Patent ID: 8508318

Claim:
A transmission line filter comprising: a plurality of ferroelectric bodies of the same shape arranged periodically in a periodical arrangement direction; a strip conductor connecting said plurality of ferroelectric bodies in said periodical arrangement direction; a plurality of paraelectric bodies having a dielectric constant lower than that of said plurality of ferroelectric bodies; a ground plane, wherein said plurality of paraelectric bodies are of the same shape and arranged in a same direction as said periodical arrangement direction of said plurality of ferroelectric bodies, wherein a dielectric composite layer including said plurality of ferroelectric bodies and said plurality of paraelectric bodies are layered and positioned between said strip conductor and said ground plane; and a voltage applying circuit connected to at least one of said plurality of ferroelectric bodies, wherein said voltage applying circuit applies a voltage to said at least one of said plurality of ferroelectric bodies to control a frequency of a stop band of said transmission line filter so that the voltage is applied in a direction in which said ground plane and said dielectric composite layer are layered.