JP6699492B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a wireless communication device, and more particularly to a wireless communication device that wirelessly communicates with a non-contact IC card, a non-contact IC chip, or the like.

  A wireless communication device such as a reader/writer device that wirelessly communicates with a non-contact IC card or a non-contact IC chip performs wireless communication using a resonance circuit including an antenna coil and a capacitor.

  In such a wireless communication device that performs communication using a resonance circuit composed of an antenna coil and a capacitor, the optimum adjustment (for example, the resonance frequency of the antenna is adjusted to 13.56 MHz) for the antenna at the time of shipment. Be implemented. At this time, there is no contactless IC card or another antenna in the vicinity of the antenna, and the environment/state (hereinafter referred to as a no-load state) in which the characteristics of the antenna to be adjusted is not changed is set as a condition.

  However, after the installation of the wireless communication device, the inductance of the antenna coil may change with temperature or with time. When the inductance of the antenna coil changes, the resonance frequency of the resonance circuit changes, and the communication performance of the wireless communication device deteriorates.

  As a wireless communication device that copes with such a problem, there is provided a wireless communication device that performs communication using a resonance circuit including an antenna coil and a capacitor, the antenna coil and a capacitor forming the resonance circuit with the antenna coil. An inductance detection unit that detects the inductance of the antenna coil; and a resonance frequency correction unit that corrects the resonance frequency of the resonance circuit by changing the capacitance of the capacitor based on the detection result of the inductance detection unit. There is a wireless communication device provided with (Patent Document 1).

JP2012-114822A

  However, the wireless communication device described in Patent Document 1 has the following problems because it adjusts only the resonance frequency and not the impedance. That is, when a load object such as a non-contact IC card or a non-contact IC chip approaches the wireless communication device, the antenna coils of the wireless communication devices are electromagnetically coupled to each other, so that the input side of the antenna of the wireless communication device (radio frequency amplification). The impedance seen from the output side of the section becomes a mismatched state that deviates from the matched state by the optimum adjustment in the no-load state.

  In the mismatched state, the current consumption of the wireless communication device changes, which may lead to an increase in temperature due to an increase in the current consumption. In addition, the resonance frequency changes and the communication performance deteriorates. Not only the communication partner device such as a non-contact IC card, but also a metal object existing in the vicinity of the wireless communication device becomes a load that causes an inconsistent state during use.

  The present invention has been made to solve such a problem, and an object thereof is a wireless communication device that performs wireless communication using a resonance circuit configured of an antenna coil and a capacitor, and a load when the device is used. It is to correct the inconsistent state caused by.

  The present invention relates to an antenna section including a resonance circuit including an antenna coil and a capacitor, a modulation section for modulating a carrier wave, a radio frequency amplification section for amplifying an output of the modulation section, the radio frequency amplification section, and the A matching circuit unit for matching with the antenna unit, and a no-load information storage that stores information indicating a no-load phase and a no-load intensity that are the phase and intensity of the output of the radio frequency amplification unit in the no-load state Means, a in-use information detecting means for detecting an in-use phase and an in-use intensity which are phases and intensities of the radio frequency amplification section in use, and the in-use phase and the in-use intensity are respectively when the no load is present. A wireless communication device comprising: a resonance frequency of the resonance circuit and an adjusting unit for adjusting the impedance of the matching circuit unit so as to be equal to the phase and the strength under no load.

  According to the present invention, in a wireless communication device that performs wireless communication using a resonance circuit including an antenna coil and a capacitor, it is possible to correct a mismatched state caused by a load when the device is used.

It is a block diagram which shows the schematic structure of the radio|wireless communication apparatus which concerns on embodiment of this invention. 2 is a block diagram of main parts of a control unit and a transmission/reception unit in FIG. 1. FIG. FIG. 3 is a diagram showing an example of a circuit configuration of a matching circuit unit in FIG. 2 and an equivalent circuit of an antenna unit. 9 is a flowchart showing an example of a procedure for correcting a mismatched state when using a product in the wireless communication device according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<Schematic configuration of wireless communication device>
FIG. 1 is a block diagram showing a schematic configuration of a wireless communication device according to an embodiment of the present invention. This wireless communication device is a reader/writer device that wirelessly communicates with a non-contact IC card or a non-contact IC chip.

  As illustrated, the reader/writer device 1 includes a control unit 2, a transmission/reception unit 3, and an antenna unit 4.

  The control unit 2 includes a CPU and a storage device. The CPU controls the overall operation of the reader/writer device 1 in addition to executing the processing by executing the program stored in the storage device. The storage device is composed of a known storage device such as a ROM, a RAM, or a flash memory, either alone or in combination.

