Numerical and experimental studies of resonators with reduced resonant   frequencies and small electrical sizes
  Methods on reducing resonant frequencies and electrical sizes of resonators are reported in this paper. Theoreti-cal and numerical analysis has been used and the results for the broadside-coupled resonators from both studies exhibit good agreement. Initial fabrication techniques are proposed and measurement results are compared with simulations. Further high resolution techniques have been envisaged to enhance the performance of the resona-tors. This class of small resonators with low resonant frequencies indicates a variety of applications in the design of microwave devices. 
T. Hao, J. Zhu, D.J. Edwards and C.J. Stevens