Systems and methods to selectively connect antennas to communicate via radio frequency signals
Systems and methods to selectively attach and control antennas via diodes. In one embodiment, a system includes: a reader having a plurality of reader antennas of different polarizations to transmit radio frequency signals; and at least one radio frequency device. The radio frequency device includes: a plurality of tag antennas of different polarizations; a plurality of diodes coupled to the plurality of tag antennas respectively; a receiver coupled to the plurality of diodes to receive the radio frequency signals from the tag antennas when the diodes are forward biased; and a set of one or more current controllers coupled to the plurality of diodes. In a receiving mode the controllers selectively forward bias the diodes to receive the signals from the reader. In a transmitting mode the controllers selectively change the state of the tag antennas to transmit data via backscattering the radio frequency signals.
1. A device, comprising:
an antenna;
a receiver configured to receive radio frequency signals via the antenna;
a first circuit having a diode coupled between the antenna and the receiver, the diode having an adjustable bias status; and
a second circuit configured to control the first circuit via the adjustable bias status to selectively allow the radio frequency signals received by the antenna to reach the receiver without short circuiting between the receiver and the antenna.
2. The device of claim 1 , wherein the antenna comprise:
a conductive patch having a feed point;
a ground element; and
a dielectric layer coupled between the conductive patch and the ground element;
wherein the diode is coupled to the feed point.
3. The device of claim 2 , wherein the diode is mounted in vicinity of the feed point.
4. The device of claim 3 , wherein the receiver and the second circuit are integrated on a single semiconductor substrate.
5. A device, comprising:
a receiver configured to receive radio frequency signals via an antenna;
a first circuit coupled between the antenna and the receiver, the first circuit comprising a diode having an adjustable bias status; and
a second circuit configured to control the first circuit via the adjustable bias status to selectively allow the radio frequency signals received by the antenna to reach the receiver without short circuiting between the receiver and the antenna.
6. The device of claim 5 , wherein the first circuit further comprises:
a bias circuit coupled to the diode connected between the antenna and the receiver, the bias circuit configured to adjust the bias status according to a control signal from the second circuit.
7. The device of claim 6 , wherein the second circuit comprises a logic circuit.
8. The device of claim 6 , wherein the second circuit comprises an analog circuit.
9. The device of claim 6 , wherein the second circuit comprises a controller.
10. The device of claim 9 , further comprising:
a memory storing data;
wherein the controller is further configured to control the bias circuit to modulate, according to the data, signals transmitted from the device via the antenna.
11. The device of claim 10 , wherein the diode is configured to change a state of the antenna according to the bias status.
12. The device of claim 11 , wherein the controller is configured to adjust a current in the bias circuit to adjust the bias status.
13. The device of claim 12 , wherein the bias circuit includes a controllable current source.
14. The device of claim 11 , wherein the bias circuit includes a transistor coupled between the diode and ground; and the controller is configured to control a gate of the transistor.
15. The device of claim 14 , wherein the transistor is configured to alternate, according to the data to be transmitted, between connecting the antenna to the ground and disconnecting the antenna from the ground.
16. The device of claim 10 , wherein the controller is configured to control the bias status to selectively connect and disconnect the antenna to transmit the data.
17. The device of claim 5 , wherein the second circuit is configured to control the bias status to selectively connect the antenna to ground and disconnect the antenna from the ground to transmit data via the antenna.
18. A method, comprising:
receiving radio frequency signals in an antenna of a device, wherein a first circuit of the device has a diode coupled between the antenna and a receiver;
adjusting, by the first circuit, a bias status of the diode;
controlling, by a second circuit of the device, the first circuit via the bias status of the diode to selectively allow the radio frequency signals received in the antenna to reach the receiver without short circuiting between the receiver and the antenna.
19. The method of claim 18 , further comprising:
receiving, in the first circuit having a bias circuit, a control signal from the second circuit;
adjusting, by the bias circuit according to the control signal, the bias status of the diode.
20. The method of claim 19 , further comprising:
storing data in a memory of the device;
controlling the bias circuit to modulate, according to the data, signals transmitted from the device via the antenna.