  When communicating with a non-contact IC card or the like, the transmitting/receiving unit 3 modulates a carrier wave of a predetermined frequency (eg, 13.56 MHz) with the baseband data generated by the control unit 2, amplifies it, and sends it to the antenna unit 4. To do. Further, the transmission/reception unit 3 demodulates the data in the radio frequency signal received by the antenna unit 4 from the non-contact IC card or the like, and sends it to the control unit 2. The antenna unit 4 constitutes a resonance circuit including an antenna coil and a capacitor, and the inductance of the antenna coil and the capacitance of the capacitor are set so that the resonance frequency matches the frequency of the carrier wave.

  When the reader/writer device 1 detects a mismatched state of the device, the reader/writer device 1 has a function of correcting the mismatched state by adjusting the resonance frequency of the resonance circuit and/or the impedance of the matching circuit section. Details of this function will be described later.

<Main parts of control unit and transmission/reception unit>
FIG. 2 is a block diagram of essential parts of the control unit 2 and the transmission/reception unit 3 in FIG. This block diagram is a portion that operates when executing the above-described function of correcting the mismatched state.

  As illustrated, the control unit 2 includes first to third bandpass filters 21 to 23 and a determination/processing unit 24. The transmitter/receiver 3 also includes a modulator 31, a radio frequency amplifier 32, a low-pass filter 33, a matching circuit 34, and first to third oscillators 35 to 37.

  The first oscillating unit 35 generates a sine wave having a predetermined frequency (eg, 13.56 MHz) as a carrier wave. The second oscillating unit 36 and the third oscillating unit 37 generate a sine wave having a frequency twice the carrier wave and a frequency three times the carrier wave, respectively.

  The modulator 31 modulates the carrier wave output from the first oscillator 35 with data to generate a modulated wave, and sends the modulated wave to the radio frequency amplifier 32. The radio frequency amplifier 32 amplifies the modulated wave and sends it to the low pass filter 33. The low-pass filter 33 removes harmonic components and the like from the output of the radio frequency amplification unit 32. The output of the low-pass filter 33 passes through the matching circuit unit 34 and is transmitted from the antenna unit 4.

  The matching circuit unit 34 is a circuit for impedance matching with the antenna unit 4. The antenna unit 4 constitutes a resonance circuit including an antenna coil and a capacitor, and performs wireless communication using electromagnetic induction with an antenna coil such as a non-contact IC card or a non-contact IC chip.

  FIG. 3 shows an example of the circuit configuration of the matching circuit section 34 and an equivalent circuit of the antenna section 4. Here, the matching circuit unit 34 is composed of a variable capacitor connected in series between the low-pass filter 33 and the antenna unit 4. In addition, the antenna unit 4 includes an antenna coil, a variable capacitor, and a parallel circuit of resistance components. The capacitance of these variable capacitors can be changed by a control voltage from the judgment/processing unit 24 in the control unit 2, and the impedance of the matching circuit unit 34 and the resonance frequency of the antenna unit 4 are adjusted by adjusting the capacitance. can do.

  The first band-pass filter 21, the second band-pass filter 22, and the third band-pass filter 23 respectively output the frequency of the carrier wave (hereinafter referred to as the fundamental wave) and twice the carrier wave from the output of the radio frequency amplifier 32. The frequency (hereinafter referred to as the second harmonic) and the frequency three times the frequency of the carrier (hereinafter referred to as the third harmonic) are extracted. Since an amplifier circuit using a semiconductor element has a non-linear characteristic, a harmonic component such as a second harmonic wave or a third harmonic wave is generated.

  The determination/processing unit 24 determines the phases and intensities of the outputs of the first bandpass filter 21, the second bandpass filter 22, and the third bandpass filter 23 in an unloaded state such as at the time of product shipment, and product usage. The phase and intensity of the outputs of the first band-pass filter 21, the second band-pass filter 22, and the third band-pass filter 23 at the time are compared, and the mismatched state deviates from the matched state adjusted in the no-load state. Is detected and the matching circuit unit 34 and the antenna unit 4 are adjusted to match the phase and strength in the unloaded state, thereby correcting the mismatched state.

<Correction of inconsistent state>
FIG. 4 is a flowchart showing an example of a procedure for correcting an inconsistent state when using a product in the wireless communication device according to the embodiment of the present invention. Hereinafter, an example of a procedure in which the reader/writer device 1 corrects a mismatched state during use will be described with reference to FIGS. 2 to 4.

