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

Abstract

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.