200418262 玖、發明說明（1 ) 【發明所屬之技術領域】 本發明是有關於-種功率放大電路，特別是指—種電路 構架簡單且可有效減少射頻功率放大失真之低失真功率放大 電路。 5【先前技術】 在目前的行動通訊系統中，為了讓手機録地台能廣泛 隸㈣㈣的頻道’手機或基地台在各個頻道中所發射的 射頻訊號必須被精確地放大，但事實上當射頻訊號通過一高 功率放大器時，由於高功率放大器中的元件會受到溫度變化 1〇 、製程誤差、設定頻率和其他原因的影響，而使得放大之射 頻訊號的振幅和相位產生非線性失真，其中振幅失真和相位 失真通常分別被稱為AM-AM轉換效應和AM-PM轉換效應。 且由於手機或基地台等通訊設備，其針對特定頻段所發射的 功率必須滿足規範所定的要求，因此，為了讓射頻訊號源的 15輸出功率維持在一特定範圍（即可容忍的失真範圍）内，通常會 採用一回授補償電路來進行校正。而習知上常用的回授補償 技術主要有美國專利第6275685B1號所揭露之pre_Dist〇rti〇n( 預失真）電路、美國專利第6138〇42號所揭露之 順向饋入）電路以及美國專利第5724〇〇3A號所揭露之出代以卜 eedback(直接回授）電路等’其中’ pre-dist〇rti〇11電路和Fee(j forward電路必須具備兩個精細設定的對照表（L〇〇k-up table )’分別做為振幅補償的參考值及相位補償的參考值，而且必 々同時建構一振幅回授迴路及一相位回授迴路，以分別產生 振幅回授訊號及一相位回授訊號，並擷取原射頻訊號來分 200418262 玖、發明說明（2 ) 別與振幅回授訊號及相位回授訊銬 tL观比較，以分別取得正確的 誤差訊號來補償增^及相位，而克服㈣減在放大過程中 造成的信號失真，但如此的架構不但控制線路複雜而且成本 昂貴。至於Directly feedback方式雖然電路簡單但由於是 以類比方式進行補償，其控制增益固定無法彈性調整’使得 可用頻寬受到限制。 【發明内容】 因此，本發明之目的，在於提供一種電路架構簡單，可 彈性調整放大增益並且有效降低射頻功率放大失真之低失真 功率放大電路。 於是，本發明之低失真功率放大電路，用以線性放大一 射頻訊號，該低失真功率放大電路包括一前置放大器、一功 率放大器、一耦合電路、一類比補償電路、一數位補償電路 及一運算電路。該前置放大器接收並前置放大該射頻訊號， 以輸出一第一射頻訊號。該功率放大器接收並放大該第一射 頻訊號，以輸出一第二射頻訊號。該耦合電路用以偵測該第 二射頻訊號以產生一回授訊號。該類比補償電路與該轉合電 路連接，以根據該回授訊號產生一第一補償訊號。該數位補 償電路與該耦合電路連接，以根據該回授訊號產生一第二補 償訊號。該運算電路，與該類比補償電路、該數位補償電路 及該前置放大器連接，以根據該第一補償訊號及第二補償訊 號產生一增益控制訊號控制該前置放大器改變其放大增益。 藉此，達到簡化電路架構並可彈性調整放大增益而有效減少 射頻功率放大失真的功效。 200418262 玖、發明說明（3 ) 5 10 再者’本發明之輸出增益控制電路，用以調整輸入一功 率放大器之-射頻訊號的輪出增^，以改善該功率放大器之 非線性失真，該輸出增益控制電路包括—前置放大器、一麵 合電路、-類比補償電路、一數位補償電路及一運算電路。 該則置放大器連接在該射頻訊號與該功率放大器之間，用以 接收並前置放大該射頻訊號，以輸出—第—射頻訊號至該功 率放大器進行放大，使輸出一第二射頻訊號。該_路用 以偵測該第二射頻訊號並產生—回授訊號。該類比補償電路 與該麵合電路連接，以根據該回授訊號產生一第—補償訊號 。該數位補償電路與㈣合電路連接，以根據該回授訊號產 生一第二補償訊號，該運算電路與該類比補償電路、該數位 補償電路及該前置放大器連接’以根據該第—補償訊號及第 二補償訊號產生益控制訊號控制㈣置放A器改變其放 大增益。 ’ 此外，本發明之輸出增益控制電路，用以控制一前置放 大器之放大增益，該前置放大器接收並前置放大一射頻訊號 ，以產生一第一射頻訊號給與該前置放大器連接之一功率放 大器，使進行放大並輸出一第二射頻訊號；該輸出增益控制 電路包括一耦合電路、一類比補償電路、一數位補償電路及 一運算電路。該耦合電路用以偵測該第二射頻訊號並產生一 回授訊號。該類比補償電路與該耦合電路連接，以根據該回 授訊號產生一第一補償訊號。該數位補償電路與該耦合電路 連接，以根據該回授訊號產生一第二補償訊號。該運算電路 與該類比補償電路、該數位補償電路及該前置放大器連接， 200418262 玖、發明說明（4) 以根據該第一補償訊號及第二補償訊號產生一增益控制訊號 控制該前置放大器改變其放大增益。 【實施方式】 本發明之前述以及其他技術内容、特點與功效，在以下 5配合參考圖式之一較佳實施例的詳細說明中，將可清楚的明 白。 參閱第一圖所示，是本發明低失真功率放大電路i的一 較佳實施例’其目的在於線性放大_射頻訊號RF，低失真功 率放大電路1包括一前置放大器10、一功率放大器n、一耦 1〇合電路12、一類比補償電路13、一數位補償電路14及一運 鼻電路15。 前置放大器10是一可變增益前置放大器，其與射頻訊號 RF連接並對射頻訊號10進行前置放大並輸出一第一射頻訊 號 RF，。 15 功率放大器11與前置放大器10的輸出端連接，其具有 一固定增益，其接收第一射頻訊號RF，並將其放大一定倍率 後，輸出一第二射頻訊號RF”至一天線17，使將第二射頻訊 號RF”發射出去。 搞合電路12包括依序串接之一輕合迴路ι21、一衰減器 20 I22及一嵌位電路123。耦合迴路121靠近天線17，以感應的 方式偵測功率放大器11輸出之第二射頻訊號RF，，並產生一回 授訊號（為一電壓值）A經過衰減器122適當衰減至本電路i可 接受的範圍後，藉由嵌位電路123將衰減後之回授訊號A，維 持在一基本準位，使當在頻段切換期間產生之回授訊號為零 200418262 玖、發明說明（5 ) 時’仍存在一電壓準位，而能減少上述AM-AM及AM-PM效 應。 類比補償電路13是一除法器，其與耦合電路丨2之嵌位 電路123連接，以對該回授訊號A，進行類比除法運算，而適 5 當調整回授訊號A’之大小並產生一第一補償訊號131。 數位補领電路14包括一 A/D轉換器141、一處理器142 、一對照表143及一 D/A轉換器144。A/D轉換器141與耦 合電路12之嵌位電路123連接，其對回授訊號A，進行數位化 後送入處理器142中。對照表143中預設有複數增益補償參 1〇 考值，其是在25°C下，量測在各規範頻段中輸出不同功率的 射頻訊號而設定之基準值，例如基地台可輸出2〇〇mw、 400mw及800mw等三種輸出功率，則在某一頻段中輸出 200mw輸出功率的情況下，在對照表143中，即具有一對應 於回授訊號A，之增益補償參考值。所以，當處理器142收到 15 數位化之回授訊號A”時，即根據回授訊號A”從對照表143 中擷取一參考值R與回授訊號A”進行減法運算（A，，_R)，以 產生一第二補償訊號145經D/A轉換器144轉換後輸出。當 然，第二補償訊號145亦可視情況，由處理器Μ]本身設定 -合適的直流（DC)項B(其用以設定下述之增益控制信號的基 20 本準位），加上回授訊號A”再減去參考值R (亦即b+a，，_r) 而獲得。 運算電路15包括一直流偏壓產生器151及一運算放大器 152。直流偏壓產生器151可供設定—直流偏壓，運算 放大器152的輸出端連接前置放大器1〇，且其正輪入端⑴與 9 200418262 玖、發明說明（6 ) 直流偏壓產生器151連接，接受直流偏壓產生器15丨提供之 直流偏壓Vbias，以提供一固定的增益控制訊號給前置放大器 1 〇 ’而其負輸入端㈠分別連接類比補償電路13及數位補償電 路14，以將第一及第二補償訊號Π1、145與直流偏壓vbias 5 合成產生一變動的增益控制訊號153輸出控制前置放大器10 〇 由於實際上，功率放大器11是經由前置放大器1〇連接 射頻訊號RF，而且前置放大器10根據由回授訊號A”產生之 增盈控制訊號153適時改變其放大增益，而預先對射頻訊號 10 RF進行前置放大的作用，將改善功率放大器11的非線性失 真現象。因此，由上述負回授電路（即低失真功率放大電路〇 可知’偵測第二射頻訊號RF”而獲得之回授訊號a，，藉由類 比補償電路13(具有即時反應特性）所產生之第一補償訊號131 回授控制前置放大器1〇，可對功率放大器u做即時的相位補 15 償，因而可拉高功率放大器11的輸出頻寬和相位邊界（phase margin)。