Millimeter-wave band communication device
Proposed is a millimeter-wave band communication device which does not generate spatial resonance in a cover shielding unnecessary radio waves from the outside. Disclosed is a millimeter-wave band communication device including: a substrate; a radio frequency circuit element for a millimeter-wave band provided on the substrate; and a cover made of a bulk material that covers at least a part of the radio frequency circuit element and a surface of the substrate, the cover being formed by blending a dielectric loss material in a base.
1. A millimeter-wave band communication device comprising:
a substrate;
a radio frequency circuit element for a millimeter-wave band provided on the substrate; and
a non-metallic cover made of a bulk material that covers at least a part of the radio frequency circuit element and a surface of the substrate,
wherein the cover is formed by blending a dielectric loss material in a base material.
2. The millimeter-wave band communication device according to claim 1 , wherein
the dielectric loss material is graphite.
3. The millimeter-wave band communication device according to claim 1 , wherein
a radio wave reflection efficiency of the cover is set to 90% or less.
4. The millimeter-wave band communication device according to claim 1 , wherein
a radio wave reflection efficiency of the cover is set to between 50% and 90%.
5. The millimeter-wave band communication device according to claim 1 , wherein
the cover is integrally molded using a resin as the base material.
6. The millimeter-wave band communication device according to claim 1 , wherein
a compounding ratio of the dielectric loss material compounded with the cover is between 20% and 80% of an entirety of the cover or in an average mass ratio.
7. The millimeter-wave band communication device according to claim 1 , wherein
the cover has a volume resistivity of 20 Ω·cm or higher.
8. The millimeter-wave band communication device according to claim 1 , wherein
a compounding concentration of the dielectric loss material is lower on a side of the cover opposing the substrate.
9. The millimeter-wave band communication device according to claim 1 , wherein
a compounding concentration of the dielectric loss material is higher on a side closer to a thickness center of the cover.
10. The millimeter-wave band communication device according to claim 1 , wherein
the cover is a rectangular parallelepiped, has a thickness T in a direction perpendicular to the substrate, has a concave portion so as to cover the radio frequency circuit element, and
a distance D between a ceiling of the concave portion of the cover and the substrate is smaller than the thickness T and larger than a height H of the radio frequency circuit element.
11. The millimeter-wave band communication device according to claim 1 , further comprising:
a radio frequency line provided on the substrate surface and connected to the radio frequency circuit element; and
a groove structure formed in the cover so as to prevent contact between the radio frequency line and the cover.
12. The millimeter-wave band communication device according to claim 11 , wherein
a width of the groove structure at a cross section intersecting with a radio wave propagation direction of the radio frequency line is set to be equal to or less than a wavelength λ of a millimeter wave use frequency.
13. The millimeter-wave band communication device according to claim 11 , further comprising:
an antenna provided on a side of the radio frequency line opposite to the radio frequency circuit element; and
a dielectric lens made of an insulator,
wherein the cover and the dielectric lens are integrally formed.
14. The millimeter-wave band communication device according to claim 11 , wherein
an antenna provided on a side of the radio frequency line opposite to the radio frequency circuit element; and
a horn antenna configured by compounding a resin with a dielectric loss material,
wherein the cover and the horn antenna are integrally configured.
15. The millimeter-wave band communication device according to claim 14 , wherein
the concave portion of the cover is set to have a depth of λ/4 so as to function as a back short of a line converter of the radio frequency line.
16. The millimeter-wave band communication device according to claim 1 , wherein the cover does not include an outer metal layer and is not metal plated.