Abstract
Throughout history, electronic engineers have been known for modifying or changing fundamental circuit building blocks to keep up with evolving technology. Since the advent of the microprocessor and microcontroller, engineers are routinely faced with an interface dilemma; the interface between reliable old analog circuitry and ever so evolving digital circuitry. This would be a trivial task if all analog circuits were easily converted to digital circuits. Unfortunately, that is not the case and sometimes the best solution is to integrate analog and digital circuits together to take advantage of both worlds. Analog circuits sometimes offer a unique attribute or precision that cannot be digitally realizable and thus, should be left alone. This project focuses on a Digitally Controlled Oscillator (DCO), where the fundamental building block of the oscillator is an analog LC tank oscillator. Rather than using a standard ring oscillator, which is fundamentally a digital circuit, the LC tank oscillator was chosen for its precision and to reduce jitter. The first approach in designing the DCO involved using a digital to analog converter (DAC) to supply a control voltage to a voltage-controlled oscillator (VCO). This approach proved to be inadequate, for reasons discussed later in this report, yet offered insight and knowledge that became quite useful in the final DCO design. Finally, a digitally tuned capacitive network (DTCN) was implemented to provide a digital interface to the analog LC tank oscillator.