而回授訊號a’經由數位補償電路丨4參照對照表j 43 產生之第二補償訊號145，則可彈性調整前置放大器1〇的放 大增益，以補償功率放大器丨丨的非線性失真部分，使功率放 大器11可適用在規範的頻段（1850.1MHZ〜1990MHZ)内。且如 20 第二圖及第三圖所示，是本案在1990MHZ頻段下，環境溫度 為25C且輸出功率為800mw時（在此環境下設定對照表143 )，相較於沒有回授的功率放大電路，在不同溫度下，輸出功 率的衰減幅度（誤差率）。由第二圖中可知，沒有回授的功率放 大電路在環境溫度偏離25°C時，即產生極大的功率誤差，尤 10 200418262 玫、發明說明（7 ) 其在環境溫度低於0它時誤差更大。反觀本發明之功率放大電 路1，當環境溫度0°c〜50°c之間時，其功率誤差率可說相當 小，而即使環境溫度是在〜1〇〇c之間，其功率誤差率也遠 較沒有回授的功率放大器來得低，顯見本發明之功率放大電 路1具有良好的功率放大效果。 綜上所述，本發明低失真功率放大電路i藉由結合類比 補償電路13及數位補償電路14，除了利用閉迴路會降低系統 增益的特性而增加可用頻寬並提高射頻輸出的精細度外，更 利用類比補償電路13做即時相位補償而提高系統之相位邊界 ，並利用數位補償電路14彈性調整前置放大器1〇的放大增 益，使得本發明的電路架構如同前述Directly feedback電路 般簡單，且又具有數位調整增益補償值的功能，而能夠應用 在行動通訊所規範的頻道範圍，確實達到簡化電路架構並且 有效降低射頻功率放大失真的功效。 准以上所述者，僅為本發明之較佳實施例而已，當不能 以此限疋本發明實施之範圍，即大凡依本發明申請專利範圍 及發明說明書内容所作之簡單的等效變化與修飾，皆應仍屬 本發明專利涵蓋之範圍内。 【圖式簡單說明】 第一圖是本發明低失真射頻功率放大器的一較佳實施例 之電路方塊圖； 弟n®表，顯示本發明與無回授之功率放大電路 相較（在胸MHZ頻段下，環境溫度4饥且輸出功率為 _層日夺），纟不同冑境溫度下的衰減幅度（功率誤差率）示意 200418262 玖、發明說明（8 ) 圖；及 第三圖是一比較表，顯示本發明與無回授之功率放大電 路在1990MHZ頻段下，相對於環境溫度變化的功率誤差率。200418262 发明. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a kind of power amplifier circuit, in particular to a kind of circuit, a low distortion power amplifier circuit with a simple structure and which can effectively reduce RF power amplifier distortion. 5 [Previous technology] In the current mobile communication system, in order to allow mobile phones to record channels that can be widely controlled, the radio frequency signals transmitted by mobile phones or base stations must be accurately amplified in each channel. In fact, when radio frequency signals When passing through a high-power amplifier, the components in the high-power amplifier will be affected by temperature changes of 10, process errors, set frequencies, and other reasons, so that the amplitude and phase of the amplified RF signal will have non-linear distortion, among which amplitude distortion And phase distortion are commonly referred to as AM-AM conversion effect and AM-PM conversion effect, respectively. And because communication equipment such as mobile phones or base stations, the power transmitted by it for a specific frequency band must meet the requirements set by the specification. Therefore, in order to maintain the 15 output power of the RF signal source within a specific range (that is, a tolerable distortion range) Normally, a feedback compensation circuit is used for correction. The conventionally used feedback compensation technology is mainly the pre_Distorn (pre-distortion) circuit disclosed in US Patent No. 6275685B1, the forward feed-in circuit disclosed in US Patent No. 6138040, and the US patent The disclosure disclosed in No. 5724〇03A is replaced by Eedback (direct feedback) circuits, etc. 'Among them' pre-distorti11 circuits and Fee (j forward circuits must have two fine-set comparison tables (L. 〇k-up table) 'as the reference value for amplitude compensation and the reference value for phase compensation, respectively, and an amplitude feedback loop and a phase feedback loop must be constructed at the same time to generate an amplitude feedback signal and a phase feedback, respectively. The signal is obtained and the original RF signal is extracted to distinguish 200418262. (2) The invention is not compared with the amplitude feedback signal and the phase feedback signal tL, to obtain the correct error signal to compensate the gain and phase, respectively. It overcomes the signal distortion caused by the reduction during the amplification process, but such an architecture not only has complicated control circuits but is also expensive. As for the Directly feedback method, although the circuit is simple, it is based on