Analysis of Spiral Resonator Filters

S.P. Yushanov, J.S. Crompton, and K.C. Koppenhoeffer
AltaSim Technologies

As the world becomes more digital, there is growing demand for advanced wireless systems. Increasingly high data rate transmission systems mean that components like microwave filters must fit into smaller and smaller spaces, and multiple filters need to be integrated into compact designs. Engineers are challenged to meet a filter's specific passband frequencies and quality requirements within the system’s geometrical and topological constraints.

AltaSim Technologies, a certified consultant of COMSOL, helps engineers to develop cost-effective solutions to improve their products and processes by combining engineering technology with advanced multiphysics analysis. To address this challenge, AltaSim created a model that is composed of two unit cells of electrically small artificial magnetic metamaterials formed with the direct connection of two concentric Hilbert fractal curves. The filter's operation is based on the excitation of two electrically-coupled fractal spiral resonators through direct connection with a feeding line.

They computed the scattering matrix (S-matrix) to describe how the input signal interacts with the device that satisfies its passband frequencies, which offers significantly reduced size compared to conventional resonators. COMSOL Multiphysics, combined with the RF Module, was able to assess the performance of the filter within the constraints of the geometry, prior to fabrication and integration into operating circuits.

Electric field at a frequency below the resonant frequency.