On using Magneto-static Responsive particles as switching elements to reconfigure microwave filters

This paper presents the use of novel Magneto-static Responsive Structures (MRSs) as switching elements in microwave filters to achieve frequency reconfigurability. A single MRS consisted of a small piece of substrate with a cavity drilled out of it. The cavity was then filled with microscopic magnetic particles and capped on both ends with copper tape. In the presence of a static magnetic field, the magnetic particles formed columns along the field lines and connected the two top and bottom conducting planes to form a short. In the absence of the magnetic field the columns collapsed, disconnecting the conducting plates resulting in an open switch. The theoretical design, optimization and performance of a single MRS as well as a reconfigurable filter using MRSs was simulated using the 3D full wave electromagnetic (EM) models in HFSS®. The laboratory prototypes with MRSs were then manufactured and attached to the reconfigurable band-pass filter prototype for validation. Measured results of the prototype filter showed good agreement with the simulations. Specifically, a 2.7 GHz center frequency with a 60 MHz bandwidth in the MRS `OFF' state and a 1.98 GHz center frequency with a 50 MHz bandwidth in the MRS `ON' state was observed. The simulated and measured insertion losses of the reconfigurable band-pass filter were 2.9 dB and 2.98 dB in the `OFF' and `ON' states, respectively. It was successfully shown that the proposed MRS can be used as an alternative switching technology in reconfigurable microwave filters in a frequency band from the 100 KHz - 3.0 GHz, with an additional benefit of not requiring directly connected biasing circuitry.