Design of W-band PIN Diode SPDT Switch with Low Loss

A W-band PIN diode single pole double throw (SPDT) switch with low insertion loss (IL) was successfully developed using a hybrid integration circuit (HIC) of microstrip and coplanar waveguide (CPW) in this paper. In order to achieve low loss of the SPDT switch, the beam-lead PIN diode 3D simulation model was accurately established in Ansys High Frequency Structure Simulator (HFSS) and the W-band H-plane waveguide-microstrip transition was realized based on the principle of the magnetic field coupling. The key of the proposed method is to design the H-plane waveguide-microstrip transition, it not only realizes the low IL of the SPDT switch, but also the direct current (DC) bias of the PIN diode can be better grounded. In order to validate the proposed design method, a W-band PIN diode SPDT switch is fabricated and measured. The measurement results show that the IL of the SPDT switch is less than 2 dB in the frequency range of 85 to 95 GHz, while the isolation of the SPDT switch is greater than 15 dB in the frequency range of 89.5 to 94 GHz. In the frequency range of 92 to 93 GHz, the IL of the SPDT switch is less than 1.65 dB, and its isolation is higher than 22 dB. Switch rise time and switch fall time of the SPDT switch are smaller than 29ns and 19ns, respectively. Good agreement between the simulations and measurements validates the design method.

Magnetic field coupling microfluidic synthesis of diluted magnetic semiconductor quantum dots: the case of Co doping ZnSe quantum dots

Magnetic field coupling microfluidic synthesis of ZnCoSe QDs. The particle size and doping amount of QDs can be adjusted by adjusting the applied field, thereby realizing online control of the magnetic and optical properties of QDs.

Internal magnetic field tests and magnetic field coupling model of a three-coil magnetorheological damper

Magnetorheological damper is a typical semi-active control device. Its output damping force varies with the internal magnetic field, which is a key factor affecting the dynamic performance of the magnetorheological dampers. Existing studies about the magnetic field of magnetorheological dampers are limited to theoretical analysis; thus, this study aims to experimentally explore the complicated magnetic field distribution inside the magnetorheological dampers with multiple coils. First, the magnetic circuit of a three-coil magnetorheological damper was theoretically analyzed and designed, and the finite element model of the three-coil magnetorheological damper was set up to calculate the magnetic induction intensities of the damping gaps in different currents and numbers of coil turns. A three-coil magnetorheological damper embedded with a Hall sensor was then manufactured based on the theoretical and finite element analysis, and internal magnetic field tests under different conditions were carried out to obtain the actual magnetic induction intensities. At last, the magnetic field coupling model of the three-coil magnetorheological damper was proposed by introducing a coupling coefficient to describe the complex magnetic field distribution due to the strong coupling effect of the three coils, and the results calculated by the proposed model agreed well with the finite element analysis and magnetic field test data. The proposed model lays a foundation for the optimal design of the magnetic circuit and the mathematical model of multi-coil magnetorheological dampers.