KDX-87型甚低频宽带定向接收与微机分析系统

KDX-87 RECEIVING AND ANALYSING SYSTEM FOR VLF WIDE-BAND DIRECTION FINDING

本文介绍了武汉大学哨声组研制的KDX-87型甚低频宽带定向接收与微机分析系统.该系统适用于测量与分析哨声波传播路径出口、偏振和动态谱.此系统具有以下优点:1.设计制造了小型化天线和便携式接收机,便于携带和架设;合理设计了输入耦合与平衡电路,加上有效的标定方法,使接收系统具有良好的频率响应和通道间性能的一致性.2.实现了数字化宽频带定向分析,有利于减小多路径效应误差,并可获得哨声路径出口与波频率之间的关系.3.利用微机进行哨声动态谱分析,采取了有效的抑制干扰处理,所得谱图分辨率优于普通声图仪制作的谱图.该系统在1988年中日联合哨声定向实验中使用,取得了满意的结果.

The KDX-87 receiving and analysing system for VLF wide-band direction finding (DF) developed by whistler group of Wuhan University is described. This system is suitable for measuring and analysing the exit area, polarization state and dynamic spectrum of whistler waves, and can be extended to locate the long-distance lightning and VLF navigation signals etc.. The system has the following advantages: 1. Snail size antennas and portable receiver are adopted, which makes it convenient to take and set up the receiving system in the field. 2. The coupling and balancing circuits between antennas and receiver are properly designed and an effective calibration technique is used, thus enabling the system to have a good frequency response and an uniformity of properties between different channels. 3. By utilizing the frequency-modulation characteristic of whistler signals, frequency-tracking wide-band DF is realiz-ed; in comparison with the traditional method of narrow-band DF, the DF errors produced by multipath effects are greatly minimized and additional information on the relationship be- tween wave frequencies and exit points of whistler path can be obtained. 4. A digitized goniometer is developed as a result of improving the traditional analogue goniometer. With a coordinate use of two methods of goniometer and field-analysis, satisfactory DF results can be obtained under either conditions of long and short distance between whistler exit and receiver. 5. The whistler dynamic spectra are analysed through a microcomputer with an effective process of removing interferences performed in advance, and the resulted spectrograms show much better resolution than that made by an ordinary sonagraph. By using the KDX-87 system, some valuable DF results have been got in the low-latitude whistler DF experiments which were carried out cooperatively by Chinese and Japanese researches.