201233082 六、發明說明： 【發明所屬之技術領域】 本發明涉及射頻領域，尤其涉及一種射頻前端電路及 具有該電路的移動終端。 【先前技術】 在現代無線通信系統中，移動終端中的射頻前端電路 是實現射頻信號無線傳輸的關鍵部件。全球移動通信系統 (Global System for Mobile Communications，GSM)是當 前應用最爲廣泛的移動電話標準，世界絕大多數地區都有 依據該電話標準建立的移動通信系統。據G S Μ聯合委員會 報導，GSM在全球有15億的用戶，並且用戶遍佈140多個 國家。因爲許多GSM網路營運商與其他國外營運商有漫遊 協議，因此當用戶到其他國家之後，仍然可以繼續使用他 們的移動電話，爲廣大的GSM用戶，特別是商務用戶，提 供了極大的便利。 在GSM蜂窩通信系統中，射頻前端電路是實現射頻信 號無線傳輸的核心部件，功率控制電路則是射頻前端電路 的重要組成部分。功率控制是GSM蜂窩通信系統中一項提 高頻譜利用率和減少功率損耗的關鍵技術，在保持鏈路通 話品質的前提下盡可能地控制移動終端和基地台的發射功 率，從而達到減少鏈路間相互干擾的目的。集成在射頻前 端電路中的功率控制電路的主要功能是控制功率放大電路 的輸出功率’一般由基帶電路裏的數位類比轉換器（ -5- 201233082201233082 VI. Description of the Invention: [Technical Field] The present invention relates to the field of radio frequency, and in particular to a radio frequency front end circuit and a mobile terminal having the same. [Prior Art] In a modern wireless communication system, a radio frequency front end circuit in a mobile terminal is a key component for realizing wireless transmission of radio frequency signals. The Global System for Mobile Communications (GSM) is the most widely used mobile phone standard in the world, and mobile communication systems established in accordance with the telephone standard in most parts of the world. According to the Joint Commission of the G SΜ, GSM has 1.5 billion users worldwide and users in more than 140 countries. Because many GSM network operators have roaming agreements with other foreign operators, users can continue to use their mobile phones after they arrive in other countries, which provides great convenience for the majority of GSM users, especially business users. . In the GSM cellular communication system, the RF front-end circuit is the core component for wireless transmission of the RF signal, and the power control circuit is an important component of the RF front-end circuit. Power control is a key technology in the GSM cellular communication system to improve spectrum utilization and reduce power loss. The transmission power of the mobile terminal and the base station can be controlled as much as possible while maintaining the quality of the link call, thereby reducing the link between the links. The purpose of mutual interference. The main function of the power control circuit integrated in the RF front-end circuit is to control the output power of the power amplifier circuit 'generally by the digital analog converter in the baseband circuit ( -5- 201233082
Digital to Analog Converter，DAC)輸出的 ramp 信號控制 ，通常用Vramp表示。 GSM的工作頻段通常可以包括GSM900和DCS1800，其 中GSM900工作頻段中的發射頻率爲880-915MHZ， DCS1800工作頻段中的發射頻率爲1710-1785MHZ。GSM協 定規定，移動終端發射功率是可以被基地台控制的。基地 台透過下行慢速相關控制頻道（Slow Associated Control Channel，SACCH )，發出命令控制手機的發射功率級別 ，每兩個相鄰功率等級之間的發射功率相差2dB，GSM900 工作頻段的最大發射功率級別是5(3 3dBm)，最小發射功率 級別是〗9(5(18111)，0€3 1 800工作頻段的最大發射功率級別 是0(30dBm)，最小發射功率級別是15(0dBm)« GSM標準對 於每個功率級別的功率變化範圍都是有著嚴格的要求，對 於最大等級的要求標準是功率變化在±2dB。因此，對功率 控制電路的控制能力也提出了嚴格的要求》 功率放大電路增益的壓縮與輸入信號的大小有關，當 輸入信號維持在一個很小的信號時，其輸入與輸出間維持 線性的關係，即功率放大電路的增益保持恆定；但當輸入 信號增大到一定範圍時，功率放大電路的增益將不再保持 恆定，而是趨於減小，此現象稱爲增益壓縮。通常，當小 信號增益下降ldB時所對應的輸出功率爲ldB增益壓縮點功 率’如圖1中P_ldB所示。一般來說，當輸出功率小於idB 增益壓縮點功率，功率放大電路工作在線性放大模式，對 應圖1中線性區。當輸入功率很大時，輸出功率不再隨輸 -6- 201233082 入功率發生變化，功率放大電路進入飽和狀態，此時的輸 出功率叫做飽和功率，對應圖1中飽和區。在飽和區輸入 功率每增加3dB，輸出功率變化小於O.ldB。輸出功率在 1 dB增益壓縮點功率和飽和功率之間，仍有—段緩慢變化 的階段’對應圖2中準線性區。在準線性區輸入功率每增 加ldB，輸出功率增加01〜0.5dB; 般的GSM移動終端的射頻前端電路由功率放大電路 和功率控制電路構成，如圖2所示，包括功率控制電路2 0 1 和功率放大電路202。功率放大電路202由驅動器2 07、驅 動器208、輸出放大器2〇9和偏壓電路210構成，其中驅動 器207、驅動器208和輸出放大器209級聯，偏壓電路210爲 驅動器207、驅動器208和輸出放大器209提供偏壓電壓， 射頻輸入信號RFIN輸入驅動器208，輸出放大器209輸出射 頻輸出信號RFOUT。驅動器207和驅動器208由功率控制電 路供電，放大器由電源電壓Vbat 203供電。功率控制電路 201主要由放大器211、PMOS電晶體和電阻203、204組成 ，移動終端的基帶控制信號Vramp連接到放大器21 1的正向 輸入端，放大器21 1的輸出端連接到PMOS電晶體21 2的閘 極，PMOS電晶體212的源極連接到電源電壓Vbat 203， PMOS電晶體212的汲極爲功率控制電路的輸出節點206。 輸出節點206爲驅動器207和驅動器208供電。輸出節點206 連接電阻204，電阻204連接電阻205，電阻205接地。電阻 204和電阻205之間的節點回饋至放大器21 1負輸入端。圖2 所示的射頻前端電路工作在最大輸出功率時，功率放大電 201233082 路的放大器209工作在飽和區，同時功率控制電路的輸出 電壓206不隨系統供電電源電壓變化，如圖3所示。