An X-Band Transformer-Coupled Varactor-Less Quadrature Current-Controlled Oscillator in 0.18 μm SiGe BiCMOS Technology

This paper presents a transformer-coupled varactorless quadrature current-controlled oscillator (QCCO) RFIC covering the entire X-Band from 8.7 GHz to 13.8 GHz. The QCCO incorporates a transformer-coupled technique that achieves frequency tuning by varying the bias currents in the primary and secondary windings. Fabricated in a 0.18 mu m SiGe BiCMOS technology, the prototype QCCO achieves a 45.3% wide tuning range. With two stacked octagonal transformers the QCCO core circuit occupies 0.4x0.5 mm(2) chip area and draws 8-18 mA current under a 1.8 V power supply. The measured phase noise for 11.02 GHz quadrature outputs is about -110 dBc/Hz at 10 MHz offset. The QCCO achieves a phase noise, power and area efficiency figure-of-merit of -191 dBc/Hz.