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In this paper, we establish the existence of smooth center manifolds for a class of nonautonomous differential equations with non-instantaneous impulses under sufficiently small perturbations of the linear homogeneous part which has a nonuniform exponential trichotomy. In addition, we show the $C^{1}$ smoothness of center manifolds outside the jumping times.

A S-band miniaturized circularly polarized microstrip antenna is designed and fabricated. The curved current technique is utilized, and the effective path length of current is increased by loading the U-shaped slot on the radiating patch. Thus the antenna resonant frequency can be tuned and the antenna can be significantly miniaturized. The experimental samples of the antenna are fabricated and tested. The measured results show that the two resonant frequencies of the miniaturized S-band circularly polarized microstrip antenna are 2.17GHz and 2.25GHz, with an impedance bandwidth (S11