Planar Waveguide, Waveguide Filter, and Antenna

A planar waveguide, comprising:

• a top printed circuit board (PCB) having a groove;
• a bottom PCB, wherein the groove and the bottom PCB form an air waveguide;
• multiple shielding metal blocks, each shielding metal block having an upper surface contacting the top PCB and a lower surface contacting the bottom PCB;
• a metal plate disposed on the upper surface of the top PCB;
• a plurality of microstrips disposed on a lower surface of the top PCB, wherein the microstrips are positioned at both ends of the groove and are disposed along an extension line of the groove and wherein the multiple shielding metal blocks are disposed along an extension direction of the microstrips and the groove and are positioned on both sides of the microstrips and the groove;
• and
• a first conversion piece configured to implement signal transmission between the microstrips and the air waveguide is further disposed between the microstrips and the bottom PCB under the groove;
• wherein a working barycentric frequency of the planar waveguide is f0;
• wherein a wavelength of an electromagnetic wave in the air under frequency f0 is λ=c/f0, where c is a velocity of light in the air;
• wherein a height Hb of the shielding metal blocks fulfills 0.75×λ/4≦Hb≦1.25×λ/4;
• wherein a width Wb of the shielding metal blocks fulfills λ/8≦Wb≦λ;
• and
• wherein a gap Wg between the multiple shielding metal blocks fulfills 0<Wg≦λ/2.