Methods and apparatus for multi-frequency beamforming

• US 10,693,544 B2
• Filed: 04/23/2019
• Issued: 06/23/2020
• Est. Priority Date: 04/23/2018
• Status: Active Grant

• Current Assignee: Brigham and Women's Hospital Incorporated, Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Ma, Yunfei, Luo, Zhihong, Steiger, Christoph, Traverso, Carlo Giovanni, Adib, Fadel
• Primary Examiner(s): Patel, Dhaval V
• Application Number:
  US16/391,740
• Publication Number:
  US 20190326970A1
• Time in Patent Office: 427 Days
• CPC Class Codes: G06K 7/10217 parameter settings controlling the transmission power of the interrogator
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H04B 13/005 Transmission systems in which the medium consists of the human body
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer
• CPC Class Codes: H04B 7/0617 for beam forming

Abstract

Multiple antennas of a beamformer may simultaneously transmit wireless signals at different frequencies. The signals may comprise synchronized, identical wireless commands, each at a different carrier frequency. The transmitted signals may constructively and destructively interfere with each other at a receiver antenna, to form a beat signal. When the transmitted signals constructively interfere, the beat signal may cause a voltage in the receiver to exceed a threshold voltage. The threshold voltage may be a minimum voltage at which a device, which is operatively connected to the receiver antenna, is able to perform energy harvesting or wireless communication. The beamformer may operate under blind channel conditions, because the transmitted frequencies may be selected in such a way as to maximize peak power delivered under all possible channel conditions. The beamformer may deliver wireless power to a sensor or actuator that is located deep inside bodily tissue.

Claims

1. A system comprising a beamformer, wherein:

(a) the beamformer includes a first set of antennas; and

(b) the beamformer is configured to transmit a first set of wireless signals from the first set of antennas during a period of time, in such a way that

(i) each antenna in the first set of antennas transmits a specific signal in the first set of signals, which specific signal is different than that transmitted by any other antenna in the first set of antennas, at least because the specific signal has a carrier frequency that is different than that of each other signal in the first set of signals;

(ii) the first set of signals has a distribution of carrier frequencies; and

(iii) the distribution of carrier frequencies maximizes peak power received at a spatial position external to the beamformer, which peak power occurs during a subperiod of the period of time, which subperiod occurs while constructive interference of the signals at the spatial position is at a global maximum for the period of time.

2. The system of claim 1, wherein the system also includes a backscatter node that is located at the spatial position.

3. The system of claim 1, wherein:

(a) the system also includes a backscatter node that is located at the spatial position;

(b) the peak power exceeds a threshold power; and

(c) the backscatter node is configured to harvest power only when received power at the backscatter node is greater than the threshold power.

4. The system of claim 1, wherein the system also includes a radio frequency identification tag that is located at the spatial position.

5. The system of claim 1, wherein:

(a) the system also includes a backscatter node that is located at the spatial position; and

(b) the system is configured to transmit a wireless signal that encodes a command (command signal) in such a way that received power of the command signal at the backscatter node is within a range of amplitudes, which range of amplitudes consists of amplitudes at which the backscatter node is configured to decode the command signal.

6. The system of claim 1, wherein the system is configured to transmit a wireless command in such a way that received power at the spatial position exceeds a specified threshold at all times throughout the command.

7. The system of claim 1, wherein the system also comprises a transceiver, which transceiver is configured to transmit and receive signals at a carrier frequency that is different than that of each signal in the first set of signals.

8. The system of claim 1, wherein:

(a) the system also comprises a transceiver, which transceiver is configured to transmit an additional signal at a carrier frequency that is different than that of each signal in the first set of signals;

(b) the first set of antennas modulate the first set of signals by a first modulation and simultaneously the transceiver modulates the additional signal by a second modulation; and

(c) the first modulation and the second modulation are identical to each other throughout the period of time.

9. The system of claim 8, wherein the first and second modulations each comprise pulse-width modulation.

10. The system of claim 1, wherein:

(a) the system also comprises a transceiver, which transceiver is configured to transmit an additional signal at a carrier frequency that is different than that of each signal in the first set of signals;

(b) the first set of antennas modulate the first set of signals by a first modulation and simultaneously the transceiver modulates the additional signal by a second modulation; and

(c) the first modulation and the second modulation are different from each other.

