JP6720647B2 - Power amplifier and control method thereof - Google Patents

Description

The present invention relates to an envelope tracking power amplifier and a control method thereof.

When amplifying a signal having a large peak-to-average power ratio (PAPR) such as OFDM used in a mobile communication system, a power amplifier device has a back-up having a peak-to-average power ratio (PAPR) or more. It is necessary to have OFF (the decibel difference between the maximum output amplitude level and the output saturation power level), and as a result, the power added efficiency (PAE) is the high frequency signal power generated by the high frequency amplifier and the high frequency amplifier. The higher the power added efficiency, the lower the power consumption).

In order to improve the power efficiency of this power amplification device, there is an envelope tracking method. This is a technique in which the power supply voltage of the high-frequency amplifier is changed according to the amplitude of the envelope signal of the transmission signal, so that the high-frequency amplifier is always operated in a state close to saturation and high-efficiency operation is realized.
The power gain of an amplification element such as an FET or a transistor used in this high frequency amplifier changes with temperature. Therefore, when used near the output saturation power in order to increase the power added efficiency, if the power gain increases due to temperature, the power supply voltage supplied to the high frequency amplifier will be insufficient and distortion will occur, generating harmonics, On the contrary, when the power gain decreases, the transmission output decreases and the transmission power becomes insufficient. Therefore, it is known that the envelope signal is corrected for the power supply voltage in consideration of this temperature condition (for example, refer to Patent Document 1).

JP, 2011-250166, A

However, in this prior art, since the timing when correcting the envelope signal based on the temperature condition is not considered, the amplitude of the envelope signal becomes discontinuous, and the waveform of the output transmission signal output from the high frequency amplifier is also When the envelope signal is corrected, it is a problem to prevent the amplitude of the envelope signal from becoming discontinuous because it may become discontinuous and generate distortion or the like.

Therefore, the present invention has been made in view of the above problems of the prior art, and when correcting the envelope signal based on the temperature condition, it is possible to correct the envelope signal while maintaining the continuity of the amplitude of the envelope signal. An object of the present invention is to provide a power amplification device and a control method thereof that can be performed.

A power amplification device according to one aspect of the present invention is a power amplification device of an envelope tracking system, which includes an envelope signal generation unit that generates an envelope signal from a baseband input transmission signal, and a control power supply voltage that amplifies the envelope signal. An envelope signal processing unit that generates a transmission signal processing unit that generates an output transmission signal by amplifying an input transmission signal using a control power supply voltage as a power supply voltage, and a temperature detection unit that detects the temperature of the transmission signal processing unit. a level detecting section for detecting the level of the envelope signal generated by the envelope signal generating unit, and a envelope correction processing section for outputting a correction envelope signal to input the envelope signal, the envelope correction processing unit, It is possible to generate and output a plurality of correction envelope signals having different input/output characteristics according to the detected temperature detected by the temperature detecting unit, and when the detected temperature detected by the temperature detecting unit changes, the detection The correction envelope signal is switched to the corrected envelope signal according to the detected temperature after the change when the level becomes equal to or lower than a predetermined threshold value .

According to one aspect of the present invention, the timing of switching to the corrected envelope signal based on the temperature condition of the transmission signal processing unit is performed when the detection level is equal to or lower than a predetermined threshold while detecting the level of the envelope signal. The amplitude continuity can be maintained and corrected.

It is a block diagram showing an example of composition of a power amplification device concerning a 1st embodiment of the present invention. It is a figure which shows an example of a look-up table, (a) is a low temperature look-up table, (b) is a normal temperature look-up table, (c) is a high temperature look-up table. It is a flow chart which shows an example of a transmission processing procedure of a power amplification device. It is a characteristic diagram which shows the relationship of the output power and efficiency with respect to the input power of a power amplification device. It is a wave form diagram which shows the correction|amendment envelope signal at the time of switching a look-up table in an envelope correction process. It is explanatory drawing in the case of performing a uniform interpolation of a lookup table. It is explanatory drawing at the time of interpolating with a high density the high temperature side of a lookup table.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar reference numerals are given to the same or similar parts. However, it should be noted that the drawings are schematic and different from the actual ones. Therefore, specific components should be determined in consideration of the following description.
Further, the embodiments described below exemplify devices and methods for embodying the technical idea of the present invention. Not specific to: Various changes can be added to the technical idea of the present invention within the technical scope defined by the claims described in the claims.

