Digitally controlled current-mode quadrature oscillator

A digitally controlled current-mode quadrature oscillator (DCC-MQO) is proposed. The circuit consist of four cascaded log-domain first order low-pass filter and a digitally programmable current division network. The lossy log-domain integrator gain and time constant can be adjusted using the bias currents of the logarithmic and exponential building blocks. The programmable current division network provides the bias currents for the log-domain cells which can be adjusted using a digital control word. The building blocks were implemented in a generic 180nm BiCMOS process and Spice simulation were performed to demonstrate de viability of the design.