【作者】 刘宇；

【导师】 肖沙里；

【作者基本信息】 重庆大学 ， 光学工程， 2007， 硕士

【摘要】 当今世界的军事冲突和局部战争形式,已从传统的武器比拼上升为“信息作战”。在战场环境下,如何建立和维持抗截获、抗干扰、安全隐密的作战单元无线局域网,是外军和我军普遍关注的两大难题。目前常用的通信系统可以大致分为有线通信、依托射频(RF)的无线电通信系统以及依托红外和可见光通信系统三个大类。无线电通信具有技术成熟的优点,但同时无线电信号也易被敌方截获、测向和干扰,信息的保密性相对不足;有线通信传输性能稳定,通信质量较高,保密性较好,是军事通信的重要手段,但存在通信线路建设时间长,投资大,维护困难,机动性差,易遭受破坏等缺点。自由空间光通信(FSO)技术相对无线电通讯具有灵活,难以截获等优点。而传统的FSO技术采用红外光作为传输载体,在一些特定的环境中容易受到干扰而难以正常工作。为了克服以上各种通信方式的不足,各国军事部门正在寻求新的通信媒介。值得注意的是,据报道近年来美国GTE公司(通用电话和电子设备公司)已为美军研制了一种新型隐蔽式紫外光通信系统,从而对我军通信能力的发展提出了严峻的考验。由于大气层的阻挡作用,地面上没有波长低于290nm的紫外线,以日盲紫外光通信为通信载体的新一代通信系统将不会受白昼和夜晚环境的影响,从而大大提高了通信的抗干扰能力。该系统还具有灵活、低窃听、全方位、并具有非视距通讯的独特优势,可满足军舰、飞机编队之间的保密通讯需要。此外,由于紫外线具有在大气中漫反射的特性,采用紫外光通讯系统,还具有一定的绕过障碍物的能力。对紫外光进行调制与解调一直是该系统的一个难题。采用调频技术对紫外气体放电灯进行频率加载调制,将电信号转换为光信号,再在接收端将接收到的光信号转换为电信号,并进行信号的频/压转换,还原出调制端加载的数字信号。该方法具有信号稳定,易于实现的优点。同时,紫外通信系统的传输速度难以提高,目前全球最快的仅为4800bps,无法直接满足语音传输的速度要求,因而,语音的实时压缩技术也成为该系统的关键点。选用MELP语音压缩编解码技术,应用DSP的实时高速的处理能力,对数字语音信号进行实时有效的滤波和压缩处理,以满足紫外通信系统的实时语音传输速度要求。该套解调系统使用灵活,性能稳定,通过室外的测试证明,一公里的范围内,在1.2kbps传输速率上可实现较为可靠的字符传输。对语音解码系统进行单独测试时,能够实现2.4kbps速率的实时处理。然而对整个系统进行语音通信时,由于解调系统在传输速率达到2.4kbps时,误码率较高,导致语音的质量较差,甚至部分音段难以分辩。因而,还需要对解调器件及语音压缩方案进行进一步的完善和改进,并对电路中的一些关键控制参数做出进一步优化,以实现全双工,高质量的适时通信。更多还原

【Abstract】 In today’s world, warfare forms of military conflicts and local wars have changed from traditional weapons to“Information Warfare”. In battlefield environment, establishing and maintaining anti-capture and anti-jamming secure wireless local area network has been focused by foreign force and our force. At present, common communication systems can be roughly divided into three categories: Cable Communication, relying on radio frequency (RF) wireless communication systems and relying on infrared and visible light communications. Radio communication has the mature technology advantages, but it is also susceptible to radio signals intercepted, and to the measured interference. The confidentiality of information is relative shortage. Cable communication with stable performance, higher quality and better confidentiality is an important military communication means, but there are some disadvantages, such as: long time to be built, great investment, difficult maintenance, poor mobility and vulnerable to be damaged. Compared with Radio communication, Free Space Optical Communications (FSO) technology has flexible and anti-intercepted advantages. However, the traditional FSO technologies use infrared light as a transmission medium. In specific environment, it is susceptible to interference to normal work.To overcome all of above insufficient, States military is looking for a new medium of communication. It is noteworthy that the United States GTE Corporation (telephone and electronic equipment company) has developed a new concealed - UV communication system for the U.S. military in recent years, thus, our communication capabilities of the development have been toughly challenged. By reason of the atmosphere, there is not below the 290 nm wavelength UV on the ground. A new generation of communication system using Solar-blind UV as medium will not be affected by daytime and nighttime environment, thus the communication ability of anti-jamming can be greatly improved. The system also has some unique advantages, such as flexible, all-round, and non-line-of-sight communication, and can meet warships, aircraft squadron confidentiality communications needs. Moreover, the UV has diffuse reflectance characteristics in the air. Ultraviolet communication system also has the ability to bypass the barrier.Modulation-demodulation of the UV is still a difficulty. Applying FM technology to UV gas discharge lamp load modulation frequency, the electric signals will be converted into optical signals. Then the receiver will receive optical signals, which are converted to electrical signals and carried on frequency-to-voltage conversion. Finally, the original digital signal can be gained. The demodulation system has some advantages: stable signal, easy to realize its benefits. Meanwhile, it is difficult to improve the speed of transmission for UV communication system, the fastest speed is only 4800bit/s in the world by far and not directly matches voice transmission speed. Consequently, the real-time voice compression technology has become the key point of the system. Making use of MELP speech compression codec technology, digital audio signal can be effective real-time filtered and compressed by means of real-time and high-speed processing capability of DSP, in order to meet the real-time voice transmission demand of UV communication system.The demodulation system is flexible and stable. Within the one-kilometer area, the transmission rate is up to 1.2kbps, and can be carried on reliable transmission of the characters through outdoor tests. Through a separate test, speech decoding system can achieve the rate of 2.4kbps real-time processing. Nevertheless, on the whole system’s tests for voice communications, as the error rate of demodulation system is high at 2.4kbps transmission rate, the speech quality is poor, and even some of the sound is difficult to differentiate. Thus, the demodulation devices and voice compression scheme need to be further refined and improved, while some of the key control parameters of circuit need to be further optimized, in order to achieve full-duplex, high-quality and real-time voice communication.更多还原