dsss 中文意思是什麼

Counteraction technology for correlative intermodulation products based on soft iimited transparent transponder in dsss

系統中用於軟限幅轉發器的相關互調分量抵消技術

The nonlinear filtering for nbi estimate - subtract assumes that the prediction error is dominated by spread spectrum signal and the background noise power is far below spread spectrum chip power, this assumption promises the low error ratio of chip decision but may not be attainable to digitalized dsss receiver in military communication environment, and does not coincide with the principle of dsss communication that decreases bit error ratio ( ber ) depending on spread spectrum gain, not on chip power

在干擾估計抵消濾波中，以往的非線性濾波要求干擾抵消濾波后擴頻信號功率遠大於殘余噪聲功率，進而假設碼片判決的誤碼片率基本為零，這一要求對軍用擴頻通信是不利的，而且也不符合擴頻通信利用擴頻增益降低誤碼率的原則。

This paper focuses on the blind code synchronization approach and spreading sequences estimation algorithm. the main results can be summarized as follows : 1. both synchronous and asynchronous dsss / bpsk baseband signal models are established

本文重點是對盲碼同步和擴頻碼序列估計的研究，主要的工作成果如下: 1 、分同步和非同步兩種情況建立了dsss / bpsk基帶信號模型，並介紹了二種非合作式擴頻碼序列估計和解擴的方案。

At last the algorithm of ddmf is achieved by the investigation tool of altera company ? quartus ii and the vhdl language, and its ip core is also achieved which is used not only in the satellite navigation position system, but also in the long pn code dsss system. ddmf investigated in the dissertation gives a good way to design the rapid pn code acquisition in the beidou project, and the technology has the definite theory and practice significance

此外還應用altera公司的最新的fpga開發工具quartusiiv5 . 1 ，採用了國際標準的硬體描述語言? vhdl語言，對數字差動匹配濾波器和傳統匹配濾波器演算法予以實現，開發了該演算法的軟ip核，可以對所應用的擴頻碼長度， a / d采樣后的數據量化階數，所用擴頻碼等可進行隨意改寫。

After establishing the model of intermediate frequency direct sequence spreading spectrum ( if dsss ) receiver, comparing and analyzing several conventional code acquisition methods, code and carrier two - dimension fast acquisition scheme based on two - dimension fft is proposed. finally, the situation for two targets is analyzed

首先在建立了中頻直擴接收機的模型之後，本文對常用的偽碼捕獲方法進行了詳細地分析和比較，然後提出了本文的基於二維傅立葉變換技術的快速捕獲方法，並且分析了兩個目標時的情況。

They are increasingly replacing conventional communication forms and obtaining extensively applications in modern military and commercial communication systems, for example, cdma communication system, gps, measuring and control system, satellite chain, identification of friend or foe and etc. therefore, corresponding dsss electronic counter technique becomes a big problem to solve in electronic warfare domain

正日益取代常規通信而廣泛應用於現代軍事和商用通信系統中，如碼分多址（ cdma ）通信、全球定位系統（ gps ） 、測控、衛星鏈路和敵我識別等。因此，與之對應的直擴通信對抗技術也就成了通信對抗領域亟待解決的問題。

A method of dsss signal detection based on stft and 3rd order cumulant

和三階累積量的直擴信號檢測法

The mechanism of the dsss to the users is like a black box and the users cannot distinguish the correctness of the results. the main reason is the insufficiency of users " interruption in the computer ' s operation and the blur mechanism of the ddss

整個過程對于用戶來說，計算過程是由計算機后臺程序進行黑箱操作的，用戶在運算過程中缺少必要的參與手段，也就是說透明交互性能不強，導致決策支持的效果不甚理想。

In order to meet the needs of dsss signal reconnaissance, a method of dispreading without the code is brought forward by this paper ， in which the local code is gained from the dsss signal. so we can intercept dsss signal with low snr even if the spreading code is unknown. liu jie ( communication and information system ) directed by prof. gao huisheng

為適應電子戰中對直擴信號偵察的需要，本文提出一種了無碼解擴的方案，採用從直擴信號中獲得本地參考信號的方法，可以在沒有擴頻碼的情況下，截獲低信噪比直擴信號的通信信息。

After achieving the synchronization of the pn code and carrier, despreading and demodulating the received dsss signal can be executed with the local synchronized code and carrier. so, lots of energy and fund has been expended on it

直接序列擴頻系統只有在完成了偽碼同步和載波同步之後，才可能用同步的本地偽碼和本地載波對接收的擴頻信號進行解擴、解調。

This paper mainly focuses on the noise limiting by means of the direct sequence spread spectrum ( dsss ) and the analysis of the transmission performance of the plc and some digital modulation technology. the contents of the paper is as follows : 1 ) the technical feasibility is proved after simulating noise limiting principle of dsss by means of systemview, the simulation software ; 2 ) a kind of band pass filter ( bpf ) is realized according to the requirement of filter and the principle of butterworth approximation, which satisfies the index of performance of dsss. 3 ) the low voltage plc system includes the sc1128, the specific modulation / demodulation ic, the bpf filter and other circuit components, furthermore, the control function of system is realized by means of the personal computer and the microcontroller

