Granted Patent B2

US 12,631,746 · App. 17/926,751 · Granted May 19, 2026

Inventors: Kush Agarwal (Singapore, SG); Karthik Thothathri (Singapore, SG)

Assignee: Wavescan Technologies PTE. LTD.

G01S13/887G01S13/86G01S13/90

Abstract

Claims (48)

1 . A non-contact microwave testing system for see-through imaging of an area under testing, comprising:

a front-end subsystem configured to transmit and receive electromagnetic waves to and from the area under testing, wherein the front-end subsystem comprises at least one transmitter antenna and at least one receiver antenna, wherein the at least one transmitter antenna and the at least one receiver antenna are integrated with a metamaterial-based lens that includes a plurality of concentric periodic split-ring resonators (SRRs) of varying sizes and concentric circular trace lines running in the bottom layer of the lens, wherein the metamaterial-based lens is made from double negative materials (DNG) having the property of negative index to enable sub-wavelength high-resolution imaging;

a System in Package (SiP) subsystem comprising transmitter and receiver radio frequency (RF) chains, wherein the SiP subsystem generates a stepped frequency continuous wave (SFCW) waveform for non-destructive testing of heterogeneous multi-layered media, including concrete, brick and mortar, ceramic facade, stone claddings, and glass facades;

a signal processing subsystem configured to perform reconstruction of spatial reflectivity of heterogeneous multi-layered media in the area under testing, by:

obtaining wideband frequency domain data S(x, y, z, f) over a source aperture, wherein (x,y,z) represent spatial coordinates and f represents frequency;

reconstructing the spatial reflectivity using at least one of:

piecewise phase addition for each of a plurality of layers of the multi-layered media, wherein an additional phase is added to a collected frequency spectrum in a piecewise manner, one layer at a time, for 3D imaging of the area under testing, including Fresnel transmission coefficients between the layers, or

deconvolution using dyadic Green's functions of the multi-layered media to include a plurality of reflections and a plurality of attenuations by the plurality of layers, wherein the reconstructed spatial reflectivity provides amplitude and phase components for each x, y, z coordinate for 3D quantitative imaging, including parameters of permittivity and conductivity; and

generating a three-dimensional (3D) image of the area under testing based on the reconstructed spatial reflectivity;

a localization subsystem configured to provide location information for synthesizing a synthetic aperture for the generated 3D image;

an interface subsystem configured to transfer visualization data of the generated 3D image of the area under testing;

wherein the non-contact microwave testing system is configured to achieve a penetration depth of at least 0.20 m in non-metallic materials and differentiate two distinct objects if a distance of at least 0.01 m separates them,

wherein the non-contact microwave testing system is configured to operate in a frequency range from 0.1 GHz to 10 GHz.

2 . The system of claim 1 , wherein the front-end subsystem comprises at least one transceiver.

3 . The system of claim 1 , wherein the signal processing subsystem comprises backpropagation algorithms for reconstruction of spatial reflectivity of the multi-layered media using the SFCW waveform.

4 . The system of claim 1 , wherein the localization subsystem comprises optical flow sensors, an inertial measurement unit (IMU), and barometric pressure sensors.

5 . The system of claim 1 , wherein the interface subsystem transfers data from the signal processing subsystem to a cloud server or a local tablet personal computer (PC) for reconstruction of the high-resolution image.

6 . The system of claim 1 , wherein the front-end subsystem is a beam focusing multiple-input-multiple-output (MIMO) front-end subsystem comprising an array of transmitter antennas that are time-division multiplexed and an array of receiver antennas forming a virtual antenna array based on the physical arrangement of the transmitter and receiver antennas;

wherein the SiP subsystem is a MIMO SiP subsystem comprising the transmitter and receiver RF chains for generating the stepped frequency continuous wave (SFCW) waveform; and,

wherein the localization subsystem provides location information of the system for the signal processing subsystem to synthesize a synthetic aperture for 3D image reconstruction.

7 . The system of claim 1 , wherein the front-end subsystem is a beam focusing antenna front-end subsystem comprising a single transceiver;

wherein the signal processing subsystem is a digital beamforming signal processing subsystem;

wherein the localization subsystem is deployed on a moving platform and provides the system's location information for the signal processing subsystem to synthesize a synthetic aperture for 3D image reconstruction.

8 . The system of claim 1 , wherein the metamaterial-based lens contains concentric periodic split-ring resonators (SRRs) of varying sizes and concentric circular trace lines running in a bottom layer of the lens.

9 . The system of claim 1 , wherein the metamaterial-based lens is placed on top of the at least one transmitter antenna and the at least one receiver antenna for non-penetrative scanning at a distance greater than a wavelength of the electromagnetic waves.

