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EP-4641180-B1 - ASYNCHRONOUS TRANSIENT SIGNAL ANALYSIS

EP4641180B1EP 4641180 B1EP4641180 B1EP 4641180B1EP-4641180-B1

Inventors

  • Pourkazemi, Ali
  • STIENS, JOHAN
  • THIBAUT, Kato
  • AKBARIAN, Fahimeh

Dates

Publication Date
20260506
Application Date
20240424

Claims (15)

  1. A system (100) for non-destructive analysis of a test material, comprising: - an electromagnetic signal generator (110) configured for repetitively generating an electromagnetic wave of substantially one frequency wherein the electromagnetic wave comprises a transient part, and for emitting the electromagnetic wave using a first transmit antenna (111) in a first channel and using a second transmit antenna (112) in a second channel different from the fist channel, - a differential measurement module (120) configured for repetitive equivalent time sampling of transient signals from a first receive antenna (121) using a first clock signal and repetitive equivalent time sampling of transient signals from a second receive antenna (122) using a second clock signal, wherein the first clock signal and the second clock signal are correlated, - to obtain a set of reference samples from the first channel when the first receive antenna (121) is receiving repetitive transient signals from reflection of the electromagnetic wave at a first reference material positioned in front of the first transmit antenna (111) and - to obtain data samples from the second channel when the second receive antenna (122) is receiving repetitive transient signals from reflection of the electromagnetic wave at the test material when the test material is positioned in front of the second transmit antenna (112), wherein the sampling is asynchronous with the generated electromagnetic wave, - a processing module (130) configured for determining phase information from the set of reference samples of the first channel using predetermined operational data of the system and for converting the data samples into synchronous data samples comprising amplitude and phase information using the phase information of the set of reference samples of the first channel and using the predetermined operational data of the system.
  2. A system (100) according to claim 1, wherein at least part of the predetermined operational data of the system is obtained by the differential measurement module (120) by obtaining a first set of predetermined reference samples from the first channel when the first receive antenna (121) is receiving repetitive transient signals from reflection of the electromagnetic wave at the first reference material positioned in front of the first transmit antenna (111) in combination with a second set of predetermined reference samples from the second channel when the second receive antenna (122) is receiving repetitive transient signals from reflection of the electromagnetic wave at a second reference material when the second reference material is positioned in front of the second transmit antenna (112).
  3. A system (100) according to any of the previous claims wherein the first reference material or the second reference material is an ideal reflector.
  4. A system (100) according to any of the previous claims, wherein at least part of the predetermined operational data of the system is obtained by the differential measurement module (120) by obtaining a third set of predetermined reference samples from the first channel when the first receive antenna (121) is receiving repetitive transient signals from reflection of the electromagnetic wave at the first reference material positioned in front of the first transmit antenna (111) in combination with a set of predetermined crosstalk samples from the second channel when the second receive antenna (122) is receiving repetitive transient signals from crosstalk between the second transmit antenna (112) and the second receive antenna (122) when no material is positioned in front of the second transmit antenna (112).
  5. A system (100) according to any of the previous claims wherein the processing module (130) is configured for deriving, from the synchronous data samples of the repetitive transient signals from reflection of the electromagnetic wave at the test material, geometric information and/or electromagnetic properties of one or more layers of the test material.
  6. A system (100) according to any of the previous claims wherein the electromagnetic wave has a frequency between 0.1 GHz and 100 Thz.
  7. A system (100) according to any of the previous claims wherein the first clock signal is the same as the second clock signal.
  8. A method (200) for non-destructive analysis of a test material, the method (200) comprising: - repetitively generating (210) an electromagnetic wave of substantially one frequency wherein the electromagnetic wave comprises a transient part, and for emitting the electromagnetic wave using a first transmit antenna (111) in a first channel and using a second transmit antenna (112) in a second channel different from the fist channel, - repetitive equivalent time sampling (230) of transient signals from a first receive antenna (121) using a first clock signal and repetitive equivalent time sampling of transient signals from a second receive antenna (122) using a second clock signal wherein the first clock signal and the second clock signal are correlated, to obtain a set of reference samples from the first channel when the first receive antenna (121) is receiving repetitive transient signals from reflection of the electromagnetic wave at a first reference material positioned in front of the first transmit antenna (111) and to obtain data samples from the second channel when the second receive antenna (122) is receiving repetitive transient signals from reflection of the electromagnetic wave at the test material when the test material is positioned in front of the second transmit antenna (112), wherein the sampling is asynchronous with the generated electromagnetic wave, - processing (240) the set of reference samples and the data samples for determining phase information from the set of reference samples of the first channel using predetermined operational data of the system and for converting the data samples into synchronous data samples comprising amplitude and phase information using the phase information of the set of reference samples of the first channel and using the predetermined operational data of the system.
