Transmitarray unit cell for a reconfigurable antenna

1. A transmitarray unit cell for an antenna reconfigurable at an operating frequency, including:

a receive patch antenna, intended to receive an incident wave;

a transmit patch antenna intended to transmit the incident wave with a phase shift, and comprising first and second radiation surfaces separated from each other by a separation area so as to be electrically isolated;

a phase-shift circuit configured to introduce the phase shift, and comprising switches, each having an on, respectively off, state, wherein the corresponding switch allows, respectively blocks, the flowing of a current between the first and second radiation surfaces of the transmit patch antenna;

a ground plane having the receive patch antenna and the transmit patch antenna arranged on either side thereof;

a first printed circuit board comprising a first surface provided with the receive patch antenna and a second opposite surface provided with the ground plane;

a wafer of a semiconductor material, electrically isolated from the ground plane, and comprising a first surface provided with the first and second radiation surfaces of the transmit patch antenna;

wherein the switches are formed at the first surface of the wafer, in the separation area, monolithically with the transmit patch antenna.

2. The transmitarray unit cell according to claim 1 , including a second printed circuit board comprising a first surface assembled on the ground plane, and a second opposite surface; and wherein the wafer is assembled to the second surface of the second printed circuit board.

3. The transmitarray unit cell according to claim 2 , including a substrate of a dielectric material assembled to the second surface of the second printed circuit board; and wherein the substrate includes a cavity shaped to receive the wafer.

4. The transmitarray unit cell according to claim 2 , wherein the phase-shift circuit includes a first assembly of electrically-conductive tracks arranged at the second surface of the second printed circuit board to bias the switches.

5. The transmitarray unit cell according to claim 4 , wherein the phase-shift circuit includes:

a second assembly of electrically-conductive tracks, arranged at the first surface of the second printed circuit board to bias the switches;

vias formed in the second printed circuit board to connect the first and second assemblies of electrically-conductive tracks.

6. The transmitarray unit cell according to claim 2 , wherein the second surface of the second printed circuit board includes bump contacts; and wherein the wafer includes solder bumps soldered to the bump contacts to assemble the wafer to the second printed circuit board.

7. The transmitarray unit cell according to claim 6 , wherein the phase-shift circuit includes a first assembly of electrically-conductive tracks arranged at the second surface of the second printed circuit board to bias the switches; wherein the bump contacts are electrically connected to the first assembly of electrically-conductive tracks, and wherein the switches are electrically connected to the solder bumps.

8. The transmitarray unit cell according to claim 2 , wherein the second surface of the second printed circuit board includes at least one cavity formed opposite the transmit patch antenna.

9. The transmitarray unit cell according to claim 1 , wherein each switch is a micro-electromechanical system including:

a fixed actuation electrode, formed at the first surface of the wafer;

a membrane, formed at the first radiation surface of the transmit patch antenna, and mobile between:

a first position, corresponding to the on state, where the membrane is in contact with the second radiation surface of the transmit patch antenna; and

a second position, corresponding to the off state, where the membrane is distant from the second radiation surface of the transmit patch antenna.

10. The transmitarray unit cell according to claim 9 , including an encapsulation layer arranged to encapsulate each micro-electromechanical system, the encapsulation layer being formed monolithically with the corresponding micro-electromechanical system.

11. The transmitarray unit cell according to claim 1 , wherein each switch includes:

an electrically-conductive element comprising a first portion formed at the first surface of the wafer, in contact with the first radiation surface of the transmit patch antenna, and a second portion extending opposite the second radiation surface of the transmit patch antenna;

a layer of a phase-change material, arranged between the second radiation surface of the transmit patch antenna and the second portion of the electrically-conductive element, the phase-change material having a crystal phase corresponding to the on state, and an amorphous phase corresponding to the off state.

12. The transmitarray unit cell according to claim 11 , wherein the phase-change material is selected from the group comprising GeTe, Ge 2 Sb 2 Te 5 .

13. The transmitarray unit cell according to claim 1 , wherein the wafer has a resistivity greater than or equal to 2,000 Ω·cm.

14. The transmitarray unit cell according to claim 1 , wherein the semiconductor material of the wafer is based on silicon.

15. The transmitarray unit cell according to claim 1 , wherein the operating frequency is in the range from 30 GHz to 110 GHz.

16. An antenna reconfigurable at an operating frequency, including a transmitarray comprising a plurality of transmitarray unit cells according to claim 1 .