Phased Array Technique Research Articles

Non-destructive Inspection of Composite Aileron during Fatigue Test

The operational safety and reliability of an airplane must be an integral part of its design. The use of suitable materials that pass material certification tests is very important for a new aircraft design. The next part is testing specific samples, sub-components, and components such as the aileron. The paper deals with a non-destructive evaluation of composite primary structural part fatigue tests in accordance with damage tolerance philosophy considering impact damage presence. NDT methods such as visual, eddy current, and ultrasonic testing included phased array technique, are used for the inspections. A schedule of inspections was created, and structural durability was verified.

2-D Self-Injection-Locked Doppler Radar for Locating Multiple People and Monitoring Their Vital Signs

This article presents the combination of a self-injection-locked (SIL) radar with frequency-modulated continuous-wave (FMCW) and switched phased-array (SPA) techniques to locate multiple people and detect their vital signs with high resolution and high sensitivity. The proposed system utilizes a subharmonic upconverter/downconverter with a 1.675-2.175-GHz chirp local oscillator (LO) signal to convert between a 2.45-GHz SIL IF signal and a 5.8-6.8-GHz FMCW RF signal. It transmits the FMCW RF signal and receives the echo signal using a transmit (Tx) antenna and a switched receive (Rx) antenna array, respectively, and processes the SIL IF signal to produce a range-azimuth map (RAM) that displays the positions of all people, their respiration rates (RRs), and their heart rates (HRs) in the monitoring region. The key advantage of combining the FMCW and SPA techniques is the provision of higher spatial resolution than obtained using each technique alone. This article also proposes a Doppler-weighted RAM to improve the identifiability of the images that are generated by two persons close to each other. Finally, the presented system was experimentally validated by measuring the locations and vital signs of up to five seated persons at a range of more than 1.5 m, of which two persons were seated almost shoulder by shoulder.

Updating of wavenumber-frequency spectrum models by a phased array measurement

This study mainly presents the updating of wavenumber-frequency spectrum models (W-F models) based on spatial correlation measurement by a phased array technique, which is critical for the evaluation of the structural vibration caused by a turbulent boundary layer. Measurements are carried out in a wind tunnel, and the effect of background noise on identifying the spatial correlations of pressure fluctuations is discussed. To improve the resolution of the beam map used to estimate the spatial correlation by the beamforming algorithm, focusing functions are introduced to accelerate beam focusing. Then, broadband fluctuations and flow-speed effects on spatial correlation identification are discussed to estimate the adaption scope of the phased array technique. To update W-F models of wall pressure fluctuations, the subsection approaching method (SAM) is employed to extract the power spectrum of wall pressure fluctuations based on the identified spatial correlation. The investigated results reveal that the spatial correlation of wall pressure fluctuations caused by the turbulent boundary layer obeys a statistical law but does not constitute an exact math expression, which further validates the necessity of the phased array technique in spatial correlation identification.

Ultrasonic Phased Array Techniques for Industrial Applications

Ultrasonic Phased Array Techniques for Industrial Applications

Acoustic sources mapping based on the non-negative [formula omitted] regularization

Phased microphone array techniques for estimating source locations and strengths have been widely employed in aeroacoustic applications. Many source localization algorithms by conducting the convex L1 norm optimization have been proposed by assuming a spatially sparse distribution of the sound sources in recent years. Nevertheless, L1 norm optimization has been shown to be suboptimal and cannot enforce further sparsity. This paper proposes a nonconvex L1/2 regularization approach for solving the inverse problem of deconvolution approach to improve its spatial resolution and robustness. Thus, the iteratively reweighted least squares method is employed to solve the L1/2 regularization problem. The capabilities of the proposed algorithm are demonstrated using various synthesized simulations to compare the results with other algorithms and it is found that multiple closely spaced sound sources with unequal powers can be identified. It indicates that the L1/2 regularization method can provide significant improvement with high spatial resolution and reduced sidelobes compared to the L1norm regularization method, and the computation cost is not increased significantly. The proposed method is applied in the experimental applications of benchmark test DLR1. Two incoherent sources are discerned near the flap side edge at particular frequency.

