Microwave tunable filter using ultra-thin magnetic film

The filter characteristics of magnetostatic surface wave propagating in a structure consisting of the strip-line antenna and a relatively thin YIG film are described. The performance theory of filter proposed here utilizes a peculiarity such as it is to be explained only in the passband characteristics of magnetostatic surface wave, when the external magnetic field and saturation magnetization of YIG film are given in the system. It was found that the loaded Q-value of filter on an ordinary magnetostatic surface wave transmission system composed of a stripline antenna with 200 μm width and a YIG film with 0.79 μm thick is about 1620 at s-band frequency.