Radio Frequency Integrated Circuit Design - Webs

316 Radio Frequency Integrated Circuit Design
Figure 8.57 A simple ring oscillator.
a high, it will discharge C 2. When the third stage sees a low, it charges C 3.
This will in turn discharge stage 1.
Thus, f is related to I /C, where I is the charging or discharging current
and C is the capacitance size.
Thus, frequency can be controlled by changing I. This circuit can operate
to high frequency if simple inverters are used. It can be made with CMOS or
bipolar transistors. However, ring oscillators, not having inductors, are usually
thought to be noisier than LC oscillators, but this depends on the design and
the technology.
References
[1] Kurokawa, K., ‘‘Some Basic Characteristics of Broadband Negative Resistance Oscillator
Circuits,’’ The Bell System Technical J., July 1969.
[2] Gonzalez, G., Microwave Transistor Amplifiers Analysis and Design, 2nd ed., Upper Saddle
River, NJ: Prentice-Hall, 1997.
[3] Voinigescu, S. P., D. Marchesan, and M. A. Copeland, ‘‘A Family of Monolithic Inductor-
Varactor SiGe-HBT VCOs for 20 GHz to 30 GHz LMDS and Fiber-Optic Receiver
Applications,’’ Proc. RFIC Symposium, June 2000, pp. 173–176.
[4] Dauphinee, L., M. Copeland, and P. Schvan, ‘‘A Balanced 1.5 GHz Voltage Controlled
Oscillator with an Integrated LC Resonator,’’ International Solid-State Circuits Conference,
1997, pp. 390–391.
[5] Zannoth, M., et al., ‘‘A Fully Integrated VCO at 2 GHz,’’ IEEE J. Solid-State Circuits,
Vol. 33, Dec. 1998, pp. 1987–1991.
[6] Hegazi, E., H. Sjoland, and A. Abidi, ‘‘A Filtering Technique to Lower LC Oscillator
Phase Noise,’’ IEEE J. Solid-State Circuits, Vol. 36, Dec. 2001, pp. 1921–1930.
[7] Razavi, B., ‘‘A Study of Phase Noise in CMOS Oscillators,’’ IEEE J. Solid-State Circuits,
Vol. 31, March 1996, pp. 331–343.
[8] Leeson, D. B., ‘‘A Simple Model of Feedback Oscillator Noise Spectrum,’’ Proc. IEEE,
Feb. 1966, pp. 329–330.
[9] Adams, S., The Dilbert Principle, New York: HarperCollins, 1996.