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TWI642269B - 補償電路、補償方法及放大電路 - Google Patents

補償電路、補償方法及放大電路 Download PDF

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TWI642269B
TWI642269B TW106128354A TW106128354A TWI642269B TW I642269 B TWI642269 B TW I642269B TW 106128354 A TW106128354 A TW 106128354A TW 106128354 A TW106128354 A TW 106128354A TW I642269 B TWI642269 B TW I642269B
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varactor
amplifier
control circuit
circuit
input
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TW106128354A
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TW201826695A (zh
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林建誠
蔡明達
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聯發科技股份有限公司
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/36—Modulator circuits; Transmitter circuits
    • H04L27/366—Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator
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    • H03D7/165—Multiple-frequency-changing at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature
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Abstract

本發明提供一種補償電路，該補償電路適用於功率放大器，以及，補償電路包括變容二極體、電壓感測器和控制電路。變容二極體耦接於功率放大器的輸入端。電壓感測器用於檢測該功率放大器的輸入訊號的幅度，以產生檢測結果。控制電路耦接于變容二極體和電壓感測器，用於根據檢測結果控制變容二極體的偏置電壓，以調整變容二極體的電容。相應地，本發明還提供了一種補償方法及放大電路。採用本發明，能夠提高功率放大器的線性度。

Description

補償電路、補償方法及放大電路
本發明涉及一種放大器，更特別地，涉及一種適用於功率放大器的補償電路、補償方法及放大電路。
功率放大器(POWER AMPLIFIER，PA)的線性度很大程度上受該功率放大器的輸入電容的影響，以及，當輸入訊號的幅度(AMPLITUDE)增大時，功率放大器的輸出訊號的相位會因輸入電容而改變，這種現象稱為幅度-相位(AM-PM)失真。為了使功率放大器具有穩定的輸出訊號相位，如何設計補償電路來提高功率放大器的線性度係一個重要的課題。
有鑑於此，本發明的目的之一在於提供一種補償電路、補償方法及放大電路，以解決上述問題。
第一方面，本發明提供一種補償電路，該補償電路適用於放大器，以及，該補償電路包括變容二極體、電壓感測器和控制電路。變容二極體耦接於放大器的輸入端。電壓感測器用於檢測放大器的輸入訊號的幅度，以產生檢 測結果。控制電路耦接于變容二極體和電壓感測器，用於根據檢測結果控制變容二極體的偏置電壓，以調整變容二極體的電容。
第二方面，本發明提供一種補償方法，該補償方法適用於放大器，以及，該補償方法包括：提供耦接於放大器的輸入端的變容二極體，其中，變容二極體的電容用作放大器的輸入電容的一部分；檢測放大器的輸入訊號的幅度，以產生檢測結果；以及，控制變容二極體的偏置電壓，以根據檢測結果調整變容二極體的電容。
