Paper Info
Title
A Second-Order Multibit Complex Bandpass Delta Sigma Ad Modulator With I, Q Dynamic Matching And Dwa Algorithm
Abstract
We have designed, fabricated and measured a second-order multibit switched-capacitor complex bandpass Delta Sigma AD modulator to evaluate our new algorithms and architecture. We propose a new structure of a complex bandpass filter in the forward path with 1, Q dynamic matching, that is equivalent to the conventional one but can be divided into two separate parts. As a result, the Delta Sigma modulator, which employs our proposed complex filter can also be divided into two separate parts, and there are no signal lines crossing between the upper and lower paths formed by complex filters and feedback DACs. Therefore, the layout design of the modulator can be simplified. The two sets of signal paths and circuits in the modulator are changed between I and Q while CLK is changed between high and low by adding multiplexers. Symmetric circuits are used for I and Q paths at a certain period of time, and they are switched by multiplexers to those used for Q and I paths at another period of time. In this manner, the effect of mismatches between I and Q paths is reduced. Two nine-level quantizers and four DACs are used in the modulator for low-power implementations and higher signal-to-noise-and-distortion (SNDR), but the nonlinearities of DACs are not noise-shaped and the SNDR of the Delta Sigma AD modulator degrades. We have also employed a new complex bandpass data-weighted averaging (DWA) algorithm to suppress nonlinearity effects of multibit DACs in complex form to achieve high accuracy; it can be realized by just adding simple digital circuitry. To evaluate these algorithms and architecture, we have implemented a modulator using 0.18 mu m CMOS technology for operation at 2.8 V power supply; it achieves a measured peak SNDR of 64.5 dB at 20 MS/s with a signal bandwidth of 78 kHz while dissipating 28.4 mW and occupying a chip area of 1.82 mm(2). These experimental results demonstrate the effectiveness of the above two algorithms, and the algorithms may be extended to other complex bandpass Delta Sigma AD modulators for application to low-IF receivers in wireless communication systems.
Year
DOI
Venue
2007
10.1093/ietele/e90-c.6.1181
IEICE TRANSACTIONS ON ELECTRONICS
Keywords
Field
DocType
complex bandpass Delta Sigma AD modulator, I, Q path mismatches, dynamic matching, miltibit, data-weighted averaging
Band-pass filter,Algorithm,Modulation,Mathematics
Journal
Volume
Issue
ISSN
E90C
6
1745-1353
Citations 
PageRank 
References 
1
0.52
0
Authors
14
Name
Order
Citations
PageRank
Hao San14116.68
Yoshitaka Jingu221.63
Hiroki Wada3263.83
Hiroyuki Hagiwara421.63
Akira Hayakawa521.97
Haruo Kobayashi63825.15
Tatsuji Matsuura7278.16
Kouichi Yahagi821.29
Junya Kudoh973.77
Hideo Nakane1021.29
Masao Hotta11309.59
Toshiro Tsukada12204.74
Koichiro Mashiko1322.31
Atsushi Wada1422.31