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of one embodiment of the invention. However, it will be apparent that one or more embodiments may be practiced without such specific details. In addition, well-known structures and devices are schematically shown in order to simplify the drawing.
Hereinafter, a power amplification device according to an embodiment of the present invention will be described.
As illustrated in FIG. 1, the power amplification device 10 includes a transmission signal generation unit 1, an envelope signal generation unit 2, an envelope correction processing unit 3, an envelope signal processing unit 4, a transmission signal processing unit 5, and a temperature detection unit. The unit 6 and the level detection unit 7 are provided.

The transmission signal generation unit 1 generates an input transmission signal SIT which is a baseband digital signal, and outputs the generated input transmission signal SIT to the envelope signal generation unit 2 and the transmission signal processing unit 5. The transmission signal generation unit 1 may be provided outside the power amplification device 10. That is, the input transmission signal may be an input signal from the outside of the power amplification device 10. In this case, the power amplification device 10 may have an input section for connecting to the external transmission signal generation section 1.

The envelope signal generator 2 generates an envelope signal SIE based on the input transmission signal SIT from the transmission signal generator 1.
The temperature detection unit 6 is arranged in the vicinity of a high frequency amplifier 5b included in a transmission signal processing unit 5 described later, detects the temperature of the high frequency amplifier 5b, and outputs a temperature detection signal St to the envelope correction processing unit 3.

The level detection unit 7 detects the signal level of the envelope signal SIE output from the envelope signal generation unit 2 and outputs the level detection signal SL indicating the detected signal level to the envelope correction processing unit 3.
The input/output characteristics of the high frequency amplifier 5b change depending on the temperature of the high frequency amplifier 5b. Therefore, the envelope correction processing unit 3 corrects the envelope signal according to the temperature detected by the temperature detection unit 6 and outputs the corrected envelope signal SAE. The envelope correction processing unit 3 is connected to a storage unit 8 that stores a plurality of lookup tables for correcting the envelope signal according to the temperature of the high frequency amplifier 5b.

As shown in FIG. 1, the specific configuration of the envelope correction processing unit 3 includes a correction envelope signal generation unit 3a and a correction operation control unit 3b that controls the correction operation of the correction envelope signal generation unit 3a.
The corrected envelope signal generation unit 3a is input from the envelope signal generation unit 2 with reference to the lookup table stored in the storage unit 8 based on the temperature detected by the correction operation control unit 3b by the temperature detection unit 6. A corrected envelope signal SAE is generated based on the envelope signal SIE.

Here, the look-up table stored in the storage unit 8 is, for example, for low temperature (at the start of transmission or when the environment temperature to be used is set for each temperature region of the high-frequency amplifier 5b as shown in FIGS. 2A to 2C). Three types are prepared: a low temperature lookup table LT1, a normal temperature (during normal operation) lookup table LT2, and a high temperature (transmission time is long or when the environment temperature is high) lookup table LT3. There is.

The low-temperature lookup table LT1 is applied when the temperature of the high-frequency amplifier 5b belongs to a low-temperature region in the range of, for example, −10° C. (operation guarantee temperature on the low temperature side) or higher and lower than 20° C. The normal temperature lookup table LT2 is applied when the temperature of the high-frequency amplifier 5b belongs to a normal temperature range of 20° C. or higher and lower than 60° C. in a normal time. The high-temperature lookup table LT3 is applied when the temperature of the high-frequency amplifier 5b belongs to a high-temperature region in the range of, for example, 60° C. or higher and less than 90° C. (operation guarantee temperature of the elements of the high-frequency amplifier).
The look-up tables shown in FIGS. 2A to 2C correspond to the characteristics that the power gain increases when the temperature of the high-frequency amplifier 5b is lower than the room temperature (during normal operation) and decreases when the temperature is high. There is.

