| 摘要: | 本研究計畫為三年期整合型計畫中的子計畫之四。整合型計畫的目標是開發一應用於數位家庭的高畫質視訊無線傳輸系統；此系統包括高畫質視訊處理、媒體存取控制、收發機的數位基頻電路以及無線前端電路。其中，無線前端將操作於57到64 GHz。本研究計畫之目的為研製60 GHz相位陣列收發前端模組，包括低雜訊放大器、功率放大器、混波器、頻率合成器，及相位偏移器，並針對相關的電路設計及製程開發作研究。最終成果將以2 × 2的相位陣列收發前端來呈現。主要的電路將使用90 nm CMOS製程。天線及相位偏移器將另行製作於低損耗基板。最後再以覆晶技術將矽晶片鍵合至低損耗基板上。本計畫有三項主要的研究重點： 1. 研製高效率的極座標式發射機 － 現有的60 GHz CMOS功率放大器效率通常相當低落，一般多在10%以下。更甚者，由於60 GHz寬頻通訊所使用的OFDM調變訊號具有相當高的峰均比；為顧及線性度，功率放大器必須操作於低功率區，使得效率低落的問題更加嚴重。因此，本計畫將使用極座標式發射機此一架構，用以提升總體效率。在極座標式發射機中，輸入訊號的波包沒有變化，功率放大器可操作在較深的非線性區域，因而效率較高。 2. 研製適用於毫米波電路的鐵電可變電容 － 在相位陣列收發前端中，壓控振盪器及相位偏移器的設計皆需要可變電容。然而，在毫米波頻段，標準的CMOS製程無法提供高品質的可變電容。微機電系統可變電容或鐵電可變電容皆可用以取代CMOS可變電容，但微機電系統可變電容有著速度緩慢的缺點。本計畫將開發基於鈦酸鍶鋇薄膜的鐵電可變電容製程，供60 GHz毫米波前端被動電路使用。天線與鐵電被動電路將製作於低損耗基板上，再以覆晶技術和CMOS晶片結合。 3. 研製毫米波相位陣列收發模組 － 當電磁波在空間中傳播時，其功率的衰減程度會隨頻率增高而加劇。因此，使用相位陣列來提高指向性，進而提升訊號的訊雜比，這在60 GHz毫米波的應用上特別有其必要性。本計畫將先開發單一收發模組。以此為基礎，研製包含多套收發模組的相位陣列收發模組。所使用的天線及收發模組數目可根據不同應用情境有所增減。多天線收發模組可用於波束掃描或增加空間多樣性，這在訊號散射物很多的居家及辦公環境中甚為重要。 This project is the 4th part of the 3-year joint project we are proposing. The goal of the joint project is to develop a wireless high-definition video interface for digital home applications. The proposed system consists of high-definition video signal processing, media access control, digital baseband and wireless front-end. The front-end will operate between 57 and 64 GHz. The goal of the individual project is to develop a 60 GHz phased-array transceiver front-end module and to conduct research on circuit design and process development. The front-end circuits that will be developed include low-noise amplifiers, power amplifiers, mixers, frequency synthesizers, phase shifters, and antennas. The ultimate results will be presented in the form of a 2-by-2 phased-array transceiver front-end module. Most of the circuits will be developed using 90 nm CMOS technology. The antennas and phase shifters will be fabricated separately on a low-loss substrate. Finally, the CMOS die will be bonded to the low-loss substrate by flip-chip, completing the front-end module. There are three key elements in this project: 1. Developing high-efficiency polar transmitters – The power efficiency of the existing 60 GHz CMOS power amplifiers are quite low, usually lower than 10%. Moreover, the OFDM modulated signal used by the 60 GHz systems has a peak-to-average ratio so high that, in order to maintain good linearity, the power amplifiers need to operate in deep back-off, which severely degrades the power efficiency. Therefore, in this project, we choose to use the polar transmitter architecture for better power efficiency. In a polar transmitter, the input signal has a constant envelope. The power amplifier can therefore operate in deeper nonlinear regions, thereby obtaining higher efficiency. 2. Developing ferroelectric varactors for millimeter-wave circuits – In phased-array front-ends, varactors are required in voltage-controlled oscillators and phase shifters. However, the standard CMOS process cannot offer high-quality varactors in millimeter-wave frequencies. Either MEMS varactors or ferroelectric varactors can be used to replace CMOS varactors, but MEMS varactors are however disadvantageous because their tuning speed is rather slow. In this project, we will develop a ferroelectric varactor process based on barium strontium titanate thin films. The antennas and ferroelectric passive circuits will be fabricated on a low-loss substrate, such as alumina or sapphire, and later bonded together with CMOS dies using flip-chip technology. 3. Developing millimeter-wave phased-array transceiver modules – As an electromagnetic wave propagates in the space, its power density drops. The power drops more as the frequency of the wave increases. Therefore, for a millimeter-wave application using carrier frequencies as high as 60 GHz, it is especially legitimate to utilize phased arrays to enhance the directivity, increasing the signal-to-noise ratio of the receive signal. In this project, we will first develop a single transceiver unit. Based on that, we will then fabricate a phased array that contains multiple transceiver units. The number of antennas may be varied according the application scenarios. Multiple-antenna transceiver modules can be used for beam scanning or spatial diversity enhancement, which are quite beneficial in home and office environments, where scatterers are everywhere. 研究期間：9908 ~ 10007 |
