Passive Vhf Radar Folded Antenna Design And Research

Antenna is an important part of radar. It is mainly used for effective directional radiation or receiving electromagnetic waves. And at the same time, it is also an energry converter which converts the energy in the form of high frequency current into energy of radio waves with the same frequency and vice versa. The performance of the antenna depends on the accuracy of the antenna structure, whereas the former directly effects on whether the radar can work normally or not.However, under the circumference of complex global situations, methods of tracking and detection are more sophisticated than ever before. To the radar itself, security is a big problem, which becomes severer and severer. Passive radar is a kind of radar which only receives signals without signal transmission. This brings it about the capability of good stealth, which means it is difficult for the enemy to detect it while the radar detects and tracks the targets. Therefore, passive radar, which is a group indispensable powerful force in national modern defence, is an important branch of radar development.The article introduces a kind of passive radar with large antenna structure and high mobility. In the demonstration of the structure scheme, we cannot found any off-the-peg cases for reference. So we have to employ a new form of antenna structure rather than a traditional one. Major jobs from several aspects listed below are taken into consideration in the process of demonstration and design of the antenna scheme:In order to meet the requirements of antenna rigidity and strength performance in specified environment, modal and static finite element analysis is necessary to be carried out on the antenna itself for the purpose of estimating the natural frequency of the antenna so as to prevent the occurrence of wind oscillation and resonance owing to the servo driving part with the antenna as well. Antenna structure test in tunnel is a very important work, which needs to be implemented before finite element analysis so as to test its wind factor together with wind torque factor during operation and obtain the initial external load.Folding and unfolding operation and automatic fast locking of large radar are implemented in order to meet the requirements of radar mobility. How to realize folding and unfolding operation of the radar antenna is a key technique in designing antenna structure due to the restriction of dimensions of unfolding mechanism in the space. First, mechanism design is implemented according to the motion track, and then, analysis and computation is carried out on the mechanism itself. Another key technique in antenna structure design is locking the working state of the antenna after it has been unfolded. The traditional locking techniques aren't suitable for radar of high mobility. However, when the new locking mechanism is applied, it is necessary to carry out sufficient analysis and simulation computation on the performance of reaching the position and locking, automatic unlocking along with the reliability of realization of the action.Besides reflector structure of the antenna itself, auxiliary mechanical equipment, elevating tower of big head and small bottom in shape and big pedestal with integrated design, which are all reliable auxiliary structures for normal operation of the antenna in complex environment, are needed.