CN204669397U - For subcarrier demodulator and the demodulating equipment of non-contact reader-writer - Google Patents

Abstract

The utility model relates to a kind of subcarrier demodulator for non-contact reader-writer and demodulating equipment.Described subcarrier demodulator comprises: upper side band signal extraction module, for generating the first local oscillated signal, demodulation being carried out to the subcarrier modulated signal received, obtains upper side band signal, wherein, the frequency of described first local oscillated signal is the frequency of positive subcarrier signal; Lower sideband signal extraction module, for generating the second local oscillated signal, carry out demodulation to the subcarrier modulated signal received, obtain lower sideband signal, wherein, the frequency of described second local oscillated signal is the frequency of negative subcarrier signal; Merge module, for the energy according to described upper side band signal and described lower sideband signal, merging treatment is carried out to described upper side band signal and described lower sideband signal, obtains base band modulated signal.The utility model can avoid antenna off resonance on the impact of receiving sensitivity, improves receiving sensitivity.

Description

For subcarrier demodulator and the demodulating equipment of non-contact reader-writer

Technical field

The utility model relates to non-contact reader-writer field, particularly relates to a kind of subcarrier demodulator for non-contact reader-writer and demodulating equipment.

Background technology

As everyone knows, based in the contact type intelligent card system of ISO/IEC14443 standard, when smart card transmits data to read write line, the mode of load-modulate is adopted.Particularly, read write line is masters, produce radiofrequency field, smart card is passive side, does not produce radiofrequency field, when smart card transmits data to card reader, smart card, by changing the load of antenna ends, changes magnetic field intensity, the change of read write line perception magnetic field intensity, thus obtain the data message of smart card transmission, therefore this modulator approach is called load-modulate.Owing to have employed the frequency of 13.56MHz as carrier frequency, read while write device and smart card is two-way communication, for non-contact card, the modulation ratio of smart card to magnetic field is more weak, if load signal directly modulation on carrier wave, so read write line is not easy the data message demodulating smart card transmission, so adopt sub-carrier modulation technology again.In 13.56MHz contact type intelligent card system, the frequency of subcarrier is Fc/16, and wherein, Fc is 13.56MHz, and subcarrier frequency is approximately 848kHz.Smart card first carries out OOK or BPSK modulation by data to subcarrier, and then carries out load-modulate to 13.56MHz carrier wave.Card reader, when receiving the data that smart card transmits, generally needs first to carry out envelope detection, obtains brewed subcarrier signal, then carry out OOK or BPSK demodulation to this brewed subcarrier signal, obtains the data message that smart card transmits.

In traditional envelope detection, normal employing diode detection method, namely utilize the unilateral conduction of diode to carry out halfwave rectifier, then low-pass filtering obtains envelope signal.But when the distance of smart card and read write line changes, the coupling coefficient of both antennas also can change, and then affects the resonance frequency of antenna loop, causes antenna off resonance, makes the energy of upper side band signal and lower sideband signal no longer balanced.Because reading and writing device antenna Q value is higher, bandwidth is less, and after antenna off resonance, have a strong impact on the receiving sensitivity of read write line, performance loss is up to 6dB.

In order to avoid antenna off resonance is on the impact of receiving sensitivity, propose another read write line demodulator.As shown in Figure 1, for the structural representation of demodulator in intelligent card read/write device in prior art, first, demodulation adopts zero intermediate frequency quadrature downconvert scheme, the radiofrequency signal that antenna receives and the simulation orthogonal local oscillation signal that generates of analog local oscillator 10 carry out quadrature downconvert simulating in orthogonal mixer 11, export I road signal and Q road signal, then bandpass filtering is carried out through band pass filter BPF 12, signal after bandpass filtering sends into programmable gain amplifier (Programmable Gain Amplifier, be called for short: PGA) 13 amplify after, send into analog to digital converter ADC 14 and carry out analog-to-digital conversion, obtain digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal, then in merging module 15, digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal are merged, obtain digital baseband modulated signal, in base band demodulating module 16, base band demodulating is carried out to digital baseband modulated signal, obtain the data message that smart card transmits.Wherein, merge module 15 can merge in the following way:

1, sqrt (sigI^2+sigQ^2) is adopted to merge.Owing to introducing direct current OFFSET after mixing on I/Q link, add band pass filter and remove this DC component, cause the component occurring in i/q signal bearing, therefore can not adopt and carry out signal merging in this way.

