the utility model is further elaborated.
Fig. 1 is the schematic diagram of a kind of preferred embodiment of the utility model ultrahigh frequency RFID label reader-writer, comprises control module, transmitter module, receiver module, baseband processing module.The controlled module controls of transmitter module, for read write line provides carrier signal, and with carrier signal modulate with power amplification after, radio frequency interface output by transmitter module transmits to electronic tag, simultaneously, radio frequency interface receives the reflected signal that electronic tag returns, and is input to receiver module.The reflected signal that receiver module returns electronic tag carries out the direct down coversion demodulation of zero intermediate frequency, realizes the two-way quadrature decoder, output two-way baseband signal.Baseband processing module carries out filtering, amplification, shaping to the two-way baseband signal, the accessible low frequency signal of controlled module.Control module receives and handles the two-way low frequency signal simultaneously, signal is reverted to the raw information of electronic tag according to related protocol.
Below the concrete composition embodiment and the function of each module of the present utility model further described.
1, control module
Control module mainly is made of embedded-type ARM single-chip microcomputer, UART Universal Asynchronous Receiver Transmitter and TCP/IP unit.
One end of UART Universal Asynchronous Receiver Transmitter and TCP/IP unit links to each other with the PORT COM of ARM single-chip microcomputer respectively, and the other end links to each other with computing machine, realizes duplex signaling respectively.The mainly responsible read write line in UART Universal Asynchronous Receiver Transmitter and TCP/IP unit is communicated by letter with computing machine.
The embedded-type ARM single-chip microcomputer is the core of read write line, present embodiment is selected the LPC2132ARM7 single-chip microcomputer of Philips for use, be operated in 32 bit patterns, the memory interface of 128 bit wides and unique accelerating structure make 32 codes can be in stable operation under the maximum rate, and it mainly finishes tasks such as amplitude shift keying coding, two phase space decodings, communication, control.
The baseband signal decoding flow process of control module is:
A, single-chip microcomputer catch interrupt and inquiry relatively, simultaneously with the two paths of signals input use of 0 ° and 90 °;
B, single-chip microcomputer are noted the length of the two-way pulse train of input;
C, single-chip microcomputer carry out dynamic digital filtering and time series conversion to two paths of signals, and further the filtering spike disturbs;
D, last, two paths of signals carried out decoding of two phase spaces and verification after, promptly finish decode procedure.
2, transmitter module
Transmitter module mainly is made up of radio-frequency (RF) local oscillator, amplitude shift key modulation circuit, power amplification circuit, circulator/isolator and radio frequency interface.Radio-frequency (RF) local oscillator and amplitude shift key modulation circuit respectively with the chip microcontroller duplex signaling.Power amplification circuit is subjected to the control of single-chip microcomputer, and with the amplitude shift key modulation circuit communication; Power amplification circuit also links to each other with receiver module with circulator/isolator respectively.Circulator/isolator links to each other with receiver module with radio frequency interface.
The phaselocked loop that radio-frequency (RF) local oscillator is made up of frequency synthesizer, loop filter and voltage controlled oscillator provides the carrier signal of 920~925MHz for read write line.The frequency synthesizer that present embodiment is selected for use comprises low noise phase frequency detector, precision charge pump, programmable frequency divider, programmable A counter and B counter and dual-modulus prescaler.Phaselocked loop is a kind of feedback control circuit, and characteristics are for utilizing the frequency of the outside reference signal control loop internal oscillation signal of importing.
The critical piece of amplitude shift key modulation circuit is a signal attenuator.The effect of attenuator is that carrier signal is decayed, and reaches the purpose of amplitude shift key modulation.The attenuator that present embodiment is selected for use can be realized the damping capacity of 1dB~31dB.The modulation system that present embodiment uses is on-off keying, i.e. 100% amplitude shift key modulation.When sending base band data " 0 ", to carrier signal decay 31dB; When sending base band data " 1 ", undamped to carrier signal.Another effect of attenuator is with power amplification circuit the power that transmits to be controlled.
