CN102185566A - Technology for controlling radio frequency power amplifier for compensating voltage change of system power supply - Google Patents

Abstract

The invention discloses a radio frequency front-end circuit and a mobile terminal having the circuit. In the radio frequency front-end circuit, a signal output by a driver (503 or 504) is input into a first amplifier (506) through a matching circuit; the matching circuit is used for making the first amplifier work in a linear area or a quasi-linear area; a power control circuit (501) comprises a low differential voltage stabilizer LDO, a mobile terminal power supply voltage change detection circuit and a compensation circuit; the driver (503 or 504) is powered by the low differential voltage stabilizer LDO; the first amplifier (506) is directly powered by a mobile terminal power supply; the output voltage of the mobile terminal power supply voltage change detection circuit is input into the low differential voltage stabilizer LDO through the compensation circuit; and the low differential voltage stabilizer LDO compensates the output voltage of the mobile terminal power supply voltage change detection circuit. By the technology, the voltage change of the system power supply of a radio frequency power amplifier in a mobile terminal system can be compensated, so the fluctuation of output power is reduced.

Description

The radio-frequency power amplifier control technology of replenishment system power supply change in voltage

Technical field

The present invention relates to RF application, relate in particular to a kind of radio-frequency (RF) front-end circuit and have the portable terminal of this circuit.

Background technology

In modern wireless communication systems, the radio-frequency (RF) front-end circuit in the portable terminal is to realize the critical component of radiofrequency signal wireless transmission.Full ball Yi moves Tong Xin Xi System, and (Global System for Mobile Communications GSM) is current application mobile phone standard the most widely, and all there is the mobile communication system of setting up according to this phone standard in most areas, the world.According to GSM joint committee, GSM has 1,500,000,000 user in the whole world, and the user spreads all over more than 140 country.Because there are roaming agreement in many GSM Virtual network operators and other external operators, therefore when the user after other countries, still can continue to use their mobile phone, for vast GSM user, particularly business users, provide a great convenience.

In the GSM cellular communication system, radio-frequency (RF) front-end circuit is to realize the core component of radiofrequency signal wireless transmission, and power control circuit then is the important component part of radio-frequency (RF) front-end circuit.Power control is key technology that improves the availability of frequency spectrum and reduce power loss in the GSM cellular communication system, under the prerequisite that keeps link speech quality, control the transmitting power of portable terminal and base station as much as possible, thereby reach the purpose that reduces phase mutual interference between link.The major function that is integrated in the power control circuit in the radio-frequency (RF) front-end circuit is the power output of power controlling amplifying circuit, general by (the Digital to Analog Converter of the digital to analog converter in the baseband circuit, DAC) Shu Chu ramp signal controlling is represented with Vramp usually.

The working frequency range of GSM can comprise GSM900 and DCS1800 usually, and wherein the tranmitting frequency in the GSM900 working frequency range is 880-915MHz, and the tranmitting frequency in the DCS1800 working frequency range is 1710-1785MHz.The gsm protocol regulation, mobile terminal emitting power can be by base stations control.The base station is by descending slow associated control channel (Slow Associated Control Channel, SACCH), give an order and control the power level of mobile phone, transmitting power between per two adjacent power grades differs 2dB, the maximum transmit power level of GSM900 working frequency range is 5 (33dBm), the minimum emissive power rank is 19 (5dBm), and the maximum transmit power level of DCS1800 working frequency range is 0 (30dBm), and the minimum emissive power rank is 15 (0dBm).GSM standard all is that strict requirement is arranged for other variable power scope of each power stage, for greatest level to require standard be variable power at ± 2dB.Therefore, the control ability to power control circuit has also proposed strict requirement.