功率放 大器在最大輸出功率時工作在飽和區，最大輸出功率主要 由負載阻抗Ruad和系統供電電源電壓Vbat決定， (1)The ramp signal control of the Digital to Analog Converter (DAC) output is usually expressed in Vramp. The working frequency band of GSM can usually include GSM900 and DCS1800, in which the transmission frequency in the GSM900 working frequency band is 880-915MHZ, and the transmission frequency in the DCS1800 working frequency band is 1710-1785MHZ. According to the GSM agreement, the mobile terminal's transmit power can be controlled by the base station. The base station sends a command to control the transmit power level of the mobile phone through the downlink slow associated control channel (SACCH). The transmit power between each two adjacent power levels differs by 2 dB, and the maximum transmit power level of the GSM900 operating band. It is 5 (3 3dBm), the minimum transmit power level is 〖9 (5111), the maximum transmit power level of 0€3 1 800 working band is 0 (30dBm), and the minimum transmit power level is 15 (0dBm) « GSM standard There is a strict requirement for the power variation range of each power level. For the maximum level, the required power is ±2 dB. Therefore, strict requirements are imposed on the control capability of the power control circuit. Compression is related to the size of the input signal. When the input signal is maintained at a small signal, the input and output maintain a linear relationship, that is, the gain of the power amplifier circuit remains constant; but when the input signal increases to a certain range, The gain of the power amplifier circuit will no longer remain constant, but tends to decrease. This phenomenon is called gain compression. Usually, The output power corresponding to the small signal gain drop ldB is ldB gain compression point power' as shown in P_ldB in Figure 1. In general, when the output power is less than the idB gain compression point power, the power amplifier circuit works in linear amplification mode, corresponding The linear region in Figure 1. When the input power is large, the output power no longer changes with the input power of -6-201233082, and the power amplifier circuit enters a saturated state. The output power at this time is called saturated power, corresponding to the saturation region in Figure 1. For every 3dB increase in input power in the saturation region, the output power variation is less than O.ldB. The output power is between 1 dB gain compression point power and saturation power, and there is still a period of slowly changing section corresponding to the quasi-linear region in Figure 2. In the quasi-linear region, the input power is increased by 01~0.5dB for each increase of ldB; the RF front-end circuit of the GSM mobile terminal is composed of a power amplifying circuit and a power control circuit, as shown in FIG. 2, including the power control circuit 2 0 1 And a power amplifying circuit 202. The power amplifying circuit 202 is composed of a driver 206, a driver 208, an output amplifier 2〇9, and a bias circuit 210, wherein the driver The 207, the driver 208 and the output amplifier 209 are cascaded. The bias circuit 210 supplies a bias voltage to the driver 207, the driver 208 and the output amplifier 209. The RF input signal RFIN is input to the driver 208, and the output amplifier 209 outputs the RF output signal RFOUT. The 207 and the driver 208 are powered by a power control circuit, and the amplifier is powered by a power supply voltage Vbat 203. The power control circuit 201 is mainly composed of an amplifier 211, a PMOS transistor and resistors 203, 204, and the baseband control signal Vramp of the mobile terminal is connected to the amplifier 21 1 At the forward input, the output of the amplifier 21 1 is connected to the gate of the PMOS transistor 21 2 , the source of the PMOS transistor 212 is connected to the supply voltage Vbat 203, and the output node 206 of the PMOS transistor 212 is the power control circuit. . Output node 206 powers driver 207 and driver 208. The output node 206 is connected to the resistor 204, the resistor 204 is connected to the resistor 205, and the resistor 205 is grounded. The node between resistor 204 and resistor 205 is fed back to the negative input of amplifier 21 1 . When the RF front-end circuit shown in Figure 2 operates at the maximum output power, the amplifier 209 of the power amplifier circuit 201233082 operates in the saturation region, and the output voltage 206 of the power control circuit does not change with the system power supply voltage, as shown in Figure 3. The power amplifier operates in the saturation region at the maximum output power, and the maximum output power is mainly determined by the load impedance Ruad and the system power supply voltage Vbat, (1)
