A 67-GHz low-phase-noise oscillator and its application in a polar transmitter

In this paper, a low-phase-noise 67-GHz CMOS oscillator is presented. This inductorless voltage-controlled oscillator (VCO) employs a combination of standing-wave and travelling-wave oscillators to generate multi-phase outputs. A filtering technique is used to reduce the phase noise of the VCO. The oscillator achieves a tuning range of 5.2 GHz using a combination of coarse and fine tuning methods. The proposed multi-phase oscillator is designed and fabricated in a 0.13-μm CMOS process. Operating at 67 GHz, the VCO consumes 14 mW from a 1.2-V supply and achieves an output phase noise of ?95.66 dBc/Hz (?107.89 dBc/Hz) at a 1 MHz (10 MHz) offset. The chip area is 0.9 mm2. As an application example for the presented multi-phase oscillator, a polar transmitter structure is proposed. The transmitter is designed for systems that use a circular quadrature-amplitude modulation (QAM) constellation. A specific example of a 16-QAM transmitter is presented. The desired output phase is chosen by an 8-to-1 multiplexer, and a variable gain amplifier (VGA) is used to achieve the desired amplitude. Based on post-layout simulations, the 60-GHz 16-QAM transmitter consumes 43.2 mW from a 1.2-V supply.