RF backscatter transmission with zero DC power consumption
View Patent ↗A method for minimizing power consumption in a wireless device which utilizes backscatter transmission in half-duplex mode, wherein a switching device is interposed between an antenna and a transmitter-receiver, and the switching device is capable of causing the antenna load impedance characteristic to be either a short, a value which substantially matches the antenna impedance, or an open, depending on the portion of the half-duplex mode.
1. In a transmitter-receiver circuit, for transmitting and receiving through an antenna, a method of minimizing power consumption comprising:
setting an antenna load impedance to match the impedance of the antenna; and
varying the antenna load impedance between a short impedance and a matching impedance, wherein the circuit is capable of operating in backscatter mode;
wherein the varying step includes varying the antenna load impedance in the range between short impedance, matching, and open impedance.
2. The method of claim 1 wherein the varying step comprises switching the short and the matching impedances into and out of the circuit.
3. The method of claim 2 wherein the switching step includes applying a voltage to the gate of a FET.
4. The transmitter-receiver circuit of claim 1 wherein the circuit is capable of half-duplex communication.
5. A transmitter-receiver circuit comprising:
a transmitter-receiver for transmitting and receiving through an antenna having an impedance;
switching logic coupled between the antenna and the transmitter-receiver, the switching logic adapted to establish an antenna load impedance which matches the antenna impedance during a listening portion of a half-duplex cycle, and, during the transmit portion of the half-duplex cycle, and, to vary the antenna load impedance between a short and a match to the antenna impedance,
wherein the transmitter-receiver is capable of operating in backscatter mode; and
generating a baseband having a phase and magnitude and varying the phase and magnitude thereof.
6. The transmitter-receiver circuit of claim 5 wherein the transmitter-receiver is a half-duplex transmitter-receiver.
7. A transmitter-receiver circuit, as recited in claim 5 , wherein the switching logic includes a Field Effect Transistor (FET) having a gate to which voltage is applied for causing the establishing of the load impedance.
8. A transmitter-receiver circuit, as recited in claim 5 , wherein the FET is N-channel, P-channel, enhancement or depletion mode transistor.
9. A transmitter-receiver circuit, as recited in claim 5 , wherein the FET is a MOSFET, IgFET or JFET transistor.
10. A transmitter-receiver circuit, as recited in claim 5 , wherein the FET is made of silicon, GaAs, InFaAs, SOI, or plastic transistors.
11. A transmitter-receiver circuit comprising:
a transmitter-receiver for transmitting and receiving through an antenna capable of operating in half-duplex mode at a baseband having a phase and a magnitude; and
logic for varying the magnitude and the phase of the baseband as applied to the antenna, wherein the transmitter-receiver is capable of operating in backscatter mode;
wherein the logic can vary the antenna load impedance in the range between short impedance, matching, and open impedance.
12. The transmitter-receiver circuit of claim 11 further including switching logic coupled between the antenna and the transmitter-receiver for varying an antenna load impedance in accordance with portions of the half-duplex cycle.
13. A transmitter-receiver circuit, as recited in claim 11 , further including an antenna.
14. A transmitter-receiver circuit, as recited in claim 11 , wherein the transmitter-receiver is a half-duplex transmitter-receiver.
15. A transmitter-receiver circuit, as recited in claim 11 , wherein the logic includes a Field Effect Transistor (FET) having a gate to which voltage is applied.
16. A transmitter-receiver circuit, as recited in claim 15 , wherein the FET is N-channel, P-channel, enhancement or depletion mode transistor.
17. In a transmitter-receiver circuit, for transmitting and receiving through an antenna, a method of minimizing power consumption comprising:
setting an antenna load impedance to match the impedance of the antenna;
varying the antenna load impedance between a short impedance and a matching impedance, wherein the circuit is capable of operating in backscatter mode; and
generating a baseband having a phase and magnitude and varying the phase and magnitude thereof.