中英对照调频通信

1、跳频通信一、跳频技术无线电通信是战时通信的必备手段，但是，传统的无线电通信都是在某一固 定频率下工作，很容易被敌方截获或施加电于干扰，从而使通信失灵。跳频通信就是针对传统无线电通信的弊端，使原先固定不变的无线电发信频 率按一定的规律和速度来回跳变。从抗干扰通信角度来看，跳频通信是靠载频的 随机跳变来躲避干扰，将干扰排斥在接收信道以外来达到抗干扰的目的，避免敌 方电台的测向和干扰。跳频通信技术在抗干扰通信方面的突岀优势，使其在通信 装备中得以广泛应用，并且成为超短波通信装备的主要抗干扰技术。跳频技术不仅是抵御外来干扰的能手，而且对于抑制远距离无线电通信本身 所造成的多径干扰也十分有效。因为采用跳

2、频技术后，由于在主波波束己被接收, 而其他径向波束尚未到达接收机时，发送和接收载频早已跳到别的频点上，因而 避免了多径效应对通信质量的影响。二、跳频通信的关键技术1跳频图案用来控制载波频率跳变的地址码序列通常称为跳频序列。在跳频序列控制下，载 波频率跳变的规律称为跳频图案。2频率合成嚣跳频通信系统的可变频率合成器是系统的核心部分，跳变频率的总和与跳频速率 决定了系统的抗干扰能力。从原理上说，跳频通信系统的可变频率合成器与普通 的频率合成器没什么不同，但有两个特点。一是受跳频序列控制，跳频数增加则 扩展的频率越宽，系统的处理增益就越大；二是能足够快的跳变频率，使系统能3同步技术对跳频系统来说，同

3、步就是收、发两端的频率必须具有相同的变化规律，即每 次跳变频率上有确切严格的对应关系。具体而言，要求做到以下两点：一是使表 示接收机的跳频图案与发射机跳频图案相一致，这样才能通过混频器(相乘)来完 成解跳。二是提取接收信号的载波频率，用它对接收信号作相关检测，解调信息三、对跳频通信的干扰跳频通信干扰的四个必要条件(1) 旳域条件：由于频率跟踪瞄准式干扰是实时测量出跳变的频率，并在该 频率上发射干扰信号，因为干扰设备反应时间和电波传播时间的影响，干扰信号 的发射时间总是滞后于通信信号。在信号频率的驻留时间内，只要有50%的时 间被干扰,就可以达到有效干扰。这就要求从干扰设备的引导接收机截获到信号

4、, 到干扰信号到达接收机的总延迟时间，必须不小于信号驻留时间的5()%。(2) 空域条件：是指跳频通信发信机、接收机以及干扰机所处的地理位置应 该满足的数学关系。为了有效地干扰跳频系统，在通信频率跳到新的频率之前，干扰机必须完成从侦 听到施放干扰的全过程。频域条件：干扰频谱与跳频通信信号中携带信息的频谱相重合，这样，在频 域就难以将二者分开干扰机采用线性宽频带实时测出跳变频率，在进行处理前 进行验证比对，看是否满足相等条件，满足则实施干扰信号发射，不满足则继续 搜频。被干扰的佶道数占跳频总信道数的比例与跳速和信号形式有关，但是，无 论哪种跳速和信号形式，只要干扰7 50%以上的信道，都可以达到

5、有效干扰的目的。(4)能域条件：一般情况下，干扰信号应具有压制敌方通信所需的干扰频率。对跳频通信最有效的干扰是以下三种：(1)窄带频率瞄准式干扰：用于干扰单个信道的窄带干扰。窄带频率瞄准式干 扰，先由引导接收机搜索截获并分析信号，然后选择最好的干涉样式启动发射 机开始按照需要功率进行干扰，在某一个频率上施放长时间的大功率的干扰，即 单频 干扰。(2)拦阻式干扰：用于干扰一个频段内多个信道的宽带干扰。拦阻式干扰，先 进行线性扫频，然后根据扫到的频率范围，实施连续拦阻式干扰或者梳状拦阻式 干扰。它按频率范围分为全频段和部分频段干扰。频率跟踪瞄准式干扰：这种干扰方式是实时测量出跳变的频率，并且它结合

6、了 窄带频率瞄准式干扰和拦阻式干扰的优点，采取一种折中的方法，即也采用窄 带干扰，避免了拦阻式干扰由于干扰功率分散在很宽的频段上而需要很高的干扰 功率，由使用了全频段扫描，采用跟频干扰，提高了窄带频率瞄准式干扰的灵活 性。四、跳频技术在商业移动通信中的作用在业务密集区，GSM系统的容量受频率复用产生的干扰限制，相对载干比 可能在呼叫之间有很大的变化。载波电平一般随移动台与基站的距离及相互间的 障碍情况变化而变化。而干扰电平则在很大程度上依赖于邻近小区的同频干扰。 由于系统的目标是尽可能满足更多用户的要求，当不选用跳频时，若某一频点出 现干扰，当某用户占用该频点时就会造成通话质量下降，而使用户难

7、以接受，若 干扰是连续的，很容易造成质量差掉话。当使用跳频时，该干扰情况就会被该载 波的其他呼叫所共亭，干扰被平均了，干扰不再处于连续状态，而处于突发状态, 整个网络的性能将得到很大提高。经分析，使用跳频的网络可比不采用跳频的网 络高3dB的增益。GSM系统中采用慢跳频技术，跳频速率为217跳/秒，跳频在 两个时隙间进行，一个时隙内用固定频率收发，下一时隙用另一频率收发，以减 小干扰的影响。Frequency HoppingFirst, the frequency hoppingRadio communication is ail essential means of communicatio

