Wireless transmitting receiving apparatus and control method thereof

Abstract

To suppress temperature rise during polling processing without impairing user convenience in a wireless transmitting receiving apparatus that communicates with a wireless communication medium such as an IC card using NFC (near field communication) technique.SOLUTION: A wireless transmitting receiving apparatus, during polling processing for searching for a wireless communication medium by transmitting a wireless signal including a polling command, determines whether or not a temperature of the wireless transmitting receiving apparatus has increased to reach a first threshold temperature (for example, 44°C) while transmitting the wireless signal at a first duty ratio (for example, 50%), and if it is reached, switches a transmission duty ratio of the wireless signal to a second duty ratio (for example, 33%) that is lower than the first duty ratio.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wireless transceiver device typified by a non-contact card reader that communicates with a wireless communication medium such as an IC card using near field communication (NFC) technology, and a control method thereof.

Background Art

[0002] As an example of a wireless transceiver device using NFC technology, there is a non-contact card reader (also referred to as a non-contact card reader / writer). The non-contact card reader performs non-contact communication, that is, wireless communication, with a wireless communication medium approaching a position near the card reader, for example, a position within several centimeters to a dozen or so centimeters. The wireless communication medium includes an antenna for performing wireless communication with the wireless transceiver device and an IC chip. As an example of the wireless communication medium, an NFC-compatible IC (integrated circuit) card can be mentioned, and as a specific example, a so-called credit card compatible with touch payment can be mentioned. The wireless communication medium may be a smartphone or various tags incorporating an NFC-compatible IC chip. The wireless communication medium may not have a built-in power source, and when it does not have a built-in power source, it receives the wireless power emitted from the wireless transceiver device and uses it as the operating power of the wireless communication medium.

[0003] As described in Patent Document 1, in order to start communication with a wireless communication medium existing in the vicinity, a wireless transceiver emits a wireless signal including a polling command and waits for the wireless communication medium to approach the vicinity of the wireless transceiver. For example, when a user holds the wireless communication medium and approaches the wireless transceiver, the wireless communication medium can receive the wireless signal including the polling command and transmit a wireless signal including a response to the received polling command to the wireless transceiver. By receiving the wireless signal including the response, the wireless transceiver detects the presence of the wireless communication medium in the vicinity and starts data communication with the wireless communication medium. The process from the emission of the wireless signal including the polling command to the detection of the wireless communication medium is called polling process. When it is not known at what timing the user approaches the wireless communication medium to the wireless transceiver, the wireless transceiver needs to continuously execute the polling process.

[0004] When the wireless communication medium uses the wireless power from the wireless transceiver as the operating power, the wireless signal including the polling command needs to be transmitted with relatively large power. As a result, heat generation in the wireless transceiver, for example, heat generation in the antenna circuit and the transceiver circuit connected to the antenna circuit increases. Heat generation also increases when performing complex processing to receive the response wireless signal from the wireless communication medium. Especially when continuously performing the polling process, heat generation in the wireless transceiver cannot be ignored, and there is a risk that the temperature of the wireless transceiver exceeds the allowable maximum temperature defined for the wireless transceiver. Therefore, it is necessary to suppress heat generation in the polling process.

[0005] Although not related to NFC technology, as a technology for suppressing heat generation in a wireless transceiver, Patent Document 2 discloses detecting the temperature of a power amplifier provided in a transceiver circuit and reducing the power of the baseband signal of a wireless signal according to the detected temperature value, that is, reducing the transmission power. Further, Patent Document 3 discloses that in a combined diversity receiver having a plurality of receiving units, the temperature inside the receiver is detected, and when the temperature rises, the number of branches used for reception is reduced, and the power supply of the branches not used for reception is cut off.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] In a wireless transceiver based on NFC technology, when reducing the transmission power of a wireless signal as described in Patent Document 2 to reduce the heat generation amount during polling processing, if the wireless communication medium is not extremely close to the wireless transceiver, the wireless communication medium cannot be detected, resulting in the loss of the advantage of communicating without contact. Also, since sufficient operating power cannot be obtained, there is a possibility that the wireless communication medium cannot transmit a response wireless signal.