Pou, 其中V b a t是系統供電電源（通常是移動終端的電池） 電壓，其正常工作的電壓範園4_2V〜3_5V。由公式（1) 計算可知，當系統供電電源電壓從4 · 2〜3 · 5 V變化時，輸 出功率的變化超過1.3.dB，如圖4所示。根據GSM標準的要 求，移動終端系統對每個功率等級的功率波動變化範圍都 是有著嚴格要求的，對於最大輸出功率等級的波動變化範 圍要求是系統輸出功率變化在±2dB以內。如果移動終端系 統在某一個功率等級的功率波動變化超過了 GSM標準規定 的範圍，將導致移動終端無法和基地台進行有效的連接、 惡化系統性能、用戶將不能進行通話。在實際移動終端產 品的生產過程中，考慮到系統校準、生產一致性、產品良 率等因素後，移動終端系統對射頻功率放大器的輸出功率 波動範圍有著更加嚴格的要求，一般來說要求每個等級的 輸出功率波動範圍在± 1 dB以內。如果不對圖2所述的射頻 功率放大器進行系統供電電源電壓的變化補償，將導致功 率放大器的輸出功率隨系統供電電源的變化而波動，在最 大輸出功率等級時的輸出功率波動超過1 · 3 d B，考慮到晶 201233082 片製造時一致性因素’在大規模產品量產時會帶來嚴重的 產品良率問題，導致製造成本增加。 【發明內容】 針對現有技術中存在的上述問題，本發明提供了一種 射頻前端電路及具有該電路的移動終端。 根據本發明，一方面提供了一種射頻前端電路，包括 功率控制電路501和功率放大電路502 ，功率放大電路501 包括驅動器503、5 04和第一放大器506，驅動器503、504 輸出的信號經匹配電路輸入第一放大器5 06，匹配電路用 於使第一放大器工作在線性區或準線性區；功率控制電路 501包括低壓差穩壓器LDO、移動終端電源電壓變化檢測 電路和補償電路；驅動器5 03、5 04連接到低壓差穩壓器 LDO，第一放大器5 06連接到移動終端電源；移動終端電 源電壓變化檢測電路控制低壓差穩壓器LDO的輸出電壓値 ，從而減小第一放大器輸出功率隨移動終端電源電壓的變 化量。 進一步地，低壓差穩壓器LDO包括第二放大器518， PMOS電晶體508，電阻R1，電阻R2和電阻R3 ; 移動終端的基帶控制信號5 1 9連接到第二放大器5 1 8的 正向輸入端，第二放大器518的輸出端連接到PMOS電晶體 508的閘極，PMOS電晶體508的源極連接到移動終端電源 電壓520，PMOS電晶體508的汲極爲驅動器5 03、504供電 ;PMOS電晶體5 08的汲極還連接電阻R1的一端，電阻R1的 201233082 另一端分別連接第二放大器518的負向輸入端和電阻R2的 一端’電阻R2的另一端連接電阻R3的一端，電阻R3的另 —端接地。 進一步地，PMOS電晶體508的汲極輸出電壓 —^—)V 尽+弋〜 Κ-Ρ =(1 爲基帶控制信號電壓。 進一步地，移動終端電源電壓變化檢測電路包括第三 放大器516，參考電壓提供電路，電阻R5，電阻R6和參考 電壓輸入電路； 參考電壓提供電路輸出的參考電壓通過參考電壓輸入 電路進入到第三放大器516的負向輸入端，電阻R6連接移 動終端電源電壓520和第三放大器516的正向輸入端，電阻 R5位於第三放大器516的輸出端和第三放大器516的正向輸 入端之間； 參考電壓輸入電路爲導線或者電阻R7。 進一步地，移動終端電源電壓變化檢測電路的輸出電 壓+ ’其中k爲參考電壓提供電路的輸出 ^6 火6 電壓，L爲移動終端電源電壓。 進一步地，參考電壓提供電路爲帶隙參考源電路517 進—步地，補償電路爲電阻R4，電阻R4的一端與第三 放大器連接，補償電阻的另一端連接在電阻R2和電阻R3之 間。 進一步地，驅動器503、504的供電電壓： -10- 201233082 Κ,α + R2R4 + J^R4 -l· R2R3 y^reimp R2R4 + 尺声4 + R2R3 R6 ㈣ K6 其中匕_爲基帶控制信號電壓，匕/爲參考電壓提供電路的 輸出電壓，L爲移動終端電源電壓。 進一步地，功率放大電路501工作在最大輸出功率等 級時，第一放大器506工作在線性區或準線性區。 根據本發明，另一方面提供了一種移動終端，包括基 帶控制晶片81，射頻收發器82，射頻前端電路83和天線84 ，射頻前端電路83爲所述的射頻前端電路。 本發明可以對移動終端系統中的射頻功率放大器進行 系統供電電源電壓變化的補償，減小輸出功率的波動。使 用該補償方法後，當系統供電電源電壓從4 · 2 V到3.5 V變化 時，功率放大器的輸出功率保持恆定。另一方面，可以保 證在實際移動終端產品大規模生產、測試過程中提高產品 的良率，節約製造成本。 本發明的其他特徵和優點將在隨後的說明書中闡述。 本發明的目的和其他優點可透過在說明書、申請專利範圍 以及附圖中所特別指出的結構來實現和獲得。 雖然在下文中將結合一些示例性實施及使用方法來描 述本發明，但本領域技術人員應當理解爲並不旨在將本發 明限制於這些實施例；反之，旨在覆蓋包含在所附的申請 專利範圍所定義的本發明的精神與範圍內的所有替代品、 修正及等效物。 -11 - 201233082 【實施方式】 . 以下將結合附圖及實施例來詳細說明本發明的實施方 式’借此對本發明如何應用技術手段來解決技術問題，以 及達成技術效果的實現過程能充分理解，並據以實施。需 要說明的是，在不衝突的情況下本發明實施例以及實施例 中的各個特徵可以相互結合，這些均落在本發明的保護範 圍之內。 從圖1所示的功率放大電路工作模式可以看出，當功 率放大電路的輸出功率沒有達到最大功率等級時，由於驅 動器的輸出功率較低，功率放大電路的輸出放大器工作在 線性區模式，這時功率放大電路的輸出功率大小是由驅動 器和輸出放大器的增益Gp決定的，與電源電壓變化無關， 即 p〇u, =Gp-Pinam (2) 其中’ Gp是驅動器的增益和輸出放大器的增益的乘積 ，Pin_am是射頻輸入信號的功率。 爲了補償功率放大電路在系統供電電源電壓變化時輸 出功率的變化’需要把功率放大電路中輸出放大器在最大 功率輸出時的工作模式調整到準線性區甚至線性區。爲了 達到這一目的，本發明在驅動器輸出放大器之間設置匹配 電路.，匹配電路的類型可以爲L型、T型或者Pi型，也可以 是L型、T型和Pi型匹配電路的任意組合，包括相互組合和 自身的組合（例如兩個L型匹配電路組合），並且級聯的 級數也不限於兩級，例如三級或更多級；匹配電路中各元 -12- 201233082 件的參數可以根據實際的情況進行選定’這對於本領域技 術人員而言是容易理解的：L型、τ型和？1型的匹配電路分 別如圖9a-圖9 c所示。透過對匹配電路進行阻抗變換’可 以把輸出放大器的輸入功率降低。當功率放大電路工作在 最大輸出功率等級時（GSM900工作頻段的輸出功率爲 33dBm，DCS1800工作頻段的輸出功率爲30dBm)，由於 輸出放大器的輸入功率降低’因此輸出放大器的工作模式 由原來的飽和區退回到了準線性區。由於功率放大器進入 到了準線性區，這時功率放大器的特性爲當輸入功率每增 加1 d B時，輸出功率增加〇 · 1〜〇 · 5 d B。透過檢測系統供電 電源電壓Vbat的變化，調整功率控制電路的輸出電壓，進 而調整輸出放大器的輸入功率，實現補償輸出功率隨系統 供電電源電壓變化的目的。 圖1本發明實施例提的射頻前端電路結構圖。整個射 頻前端電路由兩部分構成，功率放大電路502和功率控制 器電路501。功率放大電路102包括驅動器503、驅動器504 、匹配電路505、輸出放大器506和偏壓電路507。驅動器 5 03、驅動器5 04、匹配電路505和輸出放大器5 06級聯，偏 壓電路507爲驅動器503、驅動器504和輸出放大器506提供 偏壓電壓。驅動器503和驅動器504的供電電壓由功率控制 電路提供，輸出放大器5 06的供電直接由系統供電電源（ Vbat) 520提供。射頻輸入信號RFIN輸入驅動器503，輸出 放大器輸出射頻輸出信號RFOUT。透過對圖5中的匹配電 路505進行阻抗變換’可以把輸出放大器506的輸入功率 -13- 201233082 5 26降低。當功率放大電路工作在最大輸出功率等級時（ GSM900工作頻段的輸出功率爲33dBm，DCS1800工作頻段 的輸出功率爲30dBm)，由於輸出放大器506的輸入功率 526降低，因此輸出放大器506的工作模式由原來的飽和區 退回到了準線性區。 功率控制電路501主要由一個輸出電壓可變的低壓差 穩壓器（Low voltage drop out regulator，LDO)和系統供 電電源電壓Vbat 5 20變化檢測電路構成。 LDO由放大器518，PMOS電晶體508，電阻R1，電阻 R2和電阻R3組成。移動終端的基帶控制信號Vr amp 5 19連 接到放大器518的正向輸入端，放大器518的輸出連接到 PMOS電晶體508的閘極，PMOS電晶體508的源極連接到電 源電壓Vbat 5 20，PMOS電晶體的汲極爲LDO的輸出節點 5 24。PMOS電晶體5 08的汲極連接電阻R1，電阻R1通過節 點525回饋回放大器5 1 8的負向輸入端。電阻R2位於節點 5 25和節點5 2 3之間，電阻R3連接節點5 23和地。LDO的輸 入電壓Vramp和輸出電壓Vmu之間的關係運算式爲： (3) )-Vrm 系統供電電源電壓Vbat 520變化檢測電路502由放大 器516，帶隙參考源電路517，電阻R5，電阻R6，電阻R7 構成。