Hsieh, Hsieh-HungHsieh-HungHsiehLiao, Yu-TeYu-TeLiaoLIANG-HUNG LU2020-06-112020-06-1120070018-9480https://scholars.lib.ntu.edu.tw/handle/123456789/498222https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250184187&doi=10.1109%2fTMTT.2007.896815&partnerID=40&md5=afab671c2ddf022ce42d0c7d042736e3A miniaturization technique for the quadrature hybrid is proposed for monolithic-microwave integrated-drcuit applications. By using active inductors for the circuit implementation, a significant area reduction can be achieved due to the absence of distributed components and spiral inductors. Using a 0.18-μm bulk CMOS process, a 4.2-GHz quadrature hybrid is implemented for demonstration. The chip size measures 0.72 × 0.64 mm2 where the hybrid circuit only occupies active area of 0.4 × 0.2 mm2. With the enhanced Q factor provided by the active inductors, the fabricated circuit has an insertion loss less than 0.4 dB for -3-dB coupling while maintaining excellent return losses and port isolation in the vicinity of the center frequency. Owing to the reconfigurable capability provided by the CMOS active inductors, the center frequency of the quadrature hybrid can be varied from 3.6 to 4.7 GHz by adjusting the bias currents, exhibiting a tuning range of 26% at C-band. © 2007 IEEE.CMOS active inductors; Insertion loss; Lumped components; Miniaturization; Monolithic microwave integrated circuit (MMIC); Quadrature hybridActive inductors; Lumped components; Miniaturization; Quadrature hybrid; Bias currents; CMOS integrated circuits; Electric inductors; Insertion losses; Natural frequencies; Monolithic microwave integrated circuitsconference paper10.1109/TMTT.2007.8968152-s2.0-34250184187WOS:000247278500002