Sampling moiré effect is well-known in signal processing. When a continuous periodic signal $x(t)$ is sampled using a sampling rate $f_{s}$ that does not respect the Nyquist condition, and the signal-frequency $f_{x}$ folds over and gives a special sequence in the sampled signal. The coprime reconstruction is made possible when the periodic signal frequency $f_{x}$ and the sampling frequency $f_{s}$ satisfy $f_{s}/f_{x}=N/M$ with integer $M$, $N$, where $N/M$ is a reduced fraction. This article shows how to rearrange the N sample data into one entire period of the signal using the M periods of the signal. The reconstruction is equivalent to the decryption of the sample data using the method referred to the mathematic operator “multiplicative inverse modulo.” In the implementation to verify the coprime reconstruction, we used a commodity DSP board with 4.2 MHz sampling rate to reconstruct the 13.56 MHz signal acquired from the ADC circuit. The signal reconstruction result is comparable to the sampling result for the same signal sampled at 475 MHz sampling rate. The other simulation on the 234 kHz signal under 1 MHz sampling rate yields a very detail information on the signal with a finding that the multiplicative inverse modulo may also be used as the encryption of signal for network security use.

A new power receiving unit (PRU) is proposed in this paper for resonant wireless power transfer (WPT), which is characterized by the capability of attracting high power from the power transmitting unit (PTU). The resonant WPT is designed for delivering the electrical power to the PRU attached on an electrical vehicle (EV) chassis 50 cm away from a PTU installed on the ground. The proposed PRU uses only the passive elements such as inductors, diodes, and capacitors, which need no initial power from the EV. It is then applicable for charging a battery to several hundred volts for even a first-time charging battery. For a resonant WPT at a switching frequency of 4 MHz, the proposed PRU behaves as a negative impedance converter (NIC) itself in the subharmonics of 4 MHz. The NIC effect plus the subharmonic oscillation causes an instability current charging the battery connected to the PRU. In this paper, we simulated the PRU and performed the experiment. The experiment demonstrated a battery charging of 150 W from 50 cm away using three D-mode GaN HEMT transistors via the instability current ramp. The power transfer efficiency (PTE) improved as the power delivered to the load (PDL) increased. The peak PTE was 65% in the present findings. The simulation analysis showed that the circuit allowed itself be used to much higher power transfer when it is implemented with more GaN HEMT transistors connected in parallel. The theoretical derivation of the PRU circuit is also used to support both the experimental and simulation results.

A new power receiving unit (PRU) is proposed in this paper for the resonant wireless power transfer (WPT), which is characterized by the capability of attracting high power from the power transmitting unit (PTU). The resonant WPT is designed for delivering the electrical power to the PRU attached on an electrical vehicle (EV) chassis 50cm away from a PTU installed on the ground. The proposed PRU uses only the passive elements such as inductors, diodes and the capacitors, which needs no initial power from the EV. It is then applicable for charging a battery to several hundred volts for even a first-time charging battery. At a switching frequency of the resonant WPT in the experiment being 4MHz, the proposed PRU behaves itself as a negative impedance converter (NIC) in the subharmonics of 4MHz. The NIC effect plus the subharmonic oscillation causes an instability current charging the battery connected to the PRU. In this paper, we simulated the PRU and performed the experiment. The experiment demonstrates a battery charging of 150W from 50cm away using three D-mode GaN HEMT transistors via the instability current ramp. The power transfer efficiency (PTE) improved as the power delivered to load (PDL) goes higher. The best power transfer efficiency (PTE) is 65% in the present findings. The simulation analysis shows that the circuit allows itself be used to much higher power transfer when it is implemented with more GaN HEMT transistors connected in parallel. The theoretical derivation of the PRU circuit is also used to support both the experimental and simulation results.

This paper presents a resonant wireless power transfer method that leverages a 90-degree voltage phase shift between the transmitting and receiving coils to enhance efficiency and maximize power transfer. When the resonant coupling is achieved, the secondary coil with an adjustable capacitor forms a tuned LC circuit. If the primary coil is driven at the resonant frequency of both the primary and secondary sides, the system can transmit 250W of power between the coils over a distance of 50 cm. Using a single power transmitting unit (PTU) board with multiple paralleled gallium nitride high-electron-mobility transistors (GaN HEMTs), the system achieves a maximum power transfer efficiency of 88%, highlighting the effectiveness of the design in high-efficiency, long-distance wireless power transmission. The key to the success of high-power, high-efficiency RWPT is in exhibiting the imaginary turn ratio presented on the air transformer. The imaginary turn ratio can realize the negative impedance conversion that converts the positive resistance on the power-receiving unit into a negative one, and thus, the damping of the resonance oscillation becomes negative and positively encourages more power to be delivered to the power-receiving unit (PRU) load. This paper derives the theory of the imaginary turn ratio and demonstrates the implementation of the RWPT system that exhibits the imaginary turn ratio effect.

As memory device packaging moves toward die stacking technology with thin chips of high density, wafer dicing has recently become a key factor in semiconductor yield. Stealth dicing technology, which produces laser irradiation inside the wafer to form a modified layer within the wafer without any damage to the surface, is an alternative and advanced dicing process that is in line with the future trend of thin wafers. The existing stealth dicing process that utilizes an ultrashort pulse laser is expensive. In this study, we proposed a low-cost method for wafer stealth dicing using quasi-continuous wave (QCW) lasers. We redesigned the focusing lens of a QCW metal-cutting laser machine to form a cutting head with a high numerical aperture (NA) that is suitable for wafer stealth dicing. An optothermal model used to simulate the dicing process and calculate the temperature was implemented numerically based on the Crank–Nicolson algorithm and the successive over-relaxation method. Both the simulation and experimental results demonstrate that a QCW laser machine with a high-NA focus lens is ideal for wafer stealth dicing.