11. The system of claim 10, wherein the second modulation comprises a constant modulation.

12. The system of claim 1, wherein:

(a) the system also comprises a transceiver, which transceiver is configured to transmit an additional signal at a carrier frequency that is different than that of each signal in the first set of signals; and

(b) the first set of antennas modulate carrier frequencies of the first set of signals while the additional signal is not modulated.

13. The system of claim 1, wherein:

(a) the system also includes one or more computers;

(b) the one or more computers are programmed

(i) to calculate an estimate of phase of a signal that reflects from the spatial position and that is received by a particular antenna of the system, and

(ii) based on the estimate of phase, to cause a second set of antennas of the system to transmit a second set of wireless signals during a second period of time, in such a way that

(A) each antenna in the second set of antennas transmits a specific signal in the second set of signals, which specific signal is different than that transmitted by any other antenna in the second set of antennas, at least because the specific signal has a phase that is different than that of each other signal in the second set of signals, and

(B) constructive interference of the second set of signals causes received power at the spatial position to exceed a threshold during a portion of the second period of time;

(c) the first and second set of antennas may, but do not necessarily, overlap entirely or partially; and

(d) the particular antenna may be, but is not necessarily, a member of the first or second sets of antennas.

14. The system of claim 1, wherein the spatial position is at a receiver antenna of an artificial sensor located inside a living organism.

15. The system of claim 1, wherein:

(a) the system also includes (i) one or more computers and (ii) at least one antenna that is configured to receive signals (received signals), which received signals are reflections from a group of radio frequency identification (RFID) tags; and

(b) the one or more computers are programmed to analyze the received signals to determine spatial coordinates and identity of the RFID tags.

16. The system of claim 1, wherein:

(a) the system also includes one or more computers; and

(b) the one or more computers are programmed to perform an algorithm that causes the beamformer to transmit the first set of wireless signals, which algorithm does not take, as an input, data that specifies or is computationally derived from phase or amplitude of any wireless signal that has reflected from the spatial position.

17. A system comprising multiple transmitters, wherein:

(a) the multiple transmitters include a first set of antennas; and

(b) the multiple transmitters are configured to transmit a first set of wireless signals from the first set of antennas during a period of time, in such a way that

(i) each antenna in the first set of antennas transmits a specific signal in the first set of signals, which specific signal is different than that transmitted by any other antenna in the first set of antennas, at least because the specific signal has a carrier frequency that is different than that of each other signal in the first set of signals;

(ii) the first set of signals has a distribution of carrier frequencies; and

(iii) the distribution of carrier frequencies maximizes peak power received at a receiver, which peak power occurs during a subperiod of the period of time, which subperiod occurs when constructive interference of the signals at the receiver is at a global maximum for the period of time.

18. A system comprising a beamformer, wherein:

(a) the beamformer includes a first set of transmitters; and

(b) the beamformer is configured to transmit a first set of wireless signals from the first set of transmitters during a period of time, in such a way that

(i) each transmitter in the first set of transmitters transmits a specific signal in the first set of signals, which specific signal is different than that transmitted by any other transmitter in the first set of transmitters, at least because the specific signal has a carrier frequency that is different than that of each other signal in the first set of signals;

(ii) the first set of signals has a distribution of carrier frequencies; and

(iii) the distribution of carrier frequencies maximizes peak power received at a spatial position external to the beamformer, which peak power occurs during a subperiod of the period of time, which subperiod occurs while constructive interference of the signals at the spatial position is at a global maximum for the period of time.

19. The system of claim 18, wherein the wireless signals comprise electromagnetic radiation.

20. The system of claim 18, wherein the wireless signals comprise visible light or infrared light.

21. The system of claim 18, wherein the wireless signals comprise pressure waves.

22. The system of claim 18, wherein the wireless signals comprise sound waves in the 20 Hertz to 20,000 Hertz frequency band.

23. The system of claim 18, wherein the wireless signals comprise longitudinal pressure waves in the 20,000 Hertz to 200 megaHertz frequency hand.