Along with vessel detection, vessel recognition in high-resolution SAR images was necessary in order to monitor marine vessels effectively. However, lack of target data and phase defocusing of target from its velocity limited the recognition performance, especially when using detectors based on artificial intelligence. This study accordingly proposed effective vessel recognition in high-resolution ICEYE spotlight SAR images consecutively utilizing (i) vessel detector robust to defocused moving vessels and (ii) mitigation of moving target phase distortion. In order to apply quantitative and qualitative training data enhancement, a target velocity SAR phase refocusing function was developed. The proposed target velocity SAR phase refocusing function generated defocused SLC image with respect to different target azimuth velocity, which can be utilized for both training data augmentation and refocusing of velocity-induced phase distortion. Achievement of stable vessel recognition performance was enabled from (i) robust vessel detection on defocused moving vessels and (ii) well-focused detected vessel targets, both of which were consecutively applied using the proposed target velocity SAR phase refocusing function. Vessel detection results demonstrated robust performance regardless of vessel motion and vessel recognition results significantly improved after phase refocusing, both of which were subject to quantitative and qualitative training data enhancement. Performance of the proposed algorithm was analyzed both in terms of phase focusing and velocity estimation. Refocusing performance outperformed that of conventional state-of-the-art autofocusing algorithm, modified Phase Gradient Autofocusing, while azimuth velocity estimation derived the average offset of 0.68 m/s, which was regarded more accurate than previous azimuth velocity estimators based on single-channel SAR image.

3D-IC packaging using through silicon via technology has been extensively developed to meet small form factor and low power consumption demands for next generation devices. A wafer molding technology is required for 3D chip integration. Wafer molding is carried out in the chip-to-wafer process to ensure suitable levels of mechanical strength are reached. The key to wafer level mold processing is the reduction of warpage. This paper discusses the material developments and steps taken for process optimization in the wafer molding process to reduce warpage. A 2 chip stack arrangement was used for this investigation, with a 12 inch bottom wafer containing vias, and 9×9 mm top chip wafers. The evaluation was run systematically in three major phases. In the first phase, the levels of warpage experienced during the packaging processes were simulated. The evaluation of three different types of material (Epoxy, Silicone and Hybrid) was carried out in the second phase. The third and final phase involved the testing for warpage at room and high temperature conditions of the epoxy and hybrid based resins. The silicone based resin was also evaluated with varying amounts of filler and adhesion promoter. The modulus and coefficient of thermal expansion (CTE) were found to be extremely important, since lowering this property would result in low warpage levels, both at room and high temperatures, which control the water absorption and temperature cycle reliability in the silicone based resin were established.

A high-performance waveguide, 16 times 16 slot array antenna with a cover structure at 38 GHz is presented. The protective cover structure, which consists of a dielectric slab and arrayed conductor patches, offers an advantage for designing a highly directive array antenna because it lowers the resonant conductance of the slot set such that a large number of slots can be arrayed. The widths of the slots in this antenna are fixed to 1 mm for easy production with a common computer-controlled milling machine. Moreover, the manufacturing process for this antenna is simplified by positioning the waveguide corrugations and slots together on a plate, which eliminates a welding process. Measurements show an antenna gain of 30.8 dBi, a depolarization level below -30 dB, and an efficiency level of 71% at the frequency band of 37.638.6 GHz.

We present a compact L-band orthomode transducer (OMT) with a new waveguide junction consisting of a quad-ridged square waveguide and four single-ridged triangular waveguides. Quad-ridged square and single-ridged triangular waveguides of various sizes were numerically analyzed to estimate the cutoff frequencies and characteristic impedances of the waveguides. An optimum junction structure for the OMT with a low cutoff frequency and specific characteristic impedance was found based on the numerical simulation. The junction has a relatively small size without waveguide branches, and provides good impedance matching with a 50 Ω coaxial feed line. In addition, Klopfenstein and linear tapers were employed to design waveguide ridges for minimizing mismatches at the OMT junction. Measurement showed a bandwidth of about 400 MHz from 1.0 to 1.4 GHz and an isolation level below -40 dB in the frequency range. The cross section of the OMT was reduced to 62% of the standard waveguide cross section, and the total length is only 56 cm (2.24 λ₀) at 1.2 GHz.

Mitigation of geometric calibration offset in ocean without utilizing ground control points (GCPs) was investigated in this study. Real-time automatic identification system (AIS) information on vessels was exploited after preprocessing and accordingly tested against the detected vessels in the synthetic aperture radar (SAR) image. A repetitive procedure of measuring the offset between the AIS sensor and the vessel detection was conducted and derived the SAR image of which the positioning offset was ameliorated. The proposed geo-location enhancement algorithm demonstrated the possibility of application in real-time vessel monitoring from remote sensing.

A multifunctional scatterometer system and optimized radar signal processing for simultaneous observation of various physical oceanographic parameters are described in this paper. Existing observation methods with microwave remote sensing techniques generally use several separate systems such as scatterometer, altimeter, and Doppler radar for sea surface monitoring, which are inefficient in system operation and cross-analysis of each observation data. To improve this point, we integrated separate measurement functions into a single observation system by adding a measurement function of Doppler frequency to the existing system. So it enables to simultaneously measure the range and polarimetric responses of backscattering as well as movements of the sea surface. Here, the simultaneous measurement function of Doppler frequency was implemented by sampling an FMCW (frequency modulated continuous wave) radar signal as 2D raw data consisting of fast- and slow-time samples, i.e., the range and backscattering of radar target signals are analyzed from the fast-time samples while the Doppler frequency by the radar target’s movement extracts from the slow-time samples. Through the Fourier transformed-based range-Doppler signal process, distance (R), backscattering (σ°), and Doppler frequency (f_D) are sequentially extracted from the 2D raw data, and a correlation to the physical oceanographic parameters is analyzed. Operability of the proposed system was examed through total 3 times of field campaigns from June 2017 to August 2020 and the observation data retrieved by the radar measurement data (R, σ°, f_D) was also cross-analyzed with in-situ data: e.g., tide, significant wave height, and wind speed and direction. Differences in the comparative results as an observational accuracy are as follows. Tidal level (Root Mean Square Error 0.169 m (R)), significant wave height (RMSE 0.127 m (R), 0.362 m (σ°)), wind speed (RMSE 1.880 m/s (f_D), 2.094 m/s (σ°)) and direction (18.84° (f_D)).