an analog method. Compensation, its control gain is fixed and cannot be adjusted elastically, so that the available bandwidth is limited. [Summary of the invention] Therefore, the object of the present invention is to provide a simple circuit architecture that can flexibly adjust the amplification gain and effectively reduce the low distortion of RF power amplification distortion. Power amplifier circuit. Therefore, the low distortion power amplifier circuit of the present invention is used to linearly amplify a radio frequency signal. The low distortion power amplifier circuit includes a preamplifier, a power amplifier, a coupling circuit, an analog compensation circuit, and a digital signal. A compensation circuit and an arithmetic circuit. The preamplifier receives and preamplifies the radio frequency signal to output a first radio frequency signal. The power amplifier receives and amplifies the first radio frequency signal to output a second radio frequency signal. The coupling The circuit is used for detecting the second radio frequency signal to generate a feedback signal. The analog compensation circuit is connected to the turning circuit to generate a first compensation signal according to the feedback signal. The digital compensation circuit is connected to the coupling circuit. To generate a second compensation signal based on the feedback signal. An arithmetic circuit is connected to the analog compensation circuit, the digital compensation circuit and the preamplifier to generate a gain control signal to control the preamplifier to change its amplification gain according to the first compensation signal and the second compensation signal. Achieve the effect of simplifying the circuit structure and flexibly adjusting the amplification gain to effectively reduce the distortion of RF power amplification. 200418262 玖 、 Explanation (3) 5 10 Furthermore, the output gain control circuit of the present invention is used to adjust the input of a power amplifier- The RF signal is increased and increased to improve the non-linear distortion of the power amplifier. The output gain control circuit includes a preamplifier, a face-to-face circuit, an analog compensation circuit, a digital compensation circuit, and an operation circuit. The amplifier is connected between the radio frequency signal and the power amplifier, and is used for receiving and pre-amplifying the radio frequency signal, and outputting the first radio frequency signal to the power amplifier for amplification to output a second radio frequency signal. The _ road is used to detect the second radio frequency signal and generate a feedback signal. The analog compensation circuit is connected to the surface-bonding circuit to generate a first-compensation signal according to the feedback signal. The digital compensation circuit is connected to the coupling circuit to generate a second compensation signal according to the feedback signal. The arithmetic circuit is connected to the analog compensation circuit, the digital compensation circuit and the preamplifier to connect the compensation signal according to the first compensation signal. And the second compensation signal generates a gain control signal to control the A-positioner to change its amplification gain. In addition, the output gain control circuit of the present invention is used to control the amplification gain of a preamplifier. The preamplifier receives and preamplifies a radio frequency signal to generate a first radio frequency signal to the preamplifier connected to the preamplifier. A power amplifier is used to amplify and