Study RF Front-end Technology Near Space

With the high requirement in system transmission capability and space height, the research on data-link broad band radio frequency (RF) front-end character and near space environment adaptability are necessary. Based on this requirement, this paper is mainly research on unmanned aerial vehicle’s (UAV) multi-band data-link radio frequency front-end character.Based on the practical engineering requirement, the equipment of UAV data-link broad band RF front-end is studied, simulation and implementation about RF front-end and its part, a general standard modularized simulation platform is established. Analysis about filter design method of RF front-end near space in this paper. Studied how the passive intermodulation power arising in air cavity filters could be calculated and how the design of the filter could be optimized in order to reduce the amplitude of the PIM signal and to increase power handling.For the passive intermodulation(PIM) problem, two PIM amplitude and power level predict method is given by analysis the PIM between different band and multiple carrier in one band; one method deduced two order and three order relationship between intermodulation result and input power using Fourier series, another method gives mathematical analyzed statistical character of all disturbance including PIM disturbance using multiple carrier emit band flatheaded spectrum. The PIM power spectrum density function is deduced.The measurement method and its feasibility and validity are given.For multipactor discharge phenomenon the RF signal on condition of near space low voltage, a engineering depress measure is proposed, the measurement method is also proposed combine with engineering projects.