[0008] An object of the present invention is to provide a wireless transceiver and its control method capable of suppressing a temperature rise during polling processing without impairing the convenience of the user.

Means for Solving the Problems

[0009] According to one aspect, a wireless transceiver is a wireless transceiver that communicates with a wireless communication medium by near field communication (NFC), and includes an antenna circuit, a temperature sensor that detects the temperature of the wireless transceiver, and a control unit that performs a polling process of transmitting a first wireless signal including a polling command from the antenna circuit to search for the wireless communication medium. When the temperature detected by the temperature sensor rises and reaches a first threshold temperature while transmitting the first wireless signal at a first duty ratio, the control unit switches the transmission duty ratio of the first wireless signal to a second duty ratio smaller than the first duty ratio.

[0010] According to one aspect, a control method for a wireless transceiver is a control method for controlling a wireless transceiver that communicates with a wireless communication medium by NFC. During the execution of a polling process of transmitting a first wireless signal including a polling command to search for the wireless communication medium, when the temperature of the wireless transceiver rises and reaches a first threshold temperature while transmitting the first wireless signal at a first duty ratio, the transmission duty ratio of the first wireless signal is switched to a second duty ratio smaller than the first duty ratio.

Effect of the Invention

[0011] According to the present invention, in a wireless transceiver that communicates with a wireless communication medium using NFC technology, it is possible to suppress the temperature rise during the polling process without impairing the convenience of the user.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0013] Next, embodiments of the present invention will be described with reference to the drawings. The present invention relates to a wireless transceiver that communicates with a wireless communication medium using NFC (Near Field Communication) technology. A wide variety of wireless transceivers to which the present invention can be applied are assumed, and a wide variety of wireless communication media are also assumed. Here, it will be described on the assumption that the wireless communication medium is an NFC-compatible IC card typified by a credit card compatible with touchless payment, and the wireless transceiver is a non-contact card reader. Of course, the wireless communication medium is not limited to an IC card as long as it is compatible with NFC, and the wireless transceiver is not limited to a non-contact card reader (or card reader / writer). Wireless communication between the wireless transceiver and the wireless communication medium is usually performed using a high-frequency magnetic field or electromagnetic waves, but it may use a high-frequency electric field. In the following description, it is assumed that wireless communication between the wireless transceiver and the wireless communication medium is performed using a high-frequency magnetic field having a frequency of, for example, 13.56 MHz.

[0014] FIG. 1 shows a non-contact card reader 10 according to an embodiment. The card reader 10 is a wireless transceiver connected to a host device 30 such as a POS (Point of Sales) terminal or a server, and mediates data communication between the host device 30 and the IC card 50 by performing non-contact communication with the IC card 50, which is a wireless communication medium, using NFC technology. The card reader 10 includes a control unit 11 that is connected to the host device 30 and controls the operation of the card reader 10, a power supply circuit 12, a transceiver circuit 13, an antenna circuit 14 connected to the transceiver circuit 13, a storage unit (memory) 15 connected to the control unit 11, and a temperature sensor 16 that detects the temperature inside the card reader 10 and outputs the detected value to the control unit 11.

[0015] The control unit 11 is composed of, for example, a microcomputer or a microprocessor, and the programs and various parameters necessary for its operation are stored in the storage unit 15. The power supply circuit 12 supplies power to the control unit 11 and the transmission / reception circuit 13. The transmission / reception circuit 13 is provided with, for example, an oscillation circuit that generates a carrier wave, a modulation circuit that modulates the carrier wave based on a signal from the control unit 11, a power amplifier that amplifies the output of the modulation circuit and outputs it to the antenna circuit 14, and a reception circuit that demodulates the radio signal received by the antenna circuit 14 and outputs it to the control unit 11. The antenna circuit 14 includes a coil for transmission / reception and a resonance circuit connected to the coil, etc., emits a radio signal toward the surroundings, and also receives a radio signal from the IC card 50. The temperature sensor 16 detects the temperature inside the card reader 10, and it is preferably arranged near a location in the card reader 10 where a large amount of heat is generated, for example, near the transmission / reception circuit 13 or the antenna circuit 14.

