射頻CMOS主動電感器的研究與應用

Abstract

在本論文中，我們首先針對各種不同的CMOS主動式電感器(Active Inductor)與負電導產生器(Negative Conductance Generator)的組合應用於不同工作頻率的射頻放大器設計研究，並且對各種不同的主動式電感器使用不同的損失補償技術來改進此電感器特性的設計。接著將此改進的主動式電感器應用於寬頻放大器(Wideband Amplifier)與電壓控制震盪器(Voltage-Controlled Oscillator)電路，以證實射頻電路中使用主動電感器能得到比使用平面螺旋型電感器(Planar Spiral Inductor)有更好的優點。如，可得到很高的品質因數(Quality Factor)、高的電感量(Inductance)等特性；並且使用主動式電感器的射頻電路於晶片製作時的面積將比使用平面螺旋型電感器的射頻電路所佔的晶片面積小很多的優點。 本論文首先描述使用平面式螺線型電感器元件應用於射頻放大器設計，雖能得到良好的特性結果，但仍有些缺點產生。如，平面式螺線型電感器佔用的晶片面積太大、品質因數很低、不容易準確控制電感的特性等缺點。而這些缺點可以使用主動式的電感器來給予改善。應用目前已經存的主動電式感器結合改進電感器特性的負電導產生器技術設計工作於不同頻帶的射頻放大器。經由模擬結果得到輸出的增益可達到17dB以上、雜訊指數低於6dB，此結果與使用平面式螺線型電感器相近，而面積為使用平面式螺線型電感器的四分之一及使用主動電感器的功率消耗也有明顯的降低。所以，得知使用主動式電感器將優於使用平面式螺線型電感器。 然而，為降低改善主動電感器特性的電路複雜度，提出各種不同的簡單補償電路對各種不同的電感器作改良設計，得到高效能的主動電感器，且能得到電路非常簡單的電感器。經由數學的分析、電路的模擬及實際的測量結果，此改良後的電感器可得到很高的品質因數（約104以上）。最後，將此改良後的主動式電感器應用於寬頻放大器及電壓控制振盪器的電路中。於寬頻放大器可以得到頻帶寬度由0Hz到1GHz有平坦的增益（約18dB）特性。對於電壓控制振盪器得到寬的調整範圍（1GHz到3GHz）、-98dBc/Hz的相位雜訊及10mW的固定功率消耗。因此，經由以上的研究結果證實使用主動電感器於射頻電路為一種可行的方法，此種方法可使設計射頻電路時可以大幅的降低所佔的晶片面積的成本。

In this thesis, we will focus on the research illustration and design comparison on combing several different CMOS active inductor with negative conductance generator (NCG) applied in RF amplifier on different operating frequency. And we will apply various loss compensation techniques on several different active inductors to improve the characteristics of the inductors. Furthermore, we applied the improved active inductor on the wideband amplifier and the voltage-controlled oscillator to prove that using the active inductors in RF can have more advantages than using the planar spiral inductor. For example, the active inductor can have a higher quality factor, a higher operating frequency, and a higher inductance etc. On the other hand, in radio frequency circuit design, the size of the chip used in an active inductor will be much smaller than the one used in a planar spiral inductor. The design of the use of the planar spiral inductor applied on the radiofrequency amplifier will be described at the beginning of the thesis. Though the above design shows the result of performing good characteristics, some disadvantages of this design also exist. For example, the size of the chip of the circuits using planar spiral inductor too large, quality factor is too low, and the characteristics of the inductor cannot be controlled easily and accurately. We presented the use of the active inductor to improve the disadvantages mentioned above. We applied the techniques of the negative conductance generator, which combines the existing active inductor and the characteristics of the improved inductor, to work on the different bandwidth radio frequency. From the simulation results, we found that the output power gain is over 17dB, and the noise figure is lower than 6dB. The simulation also shows that the results are very close to those using the planar spiral inductor, and the size of circuit using the active inductor design is one forth of that using planar spiral inductor. Moreover, the power consumption decreases dramatically when using active inductor. So, we can conclude that using active inductor generates more benefits than using planar spiral inductor. For minimizing the complexity of the active inductor circuits, we present several simple compensated circuits for each different active inductor to reach the goals of performing higher performance and an easy design circuit. From the mathematical analysis, simulated results, and measured results, the improved active inductor can obtain a very high quality factor, which is above 104. Finally, we present the results of applying the improved active inductor in the circuits of wideband amplifier and voltage-controlled oscillator. From the wideband amplifier’s point of view, the amplifier can generate a flat gain, which is about 18dB, in the bandwidth from 0Hz to 1GHz. From the voltage-controlled oscillator’s point of view, the voltage-controlled oscillator can generate a wide tuning range from 1GHz to 3GHz, -98dBc/Hz phase noise and steady 10mW power consumption. As the result, we can conclude that using active inductor in the radio frequency is a workable solution via the approach mention above. This solution also saves us a lot of cost taken by the size of the chip during the design stage of the radio frequency.