Abstract:
Spread-spectrum techniques are methods by which a signal (e.g. an electrical, electromagnetic, or acoustic signal ) generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, to prevent detection, and to limit power flux density (e.g. in satellite downlinks).
History Frequency hopping:
The concept of frequency hopping was first alluded to in the 1903 U.S. Patent 723,188 and U.S. Patent 725,605 filed by Nikola Tesla in July 1900. Tesla came up with the idea after demonstrating the world's first radio-controlled submersible boat in 1898, when it became apparent the wireless signals controlling the boat needed to be secure from "being disturbed, intercepted, or interfered with in any way." His patents covered two fundamentally different techniques for achieving immunity to interference, both of which functioned by altering the carrier frequency or other exclusive characteristic. The first had a transmitter that worked simultaneously at two or more separate frequencies and a receiver in which each of the individual transmitted frequencies had to be tuned in, in order for the control circuitry to respond. The second technique used a variable-frequency transmitter controlled by an encoding wheel that altered the transmitted frequency in a predetermined manner. These patents describe the basic principles of frequency hopping and frequency-division multiplexing, and also the electronic AND-gate logic circuit.
摘 要
擴(kuò)頻技術(shù)是信號（例如一個電氣、電磁，或聲信號）生成的特定帶寬頻率域中特意傳播，從而導(dǎo)致更大帶寬的信號的方法。這些技術(shù)用于各種原因包括增加抗自然干擾和干擾，以防止檢測，并限制功率流密度（如在衛(wèi)星下行鏈路）的安全通信設(shè)立的。
頻率跳變的歷史：
跳頻的概念最早是歸檔在1903年美國專利723188和美國專利725605由尼古拉特斯拉在1900年7月提出的。特斯拉想出了這個想法后，在1898年時展示了世界上第一個無線電遙控潛水船，卻從“受到干擾，攔截，或者以任何方式干涉”發(fā)現(xiàn)無線信號控制船是安全的需要。他的專利涉及兩個實現(xiàn)抗干擾能力根本不同的技術(shù)，實現(xiàn)這兩個功能通過改變載波頻率或其他專用特征的干擾免疫。第一次在為使控制電路發(fā)射機(jī)的工作，同時在兩個或多個獨(dú)立的頻率和一個接收器，其中的每一個人發(fā)送頻率調(diào)整，必須在作出回應(yīng)。第二個技術(shù)使用由預(yù)定的方式更改傳輸?shù)念l率的一個編碼輪控制的變頻發(fā)送器。這些專利描述頻率跳變和頻分多路復(fù)用，以及電子與門邏輯電路的基本原則。