Recent advances in microwave test equipment through the use of microwave sources employing Direct Digital Synthesis (DDS) techniques enable frequencies up to 67GHz to be achieved. When these are combined with state-of-the-art Vector Network Analyser (VNA) receivers, new opportunities are opened up to develop current and voltage waveform measurement systems, including active load-pull systems, that operate at very high frequencies. The major technical hurdle that prevents this from being possible is the provision of an accurate, wide-band phase reference which is required to convert a frequency domain VNA into a time domain receiver capable of handling current and voltage waveforms. Attempts have been made to solve this issue through the development of new types of phase reference standards, however all of the approaches tried to date have been severely limited in their frequency of operation. This research project would therefore look into the feasibility of developing a new type of phase reference that is not frequency limited, but could in principle be used to frequencies up to 67GHz and beyond.