中英對(duì)照 調(diào)頻通信

1、跳頻通信一、跳頻技術(shù) 無線電通信是戰(zhàn)時(shí)通信的必備手段，但是，傳統(tǒng)的無線電通信都是在某一固定頻率下工作，很容易被敵方截獲或施加電子干擾，從而使通信失靈。 跳頻通信就是針對(duì)傳統(tǒng)無線電通信的弊端，使原先固定不變的無線電發(fā)信頻率按一定的規(guī)律和速度來回跳變。從抗干擾通信角度來看，跳頻通信是靠載頻的隨機(jī)跳變來躲避干擾，將干擾排斥在接收信道以外來達(dá)到抗干擾的目的，避免敵方電臺(tái)的測向和干擾。跳頻通信技術(shù)在抗干擾通信方面的突出優(yōu)勢(shì)，使其在通信裝備中得以廣泛應(yīng)用，并且成為超短波通信裝備的主要抗干擾技術(shù)。 跳頻技術(shù)不僅是抵御外來干擾的能手，而且對(duì)于抑制遠(yuǎn)距離無線電通信本身所造成的多徑干擾也十分有效。因?yàn)椴捎锰l技術(shù)

2、后，由于在主波波束己被接收，而其他徑向波束尚未到達(dá)接收機(jī)時(shí)，發(fā)送和接收載頻早已跳到別的頻點(diǎn)上，因而避免了多徑效應(yīng)對(duì)通信質(zhì)量的影響。二、跳頻通信的關(guān)鍵技術(shù) 1跳頻圖案用來控制載波頻率跳變的地址碼序列通常稱為跳頻序列。在跳頻序列控制下，載波頻率跳變的規(guī)律稱為跳頻圖案。 2頻率合成囂跳頻通信系統(tǒng)的可變頻率合成器是系統(tǒng)的核心部分，跳變頻率的總和與跳頻速率決定了系統(tǒng)的抗干擾能力。從原理上說，跳頻通信系統(tǒng)的可變頻率合成器與普通的頻率合成器沒什么不同，但有兩個(gè)特點(diǎn)。一是受跳頻序列控制，跳頻數(shù)增加則擴(kuò)展的頻率越寬，系統(tǒng)的處理增益就越大；二是能足夠快的跳變頻率，使系統(tǒng)能夠很快的從一個(gè)頻率跳到另一個(gè)頻率，躲避來自

3、外部的轉(zhuǎn)發(fā)性干擾。 3同步技術(shù)對(duì)跳頻系統(tǒng)來說，同步就是收、發(fā)兩端的頻率必須具有相同的變化規(guī)律， 即每次跳變頻率上有確切嚴(yán)格的對(duì)應(yīng)關(guān)系。具體而言，要求做到以下兩點(diǎn)：一是使表示接收機(jī)的跳頻圖案與發(fā)射機(jī)跳頻圖案相一致，這樣才能通過混頻器(相乘)來完成解跳。二是提取接收信號(hào)的載波頻率，用它對(duì)接收信號(hào)作相關(guān)檢測，解調(diào)信息三、對(duì)跳頻通信的干擾 跳頻通信干擾的四個(gè)必要條件（1）時(shí)域條件：由于頻率跟蹤瞄準(zhǔn)式干擾是實(shí)時(shí)測量出跳變的頻率，并在該頻率上發(fā)射干擾信號(hào)，因?yàn)楦蓴_設(shè)備反應(yīng)時(shí)間和電波傳播時(shí)間的影響，干擾信號(hào)的發(fā)射時(shí)間總是滯后于通信信號(hào)。在信號(hào)頻率的駐留時(shí)間內(nèi)，只要有50 的時(shí)間被干擾，就可以達(dá)到有效干擾。這

4、就要求從干擾設(shè)備的引導(dǎo)接收機(jī)截獲到信號(hào)，到干擾信號(hào)到達(dá)接收機(jī)的總延遲時(shí)間，必須不小于信號(hào)駐留時(shí)間的5O。（2）空域條件：是指跳頻通信發(fā)信機(jī)、接收機(jī)以及干擾機(jī)所處的地理位置應(yīng)該滿足的數(shù)學(xué)關(guān)系。為了有效地干擾跳頻系統(tǒng)，在通信頻率跳到新的頻率之前，干擾機(jī)必須完成從偵聽到施放干擾的全過程。(3)頻域條件：干擾頻譜與跳頻通信信號(hào)中攜帶信息的頻譜相重合，這樣，在頻域就難以將二者分開 干擾機(jī)采用線性寬頻帶實(shí)時(shí)測出跳變頻率，在進(jìn)行處理前進(jìn)行驗(yàn)證比對(duì)，看是否滿足相等條件，滿足則實(shí)施干擾信號(hào)發(fā)射，不滿足則繼續(xù)搜頻。被干擾的佶道數(shù)占跳頻總信道數(shù)的比例與跳速和信號(hào)形式有關(guān)，但是，無論哪種跳速和信號(hào)形式， 只要干擾了5

