A 28 GHz SiGe QVCO with an I/Q phase error detector for an 81–86 GHz E-band transceiver

This paper presents a 28 GHz QVCO intended to be used in an 81-86 GHz E-band transceiver. E-band transceivers using e.g. 16 QAM modulation schemes are sensitive to I/Q phase error. Already a three degree error significantly degrades the bit error rate, and careful control of the phase error of the 28 GHz QVCO is therefore required. In the presented design the phase error can be tuned using four varactors, each connected to one of the QVCO outputs. The phase error is detected in two cross-coupled active mixers, creating a DC-level proportional to the phase error. The accuracy of the detector has been verified by Monte Carlo simulations showing a 3 sigma phase error of one degree. The QVCO is designed in a SiGe process with f_T = 200 GHz. The current consumption is 14 mA from a 1.5 V supply and 57 mA from a 2.5 V supply. The 2.5 V supply is dedicated to the detector and output buffers. At 1 MHz offset the phase noise equals -105 dBc/Hz with a FOM of -181 dBc/Hz and a FOM_T of -186 dBc/Hz. The die area equals 1.3 mm².