output a second radio frequency signal. The output gain control circuit includes a coupling circuit, an analog compensation circuit, a digital compensation circuit and an operation circuit. The coupling circuit is used to detect the second RF signal and generate a feedback signal. The analog compensation circuit is connected to the coupling circuit to generate a first compensation signal according to the feedback signal. The digital compensation circuit is connected to the coupling circuit to generate a second compensation signal according to the feedback signal. The arithmetic circuit is connected to the analog compensation circuit, the digital compensation circuit and the preamplifier. 200418262 玖, description of the invention (4) A gain control signal is generated according to the first compensation signal and the second compensation signal to control the preamplifier. Change its amplification gain. [Embodiment] The foregoing and other technical contents, features, and effects of the present invention will be made clear in the following detailed description of a preferred embodiment with reference to the accompanying drawings. Referring to the first figure, it is a preferred embodiment of the low distortion power amplifier circuit i according to the present invention. Its purpose is to linearly amplify the RF signal. The low distortion power amplifier circuit 1 includes a preamplifier 10 and a power amplifier n. A coupling circuit 10, an analog compensation circuit 13, a digital compensation circuit 14, and a nose circuit 15. The preamplifier 10 is a variable gain preamplifier which is connected to a radio frequency signal RF and preamplifies the radio frequency signal 10 and outputs a first radio frequency signal RF. 15 The power amplifier 11 is connected to the output of the preamplifier 10 and has a fixed gain. It receives the first radio frequency signal RF and amplifies it at a certain magnification, and outputs a second radio frequency signal RF "to an antenna 17, so that The second radio frequency signal RF "is transmitted. The coupling circuit 12 includes a light-closing circuit ι21, an attenuator 20 I22, and an embedded circuit 123 connected in series. The coupling circuit 121 is close to the antenna 17, and detects the second radio frequency signal RF output by the power amplifier 11 in an inductive manner, and generates a feedback signal (which is a voltage value). After the range is reduced, the attenuated feedback signal A is maintained at a basic level by the embedding circuit 123, so that when the feedback signal generated during the frequency band switching is zero 200418262 发明, invention description (5) 'still There is a voltage level that can reduce the AM-AM and AM-PM effects described above. The analog compensation circuit 13 is a divider, which is connected to the embedded circuit 123 of the coupling circuit 2 to perform an analog division operation on the feedback signal A, and appropriately adjusts the size of the feedback signal A 'and generates a First compensation signal 131. The digital compensation circuit 14 includes an A / D converter 141, a processor 142, a look-up table 143, and a D / A converter 144. The A / D converter 141 is connected to the embedding circuit 123 of the coupling circuit 12, which digitizes the feedback signal A and sends it to the processor 142. The reference value 143 is preset in the comparison table 143. It is a reference value set at 25 ° C to measure RF signals with different power output in each standard frequency band. For example, the base station can output 2〇 〇mw, 400mw and 800mw output power, in