JP6529919B2 - Wireless transmission apparatus and method - Google Patents

Description

  The present invention relates to a wireless transmission device and method.

  An RFID (Radio Frequency IDentification) system is known as one system of wireless communication. In RFID, a passive type (type without power supply) IC (integrated circuit) chip called RFID tag is attached to a commodity for sale etc., and an antenna formed by, for example, metal printing is connected to the RFID tag. The RFID tag includes a rectifier circuit, a command demodulation circuit, a memory circuit, a modulation circuit, and the like in an IC chip. At the time of reading the RFID tag, for example, a radio wave (or an electromagnetic wave) in the UHF band is transmitted from the RFID tag reader to the RFID tag attached to the product. The radio wave includes a preamble by a non-modulated continuous wave (CW: Continuous Wave) signal, a modulated wave signal modulated by a command bit string, and a carrier by a CW signal. The rectifier circuit in the RFID tag generates a DC power supply current by rectifying the radio wave of the preamplifier received by the antenna. The DC power supply current starts the operation of the demodulation circuit, the memory, and the modulation circuit in the RFID tag. The demodulation circuit interprets the command contained therein by demodulating the modulation wave signal received following the preamplifier. Furthermore, the modulation circuit changes the impedance of the receiving circuit based on the bit string of the ID information such as a product read from the memory circuit at the timing of receiving the CW signal, for example, according to the interpretation result of the command. As a result, for example, the response signal of the RFID tag which has modulated the ID information is superimposed on the reflected wave of the CW signal, and is received by the antenna of the RFID tag reader. The RFID tag reader receives ID information from the RFID tag by demodulating the received response signal. Here, in addition to the RFID tag, the contactless IC card is also accessed by the same communication method, and therefore, in the description of this specification, the RFID method will be described as including the contactless IC card method.

  In the RFID system, when an RFID tag reader transmits a radio wave, a modulated wave or CW (non-modulated continuous wave) signal is amplified by a transmission amplifier and then transmitted from an antenna. A FET (Field Effect Transistor) is usually used as the transmission amplifier. This FET is generally driven by a fixed bias voltage in accordance with the maximum output of the transmission amplifier.

  In this driving method, the FET operating point is appropriate at the maximum output, but at low output, the FET operating point is higher than necessary, and the transmission amplifier is driven in the over-spec linearity region, resulting in power consumption. It gets bigger. In addition, with this drive method, the inrush current immediately after turning on the transmission amplifier also becomes large, which tends to be fatal in a battery-operated RFID tag reader. However, in the RFID method, since very weak radio waves are transmitted and received, distortion of the transmission amplifier tends to be a problem, and the transmission amplifier must be operated at a high operating point when communicating with the RFID tag.

  For such power consumption problems, conventionally, the range of the transmission power level required to operate the transmitter is divided into a plurality of sub-ranges based on statistical distribution, and for example, the bias voltage There is known a technology for reducing power consumption by switching between “or“ low ”(for example, the technology described in Patent Document 1).

JP, 2015-039190, A

  However, in the prior art in which the bias voltage is simply switched for each range of the transmission power level, for example, the bias voltage corresponds to each transmission stage in each transmission stage at transmission off in transmission by RFID method, modulation wave transmission, and CW transmission. When switching to the target bias voltage, a sudden change in the bias voltage may cause a large inrush current at the timing of switching, which shortens the operation time and the life of the RFID tag reader battery. There is a problem that there is a possibility that the power supply voltage inside the device may be lowered.

  Then, an object of the present invention is to suppress both power consumption and inrush current.

  In one example of the aspect, a transmission amplifier unit that amplifies radio waves and transmits them from an antenna, a current monitor unit that monitors the current consumption of the transmission amplifier units, and a current monitor unit that monitors each of a plurality of transmission stages of radio waves. The transmission amplifier with a target control voltage corresponding to the transmission power set for the radio wave and whose transmission stage is to be controlled while controlling the consumption current to be equal to or less than the specified value. And a transmission amplifier unit voltage control unit that controls the transmission amplifier unit by gradually changing any control voltage in the unit.

  According to the present invention, both power consumption and inrush current can be suppressed.

