# US 2014/0197848 A1 · Removable surface -wave networks for in-situ material health monitoring

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- Number: US 2014/0197848 A1
- Document ID: US20140197848A1
- Status: Published application
- Kind: A1
- Application number: 13/742,831
- Filed: 2013-01-16
- Published: 2014-07-17
- Earliest claimed: 2013-01-16
- Assignees: HRL Laboratories, LLC
- Applicants: Hrl Laboratories, LLC
- Inventors: Daniel J. Gregoire; Joseph S. Colburn
- Web page: https://patentgrep.com/patent/US20140197848A1

## CPC

- G01N 3/00: Investigating strength properties of solid materials by application of mechanical stress
- G01M 5/0033: {by determining damage, crack or wear}
- G01M 99/00: Subject matter not provided for in other groups of this subclass
- G01N 22/02: Investigating the presence of flaws
- H01Q 13/20: Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- 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)
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)

## Abstract

A system for measuring properties of a surface under test with surface waves includes a surface wave network including a dielectric substrate, a reactive grid of a plurality of metallic patches on a first surface of the dielectric substrate, a plurality of electronic nodes on the first surface of the dielectric substrate, and a ground plane on a second surface of the dielectric substrate permeable to RF fields of the surface waves, and a controller configured for causing a respective one of the electronic nodes to transmit at least one surface wave and configured for collecting data for signals received by at least one other of the plurality of electronic nodes.

## Claims

### Claim 1

A system for measuring properties of a surface under test with surface waves, the system comprising:
a surface wave network comprising:
a dielectric substrate;
a reactive grid comprising a plurality of metallic patches on a first surface of the dielectric substrate;
a plurality of electronic nodes on the first surface of the dielectric substrate; and
a ground plane on a second surface of the dielectric substrate opposite the first surface of the dielectric substrate, the ground plane permeable to radio frequency fields of the surface waves; and
a controller configured for causing a respective one of the electronic nodes to transmit at least one surface wave and configured for collecting data for signals received by at least one other of the plurality of electronic nodes.

### Claim 2 (depends on 1)

The system of claim 1 wherein the surface wave network is a laminated structured metamaterial.

### Claim 3 (depends on 1)

The system of claim 1 wherein the plurality of metallic patches on a first surface of the dielectric substrate is greater in number than the plurality of electronic nodes on the first surface of the dielectric substrate.

### Claim 4 (depends on 1)

The system of claim 1 wherein the metallic patches are printed on the first surface.

### Claim 5 (depends on 1)

The system of claim 1 wherein the surface wave network further comprises:
a thin dielectric sheet laminated to the dielectric substrate; and
wherein the reactive grid comprising the plurality of metallic patches is on the thin dielectric sheet instead of the dielectric substrate.

### Claim 6 (depends on 1)

The system of claim 1 wherein the ground plane comprises a perforated ground plane having an array of holes.

### Claim 7 (depends on 1)

The system of claim 1 wherein:
the controller is configured to send a surface wave signal to a respective one of the electronic nodes; and
the respective one of the electronic nodes transmits a surface wave in accordance with the surface wave signal.

### Claim 8 (depends on 1)

The system of claim 1 wherein:
the controller is configured to command a respective one of the electronic nodes to transmit a surface wave; and
the respective one of the electronic nodes is configured to generate a surface wave.

### Claim 9 (depends on 1)

The system of claim 1 wherein collecting data for signals received by at least one other of the plurality of electronic nodes comprises collecting amplitude and phase information.

### Claim 10 (depends on 1)

The system of claim 1 wherein:
each electronic node is configured to measure amplitude and phase of signal received, and comprises an analog to digital converter for converting the measured amplitude and phase to digital data.

### Claim 11 (depends on 1)

The system of claim 1 wherein:
the controller comprises a plurality of wires, each wire connected to a respective one of the electronic nodes.

### Claim 12 (depends on 1)

The system of claim 1 wherein:
the controller comprises a wireless network connected to a respective one of the electronic nodes.

### Claim 13 (depends on 1)

The system of claim 1 wherein when the surface wave network is located on a surface under test, the RF fields of the surface waves extend through the permeable ground plane into the surface under test.

