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Design procedure of a novel transmission line low‐pass filter is presented. The filter has a flexible rejection response for a prescribed cut‐off frequency and an in‐band ripple factor. It is compact by using a Z‐shaped coupled‐line section, which is loaded with open‐circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in‐band specifications. The simulated results show that the circuit can generate low‐pass responses with third‐, fifth‐, and seventh‐order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut‐off frequency of 0.5/0.3 GHz are fabricated using a three‐/five‐layer PCB process, which generate seventh‐order low‐pass filtering responses with good selectivity. The experimental results agree well with the predictions.

Nanoporous carbon/graphene composites (NCGC) are synthesized via one-step hydrothermal approach combining carbonization, where phenol and formaldehyde are used as carbon sources and triblock copolymers F127 as template. Transmission electron microscopy (TEM) and nitrogen adsorption measurements show that the synthesized NCGC samples possess high surface area over 400 m2·g−1 and mesoporous structures with interconnected pores. The electrochemical studies demonstrate that Pt catalyst with NCGC as support exhibits better eletrocatalytic activity for methanol oxidation as compared to the catalyst taking widely-used VulcanXC-72 as support. In addition, the potential formation mechanism of NCGC is discussed.