US 12,255,398 B2
Radio wave absorber
Motoki Masaki, Tokyo (JP); and Fumiaki Baba, Tokyo (JP)
Assigned to MITSUBISHI ELECTRIC CORPORATION, Tokyo (JP)
Appl. No. 17/789,222
Filed by Mitsubishi Electric Corporation, Tokyo (JP)
PCT Filed Feb. 27, 2020, PCT No. PCT/JP2020/008024
§ 371(c)(1), (2) Date Jun. 27, 2022,
PCT Pub. No. WO2021/171479, PCT Pub. Date Sep. 2, 2021.
Prior Publication US 2023/0054631 A1, Feb. 23, 2023
Int. Cl. H01Q 17/00 (2006.01); H01F 1/34 (2006.01); H05K 9/00 (2006.01)
CPC H01Q 17/004 (2013.01) [H01F 1/344 (2013.01); H05K 9/0081 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A radio wave absorber comprising:
a first radio wave absorbing layer having a first radio wave absorbing surface of the radio wave absorber, the first radio wave absorbing layer including:
first hexagonal ferrite particles; and
a holding material filled with the first hexagonal ferrite particles; and
a second radio wave absorbing layer having a second radio wave absorbing surface of the radio wave absorber, the second radio wave absorbing layer being located opposite to the first radio wave absorbing surface, the second radio wave absorbing layer including:
second hexagonal ferrite particles; and
a holding material filled with the second hexagonal ferrite particles, wherein
the second radio wave absorbing layer is directly stacked on the first radio wave absorbing layer,
the second hexagonal ferrite particles are larger than the first hexagonal ferrite particles in particle size,
each of the first hexagonal ferrite particles have a first particle size of 0.05 μm or more and less than 1 μm,
each of the second hexagonal ferrite particles have a second particle size of 5 μm or more and 100 μm or less,
the first hexagonal ferrite particles including first single-domain particles,
the second hexagonal ferrite particles including second single-domain particles,
a proportion of an area of the first single-domain particles and the second single-domain particles to an area of the first and second hexagonal ferrite particles being 30 percent or more, and
wherein the radio wave absorber is configured to absorb noise in the 28-GHz band and the 79-GHz band.