Transmission device and radio communication device

The present invention particularly relates to a transmission device and a wireless communication device using a polar modulation method.

Conventionally, a class A or class AB linear amplifier has been used for linearly amplifying the envelope fluctuation component in a high-frequency power amplifier that amplifies a modulated signal containing an envelope fluctuation component. While such a linear amplifier is excellent in linearity, it always consumes power associated with a DC bias component, and therefore has lower power efficiency than a class C to class E nonlinear amplifier. Therefore, when such a high-frequency power amplifier is applied to a portable radio device powered by a battery, the power consumption of the high-frequency power amplifier is large, so that the usage time is shortened. Further, when applied to a base station device of a wireless system in which a plurality of high-power transmitters are installed, there is a circumstance that the device becomes large and the amount of heat generated increases.

Therefore, as a highly efficient transmission device, a transmission device using a polar modulation method has been proposed. As shown in FIG. 7, the transmission device using the polar modulation method includes an amplitude phase separation unit 10, an amplitude modulation signal amplifier 11, a frequency synthesizer 12, and a high frequency power amplifier 13 which is a non-linear amplifier.

The amplitude phase separation unit 10 inputs the baseband modulation signal S1 and separates it into the baseband amplitude modulation signal S2 and the baseband phase modulation signal S3. The baseband amplitude-modulated signal S2 is supplied to the non-linear high-frequency power amplifier 13 as the power supply voltage of the high-frequency power amplifier 13 via the amplitude-modulated signal amplifier 11. The baseband phase modulation signal S3 is input to the frequency synthesizer 12. The frequency synthesizer 12 obtains a high-frequency phase-modulated signal S4 by phase-modulating a carrier signal with a baseband phase-modulated signal S3, and sends this to a high-frequency power amplifier 13. As a result, the high frequency power amplifier 13 amplifies the high frequency phase modulation signal S4 with the power supply voltage corresponding to the baseband amplitude modulation signal S2, and outputs this as the transmission output signal S5.

Next, the operation of the transmitter using this polar modulation method will be described. First, assuming that the baseband modulation signal S1 is Si (t), Si (t) can be expressed by the following equation.<maths num="1"><img file="JP2005295533A_D0001.tif" /></maths> Here, a (t) indicates amplitude data, and exp [jφ (t)] indicates phase data.

The amplitude data a (t) and the phase data exp [jφ (t)] are extracted from Si (t) by the amplitude phase separator 10. Here, the amplitude data a (t) corresponds to the baseband amplitude modulation signal S2, and the phase data exp [jφ (t)] corresponds to the baseband phase modulation signal S3. The amplitude data a (t) is amplified by the amplitude modulation signal amplifier 11 and given to the high frequency power amplifier 13. As a result, the power supply voltage value of the high frequency power amplifier 13 is set based on the amplitude data a (t).

The frequency synthesizer 12 generates a high-frequency phase modulation signal S4 in which the carrier angular frequency ωc is modulated by the phase data exp [jφ (t)], and this is input to the high-frequency power amplifier 13. Here, assuming that the high-frequency phase modulation signal S4 is Sc, Sc can be expressed by the following equation.<maths num="2"><img file="JP2005295533A_D0002.tif" /></maths>

Then, by using a non-linear amplifier for the high-frequency power amplifier 13, the signal obtained by multiplying the power supply voltage value a (t) of the high-frequency power amplifier 13 and the output signal of the frequency synthesizer 12 is amplified by the gain G of the high-frequency power amplifier 13. The transmitted output signal S5 is obtained. Here, assuming that the transmission output signal S5 is the RF signal Srf, the RF signal Srf can be expressed by the following equation.<maths num="3"><img file="JP2005295533A_D0003.tif" /></maths>

Since the signal input to the high-frequency power amplifier 13 is a phase-modulated signal having no fluctuation component in the amplitude direction, it becomes a constant envelope signal. Therefore, since an efficient nonlinear amplifier can be used as the high-frequency power amplifier 13, a highly efficient transmitter can be provided. Techniques using this type of polar modulation are described in, for example, Patent Document 1 and Patent Document 2.<patcit num="1"><text>Japanese Patent No. 3207153</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2001-156554</text></patcit>