The compression of power amplification circuit gain is relevant with the size of input signal, when input signal maintains a very little signal, keeps the relation of linearity between its input and output, i.e. the gain of power amplification circuit maintenance is constant; But when input signal increases to certain limit, the gain of power amplification circuit will no longer keep constant, but be tending towards reducing, and this phenomenon is called gain compression.Usually, pairing power output is a 1dB gain compression point power when small signal gain decline 1dB, shown in P_1dB among Fig. 1.In general, when power output less than 1dB gain compression point power, power amplification circuit is operated in the linear amplification pattern, corresponding diagram 1 neutral line district.When input power was very big, power output no longer changed with input power, and power amplification circuit enters saturation condition, and the power output of this moment is called saturation power, saturation region in the corresponding diagram 1.At the every increase of saturation region input power 3dB, power output changes less than 0.1dB.Power output still has one period stage that slowly changes, quasi linear region auto in the corresponding diagram 2 between 1dB gain compression point power and saturation power.At the every increase of quasi linear region auto input power 1dB, power output increases by 0.1～0.5dB;

The radio-frequency (RF) front-end circuit of general GSM mobile termination is made of power amplification circuit and power control circuit, as shown in Figure 2, comprises power control circuit 201 and power amplification circuit 202.Power amplification circuit 202 is made of driver 207, driver 208, output amplifier 209 and biasing circuit 210, wherein driver 207, driver 208 and output amplifier 209 cascades, biasing circuit 210 provides bias voltage for driver 207, driver 208 and output amplifier 209, radio-frequency input signals RFIN enter drive 208, output amplifier 209 output radio frequency output signal RFOUT.Driver 207 and driver 208 are by the power control circuit power supply, and amplifier is by supply voltage Vbat 203 power supplies.Power control circuit 201 mainly is made up of amplifier 211, PMOS transistor and resistance 203,204, the base band control signal Vramp of portable terminal is connected to the positive input of amplifier 211, the output of amplifier 211 is connected to the grid of PMOS transistor 212, the source electrode of PMOS transistor 212 is connected to supply voltage Vbat 203, and the drain electrode of PMOS transistor 212 is the output node 206 of power control circuit.Output node 206 is driver 207 and driver 208 power supplies.Output node 206 connects resistance 204, and resistance 204 connects resistance 205, resistance 205 ground connection.Node between resistance 204 and the resistance 205 feeds back to amplifier 211 negative input ends.When radio-frequency (RF) front-end circuit shown in Figure 2 was operated in peak power output, the amplifier 209 of power amplification circuit was operated in the saturation region, and the output voltage 206 of power control circuit is not with system's power supply change in voltage, as shown in Figure 3 simultaneously.Power amplifier is operated in the saturation region when peak power output, peak power output is mainly by load impedance R _LoadWith the power supply voltage Vbat of system decision,

$P_{\mathrm{out}\_\max }=\frac{{V_{\mathrm{bat}}}^2}{{2R}_{\mathrm{load}}}---\left(1\right)$

Wherein Vbat is system's power supply (the normally battery of portable terminal) voltage, the voltage range 4.2V of its operate as normal～3.5V.Calculate as can be known by formula (1), when system's power supply voltage when 4.2～3.5V changes, the variation of power output is above 1.3dB, as shown in Figure 4.According to the requirement of GSM standard, mobile terminal system all has strict demand to the power fluctuation excursion of each power grade, and requiring for the fluctuation excursion of peak power output grade is that system's power output changes in ± 2dB.If mobile terminal system changes the scope that has surpassed the GSM standard regulation at the power fluctuation of some power grades, will cause that portable terminal can't effectively be connected, worsen systematic function with the base station, the user can not converse.In the production process of actual portable terminal product, after considering factors such as system calibration, conformity of production, product yield, mobile terminal system has strict more requirement to the output-power fluctuation scope of radio-frequency power amplifier, and the output-power fluctuation scope that in general requires each grade is in ± 1dB.If the described radio-frequency power amplifier of Fig. 2 is not carried out the compensating for variations of system's power supply voltage, to cause the power output of power amplifier to fluctuate with the variation of system's power supply, output-power fluctuation when the peak power output grade surpasses 1.3dB, consistency factor when considering chip manufacturing, when the mass product volume production, can bring serious product yield problem, cause manufacturing cost to increase.

