Tunable microwave filters using nanoparticles and thin films of Ferroic materials

Tunable filters are reported using low coercivity ferromagnetic nanoparticles or ferroelectric thin films, which are attractive at RF frequencies due to their tunable capabilities using magnetic and electric control fields. This paper employs the soft ferromagnetic Fe 60 Co 40 nanoparticles with relative permeability of larger than 8 and loss tangent smaller than 0.1 to realize tunable RF filters for IEEE802.11g frequency band applications. This nanoparticle material was employed in design of 3 rd order annular ring at 2.4GHz that resulted in about 200MHz tuning, when 0.15T external magnetic flux is applied. A 5 th order annular ring filter design was also employed for comparison. A similar approach is also extended to design and predicted performance of manganese-doped Ba 0.8 Sr 0.2 TiO 3 (BST) soft ferroelectric thin films based filters, whereby a high relative permittivity of larger than 140 and loss tangent smaller than 0.02 is reported for the BST thin film. The simulated performance of the BST thin film resulted in 860MHz tuning using a 40V/μm applied electric field intensity.