FIG. 2 is a block diagram of an embodiment of a wireless transmission device. It is a figure which shows the data structural example of a target bias voltage table. It is a figure which shows the relationship example of a bias voltage and drain current. It is a flow chart which shows an example of control processing at the time of shifting to a transmitting stage of a modulation wave from transmission OFF at the time of starting transmission. It is a flow chart which shows an example of control processing when it shifts to a CW transmission stage and shifts to reception waiting of a response signal from an RFID tag after transmission of a modulation wave is completed. It is a flow chart which shows an example of control processing at the time of shifting to transmission OFF. It is explanatory drawing of the effect of rush current suppression in this embodiment. FIG. 7 is a block diagram of another embodiment of a wireless transmission device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a wireless transmission device 100, which may be, for example, an RFID tag reader device or an RFID tag reader / writer device. A CPU (central processing unit) 101 is a processor that performs signal processing of transmission and reception of radio waves.

  First, the transmission signal generated by the CPU 101 is converted to an analog transmission signal by the DAC 102 (# 1). The transmission baseband processing circuit 104 performs, for example, signal processing for improving spurious characteristics on an analog transmission signal output from the DAC 102 (# 1). The transmission mixer 105 modulates the analog transmission signal output from the transmission baseband processing circuit 104 with the carrier signal output from the local oscillation circuit (hereinafter referred to as “local oscillator”) 111, and outputs the modulated signal as a modulation wave transmission signal. . The transmission mixer 105 outputs the carrier signal output from the local oscillator 111 as it is as the CW signal at the timing when the analog transmission signal is not output. The transmission amplifier 106 amplifies the transmission signal output from the transmission mixer 105. A transmission signal output from the transmission amplifier 106 is sent to the antenna 108 by the circulator 107, and is transmitted from the antenna 108 to an RFID tag (not shown).

  Next, after the response signal from the RFID tag is received by the antenna 108, it is input to the receiving circuit by the circulator 107. The received signal is demodulated by the reception mixer 109 using the carrier signal from the local oscillator 111. The demodulated reception signal is subjected to signal processing such as noise removal in the reception baseband processing circuit 110, converted into a digital reception signal in the ADC 103 (# 2), and processed by the CPU 101.

  Next, the wireless transmission device 100 according to the present embodiment has a function of monitoring the current consumption of the transmission amplifier 106 (current monitoring unit). For example, the monitor function is connected to both terminals of a low resistance 112 (hereinafter referred to as “low resistance”) having a low resistance value inserted in series with the power supply line supplied to the transmission amplifier 106 and the low resistance 112. Differential amplifier 113 is provided. The value of the current supplied to the transmission amplifier 106 obtained as the output of the differential amplifier 113 is converted into a digital value by the A / D converter 212 (# 1) and input to the CPU 101.

  In addition, the wireless transmission device 100 according to the present embodiment includes the DAC 102 (# 2) that converts the digital value of the bias voltage sequentially calculated by the CPU 101 into an analog value. The analog bias voltage output from the DAC 102 (# 2) is supplied as the gate-source voltage of the FET that constitutes the transmission amplifier 106.

  Furthermore, in the wireless transmission device 100 according to the present embodiment, the memory 114 connected to the CPU 101 stores a target bias voltage table (target control voltage table). FIG. 2 is a view showing an example of the data configuration of the target bias voltage table stored in the memory 114. As shown in FIG. As shown in FIG. 2, in the target bias voltage table, transmission (transmission stage of modulation wave), reception (transmission stage of CW), and off (transmission stage of transmission / reception off) are performed for each required transmission power. Holds the digital value of the target bias voltage corresponding to each transmission stage of. The target bias voltage is obtained by driving the transmission amplifier 106 with a bias voltage corresponding to the target bias voltage for each required transmission power and for each transmission stage during transmission, reception, and off. The parameter is predetermined so as to optimize the current consumption of

  FIG. 3 is a diagram showing an example of the relationship between the bias voltage (voltage between gate and source) and the drain current in the FET of the transmission amplifier 106. As shown in FIG. As illustrated in FIG. 3, the drain current of the FET of the transmission amplifier 106, that is, the consumption current of the transmission amplifier 106 can be controlled by changing the bias voltage. In particular, in the transmission stage in which the wireless transmission device 100 transmits a CW signal, for example, to receive a response signal from an RFID tag, it is not necessary to consider modulation distortion, so the bias voltage in the transmission amplifier 106 can be lowered. . As a result, the current consumption can be suppressed according to the relationship example of FIG.