Summary of the invention

At the above-mentioned problems in the prior art, the invention provides a kind of radio-frequency (RF) front-end circuit and have the portable terminal of this circuit.

According to the present invention, a kind of radio-frequency (RF) front-end circuit is provided on the one hand, comprise power control circuit 501 and power amplification circuit 502, power amplification circuit 501 comprises the driver 503,504 and first amplifier 506, the signal of driver 503,504 outputs is imported first amplifier 506 through match circuit, and match circuit is used to make first amplifier to be operated in linear zone or quasi linear region auto; Power control circuit 501 comprises low-dropout regulator LDO, portable terminal mains voltage variations testing circuit and compensating circuit; Driver 503,504 is by low-dropout regulator LDO power supply, and first amplifier 506 is directly powered by the portable terminal power supply; The output voltage of portable terminal mains voltage variations testing circuit is through compensating circuit input low-dropout regulator LDO, and low-dropout regulator LDO carries out voltage compensation to the output voltage of portable terminal mains voltage variations testing circuit.

Further, low-dropout regulator LDO comprises second amplifier 518, PMOS transistor 508, resistance R 1, resistance R 2 and resistance R 3;

The base band control signal 519 of portable terminal is connected to the positive input of second amplifier 518, the output of second amplifier 518 is connected to the grid of PMOS transistor 508, the source electrode of PMOS transistor 508 is connected to portable terminal supply voltage 520, and the drain electrode of PMOS transistor 508 is driver 503,504 power supplies; The drain electrode of PMOS transistor 508 also connects an end of resistance R 1, and the other end of resistance R 1 connects the negative input of second amplifier 518 and an end of resistance R 2 respectively, and the other end of resistance R 2 connects an end of resistance R 3, the other end ground connection of resistance R 3.

Further, the drain electrode output voltage of PMOS transistor 508

V _RampBe base band control signal voltage.

Further, portable terminal mains voltage variations testing circuit comprises the 3rd amplifier 516, and reference voltage provides circuit, resistance R 5, resistance R 6 and reference voltage input circuit;

Reference voltage provides the reference voltage of circuit output to enter into the negative input of the 3rd amplifier 516 by the reference voltage input circuit, resistance R 6 connects the positive input of portable terminal supply voltages 520 and the 3rd amplifier 516, and resistance R 5 is between the positive input of the output of the 3rd amplifier 516 and the 3rd amplifier 516;

The reference voltage input circuit is lead or resistance R 7.

Further, the output voltage of portable terminal mains voltage variations testing circuit

V wherein _RefFor reference voltage provides the output voltage of circuit, V _BatBe the portable terminal supply voltage.

Further, circuit is provided is band-gap reference source circuit 517 to reference voltage.

Further, compensating circuit is a resistance R 4, and an end of resistance R 4 is connected with the 3rd amplifier, and the other end of compensating resistance is connected between resistance R 2 and the resistance R 3.

Further, the supply power voltage of driver 503,504:

V wherein _RampBe base band control signal voltage, V _RefFor reference voltage provides the output voltage of circuit, V _BatBe the portable terminal supply voltage.

Further, when power amplification circuit 501 was operated in the peak power output grade, first amplifier 506 was operated in linear zone or quasi linear region auto.

According to the present invention, a kind of portable terminal is provided on the other hand, comprise base band control chip 81, radio-frequency (RF) transceiver 82, radio-frequency (RF) front-end circuit 83 and antenna 84, radio-frequency (RF) front-end circuit 83 is described radio-frequency (RF) front-end circuit.

The present invention can carry out the compensation of system's power supply change in voltage to the radio-frequency power amplifier in the mobile terminal system, reduces the fluctuation of power output.After using this compensation method, when system's power supply voltage changed from 4.2V to 3.5V, it is constant that the power output of power amplifier keeps.On the other hand, can guarantee in the large-scale production of actual portable terminal product, test process, to improve the yield of product, save manufacturing cost.

Other features and advantages of the present invention will be set forth in the following description.Purpose of the present invention and other advantages can realize and obtain by specifically noted structure in specification, claims and accompanying drawing.

