哈尔滨理工大学远东学院学士学位论文 modulation [x (t)] and other non-modulation signal. These signals by the receiver, respectively, to find out (a signal frequency may be different from another) is the interaction between the input detector, this detector can get back to the data modulation. Spread spectrum transmission system of reference (TR-SS) of the broadband carrier is truly a random amount of broadband noise sources, through the transmitters, receivers, until the communication generated by the application of that moment, was unknown.
Stored reference generator system needs an independent device, transmitter and receiver in the pseudo-random broadband waveforms, these waveforms is identical to the basic characteristics of the [chart 1.2 (b)]. Off the automatic adjustment of the spread spectrum receiver waveform generator output can be maintained and will soon appear fully synchronized spread-spectrum waveform. Data detected by the orthogonal completion of the interaction. Waveform generator for the installation of the first occurrence of the specific parameters of the rules of the system, resulting in negative interference with the use of the state's interference waveform strategy (even if the interference source has decided to interfere with the successful completion of the structure).
A matched filter system bandwidth, the bandwidth of the signal passing through a long-term, broadband, and the charged pseudo-random function corresponding pulse generated by the filter impulse [Chart 1.2 (c)]. Signal detection receiver using the same pseudo-random mechanism of the match with the cycle of control-type filter, it is to be completed by each operator. Matched filter system and the SR system is the difference between the main difference lies in different ways, testing the process of being built mechanical components, the external filter system, therefore the nature of the detection system similar to SR.
Of course, pure TR system has some fundamental shortcomings, including: (1) system easily deceived, because interference from the principle source of transmission, said a group of receivers to receive the waveform. (2) of the
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哈尔滨理工大学远东学院学士学位论文 operation is relatively poor at low signal levels because of the noise and interference appear in the orthogonal signal receiver. (3) nearly as long as any to listen to those who can easily transfer the data signal. (4) TR two-channel system and the need for additional bandwidth is not easy to match. TR system is associated with some of the issues, through the arbitrary conversion of a communication link in which the parameters can be relaxed (for example: SR using similar technology to protect one of the broadband link).
SR system for spread spectrum waveform generator, and the application of the following general form of modulation of the device has been established, an SS waveform generator output was given the name of the common c (t), and is the base-band SS waveform description (which may the complexity of the assessment).
Recorded modulation: waveform W (t) in the Tp phase duration were recorded and, if necessary, given the form of the cycle are as follows:
c(t)???(t?nT) (1.19)
pnThe function of this signal is restricted, to limit the production of self-allocated to the transmitter and the receiver records the total, as well as the waveform is not required for re-use.
Frequency Hopping (FH): the assumption that p (t) is the duration of the basic pulse Th above the state (often referred to as hopping time), frequency-hopping modulation of the formula is as follows:
c(t)??exp?j(2?fnnt??n)?p(t?nTh)
(1.20)
Most likely, the complex baseband signal c (t) has never been natural now located on the transmitter and receiver. On the contrary, have a frequency shift of the pseudo-random sequence (fn) synthesizer-driven, resulting in true value of the IF or RF carrier modulation version of c (t), in a sequence of arbitrary phase modulation-type (Φn) by-product of the process.
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哈尔滨理工大学远东学院学士学位论文 When jumping (TH): the assumption that pulse shape p (t) reached the longest continuous cycle of TS / MT, the representation of the frequency-hopping waveform as follows:
c(t)??n??anp?i??n???MT????TS?????? (1.21)
Drawn from the above example, the time Ts seconds is divided into intervals containing an independent pulse, the pulse interval time period in the pseudo-random position to put MT.
Direct sequence spread spectrum modulation: spread spectrum waveform designers said:
c(t)??cnnp(t?nTc)
(1.22)
For direct-sequence modulation. Pseudo-random number generator, the output sequence [cn] have come up with a linear modulation pulse sequence, each pulse has a continuous cycle known as the jump time Tc.
Mixed Modulation: The above listed both the advantages of each technology, there are drawbacks, depending on the purpose of system design (AJ is designed to protect only one side of the problem). Possibility is that mixed use of modulation techniques will show the effect of better jobs. For example: Select
c(t)??ci(i)(t) (1.23)
Will win the independent bandwidth waveform c (i) (t) the advantages and disadvantages of their respective ease.