[0016] Next, the operation of the card reader 10 shown in FIG. 1 will be described, focusing particularly on the polling process. In order to establish communication between the card reader 10 and the IC card 50, the card reader 10 first needs to search for and detect the IC card 50 in its vicinity, and for this purpose, a polling process is performed. In the polling process, a radio signal including a polling command is transmitted from the card reader 10, and a radio signal from the IC card 50 including a response to the polling command is awaited. In the following description, the radio signal including the polling command is called a search signal, and the radio signal including the response is called a response signal.

[0017] In the card reader 10, since it is not known when the IC card 50 will approach the card reader 10, it is necessary to continuously perform polling processing. On the other hand, when the polling processing is being performed, the transmission / reception circuit 13 and the antenna circuit 14, which are heat sources, are operating. If the polling processing is continuously executed, the temperature inside the card reader 10 may rise and exceed the defined maximum allowable temperature. Therefore, the card reader 10 of the present embodiment intermittently transmits a search signal during the execution of the polling processing under the control of the control unit 11. That is, after transmitting the search signal for a predetermined transmission time a, the transmission of the search signal is stopped during the subsequent pause period c, and this is repeated. Since the power consumption in the transmission / reception circuit 13 and the antenna circuit 14 is almost zero during the pause period c, the amount of heat generation can be reduced. If the period of repetition is T, T = a + c holds. If the transmission duty ratio, that is, the duty ratio of the transmission of the search signal, is D, D = a / T is represented by.

[0018] Since a certain amount of time is required for the IC card 50 that has received the search signal to transmit a response signal and for the card reader 10 to receive and process the response signal from this IC card 50, there is a lower limit for the transmission time a, and the transmission time a needs to be, for example, 150 milliseconds or more. Also, if the pause period c is long, when the user brings the IC card 50 close to the card reader 10, the card reader 10 may not be able to detect the IC card 50 immediately, which deteriorates the usability of the IC card 50 for the user. To improve the usability and enhance the convenience for the user, the duty ratio can be increased. However, in that case, the temperature rise in the card reader 10 cannot be ignored.

[0019] In this embodiment, in advance, a first duty ratio and a second duty ratio smaller than the first duty ratio are defined with respect to the duty ratio of transmitting a search signal, and a first threshold temperature is defined based on the maximum allowable temperature of the card reader 10. When the temperature detected by the temperature sensor 16 rises and reaches the first threshold temperature while the control unit 11 is transmitting the search signal at the first duty ratio, the control unit 11 switches the transmission duty ratio from the first duty ratio to the second duty ratio and continues to transmit the search signal. By performing such control, it is possible to suppress the temperature rise of the card reader 10 while ensuring the convenience for the user. When the card reader 10 is activated, the temperature measured by the temperature sensor 16 is sufficiently low and far below the first threshold temperature. Therefore, when starting the polling process, the control unit 11 may transmit the search signal at the first duty ratio. The first duty ratio is defined, for example, as a duty ratio such that when the transmission of the search signal at the first duty ratio is continued, the temperature of the card reader 10 exceeds its maximum allowable temperature. The second duty ratio is defined, for example, as a duty ratio such that even when the transmission of the search signal at the second duty ratio is continued, the temperature of the card reader 10 does not exceed its maximum allowable temperature. By defining the first and second duty ratios in this way, it is possible to further enhance the convenience for the user while ensuring that the temperature of the card reader 10 does not exceed its maximum allowable temperature.

