Anti-blocker design techniques for MOSFET-C filters for direct conversion receivers

A linearized MOSFET-C low-pass filter suitable for a baseband channel selection filter for a direct conversion receiver is presented. Using polysilicon resistors instead of MOSFET resistors in the input and output part, the filter achieves very high out-of-band linearity but maintains the original transfer function under the control of a continuous on-chip cutoff tuning scheme. In order to enhance the linearity of the triode-mode MOSFET variable resistors, the gates of the MOSFETs are driven by a charge pump in the cutoff control loop. Also, an appropriate gain scaling is implemented to lower the input referred noise, thus making the out-of-band dynamic range wider. This fifth-order elliptic filter achieves -2 dBV in-band IIP3, +28 dBV out-of-band IIP3, +94 dBV out-of-band IIP2 and -87 dBV input-referred noise, and dissipates 6.2 mW from a 2.7-V supply; the on-chip continuous automatic tuning system dissipates 4.1 mW.

[1]  J. F. Dickson,et al.  On-chip high-voltage generation in MNOS integrated circuits using an improved voltage multiplier technique , 1976 .

[2]  M. Banu,et al.  An elliptic continuous-time CMOS filter with on-chip automatic tuning , 1985, IEEE Journal of Solid-State Circuits.

[3]  Chris J. M. Verhoeven,et al.  Charge pump for optimal dynamic range filters , 1994, Proceedings of IEEE International Symposium on Circuits and Systems - ISCAS '94.

[4]  H. Khorramabadi,et al.  Baseband filters for IS-95 CDMA receiver applications featuring digital automatic frequency tuning , 1996, 1996 IEEE International Solid-State Circuits Conference. Digest of TEchnical Papers, ISSCC.

[5]  A. Yasuda,et al.  A 2.7-V, 200-kHz, 49-dBm, stopband-IIP3, low-noise, fully balanced gm-C filter IC , 1999 .

[6]  Hanspeter Schmid,et al.  A charge-pump-controlled MOSFET-C single-amplifier biquad , 2000, 2000 IEEE International Symposium on Circuits and Systems. Emerging Technologies for the 21st Century. Proceedings (IEEE Cat No.00CH36353).

[7]  A. Parssinen,et al.  A channel selection filter for a WCDMA direct conversion receiver , 2000, Proceedings of the 26th European Solid-State Circuits Conference.