5、O以上的信道，都可以達(dá)到有效干擾的目的。(4)能域條件：一般情況下，干擾信號(hào)應(yīng)具有壓制敵方通信所需的干擾頻率。 對(duì)跳頻通信最有效的干擾是以下三種：（1)窄帶頻率瞄準(zhǔn)式干擾： 用于干擾單個(gè)信道的窄帶干擾。窄帶頻率瞄準(zhǔn)式干擾， 先由引導(dǎo)接收機(jī)搜索截獲并分析信號(hào)，然后選擇最好的干涉樣式啟動(dòng)發(fā)射機(jī)開始按照需要功率進(jìn)行干擾，在某一個(gè)頻率上施放長時(shí)間的大功率的干擾， 即單頻干擾。(2)攔阻式干擾：用于干擾一個(gè)頻段內(nèi)多個(gè)信道的寬帶干擾。攔阻式干擾，先進(jìn)行線性掃頻，然后根據(jù)掃到的頻率范圍，實(shí)施連續(xù)攔阻式干擾或者梳狀攔阻式干擾。它按頻率范圍分為全頻段和部分頻段干擾。(3)頻率跟蹤瞄準(zhǔn)式干擾：這種干擾方式是實(shí)時(shí)測

6、量出跳變的頻率，并且它結(jié)合了窄帶頻率瞄準(zhǔn)式干擾和攔阻式干擾的優(yōu)點(diǎn)，采取一種折中的方法， 即也采用窄帶干擾，避免了攔阻式干擾由于干擾功率分散在很寬的頻段上而需要很高的干擾功率，由使用了全頻段掃描，采用跟頻干擾，提高了窄帶頻率瞄準(zhǔn)式干擾的靈活性。四、跳頻技術(shù)在商業(yè)移動(dòng)通信中的作用 在業(yè)務(wù)密集區(qū)，GSM系統(tǒng)的容量受頻率復(fù)用產(chǎn)生的干擾限制，相對(duì)載干比可能在呼叫之間有很大的變化。載波電平一般隨移動(dòng)臺(tái)與基站的距離及相互間的障礙情況變化而變化。而干擾電平則在很大程度上依賴于鄰近小區(qū)的同頻干擾。由于系統(tǒng)的目標(biāo)是盡可能滿足更多用戶的要求，當(dāng)不選用跳頻時(shí)，若某一頻點(diǎn)出現(xiàn)干擾，當(dāng)某用戶占用該頻點(diǎn)時(shí)就會(huì)造成通話質(zhì)量下

7、降，而使用戶難以接受，若干擾是連續(xù)的，很容易造成質(zhì)量差掉話。當(dāng)使用跳頻時(shí)，該干擾情況就會(huì)被該載波的其他呼叫所共享，干擾被平均了，干擾不再處于連續(xù)狀態(tài)，而處于突發(fā)狀態(tài)，整個(gè)網(wǎng)絡(luò)的性能將得到很大提高。經(jīng)分析，使用跳頻的網(wǎng)絡(luò)可比不采用跳頻的網(wǎng)絡(luò)高3dB 的增益。GSM系統(tǒng)中采用慢跳頻技術(shù)，跳頻速率為217跳/秒，跳頻在兩個(gè)時(shí)隙間進(jìn)行，一個(gè)時(shí)隙內(nèi)用固定頻率收發(fā)，下一時(shí)隙用另一頻率收發(fā)，以減小干擾的影響。Frequency HoppingFirst, the frequency hoppingRadio communication is an essential means of communicati

8、on during the war, but traditional radio communications are working under a fixed frequency, the enemy can easily be intercepted or impose electronic interference, so that the communication failure.Frequency Hopping is the drawbacks of traditional radio communications, so that the original letter fi

9、xed radio frequency and 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 othe

10、r 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 external 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 radi

12、al beams have not yet 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

13、address 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 with anti-jamming capability. From the principle that the frequency hopping communication system with common variable frequency synthesizer frequency synthesizer is no different

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

16、 to another frequency , to avoid the forwarding of external interference.3 SynchronizationFor frequency hopping systems, synchronization is the sending and receiving ends must have the same frequency of variation, that is, every time there is a definite frequency hopping strict correspondence. In pa

17、rticular, 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 received si

18、gnal as it related to detection, demodulation informationThird, interference of frequency hopping communicationFrequency Hopping four necessary conditions for interference(1) time-domain conditions: the frequency tracking target is the real-time measurement of the jamming frequency hopping and inter

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

20、ve 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 5O%.(2) airspace conditions: is the frequency hopping communic

21、ation 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 before the new frequency, the jammer must complete release from listening to the whole proce

22、ss of interference.(3) Frequency 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 wideband jammer hopping frequencies measured in real time, during treatment Verify b

23、efore comparing to see if it meet the same conditions to meet the implementation of the interference signal transmission, does 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, whatever the f

24、orm of hop rate and signal, as long as more than 5O% interfered channel, can achieve the purpose of effective interference.(4) to field conditions: normal circumstances, the interference signal should be required to communicate with the suppression of enemy interference frequency.The most effective

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

26、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) block-type interference: interference with a band for mu

27、ltiple channels of wideband interference. Block-type 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 full-band frequency range and partial band interference.(3) frequency tracking targe

28、t type interference: the interference 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-band interference, to avoid jamming due to interference blocking scat

29、tered over a wide power band and need a very high interference power, by using a full band scan, the use of interfering with the frequency, narrow-band frequency increased the flexibility of targeting jamming.Fourth, frequency hopping in the role of commercial mobile communicationIntensive areas in

30、the business, GSM system capacity by frequency reuse interference from restrictions, and the relative carrier to interference ratio may vary widely between calls. Carrier level generally increased with distance from the mobile station and base station and the barriers between each other and change the situation. The interference level is largely dependent on the neighboring district of the same