A Cmos Qpsk Demodulator Frontend For A Pon Onu

A quadrature phase-shift keying (QPSK) demodulator frontend for a passive optical network (PON) optical network unit receiver fabricated in CMOS 0.13-mu m technology is presented. The frontend integrates a compact 5-GHz ring quadrature voltage-controlled oscillator (QVCO), two inductor-less broadband mixers, and two second-order LC ladder low-pass filters. The broadband mixers operate with an input frequency between 2.5 and 7.5 GHz and with an input 1-dB compression point of -5 dBm. Area-saving design techniques are applied to lower the cost of the terminal receivers, because a competitive cost is a key requirement for the deployment of the PON access network. The frontend circuit presented achieves an area savings of more than 90% for the QVCO and mixers when compared with some published designs that can also fit the application. Measurement and simulation results are presented to verify that this frontend can be used to demodulate a QPSK signal with a data rate as high as 5 Gb/s, which is twice the downstream data rate of the current Gigabit PON standard. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1056-1062, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25902