A 2.7–6.1GHz CMOS local oscillator based on frequency multiplication by 3/2

Frequency multiplication by 3/2 is proposed as a means to expand the frequency generation capabilities of a single LC VCO. Fractional frequency multiplication is obtained by cascading a broadband injection locked modulo-two divider and a multiply-by-three circuit based on edge combining. The proposed solution is inductorless, thus very compact. It allows the generation of all frequencies from 2.7 to 6.1GHz with a performance suitable for cellular standards. It shows a noise floor below -150 dBc and a spurious level below -35 dBc. The multiplier by 3/2 consumes 5mA and the VCO draws 10mA from a 1.2V supply. The additional power consumption due to the multiplier trades with the small area penalty and the flexibility of this solution, compared to the use of multiple LC VCOs.