帶隙參考源電路517的輸出電壓Vref 521通過電阻 R7進入到放大器516的負向輸入端，電阻R6連接電源電壓 -14- 201233082Pou, where V b a t is the voltage of the system power supply (usually the battery of the mobile terminal), and its normal operating voltage is 4_2V~3_5V. Calculated by equation (1), when the system power supply voltage changes from 4 · 2 to 3 · 5 V, the output power changes by more than 1.3 dB, as shown in Figure 4. According to the requirements of the GSM standard, the mobile terminal system has strict requirements for the power fluctuation range of each power level. For the fluctuation range of the maximum output power level, the system output power variation is within ±2 dB. If the power fluctuation of the mobile terminal system at a certain power level exceeds the range specified by the GSM standard, the mobile terminal cannot effectively connect with the base station, deteriorate the system performance, and the user will not be able to make a call. In the production process of actual mobile terminal products, after considering factors such as system calibration, production consistency, and product yield, the mobile terminal system has stricter requirements on the output power fluctuation range of the RF power amplifier, and generally requires each The level of output power fluctuates within ± 1 dB. If the RF power amplifier described in Figure 2 is not compensated for the variation of the system power supply voltage, the output power of the power amplifier will fluctuate with the change of the system power supply. The output power fluctuation at the maximum output power level exceeds 1 · 3 d. B, considering that the consistency factor of the production of the crystal 201233082 sheet will cause serious product yield problems in mass production, resulting in an increase in manufacturing costs. SUMMARY OF THE INVENTION In view of the above problems in the prior art, the present invention provides a radio frequency front end circuit and a mobile terminal having the same. According to the present invention, in one aspect, a radio frequency front end circuit is provided, including a power control circuit 501 and a power amplifying circuit 502. The power amplifying circuit 501 includes drivers 503, 504 and a first amplifier 506. The signals output by the drivers 503, 504 are matched by a matching circuit. Inputting a first amplifier 506, the matching circuit is configured to operate the first amplifier in a linear region or a quasi-linear region; the power control circuit 501 includes a low dropout regulator LDO, a mobile terminal power supply voltage change detecting circuit and a compensation circuit; and the driver 5 03 , 5 04 is connected to the low dropout regulator LDO, the first amplifier 506 is connected to the mobile terminal power supply; the mobile terminal power supply voltage change detection circuit controls the output voltage 値 of the low dropout regulator LDO, thereby reducing the output power of the first amplifier The amount of change with the power supply voltage of the mobile terminal. Further, the low dropout regulator LDO includes a second amplifier 518, a PMOS transistor 508, a resistor R1, a resistor R2 and a resistor R3; the baseband control signal 51 of the mobile terminal is connected to the forward input of the second amplifier 5 1 8 The output of the second amplifier 518 is connected to the gate of the PMOS transistor 508, the source of the PMOS transistor 508 is connected to the mobile terminal power supply voltage 520, and the NMOS transistor 508 of the PMOS transistor 508 is powered by the driver 503, 504. The drain of the crystal 5 08 is also connected to one end of the resistor R1, and the other end of the resistor R1 201233082 is connected to the negative input terminal of the second amplifier 518 and the end of the resistor R2 respectively. The other end of the resistor R2 is connected to one end of the resistor R3, and the resistor R3 The other end is grounded. Further, the drain output voltage of the PMOS transistor 508 is ^ ) Κ Κ Ρ Ρ = (1 is the baseband control signal voltage. Further, the mobile terminal power supply voltage change detecting circuit includes the third amplifier 516, reference The voltage supply circuit, the resistor R5, the resistor R6 and the reference voltage input circuit; the reference voltage outputted by the reference voltage supply circuit enters the negative input terminal of the third amplifier 516 through the reference voltage input circuit, and the resistor R6 connects the mobile terminal power supply voltage 520 and the The forward input of the three amplifiers 516, the resistor R5 is located between the output of the third amplifier 516 and the forward input of the third amplifier 516; the reference voltage input circuit is a wire or a resistor R7. Further, the power supply voltage of the mobile terminal changes The output voltage of the detection circuit + 'where k is the output of the reference voltage