A high-sensitivity and long-distance structural health monitoring system based on bidirectional SH wave phased array

When estimating a structural health monitoring (SHM) system, its defect sensitivity and area/distance coverage are most important factors. For commonly used guided wave sparse array system, it usually requires a reference state as the baseline which is not available in many cases. In comparison, phased array technique typically does not need the baseline in simple structures and it had been successfully used in nondestructive testing (NDT). However, currently developed phased array systems employed omni-directional transducers routinely, where the wave energy is distributed equally along all directions thus it is not favorable for long-distance detection. In this work, bidirectional piezoelectric transducers were used to form a linear phased array system, which can generate/receive shear horizontal (SH) wave with high energy concentration. Firstly, the configuration of the employed transducer composed by antiparallel d15 piezoelectric strips (APS) was presented. Then the total focusing method (TFM) employed for defect detection was introduced. After validating the radiation pattern of SH wave generated by the APS, the properties of beam steering for the proposed phased array was investigated. Finally, experiments were carried out to validate its performance in detection of various defects. Results indicated that even for a 1 mm through-thickness hole 700 mm away, the proposed phased array system can still detect it accurately, which is much better than previous SHM systems. Dual defects including a crack and a hole can also be clearly detected without baseline. The high-sensitivity of the proposed system was attributed to the employed bidirectional transducer which can generate non-dispersive SH0 wave with high energy concentration. This proposed SH wave phased array system will provide a high-performance SHM method for plate-like structures.

Non-linear Phased Array Imaging of Flaws Using a Dual and Tri Frequency Modulation Technique

Recently, there has been high interest in the capabilities of nonlinear ultrasound techniques for damage/defect detection as these techniques have been shown to be more sensitive than linear ultrasound techniques for certain types of damage. This paper presents a nonlinear ultrasound phased array modulation method based on the principles of frequency and amplitude modulation, for the detection and imaging of material defects/damage. The proposed method requires the use of standard ultrasound phased array systems, which use multiple transmitting and receiving elements. An adjusted dual frequency method and tri-frequency is employed, which focuses on the evaluation of harmonic sidebands. A pump signal at a frequency of f2 is used to initialise a ‘breathing/ringing’ crack scenario after which a second frequency at f1 is used to further excite the crack and improve the probability that harmonic sidebands are generated. The modulation method employs a subtraction method which is used to filter out the fundamental frequencies. The technique adds benefits in ensuring that equipment based nonlinearities produced by single frequency setups are eliminated, ensuring that only defect related nonlinearities are present. A closed fatigue crack was evaluated using multiple linear and nonlinear ultrasound phased array techniques with the suggested method showing clear benefits. Furthermore, it is shown that modulation techniques with more than two driving frequencies could further improve damage detection capabilities of phased array systems.

Log-periodic temporal apertures for grating lobe suppression in k-space tomography.

Millimeter-wave (mmW) imaging receivers have demonstrated the ability to sense radio-frequency (RF) waves using traditional phased antenna array techniques, and, through a coherent photonic up-conversion process, image these waves using free-space optical systems. Building upon the idea of coherent up-conversion, k-space tomography extends the functionality of the millimeter-wave imaging receiver as a two-dimensional spatial processing unit to three-dimensional sensing with the addition of frequency detection. In this configuration, an arrayed waveguide grating, or temporal aperture, is implemented following the photonic up-conversion of RF signals received by the phased array. These waveguides of varying length add a spectral beam-forming network to the existing spatial beam-forming of the mmW-imaging receiver. The introduction of three-dimensional phase information to the imaging system disrupts the ability to directly image the RF signal distribution on a photo-detector array, requiring the application of tomographic algorithms to reconstruct the power distribution of the received signals. In order to receive and properly recover the spatial-spectral distribution of RF sources, the antenna array and temporal array must be sampled adequately to avoid introduction of grating artifacts into the system response. Grating lobes, an artifact of regular spacing of elements within a grating, restrict the alias-free field of regard for antenna arrays, or the free spectral range for time-delay based arrays, thus limiting the spatial-spectral monitoring of RF sources via the k-space imaging modality. To alleviate this constraint, we present a non-uniform log-periodic array sampling for the k-space tomographic time-delay based aperture, greatly increasing the free spectral range of the system while maintaining the number of existing channels.

