| Abstrakt: |
The Considered incoherent demodulators of signals, which are invariant, that is, completely insensitive to the initial phase of the signal. It is shown that with absolute phase modulation, signal reception is possible only with a precisely known initial phase, which extremely limits the scope of practical use of absolute phase modulation. With phase-difference modulation of PDM-1, it becomes possible to receive phase-modulated signals with an undefined initial phase. With PDM-2, the possibility of receiving phase-modulated signals with an undefined carrier oscillation frequency is added to this. It is noted that signals from PDM-2, as well as signals from PDM-1, can be received using algorithms of coherent, optimal incoherent and autocorrelation reception. In the case of coherent and optimal incoherent methods, the property of invariance to frequency is not realized, since these reception methods reach their potential only with a precisely known frequency of the carrier oscillation, and when the frequency of the signal deviates from the frequency of the reference oscillations, the demodulators quickly lose their performance. When studying signals with phase-difference modulation and methods of receiving these signals, we are not talking about the positionality of the system (not about the multiplicity of modulation), determined by the number of discrete values or the signal of its information parameter in the communication channel, but about the order of phase differences, which are used as an information parameter. The article introduces the concept of the order of signal phase difference. It is shown that the transition to PDM-2 makes it possible to achieve complete insensitivity not only to an arbitrary initial phase, but also to arbitrary frequency shifts. The principles of construction of multi-position phase-modulated signals and signals with combined modulation methods are considered. General algorithms for the formation and processing of signals with phase-difference modulation with corresponding structural schemes have been developed. [ABSTRACT FROM AUTHOR] |