supply circuit ^6 fire 6 voltage, L is the mobile terminal supply voltage. Further, the reference voltage supply circuit is the bandgap reference source circuit 517 step by step, the compensation circuit For the resistor R4, one end of the resistor R4 is connected to the third amplifier, and the other end of the compensation resistor is connected to the resistor R2 and Further, the power supply voltage of the drivers 503, 504: -10- 201233082 Κ, α + R2R4 + J^R4 - l · R2R3 y^reimp R2R4 + 尺 4 + R2R3 R6 (4) K6 where 匕 _ is The baseband control signal voltage, 匕/ provides the output voltage of the circuit for the reference voltage, and L is the mobile terminal power supply voltage. Further, when the power amplifying circuit 501 operates at the maximum output power level, the first amplifier 506 operates in a linear region or a quasi-linear region. According to another aspect of the present invention, there is provided a mobile terminal comprising a baseband control chip 81, a radio frequency transceiver 82, a radio frequency front end circuit 83 and an antenna 84, and the radio frequency front end circuit 83 is the radio frequency front end circuit. The RF power amplifier in the terminal system compensates for the change of the system power supply voltage, and reduces the fluctuation of the output power. After using this compensation method, the output power of the power amplifier when the system power supply voltage changes from 4 · 2 V to 3.5 V Keep it constant. On the other hand, it can guarantee the improvement of product yield during the mass production and testing of actual mobile terminal products. Other features and advantages of the invention will be set forth in the description which follows. The objectives and other advantages of the invention will be realized and attained by The invention will be described in connection with some exemplary embodiments and methods of use, but those skilled in the art should understand that the invention is not intended to be limited to the embodiments; 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 The application of technical means to solve technical problems, and the realization process of achieving technical effects can be fully understood and implemented accordingly. It should be noted that the embodiments of the present invention and the various features of the embodiments may be combined with each other without conflict, and these fall within the scope of protection of the present invention. It can be seen from the working mode of the power amplifying circuit shown in FIG. 1 that when the output power of the power amplifying circuit does not reach the maximum power level, since the output power of the driver is low, the output amplifier of the power amplifying circuit operates in the linear zone mode. The output power of the power amplifier circuit is determined by the gain Gp of the driver and the output amplifier, independent of the supply voltage variation, ie p〇u, =Gp-Pinam (2) where 'Gp is the gain of the driver and the gain of the output amplifier The product, Pin_am, is the power of the RF input signal. In order to compensate for the change in output power of the power amplifying circuit when the system power supply voltage changes, it is necessary to adjust the operating mode of the output amplifier in the power amplifying circuit at the maximum power output to the quasi-linear region or even the linear region. In order to achieve this, the present invention provides a matching circuit between the driver output amplifiers. The matching circuit type may be L-type, T-type or Pi-type, or may be any combination of L-type, T-type and Pi-type matching circuits. , including combination of each other and their own (for example, two L-type matching circuit combinations), and the number of cascaded stages is not limited to two levels, such as three or more levels; each element of the matching circuit is -12-201233082 The parameters can be selected according to the actual situation'. This is easily understood by those skilled in the art: L-type, τ-type and? The matching circuit of type 1 is shown in Figures 9a - 9c, respectively. The input power of the output amplifier can be reduced by performing impedance transformation on the matching circuit. When the power amplifier circuit operates at the maximum output power level (the output power of the GSM900 operating band