Though will describe the present invention in conjunction with some exemplary enforcements and using method hereinafter, those skilled in the art should be understood to not be intended to the present invention is limited to these embodiment; Otherwise, be intended to cover all substitutes, correction and the equivalent that are included in defined spirit of the present invention of appending claims and the scope.

Description of drawings

Accompanying drawing is used to provide further understanding of the present invention, and constitutes the part of specification, is used from explanation the present invention with embodiments of the invention one, but is not construed as limiting the invention.

Fig. 1 is the mode of operation of power amplification circuit;

Fig. 2 is the structural representation of radio-frequency (RF) front-end circuit in the prior art;

Fig. 3 is the voltage curve of output of power amplification circuit in the prior art;

Fig. 4 be when power amplification circuit is operated in the saturation region in the prior art power output with the mains voltage variations schematic diagram;

Fig. 5 is the structural representation of the radio-frequency (RF) front-end circuit that provides of the embodiment of the invention;

Fig. 6 is the LDO curve of output after the embodiment of the invention provides the supply voltage compensation;

Fig. 7 is the output power curve after the embodiment of the invention provides the supply voltage compensation;

Fig. 8 is the portable terminal that the embodiment of the invention provides;

Fig. 9 a-Fig. 9 c is the match circuit of L type, T type and Pi type.

Embodiment

Describe embodiments of the present invention in detail below with reference to drawings and Examples, how the application technology means solve technical problem to the present invention whereby, and the implementation procedure of reaching technique effect can fully understand, and implement according to this.Need to prove that each feature under the situation of not conflicting among the embodiment of the invention and the embodiment can mutually combine, these all drop within protection scope of the present invention.

From power amplification circuit mode of operation shown in Figure 1 as can be seen, when the power output of power amplification circuit does not reach maximum power level, because the power output of driver is lower, the output amplifier of power amplification circuit is operated in the linear zone pattern, at this moment the power output size of power amplification circuit is by the gain G p of driver and output amplifier decision, irrelevant with mains voltage variations, promptly

P _out＝G _P·P _{in_am} (2)

Wherein, Gp is the product of the gain of the gain of driver and output amplifier, and Pin_am is the power of radio-frequency input signals.

For the variation of compensation power amplifying circuit power output when system's power supply change in voltage, need adjust to quasi linear region auto even linear zone to the mode of operation of output amplifier in the power amplification circuit when maximum power is exported.In order to reach this purpose, the present invention is provided with match circuit between the driver output amplifier, the type of match circuit can be L type, T type or Pi type, it also can be the combination in any of L type, T type and Pi type match circuit, comprise mutual combination and the combination of self (for example two L type match circuit combinations), and the progression of cascade also is not limited to two-stage, for example three grades or more multistage; The parameter of each element can be selected according to the situation of reality in the match circuit, and this is to understand easily to those skilled in the art; The match circuit of L type, T type and Pi type is respectively shown in Fig. 9 a-Fig. 9 c.By match circuit is carried out impedance conversion, can reduce the input power of output amplifier.(power output of GSM900 working frequency range is 33dBm when power amplification circuit is operated in the peak power output grade, the power output of DCS1800 working frequency range is 30dBm), because the input power of output amplifier reduces, so the mode of operation of output amplifier has return back to quasi linear region auto by original saturation region.Because power amplifier has entered into quasi linear region auto, at this moment the characteristic of power amplifier is for when the every increase of input power 1dB, and power output increases by 0.1～0.5dB.By the variation of detection system power supply voltage Vbat, adjust the output voltage of power control circuit, and then adjust the input power of output amplifier, realize the purpose of compensation power output with system's power supply change in voltage.