  9. A method (200) according to claim 8, the method comprising a pre-operation step (220), wherein the pre-operation step comprises: - obtaining at least part of the predetermined operational data of the system by repetitive equivalent time sampling (221) signals from the first receive antenna (121) using the first clock and from the second receive antenna (122) using the second clock, to obtain a first set of predetermined reference samples from the first channel when the first receive antenna (121) is receiving repetitive transient signals from reflection of the electromagnetic wave at the first reference material positioned in front of the first transmit antenna (111) and to obtain a second set of predetermined reference samples from the second channel when the second receive antenna (122) is receiving repetitive transient signals from reflection of the electromagnetic wave at a second reference material when the second reference material is positioned in front of the second transmit antenna (112), wherein the sampling is asynchronous with the generated electromagnetic wave, and/or wherein the calibration step comprises: - obtaining at least part of the predetermined operational data of the system by repetitive equivalent time sampling (223) signals from the first receive antenna (121) using the first clock and by repetitive equivalent time sampling signals from the second receive antenna (122) using the second clock, to obtain a third set of predetermined reference samples from the first channel when the first receive antenna (121) is receiving repetitive transient signals from reflection of the electromagnetic wave at the first reference material positioned in front of the first transmit antenna (111) and to obtain a set of predetermined crosstalk samples from the second channel when the second receive antenna (122) is receiving repetitive transient signals from crosstalk between the second transmit antenna (112) and the second receive antenna (122) when no material is positioned in front of the second transmit antenna (112), wherein the sampling is asynchronous with the generated electromagnetic wave.
  10. A method (200) according to claim 9 wherein the processing step (240) comprises calculating envelopes of the repetitive transient signals in the obtained samples and aligning these envelopes for calibrating timing of the repetitive transient signals in the obtained samples.
  11. A method (200) any of the claims 8 to 10 wherein the processing step (240) comprises removing outliers from the obtained samples.
  12. A method (200) according to any of the claims 8 or 11 wherein the processing (240) comprises deriving from the synchronous data samples of the repetitive transient signals from reflection of the electromagnetic wave at the test material geometric information and/or electromagnetic properties of one or more layers of the test material.
  13. A method (200) according to claim 12 wherein the deriving comprises deconvolution of the data samples into different contributions to the reflected part of the electromagnetic wave stemming from the reflection of the electromagnetic wave at, or the transmission through, one or more interfaces of the layer-based structure, based on a superposition model of the different contributions in the transient part of the reflected electromagnetic wave.
  14. A computer program product for, when executed on a processor, non-destructive analysis of a test material, the computer program product being programmed for - receiving a set of reference samples and a set of data samples from a differential measurement module which is configured for repetitive equivalent time sampling of transient signals from a first receive antenna (121) using a first signal clock and repetitive equivalent time sampling of transient signals from a second receive antenna (122) using a second clock signal wherein the first clock signal and the second clock signal are correlated, to obtain the set of reference samples from a first channel when the first receive antenna (121) is receiving repetitive transient signals from reflection of a repetitively generated transient electromagnetic wave at a first reference material positioned in front of a first transmit antenna (111) and to obtain the data samples from a second channel when the second receive antenna (122) is receiving repetitive transient signals from reflection of the electromagnetic wave at the test material when the test material is positioned in front of the second transmit antenna (112), wherein the sampling is asynchronous with the generated electromagnetic wave, - the computer program product furthermore being programmed for determining phase information from the set of reference samples of the first channel using predetermined operational data of the system and for converting the data samples into synchronous data samples comprising amplitude and phase information using the phase information of the set of reference samples of the first channel and using the predetermined operational data of the system.
  15. A data carrier comprising a computer program product according to claim 14 encoded thereon.