[0020] Furthermore, in the present embodiment, after determining a second threshold temperature lower than the first threshold temperature in advance, the control unit 11 switches the transmission duty ratio to the second duty ratio, and then, when the temperature detected by the temperature sensor 16 drops to the second threshold temperature, the control unit 11 may switch the transmission duty ratio of the search signal from the second duty ratio to the first duty ratio. When the duty ratio is the second duty ratio, the time until the IC card 50 is detected when the IC card 50 is brought closer is longer than when the duty ratio is the first duty ratio. However, by switching the duty ratio to the first duty ratio when the temperature drops to the second threshold temperature, the ratio of the period during which the duty ratio is the second duty ratio becomes smaller, and the convenience for the user is further improved. The second threshold temperature is set to, for example, a temperature slightly higher than the temperature that the card reader 10 finally reaches when the transmission of the search signal at the second duty ratio is continued.

[0021] Hereinafter, the control in the present embodiment will be described based on a specific example. Here, it is assumed that the first duty ratio is 50%, the second duty ratio is 33%, and the allowable maximum temperature of the card reader 10 is 45°C. The first threshold temperature is set to 44°C with a margin with respect to the allowable maximum temperature, and the second threshold temperature is set to 40°C. When the card reader 10 is activated, in step 101, the control unit 11 first starts transmitting the search signal at a first duty ratio of 50%. Then, in step 102, the control unit 11 determines whether or not a response signal has been received, that is, whether or not the card reader 10 has detected the IC card 50 which is the wireless communication medium. If the control unit 11 has detected the IC card 50, it proceeds to step 103, terminates the polling process, and starts the data communication process. In the data communication process, the host device 30 can perform data communication with the IC card 50 via the card reader 10. For example, if the IC card 50 is a credit card compatible with touchless payment, a transaction process is performed. When the data communication process is completed, the control unit 11 repeats the process from step 101.

[0022] When the IC card 50 is not detected in step 102, the control unit 11 acquires a temperature measurement value from the temperature sensor 16 in step 104, and determines in step 105 whether the current transmission duty ratio is 50% (i.e., the first duty ratio). When the duty ratio is 50%, the control unit 11 determines in step 106 whether the temperature measured by the temperature sensor 16 is 44°C or higher (i.e., the first threshold temperature). When the temperature is less than 44°C, the process from step 102 is repeated. When the temperature is 44°C or higher, the transmission duty ratio is switched to 33% (i.e., the second duty ratio), and then the process from step 102 is repeated. Also, when the temperature is less than 44°C in step 105, the control unit 11 determines in step 108 whether the temperature measured by the temperature sensor 16 is 40°C or lower (i.e., the second threshold temperature). When the temperature exceeds 40°C, the process from step 102 is repeated. When the temperature is 40°C or lower, the transmission duty ratio is switched to 50%, and then the process from step 102 is repeated. By implementing such control, in the card reader 10, while maintaining the temperature in the range of 40°C or higher and less than 44°C, the transmission of the search signal at the first duty ratio and the transmission of the search signal at the second duty ratio are alternately repeated.

[0023] FIG. 3 is a diagram showing the relationship between the duty ratio of transmission and the temperature of the card reader 10 in the specific example described with reference to FIG. 2. FIG. 3(a) is a graph showing the transmission status of the search signal when the duty ratio is 100%. When the duty ratio is 100%, the transmission of the search signal starts along with the start of the polling process, and thereafter, the transmission of the search signal continues without interruption. FIG. 3(b) shows the transmission status of the search signal when the duty ratio is 50%. When the duty ratio is 50%, a transmission time a of 180 milliseconds and a pause period of 180 milliseconds appear alternately, and the repetition period T is 360 milliseconds. Similarly, FIG. 3(c) shows the transmission status of the search signal when the duty ratio is 33%. When the duty ratio is 33%, the transmission time a is 180 milliseconds as in the case where the duty ratio is 50%, but the pause period is 360 milliseconds, and the repetition period T is 540 milliseconds.