<p> However, in the conventional transmitter using the polar modulation method, when the output power of the high frequency power amplifier 13 is controlled, the output signal does not change linearly with respect to the input signal because the high frequency power amplifier 13 is a non-linear amplifier. .. Therefore, it is necessary to control the average signal level by the transmission power control signal (hereinafter referred to as the gain control signal) by changing the power supply voltage in the same manner as the instantaneous amplitude control by the baseband amplitude modulation signal. In this case, the control range of the output power is limited by the leakage power, the operating limit of the transistor with respect to the power supply voltage, and the like.</p><p> The present invention has been made in view of the above points, and an object of the present invention is to provide a transmission device and a wireless communication device having good power efficiency and a wide control range of transmission output power.</p>

<p> In order to solve such a problem, in one aspect of the transmitting device of the present invention, it is a transmitting device using a polar modulation method, and an amplitude that separates baseband modulation data into a baseband amplitude-modulated signal and a baseband phase-modulated signal. The phase separation means, the phase modulation means that modulates the high-frequency carrier signal based on the baseband phase-modulated signal to form the high-frequency phase-modulated signal, and the high-frequency phase-modulated signal provided on the subsequent stage side of the phase-modulated means. A variable gain amplification means for amplifying and a high frequency power amplifier provided on the rear side of the variable gain amplification means and amplifying the power of a high frequency phase modulation signal amplified by the variable gain amplification means are provided, and the variable gain is provided. The amplification means is based on the linear-log conversion circuit that linearly converts the baseband amplitude-modulated signal, the linear-log-converted baseband amplitude-modulated signal, and the gain control signal, and the high-frequency phase-modulated signal. A variable gain amplifier that amplifies the signal and a variable gain amplifier.</p><p> According to this configuration, since the variable gain amplification means is provided, the amplification processing of the high frequency power amplifier and the variable gain amplification means is performed as compared with the case where the high frequency power amplifier is in charge of all the amplification processing of the high frequency phase modulation signal. Depending on the combination, amplification processing that takes into account the performance of the high-frequency power amplifier can be performed, and transmission output power with a wide dynamic range can be obtained. That is, by controlling the gain of the variable gain amplification means, it is possible to reduce the leakage power by controlling the level of the high frequency phase modulation signal input to the high frequency power amplifier. As a result, in the high frequency power amplifier, the control range of the output power by the power supply voltage can be expanded.</p><p> In addition, the variable gain amplification means uses a high-frequency phase based on a linear-log conversion circuit that linearly converts the baseband amplitude-modulated signal, a linear-log-converted baseband amplitude-modulated signal, and a gain control signal. Since it is configured to include a variable gain amplifier that amplifies the modulated signal, both the average signal level control by the gain control signal and the instantaneous amplitude control based on the baseband amplitude modulated signal for the high frequency phase modulated signal can be performed by the variable gain amplifier. The configuration on the signal line that amplifies the high-frequency phase-modulated signal can be simplified. For example, with a simple configuration such as providing multiple stages of variable gain amplifiers or sharing the same variable gain amplifier, both control of the average signal level based on the gain control signal and instantaneous amplitude fluctuation based on the baseband amplitude modulated signal. Can be applied to the high-frequency phase-modulated signal.</p><p> In one embodiment of the transmitter of the present invention, the variable gain amplification means further comprises an adder circuit that adds the baseband amplitude modulated signal linearly-log converted by the linear-log conversion circuit and the gain control signal. However, the variable gain amplifier adopts a configuration that amplifies the high-frequency phase-modulated signal based on the signal after addition by the adder circuit.</p><p> According to this configuration, the average signal level control and the instantaneous amplitude control can be performed by the same variable gain amplifier, so that the number of stages of the variable gain amplifier can be reduced by that amount, and the circuit scale can be reduced.</p><p> In one embodiment of the transmitter of the present invention, the high frequency power amplifier is provided with a power supply voltage or a predetermined fixed power supply voltage according to the baseband amplitude modulation signal and the gain control signal according to the first and second operation modes. A power supply voltage supply means for selectively supplying is further provided, and in the first operation mode, the high frequency power amplifier is supplied with a power supply voltage changed according to the baseband amplitude modulation signal and the gain control signal to the high frequency power amplifier. Is operated as a non-linear amplifier, the high-frequency power amplifier performs amplitude modulation according to the baseband amplitude modulation signal and the gain control signal, and in the second operation mode, a fixed power supply voltage is supplied to the high-frequency power amplifier to obtain a high frequency. The power amplifier is operated as a linear amplifier, and the variable gain amplification means is used to perform amplitude modulation according to the baseband amplitude modulation signal and the gain control signal.</p><p> According to this configuration, the power efficiency can be significantly improved by operating the high frequency power amplifier as a non-linear amplifier in the first operation mode (for example, when obtaining a high level transmission output power). In the second operation mode (for example, when obtaining a low level transmission output power), the high frequency power amplifier is operated as a linear amplifier, and the amplitude control by the baseband amplitude modulation signal and the gain control signal by the variable gain amplification means. I do. As a result, while maintaining high power efficiency by the high-frequency power amplifier, the average signal level control by the gain control signal and the instantaneous amplitude control by the baseband amplitude-modulated signal are satisfactorily performed over a wide level for the high-frequency phase-modulated signal. You will be able to apply.</p><p> In one embodiment of the wireless communication device of the present invention, a transmission processing unit having any of the above transmission devices, a reception processing unit that demodulates a received signal, an antenna, and a transmission signal supplied from the transmission processing unit to the antenna. A configuration is adopted in which a transmission / reception switching unit for switching between the antenna and the supply of the received signal from the antenna to the reception processing unit is provided.</p><p> According to this configuration, since the power efficiency of the transmission device is high, the usage time of the on-board battery power supply can be extended, and the high-frequency power amplifier of the transmission device can be made smaller, so that the wireless communication device can be made even smaller. Can be achieved. Further, since the control range of the transmission output power of the transmission device is wide, it is possible to form a higher quality transmission signal according to the communication environment, and the communication quality can be improved.</p>

