Microwave continuous-flow liquid food sterilisation, in which the liquid is mainly heated by microwaves, has the advantages of fast sterilisation speed, energy saving, comprehensive elimination, and less nutrient loss. Circular pipes are commonly used in microwave continuous-flow liquid heating processing. However, with circular pipes, which are widely used in the industry, the heating is uneven owing to the phenomenon of tube focusing when adopting external radiation. In this study, a novel microwave continuous-flow milk sterilisation system based on a coaxial slot radiator is proposed. First, the coaxial slot radiator was designed to realise efficient radiation through the establishment of multi-physics model. The structure of the system was then optimised by comparing the heating efficiency and uniformity of simulation results. The effect of microwave coaxial slot radiator rotation on heating uniformity was simulated and the results show that the heating uniformity is improved obviously. Experimental equipment was set up to verify the results of the simulation. The experimental results are consistent with the simulation results. Finally, the sensitivity analysis of the system is performed to confirm that, when the dielectric properties and types of liquid food change, the heating of the proposed microwave continuous-flow system remains efficient and uniform.

This paper presents a study of a miniature double-fed circular disc monopole antenna for ultra-wideband (UWB) systems using Finite Integration Technique (FIT) method. The antenna includes a planar circular disc as a monopole, a double-fed technique and a tapered microstrip feed line. Ground plane uses a nonlinear transformation structure to achieve a wide impedance bandwidth. Measured results show that –10 dB reflection coefficient bandwidth is from 2.96 GHz to more than 12 GHz for the proposed antenna. The measured results are in good agreement with simulated ones.

High-precision phase difference measurement based on field-programmable gate arrays (FPGA) has important application requirements in fields such as high-stability time-frequency transmission, signal synchronization, and precision testing. Addressing the limitations of traditional methods in terms of temperature stability and measurement accuracy, this paper proposes two high-precision phase difference measurement schemes based on the FPGA platform. An eight-parallel-multi-carry chain time-to-digital converter (TDC) and digital dual-mixer time difference (DDMTD) measurement modules are constructed to perform high-precision phase difference measurements on the phase-shifted output signal of the MMCM dynamic phase-shifted module. Results show that at room temperature (25 °C), the single-carry chain TDC exhibits better measurement accuracy than the DDMTD, and the single-carry chain TDC’s measurement error range of 4.7–6.0 ps is superior to the DDMTD’s 20–75 ps error range. Under different temperature conditions, the eight-parallel-multi-carry chain TDC consistently demonstrates superior measurement accuracy, resolution, and temperature stability compared to the single-carry chain TDC. In terms of measurement accuracy, under room temperature conditions, in three sets of phase difference tests (178.5714 ps, 357.1428 ps, and 535.7142 ps), the measurement error of the eight-parallel-multi-carry chain TDC was controlled within 4.6 ps, which is better than the 4.7–6.0 ps error range of the single-carry chain TDC. Average resolution: The average resolution of the single-carry chain TDC was 6.329 ps, while the average resolution of the eight-parallel-multi-carry chain TDC improved to 0.833 ps. Temperature stability: Within the temperature range of 10 °C to 100 °C, the temperature coefficient of the single-carry chain TDC was 0.002127 ps/°C, while the temperature coefficient of the eight-parallel-multi-carry chain TDC decreased to 0.000564 ps/°C. This paper also summarizes the advantages and limitations of the above methods in terms of implementation complexity and robustness, providing a reference for the optimized design of high-precision phase difference measurement technology for FPGA platforms.

The size of current microwave-driven UV lamps limits their direct application in dental light curing. This article proposes a coaxial structure to miniaturize the UV lamp. First, the Drude model and the finite difference time domain algorithm were used to analyze the multi-physical field coupling and the complex field distribution within the lamp. Second, the dimensional parameters of the lamp were optimized, which enabled the lamp to be miniaturized and operate with high performance. Third, to analyze the sensitivity of the lamp, the effects of input power, gas pressure, and gas composition on its performance were investigated. It was found that an input power of 6 watts was enough to light the bulb with over 90% energy utilization. Finally, to verify the feasibility, an experimental system was set up. The lamp was successfully lit in the experiment, and its spectral output was tested. The results show that the microwave-driven UV lamp based on a coaxial structure is miniaturized and broad-spectrum, making it suitable for clinical dental light curing.