Copyright © 2008 The Institute of Electronics, Information and Communication Engineers
Special Section on Analog Circuits and Related SoC Integration Technologies - Papers |
Analysis of CMOS Transconductance Amplifiers for Sampling Mixers
1 The authors are with the Department of Physical Electronics, Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo, 152-8552 Japan. E-mail: lining{at}ssc.pe.titech.ac.jp
In this paper the transfer function of a system with windowed current integration is discussed. This kind of integration is usually used in a sampling mixer and the current is generated by a transconductance amplifier (TA). The parasitic capacitance (Cp) and the output resistance of the TA (Ro,TA) before the sampling mixer heavily affect the performance. Calculations based on a model including the parasitic capacitance and the output resistance of the TA is carried out. Calculation results show that due to the parasitic capacitance, a notch at the sampling frequency appears, which is very harmful because it causes the gain near the sampling frequency to decrease greatly. The output resistance of the TA makes the depth of the notches shallow and decreases the gain near the sampling frequency. To suppress the effect of Cp and Ro,TA, an operational amplifier is introduced in parallel with the sampling capacitance (Cs). Simulation results show that there is a 17 dB gain increase while Cs is 1 pF, gm is 9 mS, N is 8 with a clock rate of 800 MHz.
Key Words: Windowed integration, moving average, transconductance amplifier, sampling mixer
Manuscript received October 12, 2007. Manuscript revised December 21, 2007.
References
[1] R. Bagheri, A. Mirzaei, S. Chehrazi, M. Heidari, M. Lee, M. Mikhemar, W. Tang, and A. Abidi, "An 800 MHz to 5 GHz software-defined radio receiver in 90 nm CMOS," IEEE International Solid-State Circuits Conference Digest Technical Papers, pp.1932–1941, Feb. 2006. [2] A. Mirzaei, R. Bagheri, S. Chehrazi, and A.A. Abidi, "A second-order anti-aliasing prefilter for an SDR receiver," Proc. IEEE Custom Integrated Circuits Conference, pp.629–632, Sept. 2005. [3] K. Muhammad and R.B. Staszewski, "Direct RF sampling mixer with recursive filtering in charge domain," Proc. International Symposium on Circuits and Systems, vol.1, pp.l–577–80, May 2004. [4] Y.C. Ho, R.B. Staszewski, K. Muhammad, C.M. Hung, D. Leipold, and K. Maggio, "Charge-domain signal processing of direct RF sampling mixer with discrete-time filters in bluetooth and GSM receivers," EURASIP Journal on Wireless Communications and Networking, vol.2006, pp.1–14, April 2006. [5] J. Yuan, "A charge sampling mixer with embedded filter function for wireless applications," 2nd International Conference on Microwave and Millimeter Wave Technology Proceedings, pp.315–318, Sept. 2000.
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