is 33dBm, the output power of the DCS1800 operating band is 30dBm), because the input power of the output amplifier is reduced, the operating mode of the output amplifier is from the original saturation region. Returned to the quasi-linear region. Since the power amplifier enters the quasi-linear region, the characteristics of the power amplifier are such that when the input power is increased by 1 d B, the output power is increased by 1 1 to 〇 · 5 d B. Through the detection system power supply voltage Vbat changes, adjust the output voltage of the power control circuit, and then adjust the input power of the output amplifier to achieve the purpose of compensating the output power with the system power supply voltage. FIG. 1 is a structural diagram of a radio frequency front end circuit according to an embodiment of the present invention. The entire RF front end circuit is composed of two parts, a power amplifying circuit 502 and a power controller circuit 501. The power amplifying circuit 102 includes a driver 503, a driver 504, a matching circuit 505, an output amplifier 506, and a bias circuit 507. The driver 503, the driver 504, the matching circuit 505, and the output amplifier 506 are cascaded, and the bias circuit 507 supplies a bias voltage to the driver 503, the driver 504, and the output amplifier 506. The supply voltages for driver 503 and driver 504 are provided by a power control circuit, and the supply of output amplifier 506 is provided directly by system power supply (Vbat) 520. The RF input signal RFIN is input to the driver 503, and the output amplifier outputs an RF output signal RFOUT. The input power -13 - 201233082 5 26 of the output amplifier 506 can be lowered by performing impedance transformation on the matching circuit 505 in FIG. When the power amplifying circuit operates at the maximum output power level (the output power of the GSM900 operating band is 33 dBm and the output power of the DCS1800 operating band is 30 dBm), since the input power 526 of the output amplifier 506 is lowered, the operating mode of the output amplifier 506 is The saturation region returns to the quasi-linear region. The power control circuit 501 is mainly composed of a low voltage drop out regulator (LDO) having a variable output voltage and a system supply voltage Vbat 5 20 change detecting circuit. The LDO is composed of an amplifier 518, a PMOS transistor 508, a resistor R1, a resistor R2, and a resistor R3. The baseband control signal Vr amp 5 19 of the mobile terminal is coupled to the forward input of amplifier 518, the output of amplifier 518 is coupled to the gate of PMOS transistor 508, and the source of PMOS transistor 508 is coupled to supply voltage Vbat 5 20, PMOS The 汲 of the transistor is extremely the output node of the LDO 5 24 . The drain of the PMOS transistor 508 is connected to the resistor R1, and the resistor R1 is fed back to the negative input of the amplifier 5 1 8 via the node 525. Resistor R2 is located between node 5 25 and node 5 2 3, and resistor R3 is connected to node 5 23 and ground. The relationship between the input voltage Vramp of the LDO and the output voltage Vmu is: (3)) -Vrm system power supply voltage Vbat 520 change detection circuit 502 is composed of amplifier 516, bandgap reference source circuit 517, resistor R5, resistor R6, Resistor R7 is formed. The output voltage Vref 521 of the bandgap reference source circuit 517 enters the negative input terminal of the amplifier 516 through the resistor R7, and the resistor R6 is connected to the power supply voltage -14-201233082
Vbat 5 20和放大器516的正向輸入端，回饋電阻R5位於放 大器516的輸出節點522和其正向輸入端之間；替代地，省 略電阻R7而直接將帶隙參考源電路517的輸出電壓Vref 521接入放大器516的負向輸入端。檢測電路的輸入電壓 Vref、vbat和輸出電壓vQUt2之間關係運算式爲： 匕,"2 = (1+争)〜-§^, ⑷ K6 Κ6 當系統供電電源電壓Vbat 52 0發生變化時，放大器 5 1 6的輸出電壓會隨之變化，這樣就實現了對系統供電電 源電壓的檢測。放大器516的輸出端節點522通過電阻R4連 接到LD Ο的節點5 2 3。通過電阻R4，把檢測到的電源電壓 變化値傳遞給LDO，調整LDO的輸出電壓，透過計算得出 關係運算式如下， (4)At the forward input of Vbat 5 20 and amplifier 516, feedback resistor R5 is located between output node 522 of amplifier 516 and its forward input; instead, resistor R7 is omitted and the output voltage of band gap reference source circuit 517 is directly Vref 521 is coupled to the negative input of amplifier 516. The relationship between the input voltage Vref, vbat and the output voltage vQUt2 of the detection circuit is: 匕, "2 = (1+ 争)~-§^, (4) K6 Κ6 When the system power supply voltage Vbat 52 0 changes, The output voltage of the amplifier 5 16 will change accordingly, thus achieving the detection of the system power supply voltage. Output node 522 of amplifier 516 is coupled via resistor R4 to node 5 2 3 of LD 。. Through the resistor R4, the detected power supply voltage change 値 is transmitted to the LDO, and the output voltage of the LDO is adjusted, and the relational expression is calculated as follows: (4)
