Microwave microfluidic sensors have been employed for dielectric characterization of different liquids. Intuitively, the microfluidic channel plays a vital role in determining the sensor performance. In this article, for the first time, numerical optimization design of microfluidic channel route is carried out with the aim of improving the sensor sensitivity. Two swarm intelligence algorithms, i.e., particle-ant colony optimization algorithm and wolf colony algorithm, are implemented for the route optimization. Through the developed optimization procedure, the sensor sensitivity of the original design can be increased significantly. Several prototypes of optimized sensors are fabricated and tested, and they exhibit good capability in retrieving the liquid properties. In comparison with original complementary split-ring resonator-based sensor with a sensitivity of 0.308% for water measurement, the optimized sensor achieves a high sensitivity value of 0.55%, i.e., the sensor sensitivity is increased by 78.6% after optimization. The developed methodology can also be used in other designs, such as series LC -based sensor, whose sensitivity can be improved by about 50%. It is demonstrated that the developed methodology possesses good automatic optimization ability and universality for the optimal design of microwave microfluidic sensors.

This paper presents a three-dimensional band-absorptive frequency selective rasorber (FSR). Such an FSR is absorptive within a specific band, and almost transparent below the absorption band. The definition and evaluation of the band-absorptive FSR is initially provided and followed by the design concept of 3D FSR. An example is then proposed, whose unit cell is composed of 3D absorber and 3D band-stop FSS. An equivalent circuit model is established for understanding its operating principle. A prototype of the proposed 3D band-absorptive FSR is fabricated. Measured results show that it has an absorption band (|S11| ≤ -10 dB and |S21| ≤ -10 dB) from 4.21 GHz to 6.51 GHz, with a thickness of 0.17 wavelength at 4.21 GHz. Moreover, |S21| is higher than -1 dB at the frequencies below 1.28 GHz. The proposed band-absorptive FSR can be used as radomes for low-frequency antennas in military communications or spectrum monitoring systems.

This paper presents two complementary split-ring resonator (CSRR)-based sensors for full characterization of magneto-dielectric materials. The first proposed sensor is designed by loading the microstrip line with a CSRR, while the second one is by loading the microstrip line with two CSRRs. To distinguish the effects of permittivity and permeability on the shift of resonant frequency, the electric and magnetic fields are designed to be located at two separate zones in the CSRR. Two 50Ω resistors are mounted at the ends of the microstrip line to increase the quality factor. In addition, the second sensor can perform measurements of complex permittivity and complex permeability of the magneto-dielectric materials in a single run, thereby making the measurement faster, easier, and in a more cost-effective way. The prototypes of two proposed sensors are fabricated and tested for validation of their functionality. A good agreement can be achieved between the measured data and the reference values from the manufacturers' datasheet, thereby demonstrating the applicability of the proposed sensors for full characterization of the magneto-dielectric materials.

This article presents the construction and analysis of a hybrid numerical method for the discretization of the convection-dominated nonlinear carrier transport process in semiconductor devices. In the construction of the method, the edge streamline upwind (SU) current density model is employed to overcome the nonconvergence brought by the nonlinear property of the current continuity equation, and the mixed finite volume-finite element method (FVFEM) is utilized to effectively extend the edge SU current density model to multidimensional applications. The proposed method is more reliable and flexible than the finite box (FB) method and streamline upwind Petrov–Galerkin (SUPG) method. The performance of several popular SU current density models is compared to find the optimal one. The proposed method is validated by comparing the calculated results with those calculated using commercial software. Based on the streamline upwind-finite volume-finite element method (SU-FVFEM), the finite element method (FEM), and the domain decomposition method (DDM), an in-house parallel computing electrothermal simulator is developed for large-scale semiconductor devices. The performance of the in-house developed parallel simulator is evaluated through simulations of a p-n junction diode and a 3-D bipolar transistor. The results demonstrated that the developed parallel simulator possesses good accuracy, applicability, and scalability.