This paper presents results of a simulation of electrical circuits for microwave oscillators conducted within the 'Microwave Office' RF design software suite. The purpose of the simulation and optimization is to minimize the phase noise of a millimetre wave frequency synthesizer and to find optimal designs for reference oscillators and voltage controlled oscillator circuits. The effects of incorporating bipolar and field-effect transistor circuits on the phase noise, various circuits supplying bias voltage to the base and gate of the transistor, methods of incorporating quartz crystals and frequency tuning methods of voltage controlled oscillator circuits have been studied. The low phase noise reference oscillator and millimetre wave voltage controlled oscillator circuits are presented in this article.