the case of 200mw output power in a certain frequency band, in the comparison table 143, there is a gain compensation reference value corresponding to the feedback signal A. Therefore, when the processor 142 receives the 15 digitized feedback signal A ", it extracts a reference value R and the feedback signal A" from the comparison table 143 according to the feedback signal A "and performs a subtraction operation (A ,, _R) to generate a second compensation signal 145 after conversion by the D / A converter 144. Of course, the second compensation signal 145 may also be set by the processor M] itself according to the situation-a suitable direct current (DC) term B ( It is used to set the base 20 level of the gain control signal described below, and it is obtained by adding the feedback signal A "and then subtracting the reference value R (ie, b + a, _r). The operation circuit 15 includes a DC bias generator 151 and an operation amplifier 152. The DC bias generator 151 can be set—DC bias, the output of the operational amplifier 152 is connected to the preamplifier 10, and its positive wheel input terminal (9 and 200418262), invention description (6) DC bias generator 151 Connect and accept the DC bias Vbias provided by the DC bias generator 15 丨 to provide a fixed gain control signal to the preamplifier 10 ′ and its negative input terminal is connected to the analog compensation circuit 13 and the digital compensation circuit 14, respectively. The first and second compensation signals Π1, 145 and the DC bias voltage vbias 5 are combined to produce a variable gain control signal 153. The output controls the preamplifier 10. In fact, the power amplifier 11 is connected to the RF via the preamplifier 10. Signal RF, and the preamplifier 10 changes its amplification gain in time according to the gain control signal 153 generated by the feedback signal A ”, and pre-amplifying the RF signal 10 RF in advance will improve the non-linearity of the power amplifier 11 Distortion phenomenon. Therefore, the feedback signal obtained by the above-mentioned negative feedback circuit (that is, the low distortion power amplifier circuit 〇 can detect the 'detection of the second radio frequency signal RF'). No. a, through the first compensation signal 131 generated by the analog compensation circuit 13 (with real-time response characteristics) to feedback control the preamplifier 10, it can make real-time phase compensation 15 to the power amplifier u, so it can be pulled up The output bandwidth and phase margin of the power amplifier 11. The second compensation signal 145 generated by the feedback signal a ′ through the digital compensation circuit 丨 4 with reference to the reference table j 43 can be used to flexibly adjust the preamplifier 10's Amplify the gain to compensate for the non-linear distortion of the power amplifier, so that the power amplifier 11 can be applied in the standard frequency band (1850.1MHZ ~ 1990MHZ). And as shown in the second and third figures of this figure, this case is at 1990MHZ In the frequency band, when the ambient temperature is 25C and the output power is 800mw (set the comparison table 143 in this environment), compared with the power amplifier circuit without feedback, the output power attenuation range (error rate) at different temperatures. As can be seen from the second figure, a power amplifier circuit without feedback generates a large power error when the ambient temperature deviates from 25 ° C, especially 10 200418262, the description of the invention (7) When the ambient temperature is lower than 0, the error is greater. In