<p> As described above, according to the present invention, it is possible to realize a transmission device and a wireless communication device having good power efficiency and a wide control range of transmission output power.</p>

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a schematic configuration of a transmission device for explaining an embodiment of the present invention. The transmission device 100 transmits the baseband modulation signal S1 by using the polar modulation method.

The transmission device 100 inputs the baseband modulation signal S1 to the amplitude phase separator 101. The amplitude phase separation unit 101 separates the baseband modulation signal S1 into the baseband amplitude modulation signal S2 and the baseband phase modulation signal S3.

The baseband amplitude modulation signal S2 is input to the multiplier 102. The multiplier 102 multiplies the baseband amplitude modulation signal S2 and the gain control signal S12, and sends the multiplication result to the terminal a of the switch 103. Further, a DC voltage value S11 is given to the terminal b of the switch 103, and the switch 103 is an amplitude modulation signal following the gained baseband amplitude modulation signal S2 or the DC voltage value S11 according to the mode switching signal S10. Output to amplifier 104. The amplitude modulation signal amplifier 104 generates a power supply voltage of the high frequency power amplifier 105 from the signal input from the switch 103, and supplies the power supply voltage to the high frequency power amplifier 105. Here, the amplitude-modulated signal amplifier 104 preferably uses a class D amplifier that expresses amplitude information in pulse width in order to change the power supply voltage with high efficiency according to the level of the baseband amplitude-modulated signal S2.

As a result, in the transmitter 100, the mode of supplying the high-frequency power amplifier 105 with the power supply voltage based on the gain-controlled baseband modulation signal S2 or the fixed power supply voltage based on the DC voltage value S11 is set. It becomes possible to select according to the switching signal S10. That is, it becomes possible to select whether to operate the high frequency power amplifier 105 non-linearly or linearly according to the mode switching signal S10. That is, the switch 103 functions as a power supply voltage supply means for selectively supplying a power supply voltage corresponding to the baseband amplitude modulation signal S2 or a predetermined fixed power supply voltage to the high frequency power amplifier 105.

On the other hand, the baseband phase modulation signal S3 is first input to the frequency synthesizer 106. The frequency synthesizer 106 obtains a high-frequency phase-modulated signal S4 by phase-modulating the carrier frequency with the baseband phase-modulated signal S3, and sends this to the variable gain amplification unit 201.

