A Low LO Leakage and Low Power LO Buffer for Direct-Conversion Quadrature Demodulator

Toshiya MITOMO  Osamu WATANABE  Shoji OTAKA  Ryuichi FUJIMOTO  Shunji KAWAGUCHI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E88-C   No.6   pp.1212-1217
Publication Date: 2005/06/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.6.1212
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Analog Circuit and Device Technologies)
Category: RF
Keyword: 
LO buffer,  quadrature demodulator,  direct-conversion,  self mixing,  DC offset,  

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Summary: 
A DC offset caused by self-mixing is a serious problem for direct-conversion receivers. Local oscillation (LO) leakage via quadrature demodulators (QDEMOD) must be suppressed in order to achieve a low DC offset. An LO buffer which drives QDEMOD mainly causes the LO leakage. We proposed an LO buffer which has a high-pass frequency response with small occupied area and low current consumption. A QDEMOD using the proposed LO buffer is fabricated using a SiGe BiCMOS process. Measured low LO leakage of -70 dBm is achieved, which is 10 dB lower than that of a QDEMOD with a conventional LO buffer. This measured result indicates that the proposed LO buffer is suitable for QDEMODs for direct-conversion receivers.