第三方面，本發明提供一種放大電路，該放大電路包括功率放大器和補償電路，其中，補償電路包括變容二極體、電壓感測器和控制電路。變容二極體耦接於功率放大器的輸入端。電壓感測器用於檢測放大器的輸入訊號的幅度，以產生檢測結果。控制電路耦接于變容二極體和電壓感測器，用於根據檢測結果控制變容二極體的偏置電壓，以調整變容二極體的電容。
採用本發明，通過參考輸入訊號的幅度可以動態地控制變容二極體的偏置電壓，進而通過調整變容二極體的電容來動態地調整功率放大器的輸入電容，從而功率放大器的AM-PM失真和線性度能夠得到大大地改善。
所屬技術領域中具有通常知識者在閱讀附圖所示優選實施例的下述詳細描述之後，可以毫無疑義地理解本發明的這些目的及其它目的。
100、400‧‧‧功率放大器系統
110、410‧‧‧補償電路
120、420‧‧‧功率放大器
112、412、432‧‧‧電壓感測器
114、414、434‧‧‧放大器
116、416、436‧‧‧控制電路
C、C1、C2、C3、C4‧‧‧電容器
VC1、VC2‧‧‧變容二極體
L1‧‧‧電感器
M1、M2、M3、M4‧‧‧電晶體
I1、I2‧‧‧電流源
R1、R2、R3、R4‧‧‧電阻
MP1、MP2、MP3‧‧‧PMOS
MN1、MN2、MN3‧‧‧NMOS
419‧‧‧變壓器
通過閱讀後續的詳細描述和實施例可以更全面地理解本發明，該實施例參照附圖給出，其中：第1圖係根據本發明一實施例示出的功率放大器系統的示意圖；第2圖係根據本發明一實施例示出的控制電路和變容二極體的操作的示意圖；第3圖係根據本發明一實施例示出的電壓感測器的示意圖；第4圖係根據本發明另一實施例示出的功率放大器系統的示意圖。
在下面的詳細描述中，為了說明的目的，闡述了許多具體細節，以便所屬技術領域中具有通常知識者能夠更透徹地理解本發明實施例。然而，顯而易見的係，可以在沒有這些具體細節的情況下實施一個或複數個實施例，不同的實施例可根據需求相結合，而並不應當僅限於附圖所列舉的實施例。
以下描述為本發明實施的較佳實施例。以下實施例僅用來例舉闡釋本發明的技術特徵，並非用來限制本發明的範疇。在通篇說明書及申請專利範圍當中使用了某些詞彙來指稱特定的組件。所屬技術領域中具有通常知識者應可理解，製造商可能會用不同的名詞來稱呼同樣的組件。本說明書及申請專利範圍並不以名稱的差異來作為區別組件的方式，而係以組件在功能上的差異來作為區別的基準。本發明的範圍應當參考后附的申請專利範圍來確定。在以下描述和申請專利範圍當中所提及的術語“包含”和“包括”為開放式用語，故應解釋成“包含，但不限定於...”的意思。此外，術語“耦接”意指間接或直接的電氣連接。因此，若文中描述一個裝置耦接至另一裝置，則代表該裝置可直接電氣連接於該另一裝置，或者透過其它裝置或連接手段間接地電氣連接至該另一裝置。
文中所用術語“基本”或“大致”係指在可接受的範圍內，所屬技術領域 中具有通常知識者能夠解決所要解決的技術問題，基本達到所要達到的技術效果。舉例而言，“大致等於”係指在不影響結果正確性時，所屬技術領域中具有通常知識者能夠接受的與“完全等於”有一定誤差的方式。
本發明提供一種功率放大器的補償電路，其中，補償電路可以通過參考輸入訊號的幅度來動態調整功率放大器的輸入電容。通過使用本發明實施例，可以大大地改善功率放大器的AM-PM失真和線性度，以及，整個電路具有更高的效率。應當說明的係，本發明實施例以差分輸入訊號進行示例說明，但本發明並不限於差分輸入訊號。類似地，本發明也適用於單端輸入訊號的情形，對於本領域技術人員而言，基於該示例很容易獲得單端輸入訊號的實現，因此，關於單端輸入訊號的類似實現此處不再贅述。
第1圖係根據本發明一實施例示出的功率放大器系統100(或可稱之為放大電路)的示意圖。如第1圖所示，功率放大器系統100包括補償電路110和功率放大器120。補償電路110可以包括電壓感測器(voltage sensor)112、放大器114、控制電路116、兩個變容二極體(varactor)VC1和VC2，以及兩個電容器(capacitor)C，其中，變容二極體VC1用作功率放大器120的第一輸入端的輸入電容的一部分，以及，變容二極體VC2用作功率放大器120的第二輸入端的輸入電容的一部分。功率放大器120可以包括電晶體M1-M4、電容器C1和電感器L1。在本實施例中，功率放大器系統110用於接收差分輸入訊號Vp和Vn，以產生差分輸出訊號Vout_p和Vout_n，以及，補償電路110用於補償功率放大器120，特別地，補償電路110用於補償功率放大器120的輸入電容。為便於描述，以下實施例中以檢測差分輸入訊號Vp和Vn的幅度來產生檢測結果為例進行示例說明，但本發明並不限於此。