The variable gain amplification unit 201 includes two variable gain amplifiers 202 and 203, a linear-log conversion unit 206, a digital-to-analog conversion circuit (D / A) 204 and 207, and a low-pass filter (LPF) 205 and 208. Have.

The variable gain amplification unit 201 inputs the baseband amplitude modulation signal S2 output from the switch 111 to the linear-log conversion unit 206. The linear-log converter 206 converts the baseband amplitude modulation signal S2 into a log and outputs it. The method of this linear-log conversion will not be described in detail, but it can be easily realized by a known digital signal processing circuit. The log-converted baseband amplitude modulation signal is input to the variable gain amplifier 203 as a gain control signal of the variable gain amplifier 203 via the digital-analog conversion circuit (D / A) 207 and the low-pass filter (LPF) 208.

Further, the variable gain amplification unit 201 supplies the gain control signal S21 to the variable gain amplifier 202 as a gain control signal of the variable gain amplifier 202 via the digital-analog conversion circuit (D / A) 204 and the low-pass filter (LPF) 205.

The gain control signal S21 is obtained by adding an offset by the gain offset signal S20 to the gain control signal S12 by the adder 110. This gain offset signal S20 is set for the variable gain amplifier 202 so that a signal at a level suitable for operating the high frequency power amplifier 105 as a non-linear amplifier in the saturation operation or switching operation region can be obtained. is there. The variable gain amplifier 202 amplifies the high-frequency phase modulation signal S4 in response to the gain control signal S21, and sends the amplified signal to the variable gain amplifier 203.

Either the baseband amplitude modulation signal S2 or the baseband amplitude modulation signal S2 whose lower limit value is limited by the lower limit value limiting circuit 112 is input to the linear-log converter 206 via the switch 111. The lower limit value limiting circuit 112 limits the lower limit value of the amplitude fluctuation of the baseband amplitude modulation signal S2. As a result, the variable gain amplifier 203 performs amplitude modulation on the output signal of the variable gain amplifier 202 based on either the lower limit limited baseband amplitude modulation signal S2 or the lower limit unlimited baseband amplitude modulation signal S2. And send it to the high frequency power amplifier 105.

The high-frequency power amplifier 105 obtains a transmission output signal S30 by amplifying the high-frequency phase modulation signal output from the variable gain amplification unit 201 using the power supply voltage value supplied from the amplitude modulation signal amplifier 104.

Next, the operation of the transmission device 100 will be described. In FIG. 1, the operating mode of the high-frequency power amplifier 105 is determined according to, for example, the transmission power level designation from the radio base station to the transmission device 100, or the transmission power level based on the state of the received signal of the transmission device 100.

When increasing the level of the transmission output signal S30, an operation mode in which the high-frequency power amplifier 105 is a non-linear amplifier is desirable from the viewpoint of power efficiency. On the other hand, when the level of the transmission output signal S30 becomes low and the high frequency power amplifier 105 is out of the range in which the high frequency power amplifier 105 can operate as a non-linear amplifier, it is desirable to operate the high frequency power amplifier 105 as a linear amplifier.

Focusing on this point, the transmission device 100 prepares a mode switching signal S10, and switches the operation mode of the high-frequency power amplifier 105 between a mode for operating as a non-linear amplifier and a mode for operating as a linear amplifier. The mode switching signal S10 is set based on the desired transmission power level and the characteristics of the high frequency power amplifier 105.

The mode switching signal S10, the DC voltage value S11, the gain control signal S12, and the gain offset signal S20 input to the transmission device 100 are set by, for example, a control unit (not shown).

The connection of switches 103 and 111 in FIG. 1 shows a case where the level of the transmission output signal S30 is relatively high. First, a case where the level of the transmission output signal S30 is relatively high will be described. In this case, the high frequency power amplifier 105 operates as a non-linear amplifier in the saturation operation or switching operation region. In this case, the high frequency power amplifier 105 performs amplitude modulation of the high frequency phase modulation signal. Specifically, when the terminal a and the terminal c of the switch 103 are connected by the mode switching signal S10, the product value of the baseband amplitude modulation signal S2 and the gain control signal S12 output from the terminal c of the switch 103 is calculated. After being amplified by the amplitude modulation signal amplifier 104, it is applied to the high frequency power amplifier 105 as the power supply voltage of the high frequency power amplifier 105. As a result, the high frequency power amplifier 105 operates for amplitude modulation.