The low temperature lookup table LT1 is a table for compensating for the characteristic that the temperature of the high frequency amplifier 5b is lower than that in the normal operation and the power gain of the high frequency amplifier 5b is higher, and is set by the characteristic line L1 of FIG. 2A. The horizontal axis represents the level LV1 of the envelope signal SIE, and the vertical axis represents the level LV2 of the corrected envelope signal SAE. In the characteristic line L1, the level LV2 of the corrected envelope signal SAE also becomes zero when the level LV1 of the envelope signal SIE is zero. When the level LV1 of the envelope signal SIE increases from this state, the correction envelope signal SAE also increases in proportion to the increase amount of the level LV1 of the envelope signal SIE up to a preset threshold value LV1th. However, when the level LV1 of the envelope signal SIE exceeds the threshold LV1th, the inclination is set to be small so that the increase amount of the level LV2 of the corrected envelope signal SAE becomes smaller than the increase amount of the level LV1 of the envelope signal SIE.

The normal temperature lookup table LT2 is a table corresponding to the standard characteristic of the power gain because it is used in the normal operation, and is set by the characteristic line L2 of FIG. 2B, and is the level LV1 of the envelope signal SIE. The increase amount of the level LV2 of the correction envelope signal SAE is set to increase in proportion to the increase amount of

The high temperature lookup table LT3 is a table for compensating for the characteristic that the temperature of the high frequency amplifier 5b is higher and the power gain of the high frequency amplifier 5b is lower than in the normal operation, and is set by the characteristic line L3 of FIG. 2C. While the level LV1 of the envelope signal SIE reaches the threshold value LV1th from zero, the increase amount of the level LV2 of the correction envelope signal SAE increases according to the increase amount of the level LV1 of the envelope signal SIE, When the level LV1 of the signal SIE exceeds the threshold value LV1th, the slope is set to be larger than that of the characteristic line L2 so that the increase amount of the level LV2 of the corrected envelope signal SAE is larger than the increase amount of the level LV1 of the envelope signal SIE. ing.

The characteristic lines L1 to L3 of the look-up tables LT1 to LT3 are set to be linear for the sake of simplicity of description, but in reality, the characteristic lines L1 to L3 may be non-linear in order to match the temperature characteristic of the high frequency amplifier 5b. is there.
The correction operation control unit 3b controls the correction operation of the correction envelope signal generation unit 3a, and receives the temperature detection signal St detected by the temperature detection unit 6 and the level LV1 of the envelope signal SIE detected by the level detection unit 7. It The correction operation control unit 3b determines whether the temperature detection signal St belongs to the low temperature region, the normal temperature region, or the high temperature region, and selects the lookup table referred to by the correction envelope signal generation unit 3a. Then, when the selected lookup table is different from the current lookup table, the correction operation control unit 3b switches to the selected lookup table when the level LV1 of the envelope signal SIE is equal to or less than the threshold LV1th. To do.

The envelope signal processing unit 4 amplifies the corrected envelope signal from the envelope correction processing unit 3 to generate a control power supply voltage VCP, and outputs the control power supply voltage VCP to the transmission signal processing unit 5.
Here, as an example, the envelope signal processing unit 4 includes a D/A converter (hereinafter referred to as a DAC) 4a, an amplifier 4b, and a DC power supply 4c.

The DAC 4a converts the corrected envelope signal SAE from the envelope correction processing unit 3 from a digital signal to an analog signal and outputs the analog signal to the amplifier 4b in the subsequent stage.
The amplifier 4b operates by receiving the DC voltage supplied from the DC power supply 4c, amplifies the analog signal of the correction envelope signal SAE from the DAC 4a to generate the control power supply voltage VCP, and processes the control power supply voltage VCP for transmission signal processing. Output to the unit 5.

The DC power source 4c is a DC power source such as a battery. The DC power source 4c may be provided outside the power amplification device 10. In this case, the power amplification device 10 only needs to have a power supply input section for connecting to the external DC power supply 4c.
The transmission signal processing unit 5 converts the transmission signal SIT from the transmission signal generation unit 1 from a digital signal into an analog signal, and uses the high frequency amplifier 5b to which the control power supply voltage VCP from the envelope signal processing unit 4 is applied to the analog signal. The output transmission signal is amplified and generated, and the output transmission signal is output to the antenna 9.

