A review on quality factor enhanced on-chip microwave planar resonators

This paper reviews microwave on-chip resonators with emphasis on quality-factor (Q-factor), and techniques enhancing Q-factor. The review discusses both planar microstrip and waveguide structures, with the integration of the latter emerging as a substitute for the bulky and expensive non-planar waveguides. Despite their huge Q-factor the conventional waveguide does not support integration and miniaturisation. While the microstrips support miniaturisation and mass fabrication at low-cost, they are limited by low Q-factor due to high conductor and substrate losses. A study of Q-factor enhancing techniques for on-chip devices is presented, with an introduction of integrated waveguide structures. In addition, a summary of transitions between on-chip planar microstrips and planar waveguides is presented.