Title :
A 400-MHZ 4th-order CT bandpass ΣΔ modulator with automatic frequency tuning
Author :
Loke, Wing Fai ; Oh, Chin Fong ; Xu, Yong Ping
Author_Institution :
Dept. of Electr. & Comput. Eng., Nat. Univ. of Singapore, Singapore
Abstract :
This paper presents the design and implementation of a high-speed continuous-time (CT) bandpass sigma-delta modulator targeted for an intermediate frequency (IF) receiver with an IF of 400 MHz for GSM/WCDMA application. The loop filters in the modulator is implemented with Gm-C Opamp integrators in biquad configuration. An automatic frequency tuning circuit is employed to reduce the effects of process and temperature variations on the centre frequency. Based on a commercial 0.35-μm SiGe BiCMOS process, the 4th-order bandpass modulator is able to obtain maximum SNRs of 77 dB and 62 dB for the signal bands of 200 kHz and 3.84 MHz, respectively, when sampled at 1.6 GHz.
Keywords :
band-pass filters; cellular radio; circuit tuning; code division multiple access; modulators; sigma-delta modulation; 200 kHz; 3.84 MHz; 400 MHz; 62 dB; 77 dB; BiCMOS process; GSM application; WCDMA application; automatic frequency tuning circuit; biquad configuration; continuous-time bandpass ΣΔ modulator; intermediate frequency receiver; loop filters; Automatic frequency control; Band pass filters; Circuit optimization; Delta-sigma modulation; Frequency modulation; GSM; Multiaccess communication; Silicon germanium; Temperature; Tuning;
Conference_Titel :
VLSI Design and Video Technology, 2005. Proceedings of 2005 IEEE International Workshop on
Print_ISBN :
0-7803-9005-9
DOI :
10.1109/IWVDVT.2005.1504455