ri-L 下面詳細說明該運算式的推導過程。 圖5中，節點522的輸出電壓爲 ^522 =^1 + ^ Vref ~ ^ VBa! ⑸ -15- 201233082 圖5中，節點52 5的輸出電壓爲 ^525 = Καη,ρ (6) 設LDO的輸出電流I，節點523的輸出電壓爲v 5 2 3，根 據基爾霍夫電壓電流定律，流入和流出電路節點的電流是 相同的，因此 (7) (8) (9)ri-L The derivation process of this expression is described in detail below. In Figure 5, the output voltage of node 522 is ^522 =^1 + ^ Vref ~ ^ VBa! (5) -15- 201233082 In Figure 5, the output voltage of node 52 5 is ^525 = Καη, ρ (6) is set by LDO Output current I, the output voltage of node 523 is v 5 2 3, according to Kirchhoff's law of voltage and current, the current flowing into and out of the circuit node is the same, so (7) (8) (9)
Kilt LDO ~ ^525 τ _ ^525 ~ ^523 "~~R2~ j ! ^522 ~ ^523 _ ^523 —"R4 —_ R3 由（6 )〜（9 )，消去I和V 5 2 3，得到LDO輸出電壓運 算式 V =(1 + f丨及4 + 及1 及3——ψ__^3_γ (1〇) 。'“-wo、r2r4+r3W3k_ R2W4+R2Rivm uo; 將（5 )帶入（1 0 )，得到運算式（4 )。 LDO輸出電壓524隨系統供電電源電壓Vbat 520的變化 曲線如圖6所示，當系統供電電源（電池）電壓下降時， 增大LDO輸出電壓5 24，從而使驅動器5 03和驅動器504的 輸出功率增大，使得功率放大器5 02的輸出放大器的輸入 功率526隨著系統供電電源電壓Vbat 5 20的下降而增加， -16- 201233082 這樣功率放大器驅動級和輸出級整體上就實現了功率補償 的效果，採用電壓補償技術之後的射頻功率放大器輸出功 率與Vramp的關係如圖7所示，當系統供電電源電壓從4.2V 到3.5 V變化時，輸出放大器5 06的輸出功率保持恆定。 圖8顯示了本發明實施例提供的移動終端結構示意圖 。移動終端基帶控制晶片8 1，射頻收發器82、射頻前端電 路8 3以及天線8 4。基帶控制晶片8 1用於合成將要發射的基 帶信號，或對接收到的基帶信號進行解碼：射頻收發器8 2 ，對從基帶控制晶片8 1傳輸來的基帶信號進行處理而生成 射頻信號，並將所生成的射頻信號發送到射頻前端電路83 ，或對從射頻前端電路83傳輸來的射頻信號進行處理而生 成基帶信號，並將所生成的基帶信號發送到基帶控制晶片 8 1 ;射頻前端晶片83，用於對從射頻收發器82傳輸來的射 頻信號進行諸如功率放大的處理，或接收信號並將該接收 信號處理後發送至射頻收發器8 2 ;天線8 4，其與射頻前端 電路8 3相連接，用於從外界接收信號或者發射從射頻前端 電路傳輸來的信號。 具體而言，進行信號發射時，基帶控制晶片8 1把要發 射的資訊編譯成基帶碼（基帶信號）並將其傳輸給射頻收 發器82，射頻收發器82對該基帶信號進行處理生成射頻信 號，並將該射頻信號傳輸到射頻前端電路8 3，射頻前端電 路83將從射頻收發器82傳輸來的射頻信號進行功率放大並 通過天線84向外發射；進行信號接收時，射頻前端電路83 將通過天線8 4接收到的射頻信號傳輸給射頻信號收發器8 2 -17- 201233082 ’射頻信號收發器8 2將從射頻前端電路8 3接收到的射頻信 號轉換爲基帶信號，並將該基帶信號傳輸到基帶控制晶片 8 1 ’最後由基帶控制晶片6 1將從射頻收發器傳輸來的基帶 信號解譯爲接收資訊》 替代地，該要發射的資訊或者接收資訊可以包括音頻 資訊、位址資訊（例如手機號碼或網站位址）、文字資訊 (例如短資訊文字或網站文字）、圖片資訊等。 該基帶控制晶片的主要元件爲處理器（如DSP、ARM 等）和記憶體（如SRAM、Flash等）。替代地，該基帶控 制晶片由單一晶片實現。 【圖式簡單說明】 附圖用來提供對本發明的進一步理解，並且構成說明 書的一部分，與本發明的實施例一起用於解釋本發明，但 並不構成對本發明的限制。 圖1是功率放大電路的工作模式； 圖2是現有技術中射頻前端電路的結構示意圖； 圖3是現有技術中功率放大電路的電壓輸出曲線； 圖4是現有技術中功率放大電路工作在飽和區時輸出 功率隨電源電壓變化示意圖； 圖5是本發明實施例提供的射頻前端電路的結構示意 圖； 圖6是本發明實施例提供電源電壓補償後的LDO輸出 曲線； -18- 201233082 圖7是本發明實施例提供電源電壓補償後的輸出功率 曲線； 圖8是本發明實施例提供的移動終端； 圖9a-圖9c是L型、T型和Pi型的匹配電路。 【主要元件符號說明】 2 Ο 1 :功率控制電路 202:功率放大電路 203 :電源電壓Vbat 204 :電阻 205 :電阻 206 :輸出節點 2 1 1 :放大器 2 1 2 :鬧極 2 1 0 :偏壓電路 2 0 7 :驅動器 2 0 8 :驅動器 2 09 :驅動器 5 0 1 :功率放大電路 502:功率放大電路 · 5 03 :驅動器 5 04 :驅動器 5 0 5 :匹配電路 506:輸出放大器 -19- 201233082 508: PMOS電晶體 516 :放大器 5 1 7 :帶隙參考源電路 5 1 8 :第二放大器 5 1 9 :基帶控制信號 5 2 0 :系統供電電源 5 2 2 :輸出節點 5 2 3 :節點 5 2 4 :輸出電壓 5 2 5 :節點 5 2 6 :輸入功率 5 0 7 :偏壓電路 8 1 :基帶控制晶片 82 :射頻收發器 8 3 :射頻前端電路 84 :天線 -20-Kilt LDO ~ ^525 τ _ ^525 ~ ^523 "~~R2~ j ! ^522 ~ ^523 _ ^523 —"R4 —_ R3 From (6)~(9), I and V 5 2 are eliminated 3, get the LDO output voltage expression V = (1 + f 丨 and 4 + and 1 and 3 - ψ __ ^ 3 γ (1 〇). '"-wo, r2r4 + r3W3k_ R2W4 + R2Rivm uo; will (5) Enter (1 0 ) to get the expression (4). The curve of the LDO output voltage 524 with the system power supply voltage Vbat 520 is shown in Figure 6. When the system power supply (battery) voltage drops, increase the LDO output voltage 5 24, thereby increasing the output power of the driver 503 and the driver 504, so that the input power 526 of the output amplifier of the power amplifier 502 increases as the system power supply voltage Vbat 5 20 decreases, and the power amplifier is driven by -16-201233082 The power compensation effect is realized on the whole stage and the output stage. The relationship between the output power of the RF power amplifier and the Vramp after the voltage compensation technique is shown in Figure 7. When the system power supply voltage changes from 4.2V to 3.5V, the output is The output power of the amplifier 506 remains constant. Figure 8 shows an embodiment of the invention. A schematic diagram of a mobile terminal structure, a mobile terminal baseband control chip 810, a radio frequency