10 . The system of claim 1 , wherein the system is configured to be hand-held, mounted/fixed on a payload-carrying, autonomous/semi-autonomous/controlled system selected from an unmanned ground vehicle (UGV), a drone, a robotic arm, a crawler robot and/or a combination thereof for non-destructive inspection of facilities including facade structures, cladding systems, concrete pillars and walls, indoor mechanical, electrical and plumbing (MEP) fittings, water, oil and gas pipelines, metallic parts, roads, tree trunks, tunnels, dams, bridges, medical imaging, security surveillance and warehouse sorting.

11 . The system of claim 10 , wherein the system is configured to be hand-held, and wherein the front-end subsystem comprises:

a single input single output (SISO) configuration including a single transmitting and receiving wideband antenna element;

a monostatic array of antenna elements; or

a MIMO array of antenna elements.

12 . The system of claim 10 , wherein the system is mounted/fixed on a payload-carrying, autonomous/semi-autonomous/controlled system selected from an unmanned ground vehicle (UGV), drone, robotic arm and crawler robot, and wherein the front-end subsystem comprises:

a beam focusing antenna subsystem with a single transceiver;

a MIMO subsystem with multiple transceivers; or

a monostatic array of reflectometers.

13 . A method for non-contact see-through imaging of an area under testing, the method comprising the steps of:

generating electromagnetic waves by a System-in-Package (SiP) subsystem, wherein a stepped frequency continuous wave (SFCW) waveform is generated by the SiP subsystem for non-destructive testing of heterogeneous multi-layered media, including concrete, brick and mortar, ceramic facade, stone claddings, and glass facades;

transmitting the generated electromagnetic waves to a front-end subsystem through an RF interface, wherein the front-end subsystem comprises at least one transmitter antenna and at least one receiver antenna, wherein the at least one transmitter antenna and the at least one receiver antenna are integrated with a metamaterial-based lens that includes a plurality of concentric periodic split-ring resonators (SRRs) of varying sizes and concentric circular trace lines running in the bottom layer of the lens, wherein the metamaterial-based lens is made from double negative materials (DNG) having the property of negative index to enable sub-wavelength high-resolution imaging;

transmitting and receiving backscattered signals to the front-end subsystem from the area under testing;

routing received RF signals to a signal processing subsystem by the SiP subsystem for signal processing and reconstruction of spatial reflectivity of heterogeneous multi-layered media in the area under testing, wherein the reconstruction of spatial reflectivity comprises:

obtaining, by the signal processing subsystem, wideband frequency domain data S(x, y, z, f) over a source aperture, wherein (x, y, z) represent spatial coordinates, and f represents frequency;

reconstructing, by the signal processing subsystem, the spatial reflectivity using at least one of:

piecewise phase addition for each of a plurality of layers of the multi-layered media, wherein an additional phase is added to a collected frequency spectrum in a piecewise manner, one layer at a time, for 3D imaging of the area under testing, including Fresnel transmission coefficients between the layers, or

deconvolution using dyadic Green's functions of the multi-layered media to include a plurality of reflections and a plurality of attenuations by the plurality of layers, wherein the reconstructed spatial reflectivity provides amplitude and phase components for each x, y, z coordinate for 3D quantitative imaging, including parameters of permittivity and conductivity;

generating a three-dimensional (3D) image of the area under testing based on the reconstructed spatial reflectivity, wherein the generation of the 3D image comprises combining data from the SiP subsystem and a localization subsystem by the signal processing subsystem to perform 3D image reconstruction and data interpretation schemes, wherein the localization subsystem provides location information for synthesizing a synthetic aperture for the generated 3D image, and wherein the 3D image reconstruction and which is routed to an interface subsystem; and

routing the data interpretation schemes and a reconstructed 3D image by the interface subsystem through wired or wireless transmission to a cloud server or a local tablet personal computer (PC) for a user to visualise the image of the area under testing,

wherein the method achieves a penetration depth of at least 0.20 m in non-metallic materials and differentiates two distinct objects if a distance of at least 0.01 m separates them, and wherein the method operates in a frequency range from 0.1 GHz to 10 GHz.

14 . The method of claim 13 , wherein the backscattered signals from the area under testing are directly sampled at an aperture of the front-end subsystem, by a reflectometer utilizing a Schottky diode at an aperture of an antenna with a metamaterial-based lens.

15 . The method of claim 13 , wherein a dead reckoning algorithm for an inertial measurement unit (IMU) is combined with an optical flow sensor, for retrieving accurate coordinate information from the localization subsystem.

Assignments (1)

Priority Claims (1)

Continuity (1)

References Cited (33)