  The CPU 101 operating as a transmission amplifier unit voltage control unit controls the monitor value of the supply current to the transmission amplifier 106 input from the ADC 103 (# 1) to be less than or equal to a specified value for each of a plurality of transmission stages of radio waves. However, the target bias voltage to be supplied to the transmission amplifier 106 at the current transmission stage corresponding to the transmission power currently set for the radio wave is calculated while gradually changing the bias voltage as a target value. Specifically, the CPU 101 corresponds to the transmission power currently set for the radio wave, and the target bias voltage table in which the memory 114 stores the digital value of the target bias voltage corresponding to the current transmission stage. Get by reference. Then, the CPU 101 controls the monitor value of the current supplied to the transmission amplifier 106 to be equal to or less than a specified value, and sets the digital value of the acquired target bias voltage as a target value to the bias voltage supplied to the transmission amplifier 106. Calculate while changing the digital value gradually. The bias voltage calculated in this manner is supplied to the transmission amplifier 106 via the DAC 102 (# 2).

  As described above, in the present embodiment, the target bias voltage corresponding to the changed transmission stage is not suddenly supplied to the transmission amplifier 106 every time the transmission stage shifts, but the supply current to the transmission amplifier 106 is monitored. The value is supplied to the transmission amplifier 106 while being controlled so as to be equal to or less than the specified value and while the bias voltage is gradually changed to reach the target bias voltage of the new transmission stage. As a result, it is possible to set the consumption current in the transmission amplifier 106 to the optimum value for each transmission stage while suppressing the generation of inrush current in the transmission amplifier 106, and the entire consumption current of the wireless transmission device 100 is optimized. It is possible to

  A detailed example of the bias voltage control process described above will be described using the flowcharts of FIGS. 4 to 6.

  FIG. 4 is a flowchart showing an example of control processing when shifting from transmission off to the transmission stage of the modulation wave at the time of start of transmission. This control process is realized as an operation in which the CPU 101 of FIG. 1 executes a control process program at the time of transmission activation stored in, for example, a ROM (read only memory) (not shown).

  In FIG. 4, the CPU 101 first acquires a target bias voltage corresponding to transmission power for transmitting a radio wave from now on and corresponding to “upon transmission” by referring to the target bias voltage table stored in the memory 114 (see FIG. S401 of FIG. 4).

  Next, the CPU 101 turns on the transmission amplifier 106 in a state where the bias voltage is narrowed down via the DAC 102 (# 2) (S402 in FIG. 4).

Next, the CPU 101 waits for a fixed waiting time (S403 in FIG. 4).
Thereafter, the CPU 101 performs control such that the monitor value of the supply current to the transmission amplifier 106 input from the ADC 103 (# 1) becomes equal to or less than the specified value by a series of processes from S404 to S407 in FIG. The bias voltage is controlled such that the voltage value gradually increases with the target bias voltage acquired in S401 as the target value.

  In this series of processes, the CPU 101 first raises the bias voltage value by a predetermined value, and supplies the increased bias voltage value to the transmission amplifier 106 via the DAC 102 (# 2) (S404 in FIG. 4).

  Next, the CPU 101 acquires the monitor value of the current supplied to the transmission amplifier 106 input from the ADC 103 (# 1) (S405 in FIG. 4). Then, the CPU 101 determines whether the monitor value is less than or equal to a specified value (S406 in FIG. 4).

  If the determination in S406 is YES, the CPU 101 determines whether the bias voltage value has reached the target bias voltage value acquired in S401 (S407 in FIG. 4).

  If the determination in step S407 is NO, the CPU 101 returns to the process of step S404 in FIG. 4 and gradually increases the bias voltage value.

  If the determination in S406 is NO, the CPU 101 determines that the bias voltage may be raised too much and a rush current may be generated, and the bias voltage value is decreased by a predetermined value, and the lowered bias voltage value is reduced to DAC 102 (# 2) to the transmission amplifier 106 (S408 in FIG. 4). Thereafter, the CPU 101 returns to the process of S403, and after waiting for a fixed waiting time, executes the series of processes of S404 to S407 again.

