CN102185566B - Radio frequency front end circuit and mobile terminal with the circuit - 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

A kind of radio-frequency (RF) front-end circuit and have the portable terminal of this circuit

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.It is the most widely mobile phone standard of current application that full ball Yi moves Tong Xin Xi System (Global System for Mobile Communications, GSM), and there is the mobile communication system according to this phone normalization 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 as much as possible the transmitting power of portable terminal and base station, 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 ratio control amplifying circuit, general by (the Digital to Analog Converter of the digital to analog converter in the baseband circuit, DAC) the ramp signal controlling of output represents 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 controlled by the base station.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), the maximum transmit power level of DCS1800 working frequency range is 0(30dBm), the minimum emissive power rank is 15(0dBm).GSM standard is that strict requirement is arranged for other power excursion of each power stage, is that power changes at ± 2dB for the standard that requires of greatest level.Therefore, strict requirement has also been proposed the control ability of power control circuit.

The compression of power amplification circuit gain is relevant with the size of input signal, and when input signal maintained a very little signal, its input was kept linear relation with outlet chamber, 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, corresponding power output is 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 linear amplification mode, corresponding diagram 1 neutral line district.When input power was very large, 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 comprised 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 contact resistances 204, resistance 204 contact resistances 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 the system power supply mains voltage variations, 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 _LoadDetermine with system power supply supply voltage Vbat,

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

Wherein Vbat is system power supply power supply (the normally battery of portable terminal) voltage, the voltage range 4.2V of its normal operation～3.5V.Calculated as can be known by formula (1), when the system power supply supply voltage changed from 4.2～3.5V, the variation of power output surpassed 1.3dB, as shown in Figure 4.According to the requirement of GSM standard, mobile terminal system 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 connect, worsen systematic function with the base station, the user can not converse.In the production process of actual portable terminal product, after considering the factors such as system calibration, conformity of production, product yield, mobile terminal system has stricter 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 power supply supply voltage, to cause the power output of power amplifier to fluctuate with the variation of system power supply 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

For 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 and power amplification circuit, power amplification circuit comprises driver and the first amplifier, described power amplification circuit also comprises the match circuit that is arranged between described driver and described the first amplifier, the signal of driver output is inputted the first amplifier through match circuit, and match circuit is used for making the first amplifier be operated in linear zone or quasi linear region auto; Power control circuit comprises low-dropout regulator LDO, portable terminal mains voltage variations testing circuit and compensating circuit; Driver is by low-dropout regulator LDO power supply, and the first amplifier 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 the second amplifier, PMOS transistor, the first resistance, the second resistance and the 3rd resistance;

The base band control signal of portable terminal is connected to the positive input of the second amplifier, the output of the second amplifier is connected to the transistorized grid of PMOS, the transistorized source electrode of PMOS is connected to the portable terminal supply voltage, and the transistorized drain electrode of PMOS is the driver power supply; The transistorized drain electrode of PMOS also connects an end of the first resistance, and the other end of the first resistance connects respectively the negative input of the second amplifier and an end of the second resistance, and the other end of the second resistance connects an end of the 3rd resistance, the other end ground connection of the 3rd resistance.

Further, the transistorized drain electrode output voltage of PMOS

V _RampBe base band control signal voltage.

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

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

The reference voltage input circuit is wire or the 7th resistance.

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 to reference voltage.

Further, compensating circuit is compensating resistance, and an end of compensating resistance is connected with the 3rd amplifier, and the other end of compensating resistance is connected between the second resistance and the 3rd resistance.

Further, the supply power voltage of driver:

$V_{\mathrm{out}\_\mathrm{LDO}}=(1+\frac{R_1{R}_4+R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3})V_{\mathrm{ramp}}-\frac{R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3}(\frac{R_5+R_6}{R_6}{V}_{\mathrm{ref}}-\frac{R_5}{R_6}{V}_{\mathrm{bat}}),$ 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 was operated in the peak power output grade, the first amplifier 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 the base band control chip, radio-frequency (RF) transceiver, radio-frequency (RF) front-end circuit and antenna, radio-frequency (RF) front-end circuit is described radio-frequency (RF) front-end circuit.

The present invention can carry out to the radio-frequency power amplifier in the mobile terminal system compensation of system power supply mains voltage variations, reduces the fluctuation of power output.After using this compensation method, when the system power supply 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.

Although describe the present invention in connection 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 the defined spirit of the present invention of appending claims and the scope.

Description of drawings

Accompanying drawing is used to provide a further understanding of the present invention, and consists of the part of specification, is used for together with embodiments of the present invention explaining the present invention, 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-output curve 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-shaped 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 in 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.

Can find out from power amplification circuit mode of operation shown in Figure 1, 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 to be determined by the gain G p of driver and output amplifier, irrelevant with mains voltage variations, namely

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 the system power supply mains voltage variations, need to adjust to quasi linear region auto even linear zone to the mode of operation of output amplifier in the power amplification circuit when the maximum power output.In order to reach this purpose, the present invention arranges match circuit between the driver output amplifier, the type of match circuit can be L-type, T-shaped or Pi type, it also can be the combination in any of L-type, T-shaped 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 that appearance is intelligible to those skilled in the art; The match circuit of L-type, T-shaped and Pi type is respectively shown in Fig. 9 a-Fig. 9 c.By match circuit is carried out impedance transformation, 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, the output voltage of Modulating Power control circuit, and then the input power of adjustment output amplifier realize that the compensation power output is with the purpose of system power supply mains voltage variations.

