| 摘要 |
The invention relates to a method and a device for rendering the information transmissions secret, said method and device being compatible to the existing systems and ensuring a very good protection against decoding. The method for rendering the information transmissions secret consists in rearranging the spectrum sequentially, in the same range, according to a quasi-random law, with three degrees of freedom. The method requires two channels, one for transmitting the information-carrying signal with redistributed signal and one for the synchronizing signal which may be common to many information transmitting channels. The rearrangement of the spectrum is made by sampling, multiplying with a +1/-1 quasi-random binary sequence, and by filtering. The degrees of freedom are obtained by choosing the sampling frequency of the code of the quasi-random sequence and of the synchronization delay. The device for rendering the information transmissions secret has a simple construction, being made up of a reciprocal circuit for rearranging the spectrum, which encodes and decodes the information-carrying signals, said circuit consisting of a unit of controlled sampling-multiplying (1), a low-pass filter (2) and a sampling-multiplying control unit (3) working synchronously, according to an external synchronizing signal processed in a synchronization circuit (4), depending on the commands received from a panel of selecting the synchronization parameters (5) wherefrom there may be selected the synchronization parameters and the sampling frequency, the multiplication code and the synchronization delay, respectively. The synchronization may also be done starting from the voltage phase in the power supply network. The constructive performance of the device requires a simple conventional technology.
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