return loss, and isolation of the designed coupler over a band of 3.0 -11 GHz are shown in Figure 7. The simulated coupling is close to 3 dB. Return loss is greater than 21 dB, whereas isolation is better than 19 dB. The phase difference, between Ports 2 and 3 is 90°Ϯ 1.5°across the concerned frequency band, as illustrated in Figure 8.The measured result for the average coupling coefficient is about 3.6 dB. The isolation of the manufactured coupler is better 17 dB than, whereas the return loss is better than 18.5 dB. The measured phase difference between the output Ports 2 and 3 is 90°Ϯ 4°across the band. A relatively good agreement between the simulated and the measured results is observed. The discrepancies between the simulated and measured results can be explained by the manufacturing errors. The coupler was developed using a milling machine and its two layers had to be aligned manually. Plastic screws were used for alignment as well as for reducing the effect of air gaps. In terms of quality of its operation, the designed coupler with rectangular sections of microstrip lines and slots performs slightly worse than its elliptically shaped counter part reported in Ref. 9. However, its performance can still be considered as very satisfactory for many ultra wideband applications.
CONCLUSIONS
As an important carrier of information and culture, paper-based books and relics often suffer from many damages because of their fragile and environmentally sensitive intrinsic structure. Hence, a safe, durable, and multifunctional protection method is highly anticipated. In this work, we have pioneered the use of NaY zeolite as an open framework container to selectively load one or more functional object species with a sustained release effect for paper preservation. Based on this strategy, a series of MgO-modified NaY with an adjustable basic oxide amount was obtained, and it appears that with the coating of such composite materials, paper degradation can be effectively controlled by slowing down the acidification and maintaining a desired and moderate pH value between 7.53 and 9.11. Moreover, by cofunctionalization with Ag species, the coated paper can further tolerate the erosion of several typical ancient book fungi, such as Aspergillus niger, Trichoderma viride, and Paecilomyces variotii. Further, it is worth mentioning that the coating of functional NaY not only makes little aberration to the original chromatic property and water wettability of paper but also triggers no color changes of alkali-sensitive pigments (fading or blanching), as the side effects because of the introduction of overstrong alkalinity usually caused by traditional deacidification agents can be avoided. These unique characteristics are promising for the functional zeolite composites in the intelligent protection of paper-based materials and relics.
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