【正文】 ”。這兩個序列發(fā)生器產(chǎn)生偽隨機(jī)噪聲（ PN）二值序列，在調(diào)制端將傳送信號在頻域進(jìn)行擴(kuò)展，在解調(diào)端解擴(kuò)該擴(kuò)頻發(fā)送信號。 F 為信號的頻率 。 以絕對標(biāo)高 m 為準(zhǔn)，總長 27樓 ； 30樓 m。 本工程耐火等級二級，屋面防水等級三級，地震防烈度為 8度，設(shè)計使用年限 50 年。所以 ,擴(kuò)頻系統(tǒng)可實(shí)現(xiàn)隱蔽通信 。 2）抗干擾容限 是指擴(kuò)頻通信系統(tǒng)能在多大干擾環(huán)境下正常工作的能力，定義為： ]s)/[( outj LNSGM ??? （ 6） 其中： jM 抗干擾容 G 處理增益 out)/( NS 信息數(shù)據(jù)被正確解調(diào)而要求的最小輸出信噪比 sL 接收系統(tǒng)的工作損耗 擴(kuò)頻通信系統(tǒng)的工作原理 數(shù)字?jǐn)U頻通信的一般工作原理如圖 1 所示。為什么要用這樣寬頻帶的信號來傳送信息呢 ? 簡單的回答就是主要為了通信的安全可靠。例如很窄的脈沖信號，其頻譜則很寬。 研究擴(kuò)頻通信的目的和意義 擴(kuò)頻通信是通信的一個重要分支和信道通信系統(tǒng)的發(fā)展方向。 At the same time, different users use different code, others can not be tapping their munications, thus spreadspectrum system with high confidentiality. 4 Spread Spectrum Communication in the MATLAB simulation Direct Sequence Spread Spectrum system BER simulation According to Shannon theorem, we can see: ）（ NSWLC /1og ?? （ 7） Where: W for the transmission bandwidth。 the receiving end is using the same modem code and related processing, the restoration of the original spectrum munication system has three main characteristics. Carrier is an unpredictable, or socalled pseudorandom broadband signal. Carrier data bandwidth than the modulation bandwidth is much wider. Receiving process is generated by local broadband carrier signal and receiving a copy of the signal to the broadband signal to achieve. The main way of spread spectrum are as follows:Direct Sequence Spread Spectrum (DSSS) using highspeed pseudorandom code on to the lowspeed data transmission spread spectrum modulation。 1) information and data, Repeat for each information CL Times, CL Correspond to the information contained in each of the pseudocode chip number, a random number generator PN Sequence )(nc Multiplied,And then superimposed on the sequence of variance for 2/02 N?? Gaussian white noise and the form of nAni 0sin)( ?? Sinusoidal interference signal, which ?? ?? 00 and CLA? .In the demodulator, PN sequence with interrelated operations Information and will form the sum of d and will form the sum of CL output will be sent to decision, and on the signal and threshold 0 to determine the data transmission +1 or 1, Figure 2 in the counter39。這一定義包含了以下三方面的意思： 1）信號的頻譜被展寬了。這種很窄的脈沖碼序列，其碼速率是很高的，稱為擴(kuò)頻碼序列。擴(kuò)頻通信的可行性，是從信息論和抗干擾理論的基本公式中引伸而來的。 3 擴(kuò)頻通信系統(tǒng)的特點(diǎn) 擴(kuò)頻信號是不可預(yù)測的偽隨機(jī)的寬帶信號 ,其帶寬遠(yuǎn)大于欲傳輸數(shù)據(jù) (信息 ) 帶寬 ,同時 ,接收機(jī)中必須有與寬帶載波同步的副本。 E 為信號能量 ?？倢?27樓 ； 30樓 m。 本工程由寧夏燕寶房地產(chǎn)開發(fā)有限公司開發(fā)，銀川市規(guī)劃建筑設(shè)計院設(shè)計。 保密性好 在一定的發(fā)射功率下 ,由于擴(kuò)頻信號分布在很寬的頻帶內(nèi) ,無 線信道中有用信號功率譜密度極低 ,這樣信號可以在強(qiáng)噪聲背景下 ,甚至是有用信號被噪聲淹沒的情況下進(jìn)行可靠通信 ,使外界很難截獲傳送的信息 ,想進(jìn)一步檢測出信號的特征參數(shù)就更難了。因此，處理增益 G反映了擴(kuò)頻通信系統(tǒng)信噪比改善的程度。 14 擴(kuò)頻通信的理論基礎(chǔ) 長期以來，人們總是想法使信號所占領(lǐng)譜盡量的窄，以充分利用十分寶貴的頻譜資源。 我們知道，在時間上有限的信號，其頻譜是無限的。正是因?yàn)閿U(kuò)頻系統(tǒng)本身具有的特征使其性能具有一系列的優(yōu)勢。 As the spread spectrum munication system in the transmission signal bandwidth expansion, so even if the signal to noise ratio is very low, even lower than the useful signal power of interference signal power is still the case to highquality uninterrupted munication, the expansion of the spectrum The more width, the stronger the antiinterference. LPI of Spread spectrum signal is equivalent to the power being distributed evenly over a wide frequency band, so that transmission signals are very low power density, so that it is difficult to monitor to detect the , the spread spectrum munication system has a low probability of interception. Antiinterference performance of multipath Multipath interference is due to radio propagation encountered in the course of a variety of nonexpected reflector (such as the ionosphere, the mountains, buildings, etc.) caused by reflection or or scattering of these signals with the direct path signal interference in the receiver interfere with each interference in radar and munication are severely the spread spectrum munication system in an increase of spreadspectrum modulation and despread process,This spreadspectrum sequences using the correlation between the characteristics of,Despreading at the receiving end when the relevant technology from multipath signals to isolate the most useful signals, or multipath signals of the same code sequence signal superposition, so that you can effectively eliminate the wireless munications in multipath interference caused by signals decline and, therefore, 8 spread spectrum munication system has good properties of antimultipath fading. Good Privacy Transmitting power in certain circumstances, due to the distribution of spreadspectrum signals over a wide frequency band, Useful signal channel power spectral density is extremely low, so the signal can be in strong background noise, or even a useful signal to be the case of noise drowned reliable munications,Intercepted by the outside world it is very difficult to send the information, would like to detect the characteristic parameters of the signal even , the spread spectrum munication system can be concealed。Frequencyhopping system using pseudorandom code to control the carrier frequency in a wider band of the change。s decision to record the number of wrongful convictions . Analysis of simulation results Adding noise and interference, the access CL = 10 ,With three different sinusoidal signal interference, the amplitude of 2, 3, 7. In bit error rate in puting the variance of additive noise is fixed, a total of 10,000 calculations, and each operator, the signal energy values are required to meet the requirements of the signal to noise ratio, which has been shown in Figure 3 the simulation be seen that the amplitude of the sinusoidal interference signal the greater the greater the error rate. Similarly, in the same signal to noise ratio, the greater the processing gain, the smaller the error rate, and in large signal to noise ratio, this difference is particularly evident. Figure 3 MonteCarlo simulation of the spread spectrum munic