On the other hand, for the high-frequency phase modulation signal S4, when the level of the transmission output signal S30 is relatively large, the mode switching signal S10 connects the terminal a and the terminal c of the switch 111. As a result, a signal whose lower limit value of the amplitude fluctuation of the baseband amplitude modulation signal S2 is limited by the lower limit value limiting circuit 112 is input to the linear-log conversion unit 206 of the variable gain amplification unit 201 via the switch 111. As a result, the output signal of the variable gain amplifier 202 is amplitude-modulated by the variable gain amplifier 203 based on the baseband amplitude modulation signal S2 whose lower limit is limited, and is sent to the high-frequency power amplifier 105.

Here, in general, a variable gain amplifier has a voltage gain V between input and output._{out out}/ V_INIs the exponential function of the gain control signal. In consideration of this, in this embodiment, the variable gain amplifier 203 is provided by log-converting the baseband amplitude modulation signal S2 by the linear-log converter 206 and then supplying it as the gain control signal of the variable gain amplifier 203. It is designed to operate linearly with respect to the baseband amplitude modulated signal S2. In other words, by providing the linear-log converter 206, it becomes possible to realize the multiplication of the high frequency phase modulation signal S4 and the baseband amplitude modulation signal S2 by using the variable gain amplifier 203.

In this way, by using the variable gain amplifier 203 to perform multiplication with the baseband amplitude modulation signal S2 as the gain, the average signal level control by the gain control signal S12 and the instantaneous amplitude control by the baseband amplitude modulation signal S2 can be performed. Can be performed using a variable gain amplifier having a similar configuration. This facilitates the manufacture of amplifiers.

Further, the variable gain amplification unit of the present invention does not actually have a configuration in which it is simply divided into two blocks as shown in FIG. 1, but for example, two variable gain amplifiers of three subordinate connections are connected. Will be used as the variable gain amplifier 202 for controlling the average signal level, and the remaining one will be used as the variable gain amplifier 203 for performing instantaneous amplitude control. In this case, if the average signal level and the instantaneous amplitude can be controlled by the same variable gain amplifier as in the present embodiment, the number of variable gain amplifiers assigned to each control can be easily assigned according to the specifications. Can be changed to. As a result, versatility is increased and usability is also improved.

Figure 2 shows a configuration example of the variable gain amplifier. In the figure, Vin is the differential input signal, Vout is the differential output signal, and V._dIndicates the (differential) gain control signal, and Vcc indicates the power supply voltage. R_EIs the emitter resistance, R_LIs the load resistance. Transistors TR5 and TR6 connected to the input terminal to which the differential input signal Vin is input are grounded at the emitter, and the differential current Gm · Vin flows through the collector. Here, Gm can be expressed by the following equation.<maths num="4"><img file="JP2005295533A_D0004.tif" /></maths>

Further gain control signal V_dThis current is V by the transistors Tr1, Tr2, Tr3, Tr4 connected to the input terminal to which is input._dDivided according to, load resistance R_LA voltage drop occurs at. As a result, the input / output relationship can be expressed as the following equation.<maths num="5"><img file="JP2005295533A_D0005.tif" /></maths>

V_dWhen = -, load resistance R_LThose who are not connected (I_x0Since all the current flows through), the following equation is obtained.<maths num="6"><img file="JP2005295533A_D0006.tif" /></maths>

On the contrary, V_dWhen = + , load resistance R_LThose who are connected (I_L0Since all the current flows through), the following equation is obtained.<maths num="7"><img file="JP2005295533A_D0007.tif" /></maths>

Also, V_d/ V_T&lt;&lt; -1 (when the input is small enough) can be approximated as follows.<maths num="8"><img file="JP2005295533A_D0008.tif" /></maths>

That is, the voltage gain Vout / Vin (= proportional to the output amplitude) between the input and output is the gain control signal (or amplitude control signal) V._dIt is an exponential function of (= log linear).