2, select branch road that in I/Q two paths of signals, amplitude is larger as output.But, when in process of exchange, because hand-held intelligent card there occurs movement to the distance between card reader, the change of antenna-coupled coefficient can be caused, carrier phase on antenna is caused to change relative to local 13.56MHz clock phase, after mixing, the relative size of i/q signal amplitude can change, and that road signal amplitude chosen may be caused to become less, and performance can worsen further.

3, using I+Q or I-Q as output.When antenna matching network off resonance, cause i/q signal to be no longer homophase or reverse relation, can not directly carry out being added or subtracting each other merging.

Therefore, the demodulator shown in Fig. 1 can not avoid antenna off resonance on the impact of receiving sensitivity.

Utility model content

The utility model provides a kind of subcarrier demodulator for non-contact reader-writer and demodulating equipment, in order to realize avoiding antenna off resonance on the impact of receiving sensitivity, improves receiving sensitivity.

The utility model provides a kind of subcarrier demodulator for non-contact reader-writer, comprising:

Upper side band signal extraction module, for generating the first local oscillated signal, carry out demodulation to the subcarrier modulated signal received, obtain upper side band signal, wherein, the frequency of described first local oscillated signal is the frequency of positive subcarrier signal;

Lower sideband signal extraction module, for generating the second local oscillated signal, carry out demodulation to the subcarrier modulated signal received, obtain lower sideband signal, wherein, the frequency of described second local oscillated signal is the frequency of negative subcarrier signal;

Merge module, for the energy according to described upper side band signal and described lower sideband signal, merging treatment is carried out to described upper side band signal and described lower sideband signal, obtains base band modulated signal.

The utility model also provides a kind of demodulating equipment for non-contact reader-writer, comprising:

Main carrier demodulator, for receiving main carrier modulated signal, carrying out demodulation to described main carrier modulated signal, obtaining subcarrier modulated signal;

Subcarrier demodulator, for generating the first local oscillated signal, demodulation is carried out to the subcarrier modulated signal received, obtain upper side band signal, generate the second local oscillated signal, demodulation is carried out to the subcarrier modulated signal received, obtain lower sideband signal, merging treatment is carried out to described upper side band signal and described lower sideband signal, obtain base band modulated signal, wherein, the frequency of described first local oscillated signal is the frequency of positive subcarrier signal, and the frequency of described second local oscillated signal is the frequency of negative subcarrier signal;

Base band demodulator, for carrying out demodulation to described base band modulated signal, obtains the data message that contact type intelligent card transmits.

In the utility model embodiment, by two demodulation branch roads, subcarrier demodulation is carried out to subcarrier modulated signal, wherein, upper side band signal extraction module extracts upper side band signal from subcarrier modulated signal, lower sideband signal extraction module extracts lower sideband signal from subcarrier modulated signal, then the energy of module according to upper side band signal and lower sideband signal is merged, merging treatment is carried out to upper side band signal and lower sideband signal, obtain base band modulated signal, like this, owing to being extracted upper side band signal and lower sideband signal, according to the energy of upper side band signal and lower sideband signal, upper side band signal and lower sideband signal are merged, obtain base band modulated signal, even if so antenna off resonance causes the energy of upper side band signal and lower sideband signal unbalanced, also base band modulated signal accurately can be obtained, avoid the impact of antenna off resonance on receiving sensitivity, improve receiving sensitivity.

Accompanying drawing explanation

Fig. 1 is the structural representation of demodulator in intelligent card read/write device in prior art;

Fig. 2 is the reception schematic diagram of the utility model for the demodulating equipment embodiment of non-contact reader-writer;

Fig. 3 is the structural representation of the utility model for the subcarrier demodulator embodiment of non-contact reader-writer;

Fig. 4 is the schematic flow sheet of the utility model for the subcarrier demodulation method embodiment of non-contact reader-writer;

Fig. 5 is the structural representation of the utility model for digital phase-locked loop in the subcarrier demodulator embodiment of non-contact reader-writer.