Power amplification circuit mainly is that the radiofrequency signal after the modulation is carried out power amplification, the conditioning signal gain, and the power amplifier that present embodiment is selected for use has the power output of maximum 35dBm, has good control characteristic.The output area of radio-frequency power is 20~31.5dBm in the present embodiment.
Radio frequency interface, promptly antennal interface carries out wireless connections by the cloudy seat of SMA with electronic tag.
3, receiver module
Receiver module mainly is made up of mixer and two frequency mixer.The input end of mixer links to each other with circulator/isolator with the power amplifier module of receiver module.The output terminal of mixer links to each other with two frequency mixer respectively, as Fig. 2.
Mixer becomes 0 ° of signal and 90 ° of signals with the reflected signal orthogonal transformation that receives; After two frequency mixer carry out mixing with 0 ° of signal and 90 ° of signals and local oscillation signal respectively, produce the baseband signal of 0 ° of two-way and 90 °.
The rf receiver unit of present embodiment adopts the principle of the direct down coversion of zero intermediate frequency to carry out the signal demodulation, realizes the two-way quadrature decoder, and the signal of output is exactly a baseband signal.After the two-way radiofrequency signal of process orthogonal transformation is passed through the frequency mixer mixing respectively, will produce the two-way baseband signal.
4, baseband processing module
Baseband processing module mainly is made up of filtering circuit, amplifying circuit, shaping circuit and power supply.Filtering circuit links to each other with receiver module, and the input end of amplifying circuit links to each other with filtering circuit, and output terminal links to each other with shaping circuit, and shaping circuit links to each other with the ARM single-chip microcomputer.
Filtering circuit is the bandpass filter of a 100K~250K, and the two paths of signals with 0 ° and 90 ° carries out bandpass filtering respectively, filtering noise signal, the remaining manageable useful signal of single-chip microcomputer.
Amplifying unit amplifies the faint return signal that filtering circuit transmits, and present embodiment adopts the amplifier of 203M and 160M bandwidth to realize that gain is high, stable performance.
Shaping unit provides final digital signal by using high speed voltage comparator and Schmidt trigger as single-chip microcomputer.
The course of work of the read write line of present embodiment is as follows:
1, after label enters the radio frequency signal district that read write line sends, receives the radiofrequency signal that read write line sends;
2, label relies on induction current on the coil to obtain energy to start label control circuit and radio circuit and send out data according to related protocol;
3, read write line receives the signal of label emission and decodes;
A, receiver module adopt the principle of the direct down coversion of zero intermediate frequency that the signal that receives is carried out demodulation, realize the two-way quadrature decoder, output two-way baseband signal;
B, baseband processing module obtain the manageable useful signal of single-chip microcomputer after the two-way baseband signal is passed through filtering, amplification, shaping;
C, control module revert to the raw information of label with low frequency signal, deliver to background computer then;
4, computing machine carries out the relevant data processing, and last application system obtains needed information, thus the purpose that realization is discerned automatically or write.
The basic parameter of present embodiment read write line is as follows:
Working frequency range: 920~925MHz;
Reading/writing distance: read maximum 12 meters, write maximum 6 meters;
Emissive power:<32dBm;
Recognition capability: have anticollision protocol, possess many tag recognition ability;
Supported protocol: ISO-18000-6B;
Working temperature :-20 O-C~+ 60 O-C;
Power supply: DC9V, 4A;
Power supply power consumption: less than 15W;
Communication interface: RS232 or LAN interface (10M);
Programmable I/O:2 input interface, 2 output interfaces can be realized the control of external signal collection and external unit;
System parameter setting: the online setting of back-up system parameter can keep current systematic parameter simultaneously;
Mode of operation: frequency hopping;
Antennal interface: the cloudy head of SMA type.