把手教你看懂RF原理圖——原理圖入門（二）

把手教你看懂RF原理圖——原理圖入門（二）

作者簡介：Wayne，資深射頻工程師，多年來一直就職於國內手機廠商射頻開發第一線，深諳Q廠和M廠smart phone平臺架構，精通射頻硬件的設計工作和RF Driver配置。出於無私分享精神，特將多年來自己射頻基礎知識積累和開發經驗，書寫成文供大家學習參考，並歡迎各位看官指正和垂詢。

接上一篇，上述原理圖有兩個核心器件組成，分別是U3301 SKY77927-11以及U3201 SKY77643，他們分別是什麼器件，有什麼功能，這需要打開規格書來查找了。

先看SKY77927-11，

The SKY77927-11 SkyLiTE™ Tx-Rx Front-End Module (FEM) offers a complete Power Amplifier (PA) and switching solution for advanced 2G/3G/4G cellular handsets .

Two PAs support quad-band GSM, GPRS, EDGE multi-slot operation and TD-SCDMA and TDD LTE transmission. The FEM facilitates flexible broadband RF switch-through by means of outward switching of the LB/MB PA RF inputs and 16 transmit/receive (TRx) antenna switch ports covering all 3G/4G bands from 700 MHz through 2300-2700 MHz. In support of downlink inter-band Carrier Aggregation (CA), the TRx ports are partitioned into two independent switch blocks, comprising 7 LB ports and 9 M/HB ports. Each switch block includes an integrated directional coupler that may be monitored on the CPL port with selectable forward or reverse directionality. A built-in diplexer provides simultaneous LB and M/HB reception required for downlink CA at the single antenna port.

內部架構如下：

簡而言之，SKY77927是內部集成了高中頻與低頻開關以及濾波器的帶有2G PA的射頻前端模組。

再看看另外一個器件SKY77643

SKY77643-11 SkyLiTE™ is a key building block for global or five-mode front-end

implementation. As a hybrid multimode multiband (MMMB) Power Amplifier Module (PAM), the SKY77643-11 SkyLiTE™ supports 3G / 4G handsets and operates

efficiently in WCDMA, TD-SCDMA, and LTE modes. The module is fully programmable through a Mobile Industry Processor Interface (MIPI®).

The module includes a WCDMA / LTE block for low, high, and mid-bands, a MultiFunction Control (MFC) block, and the RF input/output ports are internally matched to 50 Ω loads to minimize external components. A CMOS integrated circuit utilizes standard MIPI® controls for the internal MFC interface and operation. Extremely low leakage current maximizes handset standby time.

The InGaP die, the silicon die and passive components are mounted on a multi-layer

laminate substrate. The assembly is encapsulated in a 4.0 mm x 6.8 mm x 0.8 mm,

42-pad MCM, SMT package which allows for a highly manufacturable, low cost

solution.

3G: The SKY77643-11 SkyLiTE™ supports WCDMA, High-Speed Downlink Packet

Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet

Access (HSPA+), and TD-SCDMA modulations. Varying the input power level provides control of output power. Adjusting the VCC using a DCDC converter maximizes

efficiency of each power level and modulation type.

4G: The SKY77643-11 SkyLiTE™ supports 1.4, 3, 5, 10, 15, 20 MHz channel

bandwidths. Similar to 3G operation, varying the input power level provides control of output power. Adjusting the VCC using a DCDC converter maximizes efficiency at each power level.

總結SKY77643就是一個支持多模多頻的多輸出LTE PA模組。

接下來看兩個器件的連接，很簡單，就是通過中間的雙工器進行連接TX、RX、TRX

這個是最簡單的信號流向劃分。當然如果所有的頻段都是如此簡單的話，原理圖就很好了解了。

對於LTE而言和以往的2G/3G的一個顯著差異，就是CA的概念。而不同的CA需求會導致不同的硬件設計，越多的CA需求，會導致更復雜的硬件設計，這個對於RF驅動以及RF工程師而言，都會增加設計難度。

簡單來說，CA包括三個類型：

1. 帶內連續CA

2. 帶內非連續CA

3. 帶外CA

針對第一個，硬件設計最簡單，只需要對應TRX通路器件滿足帶內CA的頻段帶寬。

第二個，需要在收發機端口器件能同時支持該頻段的非連續信號。

第三個，需要在收發機端口器件能同時支持所有CA頻段的信號。

結合上面的簡要說明，可以理解上述原理圖能支持HB/MB與LB之間的CA組合，如果需要實現HB+MB，或者HB+HB，MB+MB的CA，都需要另外增加通路上能同時工作該信號的器件，例如四工器，功分器等等。