  First, the CPU of the control unit 2 reads the initial state information from the storage device (step S1). The initial state information includes the first phase information (hereinafter, also referred to as “phase i”) and the second phase information (hereinafter, referred to as “phase i”) written in the storage device in the control unit 2 in a no-load state at the time of shipment. , May be referred to as "phase ii"), first intensity information (hereinafter may be referred to as "signal intensity i"), second intensity information (hereinafter referred to as "signal intensity ii") Sometimes).

  Here, the phase i and the signal intensity i are the phase information of the carrier wave which is obtained by amplifying the unmodulated carrier wave (carrier) sent from the modulating section 31 by the radio frequency amplifying section 32 and extracting by the first band pass filter 21, This is strength information. This phase information is acquired by phase-detecting the carrier wave (fundamental wave component) extracted by the first bandpass filter 21 with the output of the first oscillating unit 35 as a reference. Further, the intensity information is acquired by amplitude-detecting the carrier wave extracted by the first bandpass filter 21.

  As for the phase ii and the signal strength ii, the unmodulated carrier wave (carrier) sent from the modulator 31 is amplified by the radio frequency amplifier 32, and the second bandpass filter 22 and the third bandpass filter 23 are used. These are phase information and intensity information of the extracted carrier wave. As the phase information, the second harmonic wave and the third harmonic wave extracted by the second bandpass filter 22 and the third bandpass filter 23 are output from the second oscillator 36 and the third oscillator 37, respectively. It is acquired by phase detection using the output as a reference. The intensity information is acquired by amplitude-detecting the second harmonic wave and the third harmonic wave extracted by the second bandpass filter 22 and the third bandpass filter 23, respectively.

  Next, the CPU in the control unit 2 causes the modulation unit 31 to send out an unmodulated carrier wave (carrier) (step S2: R/W standby). Next, the determination/processing unit 24 phase-detects the output of the first bandpass filter 21 with the output of the first oscillating unit 35 as a reference to obtain the phase information of the fundamental wave, and further compares it with the phase i. Then, it is determined whether the phases match (step S3).

  If the phases do not match (step S3: ≠ phase i), the capacitance of the variable capacitor of the antenna unit 4 is adjusted until the phases match (step S4→step S3). If the phases match (step S3:=phase i), the output of the first bandpass filter 21 is amplitude-detected to acquire the intensity information of the fundamental wave, and further compared with the signal intensity i, It is determined whether the intensities match (step S5).

  If the intensities do not match (step S5: ≠ signal intensity i), the capacitance of the variable capacitor of the matching circuit unit 34 is adjusted until the intensities match (steps S6→S5). If the intensities match (step S5:=signal intensity i), the output of the first bandpass filter 21 is again phase-detected with the output of the first oscillating unit 35 as a reference, so that the fundamental wave The phase information is acquired and further compared with the phase i to determine whether or not the phases match (step S7).

  If the phases do not match (step S7: ≠ phase i), the capacitance of the variable capacitor of the antenna unit 4 is adjusted, and the process returns to step S3. By performing this procedure, it is possible to correct the phase shift when the phases of the fundamental wave components are matched by the phase adjustment and then the phase is shifted by the intensity adjustment.

  If the phases match (step S7:=phase i), the process moves to the adjustment of the harmonic component. In the present embodiment, the harmonic components to be adjusted are the second harmonic wave and the third harmonic wave, and the harmonic components are sequentially adjusted. However, for convenience, only the second harmonic wave will be described in the following procedure.

  The determination/processing unit 24 phase-detects the output of the second bandpass filter 22 with the output of the second oscillating unit 36 as a reference to obtain the phase information of the second harmonic and further compares it with the phase ii. , It is determined whether the phases match (step S9).

  If the phases do not match (step S9:≠phase ii), the capacitance of the variable capacitor of the antenna unit 4 is adjusted until the phases match (step S10→step S9). If the phases match (step S9:=phase ii), the output of the second bandpass filter 22 is amplitude-detected to obtain the intensity information of the second harmonic, and further compared with the signal intensity ii. , It is determined whether the intensities match (step S11).

  If the strengths do not match (step S11: ≠ signal strength ii), the capacitance of the variable capacitor of the matching circuit unit 34 is adjusted until the strengths match (steps S12→S11). If the intensities match (step S11:=signal intensity i), the output of the second bandpass filter 22 is phase-detected again with the output of the second oscillating unit 36 as the reference, and the second harmonic The phase information of is acquired and compared with the phase ii to determine whether the phases match (step S13).

  If the phases do not match (step S13:≠phase ii), the capacitance of the variable capacitor of the antenna unit 4 is adjusted (step S14), and the process returns to step S3. By performing this procedure, it is possible to correct the phase shift when the phase of the second harmonic wave is matched by the phase adjustment and then the phase is shifted by the intensity adjustment.

