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 to receive radio frequency signals;
a receiver;
a diode coupled between the antenna and the receiver; and
a circuit coupled to the diode, wherein
when in a receiving mode, the circuit is controlled to
forward bias the diode to cause the diode to provide a path for the radio frequency signals received by the antenna to reach the receiver, and
reverse bias the diode to cause the diode to prevent the radio frequency signals received by the antenna from reaching the receiver, and
when in a transmission mode, the circuit is controlled to transmit data by modulating backscatter of the antenna.
2. The device of claim 1 , wherein the circuit is configured to change a state of the antenna according to data to be transmitted.
3. The device of claim 2 , wherein the circuit comprises a current controller configured to selectively provide a forward bias current and change the state of the antenna.
4. The device of claim 3 , wherein the current controller comprises a transistor coupled between the diode and ground; the transistor has a gate; when the gate is at a first voltage, the transistor provides the forward bias current to the diode; when the gate is at a second voltage, the transistor stops the forward bias current.
5. The device of claim 4 , wherein the gate is configured to change an impedance between the antenna and the ground according to the data to be transmitted to change backscattering of the antenna.
6. The device of claim 4 , 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.
7. The device of claim 2 , wherein the antenna has a plurality of feed points for the receiver; and the diode is coupled to one of the plurality of feed points for the receiver; and the device further comprises:
a second diode coupled between the receiver and a second feed point of the plurality of feed points; and
a second circuit coupled to the second diode to selectively forward bias and reverse bias the second diode.
8. The device of claim 1 , wherein the circuit is configured to selectively connect and disconnect the antenna to transmit data.
9. The device of claim 1 , wherein the circuit is further configured to selectively connect the antenna to ground and disconnect the antenna from the ground to transmit 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 current source circuit coupled to the plurality of diodes; and
at least one controller coupled to the current source circuit, the at least controller configured to control the current source circuit to:
when in a receiving mode,
forward bias one or more first diodes of the diodes to allow radio frequency signals received via respective one or more first antennas of the antennas to reach the receiver, and
reverse bias one or more second diodes of the diodes to prevent radio frequency signals from propagating from one or more second antennas of the antennas to the receiver, and
when in a transmission mode, modulating grounding of one or more of the antennas to transmit data via backscattering.
11. The device of claim 10 , wherein the at least one controller comprises a plurality of transistors; wherein gates of the transistors are controllable to selectively forward bias the diodes and to selectively ground the antennas to modulate backscatter by the antennas.
12. The device of claim 10 , wherein the at least one controller comprises a plurality of current controllers coupled to the plurality of diodes respectively.
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.