A Design of Continuous-Time Delta-Sigma Modulators Using a Fully-Differential Resonant-Tunneling Comparator

Keisuke EGUCHI
Mitsuhiro TANIHATA
Takao WAHO

IEICE TRANSACTIONS on Electronics   Vol.E89-C    No.7    pp.979-984
Publication Date: 2006/07/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.7.979
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Heterostructure Microelectronics with TWHM2005)
Category: THz Devices
resonant-tunneling,  delta-sigma,  continuous-time,  bandpass,  comparator,  

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Ultrahigh-speed continuous-tine delta-sigma modulators (DSMs) have been designed by using a fully-differential comparator consisting of resonant-tunneling diodes (RTDs) and HEMTs. Continuous-time lowpass and bandpass filters using HEMTs have also been incorporated to obtain lowpass- and bandpass-type DSMs, respectively. Circuit simulation assuming 0.1-µm InP-based HEMT and RTD technology has revealed a successful operation of the 2nd-order lowpass DSM at a sampling frequency of 20 GHz. The clock frequency was 10 GHz because of the double sampling function of the present comparator. The 2nd-order bandpass DSM has also been designed with a center frequency of 3 GHz. These results clearly show high potential of the present delta-sigma modulators.