Embodiment

Below in conjunction with specification drawings and specific embodiments, the utility model will be further described.

As shown in Figure 2, the reception schematic diagram of the demodulating equipment embodiment of non-contact reader-writer is used for for the utility model, this demodulating equipment can comprise main carrier demodulator 21, subcarrier demodulator 22 and base band demodulator 23, wherein, subcarrier demodulator 22 is connected with main carrier demodulator 21, and base band demodulator 23 is connected with subcarrier demodulator 22.

Main carrier demodulator 21, for receiving main carrier modulated signal, carries out demodulation to main carrier modulated signal, obtains subcarrier modulated signal; Subcarrier demodulator 22 is for generating the first local oscillated signal, demodulation is carried out to the subcarrier modulated signal received, obtain upper side band signal, generate the second local oscillated signal, demodulation is carried out to the subcarrier modulated signal received, obtain lower sideband signal, merging treatment is carried out to upper side band signal and lower sideband signal, obtain base band modulated signal, wherein, the frequency of the first local oscillated signal is the frequency of positive subcarrier signal, and the frequency of the second local oscillated signal is the frequency of negative subcarrier signal; Base band demodulator 23, for carrying out demodulation to base band modulated signal, obtains the data message that contact type intelligent card transmits.Alternatively, base band demodulator 23 can carry out OOK or BPSK demodulation to base band modulated signal.

Wherein, the concrete structure of subcarrier demodulator 22 is as follows: as shown in Figure 3, the structural representation of the subcarrier demodulator embodiment of non-contact reader-writer is used for for the utility model, subcarrier demodulator 22 can comprise upper side band signal extraction module 221, lower sideband signal extraction module 222 and merge module 15, upper side band signal extraction module 221 is connected with main carrier demodulator 21 with lower sideband signal extraction module 222, merges module 15 and is connected with upper side band signal extraction module 221 and lower sideband signal extraction module 222.

Upper side band signal extraction module 221 is for generating the first local oscillated signal, and carry out demodulation to the subcarrier modulated signal received, obtain upper side band signal, wherein, the frequency of the first local oscillated signal is the frequency of positive subcarrier signal; Lower sideband signal extraction module 222 is for generating the second local oscillated signal, and carry out demodulation to the subcarrier modulated signal received, obtain lower sideband signal, wherein, the frequency of the second local oscillated signal is the frequency of negative subcarrier signal; Merge module 15 for the energy according to upper side band signal and lower sideband signal, merging treatment is carried out to upper side band signal and lower sideband signal, obtains base band modulated signal.

The course of work of subcarrier demodulator 22 is as follows: as shown in Figure 4, and be used for the schematic flow sheet of the subcarrier demodulation method embodiment of non-contact reader-writer for the utility model, the method can comprise the steps:

Step 41, upper side band signal extraction module 221 generate the first local oscillated signal, and carry out demodulation to the subcarrier modulated signal received, obtain upper side band signal, wherein, the frequency of the first local oscillated signal is the frequency of positive subcarrier signal;

Step 42, lower sideband signal extraction module 222 generate the second local oscillated signal, and carry out demodulation to the subcarrier modulated signal received, obtain lower sideband signal, wherein, the frequency of the second local oscillated signal is the frequency of negative subcarrier signal;

Step 43, merge the energy of module 15 according to upper side band signal and lower sideband signal, merging treatment is carried out to upper side band signal and lower sideband signal, obtains base band modulated signal.

In the present embodiment, by two demodulation branch roads, subcarrier demodulation is carried out to subcarrier modulated signal, wherein, upper side band signal extraction module 221 extracts upper side band signal from subcarrier modulated signal, lower sideband signal extraction module 222 extracts lower sideband signal from subcarrier modulated signal, then the energy of module 15 according to upper side band signal and lower sideband signal is merged, merging treatment is carried out to upper side band signal and lower sideband signal, obtain base band modulated signal, like this, owing to being extracted upper side band signal and lower sideband signal, according to the energy of upper side band signal and lower sideband signal, upper side band signal and lower sideband signal are merged, obtain base band modulated signal, even if so antenna off resonance causes the energy of upper side band signal and lower sideband signal unbalanced, also base band modulated signal accurately can be obtained, avoid the impact of antenna off resonance on receiving sensitivity, improve receiving sensitivity.

