HF Adaptive Frequency Hopping Communication Systems

In this paper it is introduced that the basic theory of software radio and shortwave radio IF digital application, in the foundation of that and with the typical chip that is on the core of software radio digital frequency conversion techniques are discussed, update the original analog communication system on application of new technologies, new methods, in the paper it is given a short-wave radio IF digital design program, by using HF SSB modulation the program for the test, the results show that the new shortwave adaptive frequency hopping communication systems have substantially improved in terms of performance indicators.FH is the most commonly used form of spread spectrum. Transceivers its work both sides of the transmission signal carrier frequency in accordance with predetermined rules for discrete changes in the means of communication, that is to say, carrier frequency is used by the pseudo-random code control and random hopping in communication. From ICT implementation,"Frequency Hopping" is a code sequence using more frequently shift keying means of communication, as well as a code-controlled carrier FH communication systems. In the time domain, FH signal is a multi-frequency FSK signal; In the frequency domain, FH signal in the spectrum is a very wide band on a random intervals ranging from the hopping.In the design the adaptive frequency hopping system is on the basis of the conventional adaptive frequency hopping system. Removal of real-time fixed or semi-fixed interference, thereby automatically choose good adaptive channel set to communicate, it keeps communication system to maintain good state in communication. In other words, it will not only achieve the function of conventional frequency hopping system, but also achieve the function of real-time adaptive frequency and power control.Compared the communication of determining frequency, the FH communication becomes covert and hardly to be intercepted. Meanwhile, frequency-hopping communication also has good anti-jamming capability, even if the partly of crossover interference, it could communicate normally on the other frequency that is not interference. Since FH communication system is instantaneous narrowband system, it easily compatible with other narrowband communication systems, hopping radio links with the conventional narrowband radio and easily to update equipment. With the rapid development of technology of microelectronics and digital signal processing, the frequency synthesizer and hopping synchronization problem has been solved. And adaptive technology further enhances the integration of the frequency hopping system performance. FH innovative method has been applied continuously, And FH technology develops in a new area for the application of software radio.Currently the single carrier shortwave communication transmission rate has reached 9,600 bps, it is strictly demands with equilibrium, and it is hard to further enhance the transmission speed, a new developing generation modem of parallel system uses OFDM technology. Through adding the layout of protection, frequency-selective fading channel can be transformed as smooth fading channel. It has strong capacity of anti-ISI to reduce the complexity of equilibrium.