### Claim 14 (depends on 1)

The system of claim 1 wherein the controller further comprises a processor for processing signals received from the electronic nodes, and for creating an image of properties of the surface under test.

### Claim 15 (depends on 1)

The system of claim 1 wherein the surface wave network is flexible, and/or stretchable to adapt to complex curvatures.

### Claim 16 (depends on 1)

The system of claim 1 wherein the surface wave network further comprises:
an inflatable bladder; and
wherein the surface wave network is on the outside of the inflatable bladder, on the inside of the inflatable bladder, or partially on the outside and the inside of the inflatable bladder.

### Claim 17 (depends on 16)

The system of claim 16 wherein:
the electronic nodes are distributed on the inside of the bladder; and
the permeable ground plane is located on the outside of the bladder.

### Claim 18 (depends on 17)

The system of claim 17 wherein:
the controller comprises a plurality of wires, each wire connected to a respective one of the electronic nodes;
the bladder comprises a pneumatic cable feedthrough; and
the plurality of wires pass through the pneumatic cable feedthrough.

### Claim 19 (depends on 16)

The system of claim 16 wherein the inflatable bladder is configured to fit within a reentrant cavity of complex curvature.

### Claim 20

A method of determining a surface characteristic of a surface under test, the method comprising:
removably locating a surface wave network on the surface under test, wherein the surface wave network comprises:
a dielectric substrate;
a reactive grid comprising a plurality of metallic patches on a first surface of the dielectric substrate;
a plurality of electronic nodes on the first surface of the dielectric substrate; and
a ground plane on a second surface of the dielectric substrate opposite the first surface of the dielectric substrate, the ground plane permeable to radio frequency fields of the surface waves;
operating a controller configured for causing a respective one of the electronic nodes to transmit at least one surface wave and configured for collecting data for signals received by at least one other of the plurality of electronic nodes; and
processing the collected data to determine the surface characteristic of the surface under test.

### Claim 21 (depends on 20)

The method of claim 20, wherein processing the collected data further comprises comparing the collected data to baseline collected data from a damage-free surface.

### Claim 22 (depends on 20)

The method of claim 20 wherein comparing the collected data to baseline collected data from a damage-free surface further comprises creating an image of the damage to the surface.

### Claim 23

An apparatus for measuring properties of a surface under test with surface waves comprising:
a surface wave network comprising:
a dielectric substrate;
a reactive grid comprising a plurality of metallic patches on a first surface of the dielectric substrate;
a plurality of electronic nodes on the first surface of the dielectric substrate; and
a ground plane on a second surface of the dielectric substrate opposite the first surface of the dielectric substrate, the ground plane permeable to radio frequency fields of the surface waves.

### Claim 24 (depends on 23)

The apparatus of claim 23 wherein the surface wave network is a laminated structured metamaterial.

### Claim 25 (depends on 23)

The apparatus of claim 23 wherein the surface wave network further comprises:
a thin dielectric sheet laminated to the dielectric substrate; and
wherein the reactive grid comprising the plurality of metallic patches is on the thin dielectric sheet instead of the dielectric substrate.

### Claim 26 (depends on 23)

The apparatus of claim 23 wherein the ground plane comprises a perforated ground plane having an array of holes.

### Claim 27 (depends on 23)

The apparatus of claim 23 wherein:
each electronic node is configured to measure amplitude and phase of signal received, and comprises an analog to digital converter for converting the measured amplitude and phase to digital data.

### Claim 28 (depends on 23)

The apparatus of claim 23 wherein when the surface wave network is located on a surface under test, the RF fields of the surface waves extend through the permeable ground plane into the surface under test.

### Claim 29 (depends on 23)

The apparatus of claim 23 wherein the surface wave network is flexible, and/or stretchable to adapt to complex curvatures.

### Claim 30 (depends on 23)

The apparatus of claim 23 wherein the surface wave network further comprises:
an inflatable bladder; and
wherein the surface wave network is on the outside of the inflatable bladder, on the inside of the inflatable bladder, or partially on the outside and the inside of the inflatable bladder.

### Claim 31 (depends on 23)

The apparatus of claim 23 wherein:
the electronic nodes are distributed on the inside of the bladder; and
the permeable ground plane is located on the outside of the bladder.