Alternatively, main carrier demodulator 21 can comprise the analog local oscillator 10 shown in Fig. 1, simulation orthogonal mixer 11, band pass filter BPF 12 and analog to digital converter 14, does not repeat them here.Alternatively, main carrier demodulator 21 can also comprise PGA 13, is connected between band pass filter 12 and analog to digital converter 14.

Alternatively, structural representation shown in Figure 3, upper side band signal extraction module 221 can comprise the first digital local oscillator 2211, first digital quadrature mixer 2212 and the first wave digital lowpass filter (Digital Low Pass Filter, be called for short: DLPF) 2213, lower sideband signal extraction module 222 can comprise the second digital local oscillator 2221, second digital quadrature mixer 2222, 2nd DLPF 2223, first digital quadrature mixer 2212 is connected with the first digital local oscillator 2211 and main carrier demodulator 21, one DLPF 2213 is connected with the first digital quadrature mixer 2212, second digital quadrature mixer 2222 is connected with the second digital local oscillator 2221 and main carrier demodulator 21, 2nd DLPF 2223 is connected with the second digital quadrature mixer 2222.The subcarrier modulated signal that main carrier demodulator 21 exports can comprise digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal, the first local oscillated signal that first digital local oscillator 2211 generates is specifically as follows the first digital quadrature local oscillated signal, the second local oscillated signal that second digital local oscillator 2221 generates is specifically as follows the second digital quadrature local oscillated signal, the upper side band signal that one DLPF 2213 exports can comprise an I railway digital base band modulated signal and a Q railway digital base band modulated signal, the lower sideband signal that 2nd DLPF 2223 exports can comprise the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal.

Wherein, the first digital local oscillator 2211 is for generating the first digital quadrature local oscillated signal; First digital quadrature mixer 2212 is for carrying out quadrature downconvert by the first digital quadrature local oscillated signal and digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal; One DLPF 2213 carries out low-pass filtering for the signal exported the first digital quadrature mixer, obtain an I railway digital base band modulated signal and a Q railway digital base band modulated signal, alternatively, two sub-DLPF can be comprised in one DLPF, respectively filtering is carried out to the two paths of signals that the first digital quadrature mixer 2212 exports; Second digital local oscillator 2221 is for generating the second digital quadrature local oscillated signal; Second digital quadrature mixer 2222 is for carrying out quadrature downconvert by the second digital quadrature local oscillated signal and digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal; 2nd DLPF 2223 carries out low-pass filtering for the signal exported the second digital quadrature mixer 2222, obtain the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal, alternatively, two sub-DLPF can be comprised in 2nd DLPF 2223, respectively filtering is carried out to the two paths of signals that the second digital quadrature mixer 2222 exports; Merging module 15 for carrying out merging treatment to an I railway digital base band modulated signal, a Q railway digital base band modulated signal, the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal, obtaining base band modulated signal.Such as: for the digital sub carrier modulated signal adopting OOK mode modulation, just can adopt upper side band signal extraction module 221 and the lower sideband signal extraction module 222 of this structure.

Correspondingly, in schematic flow sheet shown in Fig. 4, step 41 can comprise the steps:

Step 411, the first digital local oscillator 2211 generate the first digital quadrature local oscillated signal;

First digital quadrature local oscillated signal and digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal are carried out quadrature downconvert by step 412, the first digital quadrature mixer 2212;

Step 413, a DLPF 2213 carry out low-pass filtering to the signal that the first digital quadrature mixer 2212 exports, and obtain an I railway digital base band modulated signal and a Q railway digital base band modulated signal;

Step 42 can comprise the steps:

Step 421, the second digital local oscillator 2221 generate the second digital quadrature local oscillated signal;

Second digital quadrature local oscillated signal and digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal are carried out quadrature downconvert by step 422, the second digital quadrature mixer 2222;

Step 423, the 2nd DLPF 2223 carry out low-pass filtering to the signal that the second digital quadrature mixer 2222 exports, and obtain the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal;

Step 43 is specifically as follows: merge module 15 and carry out merging treatment to an I railway digital base band modulated signal, a Q railway digital base band modulated signal, the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal, obtain base band modulated signal.