[0024] FIG. 3(d) shows how the temperature of the card reader 10, i.e., the temperature detected by the temperature sensor 16, changes according to the elapsed time from the start of the polling process, assuming that the ambient temperature is 25° C. (room temperature). As described above, the maximum allowable temperature of the card reader 10 is assumed to be 45° C. When the duty ratio is 100%, the temperature reaches approximately 65° C. (the maximum temperature) 90 minutes after the start of the polling process, which greatly exceeds the maximum allowable temperature of the card reader 10. Even when the duty ratio is 50%, the temperature reaches 50° C. after 90 minutes, which also exceeds the maximum allowable temperature. On the other hand, when the duty ratio is 33%, the temperature after 90 minutes is 39° C., which is below the maximum allowable temperature. Therefore, 50% can be selected as the first duty ratio, which is a duty ratio at which the temperature of the card reader 10 exceeds the maximum allowable temperature when the transmission of the search signal is continued, and 33% can be selected as the second duty ratio, which is a duty ratio at which the temperature of the card reader 10 does not exceed the maximum allowable temperature even when the transmission of the search signal is continued. The second threshold temperature is preferably higher than the temperature reached when the transmission of the search signal at the second duty ratio is continued so that the switching from the second duty ratio to the first duty ratio surely occurs when the temperature of the card reader 10 has decreased to some extent from the first threshold temperature. From this viewpoint, in the present embodiment, 40° C. is selected as the second threshold temperature.

[0025] FIG. 4 is a diagram for explaining the change in the temperature of the card reader 10 and the switching of the transmission duty ratio when the control described with reference to FIG. 2 is performed. (a) shows, by graph, the change in the temperature of the card reader 10 from the start of the polling process, and (b) shows, by graph, the switching of the duty ratio by showing the transmission status of the search signal during the period indicated by arrow b in FIG. 4(a). As shown in the figure, the temperature inside the card reader 10 is 25° C. at the start of the polling process. By transmitting a search signal with a duty ratio of 50%, the temperature inside the card reader 10 rises and eventually reaches the first threshold temperature of 44° C. Then, the transmission duty ratio switches to 33%, and the temperature inside the card reader 10 begins to decrease. When the temperature drops to the second threshold temperature of 40° C., this time the duty ratio switches to 50%, and again, the temperature inside the card reader 10 begins to rise. Thereafter, the switching of the duty ratio and the rise and fall of the temperature of the card reader 10 are repeated between 40° C. and 44° C. The specific transmission status of the search signal at that time is as shown in FIG. 4(b).

[0026] In the card reader 10 of the present embodiment described above, while maintaining the temperature of the card reader 10 between the first threshold temperature (for example, 44° C.) and the second threshold temperature (for example, 40° C.), the transmission of the search signal at the first duty ratio and the transmission of the search signal at the second duty ratio are repeated. Therefore, it is possible to ensure the convenience of the user while suppressing the temperature rise of the card reader 10.

[0027] As described above, the configuration for implementing the present invention has been explained. However, the above technology can be configured as follows.

[0028] (1) A wireless transceiver that communicates with a wireless communication medium by short-range wireless communication, an antenna circuit, a temperature sensor that detects the temperature of the wireless transceiver, a control unit that performs a polling process of transmitting a first wireless signal including a polling command from the antenna circuit to search the wireless communication medium, and having When the temperature detected by the temperature sensor rises and reaches a first threshold temperature while the control unit is transmitting the first radio signal at a first duty ratio, the radio transceiver switches the transmission duty ratio of the first radio signal to a second duty ratio that is smaller than the first duty ratio.

