Design and analysis of CMOS broad-band compact high-linearity modulators for gigabit microwave/millimeter-wave applications

• Published in: IEEE transactions on microwave theory and techniques 2006-01, Vol.54 (1), p.20-30
• Main Authors: Hong-Yeh Chang, Pei-Si Wu, Tian-Wei Huang, Wang, Huei, Chung-Long Chang, Chern, J.G.J.
• Format: Article
• Language: English
• Subjects: Binary phase shift keying; Binary phase-shift keying (BPSK); Circuit topology; CMOS; CMOS process; coupler; Digital modulation; Distributed parameter circuits; millimeter wave (MMW); MMICs; Phase modulation; Phase shift keying; Power transmission lines; Propagation losses; quadrature amplitude modulator (QAM)
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2005.860900

CMOS broad-band compact high-linearity binary phase-shift keying (BPSK) and IQ modulators are proposed and analyzed in this paper. The modulators are constructed utilizing a modified reflection-type topology with the transmission lines implemented on the thick SiO/sub 2/ layer to avoid the lossy silicon substrate. The monolithic microwave integrated circuit (MMIC) chips were fabricated using standard bulk 0.13-/spl mu/m MS/RF CMOS process and demonstrated an ultracompact layout with more than 80% chip size reduction. The broadside couplers and 180/spl deg/ hybrid for the modulators in the CMOS process are broad-band designs with low phase/amplitude errors. The dc offset and imbalance for the proposed topology are investigated and compared with the conventional reflection-type modulators. The measured dc offset was improved by more than 10 dB. Both BPSK and IQ modulators feature a conversion loss of 13 dB, a modulation bandwidth of wider than 1 GHz, and second- and third-order spur suppressions of better than -30 dBc. The IQ modulator shows good sideband suppression with high local-oscillator suppression from 20 to 40 GHz. The modulators are also evaluated with a digital modulation signal and demonstrate excellent modulator quality and adjacent channel power ratio.