In the present embodiment, after log conversion is performed by the linear-log conversion unit 206, the exponent is multiplied by the variable gain amplifier 203, resulting in linearity. If the linear-log conversion performed by the linear-log conversion unit 206 is made an inverse function of Eq. (5), accurate linear amplification can be performed by the variable gain amplifier 203. If the input is sufficiently small, there is no problem in practical use if the linear-log conversion performed by the linear-log conversion unit 206 is an inverse function of the approximate expression of Eq. (8).

Incidentally, the inverse function of Eq. (5) is expressed by the following Eq.<maths num="9"><img file="JP2005295533A_D0009.tif" /></maths> Here, A represents an amplitude signal.

The inverse function of Eq. (8) is expressed by the following equation.<maths num="10"><img file="JP2005295533A_D0010.tif" /></maths>

As described above, according to the present embodiment, the linear-log converter 206 and the variable gain amplifier 203 are provided, the baseband amplitude modulation signal S2 is log-converted, and the log-converted signal is gain-controlled by the variable gain amplifier 203. By using the signal, the variable gain amplifier 203 can give an instantaneous amplitude fluctuation due to the base band amplitude modulation signal S2. As a result, the variable gain amplifier can perform both the control of the average signal level by the gain control signal S12 and the instantaneous amplitude fluctuation by the baseband amplitude modulation signal S2 for the high frequency phase modulation signal S4, so that the high frequency phase modulation can be performed. The configuration on the signal line that amplifies the signal S4 can be simplified, the versatility can be increased, and the usability can be improved.

In addition, since the linear-log converted value is digital-to-analog converted and given to the variable gain amplifier 203, the number of bits required for the D / A 207 is reduced compared to the case of digital-to-analog conversion of the antilogarithm. As a result, the configuration of the D / A207 can be simplified and the processing time can be shortened.

Further, in the present embodiment, the variable gain amplification unit 201 is provided on the front stage side of the high frequency power amplifier 105, and in the first operation mode, the high frequency power amplifier 105 receives the base band amplitude modulation signal S2 and the gain control signal S12. By supplying the power supply voltage changed accordingly and operating the high-frequency power amplifier 105 as a non-linear amplifier, the high-frequency power amplifier 105 performs amplitude modulation according to the baseband amplitude modulation signal S2 and the gain control signal S12. In the operation mode of 2, a fixed power supply voltage is supplied to the high-frequency power amplifier 105 to operate the high-frequency power amplifier 105 as a linear amplifier, and the variable gain amplification unit 201 responds to the baseband amplitude modulation signal S2 and the gain control signal S12. By performing amplitude modulation, while maintaining high power efficiency by the high-frequency power amplifier 105, the average signal level control and baseband amplitude by the gain control signal S12 over a wide range with respect to the high-frequency phase-modulated signal S4. Instantaneous amplitude control by the modulated signal S2 can be performed satisfactorily.

This will be described in detail below.

FIG. 3 is a diagram showing the circuit configuration of the high-frequency power amplifier 105 when used as a nonlinear amplifier, and FIG. 4 is a diagram showing the operation of the high-frequency power amplifier 105 when used as a nonlinear amplifier. As shown in FIG. 3, the high frequency power amplifier 105 can be represented by a nonlinear amplifier 120 and a parasitic capacitance 121 connected between its input side and output side.

FIG. 4 shows the relationship between the power supply voltage and the output power of the nonlinear amplifier 120. As shown in FIG. 4, in the nonlinear amplifier 120, the square of the power supply voltage is proportional to the output power. Here, the magnitude of the leak power is determined by the parasitic capacitance 121 and the level of the input signal of the nonlinear amplifier 120 (the level of the output signal of the variable gain amplification unit 201).

Here, considering the case where the variable gain amplification unit 201 is not provided, the output of the frequency synthesizer 106 is substantially constant, so the leakage power is also constant. In that case, in order to lower the level of the transmission output signal S30, the power supply voltage of the nonlinear amplifier 120 may be lowered, but the output level cannot be lowered below a certain value due to the leakage power.

On the other hand, in the present embodiment, the leak power is reduced by controlling the gain of the variable gain amplifier 202 by the gain control signal S12 to control the level of the high frequency phase modulation signal input to the high frequency power amplifier 105. It is possible to reduce it. Therefore, in the high frequency power amplifier 105, the control range of the output power by the power supply voltage can be expanded.