contrast, the power amplifier circuit 1 of the present invention, when the ambient temperature is between 0 ° c ~ 50 ° c, its power error rate can be said to be quite small, and even if the ambient temperature is between ~ Between 100c, its power error rate is also much lower than that of a power amplifier without feedback. It is obvious that the power amplifier circuit 1 of the present invention has a good power amplification effect. In summary, the low distortion power amplifier circuit of the present invention By combining the analog compensation circuit 13 and the digital compensation circuit 14, in addition to using the closed-loop will reduce the system gain characteristics to increase the available bandwidth and improve the precision of the RF output, the analog compensation circuit 13 is used for real-time phase compensation to improve The phase boundary of the system, and the digital gain compensation circuit 14 is used to elastically adjust the amplification gain of the preamplifier 10, so that the circuit architecture of the present invention is as simple as the aforementioned Directly feedback circuit, and has the function of digitally adjusting the gain compensation value, and can be applied. In the range of channels regulated by mobile communications, the function of simplifying the circuit structure and effectively reducing the distortion of RF power amplification is indeed achieved. . Those mentioned above are only the preferred embodiments of the present invention, and should not be used to limit the scope of the present invention, that is, simple equivalent changes and modifications made in accordance with the scope of the patent application and the contents of the invention specification. , All should still fall within the scope of the invention patent. [Brief description of the figure] The first figure is a circuit block diagram of a preferred embodiment of the low-distortion RF power amplifier of the present invention; the n® table shows that the present invention is compared with a power amplifier circuit without feedback (on the chest MHZ) In the frequency band, the ambient temperature is 4 h and the output power is _ layer daily gain). The attenuation range (power error rate) at different ambient temperatures is shown in 200418262. Figure of the Invention (8); and the third figure is a comparison table. , Shows the power error rate of the present invention and the power amplifier circuit without feedback in the 1990MHZ frequency band relative to the ambient temperature change.
12 200418262 玖、發明說明（9 ) 【圖式之主要元件代表符號簡單說明】 1 低失真功率放大電路 10前置放大器 12耦合電路 14數位補償電路 17天線 111輸入端 121耦合迴路 123嵌位電路 141 A/D轉換器 143對照表 145第二補償訊號 152運算放大器 A回授訊號 A”數位化之回授訊號 RF第一射頻訊號 11功率放大器 13類比補償電路 15運算電路 112輸出端 122衰減器 131第一補償訊號 142處理器 144 D/A轉換器 151直流偏壓產生器 153增益控制訊號 A’衰減後之回授訊號 RF射頻訊號 RF”第二射頻訊號12 200418262 发明. Description of the invention (9) [Simplified description of the main components of the diagram] 1 Low distortion power amplifier circuit 10 Pre-amplifier 12 Coupling circuit 14 Digital compensation circuit 17 Antenna 111 Input terminal 121 Coupling circuit 123 Embedded circuit 141 A / D converter 143 comparison table 145 Second compensation signal 152 Operational amplifier A feedback signal A ”Digitized feedback signal RF First radio frequency signal 11 Power amplifier 13 Analog compensation circuit 15 Operation circuit 112 Output end 122 Attenuator 131 First compensation signal 142 Processor 144 D / A converter 151 DC bias generator 153 Gain control signal A 'Attenuated feedback signal RF RF signal RF "Second RF signal
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