Abstract-This paper presents a hexagonal shape defected ground structure (DGS) implemented on two element triangular patch microstrip antenna array. The radiation performance of the antenna is characterized by varying the geometry and dimension of the DGS and also by locating the DGS at specific position which were simulated. Simulation and measurement results have verified that the antenna with DGS had improved the antenna without DGS. Measurement results of the hexagonal DGS have axial ratio bandwidth enhancement of 10 MHz, return loss improvement of 35%, mutual coupling reduction of 3 dB and gain enhancement of 1 dB.

Abstract-A novel design of multiband microstrip antenna array with dumbbell shape defected ground structure (DGS) is presented. The DGS is inserted into the ground plane between the two elements of the antenna array in order to suppress mutual coupling. Both simulation and measurement results verified that the DGS improved the radiation properties of the antenna array. Measurement results of the DGS antenna showed mutual coupling reduction of maximum 5 dB and gain enhancement to 3 dB.

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For application in a room-temperature microbolometer to detect terahertz waves, “narrow-width effects” on the temperature coefficient of resistance (TCR) and resistivity (ρ) for platinum (Pt) and titanium (Ti) nanowires are investigated. The TCR and ρ of a thermistor could be described by empirical formulas with average measured widths for higher precision. The effect of width on TCR in Pt is lower than that in Ti. The noise equivalent power of the microbolometer could be improved by a factor of 2.3 by replacing the Ti thermistor with a Pt thermistor of the same width (100 nm). The results provide a detailed understanding of the narrow-width effect on TCR for Pt and Ti, which, to our knowledge, is lacking at present.

The main problem in designing a multiband bandpass filter (BPF) is making each passband response highly independent, where each bandwidth of multiband BPF can be controlled and adjusted separately. To overcome this problem, this paper proposes a highly independent multiband BPF based on a multicoupled line stub-SIR with a folding structure. The proposed multiband BPF is constructed as a multicoupled line to generate a highly independent inter-passband. Moreover, the multiband performance is produced separately and independently by using three sets of resonators: resonator A1/A2 (R A1 and R A2), resonator B1/B2 (R B1 and R B2), and resonator C1/C2 (R C1 and R C2). The three passband frequencies can be independently arranged and designed. To miniaturize the multiband BPF, a folding structure is also proposed. As a result, the multiband BPF has a compact size that is reduced by over 61.29 % compared to previous structures. The even-odd excitation model and the equivalent circuit model are used to analyze the multiband BPF structure. This BPF is designed for GPS applications at 1.57 GHz, WCDMA (3G) at 1.8 GHz, WLAN (WiFi) at 2.4 GHz, LTE (4G) at 2.6 GHz, and 5G communication at 3.5 GHz. To evaluate and validate the proposed structure of the multiband BPF, the circuits are fabricated and tested. The simulated and measured results of the multiband BPF show good agreement. In conclusion, the proposed multiband BPF structure has a highly independent inter passband response and a compact size. INDEX TERMS Compact, folding structure, highly independent, multiband BPF.