Here, as an example, the transmission signal processing unit 5 includes a DAC/RF converter 5a and a high frequency amplifier 5b.
The DAC/RF converter 5a converts the transmission signal SIT from the transmission signal generation unit 1 from a digital signal to an analog signal, and then up-converts it into a high frequency signal in an RF (Radio Frequency) band to generate an RF signal SRF, and a high frequency signal in the subsequent stage. Output to the amplifier 5b.

The high frequency amplifier 5b is configured to include, for example, an N-channel field effect transistor (FET), and applies the control power supply voltage VCP output from the envelope signal processing unit 4 to the drain electrode. This control power supply voltage VCP is based on the corrected envelope signal SAE corrected according to the temperature-dependent input/output characteristic of the high-frequency amplifier 5b in the envelope correction processing unit 3, and therefore the output power characteristic L11 with respect to the input power of the power amplifier of FIG. As indicated by the power efficiency characteristic L21, the high-frequency amplifier 5b operates near the saturation power point to amplify the RF signal SRF with high efficiency to generate the output transmission signal SOT. Then, the high frequency amplifier 5b outputs the output transmission signal SOT to the antenna 9.

The antenna 9 is a device that transmits the output transmission signal SOT from the transmission signal processing unit 5 to the outside of the power amplification device 10 by radiating the output transmission signal SOT as a radio wave (electromagnetic wave) into space. The antenna 9 may be provided inside the power amplification device 10.
Next, the flow of transmission processing by the power amplification device 10 will be described with reference to FIG.
When the transmission start instruction (transmission ON) is input, first, the transmission process of FIG. 3 is started, and the correction operation control unit 3b of the envelope correction processing unit 3 acquires the temperature detection signal St detected by the temperature detection unit 6. (Step S1).

The correction operation control unit 3b determines whether the temperature of the high-frequency amplifier 5b belongs to the low temperature region, the normal temperature region, or the high temperature region based on the temperature detection signal St, and stores it in the storage unit 8 based on the determination result. One of the low temperature look-up table LT1, the room temperature look-up table LT2, and the high temperature look-up table LT3 is selected, and the correction envelope signal generation unit 3a generates the correction envelope signal based on the selected look-up table. It is generated (step S2).

Next, the transmission signal generation unit 1, the envelope signal generation unit 2, the envelope correction processing unit 3, the envelope signal processing unit 4, and the transmission signal processing unit 5 are operated to start the transmission process (step S3).
Therefore, the transmission signal generation unit 1 generates the baseband input transmission signal SIT and outputs the generated input transmission signal SIT to the envelope signal generation unit 2 and the transmission signal processing unit 5.

The envelope signal generator 2 generates an envelope signal SIE based on the input transmission signal SIT and outputs it to the envelope correction processor 3.
The envelope correction processing unit 3 refers to the lookup table LTi (i=1, 2, 3) selected by the correction operation control unit 3b according to the temperature detected by the temperature detection unit 6, and refers to the envelope signal generation unit 2 A corrected envelope signal SAE is generated based on the signal of the envelope signal SIE input from the and output to the envelope signal processing unit 4.
The envelope correction processing unit 3 corrects the envelope signal according to the temperature detected by the temperature detection unit 6 and outputs a corrected envelope signal SAE. The envelope correction processing unit 3 is connected to a storage unit 8 that stores a plurality of lookup tables for correcting the level of the envelope signal according to the temperature of the high frequency amplifier 5b.

The envelope signal processing unit 4 generates the control power supply voltage VCP based on the corrected envelope signal SAE from the envelope correction processing unit 3 and outputs it to the transmission signal processing unit 5.
The transmission signal processing unit 5 generates the RF signal SRF after converting the transmission signal SIT from the transmission signal generation unit 1 from a digital signal to an analog signal, and the RF signal SRF is converted by the control power supply voltage VCP from the envelope signal processing unit 4. The applied high-frequency amplifier 5b amplifies the output transmission signal SOT and outputs the output transmission signal to the antenna 9.

As described above, after the transmission process is started, the process proceeds to step S4, and it is determined whether or not a time measuring timer (not shown) built in the correction operation control unit 3b that measures a predetermined time (for example, one minute) has timed out. If it is determined that the time counting timer has not timed out, the process waits until the time is up.
In step S5, the correction operation control unit 3b obtains the temperature detection signal St from the temperature detection unit 6 again, and then it is determined whether or not the temperature detection signal St is within the temperature range of the currently selected lookup table LTi. Is determined (step S6).

