Methods and Apparatus for Sensing Organic Tissue

• US 20130162459A1
• Filed: 12/27/2011
• Published: 06/27/2013
• Est. Priority Date: 12/27/2011
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Aharony, Nadav, Siegel, Michael
• Granted Patent: US 8,866,663 B2
• Time in Patent Office: Days
• US Class Current: 342/27
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56

Abstract

In exemplary implementations of this invention, a radio signal is transmitted between a transmitter and a receiver. Either the transmitter, or receiver, or both, have a directional antenna. When organic tissue passes between (or is stationary between) the transmitter and receiver, the tissue causes a reduction of the received signal strength (RSS) of the signal, as compared to a baseline RSS. The larger the amount of tissue, the greater is the reduction of the RSS. By analyzing the degradation of the signal, information about organic tissue between the transmitter and receiver may be determined. For example, the number of persons passing through a physical threshold may be determined. Or the fact that one person is walking faster than, and catching up with, a second person as they pass between the transmitter and receiver may be determined.

Claims

1. A method comprising:

transmitting radio signals from a first antenna to a second antenna, at least one of the first and second antennas being a directional antenna, and

processing data regarding received signal strength of the radio signals to determine the position, velocity or number of one or more bodies that are between or that cross between the first and second antennas.

2. The method of claim 1, wherein the first antenna is a directional antenna.

3. The method of claim 1, wherein the second antenna is a directional antenna.

4. The method of claim 1, wherein the processing of data includes the step of recognizing an event that starts when received signal strength at the second antenna falls below a baseline and that ends when received signal strength at the second antenna returns to the baseline.

5. The method of claim 4, wherein the processing of data further comprises the steps of:

calculating sum degradation as of different times during the event, recognizing a pattern in how the sum degradation changes during the event, and based on at least in part on the pattern that is recognized, determining the position, velocity or number of the one or more bodies.

6. The method of claim 4, wherein the processing of data further comprises the steps of:

recognizing a pattern in how received signal strength changes during an event, and

based at least in part on the pattern that is recognized, determining that, during at least part of the event, a body is located between the first and second antennas and is not moving.

7. The method of claim 1, wherein the radio signals are received by a plurality of antennas, including the second antenna, and the data that is processed includes received signal strength of each of the plurality of antennas, respectively.

8. The method of claim 1, wherein:

the first and second antennas are members of a set of antennas, which set comprises at least three antennas,

a subset comprises all or part of the set of the antennas, each member of the subset is a directional antenna, each member of the subset has a direction of peak power gain, and said direction of peak power gain has a projection on a reference plane, which reference plane is a plane that intersects all of the directional antennas in the subset or that intersects the maximum number of directional antennas in the subset that any plane intersects, and

the projections on the reference plane intersect each other at angles.

9. The method of claim 8, wherein at least some of the angles, respectively, are greater than 85 degrees.

10. The method of claim 8, wherein at least some of the angles, respectively, are less than 70 degrees.

11. The method of claim 1, wherein the radio signals have a frequency that is more than 2.3 GHz and less than 2.5 GHz.

12. The method of claim 1, wherein the radio signals have a frequency that is more than 4.9 GHz and less than 5.1 GHz.

13. The method of claim 1, wherein

the first and second antennas are positioned at a first and second height, respectively, above the surface on which the bodies are walking or standing, and

the first and second heights are each less than 145 centimeters and more than 85 centimeters.

14. The method of claim 1, wherein the first and second antennas may each transmit and receive signals.

15. Apparatus comprising, in combination:

a transmitter for transmitting radio signals, which transmitter includes a first antenna,

a receiver for receiving the radio signals, which receiver includes a second antenna, at least one of the first and second antennas being a directional antenna, and

at least one processor for processing data regarding the received signal strength of the radio signals received by the receiver and determining, based on that data, the number of the bodies that move past a threshold.

16. The apparatus of claim 15, wherein the bodies comprise human bodies.

17. The apparatus of claim 15, further comprising an attenuator for reducing signal strength of the radio signals transmitted by the transmitter.

18. Apparatus comprising

a first transmitter for transmitting radio signals,

a first receiver for receiving the radio signals and outputting electrical signals,

a signal conditioning module for accepting the electrical signals and for outputting conditioned signals, and

at least one processor for

processing the conditioned signals to determine reduction in received signal strength of the radio signals relative to a baseline, and

based on the reduction, determining the position, velocity or number of one or more bodies that are between, or cross between, the first and second antennas,

wherein the first transmitter includes a first antenna and the first receiver includes a second antenna, and at least one of the first or second antennas is a directional antenna.

19. The apparatus of claim 18, wherein the at least one processor comprises more than one processors, at least one of which is remote from both the first transmitter and the first receiver.

20. The apparatus of claim 19, which apparatus further comprises other receivers for receiving the radio signals, each of which other receivers has an antenna,

wherein:

the data that the at least one processor is adapted to process includes received signal strength of each antenna of the other receivers, respectively, and

either the first antenna is a directional antenna or the second antenna and each antenna of the other receivers are directional antennas.