Description

Field of the Invention The present invention relates to the field of non-destructive testing and analysis of materials, and more specifically to systems and methods for sampling and processing repetitive transient radar signals reflected on these materials. Background of the Invention The field of non-destructive testing (NDT) is critical for ensuring the integrity and safety of materials and structures across various industries. NDT methods are employed to detect, characterize, and measure defects or inconsistencies in materials without causing damage, thereby preserving their utility, and extending their service life. These methods are essential in industries such as aerospace, automotive, construction, and manufacturing, where material failure can have catastrophic consequences. One of the challenges in the field of NDT is the accurate and efficient analysis of multilayer structures. These structures are common in many industrial applications, and their integrity is often crucial for the overall performance of the system they are part of. Traditional NDT methods, such as ultrasonic testing, radiography, and eddy current testing, have limitations in terms of resolution, depth of penetration, and the ability to provide quantitative information about the material properties. The resolution of measurements is a concern in NDT. As industries strive for more precise and detailed inspections, the demand for higher resolution in both lateral and depth dimensions increases. For instance, improving the frequency of the testing method can enhance resolution, but this often comes with technical and commercial challenges, particularly when dealing with high-frequency signals. An example of a prior-art set-up of a synchronized system for non-destructive analysis which implements a transient radar is illustrated in FG. 1. A single frequence signal is generated by the generator (1), a power divider (2) splits the incoming signal in two output signals. A first signal is for transmission to the material under test and a second signal is for synchronizing the sampling of the reflected first signal. A switch (5), with as input the first signal and triggered by a trigger (T), is repetitively switched on and off for repetitively generating a transient signal, and the obtained signal is amplified (7) before being transmitted using a transmit antenna. At the receive side the signal from the receiver antenna is sampled using a single shot sampler (6) and the sampling is synchronized using the second signal which can be filtered using a filter (3), and delayed with a tunable (8) delay using a delay creator (4). In the example illustrated in FIG. 1 the sampled signal can be processed using a computer. FIG. 2 shows a transient radar sinusoidal signal sampled using the prior art synchronous system of FIG. 1. An example of a synchronous system is disclosed in EP3106861A1. The need for synchronized signals in NDT methods can be a significant hurdle. Synchronization requires complex and expensive electronics, which can limit the practicality and scalability of these methods. This is especially true at higher frequencies, where generating synchronous transient radar signals becomes increasingly difficult. Despite the advancements in NDT technologies, there remains a need for further innovation to address these challenges. A method that can provide high-resolution, quantitative analysis of multilayer structures in a non-contact and non-destructive manner, without the need for synchronized signals, would be a significant step forward in the field. Such a method would ideally be adaptable to a wide range of industrial materials and applications, offering a more efficient and cost-effective solution for material analysis and quality control. Summary of the Invention It is an object of embodiments of the present invention to enable non-destructive analysis of test materials with enhanced frequency range and reduced costs by operating without the need for synchronized electromagnetic signal generation. This objective is accomplished by a system for non-destructive analysis of a test material according to the invention. In the first aspect, the present invention relates to a system for non-destructive analysis of a test material, comprising an electromagnetic signal generator configured for repetitively generating an electromagnetic wave of substantially one frequency wherein the electromagnetic wave comprises a transient part, and for emitting the electromagnetic wave using a first transmit antenna in a first channel and using a second transmit antenna in a second channel different from the first channel, a differential measurement module configured for repetitive equivalent time sampling of transient signals from a first receive antenna using a first clock signal and repetitive equivalent time sampling of transient signals from a second receive antenna using a second clock signal, wherein the first clock signal and the second clock signal ar