Microwave Imaging of Voids in Oil Palm Trunk Applying UWB Antenna and Robust Time-Reversal Algorithm

Abstract

The oil palm trees in Southeast Asia face a great challenge due to voids within tree trunks. Besides, both plantations and the palm oil industry suffered considerable losses due to ineffective inspection of defective trees. Several techniques such as ultrasound, X-ray, capacitive volume, gamma computed tomography, and microwave tomography were applied to detect and control the decay of a trunk. However, all the techniques showed substantial drawbacks (such as limited resolution, tedious processing time, and use of bulky equipment with limited mobility) except for microwave tomography which overtook the other techniques by using a method that distinguishes the dielectric properties of healthy and diseased trunks. This work proposes ultra-wide-band (UWB) signal transmission and reception using antenna sensor arrays that record reflections from affected regions in the trunk. Various factors have been considered, such as different cylindrical arrays of 4, 8, 12, and 16 antennas; different positions of hollows; a heterogeneous trunk; multiple targets; and larger trunk samples (16–30 cm). To validate the system’s capabilities, two cylindrical wood samples with different diameters of 100 mm and 140 mm and with one hollow and three hollows within are 3D-printed, investigated, and then measured. The authors recommended a robust time-reversal algorithm (RTR) to reconstruct 2D images that successfully identified and localized cavities with the smallest diameter of 3.5 mm. Furthermore, reconstructed images of measured data verified a practical and reliable oil palm trunk imaging and sensing system with a high structural similarity index and resolution.

High Gain Compact UWB Antenna for Ground Penetrating Radar Detection and Soil Inspection

“…The images of each target for each consideration are reconstructed utilizing the robust time-reversal algorithm presented in Figure 22 [ 45 ]. At first, the received signals from each array were extracted from CST and then imported into MATLAB.…”

“…However, to reconstruct the image of the target in this article, only one transmitter sent, and the others received, thus saving processing time. The images of each target for each consideration are reconstructed utilizing the robust time-reversal algorithm presented in Figure 22 [45]. At first, the received signals from each array were extracted from CST and then imported into MATLAB.…”

Full Ground Ultra-Wideband Wearable Textile Antenna for Breast Cancer and Wireless Body Area Network Applications

“…After the proposed antenna’s characteristics were investigated and evaluated in both on- and off-body conditions (and with and without tumours), the antenna’s capability in image reconstruction of tumours in the breast was assessed under various conditions: with a central tumour (with and without skin) and with two and three tumours. Figure 13 shows the reconstructed image using the robust time reversal algorithm presented in [ 47 ]. The spherical tumours were perfectly detected under all four conditions.…”

“… Reconstructed images using received signals from four arrays and a robust time reversal algorithm [ 47 ]: ( a ) central tumour with skin, ( b ) central tumour without skin, ( c ) two tumours and ( d ) three tumours. …”

A Bra Monitoring System Using a Miniaturized Wearable Ultra-Wideband MIMO Antenna for Breast Cancer Imaging

“…When the proposed antenna's characteristics in both on-and off-body environments (with and without a tumour) were assessed, the antenna's suitability for image reconstruction of breast tumours was tested under a variety of conditions: with a central tumour (small and large tumours), an off-centre tumour, two tumours, and three tumours. The reconstructed image is shown in Figure 26 using the RTR algorithm described in [64]. In all five conditions, the spherical tumours were perfectly detectable.…”