  When the bias voltage value reaches the target bias voltage value and the determination in S407 is YES, the CPU 101 waits for a fixed waiting time, and when the transmission power of the transmission amplifier 106 is stabilized (S409 in FIG. 4), the DAC 102 (#) The transmission process is executed by outputting a transmission signal to the RFID tag in 1) (S410 in FIG. 4).

  By the control process described above, when the transmission amplifier 106 is turned on from the off state, the target bias voltage corresponding to the transmission stage of the modulation wave is not suddenly supplied to the transmission amplifier 106, but to the transmission amplifier 106. The bias voltage is supplied to the transmission amplifier 106 while being controlled so that the monitor value of the supply current is equal to or less than a specified value, and gradually changed so as to reach the target bias voltage of the transmission stage of the modulation wave. As a result, it is possible to set the consumption current in the transmission amplifier 106 to the optimum value of the transmission stage of the modulation wave while suppressing the generation of inrush current in the transmission amplifier 106.

  FIG. 5 is a flow chart showing an example of control processing when transitioning to the CW transmission stage and transitioning to reception waiting for a response signal from the RFID tag after transmission of the modulation wave is completed. Similar to the case of FIG. 4, this control process is realized as an operation in which the CPU 101 of FIG. 1 executes a control process program waiting for reception stored in, for example, a ROM (not shown).

  In FIG. 5, the CPU 101 first acquires a target bias voltage corresponding to the current transmission power and corresponding to “at reception” by referring to the target bias voltage table stored in the memory 114 (S501 in FIG. 5). ). When transmission becomes a CW transmission stage after completion of transmission and waiting for a response signal from the RFID tag, it is not necessary to consider modulation distortion, so a bias voltage lower than that at the time of transmission is set as the target bias voltage. The power consumption of the amplifier 106 can be reduced.

After S501, the CPU 101 waits for a fixed waiting time (S502 in FIG. 5).
Thereafter, the CPU 101 performs control such that the monitor value of the current supplied to the transmission amplifier 106 input from the ADC 103 (# 1) becomes equal to or less than a specified value by a series of processes from S503 to S506 in FIG. With the target bias voltage acquired in S501 as a target value, the bias voltage is controlled so that the voltage value gradually decreases.

  In this series of processing, the CPU 101 first lowers the bias voltage value by a predetermined value, and supplies the lowered bias voltage value to the transmission amplifier 106 via the DAC 102 (# 2) (S503 in FIG. 5).

  Next, the CPU 101 acquires the monitor value of the current supplied to the transmission amplifier 106 input from the ADC 103 (# 1) (S504 in FIG. 5). Then, the CPU 101 determines whether the monitor value is equal to or less than a specified value (S505 in FIG. 5).

  If the determination in S505 is YES, the CPU 101 determines whether the bias voltage value has reached the target bias voltage value acquired in S501 (S506 in FIG. 5).

  If the determination in S506 is NO, the CPU 101 returns to the process of S503 in FIG. 5 and gradually reduces the bias voltage value.

  If the determination in S505 is NO, the CPU 101 determines that the bias voltage may be lowered too much and a rush current may occur, and the bias voltage value is increased by a predetermined value, and the raised bias voltage value is set to the DAC 102 (# The signal is supplied to the transmission amplifier 106 through 2) (S507 in FIG. 5). Thereafter, the CPU 101 returns to the process of S502, and after waiting for a fixed waiting time, executes the series of processes of S503 to S506 again.

  If the bias voltage value reaches the target bias voltage value and the determination in S506 is YES, the CPU 101 waits for a fixed waiting time, and when the transmission power of the transmission amplifier 106 is stabilized (S508 in FIG. 5), the local generator By outputting only the unmodulated continuous wave signal to the transmission amplifier 106 from 111 through the transmission mixer 105, reception processing of the response signal from the RFID tag is executed (S509 in FIG. 5).

  If the target bias voltage corresponding to the unmodulated continuous wave transmission stage is suddenly supplied to the transmission amplifier 106 when transitioning from the modulated wave transmission stage to the unmodulated continuous wave transmission stage by the control processing described above. Instead, while the monitor value of the supply current to the transmission amplifier 106 is controlled to be less than the specified value, and while the bias voltage is gradually changed to reach the target bias voltage of the unmodulated continuous wave transmission stage, The signal is supplied to the transmission amplifier 106. Thereby, it is possible to set the consumption current in the transmission amplifier 106 to the optimum value of the transmission stage of the non-modulated continuous wave while suppressing the generation of the rush current in the transmission amplifier 106.