The radio-frequency (RF) front-end circuit structure chart that Fig. 1 embodiment of the invention is carried.Whole radio-frequency (RF) front-end circuit is made of two parts, power amplification circuit 502 and power controller circuit 501.Power amplification circuit 102 comprises driver 503, driver 504, match circuit 505, output amplifier 506 and biasing circuit 507.Driver 503, driver 504, match circuit 505 and output amplifier 506 cascades, biasing circuit 507 provides bias voltage for driver 503, driver 504 and output amplifier 506.The supply power voltage of driver 503 and driver 504 is provided by power control circuit, and the power supply of output amplifier 506 is directly provided by system's power supply (Vbat) 520.Radio-frequency input signals RFIN enter drive 503, output amplifier output radio frequency output signal RFOUT.By the match circuit among Fig. 5 505 is carried out impedance conversion, can reduce the input power 526 of output amplifier 506.(power output of GSM900 working frequency range is 33dBm when power amplification circuit is operated in the peak power output grade, the power output of DCS1800 working frequency range is 30dBm), because the input power 526 of output amplifier 506 reduces, so the mode of operation of output amplifier 506 has return back to quasi linear region auto by original saturation region.

Mainly (Low voltage drop out regulator LDO) constitutes with the power supply voltage Vbat of system 520 change detecting circuits power control circuit 501 by a variable low-dropout regulator of output voltage.

LDO is by amplifier 518, PMOS transistor 508, and resistance R 1, resistance R 2 and resistance R 3 are formed.The base band control signal Vramp 519 of portable terminal is connected to the positive input of amplifier 518, the output of amplifier 518 is connected to the grid of PMOS transistor 508, the source electrode of PMOS transistor 508 is connected to supply voltage Vbat 520, and the PMOS transistor drain is the output node 524 of LDO.The drain electrode of PMOS transistor 508 connects resistance R 1, and resistance R 1 feeds back to the negative input of amplifier 518 by node 525.Resistance R 2 between node 525 and node 523, resistance R 3 connected nodes 523 and ground.The input voltage V of LDO _RampAnd output voltage V _Out1Between relational expression be:

$V_{\mathrm{out}1}=(1+\frac{R_1}{R_2+R_3})\·V_{\mathrm{ramp}}---\left(3\right)$

System's power supply voltage Vbat 520 change detecting circuits 502 are by amplifier 516, band-gap reference source circuit 517, and resistance R 5, resistance R 6, resistance R 7 constitutes.The output voltage V ref 521 of band-gap reference source circuit 517 enters into the negative input of amplifier 516 by resistance R 7, resistance R 6 connects the positive input of supply voltage Vbat 520 and amplifier 516, and feedback resistance R5 is between the output node 522 and its positive input of amplifier 516; Alternatively, omit resistance R 7 and the direct negative input that the output voltage V ref 521 of band-gap reference source circuit 517 is inserted amplifiers 516.The input voltage V of testing circuit _Ref, V _BatAnd output voltage V _Out2Between relational expression be:

$V_{\mathrm{out}2}=(1+\frac{R_5}{R_6})V_{\mathrm{ref}}-\frac{R_5}{R_6}{V}_{\mathrm{bat}}---\left(4\right)$

When the power supply voltage Vbat of system 520 changed, the output voltage of amplifier 516 can change thereupon, has so just realized the detection to system's power supply voltage.The output node 522 of amplifier 516 is connected to the node 523 of LDO by resistance R 4.By resistance R 4, detected mains voltage variations value is passed to LDO, adjust the output voltage of LDO, as follows by calculating relational expression,

$V_{\mathrm{out}\_\mathrm{LDO}}=(1+\frac{R_1{R}_4+R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3})V_{\mathrm{ramp}}---\left(4\right)$

$-\frac{R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3}(\frac{R_5+R_6}{R_6}{V}_{\mathrm{ref}}-\frac{R_5}{R_6}{V}_{\mathrm{bat}})$

Describe the derivation of this expression formula below in detail.