Further, the variable gain amplifier 203 performs amplitude modulation on the output signal of the variable gain amplifier 202 based on the baseband amplitude modulation signal S2, so that the input level of the high frequency power amplifier 105 is set to the baseband amplitude modulation signal S2. Since the leakage power is reduced while following the instantaneous level fluctuation of the above, the reproducibility of the instantaneous level fluctuation can be improved. That is, the input of the high frequency power amplifier 105 can be controlled according to the instantaneous output power.

Here, if the input level of the high-frequency power amplifier 105 is lowered too much, it goes out of the saturation operation or switching operation region, and the linearity with respect to the change of the power supply voltage deteriorates. Therefore, in this embodiment, the input level of the high-frequency power amplifier 105 is maintained above a certain value by providing the lower limit value limiting circuit 112.

Next, a case where the level of the transmission output signal S30 is relatively small will be described. First, in the switch 103, the terminal b and the terminal c are connected by the mode switching signal S10. As a result, the DC voltage value S11 is input to the amplitude-modulated signal amplifier 104 via the switch 103, and a constant power supply voltage is applied to the high-frequency power amplifier 105 from the amplitude-modulated signal amplifier 104. As a result, the high-frequency power amplifier 105 operates as a linear amplifier having a linear input / output relationship.

On the other hand, for the high-frequency phase modulation signal S4, when the level of the transmission output signal S30 is relatively small, the mode switching signal S10 connects the terminal b and the terminal c of the switch 111, and the lower limit value is not limited. The signal S2 is input to the linear-log converter 206, and based on this baseband amplitude modulation signal S2, the output signal of the variable gain amplifier 202 is amplitude-modulated by the variable gain amplifier 203 and sent to the high-frequency power amplifier 105. Will be done.

When the level of the transmission output signal S30 is relatively small, the gain offset signal S20 is set to zero, and the unoffset gain control signal S21 is input to the variable gain amplifier 202. The high frequency power amplifier 105 linearly amplifies the output of the variable gain amplifier 203 based on the fixed power supply voltage supplied from the amplitude modulation signal amplifier 104 to obtain the transmission output signal S30.

As described above, in the transmission device 100 of the present embodiment, when the level of the transmission output signal S30 is small and the high frequency power amplifier 105 may deviate from the saturation operation or switching operation region, that is, with respect to a change in the power supply voltage. Even when the linearity of the output power may deteriorate, by operating the high frequency power amplifier 105 as a linear amplifier, the output power control range can be expanded while maintaining the linearity of the output signal with respect to the input signal. ..

That is, when the level of the transmission output signal S30 is relatively high, the high-frequency power amplifier 105 is used as a nonlinear amplifier, and the power supply voltage applied to the high-frequency power amplifier 105 is used for instantaneous amplitude control and gain control based on the baseband amplitude modulation signal S2. When the average output level is controlled based on the signal S12 and the level of the transmission output signal S30 is relatively small, the high frequency power amplifier 105 is used as a linear amplifier, and the variable gain amplification unit 201 provided in front of the high frequency power amplifier 105 is used. By performing instantaneous amplitude control and average output level control in, the level of the transmission output signal S30 can be controlled over a wide range.

Further, when the high-frequency power amplifier 105 operates in a non-linear operation, the leak power in the high-frequency power amplifier 105 is changed by controlling the gain of the variable gain amplifier 202 according to the gain control signal S12 to change the level of the high-frequency phase modulation signal S4. Therefore, the control range of the output power by the power supply voltage can be expanded.

(Embodiment 2) In the first embodiment described above, the case where only the instantaneous amplitude fluctuation by the base band amplitude modulation signal S2 is given by the variable gain amplifier 203 has been described, but in the present embodiment, the variable gain amplifier 203 is used. In addition to the instantaneous amplitude fluctuation by the base band amplitude modulation signal S2, the average signal level is controlled.

