MSK modulation and differentially coherent detection transmission system
First Claim
1. A minimum shift key (MSK) continuous phase modulation transmission system comprising differentially coherent type MSK transmitting equipment and differentially coherent type MSK receiving equipment which are connected through a transmission medium,said transmitting equipment comprising means for encoding a message having an ordered string of K symbols successively derived with a predetermined periodicity, T, into an ordered coded string of K differentially coded symbols, where K is an integer greater than one, the encoder deriving an MSK continuous phase signal modulated by a waveform having a string of impulses carrying said ordered coded string,said receiving equipment including:
- filter means matched with the waveform of the impulses of said impulse string, and means cascaded with said filter means for suppressing intersymbol interference inherent to said MSK type continuous phase signal from samples of a string of received impulses.
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Abstract
An embodiment of the transmission system comprises an MSK linear-modular transmitter and an MSK differentially coherent receiver connected by a transmission medium 3. A system embodying the invention is essentially characterized by filters in the receiver including analog or digital equalizers and by a differential encoding carried out on symbols of a message to be transmitted by a differential encoder included in the transmitter. The function of the equalizer is to eliminate intersymbol inteference in received signals. The differential encoding carried out is such that a coded symbol of rank k issued by the encoder depends on the corresponding symbol of the message and on the coded symbol of rank k-M, whereby M is an odd integer preferably greater than 1. On reception the probability of decision error with regard to a received symbol is all the lower that the integer M is high. The value M=3 is an appropriate value.
42 Citations
32 Claims
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1. A minimum shift key (MSK) continuous phase modulation transmission system comprising differentially coherent type MSK transmitting equipment and differentially coherent type MSK receiving equipment which are connected through a transmission medium,
said transmitting equipment comprising means for encoding a message having an ordered string of K symbols successively derived with a predetermined periodicity, T, into an ordered coded string of K differentially coded symbols, where K is an integer greater than one, the encoder deriving an MSK continuous phase signal modulated by a waveform having a string of impulses carrying said ordered coded string, said receiving equipment including: - filter means matched with the waveform of the impulses of said impulse string, and means cascaded with said filter means for suppressing intersymbol interference inherent to said MSK type continuous phase signal from samples of a string of received impulses.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An MSK type continuous phase modulation transmission system comprising differentially coherent type transmitting equipment and differentially coherent type receiving equipment which are connected through a transmission medium, wherein said transmitting equipment is of the linear modulator type and comprises means for encoding an incoming message including an ordered string of K symbols successively derived at a predetermined period into an ordered coded string of K differentially coded symbols, where K is any integer greater than one, said encoding means deriving an MSK type continuous phase signal modulated by a string of impulses carrying said ordered coded string, said encoding means carrying out a differential coding function such that any coded symbol of rank k in said coded string depends on the product of the coded symbol of rank k-M and the symbol of rank k in said incoming message, where M is a predetermined odd integer greater than 1,
said differentially coherent type receiving equipment comprising a filter matched with the waveform of the impulses of said impulse string, and means cascaded with said filter for suppressing intersymbol interference inherent to said MSK type continuous phase signal from samples of a string of received impulses.
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17. An MSK type continuous phase modulation transmission system comprising differentially coherent type transmitting equipment and receiving equipment which are connected through a transmission medium, wherein
said transmitting equipment comprises means for encoding a message having an ordered string of K symbols successively derived at a predetermined period into an ordered coded string of K differentially coded symbols and for deriving an MSK continuous phase signal modulated by a string of impulses carrying said ordered coded string, where K is any integer greater than one, said receiving equipment comprising: - filter means matched with the waveform of the impulses of said impulse string, and means cascaded with said filter means for suppressing intersymbol interference inherent to MSK type continuous phase signals, and thereby deriving first and second signals comprising said received impulse string,
wherein said receiving equipment further comprises means for deciding with a minimal probability of error the value of a kth symbol in said message according to first and second values of said first and second signals including said received impulse string respectively at first and second sampling instants, said first and second sampling instants being of ranks k-M and k respectively corresponding to the transmission by said transmitting equipment of said k-Mth and kth coded symbols, where M is an odd integer greater than 1, said first values of said first and second signals at the first sampling instant of rank k-M respectively representing first and second components of a k-Mth received coded symbol corresponding to the k-Mth symbol of said message, said second values of said first and second signals at said second sampling instant of rank k respectively representing first and second components of a kth received coded symbol corresponding to the kth symbol of said message. - View Dependent Claims (18)
- filter means matched with the waveform of the impulses of said impulse string, and means cascaded with said filter means for suppressing intersymbol interference inherent to MSK type continuous phase signals, and thereby deriving first and second signals comprising said received impulse string,
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19. Receiving equipment in an MSK transmission system wherein an encoder at a transmitter derives a message having an ordered string of K symbols successively derived at a predetermined period T into an ordered coded string of K differentially coded symbols and for deriving an MSK continuous phase signal modulated by a string of impulses carrying said ordered coded string, where K is any integer greater than one,
said receiving equipment comprising a filter means matched with the waveform of the impulses of said impulse string, and means cascaded with said filter means for suppressing intersymbol interference inherent to said MSK type continuous phase signals, and thereby deriving first and second signals comprising said received impulse string, wherein said receiving equipment further comprises means for deciding with a minimal probability of error the value of a kth symbol in said message according to first and second values of said first and second signals including said received impulse string respectively at first and second sampling instants, said first and second sampling instants being of ranks k-M and k respectively corresponding to the transmission by said transmitting equipment of said k-Mth and kth coded symbols, where M is an odd integer greater than 1, said first values of said first and second signals at the first sampling instant of rank k-M respectively representing first and second components of a k-Mth received coded symbol corresponding to the k-Mth symbol of said message, said second values of said first and second signals at said second sampling instant of rank k respectively representing first and second components of a kth received coded symbol corresponding to the kth symbol of said message.
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21. Receiving equipment in an MSK transmission system wherein an encoder at a transmitter derives a message having an ordered string of K symbols successively derived with a predetermined periodicity, T, into an ordered coded string of K differentially coded symbols, where K is an integer greater than one, the encoder deriving an MSK continuous phase signal modulated by a waveform having a string of impulses carrying said ordered coded string, said receiving equipment comprising filter means matched with the waveform of the impulses of said impulse string, and means cascaded with said filter means for suppressing intersymbol interference inherent to said MSK type continuous phase signal from samples of a string of received impulses, the signal received by the receiving equipment having a frequency f0 and the means for suppressing includes means for deriving a first signal proportional to the product of the received signal and the received signal delayed by the linear combination of MT and one quarter of a cycle at f0, where f0 MT and M have integral values so sin 2π
- f0 MT=0 and cos 2π
f0 MT=1, and means for periodically sampling the first signal at times spaced from each other by T. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
- f0 MT=0 and cos 2π
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32. Differentially coherent receiving equipment in an MSK transmission system wherein an encoder at a transmitter derives a message having an ordered string of K symbols successively derived with a predetermined periodicity, T, into an ordered coded string of K differentially coded symbols, where K is an integer greater than one, the encoder deriving an MSK continuous phase signal modulated by a waveform having a string of impulses carrying said ordered coded string, said receiving equipment comprising differentially coherent filter means matched with the waveform of the impulses of said impulse string, and means cascaded with said filter means for suppressing intersymbol interference inherent to said MSK type continuous phase signal from samples of a string of received impulses.
Specification