Among Fig. 5, the output voltage of node 522 is

$V_{522}=(1+\frac{R_5}{R_6})V_{\mathrm{ref}}-\frac{R_5}{R_6}{B}_{\mathrm{Bat}}---\left(5\right)$

Among Fig. 5, the output voltage of node 525 is

V ₅₂₅＝V _ramp (6)

If the output current I of LDO, the output voltage of node 523 are V ₅₂₃, according to kirchhoff electric current and voltage law, it is identical flowing into the electric current that flows out circuit node, therefore

$I=\frac{V_{\mathrm{out}\_\mathrm{LDO}}-V_{525}}{R1}---\left(7\right)$

$I=\frac{V_{525}-V_{523}}{R2}---\left(8\right)$

$I+\frac{V_{522}-V_{523}}{R4}=\frac{V_{523}}{R3}---\left(9\right)$

By (6)～(9), cancellation I and V ₅₂₃, obtain the LDO output voltage and express formula

$V_{\mathrm{out}\_\mathrm{LDO}}=(1+\frac{R_1{R}_4+R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3})V_{\mathrm{ramp}}-\frac{R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3}{V}_{522}---\left(10\right)$

(5) are brought into (10), obtain expression formula (4).

LDO output voltage 524 with the change curve of the power supply voltage Vbat of system 520 as shown in Figure 6, when system's power supply (battery) voltage descends, increase LDO output voltage 524, thereby the power output of driver 503 and driver 504 is increased, make the input power 526 of output amplifier of power amplifier 502 increase along with the decline of the power supply voltage Vbat of system 520, power amplifier driving stage and output stage have just realized the effect of power back-off on the whole like this, radio-frequency power amplifier power output after the employing voltage compensation technology and the relation of Vramp are as shown in Figure 7, when system's power supply voltage changed from 4.2V to 3.5V, it is constant that the power output of output amplifier 506 keeps.

Fig. 8 has shown the mobile terminal structure schematic diagram that the embodiment of the invention provides.Mobile terminal baseband control chip 81, radio-frequency (RF) transceiver 82, radio-frequency (RF) front-end circuit 83 and antenna 84.Base band control chip 81 is used for the synthetic baseband signal that will launch, or the baseband signal that receives is decoded; Radio-frequency (RF) transceiver 82, generate radiofrequency signal to handling from the next baseband signal of base band control chip 81 transmission, and the radiofrequency signal that is generated sent to radio-frequency (RF) front-end circuit 83, or the radiofrequency signal of coming from radio-frequency (RF) front-end circuit 83 transmission handled and generate baseband signal, and the baseband signal that is generated is sent to base band control chip 81; Radio frequency front end chip 83 is used for the radiofrequency signal of coming from radio-frequency (RF) transceiver 82 transmission is carried out processing such as power amplification, or received signal and will this received signal handle after be sent to radio-frequency (RF) transceiver 82; Antenna 84, it is connected with radio-frequency (RF) front-end circuit 83, is used for transmitting the signal of coming from extraneous received signal or emission from radio-frequency (RF) front-end circuit.

Particularly, when carrying out the signal emission, base band control chip 81 is compiled into the information that will launch base band sign indicating number (baseband signal) and it is transferred to radio-frequency (RF) transceiver 82,82 pairs of these baseband signals of radio-frequency (RF) transceiver are handled the generation radiofrequency signal, and with this radio signal transmission to radio-frequency (RF) front-end circuit 83, radio-frequency (RF) front-end circuit 83 will be carried out power amplification and outwards launch by antenna 84 from the radiofrequency signal that radio-frequency (RF) transceiver 82 transmission comes; When carrying out the signal reception, radio-frequency (RF) front-end circuit 83 will be given radio-frequency signal transceiver 82 by the radio signal transmission that antenna 84 receives, radio-frequency signal transceiver 82 will be converted to baseband signal from the radiofrequency signal that radio-frequency (RF) front-end circuit 83 receives, and this baseband signal is transferred to base band control chip 81, will be interpreted as reception information from the baseband signal that the radio-frequency (RF) transceiver transmission comes by base band control chip 61 at last.

Alternatively, the described information that will launch or reception information can comprise audio-frequency information, address information (for example phone number or station address), Word message (for example short message literal or website literal), pictorial information etc.

The primary clustering of described base band control chip is processor (as DSP, ARM etc.) and internal memory (as SRAM, Flash etc.).Alternatively, this base band control chip is realized by one chip.

