The invention discloses a differential filter based on
artificial surface plasmon. The function of a differential wave filtering is achieved by means of a
metal grating ring and mutual
coupling and interference between a first straight
metal grating structure and a second straight
metal grating structure. The straight metal gratings and the
metal grating ring are metal straps which are printed on a medium substrate, the thickness of each metal strap is nearly zero, the size of each metal strap is small, the length and the height of a
unit structure are smaller than the operating
wavelength, and the thickness of the
unit structure is far smaller than the operating
wavelength.
Surface wave propagation can be bound in the size of deep sub-
wavelength surrounding the metal straps, and efficient transmission of energy can be achieved. A
dispersion curve of the metal surface can be changed by means of control over the depth, the width and the periodicity of a surface groove of a
metal grating structure and control over distance between each straight
metal grating and each metal grating, and the metal grating structure which meets the requirement of a working frequency is designed. A
coaxial line inner conductor which extends outward is taken as a metal line to stimulate surface
waves on the metal grating structure. The differential filter based on the
artificial surface plasmon has the advantages of being wide in bandwidth, not obvious in internal dispersion of a pass band, stable in performance, and applicable to different wave bands such as microwaves,
millimeter waves and Terahertz
waves by means of scaling of structural parameters.