科研之友
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摘要
RFIC integration has seen dramatic progress since the early 1990s. For example, Si-based single-chip products for GSM, WLAN, Bluetooth, and DECT applications have become commercially available. However, RF power amplifiers (PAs) and switches tend to remain off-chip in the context of single-chip CMOS/BiCMOS transceiver ICs for handset applications. More recently, several WLAN/Bluetooth vendors have successfully integrated less demanding PAs onto the transceivers. This paper will focus on single-chip RF-system-on-a-chip (i.e., ※RF-SoC§) implementations that include a high-power PA. An analysis of all tradeoffs inherent to integrating higher power PAs is provided. The analysis includes the development cost, time-to-market, power efficiency, yield, reliability, and performance issues. Recent design trends on highly integrated CMOS WiFi transceivers in the literature will be briefly reviewed with emphasis on the RF-SoC product design tradeoffs impacted by the choice between integrated versus external PAs. 1. Introduction In a manner analogous to Moore＊s law for digital ICs, it is expected that one can significantly reduce the cost and the form factor of communication products by progressive integration of the RF/analog system. However, the RF portion of many advanced communication systems remains a mixture of components based on different technologies and interface requirements. For example, compound semiconductors (primarily in group III-V) predominate for low-noise amplifiers (LNAs), switches and power amplifiers (PAs) in cellular phones. This prevents progressive integration towards a true single-chip radio. Historically, one might argue that this is partly because, prior to the late 1980＊s, most RF circuits were designed for military applications. By natural market evolution, the RF component industry has moved rapidly from the low-volume discrete RF circuitry to the high-volume low-cost, highly integrated commercial products. Moreover, this trend has encouraged circuit topologies that are friendlier to integration. For example, differential-type circuit topologies such as the Gilbert balanced mixers that suffer from device mismatch issues in discrete RF design, have become very popular for integrated RFICs. While GaAs-based devices can be inexpensive and highly efficient at GHz frequencies, they offer a limited ability to integrate with CMOS baseband chips. Fueled by the recent wireless Internet explosion, rapidly growing broadband communication markets are driving the development of reliable, high performance and economical RF integrated circuits and