Claims (10)

1. radio-frequency (RF) front-end circuit, comprise power control circuit (501) and power amplification circuit (502), power amplification circuit (501) comprises driver (503,504) and first amplifier (506), it is characterized in that, the signal of driver (503,504) output is imported first amplifier (506) through match circuit, and match circuit is used to make first amplifier to be operated in linear zone or quasi linear region auto; Power control circuit (501) comprises low-dropout regulator LDO, portable terminal mains voltage variations testing circuit and compensating circuit; Driver (503,504) is by low-dropout regulator LDO power supply, and first amplifier (506) is directly powered by the portable terminal power supply; The output voltage of portable terminal mains voltage variations testing circuit is through compensating circuit input low-dropout regulator LDO, and low-dropout regulator LDO carries out voltage compensation to the output voltage of portable terminal mains voltage variations testing circuit.

2. radio-frequency (RF) front-end circuit as claimed in claim 1 is characterized in that, low-dropout regulator LDO comprises second amplifier (518), PMOS transistor (508), resistance (R1), resistance (R2) and resistance (R3);

The base band control signal (519) of portable terminal is connected to the positive input of second amplifier (518), the output of second amplifier (518) is connected to the grid of PMOS transistor (508), the source electrode of PMOS transistor (508) is connected to portable terminal supply voltage (520), and the drain electrode of PMOS transistor (508) is driver (503,504) power supply; The drain electrode of PMOS transistor (508) also connects an end of resistance (R1), the other end of resistance (R1) connects the negative input of second amplifier (518) and an end of resistance (R2) respectively, the other end of resistance (R2) connects an end of resistance (R3), the other end ground connection of resistance (R3).

3. radio-frequency (RF) front-end circuit as claimed in claim 2 is characterized in that, the drain electrode output voltage of PMOS transistor (508)

V _RampBe base band control signal voltage.

4. radio-frequency (RF) front-end circuit as claimed in claim 2 is characterized in that, portable terminal mains voltage variations testing circuit comprises the 3rd amplifier (516), and reference voltage provides circuit, resistance (R5), resistance (R6) and reference voltage input circuit;

Reference voltage provides the reference voltage of circuit output to enter into the negative input of the 3rd amplifier (516) by the reference voltage input circuit, resistance (R6) connects the positive input of portable terminal supply voltage (520) and the 3rd amplifier (516), and resistance (R5) is positioned between the positive input of the output of the 3rd amplifier (516) and the 3rd amplifier (516);

The reference voltage input circuit is lead or resistance (R7).

5. radio-frequency (RF) front-end circuit as claimed in claim 4 is characterized in that, the output voltage of portable terminal mains voltage variations testing circuit

V wherein _RefFor reference voltage provides the output voltage of circuit, V _BatBe the portable terminal supply voltage.

6. radio-frequency (RF) front-end circuit as claimed in claim 4 is characterized in that, it is band-gap reference source circuit (517) that reference voltage provides circuit.

7. radio-frequency (RF) front-end circuit as claimed in claim 4 is characterized in that, compensating circuit is resistance (R4), and an end of resistance (R4) is connected with the 3rd amplifier, and the other end of compensating resistance is connected between resistance (R2) and the resistance (R3).

8. radio-frequency (RF) front-end circuit as claimed in claim 7 is characterized in that, the supply power voltage of driver (503,504):

V wherein _RampBe base band control signal voltage, V _RefFor reference voltage provides the output voltage of circuit, V _BatBe the portable terminal supply voltage.

9. as any described radio-frequency (RF) front-end circuit of claim 1-8, it is characterized in that when power amplification circuit (501) was operated in the peak power output grade, first amplifier (506) was operated in linear zone or quasi linear region auto.

10. a portable terminal comprises base band control chip (81), radio-frequency (RF) transceiver (82), and radio-frequency (RF) front-end circuit (83) and antenna (84) is characterized in that, radio-frequency (RF) front-end circuit (83) is as any described radio-frequency (RF) front-end circuit of claim 1-9.

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