Alternatively, merge module 15 can using upper side band signal and lower sideband signal and as base band modulated signal or using sideband signals larger for energy in upper side band signal and lower sideband signal as base band modulated signal.

Owing to having carried out mixing by the first digital quadrature mixer 2212 and the second digital quadrature mixer 2222, with DC component in making mixing export, so there is no negative component in an I railway digital base band modulated signal, a Q railway digital base band modulated signal, the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal, merge selection that module 15 carries out merging so just a lot.Alternatively, merge module 15 can adopt the following two kinds mode using upper side band signal and lower sideband signal and as base band modulated signal:

Mode one: merge module 15 and in the following way merging treatment is carried out to upper side band signal and lower sideband signal:

$de\mathrm{mod}out=\sqrt{mfI{1}^2+mfQ{1}^2}+\sqrt{mfI{2}^2+mfQ{2}^2}---\left(1\right)$

Wherein, demodout is base band modulated signal, and mfI1 is an I railway digital base band modulated signal, and mfQ1 is a Q railway digital base band modulated signal, and mfI2 is the 2nd I railway digital base band modulated signal, and mfQ2 is the 2nd Q digital baseband modulated signal;

Mode two: merging module 15 can also carry out merging treatment to upper side band signal and lower sideband signal in the following way:

demodout＝|mfI1|+|mfQ1|+|mfI2|+|mfQ2| (2)

Alternatively, when the energy of upper side band signal is greater than the energy of lower sideband signal, merges module 15 and can adopt the following two kinds mode using sideband signals larger for energy in upper side band signal and lower sideband signal as base band modulated signal:

Mode one: merging module 15 can carry out merging treatment to upper side band signal and lower sideband signal in the following way:

$de\mathrm{mod}out=\sqrt{mfI{1}^2+mfQ{1}^2}---\left(3\right)$

Mode two: merging module 15 can also carry out merging treatment to upper side band signal and lower sideband signal in the following way:

demodout＝|mfI1|+|mfQ1| (4)

Alternatively, structural representation shown in Figure 3 again, upper sideband extraction module 221 can also comprise the first digital phase-locked loop 2214, be connected to a DLPF 2213 and merge between module 15, lower sideband signal extraction module 222 can also comprise the second digital phase-locked loop 2224, is connected to the 2nd DLPF 2223 and merges between module 15.First digital phase-locked loop 2214 is for entering horizontal phasing control to an I railway digital base band modulated signal and a Q railway digital base band modulated signal, export an an x direction signal mfx1 and y direction signal mfy1, wherein, the concentration of energy of upper side band signal is on an x direction signal mfx1; Second digital phase-locked loop 2224, for carrying out Phase Tracking to the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal, exports the 2nd x direction signal mfx2 and the 2nd y direction signal mfy2; Wherein, the concentration of energy of lower sideband signal is on the 2nd x direction signal mfx2.Merging module 15 for carrying out merging treatment to an x direction signal mfx1, a y direction signal mfy1, the 2nd x direction signal mfx2 and the 2nd y direction signal mfy2, obtaining base band modulated signal.Now, due to sideband signals concentration of energy in the x direction, so the signal in x direction is far longer than y direction signal, aforesaid calculating formula (1) and (2) can be reduced to:

demodout＝|mfx1|+|mfx2| (5)

Aforesaid calculating formula (3) and (4) can be reduced to:

demodout＝|mfx1| (6)

Alternatively, the energy of upper side band signal can also concentrate on a y direction signal, and the energy of lower sideband signal can also concentrate on the 2nd y direction signal, and now, aforesaid calculating formula (1) and (2) can be reduced to:

demodout＝|mfy1|+|mfy2| (7)

Aforesaid calculating formula (3) and (4) can be reduced to:

demodout＝|mfy1| (8)

For the digital sub carrier modulated signal adopting BPSK pattern, the upper side band signal extraction module 221 with digital phase-locked loop shown in Fig. 3 and lower sideband signal extraction module 222 can be adopted, and the first digital phase-locked loop 2214 and the second digital phase-locked loop 2224 only enter horizontal phasing control to the frame head of every frame data, horizontal phasing control is not entered to other data outside removing frame head.

