Microwave planar sensor using PCB cavity packaging process

1. A microwave planar sensor for detecting movement of a target in a detection area, comprising:

a microwave board, comprising:

an oscillator/mixer layer, comprising an oscillator configured to generate at least one microwave signal and a signal mixer electrically coupled to the oscillator, the signal mixer configured to combine a microwave signal generated by the oscillator and a reflected signal reflected by the target, thereby generating an intermediate frequency signal having a Doppler frequency;

an antenna layer, comprising a transmit antenna coupled to the oscillator for transmitting a microwave signal generated by the oscillator into the detection area and a receive antenna coupled to the signal mixer for receiving the reflected signal; and

a ground layer disposed between the oscillator/mixer layer and the antenna layer when the oscillator/mixer layer and the antenna layer are bonded together, and

a support board, comprising:

a top surface bonded to the oscillator/mixer layer of the microwave board through a first metal layer coated on the top surface; and

a continuous cavity extending from the top surface for accommodating the oscillator and the mixer of the oscillator/mixer layer, the surface of the cavity coated with a second metal layer.

2. The microwave planar sensor of claim 1 , wherein the oscillator comprises a power distributor disposed between the oscillator and the transmit antenna and between the oscillator and the mixer.

3. The microwave planar sensor of claim 2 , wherein the transmit antenna comprises a microstrip and the power distributor comprises a corresponding microstrip, said microstrips substantially overlying each other when the oscillator/mixer layer and the antenna layer are bonded together.

4. The microwave planar sensor of claim 2 , wherein the receive antenna comprises a microstrip and the mixer comprises a corresponding microstrip, said microstrips substantially overlying each other when the oscillator/mixer layer and the antenna layer are bonded together.

5. The microwave planar sensor of claim 3 , wherein the ground layer comprises a first slot to provide coupling interface between the microstrip of the transmit antenna and the corresponding microstrip of the power distributor.

6. The microwave planar sensor of claim 4 , wherein the ground layer comprises a second slot to provide coupling interface between the microstrip of the receive antenna and the corresponding microstrip of the mixer.

7. The microwave planar sensor of claim 1 , wherein the continuous cavity comprises a first cavity for accommodating the mixer and a second cavity for accommodating the oscillator.

8. The microwave planar sensor of claim 7 , wherein the first cavity and the second cavity are in communication through a groove.

9. The microwave planar sensor of claim 1 , wherein oscillator/mixer layer comprises at least one conductive via, electrically coupled to the first metal layer and the ground layer.

10. The microwave planar sensor of claim 1 , wherein the microwave board is made of a non-Teflon material.

11. The microwave planar sensor of claim 1 , wherein the support board is made of a non-Teflon material.

12. The microwave planar sensor of claim 1 , wherein the continuous cavity extends through the support board to provide a through cavity.

13. The microwave planar sensor of claim 12 , farther comprising a baseboard coupled to a bottom surface of the support board.

14. The microwave planar sensor of claim 13 , wherein the baseboard comprises a top surface bonded to the bottom surface of the support board through a third metal layer coated on the top surface of the base board.

15. The microwave planar sensor of claim 13 , wherein the baseboard comprises a first sub-board and a second sub-board, movable relative to one another, the first sub-board including a top surface bonded to the bottom surface of the support board through a fourth metal layer coated on the top surface of the first sub-board.

16. The microwave planar sensor of claim 15 , wherein the baseboard comprises at least one connector disposed between the first sub-board and the second sub-board, the connector configured adjustable to change the detecting angel of the sensor.

17. The microwave planar sensor of claim 16 , wherein the connector comprises a post having an outer thread, and a block having an inner thread mating with the outer thread, such that the block is movable along the post through the mating of the outer thread and the inner thread.

18. The microwave planar sensor of claim 17 , wherein an end of the first sub-board is connected to a corresponding end of the second sub-board, and the connector is positioned adjacent to the opposite ends of the first sub-board and the second sub-board for tilting the first sub-board and the second sub-board relative to one another.

19. The microwave planar sensor of claim 16 , wherein the baseboard comprises a tuning screw for adjusting the operative frequency of the sensor.

20. The microwave planar sensor of claim 19 , wherein the baseboard comprises a metal base associated with the tuning screw, the metal base soldered to the first sub-board.