If this determination result is within the temperature range of the currently selected lookup table LTi, the process returns to step S4. If it is different from the currently selected temperature range of the lookup table LTi, the temperature detection signal St is output. A lookup table LTj (a value excluding i out of j=1, 2, 3) of the temperature range to which it belongs is selected (step S7).
Next, the level LV1 of the envelope signal SIE from the level detection unit 7 is acquired (step S8), and it is determined whether or not the level LV1 of the acquired envelope signal SIE is equal to or less than the threshold value LV1th (step S9).

If the result of this determination is that the level LV1 of the envelope signal SIE exceeds the threshold value LV1th, the process returns to step S8, and if the level LV1 is less than or equal to the threshold value LV1th, the lookup table LTj that newly selects the lookup table LTi. (Step S10).
Next, it is determined whether or not a transmission stop instruction (transmission off) has been input (step S11). When the transmission stop instruction has been input, transmission processing stop processing is performed (step S12), and the transmission signal generation unit 1, The processing is terminated after stopping the envelope signal generation unit 2, the envelope correction processing unit 3, the envelope signal processing unit 4, and the transmission signal processing unit 5.

On the other hand, when the transmission stop instruction is not input, the process returns to step S4.
In this way, the envelope signal SIE from the envelope signal generation unit 2 is output to the envelope correction processing unit 3, and in the envelope correction processing unit 3, the temperature detection signal St of the high frequency amplifier 5b input from the temperature detection unit 6 is input. A temperature-compensated corrected envelope signal SAE is generated according to Based on the corrected envelope signal SAE output from the envelope correction processing unit 3, the envelope signal processing unit 4 generates the control power supply voltage VCP, and outputs the generated control power supply voltage VCP to the transmission signal processing unit 5.

In this way, by correcting the envelope signal according to the temperature detection signal St of the high frequency amplifier 5b and controlling the control power supply voltage VCP, it is possible to compensate for the characteristic that the power gain increases at low temperatures to compensate for the harmonics caused by the distortion. Since the occurrence of output power shortage can be suppressed by suppressing the generation or compensating for the characteristic that the power gain decreases at high temperature, the backoff can be made smaller than when the envelope signal is not corrected. Can be raised.

The lookup table LTi used by the correction envelope signal generator 3a by the correction operation controller 3b of the envelope correction processor 3 is switched when the level LV1 of the envelope signal SIE is equal to or lower than the threshold LV1th. Therefore, at a level equal to or lower than the threshold value LV1th of each look-up table LT1 to LT3, the level LV2 of the correction envelope signal SAE becomes the same value regardless of which look-up table LT1 to LT3 is selected. Therefore, as shown in FIG. 5, when the currently selected lookup table LTi is switched to the new lookup table LTj, the level of the correction envelope signal SAE does not become discontinuous and is output from the high frequency amplifier 5b. It is possible to prevent the distortion of the waveform of the output transmission signal that is generated.

In the above embodiment, the case where three types of lookup tables LT1 for low temperature, lookup table LT2 for normal temperature, and lookup table LT3 for high temperature are used as the lookup tables used in the envelope correction processing unit 3 have been described. However, the present invention is not limited to this, and for example, two types of lookup tables are prepared: a low temperature lookup table LT1 below 20° C. and a high temperature lookup table LT3 above 60° C. When the temperature of the high-frequency amplifier 5b detected by the temperature detection unit 6 is an intermediate temperature between the low temperature lookup table LT1 and the high temperature lookup table LT3, as shown in FIG. The level corresponding to the detected temperature may be calculated by an interpolation process in which the levels of the two corrected envelope signals SAE calculated individually by the LT1 and the high temperature lookup table LT3 are equally divided. In this case, only two look-up tables are required, so the storage capacity of the storage unit 8 can be reduced.

Further, instead of equally dividing the levels of the two correction envelope signals SAE calculated individually by the low temperature look-up table LT1 and the high temperature look-up table LT3, for example, the high-frequency amplifier 5b supplies electric power with respect to temperature change at high temperature. When the change in the gain is larger than that at the low temperature, as shown in FIG. 7, the gain is roughened at the low temperature side and becomes denser as it goes to the high temperature side, and the envelope signal correction accuracy at the high temperature side can be improved.