Alternatively, as shown in Figure 5, for the utility model is used for the structural representation of digital phase-locked loop in the subcarrier demodulator embodiment of non-contact reader-writer, first digital phase-locked loop 2214 and the second digital phase-locked loop all can adopt this structure to realize, this digital phase-locked loop can comprise phase discriminator 51, loop filter 52, phase place automatic calibration controller 53, rotation of coordinate frequency mixer (Cordic Mixer) 54, the input of loop filter 52 is connected with the output of phase discriminator 51, the input of phase place automatic calibration controller 53 is connected with the output of loop filter 52, the input of rotation of coordinate frequency mixer 54 is connected with the output of a DLPF 2213 or the 2nd DLPF 2223 and is connected with the output of phase place automatic calibration controller 22143, the output of rotation of coordinate frequency mixer 55 is the output of digital phase-locked loop 2214 and is connected with the input of phase discriminator 51.Alternatively, phase discriminator 51 can adopt the form of atan (y/x) to realize, and like this, the concentration of energy of the signal finally making digital phase-locked loop export in the x direction.

Alternatively, in order to filtering interference signals, in structural representation shown in Fig. 3, upper side band signal extraction module 221 is on the basis comprising the first digital phase-locked loop 2214, the 3rd DLPF 2215 can also be comprised, lower sideband signal extraction module 222, on the basis comprising the second digital phase-locked loop 2224, can also comprise the 4th DLPF 2225.

Wherein, the 3rd DLPF 2215 is for carrying out digital low-pass filtering to an x direction signal and a y direction signal, and the 4th DLPF 2225 is for carrying out digital low-pass filtering to the 2nd x direction signal and the 2nd y direction signal.Alternatively, two sub-DLPF can be comprised in 3rd DLPF 2215, respectively filtering is carried out to an x direction signal and a y direction signal, two sub-DLPF in the 2nd DLFP 2225, can be comprised, respectively filtering is carried out to the 2nd x direction signal and the 2nd y direction signal.

Last it is noted that above embodiment is only in order to illustrate the technical solution of the utility model and unrestricted, although be described in detail the utility model with reference to preferred embodiment, those of ordinary skill in the art is to be understood that, can modify to the technical solution of the utility model or equivalent replacement, and not depart from the spirit and scope of technical solutions of the utility model.

Claims (6)

1. for a subcarrier demodulator for non-contact reader-writer, it is characterized in that, comprising:

Upper side band signal extraction module, for generating the first local oscillated signal, carry out demodulation to the subcarrier modulated signal received, obtain upper side band signal, wherein, the frequency of described first local oscillated signal is the frequency of positive subcarrier signal;

Lower sideband signal extraction module, for generating the second local oscillated signal, carry out demodulation to the subcarrier modulated signal received, obtain lower sideband signal, wherein, the frequency of described second local oscillated signal is the frequency of negative subcarrier signal;

Merge module, for the energy according to described upper side band signal and described lower sideband signal, merging treatment is carried out to described upper side band signal and described lower sideband signal, obtains base band modulated signal.