Finite Element Analysis Model on Ultrasonic Phased Array Technique for Material Defect Time of Flight Diffraction Detection

In this study, the finite element method (FEM) for phased array technology in ultrasonic time of flight diffraction (TOFD) for the defect detection of two-dimensional (2-D) geometric materials was researched. The phased array technology generated the FEM model for the TOFD signal. We have established the finite element model by the FEM software ANSYS based on the ultrasonic mechanism about the defects and the phased array transducer. A plane strain elements have simulated the reflected signal of the defect. We can compare the error ratio between simulation and experiment by using the theoretical calculation value as the benchmark, and find the feasibility of the FEM detection.

A Ku-Band 6-Bit Vector-Sum Phase Shifter With Half-Quadrant Control Technique

This paper presents a 6-bit vector-sum phase shifter with half-quadrant control technique for Ku-band phased arrays. In this paper, the gain and phase symmetry in each quadrant is studied. Based on the gain and phase symmetry in vector-sum phase shifter, the half-quadrant control technique is proposed to simplify the complexity of phase control, phase measurement and phase calibration for large-scale phased arrays. Besides, a phase optimization method without extra phase settings is proposed to achieve low phase error. As results, the measured 6-bit RMS phase error is 1.6° ~ 2.3° across 13 ~ 17 GHz with only 64 different phase states, demonstrating the brevity and accuracy of phase control simultaneously. With the same phase optimization, six chips are measured and the maximum deviation of RMS phase error is −11.4 dBm. The chip consumes 29.7 mW with 1.8 V supply and occupies $0.9\times1.45$ mm2. This work is fabricated in TSMC 180-nm CMOS technology.

Radiofrequency applicator concepts for thermal magnetic resonance of brain tumors at 297 MHz (7.0 Tesla)

Purpose Thermal intervention is a potent sensitizer of cells to chemo- and radiotherapy in cancer treatment. Glioblastoma multiforme (GBM) is a potential clinical target, given the cancer’s aggressive nature and resistance to current treatment options. The annular phased array (APA) technique employing electromagnetic waves in the radiofrequency (RF) range allows for localized temperature increase in deep seated target volumes (TVs). Reports on clinical applications of the APA technique in the brain are still missing. Ultrahigh field magnetic resonance (MR) employs higher frequencies than conventional MR and has potential to provide focal temperature manipulation, high resolution imaging and noninvasive temperature monitoring using an integrated RF applicator (ThermalMR). This work examines the applicability of RF applicator concepts for ThermalMR of brain tumors at 297 MHz (7.0 Tesla). Methods Electromagnetic field (EMF) simulations are performed for clinically realistic data based on GBM patients. Two algorithms are used for specific RF energy absorption rate based thermal intervention planning for small and large TVs in the brain, aiming at maximum RF power deposition or RF power uniformity in the TV for 10 RF applicator designs. Results For both TVs, the power optimization outperformed the uniformity optimization. The best results for the small TV are obtained for the 16 element interleaved RF applicator using an elliptical antenna arrangement with water bolus. The two row elliptical RF applicator yielded the best result for the large TV. Discussion This work investigates the capacity of ThermalMR to achieve targeted thermal interventions in model systems resembling human brain tissue and brain tumors.

