Compact repeaters for wireless sensing

1. A repeater for wireless sensing, the repeater comprising:

a base substrate;

a front substrate orthogonal to the base substrate;

a rear substrate orthogonal to the base substrate;

a receive antenna formed on the front substrate configured to receive an interrogation signal transmitted by another device;

a bias network configured to connect the repeater to a sensor and modulate the interrogation signal based upon a parameter sensed by the sensor;

a frequency multiplier formed on the base substrate, the frequency multiplier being in communication with the receive antenna and configured to multiply the frequency of the interrogation signal by a multiplication factor; and

a transmit antenna formed on the rear substrate, the transmit antenna being in communication with the frequency multiplier and configured to retransmit the modulated interrogation signal at a multiplied frequency.

2. The repeater of claim 1 , wherein the receive antenna is a three-dimensional half-wave dipole antenna that comprises a first antenna element and a second antenna element, the first antenna element including a vertical portion formed on one side of the front substrate and the second antenna element including a vertical portion formed on the opposite side of the front substrate.

3. The repeater of claim 2 , wherein each antenna element of the receive antenna further comprises a dipole arm that extends laterally from its vertical portion.

4. The repeater of claim 3 , further comprising first and second lateral substrates that are orthogonal to the front substrate, wherein each dipole arm extends onto one of the lateral substrates.

5. The repeater of claim 4 . . . , wherein the dipole arms each terminate in a meandered portion and are anti-symmetrical to each other.

6. The repeater of claim 1 , wherein the transmit antenna is a three-dimensional half-wave dipole antenna that comprises a first antenna element and a second antenna element, the first antenna element including a vertical portion that is formed on one side of the rear substrate and the second antenna element including a vertical portion that is formed on the opposite side of the rear substrate.

7. The repeater of claim 6 , wherein each antenna element of the transmit antenna further comprises a dipole arm that extends laterally from its vertical portion.

8. The repeater of claim 7 , wherein the dipole arms each terminate in a vertical portion and are anti-symmetrical to each other.

9. The repeater of claim 1 , wherein the frequency multiplier is configured to double the frequency of the interrogation signal received by the receive antenna such that the retransmitted interrogation signal has a frequency that is twice the frequency of the received interrogation signal.

10. The repeater of claim 1 , wherein the frequency multiplier comprises a Schottky barrier diode.

11. The repeater of claim 1 , further comprising a first feeding network formed on the base substrate that connects the receive antenna to the frequency multiplier and a second feeding network formed on the base substrate that connects the transmit antenna to the frequency multiplier.

12. The repeater of claim 11 , wherein the feeding networks are formed on a first side of the base substrate and the repeater further comprises a ground plane that is formed on an opposite side of the base substrate, wherein the receive and transmit antennas are connected to the ground plane.

13. The repeater of claim 1 , wherein the front substrate and the rear substrate have been machined to remove excess material.

14. The repeater of claim 13 , wherein the portions of the front and rear substrates that do not support an electrical element have been machined away.

15. The repeater of claim 1 , wherein the bias network comprises a direct current bias network.

16. The repeater of claim 11 , wherein the bias network is coupled to the first feeding network.

17. A repeater for wireless sensing, the repeater comprising:

a base substrate;

a front substrate that is orthogonal to the base substrate;

first and second lateral substrates that are orthogonal to the front substrate;

a rear substrate that is orthogonal to the base substrate;

a receive antenna including a first antenna element and a second element, the first antenna element including a vertical portion formed on an inner side of the front substrate and a dipole arm that extends laterally outward from the vertical portion across the inner side and onto the first lateral substrate, the second antenna element including a vertical portion formed on an outer side of the front substrate and a dipole arm that extends laterally outward from the vertical portion across the outer side and onto the second lateral substrate;

a transmit antenna including a first antenna element and a second element, the first antenna element including a vertical portion formed on an inner side of the rear substrate and a dipole arm that extends laterally outward from the vertical portion across the inner side, the second antenna element including a vertical portion formed on an outer side of the rear substrate and a dipole arm that extends laterally outward from the vertical portion across the outer side;

a frequency multiplier provided on the base substrate;

a first feeding network formed on the base substrate that connects the first antenna element of the receive antenna to the frequency multiplier; and

a second feeding network formed on the base substrate that connects the first antenna element of the transmit antenna to the frequency multiplier.

18. The repeater of claim 17 , wherein the dipole arms of the receive antenna each terminate in a meandered portion and the dipole arms of the transmit antenna each terminate in a vertical portion.

19. The repeater of claim 18 , wherein the dipole arms of each antenna are anti-symmetrical to each other.

20. The repeater of claim 17 , wherein the front substrate and the rear substrate have been machined to remove the portions of the front and rear substrates that do not support an electrical element have been machined away.