關於補償電路110的操作，電壓感測器112經由電容器C接收差分輸入訊號Vp和Vn，以檢測差分輸入訊號Vp和Vn的幅度，並產生檢測結果，其中，電容器C用於阻斷直流(Direct Current，DC)電壓。在本實施例中，檢測結果係表示差分輸入訊號Vp和Vn的幅度的電壓訊號，以及，檢測結果經由放大器114輸入至控制電路116，其中，放大器114用於調整(adjust)檢測結果的電壓電平。然後，控制電路116控制/調整變容二極體VC1和VC2的電容(capacitance)，以根據檢測結果補償功率放大器120的輸入電容。在一實施例中，功率放大器的輸入端具有固定的(fixed)直流(DC)電壓(即，變容二極體VC1的上部節點和/或變容二極體VC2的下部節點具有固定的直流電壓)，以及，控制電路116通過設置適當的偏置電壓給變容二極體VC1的下部節點和變容二極體VC2的上部節點(例如，變容二極體VC1和變容二極體VC2之間的連接節點)能夠調整變容二極體VC1和VC2的電容。
在本實施例中，控制電路116包括開關，以及，控制電路116根據檢測結果確定接通或斷開該開關，即該開關根據檢測結果被接通(turned on)或被斷開(turned off)。例如，如第2圖所示，當檢測結果指示差分輸入訊號Vp和Vn具有較大的電力(power)/幅度時，開關被接通，以將變容二極體VC1連接到變容二極體VC2，以及，控制電路116能夠設置偏置電壓Vb給變容二極體VC1和VC2中間的連接節點，以控制/調整變容二極體VC1和VC2的電容。當檢測結果指示差分輸入訊號Vp和Vn具有較低的電力/幅度時，則不需要補償功率放大器120的輸入電容，開關係斷開的，以及，變容二極體VC1的下部節點和變容二極體VC2的上部節點處於浮動狀態(floating state)。此外，在一實施例中，當檢測結果指示差分輸入訊號Vp和Vn的幅度增大時，控制電路116控制變容二極體VC1和VC2 的偏置電壓，以增大變容二極體VC1和VC2的電容；以及，當檢測結果指示差分輸入訊號Vp和Vn的幅度減小(decrease)時，控制電路116控制變容二極體VC1和VC2的偏置電壓，以減小變容二極體VC1和VC2的電容。因此，在本發明實施例中，控制電路116根據檢測結果動態地調整變容二極體VC1和VC2的偏置電壓，進而動態地調整變容二極體VC1和VC2的電容，以實現調整功率放大器的輸入電容的目的。
通過使用上述補償方法，能夠根據差分輸入訊號Vp和Vn的幅度動態地補償功率放大器120的輸入電容，因此，差分輸出訊號Vout_p和Vout_n的相位將更加穩定，以及，AM-PM失真能夠得到有效地改善，即便差分輸入訊號Vp和Vn的幅度頻繁變化也將如此。
第3圖係根據本發明一實施例示出的電壓感測器112的示意圖。如第3圖所示，電壓感測器112可以包括三個P型金屬氧化物半導體(P-type metal-oxide semiconductors，PMOS)MP1-MP3、三個N型金屬氧化物半導體(N-type metal-oxide semiconductors，NMOS)MN1-MN3、兩個電流源I1-I2、三個電阻R1-R3和兩個電容器C2-C3。第3圖所示的實施例係峰值檢波器(peak detector)，其分別將差分輸入訊號Vp和Vn與參考電壓Vref進行比較，以檢測差分輸入訊號Vp和Vn的擺幅(swing amplitude)或峰值(peak value)，以及，檢測結果的電壓電平被用來表示差分輸入訊號Vp和Vn的擺幅或峰值。