A configuration example for achieving this is shown in FIG. In FIG. 5, which is shown by assigning the same reference numerals to the portions corresponding to those in FIG. 1, the variable gain amplification unit 210 adds the baseband amplitude modulation signal and the gain control signal 2 after log conversion by the adder 211. As a result, the variable gain amplifier 203 can give an instantaneous amplitude fluctuation due to the baseband amplitude modulation signal S2 and an average signal level fluctuation due to the gain control signal 2. In this way, since the average signal level control can be assigned to the variable gain amplifier 202 and the variable gain amplifier 203, the number of stages of the variable gain amplifier 202 can be reduced, and the circuit scale can be reduced. Further, even when the performance of each variable gain amplifier is limited with respect to the gain control signal, it becomes possible to perform amplification processing having a sufficiently wide dynamic range according to the gain control signal.

Further, in FIG. 5, the variable gain amplifier 202 also controls the average signal level according to the gain control signal 1, but in some cases, the variable gain amplifier 203 alone may perform instantaneous amplitude control and average signal level control. Since it becomes possible, the circuit scale can be further reduced.

Further, in the first embodiment and the present embodiment, the case where the linear-log conversion is performed before the digital-to-analog conversion by the D / A 207 has been described, but the linear-log conversion is performed after the digital-analog conversion. May be good.

(Embodiment 3) FIG. 6 shows a configuration of a wireless communication device to which the transmission devices of the above-described first and second embodiments are applied. The wireless communication device 300 includes a transmission processing unit 301 including the transmission devices of the first and second embodiments, a reception processing unit 302 that performs reception processing including demodulation processing on the received signal, an antenna 304, and a transmission processing unit. It has a transmission / reception switching unit 303 that switches between a state of supplying a transmission signal from the 301 to the antenna 304 and a state of supplying a reception signal from the antenna 304 to the reception processing unit 302.

The wireless communication device 300 is, for example, a mobile phone, a portable wireless terminal device such as a personal digital assistant having a communication function, a wireless base station, or the like.

In the wireless communication device 300, by applying the transmission device 100 shown in the first and second embodiments to the transmission processing unit 301, in the case of a portable wireless terminal device, the high frequency power amplifier 105 is a non-linear amplifier when the output power is high. By operating as, the power efficiency is improved, the consumption of the battery can be prevented by that amount, and the usage time can be extended. Further, since the high-frequency power amplifier 105 can be miniaturized due to the improved power efficiency and the amount of heat generated can be reduced, the portable wireless terminal device equipped with the high-frequency power amplifier 105 can be miniaturized.

Further, when the wireless communication device 300 is a base station device of a wireless system in which a plurality of high-power transmitters are installed, the power efficiency of the high-frequency power amplifier 105 at high output power is improved. Therefore, the high-frequency power amplifier 105 The size of the equipment can be reduced and the amount of heat generated can be reduced. As a result, the size of the equipment can be prevented and the space can be improved.

The present invention is not limited to the above-described embodiment, and can be implemented by various other embodiments in terms of specific configuration, function, action, and effect without departing from the gist thereof.

The transmission device and wireless communication device of the present invention can realize a transmission device having good power efficiency and a wide control range of transmission output power, and are applied to wireless communication devices such as personal digital assistants and wireless base stations. Is suitable.

<figref num="1">A block diagram showing a schematic configuration of a transmitter according to a first embodiment of the present invention.</figref><figref num="2">Connection diagram showing a configuration example of a variable gain amplifier</figref><figref num="3">The figure which shows the circuit structure when the high frequency power amplifier shown in FIG. 1 is used as a nonlinear amplifier.</figref><figref num="4">The figure explaining the operation when the high frequency power amplifier shown in FIG. 1 is used as a nonlinear amplifier.</figref><figref num="5">The block diagram which shows the structure of the variable gain amplification part of Embodiment 2.</figref><figref num="6">A block diagram showing a configuration of a wireless communication device equipped with the transmission device of the present invention.</figref><figref num="7">Block diagram showing a configuration example of a conventional transmitter</figref>

Code description

100 Transmitter 101 Oscillation phase separator 102 Multiplier 103, 111 Switch 105 High frequency power amplifier 112 Lower limit value limit circuit 201 Variable gain amplifier 202, 203 Variable gain amplifier 206 Linear-log converter S1 Baseband modulation signal S2 Baseband amplitude Modulation signal S3 Baseband phase modulation signal S4 High frequency phase modulation signal S10 Mode switching signal S11 DC voltage value S12 Gain control signal S30 Transmission output signal