  If the phases match (step S13:=phase ii), the fundamental wave is adjusted again. That is, the determination/processing unit 24 phase-detects the output of the first band-pass filter 21 with the output of the first oscillating unit 35 as a reference to obtain the phase information of the fundamental wave and further compare it with the phase i. Then, it is determined whether the phases match (step S15).

  If the phases do not match (step S15: ≠ phase i), the capacitance of the variable capacitor of the antenna unit 4 is adjusted (step 16), and the process returns to step S3. If the phases match (step S15:=phase i), the output of the first bandpass filter 21 is amplitude-detected to acquire the intensity information of the fundamental wave, and further compared with the signal intensity i, It is determined whether the intensities match (step S17).

  If the intensities do not match (step S17: ≠ signal intensity i), the capacitance of the variable capacitor of the matching circuit unit 34 is adjusted (step S18), and the process returns to step S5. If the intensities match (step S17:=signal intensity i), the inconsistent state is resolved, so the control unit 2 sends data to the modulation unit 31, modulates the carrier wave, and starts communication. (Step S19: R/W communication starts).

As described in detail above, according to the wireless communication device according to the embodiment of the present invention, when an inconsistent state is detected during use, it is possible to correct to an optimum adjustment state in a no-load state, The following effects (1) to (5) can be obtained.
(1) Since the deviation of the resonance frequency is corrected, it is possible to prevent the deterioration of communication performance.
(2) Since the fluctuation of the output impedance of the radio frequency amplifier is corrected, the consumption current is stable. As a result, it is possible to prevent the temperature of the device from rising due to an increase in current consumption.
(3) The emission of harmonic noise can be limited by suppressing the intensity of harmonics.
(4) Stable communication is possible even in an installation environment in which there is always a load (for example, it is installed in an electronic device or installed in a place where a metal object is present nearby).
(5) Even if there are a plurality of types of non-contact IC cards that have different effects on the output impedance of the radio frequency amplification unit as non-contact IC cards that are communication partners, communication can be performed in an optimal state for each. ..

The above-described embodiment is a preferred embodiment of the present invention, and various modifications can be made without departing from the gist of the present invention. That is, for example, the following modifications (1) to (6) are possible.
(1) Phase adjustment and intensity adjustment are performed only on the fundamental wave.
(2) Phase adjustment and intensity adjustment are performed on the fundamental wave and the second harmonic wave.
(3) The matching circuit unit 34 is composed of a resonance circuit unit and an impedance circuit unit, phase adjustment is performed by the resonance circuit unit, and strength adjustment is performed by the impedance circuit unit.
(4) The resonance frequency is adjusted by adjusting the inductance such as changing the length of the antenna coil.
(5) By multiplying the output of the first oscillating unit 35, a second harmonic wave and a third harmonic wave are generated.
(6) The first to third bandpass filters 21 to 23 are provided in the transmitting/receiving unit 3.

DESCRIPTION OF SYMBOLS 1... Reader/writer device, 2... Control part, 4... Antenna part, 31... Modulation part, 32... Radio frequency amplification part, 34... Matching circuit part.

Claims (5)

An antenna section composed of a resonance circuit composed of an antenna coil and a capacitor,
A modulator for modulating a carrier wave,
A radio frequency amplifier for amplifying the output of the modulator,
A matching circuit unit for matching the radio frequency amplification unit and the antenna unit;
A no-load information storage unit that stores information indicating a no-load phase and a no-load intensity that are the phase and intensity of the output of the radio frequency amplification unit in a no-load state,
An in-use information detecting means for detecting an in-use phase and an in-use intensity, which are phases and intensities of the radio frequency amplification section during use,
The use phase, the use strength, respectively, so as to be equal to the no-load phase, the no-load strength, the resonance frequency of the resonant circuit, adjusting means for adjusting the impedance of the matching circuit unit,
Wireless communication device having. The wireless communication device according to claim 1,
The wireless communication device, wherein the no-load phase, the no-load intensity, the in-use phase, and the in-use intensity are for the same frequency as the carrier wave. The wireless communication device according to claim 1,
The wireless communication device, wherein the no-load phase, the no-load intensity, the in-use phase, and the in-use intensity are for the same frequency as the carrier wave and its harmonics. The wireless communication device according to any one of claims 1 to 3,
The wireless communication device, wherein the matching circuit section has a resonance circuit section and an impedance circuit section, and the phase of the resonance circuit section is adjusted by adjusting the resonance circuit section and the strength is adjusted by adjusting the impedance circuit section. The wireless communication device according to any one of claims 1 to 4,
The wireless communication device, wherein the adjusting means performs adjustment in the order of phase matching and strength matching, and again performs phase matching when the phases are shifted after the strength matching.

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