本課題在對低壓電力線的傳輸特性和數字調制技術進行分析的基礎上，將通信理論中的直接序列擴頻技術（ dsss ）用於解決低壓電力線通信的干擾問題，主要研究內容如下： （ 1 ）用通信模擬軟體systemview對dsss技術的通信和抗干擾原理進行模擬分析，分別對時域和頻域下採用dsss技術前後接收信號的頻譜進行分析，驗證dsss技術在本系統中的可行性； （ 2 ）由dsss技術對濾波系統的要求，根據濾波理論分析了巴特沃思型濾波器的逼近原理並設計了合適的濾波電路； （ 3 ）用調制解調晶元sc1128和自行設計的濾波器加之輔助外圍電路，構造出低壓電力線載波通信系統，並採用atmel公司的單片機設計了接收和發射電路的微控制器； （ 4 ）分別對採取抗干擾措施前後輸入和輸出信號進行對比實驗，並對結果進行分析，驗證了dsss技術對干擾信號的抑制作用。

4. analyzed two types of spread spectrum ( dsss and fhss ) approved by the fcc based on the characteristic of phy layer ; then analyzed the characteristic and technology of the cck modulation and at last put forward an improved cck scheme that will increase the data rate of wlan to 16. 5mbps

針對物理層的特點，討論了無線局域網的兩種擴頻技術? ? dsss和fhss ，分析比較了兩者的性能特點和適用的范圍，並探討了一種支持高數據數率的cck調制方式以及使速率能達到16 . 5mbps的cck改進方案； 5

Appropriate data compression methods are needed to assure the random nature of the information source and to enlarge its entropy. in this thesis, first, we present the theory of sess system, then the acquisition method of sess system is discussed in detail, finally, a acquisition model of sess system is built and simulated in the awgn channel, in the raleigh fading channel and in multi - address interfere condition. the simulation results show the acquisition method of sess system can be just as reliable as the conventional dsss systems

本文首先對自編碼擴頻通信的基本原理，自編碼擴頻序列的產生方法及其產生的序列的特性進行了概述，然後詳細討論了直擴通信系統中的擴頻碼的捕獲跟蹤問題，根據自編碼擴頻通信的特點，設計了其捕獲跟蹤方案，並在加性高斯白噪聲通道、瑞利衰落通道和多址干擾情況下進行了模擬。

By making use of the characteristics of pseudorandom spread spectrum sequence in time - domain, this thesis has studied the time - domain correlation detection method of the dsss / bpsk signal and proposed the time - domain difference - accumulation detection method of the dsss / bpsk signal

利用擴頻偽隨機序列在時域上的特點，本文研究了dsss / bpsk信號的時域相關檢測方法，並提出了dsss / bpsk信號的時域累差檢測方法。

Based on chaos critical state detection method, two approaches are used : one is that making a pretreatment on dsss signal to take out the period information of the signal. the other is that starting from the analysis of the sensitivity of duffing system to ambi - polar square wave modulated by sine signal, the

通過兩種途徑:對信號進行預處理，提取出其中的周期信息，轉化為單頻信號檢測;從研究duffing振子對方波調制信號的敏感性出發，全面分析其中的間歇混沌現象，實現信噪比- 20db以下dsss信號的檢測。

The results of the testing prove that the system compare with dsss takes great advantages over others on the aspects of the rate of transmitting data, its stabilization and its possibility of expanding

測試結果表明，與直序擴頻系統相比， ofdm系統在數據傳輸速率、穩定性和可擴展性等方面具有十分明顯的優勢。

For dsss signals, we proposed two algorithms, one is a hypothesis test algorithm that can be used to detect if there are dsss signals, the other is a symbol period estimation algorithm using the cycle - stationary feature of dsss signals

對直序擴頻（ dsss ）信號，本文提出了一種假設檢驗演算法檢測其存在性；利用dsss信號的循環平穩特性，提出了估計dsss信號符號周期的方法。

We analyzed the anti - jam and band inside anti - interfere performance of the system, and the low probability intercept ( lpi ) of the traditional direct sequence spread spectrum ( dsss ) modulations in the uav platform ' s applications. so a new modulation technique using a multi - level pseudo noise ( pn ) code has been presented. the new multi - level pn code is built from a high speed pn code through a low passed filter ( lpf )

分析了系統抗阻塞式干擾和抗帶內頻帶干擾的性能，以及常規bpsk qpsk - dsss調制在無人機通信中存在的安全隱患，提出了一種用多電平pn碼進行擴頻調制的方法：採用高速pn碼，經過低通濾波器，產生多電平pn碼進行直序擴頻調制，能在低信噪比情況下有效抵抗平方率檢測器對系統載波的檢測。

At the end of this paper the dsss system is compared with two different systems to emphasize its perfect performance

應用systemview模擬工具對系統進行了性能模擬，分析了系統的誤比特率。

It is an urgency to investigate a new dsss to achieve lower low probability of detection ( lpd ) and higher anti - jamming performance

為達到更低截獲率和更高抗干擾的通信目的，必須研究新的直擴通信技術。