# US 2017/0284945 A1 · Characterization of dielectric slabs attached to the body using focused millimeter waves

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- Number: US 2017/0284945 A1
- Document ID: US20170284945A1
- Status: Published application
- Kind: A1
- Application number: 15/462,570
- Filed: 2017-03-17
- Published: 2017-10-05
- Earliest claimed: 2016-03-31
- Assignees: Northeastern University
- Applicants: Northeastern University
- Inventors: Carey Rappaport; Jose A. Martinez-Lorenzo; Ann Morgenthaler
- Web page: https://patentgrep.com/patent/US20170284945A1

## CPC

- G01N 22/00: Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more (G01N3/00 - G01N17/00, G01N24/00 take precedence)
- G01B 15/02: for measuring thickness
- G01S 13/887: {for detection of concealed objects, e.g. contraband or weapons}
- G01V 8/005: {operating with millimetre waves, e.g. measuring the black losey radiation}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)

## Abstract

A system for characterizing a dielectric object situated adjacent to an electrically conductive surface comprises a radiation source configured to radiate electromagnetic energy toward the dielectric object, and a receiver configured to receive scattered electromagnetic energy scattered by the dielectric object and the electrically conductive surface. The system may further comprise a control subsystem, coupled to the radiation source and the receiver, that determines an apparent focal point within the object, determines a phase shift associated with the scattered electromagnetic energy with respect to the electromagnetic energy radiated by the radiation source, and determine a thickness and an index of refraction of the object based, on the apparent focal point and the phase shift. The system may determine the apparent focal point by scanning a calculated focus point of the radiated energy through different depths of the object, and searching for a peak in an amplitude of the scattered energy.

## Claims

### Claim 1

A system for characterizing a dielectric object situated adjacent to an electrically conductive surface, comprising:
a control subsystem arranged to operate in conjunction with (i) a radiation source configured to radiate electromagnetic energy toward the dielectric object and (ii) a receiver configured to receive scattered electromagnetic energy that is scattered by the dielectric object and the electrically conductive surface, the control subsystem comprising a processor and a memory with computer code instructions stored thereon, the memory operatively coupled to the processor, the control system configured to:
(i) determine an apparent focal point within the dielectric object;
(ii) determine a phase shift associated with the scattered electromagnetic energy with respect to the electromagnetic energy radiated by the radiation source; and
(iii) determine a thickness of the object and an index of refraction of the object based on the apparent focal point and the phase shift.

### Claim 2 (depends on 1)

The system of claim 1, wherein the radiation source is a continuous-wave millimeter-wave source.

### Claim 3 (depends on 1)

The system of claim 1, wherein the control system cooperates with an antenna subsystem configured to focus the radiated electromagnetic energy at, within, or proximate to the dielectric object, and to receive the scattered electromagnetic energy scattered by the dielectric object.

### Claim 4 (depends on 3)

The system of claim 3, wherein the antenna subsystem comprises a Fresnel reflector aperture antenna.

### Claim 5 (depends on 1)

The system of claim 1, wherein to determine the apparent focal point within the dielectric object, the control subsystem is configured to adjust a calculated focus point of the radiated energy to scan through different depths of the dielectric object, and to search for a peak in an amplitude of the scattered electromagnetic energy.

### Claim 6 (depends on 5)

The system of claim 5, wherein the control subsystem is further configured to determine a conductive surface location by scanning the calculated focus point away from the dielectric object, and to determine a distance from the conductive surface location to the apparent focal point.

### Claim 7 (depends on 1)

The system of claim 1, wherein to determine the thickness of the object, the control subsystem produces a thickness determination as object thickness=
c
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Δ
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Φ
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F
c
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Φ
+
2
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π
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f
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Δ
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F
.

### Claim 8 (depends on 1)

The system of claim 1, wherein to determine the index of refraction of the object, the control subsystem produces an index of refraction determination as object index of refraction=
-
c
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Δ
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Φ
2
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π
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f
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.

