Systems and methods to selectively connect antennas to receive and backscatter 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 configured to receive radio frequency signals;
a receiver;
a diode coupled between the antenna and the receiver;
a bias circuit coupled to the diode and configured to adjust a bias status of the diode; and
a controller coupled to the bias circuit, wherein the controller is configured to adjust the bias status of the diode without short circuiting a predetermined impedance connected between the receiver and the antenna, causing the device to:
selective allow the radio frequency signals received by the antenna to reach the receiver; and
modulate data transmitted from the device via the antenna.
2. The device of claim 1 , further comprising:
a memory storing the data.
3. The device of claim 2 , wherein the diode changes a state of the antenna according to the bias status of the diode.
4. The device of claim 3 , wherein the controller adjusts a current in the bias circuit to adjust the bias status of the diode.
5. The device of claim 4 , wherein the bias circuit is a controllable current source.
6. The device of claim 3 , wherein the bias circuit is a transistor coupled between the diode and ground; and the controller controls a gate of the transistor.
7. The device of claim 6 , 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.
8. The device of claim 1 , wherein the bias circuit is controlled by the controller to selectively connect and disconnect the antenna to transmit the data.
9. The device of claim 1 , wherein the bias circuit is controlled by the controller to selectively connect the antenna to ground and disconnect the antenna from the ground to transmit the data via the antenna.
10. A device, comprising:
a receiver;
a plurality of antennas;
a plurality of diodes coupled between the receiver and the plurality of antennas respectively;
a plurality of bias circuits coupled to the plurality of diodes respectively, each of the plurality of bias circuits controllable to adjust a bias status of a respective diode of the plurality of diodes; and
a circuit configured to selectively couple a control signal to a selected bias circuit in the plurality of bias circuits without short circuiting a predetermined impedance connected between the receiver and the antennas, wherein:
the selected bias circuit is controllable to adjust a bias status of a first diode of the plurality of diodes;
the first diode is coupled to a first antenna of the plurality of antennas; and
the control signal is adjustable to change the bias status of the first diode in:
selective allowing radio frequency signals received by an antenna coupled to a diode to reach the receiver; and
modulating data transmitted from the device via the antenna.
11. The device of claim 10 , wherein each of the plurality of bias circuit is a transistor coupled between ground and a respective one of the plurality of diodes.
12. The device of claim 10 , wherein each of the plurality of bias circuit is a current controller connected to a respective one of the plurality of diodes.
13. The device of claim 12 , wherein the plurality of antennas comprise:
a conductive patch having a plurality of feed points;
a ground element; and
a dielectric layer coupled between the conductive patch and the ground element;
wherein the diodes are coupled to the feed points.
14. The device of claim 13 , wherein the diodes are mounted in vicinity of the feed points to which the diodes are connected.
15. The device of claim 14 , wherein the receiver and the circuit are integrated on a single semiconductor substrate.
16. A device, comprising:
a plurality of antennas;
a receiver;
a plurality of diodes coupled between the receiver and the plurality of antennas respectively;
a bias circuit shared by the plurality of diodes to adjust bias statuses of the diodes simultaneously; and
a controller coupled to the bias circuit, wherein the controller adjusts the bias statuses of the diodes, without short circuiting a predetermined impedance connected between the receiver and the antennas, in:
selective allowing radio frequency signals received by the antennas to reach the receiver; and
modulating data transmitted from the device via the antennas.
17. The device of claim 16 , wherein the bias circuit is an adjustable current source.
18. The device of claim 16 , wherein the plurality of antennas have different polarizations.
19. The device of claim 16 , wherein the plurality of diodes are mounted in vicinity of respective feed points to which the diodes are connected.
20. The device of claim 16 , wherein the receiver and the controller are integrated on a single semiconductor substrate.