[0029] (2) The first duty ratio is determined as a transmission duty ratio at which, if the transmission of the first radio signal at the first duty ratio is continued, the temperature of the radio transceiver exceeds the maximum allowable temperature defined for the radio transceiver. The radio transceiver according to (1), wherein the second duty ratio is determined as a transmission duty ratio at which, even if the transmission of the first radio signal at the second duty ratio is continued, the temperature of the radio transceiver does not exceed the maximum allowable temperature.

[0030] (3) After the control unit switches the transmission duty ratio to the second duty ratio, if the temperature detected by the temperature sensor drops to a second threshold temperature that is lower than the first threshold temperature, the control unit switches the transmission duty ratio of the first radio signal from the second duty ratio to the first duty ratio. The radio transceiver according to (1) or (2).

[0031] (4) The radio transceiver according to any one of (1) to (3), wherein the control unit transmits the first radio signal at the first duty ratio when starting the polling process.

[0032] (5) When the control unit receives a second radio signal including a response to the polling command from the wireless communication medium, the control unit ends the polling process and starts data communication with the wireless communication medium. The radio transceiver according to any one of (1) to (4).

[0033] (6) The radio transceiver according to any one of (1) to (5), which is a non-contact type card reader to which the control unit is connected to a host device.

[0034] (7) A control method for controlling a wireless transceiver that communicates with a wireless communication medium by short-range wireless communication, when performing a polling process of transmitting a first wireless signal including a polling command to search for the wireless communication medium, if the temperature of the wireless transceiver rises and reaches a first threshold temperature while transmitting the first wireless signal at a first duty ratio, the transmission duty ratio of the first wireless signal is switched to a second duty ratio smaller than the first duty ratio.

[0035] (8) The first duty ratio is defined as a transmission duty ratio at which if the transmission of the first wireless signal at the first duty ratio is continued, the temperature of the wireless transceiver exceeds an allowable maximum temperature defined for the wireless transceiver, The second duty ratio is defined as a transmission duty ratio at which if the transmission of the first wireless signal at the second duty ratio is continued, the temperature of the wireless transceiver does not exceed the allowable maximum temperature. The control method according to (7).

[0036] (9) After switching the transmission duty ratio to the second duty ratio, if the temperature of the wireless transceiver drops to a second threshold temperature lower than the first threshold temperature, the transmission duty ratio of the first wireless signal is switched from the second duty ratio to the first duty ratio. The control method according to (7) or (8).

[0037] (10) Transmitting the first wireless signal at the first duty ratio when starting the polling process. The control method according to any one of (7) to (9).

[0038] (11) When receiving a second wireless signal including a response to the polling command from the wireless communication medium, ending the polling process and starting data communication with the wireless communication medium. The control method according to any one of (7) to (10).

[0039] (12) The data communication according to the control method described in (11) is data communication between a host device to which the wireless transceiver is connected and the wireless communication medium.

[0040] According to the configurations shown in (1) and (7), until the temperature of the wireless transceiver reaches the first threshold temperature, a first duty ratio, which is a relatively large transmission duty ratio, is used to transmit a first wireless signal (i.e., a search signal). Therefore, while suppressing the temperature rise of the wireless transceiver, the convenience of the user can be ensured.

[0041] When the first and second duty ratios are determined as shown in (2) and (8), the convenience of the user can be further enhanced while ensuring that the temperature of the wireless transceiver does not exceed its allowable maximum temperature.

[0042] As shown in (3) and (9), when the temperature drops to the second threshold temperature, by switching the duty ratio to the first duty ratio, the ratio of the period of the second duty ratio, which is a relatively small duty ratio, can be reduced, and the convenience of the user is further improved.

[0043] Since it is considered that the temperature of the wireless transceiver is sufficiently low at the start of the polling process, the configurations shown in (4) and (10) can be adopted, whereby the convenience of the user can be ensured even at the start of the polling process.

[0044] According to the configurations shown in (5) and (11), it is possible to smoothly shift from the polling process to data communication processing for transactions using a credit card or the like.