Perceptually Correct Haptic Rendering in Mid-Air Using Ultrasound Phased Array

This paper provides a perceptually transparent rendering algorithm for an ultrasound-based mid-air haptic device. In a series of experiments, we derive a systematic mapping function relating from the device command value to final user's perceived magnitude of a mid-air vibration feedback. The algorithm is designed for the ultrasonic mid-air haptic interface that is capable of displaying vibro-tactile feedback at a certain focal point in mid-air through ultrasound phased array technique. The perceived magnitude at the focal point is dependent on input parameters, such as input command intensity, modulation frequency, and position of the focal point in the work-space. This algorithm automatically tunes these parameters to ensure that the desired perceived output at the user's hand is precisely controlled. Through a series of experiments, the effect of the aforementioned parameters on the physical output pressure are mapped, and the effect of this output pressure to the final perceived magnitude is formulated, resulting in the mapping from the different parameters to the perceived magnitude. Finally, the overall transparent rendering algorithm was evaluated, showing better perceptual quality than rendering with simple intensity command.

Phased Array Shaped-Beam Satellite Antenna With Boosted-Beam Control

This communication presents a beamforming shaped-beam satellite (SBS) antenna based on a phased array technique and a boosted-beam control. The presented SBS antenna is specifically designed to cover the whole regions of Korea including the southern and northern areas. The proposed SBS antenna consists of waveguide feed network, beamforming circuits, waveguide circular polarizers, 19 radiation elements, and a boosted-beam control panel with active component calibration for temperature variation. To maximize the flexible performance, boosted-beam mode is supported to meet the required high-power signal regardless of bad weather conditions. The adjustable effective isotropic radiated power (EIRP) range was around 6 dB and there are a total of 19 beamforming units each configured by drive amplifier, phase shifter, and attenuator. Also, one extra beamforming unit synchronized with the other 19 elements is integrated for active component calibration. Each beamforming element can control relative phase shift up to 360° with 5° step and relative amplitude variation up to 10 dB with 1 dB step as well. Also, each radiation element is configured by waveguide horn and the return losses were better than 25 dB at 21 GHz.

Ultrasonic Scattered Field Distribution of One and Two Cylindrical Solids with Phased Array Technique

The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field distributions of different incident waves created by elastic cylinders embedded in an elastic isotropic medium. Scattered waves, including longitudinal and transverse waves both inside and outside the cylinder, are described with specific modalities under an incident plane wave. A model with a scatterer embedded in a structural steel matrix and filled with aluminum is developed for comparison with the theoretical solution. The frequency of the plane wave ranged from 235 kHz to 2348 kHz, which corresponds to scaling factors from 0.5 to 5. Scattered field distributions in matrix materials blocked by an elastic cylindrical solid have been obtained by simulation or calculated using existing parameters. The simulation results are in good agreement with the theoretical solution, which supports the correctness of the simulation analysis. Furthermore, ultrasonic phased arrays are used to study scattered fields by changing the characteristics of the incident wave. On this foundation, a partial preliminary study of the scattered field distribution of double cylinders in a solid has been carried out, and the scattered field distribution at a given distance has been found to exhibit particular behaviors at different moments. Further studies on directivities and scattered fields are expected to improve the quantification of scattered images in isotropic solid materials by the phased array technique.

Characterization of planar flaws by an integrated approach using phased array and synthetic aperture focusing technique

Two sound beam focusing techniques viz. phased array (PA) and synthetic aperture focusing technique (SAFT) are used during ultrasonic non-destructive testing. While PA involves sequential excitation of elements in an array using focal laws, SAFT is a post-processing algorithm involving time-shifting, summation and averaging of A-scan signals acquired by a divergent sound beam. An integrated approach using PA and SAFT has been developed in the authors’ laboratory for sound beam focusing. The approach is utilized to accurately locate the extremities of planar flaws for their characterization in terms of depth and orientation. The technique is employed for characterization of simulated planar flaws in stainless steel plates and lack of sidewall fusion in a weld joint. The results obtained by PA-SAFT are found to be very accurate and comparable to the ones obtained by an advanced and a well-established array based technique called Full Matrix Capture – Total Focusing Method.