第4圖係根據本發明另一實施例示出的功率放大器系統400的示意圖，但本發明並不限於所示出的示例性實施例。例如，在基於第4圖的變型實施例中，可以省略電壓感測器432、連接至電壓感測器432的兩個電容C以及放大器 434，以及，放大器414的輸出端還耦接於控制電路436，具體地，本發明實施例不做任何限制。如第4圖所示，功率放大器系統100包括補償電路410和功率放大器420。補償電路410可以包括兩個電壓感測器412和432、兩個放大器414和434、兩個控制電路416和436、兩個變容二極體VC1和VC2、變壓器(transformer)419以及四個電容器C。功率放大器120可以包括電晶體M1-M4、電容器C1和電感器L1。在本實施例中，功率放大器系統410用於經由變壓器419接收差分輸入訊號Vp和Vn，以產生差分輸出訊號Vout_p和Vout_n，換句話說，變壓器419用於將差分輸入訊號Vp和Vn提供給功率放大器420的輸入端，以及，補償電路410用於補償功率放大器的輸入電容420。在第4圖所示實施例中，控制電路436包括電容C4和電阻R4，其中，電容C4和電阻R4表現為分壓器。
關於補償電路410，電壓感測器412、放大器414、控制電路416以及變容二極體VC1和VC2可以被視為相位調製(phase-modulation，PM)補償回路，以使差分輸入訊號Vp和Vn的相位更穩定，以及，電壓感測器432、放大器434、控制電路436和變壓器419可以被視為幅度調製(amplitude-modulation，AM)補償回路，以使功率放大器420以更高的線性度和效率工作。首先，關於相位調製(PM)補償回路的操作，電壓感測器412經由電容器C接收差分輸入訊號Vp和Vn，以檢測差分輸入訊號Vp和Vn的幅度，並產生檢測結果，其中，電容器C用於阻斷直流(DC)電壓。在本實施例中，檢測結果係表示差分輸入訊號Vp和Vn的幅度的電壓訊號，以及，檢測結果經由放大器414輸入至控制電路416，放大器414用於調整檢測結果的電壓電平。然後，控制電路416根據檢測結果來控制/調整變容二極體VC1和VC2的電容，以補償功率放大器420的輸入電容。
在本實施例中，控制電路416包括開關，以及，控制電路416根據檢 測結果確定接通或斷開該開關，即開關根據檢測結果被接通或斷開。例如，當檢測結果指示差分輸入訊號Vp和Vn具有較大的電力/幅度時，開關被接通，以將變容二極體VC1連接至變容二極體VC2(例如，第2圖所示的實施例)，以及，控制電路416能夠設置適當的偏置電壓給變容二極體VC1和VC2之間的連接節點，以控制/調整變容二極體VC1和VC2的電容。當檢測結果指示差分輸入訊號Vp和Vn具有較低的電力/幅度時，則不需要補償功率放大器420的輸入電容，開關係斷開的，以及，變容二極體VC1的下部節點和變容二極體VC2的上部節點處於浮動狀態。此外，在一實施例中，當檢測結果指示差分輸入訊號Vp和Vn的幅度增大時，控制電路416控制變容二極體VC1和VC2的偏置電壓，以增大變容二極體VC1和VC2的電容；以及，當檢測結果指示差分輸入訊號Vp和Vn的幅度減小時，控制電路416控制變容二極體VC1和VC2的偏置電壓，以減小變容二極體VC1和VC2的電容。因此，在本發明實施例中，控制電路416根據檢測結果動態地調整變容二極體VC1和VC2的偏置電壓，進而動態地調整變容二極體VC1和VC2的電容，以實現調整功率放大器的輸入電容的目的。
通過使用上述相位調製(PM)補償方法，能夠根據輸入差分訊號Vp和Vn的幅度動態地補償功率放大器420的輸入電容，因此，差分輸出訊號Vout_p和Vout_n的相位將係更穩定的，以及，AM-PM失真可以得到有效地改善，即便輸入差分訊號Vp和Vn的幅度頻繁變化也將如此。
關於幅度調製(AM)補償回路的操作，電壓感測器432經由電容器C接收差分輸入訊號Vp和Vn，以檢測差分輸入訊號Vp和Vn的幅度，並產生檢測結果，其中，電容器C用於阻斷直流電壓。在本實施例中，檢測結果係表示差分輸入訊號Vp和Vn的幅度的電壓訊號，以及，檢測結果經由放大器434輸入至控制 電路436，放大器434用於調整檢測結果的電壓電平。然後，控制電路436內的電阻器R4和電容器C4用作分壓器，以根據檢測結果提供偏置電壓至變壓器419的中心抽頭。
在本實施例中，當差分輸入訊號Vp和Vn的幅度增大時，控制電路436將較高的偏置電壓施加到變壓器419的中心抽頭，使得功率放大器420的輸入端具有較高的直流(DC)電壓。在本發明實施例中，變壓器419用於變換阻抗，輸入至功率放大器420的直流電壓受控制電路436的控制，因此，即使當差分輸入訊號Vp和Vn具有大的擺幅時，功率放大器420的線性度也不會惡化。此外，當差分輸入訊號Vp和Vn的幅度減小時，控制電路436將較低的偏置電壓施加到變壓器419的中心抽頭，使得功率放大器420的輸入端具有較低的直流(DC)電壓，因此，可以改善功率放大器420的功耗。