8、n during the war, but traditional mdio communications arc working under a fixed frequency, the enemy call easily be intercepted or impose electronic interference, so that the communication failureFrequency Hopping is the drawbacks of traditional radio communications, so that the original letter fixe

9、d radio frequency :ind speed at a certain law of jump back and forth Communication from the interference point of view, the carrier frequency hopping communication is by a random jump to avoid interference, the interference rejection at the receiver interference channel to achieve the purpose other

10、than to avoid enemy radio direction finding and jamming. Frequency-hopping communication technology- in anti-jamming communications of the outstanding advantages, so that it can be widely used in communication equipment, and VHF communications equipment as the main interference technology-.Frequency

11、 hopping is not only a skilled defense against externd interference, and for the suppression of long-distance radio communications caused by itself is also very effective multi-path interference. Because the use of frequency hopping, due in the main wave beam has been received, while the other radia

12、l beams have not vet reached the receiver, the transmit and receive carrier frequency on the long jump to another frequency, thus avoiding the multipath effects on the quality of communication effects.Second, the key technology of frequency hopping communication1 hopping patternUsed to control the a

13、ddress of the carrier frequency hopping code sequence is often referred to as frequency hopping sequence. Under the control of the frequency hopping sequence, the law of frequency hopping carrier called the frequency hopping patterns.2 Synthesis dinFrequency hopping communication system is a system

14、variable frequency synthesizer core part of the sum of the frequency hopping rate determines the frequency hopping system yrith anti-jamming capability' From the principle that the frequency hopping communication system with common variable frequency synthesizer frequency synthesizer is no diffe

15、rent, but there arc two characteristics First, controlled by the frequency hopping sequence, frequency hopping to increase the number of widur expansion of the frequency, the greater the system processing gain; the second is to jump fast enough frequency, the system can quickly jump from one frequen

16、cy to another frequency , to avoid the f(>rwarding of external interference.3 SynchronizationJFor frequency hopping systems, synchronization is the sending and recchnng ends must have the same frequency of variation, that is, evury time there is a definite frequency hopping strict correspondence.

17、 In particular, the requirement to do two things： First, the hopping pattern so that the receiver and transmitter frequency hopping pattern is consistent, so to come through a mixer (multiplication) to complete the solution jump. Second, extract the received signal carrier frequency, using the recei

18、ved si何al as it related to detection, demodulation informationThird, interference of frequency hopping communicationFrequency Hopping four necessary conditions fi)r interference(1) timc-domaill conditions： the frequency tracking target is the real-time measurement of the jamming frequency hopping an

19、d interference in the transmitting frequency signals, because interference duvicu response time and the impact of wave propagation time, launch time is always interfering signals lag behind the communication signals. Dwull time at the signal frequency, as long as 50% of the time be disturbed you can

20、 achieve effective interference. This requires guidance from the jamming equipment was intercepted in the receiver signal to the interference signal reaches the receiver, the total delay time, the signal must not be less than the dwell time in 5()%(2) airspace conditions： is the frequency hopping co

21、mmunication transmitter, receiver and jammer geographical location should satisfy the mathematical relationships.In order to effectively interfere with frequency hopping system, the communication frequency to jump bcf()rc the new frequency, the jammer must complete release from listening to the whol

22、e process of interference(3) FtcCjUCllCy Domain： The Spectrum and frequency hopping communication signal to carry- information in the spectrum coincide, so that in the frequency domain is difficult to separate the two linear wickband jammer hopping frequencies measured in real time, during treatment

23、 Verify bcf()rc comparing to see if it meet the same conditions to meet the implementation of the interference signal transmission, docs not meet the continued search frequency. Ji Road disturbed accounted hopping ratio of total number of channels and the format of the hop rate and signal, but, what

24、ever the form of hop rate and signal, as long as more than 50% interfered channel, can Jichievu the purpose of cffcctix interference(4) to field conditions： normal circumstances, the interference signal should be required to communicate with the suppression of enemy interference frequency.The most e

25、ffective of frequency hopping communications interference is the following three:(1) narrow-band frequency of target-type interference: interference wth a single channel f()r narrowband interference. Aimed at jamming the frequency band, first intercepted and analyzed to guide the search signal recei

26、ver, and then choose the best transmitter interference pattern starts to interfere with the beginning in accordance： with the needs of power, at a certain frequency, the interference of high-power cast a long time, that single- FrequencyInterference.(2) bl()ck-trpc interference! interference with a

27、band for multiple channels of wideband interference. Bk)ck-t*pc interference, the first linear sweep, and then sweep the frequency range, the implementation of a continuous block or comb block jamming jamming. It is divided by Rill-band frequency range and partial band interference.(3) frequency tra

28、cking target type interference: the intcrfcrcncc method is measured in real time the frequency hopping, and it combines the targeting frequency band jamming jamming and blocking the merits, to take a compromise approach that also uses narrow-buid interference, to avoid jamming due to interference bl

29、ocking scattered over a wide power band and need a vcr)r high interference power, by using a full band scan, the use of interfering wth the frequency, narrow-band frequency increased the flexibility of targeting jamming.Fourth, frequency hopping in the role of commercial mobile communicationIntensiv

30、e areas in the business, GSM system capacity by frequency reuse interference from restrictions, and the relative carrier to interference ratio mav vary widely betxen calls Carrier levelJJJgenerally increased with distance from the mobile station and base station and the barriers bcccn each other and chan牛 the situation. The interference level is largely dependent on the neighboring district of the same frequency in