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哈尔滨理工大学远东学院学士学位论文 附录B
扩频系统的构造与配置
纯扩频策略，是任何时刻仅应用单一线路，机械化后比潜在多样因素K的系统更有工作效率，这可在图表1.1中得出。对于扩频系统，图表1.1中的K型传输接收机组合，被单一宽频带的链接代替，这种链接具有综合和检查所有由正交通信系统复合结构产生的波形特征的功能。在纯扩频策略中，随机选取的便于通信的链接被等价的近似所代替，即选择D尺寸附属空间，达到从2TSWSS尺寸信号空间的合成波形的目的，每次传输信号时，随机选择过程必须可以独立重复，为了避免通信链接的威胁，独立选取是必要的。从而干扰源可以预测要使用的信号装置，可以限制某种干扰能量到某个装置上，因而可以减少表面的多样性和能量增益，从而形成单一性。
图表1.2显示了三种系统构造，它阐明设计者可能使用的基本技术，能确保发射机和接收机与类似的随机信号设备相同步。负责维持传导过程中不可测的性质的扩频系统那部分在图表1.2中双倍圈画，这些系统的具体运算方式如下：
1. 传输扩频系统完成扩频工作，通过传输两种不同的带宽，不可预测的载波，一个数据调制[x(t)]和其他未调制的信号。这些信号，由接收机分别重新找出（一种信号也许在频率上不同于另一种）是相互作用的检测器的输入量，这种检测器可恢复数据调制。传输参考扩频系统（TR-SS）中的宽带载波是真正的随机量，宽带噪声来源，通过发射机、接收机，直到通信应用中产生的那一瞬间，才被知晓。
2. 储存参考系统需要独立的发生器装置，它在发射机和接收机的伪随机宽带波形上，这些波形的基本特征是完全相同的[图表1.2(b)]。自动调节过的接收机的扩频波形发生器可保持输出量与即将出现扩频波形完全同步。数据检测是由正交的相互作用完成的。波形发生器最初用于安装特定参数到发生规则系统内，由此否定处于使用状态的波形干扰器的干扰策略（即使干扰源已成功地完成决定干扰器的结构）。
3. 匹配滤波器系统产生一种带宽，这个带宽传递的信号是通过带有长期的、宽带的、伪随机的被控脉冲相应功能的滤波器冲激产生的[图表1.2(c)]。接收机的信号检测运用完全相同的伪随机机制，同周期控制的匹配式的滤波器,它可完成相互运算。匹配式滤波器系统与SR系统有区别，区别主要在于方式不同，内置部件检测过程被机械化，因此滤波系统外在的检测性质与SR系统近似。
当然，纯TR系统有某些基本缺点，其中：（1）系统易被骗，因为从
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哈尔滨理工大学远东学院学士学位论文 原理上说干扰源传输一组接收机可接收的波形。（2）相对地劣性操作在低信号等级上出现，原因是噪音和干扰都出现在接收机的正交信号上。（3）任何收听者只要接近传输信号很容易得到数据。（4）TR系统的两个通道需要额外带宽而且不容易匹配。与TR系统相关联的某些问题，通过随意转换其中一个通信链路的参数可得到缓和（例如：用类似SR技术保护其中一种宽带链接）。
用于SR系统的扩频波形发生器，并且应用下列普通调制形态的装置已被建立，一个SS波形发生器的输出被给予共通的名称c(t)，并且是SS波形的基带描述（可能的复杂评估）。
1. 记载调制：波形W(t)在持续时间Tp阶段被记录，如有需要，给出周期形式如下：
c(t)???(t?nTp) (1.19)
n这种信号的功能受到限制，限制产生自分配给发送机和接收机的记录总量，以至波形的重新利用是不需要的。
2. 跳频（FH）：假设p(t)是持续时间段Th的基本脉冲状态（通常称为跳变时间），跳频调制的公式如下：
c(t)??exp?j(2?fnt??n)?p(t?nTh)
n(1.20)
十之八九，复杂的基带信号c(t)从未自然地处现在发射机和接收机上。相反地，产生的伪随机频移序列{fn}驱使频率合成器，产生真值IF或RF的载波调制版本c(t)，处于任意相位的序列{Φn}式调制过程的副产品。
3. 时跳（TH）：假设脉冲波形p(t)的最长持续周期达到TS/MT，代表性的跳频波形为：
c(t)??n??anp?i??n???MT????TS??????
(1.21)
从上例得出，时间被分为Ts秒间隔内包含一种独立脉冲，此脉冲在间隔时间段内伪随机地置于MT位置。
4. 直接扩频序列调制：扩展频谱设计师们称波形：
c(t)??cnp(t?nTc) (1.22)
n为直接序列调制。伪随机数字发生器的输出序列[cn]线性调制得出一种脉冲序列，每种脉冲具有的持续周期Tc称为跳跃时间。
5. 混合式调制：以上列举的每种技术既有优点，也有缺点，取决于系统设计的目的（AJ保护仅是设计问题的一个方面）。可能的是，混合使用调制技术会表现出更好的工作效果。例如：选择
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哈尔滨理工大学远东学院学士学位论文 c(t)??ci(i)(t) (1.23)
会赢得独立带宽波形c(i)(t)的优势，并且缓和它们各自的劣势。
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