  FIG. 6 is a flowchart showing an example of control processing when shifting to transmission off. This control process is implemented as an operation in which the CPU 101 of FIG. 1 executes a transmission-off control processing program stored in, for example, a ROM (not shown), as in the case of FIGS. 4 and 5.

  The control process shown in FIG. 6 is basically the same as the control process of waiting for reception described above with reference to FIG. 5, and the process with the same step number as that of FIG. 5 shows the same process as that of FIG. That is, the CPU 101 obtains the target bias voltage value for off time by referring to the target bias voltage table stored in the memory 114 (S501 in FIG. 6), and after waiting for a fixed time (S502 in FIG. 6), The above target bias voltage is used as a target value while performing control such that the monitor value of the supply current to the transmission amplifier 106 input from the ADC 103 (# 1) becomes equal to or less than a specified value by a series of processes from S503 to S506 of 6. The bias voltage is controlled so that the voltage value gradually decreases.

  When the bias voltage value reaches the target bias voltage value when transmission is off and the determination in S506 of FIG. 6 is YES, the CPU 101 waits for a fixed waiting time (S508 in FIG. 6) and then turns off the transmission amplifier 106. Processing is executed (S601 in FIG. 6). Only the process of this portion is different from the process of S509 of FIG.

  According to the control process described above, when transitioning to transmission OFF, the target bias voltage corresponding to OFF is not suddenly supplied to the transmission amplifier 106, but the monitor value of the supply current to the transmission amplifier 106 is less than the specified value. And the bias voltage is supplied to the transmission amplifier 106 while being gradually changed to reach the target bias voltage at the time of OFF. As a result, it is possible to set the consumption current in the transmission amplifier 106 to the optimal value at the transmission off time while suppressing the generation of inrush current in the transmission amplifier 106.

  FIG. 7 is an explanatory view of the effect of the rush current suppression in the present embodiment. In FIG. 7, the horizontal axis represents time, and the vertical axis represents drain current (consumption current) of the FET of the transmission amplifier 106. Also, the characteristic 701 in the solid line shows the time change characteristic of the drain current (current consumption) in the control method of the bias voltage according to the present embodiment, and the characteristic 702 in the broken line is the conventional technology in which the bias voltage of the transmission amplifier 106 is simply switched. The time change characteristic of drain current (current consumption) is shown. Also, the specified value 703 is such that the monitor value of the supply current to the transmission amplifier 106 input from the ADC 103 (# 1) determined in S406 of FIG. 4 or S505 of FIG. 5 or FIG. It is a threshold value which determines whether it did or not. In FIG. 7, in the characteristic 702 corresponding to the prior art, the rush of the FET of the transmission amplifier 106 is caused by the rapid change of the bias voltage value at time t1 when the transmission amplifier 106 is turned on and time t2 when it is turned off. It can be seen that a current is generated. On the other hand, in the characteristic 701 corresponding to the present embodiment, monitoring of the current supplied to the transmission amplifier 106 input from the ADC 103 (# 1) at time t1 when the transmission amplifier 106 is turned on and time t2 when the transmission amplifier 106 is turned off As a result of the control so that the value does not exceed the specified value 703, it can be seen that the occurrence of inrush current is suppressed. Further, in the characteristic 701 corresponding to the present embodiment, the drain voltage (consumption current) is further suppressed in the transmission stage of the non-modulated continuous wave corresponding to the reception time by further changing the bias voltage at the transmission time and the reception time. Is possible.

  The above embodiment assumes that the FET of the transmission amplifier 106 is of n (NPN) type, and has a characteristic that the drain current (current consumption) increases when the bias voltage is increased. Accordingly, assuming that a p (PNP) type is assumed as the FET of the transmission amplifier 106, the direction of changing the bias voltage is reversed, and control may be performed in the direction of decreasing the negative bias voltage.

