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Microwave passive devices with high efficiency, small size, and light weight are one of the fundamental requirements for mobile communication coverage in the 5G frequency band. In this paper, the design of a novel ultra-wideband slow-wave microstrip transmission line is proposed and studied. The electromagnetic field simulation software HFSS is used to simulate the slow-wave microstrip transmission line, and the simulation results show that the ultra-wideband slow-wave structure has the advantage of wider bandwidth, smaller size, and lower cost, which meets the needs of 5G communication systems. Finally, the proposed slow-wave microstrip line is used in the U-shaped phase shifter, and the experimental results show that the novel slow-wave microstrip transmission line has a large application potential in the base station antenna system.

For convenient and efficient verification of the magnetoresistance effect in graphene spintronic devices, vertical magnetic junctions with monolayer graphene sandwiched between two NiFe electrodes are fabricated by a relatively simple way of transferring CVD graphene onto the bottom ferromagnetic stripes. The anisotropic magnetoresistance contribution is excluded by the experimental result of magnetoresistance (MR) ratio dependence on the magnetic field direction. The spin-dependent transport measurement reveals two distinct resistance states switching under an in-plane sweeping magnetic field. A magnetoresistance ratio of about 0.17 % is obtained at room temperature and it shows a typical monotonic downward trend with the bias current increasing. This bias dependence of MR further verifies that the spin transport signal in our device is not from the anisotropic magnetoresistance. Meanwhile, the I–V curve is found to manifest a linear behavior, which demonstrates the Ohmic contacts at the interface and the metallic transport characteristic of vertical graphene junction.