Passive Coherent Location Research And Design Of The Antenna Feeder Subsystem

The Passive Coherent Location (PCL) system is a kind of passive radar. This system can detect and locate the goals that relys on external non-coordinational radiator,and the feature of does not radiate electromagnetic energy is highly advantageous to its security. It is known as the "nemesis" of the stealth aircraft because it can take advantage of rich low-frequency spectrum which is helpful to detect stealthy and low-altitude targets. For this reason,the PCL system has been paid attention and studied widely.The antenna is the "eye" of the PCL system and is very important to the system's performance. In order to achieve enough detection range and positioning accuracy,the phased array technology is often used in PCL systems. In this thesis,the sub-system of antenna and feed in PCL system which roots from an engineering practice are studied comprehensively. The design methods , implementary scheme and test approach of the main antenna array are also presented.Moreover,some introductions and the simulation of pattern nulling are described in chapter 2.The sub-system of antenna and feed in PCL system which works in VHF band can be divided into four functional blocks: main antenna array,feed, beam controller and direct-wave antenna array. The main antenna array is the core of the PCL system. A dual-beam synchro-scanning phased array with the low-sidelobe feature and a cosecant shaped pattern is adopted as the main antenna array. This array which has the dimension of 20×12m is composed of 32×8 cells by 256 log-periodic dipole antennas and according to a triangle arrangement. The beams of the main array can be scanned within±30deg in elevation plane and the gain is greater than 28dB. The testing results in outfield are well-pleasing and the sub-system of antenna and feed is competent for the PCL system.This thesis uses the theoretical knowledge that mainly includes the basic working principle of phased array, feed technology,beam control and pattern synthesis etc. The engineering-oriented problems involve simulation of antenna cells,feed arrangement, framework design and antenna measurement outdoors.Hope that this thesis may contribute to the study of PCL system and Phased Array.