2. the subcarrier demodulator for non-contact reader-writer according to claim 1, it is characterized in that, described subcarrier modulated signal comprises digital sub carrier modulated I road signal and digital sub carrier modulated Q road signal, described first local oscillated signal is specially the first digital quadrature local oscillated signal, described second local oscillated signal is specially the second digital quadrature local oscillated signal, described upper side band signal comprises an I railway digital base band modulated signal and a Q railway digital base band modulated signal, described lower sideband signal comprises the 2nd I railway digital base band modulated signal and the 2nd Q railway digital base band modulated signal,

Described upper side band signal extraction module comprises:

First digital local oscillator, for generating described first digital quadrature local oscillated signal;

First digital quadrature mixer, for carrying out quadrature downconvert by described first digital quadrature local oscillated signal and described first digital sub carrier modulated I road signal and described first digital sub carrier modulated Q road signal;

First wave digital lowpass filter, carries out low-pass filtering for the signal exported described first digital quadrature mixer, obtains a described I railway digital base band modulated signal and a described Q railway digital base band modulated signal;

Described lower sideband signal extraction module comprises:

Second digital local oscillator, for generating described second digital quadrature local oscillated signal;

Second digital quadrature mixer, for carrying out quadrature downconvert by described second digital quadrature local oscillated signal and described second digital sub carrier modulated I road signal and described second digital sub carrier modulated Q road signal;

Second wave digital lowpass filter, carries out low-pass filtering for the signal exported described second digital quadrature mixer, obtains described 2nd I railway digital base band modulated signal and described 2nd Q railway digital base band modulated signal;

Described merging module is used for carrying out merging treatment to a described I railway digital base band modulated signal, a described Q railway digital base band modulated signal, described 2nd I railway digital base band modulated signal and described 2nd Q railway digital base band modulated signal, obtains described base band modulated signal.

3. the subcarrier demodulator for non-contact reader-writer according to claim 2, is characterized in that, described upper sideband extraction module also comprises:

First digital phase-locked loop, for entering horizontal phasing control to a described I railway digital base band modulated signal and a described Q railway digital base band modulated signal, export an x direction signal and a y direction signal, the concentration of energy of described upper side band signal is on a described x direction signal or on a y direction;

Described lower sideband extraction module also comprises:

Second digital phase-locked loop, for entering horizontal phasing control to described 2nd I railway digital base band modulated signal and described 2nd Q railway digital base band modulated signal, exports the 2nd x direction signal and the 2nd y direction signal;

Described merging module is used for carrying out merging treatment to a described x direction signal, a described y direction signal, described 2nd x direction signal and described 2nd y direction signal, obtain described base band modulated signal, the concentration of energy of described lower sideband signal is on described 2nd x direction signal or on described 2nd y direction signal.

4. the subcarrier demodulator for non-contact reader-writer according to Claims 2 or 3, is characterized in that, described merging module carries out merging treatment to described upper side band signal and described lower sideband signal in the following way:

$\mathrm{de}\mathrm{mod}\mathrm{out}=\sqrt{\mathrm{mfy}{1}^2+\mathrm{mfx}{1}^2}+\sqrt{\mathrm{mfy}{2}^2+\mathrm{mfx}{2}^2}$

Wherein, demodout is the signal after merging treatment, mfx1 is a described x direction signal or a described Q railway digital base band modulated signal, mfy1 is a described y direction signal or a described I railway digital base band modulated signal, mfx2 is described 2nd x direction signal or described 2nd Q railway digital base band modulated signal, and mfy2 is described 2nd y direction signal or described 2nd I railway digital base band modulated signal.

5. for a demodulating equipment for non-contact reader-writer, it is characterized in that, comprising:

Main carrier demodulator, for receiving main carrier modulated signal, carrying out demodulation to described main carrier modulated signal, obtaining subcarrier modulated signal;

Subcarrier demodulator, for generating the first local oscillated signal, demodulation is carried out to the subcarrier modulated signal received, obtain upper side band signal, generate the second local oscillated signal, demodulation is carried out to the subcarrier modulated signal received, obtain lower sideband signal, merging treatment is carried out to described upper side band signal and described lower sideband signal, obtain base band modulated signal, wherein, the frequency of described first local oscillated signal is the frequency of positive subcarrier signal, and the frequency of described second local oscillated signal is the frequency of negative subcarrier signal;

Base band demodulator, for carrying out demodulation to described base band modulated signal, obtains the data message that contact type intelligent card transmits.

6. device according to claim 5, is characterized in that, described subcarrier demodulator comprises the arbitrary described subcarrier demodulator for non-contact reader-writer of claim 1-4.