The analog simulation method of RFID tag circuit
Technical field
The present invention relates to a kind of emulation mode of semiconductor circuit, especially a kind of analog simulation method of RFID tag circuit.
Background technology
Existing rfid system comprises HF card reader and the label and the antenna composition of emission 13.56MHz signal, the carrier wave that has modulation signal of actual transmission is coupled from the antenna of card reader antenna by physical space and label, label chip produces resonance by antenna of oneself and inner electric capacity, the passive label chip takes out the power supply of energy as entire chip by rectifier, and the signal that card reader is sent is exported in the detuner demodulation of label chip simultaneously.The emission of label chip signal then is by changing the load on the antenna, make that the amplitude of resonance changes on the label antenna, by with the coupling of card reader antenna, amplitude on the card reader antenna is also changed, finish the signal emission of label reading card device chip by signal amplification circuit on the card reader and signal read circuits.When carrying out emulation, how to realize that above-mentioned physical process needs modeling accurately and corresponding circuit design at design RFID tag circuit.The method that adopts when the tag design chip carries out emulation at present is directly in plus signal source, the two ends of label antenna, and as shown in Figure 1, wherein V0~V4 is different control signal source, and S1~S4 is a perfect switch, and R1~R4 is the divider resistance of design.The shortcoming of existing analog simulation method is that the signal source that is loaded is constant, its impedance does not change, as shown in Figure 2, this signal is a perfect sine wave, the waveform that this and antenna ends form continuous variation of practical work process middle impedance is inconsistent, also incomplete same with the actual physical situation of actual chips, the chip of design needs repeatedly flow just can reach consistent with the data under the actual test environment.
Summary of the invention
Technical matters to be solved by this invention provides a kind of analog simulation method of RFID tag circuit, can simulate the real working environment of RFID tag circuit, accurately the RFID tag circuit is carried out emulation.
For solving the problems of the technologies described above, technical scheme of the present invention is, the model of described RFID tag circuit comes complete various simulation operations by antenna receiving signal, the carrier wave and the energy thereof of the band modulation signal of the modeling card reader emission of employing amplitude modulator, and described signal is coupled to the antenna of RFID tag circuit by coefficient of mutual inductance from described amplitude modulator, simulate the size of actual field intensity.
The present invention sends signal by adopting amplitude modulator simulation card reader, and is coupled to the chip of RFID tag circuit by coefficient of mutual inductance, simulates the real working environment of RFID tag circuit, accurately the RFID tag circuit is carried out emulation.
Description of drawings
The present invention is further detailed explanation below in conjunction with drawings and Examples:
Fig. 1 is the synoptic diagram of existing RFID tag circuit analog simulation;
Fig. 2 is the signal waveforms of existing RFID tag circuit analog simulation;
Fig. 3 is the synoptic diagram of RFID tag circuit analog simulation of the present invention;
Fig. 4 is the signal waveforms of RFID tag circuit analog simulation of the present invention.
Embodiment
The invention discloses a kind of analog simulation method of RFID tag circuit, the model of described RFID tag circuit comes complete various simulation operations by antenna receiving signal, the present invention adopts the carrier wave and the energy thereof of band modulation signal of the modeling card reader emission of amplitude modulator, and described signal is coupled to the antenna of RFID tag circuit by coefficient of mutual inductance from described amplitude modulator, simulate the size of actual field intensity.
The RFID label principle of work of ISO14443 agreement defined is to adopt the inductance magnetic coupling of card reader and label antenna to carry out data communication, and as passive label, the label working dc power can obtain from card reader by the magnetic coupling of inductance.Card reader produces the strong-electromagnetic field of high frequency, the xsect of antenna and the space around the coil are passed in this magnetic field, because wavelength ratio card reader antenna in the frequency range of using (13.56MHz) and the big manyfold of distance between the label can be used as simple alternating magnetic field to the electromagnetic field between the antenna and handle.High-frequency current flows through the card reader antenna inductance can produce magnetic field in the space, be coupled in the antenna (inductance) on the label in this magnetic field, produce mutual inductance, be coupled on the label antenna by the current segment of this mutual inductance reader, to just can be used as the direct supply of label behind this voltage commutation, the modulation demodulation that this voltage is contained comes out just can activate specific label or unit.The analog simulation method of RFID tag circuit of the present invention as shown in Figure 3, the emission of signal is to realize by the behavioral scaling model that can adjust amplitude (AM) modulator of carrier frequency, the signal and the carrier signal of modulating signal source are modulated into the AM signal, the logical signal that the modulation of amplitude will be sent by card reader is controlled, the carrier wave of the band specifying information that produces carries out resonance by the antenna of a Voltage-controlled Current Source (VCVS) reading card device again, simulate the physical distance (also being the size of actual field intensity) between physical tags and the card reader and the size of energy by the coefficient of mutual inductance between reading card device antenna and RFID tag circuit antenna, the receiving end of label is near the energy that card reader sends that is coupled the 13.56MHz frequency of the antenna by label then, arrive the internal rectifier circuit of label by the encapsulated delivery of label chip, Fig. 4 is the inductive waveform figure of the present invention on label antenna, its waveform no longer has been simple sine wave, but can change actual conditions when reflecting the work of RFID tag circuit more true to nature with changes in antenna impedance.
Reading card device of the present invention adopts behavioral scaling model to build and touches, the carrier wave of output band modulation signal is converted to the antenna of voltage-controlled voltage source control card reader, simulate the size of actual field intensity by the adjusting of coefficient of mutual inductance, receive the signal that card reader is sent by coupling to the label antenna inductance.Change signal amplitude on the label chip antenna by the logic that changes label chip inside, the antenna of the card reader that is coupled is back again finished the back emitted of label reading card device signal.Concrete enforcement is to adopt the signal that will need to send to adopt the pulse-width signal of HSPICE form to be write as in the regular hour section on the behavioral scaling Verilog model that logical signal is added to following AM (amplitude modulation(PAM)):
By it is set the frequency (now being 13.56MHz) of carrier wave and the maximum/minimum radius and the depth of modulation of signal, obtain containing the card reader output signal of carrier and modulating signal, remove to control the antenna of card reader again by a Voltage-controlled Current Source, the actual signal of simulating actual card reader antenna emission is finished the emission of signal.The field intensity in actual physics space is then represented intensity with the coupling of the antenna of label by the size of coefficient of mutual inductance M, connect the parasitic model (containing lead-in inductance, lead resistance and stray capacitance) of actual chips encapsulation and the RFID label chip of follow-up design again, enter the radio frequency induction circuit part of label.Can simulate actual card reader by this whole complete system, the physical environment of the coupling of two antennas and RFID label and encapsulation is realized the two-way full emulation of communication, carries out the design and the diagnosis of RFID label chip.
In sum, the present invention sends signal by adopting amplitude modulator simulation card reader, and is coupled to the chip of RFID tag circuit by coefficient of mutual inductance, simulates the real working environment of RFID tag circuit, accurately the RFID tag circuit is carried out emulation.