[0045] According to the configurations shown in (6) and (12), when the wireless communication medium is, for example, a credit card compatible with touch payment, it is possible to surely establish data communication between the host device and the wireless communication medium without impairing the convenience of the user.

Description of Reference Numerals

[0046] 10…Card reader; 11…Control unit; 12…Power supply circuit; 13…Transmission / reception circuit; 14…Antenna circuit; 15…Memory unit; 16…Temperature sensor; 30…Host device; 50…IC card.

Claims

1. A wireless transceiver that communicates with a wireless communication medium by short-range wireless communication, comprising: an antenna circuit; a temperature sensor that detects the temperature of the wireless transceiver; a control unit that performs polling processing for transmitting a first wireless signal including a polling command from the antenna circuit to search for the wireless communication medium; wherein when the temperature detected by the temperature sensor rises and reaches a first threshold temperature while the first wireless signal is being transmitted at a first duty ratio, the control unit switches the transmission duty ratio of the first wireless signal to a second duty ratio smaller than the first duty ratio. A wireless transceiver.

2. The first duty ratio is determined as a transmission duty ratio at which the temperature of the wireless transceiver exceeds the allowable maximum temperature defined for the wireless transceiver when the transmission of the first wireless signal at the first duty ratio is continued, The second duty ratio is determined as a transmission duty ratio at which the temperature of the wireless transceiver does not exceed the allowable maximum temperature even when the transmission of the first wireless signal at the second duty ratio is continued. The wireless transceiver according to claim 1.

3. After the control unit switches the transmission duty ratio to the second duty ratio, when the temperature detected by the temperature sensor drops to a second threshold temperature lower than the first threshold temperature, the control unit sets the transmission duty ratio of the first wireless signal to the second duty ratio. The wireless transceiver according to claim 1 or 2, which switches from the duty ratio to the first duty ratio.

4. The control unit transmits the first wireless signal at the first duty ratio when starting the polling process. The wireless transceiver according to claim 1 or 2.

5. When the control unit receives a second wireless signal including a response to the polling command from the wireless communication medium, the control unit ends the polling process and starts data communication with the wireless communication medium. The wireless transceiver according to claim 1 or 2.

6. The wireless transceiver according to claim 1 or 2, which is a non-contact type card reader in which the control unit is connected to a host device.

7. A control method for controlling a wireless transceiver that communicates with a wireless communication medium by short-range wireless communication, comprising: During the implementation of polling processing for searching the wireless communication medium by transmitting a first wireless signal including a polling command, when the temperature of the wireless transceiver rises to reach a first threshold temperature while transmitting the first wireless signal at a first duty ratio, a control method for switching the transmission duty ratio of the first wireless signal to a second duty ratio smaller than the first duty ratio.

8. The first duty ratio is determined as a transmission duty ratio at which the temperature of the wireless transceiver exceeds the allowable maximum temperature defined for the wireless transceiver when the transmission of the first wireless signal at the first duty ratio is continued, The second duty ratio is determined as a transmission duty ratio at which the temperature of the wireless transceiver does not exceed the allowable maximum temperature even if the transmission of the first wireless signal at the second duty ratio is continued. The control method according to claim 7.

9. After switching the transmission duty ratio to the second duty ratio, when the temperature of the wireless transceiver drops to a second threshold temperature lower than the first threshold temperature, the transmission duty ratio of the first wireless signal is switched from the second duty ratio to the first duty ratio. The control method according to claim 7 or 8.

10. Transmitting the first wireless signal at the first duty ratio when starting the polling process. The control method according to claim 7 or 8.

11. When receiving a second wireless signal including a response to the polling command from the wireless communication medium, ending the polling process and starting data communication with the wireless communication medium. The control method according to claim 7 or 8.

12. The data communication is data communication between the host device to which the wireless transceiver is connected and the wireless communication medium. The control method according to claim 11.

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