This letter describes an asymmetrical coplanar strip (ACPS) wall to suppress the mutual coupling between two closely spaced 5.8-GHz microstrip antennas. The ACPS wall, which is inserted vertically between the two antennas, introduces an additional coupling path to reduce the antenna coupling, occupying just a small area between the two antennas. The decoupling effect of the proposed structure is verified by the simulation and measurement. The experimental results show that the achieved isolation is better than 35 dB and reaches a maximum of 54.3 dB at 5.8 GHz, with an extremely close antenna distance of 0.030 (edge-to-edge distance). The measured patterns indicate that the proposed structure also improves the radiation of the microstrip antenna.
Particulate matter (PM) was collected in three different areas, SY-1, SY-2, and SY-3, in Shenyang, China, during the warm and cold seasons from 2012 to 2014. SY-1 was located beside a thermal power plant, far from the central area. SY-2 was near a coal heating boiler on the main road, close to the central area. SY-3 was on the main road, without fixed emission sources. Nine PM-bound polycyclic aromatic hydrocarbons (PAHs) were analyzed. The results showed that the mean concentration of total PAHs was higher in the cold season (92.6–316 ng m−3) than in the warm season (18.4–32.2 ng m−3). Five- and six-ring PAHs occupied a large percentage at all sites in the warm season, and four-ring PAHs were the dominant components in the cold season. Several diagnostic PAH ratios indicated that the main sources of PAHs in Shenyang in the warm and cold seasons were not only coal burning but also vehicle emission. In this study, we suggest that a benzo[a]pyrene/benzo[ghi]perylene ratio ([BaP]/[BgPe]) of 0.6 was a useful indicator to speculate the relative significance of coal burning and vehicle exhaust. Although the Shenyang government has undertaken actions to address air pollution, the PM and PAH concentrations did not decrease significantly compared to those in our previous studies. The cancer risk calculated from the BaP equivalent total concentration at all three sites in the warm and cold seasons exceeded the acceptable limit established by the US EPA.
A postwall slotline (PWS), composed of a bilateral slotline and two metalized via arrays aligned at the slot edges, is proposed and its application in the design of short-pulse tapered slot antennas (TSAs) is investigated. The characteristic impedance of the PWS is derived by a partly analytical and partly empirical method. Compared with the conventional slotline, the PWS has lower available characteristic impedance and larger variation range, which is favorable for meeting diverse design specifications. The PWS is employed in the design of two TSAs with exponential profile and Gaussian profile, respectively. The two tapered PWS antennas are fabricated and their performance in both frequency domain and time domain is investigated. The results show that the TSA based on the PWS is featured by broad bandwidth, low cross-polarization, and good suitability for short-pulse applications.
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