transceiver 82, a radio frequency front end circuit 83, and an antenna 84. The baseband control chip 81 is used to synthesize a baseband signal to be transmitted, or to perform a received baseband signal. Decoding: The RF transceiver 8 2 processes the baseband signal transmitted from the baseband control chip 81 to generate a radio frequency signal, and transmits the generated radio frequency signal to the radio frequency front end circuit 83 or to the radio frequency front end circuit 83. The RF signal is processed to generate a baseband signal, and the generated baseband signal is sent to the baseband control chip 81; the RF front end chip 83 is used to perform processing such as power amplification on the RF signal transmitted from the RF transceiver 82. Or receiving the signal and processing the received signal to the RF transceiver 8 2; the antenna 84 is connected to the RF front end circuit 83 for receiving signals from the outside or transmitting signals transmitted from the RF front end circuit. In the case of signal transmission, the baseband control chip 81 compiles the information to be transmitted into a baseband code (baseband signal). And transmitting it to the radio frequency transceiver 82, the radio frequency transceiver 82 processes the baseband signal to generate a radio frequency signal, and transmits the radio frequency signal to the radio frequency front end circuit 83, and the radio frequency front end circuit 83 transmits the radio frequency front end circuit 83 from the radio frequency transceiver 82. The RF signal is amplified by power and transmitted outward through the antenna 84. When receiving the signal, the RF front end circuit 83 transmits the RF signal received through the antenna 84 to the RF signal transceiver. 8 2 -17- 201233082 'RF Signal Transceiver 8 2 converts the radio frequency signal received from the radio frequency front end circuit 83 into a baseband signal, and transmits the baseband signal to the baseband control chip 8 1 ' Finally, the baseband control chip 6 1 decomposes the baseband signal transmitted from the radio frequency transceiver Alternatively, the information to be transmitted or the received information may include audio information, address information (such as a mobile phone number or website address), text information (such as short message text or website text), picture information, and the like. The main components of the baseband control chip are a processor (such as DSP, ARM, etc.) and a memory (such as SRAM, Flash, etc.). Alternatively, the baseband control wafer is implemented from a single wafer. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are intended to provide a further understanding of the invention 1 is a schematic diagram of a working mode of a power amplifying circuit; FIG. 2 is a schematic structural view of a front end circuit of a radio frequency in the prior art; FIG. 3 is a voltage output curve of a power amplifying circuit in the prior art; and FIG. 4 is a working circuit of a power amplifying circuit in the prior art. FIG. 5 is a schematic structural diagram of a radio frequency front end circuit according to an embodiment of the present invention; FIG. 6 is an LDO output curve after power supply voltage compensation according to an embodiment of the present invention; -18-201233082 FIG. The embodiment of the invention provides an output power curve after power supply voltage compensation; FIG. 8 is a mobile terminal provided by an embodiment of the present invention; and FIGS. 9a to 9c are L-type, T-type and Pi-type matching circuits. [Description of main component symbols] 2 Ο 1 : Power control circuit 202 : Power amplifier circuit 203 : Power supply voltage Vbat 204 : Resistor 205 : Resistor 206 : Output node 2 1 1 : Amplifier 2 1 2 : Noisy pole 2 1 0 : Bias Circuit 2 0 7 : Driver 2 0 8 : Driver 2 09 : Driver 5 0 1 : Power Amplifying Circuit 502 : Power Amplifying Circuit · 5 03 : Driver 5 04 : Driver 5 0 5 : Matching Circuit 506 : Output Amplifier -19- 201233082 508: PMOS transistor 516: amplifier 5 1 7 : bandgap reference source circuit 5 1 8 : second amplifier 5 1 9 : baseband control signal 5 2 0 : system power supply 5 2 2 : output node 5 2 3 : node 5 2 4 : Output voltage 5 2 5 : Node 5 2 6 : Input power 5 0 7 : Bias circuit 8 1 : Baseband control chip 82 : RF transceiver 8 3 : RF front-end circuit 84 : Antenna -20-