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 power supply power supply (Vbat) 520.Radio-frequency input signals RFIN enter drive 503, output amplifier output radio frequency output signal RFOUT.By the match circuit 505 among Fig. 5 is carried out impedance transformation, 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.

Power control circuit 501 mainly is made of variable low-dropout regulator (Low voltage drop out regulator, LDO) and system power supply supply voltage Vbat 520 change detecting circuits of output voltage.

LDO is by amplifier 518, PMOS transistor 508, and resistance R 1, resistance R 2 and resistance R 3 form.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 transistorized drain electrode of PMOS is the output node 524 of LDO.The drain electrode contact resistance R1 of PMOS transistor 508, 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 power supply 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 consists of.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 accessed amplifiers 516.The input voltage V of testing circuit _Ref, V _BatAnd output voltage V _Out2The Relations Among expression formula is:

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

When system power supply supply voltage Vbat 520 changed, the output voltage of amplifier 516 can change thereupon, had so just realized the detection to the system power supply 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, the mains voltage variations value that detects is passed to LDO, adjust the output voltage of LDO, as follows by calculating relational expression,

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

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

The below describes the derivation of this expression formula in detail.

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

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

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 system power supply supply voltage Vbat 520 as shown in Figure 6, when system power supply power supply (battery) voltage drop, increase LDO output voltage 524, thereby the power output of driver 503 and driver 504 is increased, so that the input power 526 of the output amplifier of power amplifier 502 increases along with the decline of system power supply supply voltage Vbat 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 the system power supply 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 for the synthesis of the baseband signal that will launch, or the baseband signal that receives is decoded; Radio-frequency (RF) transceiver 82, the baseband signal of coming from 81 transmission of base band control chip is processed and radio frequency signal generation, and the radiofrequency signal that generates sent to radio-frequency (RF) front-end circuit 83, or the radiofrequency signal of coming from radio-frequency (RF) front-end circuit 83 transmission processed and generate baseband signal, and the baseband signal that generates is sent to base band control chip 81; Radio frequency front end chip 83 for the processing of the radiofrequency signal of coming from radio-frequency (RF) transceiver 82 transmission being carried out such as power amplification, or is sent to radio-frequency (RF) transceiver 82 after receiving signal and should receiving the signal processing; Antenna 84, it is connected with radio-frequency (RF) front-end circuit 83, is used for receiving signal or emission from the next signal of radio-frequency (RF) front-end circuit transmission from the external world.

Particularly, when carrying out the signal emission, base band control chip 81 is compiled into the information that will launch base band code (baseband signal) and it is transferred to radio-frequency (RF) transceiver 82,82 pairs of these baseband signals of radio-frequency (RF) transceiver are processed radio frequency signal generation, 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, the radio signal transmission that radio-frequency (RF) front-end circuit 83 will receive by antenna 84 is to radio-frequency signal transceiver 82, 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 with this base band signal transmission 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 (such as phone number or station address), Word message (such as short message literal or website literal), pictorial information etc.

The primary clustering of described base band control chip is processor (such as DSP, ARM etc.) and internal memory (such 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 (502) comprises driver (503,504) and the first amplifier (506), it is characterized in that, described power amplification circuit also comprises the match circuit that is arranged between described driver and described the first amplifier, the signal of driver (503,504) output is inputted the first amplifier (506) through match circuit, and match circuit is used for making the first amplifier 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 the 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 the second amplifier (518), PMOS transistor (508), the first resistance (R1), the second resistance (R2) and the 3rd resistance (R3);

The base band control signal (519) of portable terminal is connected to the positive input of the second amplifier (518), the output of the 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 the first resistance (R1), the other end of the first resistance (R1) connects respectively the negative input of the second amplifier (518) and an end of the second resistance (R2), the other end of the second resistance (R2) connects an end of the 3rd resistance (R3), the other end ground connection of the 3rd 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, the 5th resistance (R5), the 6th 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, the 6th resistance (R6) connects the positive input of portable terminal supply voltage (520) and the 3rd amplifier (516), and the 5th 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 wire or the 7th 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, it is characterized in that, compensating circuit is compensating resistance (R4), and an end of compensating resistance (R4) is connected with the 3rd amplifier, and the other end of compensating resistance is connected between the second resistance (R2) and the 3rd 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):

$V_{\mathrm{out}\_\mathrm{LDO}}=(1+\frac{R_1{R}_4+R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3})V_{\mathrm{ramp}}-\frac{R_1{R}_3}{R_2{R}_4+R_3{R}_4+R_2{R}_3}(\frac{R_5+R_6}{R_6}{V}_{\mathrm{ref}}-\frac{R_5}{R_6}{V}_{\mathrm{bat}}),$ 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. such as the described radio-frequency (RF) front-end circuit of claim 1-8 any one, it is characterized in that when power amplification circuit (501) was operated in the peak power output grade, the 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 such as the described radio-frequency (RF) front-end circuit of claim 1-9 any one.

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