通過使用上述幅度調製(AM)補償方法，能夠根據輸入差分訊號Vp和Vn的幅度動態地調整功率放大器420的輸入端的直流電壓，因此，功率放大器420可以具有更好的線性度和適當的功耗。
電壓感測器412和432可以由第3圖所示的實施例來實現，但這並不係對本發明的限制。
簡而言之，在本發明的補償電路中，補償電路通過參考輸入訊號的幅度能夠動態地調整功率放大器的輸入電容，以及，AM-PM失真和功率放大器的線性度能夠得到大大地改善。此外，補償電路通過參考輸入訊號的幅度還能夠動態地調整功率放大器的輸入端的直流電壓，以使得功率放大器具有更好的 線性度和適當的功耗。
雖然已經對本發明實施例及其優點進行了詳細說明，但應當理解的係，在不脫離本發明的精神以及申請專利範圍所定義的範圍內，可以對本發明進行各種改變、替換和變更，例如，可以通過結合不同實施例的若干部分來得出新的實施例。所描述的實施例在所有方面僅用於說明的目的而並非用於限制本發明。本發明的保護範圍當視所附的申請專利範圍所界定者為准。所屬技術領域中具有通常知識者皆在不脫離本發明之精神以及範圍內做些許更動與潤飾。
以上所述僅為本發明之較佳實施例，凡依本發明申請專利範圍所做之均等變化與修飾，皆應屬本發明之涵蓋範圍。

Claims (10)

  1. 一種補償電路，適用於放大器，其中，該補償電路包括：第一變容二極體，耦接於該放大器的第一輸入端；電壓感測器，用於檢測該放大器的輸入訊號的幅度，以產生檢測結果；以及控制電路，耦接於該第一變容二極體和該電壓感測器，用於根據該檢測結果控制該第一變容二極體的偏置電壓，以調整該第一變容二極體的電容；其中，該補償電路還包括：第二變容二極體，耦接於該放大器的第二輸入端；其中，該控制電路根據該檢測結果還控制該第二變容二極體的偏置電壓，以調整該第二變容二極體的電容。
  2. 根據申請專利範圍第1項所述之補償電路，其中，該第一變容二極體的第一端耦接於該放大器的該第一輸入端，以及，該第一變容二極體的第二端用於接收由該控制電路提供的該偏置電壓。
  3. 根據申請專利範圍第1項所述之補償電路，其中，當該輸入訊號的該幅度增大時，該控制電路控制該第一變容二極體的該偏置電壓，以增大該第一變容二極體的電容。
  4. 根據申請專利範圍第1項所述之補償電路，其中，當該輸入訊號的幅度減小時，該控制電路控制該第一變容二極體的偏置電壓，以減小該第一變容二極體的電容。
  5. 根據申請專利範圍第1項所述之補償電路，其中，該第一變容二極體的第一端耦接於該放大器的該第一輸入端，該第二變容二極體的第一端耦接於該放大器的第二輸入端，該第一變容二極體的第二端和該第二變容二極體的第二端用於接收該控制電路提供的該偏置電壓。
  6. 根據申請專利範圍第1項所述之補償電路，其中，該控制電路包括：開關，用於將該第一變容二極體的第二端連接到該第二變容二極體的第二端，或者，將該第一變容二極體的第二端與該第二變容二極體的第二端的連接斷開。
  7. 根據申請專利範圍第6項所述之補償電路，其中，該控制電路根據該檢測結果確定接通或斷開該開關，以及，當該開關係接通的時，該控制電路將該偏置電壓施加到該第一變容二極體的第二端和該第二變容二極體的第二端；而當該開關係斷開的時，該控制電路不向該第一變容二極體的第二端和該第二變容二極體的第二端提供任何的偏置電壓。
  8. 根據申請專利範圍第1項所述之補償電路，其中，該補償電路還包括：變壓器，該變壓器用於將該輸入訊號提供給該放大器的輸入端；另一電壓感測器，用於檢測該輸入訊號的幅度，以產生另一檢測 結果；以及另一控制電路，耦接於該另一電壓感測器，用於根據該另一檢測結果控制該變壓器的中心抽頭的電壓電平。
  9. 一種補償方法，適用於放大器，其中，該補償方法包括：提供分別耦接於該放大器的第一輸入端和第二輸入端的第一變容二極體和第二變容二極管，其中，該第一變容二極體和該第二變容二極管的電容用作該放大器的輸入電容的一部分；檢測該放大器的輸入訊號的幅度，以產生檢測結果；以及控制該變容二極體的偏置電壓，以根據該檢測結果調整該第一變容二極體和該第二變容二極管的電容。
  10. 一種放大電路，其中，該放大電路包括功率放大器和如權利要求1至8中的任意一項補償電路。
TW106128354A 2016-09-06 2017-08-22 補償電路、補償方法及放大電路 TWI642269B (zh)

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