Further, in order to further improve the correction accuracy of the envelope signal SIE in the envelope correction processing unit 3, four or more look-up tables having a narrowed temperature range are stored in the storage unit 8, and the temperature detection signal St from the temperature detection unit 6 is stored. The lookup table may be set finely based on.

Further, in the above embodiment, the case where the level of the corrected envelope signal SAE is calculated from the level of the envelope signal SIE is described with reference to the lookup tables LT1 to LT3, but the present invention is not limited to this. .. For example, an equation is created for each of the characteristic lines L1 to L3 set in the lookup tables LT1 to LT3, for example, a variable x is the level LV1 of the envelope signal SIE, and a variable y is the level LV2 of the corrected envelope signal SAE. Then, the correction operation control unit 3b selects an equation created based on the temperature detection signal St detected by the temperature detection unit 6 and converts it into the equation selected by the correction envelope signal generation unit 3a. The level LV1 of the envelope signal SIE may be substituted to calculate the level LV2 of the corrected envelope signal SAE.

Although the present invention has been described with reference to the specific embodiments, it is not intended to limit the invention by these descriptions. Various embodiments of the invention, as well as various modifications of the disclosed embodiments, will be apparent to persons skilled in the art upon reference to the description of the invention. Therefore, the scope of the claims should be understood to cover these modifications and embodiments included in the scope and gist of the present invention.

DESCRIPTION OF SYMBOLS 1... Transmission signal generation part, 2... Envelope signal generation part, 3... Envelope correction processing part, 3a... Correction envelope signal generation part, 3b... Correction operation control part, 4... Envelope signal processing part, 4a... DAC, 4b... Amplifier 4c... DC power supply, 5... Transmission signal processing unit, 5a... DAC/RF converter, 5b... High frequency amplifier, 6... Temperature detection unit, 7... Level detection unit, 8... Storage unit, 9... Antenna, 10... Power amplification apparatus

Claims (3)

An envelope tracking type power amplification device,
An envelope signal generation unit that generates an envelope signal from the input transmission signal of the baseband,
An envelope signal processing unit for amplifying the envelope signal to generate a control power supply voltage,
A transmission signal processing unit that amplifies an input transmission signal using the control power supply voltage as a power supply voltage to generate an output transmission signal,
A temperature detector for detecting the temperature of the transmission signal processor,
A level detection unit that detects the level of the envelope signal generated by the envelope signal generation unit;
And a envelope correction processing section for outputting a correction envelope signal to input the envelope signal,
The envelope correction processing unit is capable of generating and outputting a plurality of corrected envelope signals having different input/output characteristics according to the detected temperature detected by the temperature detecting unit, and the detected temperature detected by the temperature detecting unit. When the detected level becomes equal to or lower than a predetermined threshold value, the power amplifier device switches to a corrected envelope signal according to the detected temperature after the change . The envelope correction processing unit stores a lookup table for generating a correction envelope signal corresponding to at least two temperatures set at a predetermined temperature interval in the storage unit, and the detected temperature is an intermediate value between the two temperatures. The electric power according to claim 1, wherein when the temperature is the temperature, the level of the correction envelope signal obtained from the two look-up tables stored in the storage unit is interpolated to generate the correction envelope signal. Amplification device. Generates an envelope signal generated based on the input transmission signal, amplifies the generated envelope signal to generate a control power supply voltage, and supplies the generated control power supply voltage as a power supply voltage to the transmission signal processing unit. An envelope tracking power amplification control method for amplifying a signal level of an input transmission signal in a processing unit to generate an output transmission signal,
Detecting the temperature of the transmission signal processing unit,
Detecting the level of the envelope signal,
Generating a plurality of corrected envelope signals having different input/output characteristics according to the detected temperature detected,
If the detected temperature and the detected changes, the envelope tracking method, characterized in that switching to the correction envelope signal corresponding to the previous SL detected temperature after the change when the detection level of the envelope signal is equal to or less than a predetermined threshold value Power amplification control method.

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