Phased Array Ultrasonic Inspection of Metal Additive Manufacturing Parts

The adoption of wire and arc additive manufacturing (WAAM) in the market has been retained by the need to find a suitable method to ensure the quality of the parts produced. WAAM processes build up parts through the deposition of weld beads, consequently components with rough finish surfaces are characteristics of the method. Non-destructive testing (NDT) by ultrasonic (UT) method, namely the phased array technique (PAUT), is usually used to detect these defects in welding. However, the roughness of the parts represents a challenge for the UT application, since these variations influence the interaction between the emitted UT beam and the component. This study is thus focused on assessing the capability of detecting WAAM defects. The effectiveness of phased array ultrasonic testing to detect defects in aluminium WAAM components with several degrees of surface finish was evaluated. Simulations were first performed with CIVA software to characterize the beam emitted and select the probes and inspection parameters. Afterwards, physical inspections were performed on three reference specimens. Experimental outcomes prove that PAUT techniques are suitable for WAAM defects detection, including sizing, morphology and location. In addition, the experimental results were consistent with the simulated ones. The probes were able to overcome the limitations caused by the surface roughness of the samples, for a maximum of 89.6 μm average waviness profile. Also, defects ranging from 2 to 5 mm were characterized, in size and depth. These preliminary results represent an essential step for the development of an NDT system for inspecting WAAM parts.

Corrosion Assessment using Advanced Ultrasonic Measurement Technique

This paper describes the remaining wall thickness assessment using Ultrasonic Testing Phased Array (UTPA) technique. A steel plate of thickness 15 mm consists of machined simulated corrosion with various thicknesses, depths, shapes, and sizes were used in this work. Manual corrosion scanner is attached with GE Phased Array (PA) thirty-two elements (transmitter and receiver) Dual Matrix probe of 5 MHz with 1.5 mm pitch is used. The scanner then applied firmly on the plate to execute the inspection. From the result, the relevant indications from the A, B and C-Scans display are collected and analysed. The outcome of the study revealed that UTPA technique is capable to collect a high density of measuring point of thickness compared to the conventional UT technique such as Ultrasonic Testing Thickness Gauge (UTTG).

Geometry-independent attenuation and randomness of ultrasound wave propagation in concrete measured by embedded PZT transducers

Ultrasound is widely used in nondestructive testing (NDT). It is the basis of many NDT techniques, such as acoustic emission, phased array and synthetic aperture focusing technique. The attenuation of ultrasound is a key factor that ensures the feasibility of these techniques. Conventional studies of attenuation are mostly conducted in specimens that have dimensions smaller than ultrasound wavelengths. In this type of study, reflections from media boundaries interfere with the wave, resulting in a geometry-dependent attenuation that cannot be applied in another specimen with a different geometry, even if the material is identical. Another factor that impacts on the viability of ultrasound NDT techniques is the spatial uniformity of waves in the concrete sample. To serve as a reference in testing defects, the degree of randomness caused by the material’s heterogeneity should be estimated in conditions free of defects. In this study, a large concrete specimen was fabricated to suppress boundary reflections of the wave, creating an environment less dependent on geometry. Twenty-two PZT (lead zirconate-titanate ceramics) transducers were arranged in a three-by-seven array to transmit and receive ultrasound waves. This experiment sought to measure attenuation over distance and by frequency, as well as analyzing attenuation factors such as geometrical spreading and material absorption. A quadratic trend with good consistency between attenuation and frequency was found, indicating minimal local attenuation. The degree of randomness in the wave was measured by three indices: amplitude, group velocity and the frequency spectrum cross-correlation factor. Frequency dispersion was also described using group velocity. The findings of this study can serve as a reference for other NDT research, disclosing geometry-independent attenuation and the variability of wave characteristics in concrete.

Ultrasonic testing method for quality control of mold castings

The paper presents the review of one of the promising testing methods for quality control of mold castings that is ultrasonic inspection. Pulse-echo method, through transmission method and phased array technique are considered. The advantages and limitations for the analyzed methods are discussed. The produced by foreign and national companies aperture is reviewed.

Ultrasonic Control of Ductile Cast Iron Castings by Phased Array Technique

Ultrasonic Control of Ductile Cast Iron Castings by Phased Array Technique