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In this letter, a Taylor-surrogate-model-based method (TSMBM) is proposed to predict the bounds of power pattern of array antennas with interval position errors of antenna elements. The advantage of TSMBM is that it provides the approximate analytical solution of the problem with high precision and free of “wrapping effect.” First, the integral form of the Taylor surrogate model (IFTSM) of the distorted power pattern of array antennas is deduced. Then, the extrema point vector of IFTSM can be readily calculated within a set composed of bounds, –1 and 1. Finally, the bounds of the distorted power pattern are determined by submitting the extrema point vector of IFTSM to the distorted power pattern. Representative examples are presented to demonstrate the accuracy and effectiveness of the method.

Active phased array antennas (APAAs) can suffer from the effects of harsh thermal environments, which are caused by the large quantity of power generated by densely packed T/R modules and external thermal impacts. The situation may be worse in the case of limited room and severe thermal loads, due to heat radiation and a low temperature sink. The temperature field of the antenna can be changed. Since large numbers of temperature-sensitive electronic components exist in T/R modules, excitation current output can be significantly affected and the electromagnetic performance of APAAs can be seriously degraded. However, due to a lack of quantitative analysis, it is difficult to directly estimate the effect of temperature on the electromagnetic performance of APAAs. Therefore, this study investigated the electromagnetic performance of APAAs as affected by two key factors&mdash, the uniformly distributed temperature field and the temperature gradient field&mdash, based on different antenna shapes and sizes, to provide theoretical guidance for their thermal design.

MEMS phase shifter has many advantages as the ‘steering wheel’ of phased array antenna beam steering. The deformation of mechanical structures of MEMS phase shifter influenced by the complex environmental factors, which became the biggest obstacle to further enhance the performance of phased array antennas. The electromechanical coupling model between the bridge height and phase shift of the distributed MEMS phase shifter is developed. The coupling model could be used to predict the phase error and determine the bridge height tolerance for the deformed MEMS phase shifter. The simulation results of four-bit distributed MEMS phase shifter with 15 bridges illustrate the validity of coupling model and demonstrate the application potential for engineering design and test.

The position error of array antenna significantly deteriorates the gain and sidelobe of the array, which seriously hinders the realization of high performance of communication antenna for Internet of Things (IoT). Based on the sensitivity analysis theory, the sensitivity of the array radiation field with respect to the position of the antenna element is derived. Besides, a novel design method of position tolerance for array antenna is proposed and applied to a 20×20 planar array. Compared with the array designed by traditional method, the gain loss is basically the same (being 0.5 dB), while the peak sidelobe level is lowered by 1.937 dB (φ=0°)/1.586 dB (φ=90°). Besides, the uncertainty analysis results show that the newly designed array has a much higher chance to achieve the desired performance, which fully demonstrates the innovation and effectiveness of the new method.

Chitosan/nano-hydroxyapatite composites with different weight ratios were prepared through a co-precipitation method using Ca(OH)(2), H(3)PO(4) and chitosan as starting materials. The properties of these composites were characterized by means of TEM, IR, XRD, burn-out test and universal matertial test machine. Additionally, in vitro tests were also conducted to investigate the biodegradability and bioactivity of the composite. The results showed that the HA synthesized here was poorly crystalline carbonated nanometer crystals and dispersed uniformly in chitosan phase and there is no phase-separation between the two phases. Because of the interactions between chitosan and n-HA, the mechanical properties of these composites were improved, and the maximum value of the compressive strength was measured about 120 MPa corresponding to the chitosan/n-HA composite with a weight ratio of 30/70. The specimens made of 30/70 chitosan/n-HA composite exhibit high biodegradability and bioactivity when being immersed in SBF solutions. The composite is appropriate to being used as scaffold materials for bone tissue engineering. (c) Springer Science + Business Media, Inc.

Porous scaffolds made of n-HA/PA66 composite were fabricated through porogen-leaching technique. The structure, phase and morphology of the scaffolds were investigated by using IR, XRD and SEM, and the physical properties were also studied. The results indicated that the two phases in the composite dispersed uniformly and chemical bonding existed between the two phases. The porosity was proportional to the content of the porogen, and macropores and micropores coexisted and interconnected in the scaffolds. When the porosity was up to 80%, the porosity and the mechanical strength of the scaffolds prepared can meet the demands of tissue engineering simultaneously.