Design method for low-power, low phase noise voltage-controlled oscillators

Abstract

This paper presents a design method for voltage controlled oscillators (VCOs) with simultaneous small size, low phase noise, DC power consumption and thermal drift. We show design steps to give good prediction of VCO phase noise and power consumption behavior: (1) measured resonator frequency-dependent parameters; (2) transistor additive phase noise/ noise figure characterization; (3) accurate tuning element model; and (4) bias-dependent model in case of an active load. As an illustration, the design of a 3.4-GHz bipolar transistor VCO with varactor tuning is presented Oscillator measurements demonstrate low phase noise (-40dBc@ 100Hz and better than -lOOdBcfflOkHz) with power consumption on the order of a few milliwatts with a circuit footprint smaller than 0.6cm2. The temperature stability is found to be better than +/-10ppm/degC from -40degC to +30degC. The oscillators are implemented using low-cost off-the-shelf surface-mountable components, including a micro-coaxial resonator. The VCO directly modulates the current of a laser diode and demonstrates a short-term stability 2-10/radictau Bias of clock. when locked to a miniature Rubidium atomic clock.