  In the embodiment described above, the target control voltage for controlling the transmission amplifier 106 is a target bias voltage that is the target value of the bias voltage to be supplied to the transmission amplifier 106, and the CPU 101 operating as a transmission amplifier unit voltage control unit The bias voltage was gradually changed with the target bias voltage as the target value, and was supplied to the bias terminal of the transmission amplifier 106 via the DAC 102 (# 2). On the other hand, the target control voltage may be a target power supply voltage or a target drain voltage instead of the target bias voltage. In this case, the CPU 101 operating as the transmission amplifier unit voltage control unit supplies the power supply voltage or the drain voltage to the power supply or the drain terminal of the transmission amplifier 106 while changing the power supply voltage or the drain voltage gradually with the target power supply voltage or the target drain voltage as the target value. May be

  FIG. 8 is a block diagram of another embodiment of the wireless device 100 'when the target control voltage is the target power supply voltage and the CPU 101 controls the power supply 801. In FIG. 8, portions given the same reference numerals as in the case of the wireless device 100 in FIG. 1 perform the same operations as in the case of FIG. 1.

  In FIG. 1 described above, the CPU 101 supplies the bias voltage to the bias terminal of the transmission amplifier 106 via the DAC 102 (# 2) while gradually changing the bias voltage with the target bias voltage as the target value. On the other hand, in FIG. 8, the CPU 101 may control the power supply voltage VDD in the power supply 801 to be gradually and directly changed with the target power supply voltage as the target value.

  At this time, in place of the target bias voltage table described with reference to FIG. 2 as the target control voltage table in the memory 114, the CPU 101 performs transmission (transmission stage of modulation wave) and reception (for each transmission power required). A target power supply voltage table holding digital values of target power supply voltages corresponding to the respective transmission stages of CW transmission stage) and OFF (transmission and reception OFF transmission stage) may be held. When the power supply 801 drives the transmission amplifier 106 with the power supply voltage corresponding to the target power supply voltage, the target power supply voltage is required for each required transmission power and for each transmission stage at the time of transmission, reception, and off. These parameters are previously determined such that the current consumption of the transmission amplifier 106 is optimal.

  The CPU 101 acquires the digital value of the target power supply voltage corresponding to the transmission power currently set for radio waves and corresponding to the current transmission stage with reference to the target power supply voltage table stored in the memory 114. . Then, the CPU 101 performs control so that the monitor value of the current supplied to the transmission amplifier 106 obtained via the low resistance 112, the differential amplifier 113, and the ADC 103 (# 1) becomes equal to or less than a specified value. Using the digital value of the target power supply voltage as the target value, the digital value of the power supply voltage VDD is calculated while being gradually changed, and is set as the power supply 801.

  As described above, in the present embodiment, it is possible to set the consumption current in the transmission amplifier 106 to the optimal value for each transmission stage while suppressing the occurrence of inrush current in the transmission amplifier 106, thereby achieving wireless transmission It becomes possible to optimize the current consumption of the entire apparatus 100, and in particular, it is possible to extend the operation time of the battery-powered wireless transmission apparatus.

  In the above embodiment, the RFID method has been described as an example, but the same implementation can be made for other non-contact ID methods.

100 wireless transmitter 101 CPU
102 DAC (Digital to Analog Converter)
103 ADC (Analog to Digital Converter)
Reference Signs List 104 transmit baseband processing circuit 105 transmit mixer 106 transmit amplifier 107 circulator 108 antenna 109 receive mixer 110 receive baseband processing circuit 111 local oscillator 112 low resistance 113 differential amplifier 114 memory 801 power supply

Claims (13)

