为了提高高轨电子侦察卫星对雷达信号的侦收灵敏度,增大截获概率,提出了一种基于天线波束偏转的雷达主瓣侦收方法。根据雷达辐射源最大仰角,高轨卫星可以获得雷达信号的主副瓣侦收区域。通过天线波束在短时间内进行特定方向和一定角度...为了提高高轨电子侦察卫星对雷达信号的侦收灵敏度,增大截获概率,提出了一种基于天线波束偏转的雷达主瓣侦收方法。根据雷达辐射源最大仰角,高轨卫星可以获得雷达信号的主副瓣侦收区域。通过天线波束在短时间内进行特定方向和一定角度的偏转,使指向雷达副瓣的天线波束实时对准雷达主瓣侦收区域,实现雷达主瓣侦收。仿真实验结果表明:取雷达主瓣最大仰角为40°、天线波束宽度为2°,通过天线波束偏转7.6°,可完成雷达辐射源主瓣侦收;与副瓣侦收相比,主瓣侦收信号信噪比至少可提高12.24 d B。展开更多
Largest portion of the bridge stock in almost any country and bridge owning organisation consists on ordinary bridges that has short or medium spans and are now deteriorating due to aging, etc. Therefore, it is becomi...Largest portion of the bridge stock in almost any country and bridge owning organisation consists on ordinary bridges that has short or medium spans and are now deteriorating due to aging, etc. Therefore, it is becoming an important social concern to develop and put to practical use simple and efficient health monitoring systems for existing short and medium span (10 - 30 m) bridges. In this paper, one practical solution to the problem for condition assessment of short and medium span bridges was discussed. A vehicle-based measurement with a public bus as part of a public transit system (called “Bus monitoring system”) has been developed to be capable of detecting damage that may affect the structural safety of a bridge from long term vibration measurement data collected while the vehicle (bus) crossed the target bridges. This paper systematically describes how the system has been developed. The bus monitoring system aims to detect the transition from the damage acceleration period, in which the structural safety of an aged bridge declines sharply, to the deterioration period by continually monitoring the bridge of interest. To evaluate the practicality of the newly developed bus monitoring system, it has been field-tested over a period of about four years by using an in-service fixed-route bus operating on a bus route in the city of Ube, Yamaguchi Prefecture, Japan. The verification results thus obtained are also described in this paper. This study also evaluates the sensitivity of “characteristic deflection”, which is a bridge (health) condition indicator used by the bus monitoring system, in damage detection. Sensitivity of “characteristic deflection” is verified by introducing artificial damage into a bridge that has ended its service life and is awaiting removal. As the results, it will be able to make a rational long-term health monitoring system for existing short and mediumspan bridges, and then the system helps bridge administrators to establish the rational maintenance strategies.展开更多
文摘为了提高高轨电子侦察卫星对雷达信号的侦收灵敏度,增大截获概率,提出了一种基于天线波束偏转的雷达主瓣侦收方法。根据雷达辐射源最大仰角,高轨卫星可以获得雷达信号的主副瓣侦收区域。通过天线波束在短时间内进行特定方向和一定角度的偏转,使指向雷达副瓣的天线波束实时对准雷达主瓣侦收区域,实现雷达主瓣侦收。仿真实验结果表明:取雷达主瓣最大仰角为40°、天线波束宽度为2°,通过天线波束偏转7.6°,可完成雷达辐射源主瓣侦收;与副瓣侦收相比,主瓣侦收信号信噪比至少可提高12.24 d B。
文摘Largest portion of the bridge stock in almost any country and bridge owning organisation consists on ordinary bridges that has short or medium spans and are now deteriorating due to aging, etc. Therefore, it is becoming an important social concern to develop and put to practical use simple and efficient health monitoring systems for existing short and medium span (10 - 30 m) bridges. In this paper, one practical solution to the problem for condition assessment of short and medium span bridges was discussed. A vehicle-based measurement with a public bus as part of a public transit system (called “Bus monitoring system”) has been developed to be capable of detecting damage that may affect the structural safety of a bridge from long term vibration measurement data collected while the vehicle (bus) crossed the target bridges. This paper systematically describes how the system has been developed. The bus monitoring system aims to detect the transition from the damage acceleration period, in which the structural safety of an aged bridge declines sharply, to the deterioration period by continually monitoring the bridge of interest. To evaluate the practicality of the newly developed bus monitoring system, it has been field-tested over a period of about four years by using an in-service fixed-route bus operating on a bus route in the city of Ube, Yamaguchi Prefecture, Japan. The verification results thus obtained are also described in this paper. This study also evaluates the sensitivity of “characteristic deflection”, which is a bridge (health) condition indicator used by the bus monitoring system, in damage detection. Sensitivity of “characteristic deflection” is verified by introducing artificial damage into a bridge that has ended its service life and is awaiting removal. As the results, it will be able to make a rational long-term health monitoring system for existing short and mediumspan bridges, and then the system helps bridge administrators to establish the rational maintenance strategies.
