應用於W波段收發機系統之前端電路分析及設計

隨著矽製程技術不斷發展，工作頻率可達到幾百GHz，除了在商業應用上有很大的發展潛力，如果能將矽製程應用在天文接收望遠鏡上，讓天文接收系統可以整合到一顆晶片，將可以幫助大型多像素焦平面陣列發展到W波段甚至更高的頻段。為了實現能夠涵蓋整個W波段的接收機系統，我們首先設計了一顆W頻帶接收器電路，包含射頻端的低雜訊放大器、寬頻混頻器、中頻端放大器以及含有三倍頻器和驅動放大器的本振電路，所有電路皆整合在一顆晶片，面積大小為1050×820μm2。而為了有效地增加中頻頻寬且不影響其轉化增益，我們發展出雙調變的轉化矩陣公式來探討電晶體偏壓以及輸出阻抗的對混頻器的效能影響，此雙調變轉化矩陣公式可同時考量本振端轉導和通道電導產生的調變。此外，我們將中頻放大器輸入端的寄生電容結合成高阻抗的等效傳輸線，使得主動偏壓下的混頻器可以在整體頻寬內都輸出一樣的增益。最後利用65-nm CMOS製程製作一顆77~110GHz接收器電路，其中頻頻寬為33GHz。此電路的轉換增益和雜訊指數為10dB和20B、輸入參考P1dB是-15dBm、在偏壓1.3V下的整體直流功率消耗為330mW。此外，我們專注於探討微波功率放大器中的八合一合成器的插入損耗以提升其效率。當合成器在電阻電容負載下做阻抗轉換，我們可以得到傳輸線相對應的特性阻抗和電氣長度，而較短的線意味著有較大頻寬和較低插入損耗。然而電壓波在不匹配的傳輸線之間會有多重反射，因此必須將多重反射造成的功率損耗一併考慮進去；也就是說，如果我們只用e^(-2αL)當作功率衰減指數是不夠的。從我們推導的公式來看，我們提出的八合一功率合成器的插入損耗在94GHz可低至0.92dB、比傳統的四分之一波長合成器(1.5dB) 小很多；另外我們也推導了汲極偏壓端之傳輸線和隔直流電容器的插入損耗。最後利用40nm-CMOS製程製作一顆77~110GHz 的功率放大器做為驗證，此放大器採用疊加電晶體架構，在整體頻寬下可輸出大於18dB的增益，輸出1dB增益壓縮點落在13dBm。由於系統的需求，我們提出一個新型的架構可以在不影響增益前提下達到足夠的頻寬。此架構是建立在分佈式放大器的基礎上，將輸入等效傳輸線中的放大級採用交錯式排列方式而非傳統平行式，經由數學公式分析以及電路模擬驗證後確實可以大幅增加頻寬。為了驗證，我們使用0.1μm-GaAs pHEMT製程製作了平行式和交錯式的主動式功率分配器並進行量測，量測結果顯示交錯式架構確實有頻寬的優勢。進而我們使用90nm CMOS製程製作一顆從DC到40GHz的寬頻功率分配器，其兩個輸出端的大小和相位差在20GHz以下為0.15dB和2.6度，20GHz~40GHz範圍內則是0.16dB和14度。輸出端的隔絕度在整體頻寬內都大於30dB。

關鍵字

W波段；接收器； CMOS ；寬頻；功率分配器；功率放大器

並列摘要

With maximum operating frequency in hundreds of gigahertz, today’s silicon processing technologies show great promise for commercial millimetre-wave applications. If silicon process be used in radio-astronomical telescopes, it could facilitate the development of large multi-pixel focal plane arrays up to W-band and beyond. To develop a receiver system, which covers overall W-band frequency, we start with the design of W-band receiver where RF-LNA, wideband mixer, IF amplification, LO tripler and driving amplifier are all integrated into one single chip of 1050×820μm2. To effectively extend the mixer’s IF bandwidth while retaining its conversion gain, impacts of the mixing transistor’s drain bias and output loading impedance are explored using dual-modulation conversion-matrix method, which allows both the LO-induced transconductance modulation and channel-conductance modulation to be considered simultaneously. It is shown that, by merging the input capacitance of the IF amplifier into a high-impedance artificial transmission line, an actively-biased mixer can have constant conversion gain over broad bandwidth. A 77–110GHz 65nm-CMOS receiver with 33GHz IF bandwidth is then designed and measured. Its conversion gain and noise figure are 10dB and 20dB, respectively, and the input-referred P1dB is -15dBm; the overall power consumption is 330mW under 1.3V drain bias. Besides, we investigate the insertion loss of the broadband 8-way power combiner used in our millimeter-wave power amplifier design. By treating this combiner as impedance-transformer under RC loading condition, both the characteristic impedance and electrical length of the constituting metal lines can be obtained where the much shorter line length suggests wider bandwidth and lower insertion loss (IL). However, proper loss analysis must take into account the multi-reflection of voltage wave along these mismatched transmission lines, i.e., the use of the power attenuation expression e^(-2αL) is just not accurate enough. With our derived equations, it shows that the insertion loss of our proposed 8-way combiner can be as low as 0.92dB at 94GHz, which is much smaller than the 1.5dB for the conventional quarter-wavelength combiner. Mathematics for the insertion loss of the drain-bias shunt stub and the output DC-blocking capacitor have also been derived. As a demonstration, a 77~110 GHz 40nm-CMOS PA made of cascode transistors is then designed that has more than 18dB gain and its OP1dB is around 13dBm across the whole frequency range. According to the need of the system, a new wideband active power splitter design where the gain cells along the input transmission line are arranged in interleaf rather than the conventional parallel style, thus the circuit’s high-frequency performance can be greatly improved. Both theoretical analysis and circuit simulation have been carried out; as a demonstration, parallel and interleaf active power splitters are designed using 0.1μm-GaAs pHEMT process and measured on-wafer. The results clearly indicates the superiority of the interleaf topology. A 40GHz interleaf active power splitter in 90nm-CMOS is then presented where the magnitude and phase imbalance between the two output ports are 0.15dB and 2.6o at 20GHz, and 0.16dB and 14o at 40GHz. The output-port isolation is better than 30dB across the whole frequency range.

並列關鍵字

W-band ； Receiver ； CMOS ； Wideband ； Power Splitter ； Power Amplifier

參考文獻

References

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[1] May, J. W., Rebeiz, G. M.: 'Design and characterization of W-Band SiGe RFICs for passive millimeter-wave imaging', IEEE Trans. Microwave Theory Tech., 2010, 58, (5), pp. 1420–1430

Google Scholar

[2] Tomkins, A., Garcia, P., Voinigescu, S. P.: 'A passive W-Band imaging receiver in 65-nm bulk CMOS', IEEE J. Solid- State Circuits, 2010, 45, (10), pp. 1981–1991

Google Scholar

[3] Mitomo, T., Ono, N., Hoshino, H., et al.: 'A 77 GHz 90 nm CMOS Transceiver for FMCW Radar Applications', IEEE J. Solid-State Circuits, 2010, 45, (4), pp. 98–937

Google Scholar

[4] Preiffer, U. R.: 'Sub-millimeter wave active imaging with silicon integrated circuits'. Int. Conf. on Infrared, Millimeter and Terahertz Waves, Oct. 2011

Google Scholar

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應用於W波段收發機系統之前端電路分析及設計

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