A transmission amplifier unit that amplifies radio waves and transmits them from an antenna;
A current monitor unit that monitors the current consumption of the transmission amplifier unit;
The transmission stage corresponding to the transmission power set for the radio wave while controlling the consumption current monitored by the current monitor unit to be less than or equal to a prescribed value for each of the plurality of transmission stages of the radio wave A transmission amplifier unit voltage control unit that controls the transmission amplifier unit by gradually changing any control voltage in the transmission amplifier unit with a target control voltage for controlling the transmission amplifier unit as a target value;
A wireless transmission device comprising: The target control voltage is a target bias voltage that is a target value of a bias voltage to be supplied to the transmission amplifier unit,
The transmission amplifier unit voltage control unit supplies the target bias voltage as a target value to the bias terminal of the transmission amplifier unit while gradually changing the bias voltage.
The wireless transmission device according to claim 1. The target control voltage is a target power supply voltage that is a target value of the power supply voltage to be supplied to the transmission amplifier unit,
The transmission amplifier unit voltage control unit supplies the target power supply voltage as a target value to the transmission amplifier unit while gradually changing the power supply voltage.
The wireless transmission device according to claim 1. The target control voltage is a target drain voltage that is a target value of the drain voltage to be supplied to the transmission amplifier unit,
The transmission amplifier unit voltage control unit supplies the target drain voltage as a target value to the drain terminal of the transmission amplifier unit while gradually changing the drain voltage.
The wireless transmission device according to claim 1.   The wireless transmission device according to any one of claims 1 to 4, wherein the wireless radio wave is either a modulated wave or a non-modulated continuous wave.   The transmission amplifier unit voltage control unit targets the target control voltage corresponding to the transmission stage of the modulation wave at the time of transition from the transmission stage of transmission / reception off or the transmission stage of the unmodulated continuous wave to the transmission stage of the modulation wave. The value according to claim 5, wherein the control voltage is varied so that the value gradually increases from the voltage value controlled for the transmission / reception off transmission stage or the unmodulated continuous wave transmission stage as a value. Wireless transmitter.   The transmission amplifier unit voltage control unit is configured to set a target control voltage of the transmission stage of the unmodulated continuous wave as a target value at the time of transition from the transmission stage of the modulated wave to the transmission stage of the unmodulated continuous wave. The wireless transmission device according to claim 5, wherein the control voltage is varied so that the value gradually decreases from the voltage value controlled for the transmission stage.   At the time of transition from the transmission stage of the modulated wave or the transmission stage of the non-modulated continuous wave to the transmission stage of transmission / reception off, the transmission amplifier unit voltage control section sets a target control voltage of the transmission stage of transmission / reception off as a target value. The wireless transmission device according to claim 5, wherein the control voltage is varied such that the value gradually decreases from the voltage value controlled for the transmission stage of the modulated wave or the transmission stage of the unmodulated continuous wave. . The wireless transmission device according to any one of claims 5 to 8, wherein the wireless transmission device is an RFID tag reader / writer device that transmits the modulated wave or the unmodulated continuous wave to an RFID tag. The current monitor unit includes a resistor inserted in series with the power supply line supplied to the transmission amplifier unit, a differential amplifier connected to both terminals of the resistor, and a digital signal of the output of the differential amplifier. The wireless transmission device according to any one of claims 5 to 9, further comprising: an analog-to-digital converter for converting into and a processor for determining a digital signal output from the analog-to-digital converter. The transmission amplifier unit voltage control unit is configured for a memory that stores a target control voltage table that holds a digital value of the target control voltage corresponding to each of the transmission stages for each of the transmission powers; The digital value of the target control voltage corresponding to each current transmission stage of the radio wave and the current transmission power of the radio wave is acquired with reference to the target control voltage table, and the consumption current monitored by the current monitor unit becomes less than the specified value. And a processor that calculates the digital value of any of the control voltages in the transmission amplifier unit while gradually changing the digital value of the acquired target control voltage as the target value while performing control, and the digital value calculated by the processor digitally supplied to the transmission amplifier section into an analog value - and a analog converter, any claims 5 to 10 The radio transmitting apparatus according to.   The target control voltage table includes, for each of the transmission powers, a digital value of the target control voltage corresponding to the transmission stage of the modulated wave, and a digital value of the target control voltage corresponding to the transmission stage of the unmodulated continuous wave. The wireless transmission device according to claim 11, wherein digital values of respective target control voltages corresponding to transmission stages of transmission and reception off are held. In a wireless transmission method in a wireless transmission apparatus comprising a transmission amplifier unit for amplifying a wireless radio wave and transmitting it from an antenna,
Monitor the current consumption of the transmission amplifier
The transmission amplifier corresponds to the transmission power set for the radio wave while controlling the consumed current monitored for each of the plurality of transmission stages of the radio wave to be equal to or less than a specified value. Control the transmission amplifier unit by gradually changing any control voltage in the transmission amplifier unit with a target control voltage for controlling the unit as a target value;
A wireless transmission method characterized in that.

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