### Claim 9 (depends on 1)

The system of claim 1, wherein the control subsystem determines that an air-to-dielectric interface of the dielectric object is one of (i) parallel to the electrically conductive surface adjacent to the dielectric object and (ii) non-parallel to the electrically conductive surface.

### Claim 10 (depends on 9)

The system of claim 9, wherein, when the air-to-dielectric interface of the dielectric object is determined to be non-parallel to the electrically conducting surface, the control subsystem performs an evaluation of the scattered electromagnetic energy as an iterative solution of:
E
s

(
r
,
ω
)
=
∫
r
′
∈
V

G
b
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(
r
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k
b
2
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(
r
′
,
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)
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χ

(
r
′
)
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dr
′
.

### Claim 11

A method of characterizing a dielectric object situated adjacent to an electrically conductive surface, comprising:
by a processor and a memory with computer code instructions stored thereon, the processor and memory operating in conjunction with a radiation source that radiates electromagnetic energy toward the dielectric object and a receiver that receives scattered electromagnetic energy scattered by the dielectric object and the electrically conductive surface, the memory operatively coupled to the processor such that, when executed by the processor, the computer code instructions cause the system to implement:
(i) determining an apparent focal point within the dielectric object;
(ii) determining a phase shift associated with the scattered electromagnetic energy with respect to the electromagnetic energy radiated by the radiation source; and
(iii) determining a thickness of the object and an index of refraction of the object based on the apparent focal point and the phase shift.

### Claim 12 (depends on 11)

The method of claim 11, further comprising focusing the radiated electromagnetic energy at, within, or proximate to the dielectric object, and to receive the scattered electromagnetic energy scattered by the dielectric object.

### Claim 13 (depends on 11)

The method of claim 11, further comprising determining the apparent focal point by adjusting a calculated focus point of the radiated energy to scan through different depths of the dielectric object, and searches for a peak in an amplitude of the scattered electromagnetic energy.

### Claim 14 (depends on 13)

The method of claim 13, further comprising determining a conductive surface location by scanning the calculated focus point away from the dielectric object, and determines a distance from the conductive surface location to the apparent focal point.

### Claim 15 (depends on 11)

The method of claim 11, further comprising determining the thickness of the object as object thickness=
c


Δ


Φ


Δ


F
c
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Δ
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Φ
+
2


π


f


Δ


F
.

### Claim 16 (depends on 11)

The method of claim 11, further comprising determining the index of refraction of the object as object index of refraction=
-
c


Δ


Φ
2


π


f
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Δ
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F
.

### Claim 17 (depends on 11)

The method of claim 11, further comprising determining that an air-to-dielectric interface of the dielectric object is one of (i) parallel to the electrically conductive surface adjacent to the dielectric object and (ii) non-parallel to the electrically conductive surface.

### Claim 18 (depends on 17)

The method of claim 17, further comprising, when the air-to-dielectric interface of the dielectric object is determined to be non-parallel to the electrically conducting surface, performing an evaluation of the scattered electromagnetic energy as an iterative solution of:
E
s

(
r
,
ω
)
=
∫
r
′
∈
V

G
b

(
r
,
ω
)

k
b
2

E
T

(
r
′
,
ω
)

χ

(
r
′
)

dr
′
.

### Claim 19

A non-transitory computer-readable medium with computer code instruction stored thereon, the computer code instructions, when executed by an a processor, cause a dielectric object detection system to:
determine an apparent focal point within the dielectric object, based on electromagnetic energy scattered by the dielectric object and the electrically conductive surface;
determine a phase shift associated with the scattered electromagnetic energy with respect to the electromagnetic energy radiated by the radiation source; and
determine a thickness of the object and an index of refraction of the object based on the apparent focal point and the phase shift.

### Claim 20 (depends on 19)

The non-transitory computer-readable medium of claim 19, wherein the computer code instructions, when executed by an a processor, further cause a dielectric object detection system to adjust a calculated focus point of the radiated energy to scan through different depths of the dielectric object, and searches for a peak in an amplitude of the scattered electromagnetic energy.