Millimeter-wave waveguide

1. A millimeter-wave waveguide comprising at least one strip, a sheath surrounding the at least one strip, and at least four ribs connecting the at least one strip to the sheath, said at least one strip, said sheath, and said at least four ribs being made of a dielectric material having a dielectric constant in the range from 1 to 4;

wherein the sheath, the at least one strip, and the at least four ribs define cavities filled with a gas, with a gas mixture, with a fluid, or with a solid; each of the gas, the gas mixture, the fluid, and the solid having a dielectric constant smaller than that of the dielectric material, and

wherein the at least one strip is configured for propagating electromagnetic waves received from an antenna when the antenna is aligned with the at least one strip.

2. The millimeter-wave waveguide of claim 1 , wherein the at least four ribs are parallel.

3. The millimeter-wave waveguide of claim 1 , comprising at least two strips of said dielectric material, the sheath surrounding the at least two strips, the ribs connecting the at least two strips to one another and to the sheath.

4. The millimeter-wave waveguide of claim 3 , wherein the at least two strips are parallel.

5. The millimeter-wave waveguide of claim 1 , wherein the millimeter-wave waveguide is made of a dielectric material having a dielectric constant in the range from 2 to 4.

6. The millimeter-wave waveguide of claim 1 , wherein the millimeter-wave waveguide is made of a plastic material, particularly polytetrafluoroethylene, polypropylene, or polystyrene.

7. A device for transmitting first millimeter waves comprising the millimeter-wave waveguide of claim 1 and at least four first antennas, each of the at least four first antennas being capable of transmitting and receiving the first millimeter waves, each end of the millimeter-wave waveguide being in contact with two of said at least four first antennas.

8. The device of claim 7 , wherein said two of said at least four first antennas at each end of the waveguide are distant from each other by a length greater than or equal to a half transmission wavelength of the at least four first antennas.

9. The device of claim 7 , wherein each of the at least four first antennas has a wavelength in the order of the wavelength of the first millimeter waves transmitted by the first antenna.

10. The device of claim 7 , comprising at least two second antennas, one of the at least two second antennas being in contact with the millimeter-wave waveguide at one of the ends of the millimeter-wave waveguide and another second antenna of the at least two second antennas being in contact with the millimeter-wave waveguide at the other end of the millimeter-wave waveguide, each of the at least two second antennas being capable of transmitting and of receiving second millimeter waves having a polarization perpendicular to within 10% to a polarization of the first millimeter waves.

11. The device of claim 7 , wherein the first millimeter waves have a frequency in a range from 30 GHz to 300 GHz.