PSK modem system with improved demodulation reliability
First Claim
1. A modem system for digital data, comprising:
- means for producing a transmission signal which is phase modulated in accordance with "mark" and "space" states of an applied digital signal in repetitive signal time slots, each of a predetermined duration, said transmission signal having a phase reference period of predetermined time duration in total provided at at least one of the front and rear portions of each of said time slots during which said transmission signal assumes a reference phase value, and in the first half of the remaining portion of each said time slot the phase of said transmission signal changes stepwise in a predetermined direction in correspondence to the "mark" state of said digital signal while, in the second half, the phase of said trasmission signal changes stepwise in a direction opposite to said predetermined direction to said reference phase value, and in correspondence to the "space" state of said digital signal the phase of said transmission signal is changed in a direction opposite to that in the case of the "mark" state of said digital signal, means for applying said digital signal to said producing means; and
,means for demodulating said transmission signal to reproduce said digital signal and comprising;
means for dividing said transmission signal into two signals,means for delaying one of said two signals relative to the other to produce a pair of relatively delayed signals, andmeans for comparing said pair of relatively delayed signals to produce a signal representative of said digital signal.
1 Assignment
0 Petitions
Accused Products
Abstract
A modem system is disclosed which has an improved reliability of detection of PSK data using a simple signal delay detection scheme. A transmission signal is produced which has a phase reference portion provided at at least one of the front and rear portions of a time slot. In a first half of the remaining portion of the time slot the phase of the transmission signal changes stepwise in a first predetermined direction for a "mark" state while in a second half of the remaining portion it changes stepwise back to the reference value. For a "space" state the phase changes stepwise in a second predetermined direction, opposite the first, in the first half of the remaining portion and then in the second half it changes stepwise back to the reference value. In a second aspect of the invention only one of the two digital states causes a corresponding phase change while for the other state the transmission signal retains the phase reference value throughout the time slot.
-
Citations
12 Claims
-
1. A modem system for digital data, comprising:
-
means for producing a transmission signal which is phase modulated in accordance with "mark" and "space" states of an applied digital signal in repetitive signal time slots, each of a predetermined duration, said transmission signal having a phase reference period of predetermined time duration in total provided at at least one of the front and rear portions of each of said time slots during which said transmission signal assumes a reference phase value, and in the first half of the remaining portion of each said time slot the phase of said transmission signal changes stepwise in a predetermined direction in correspondence to the "mark" state of said digital signal while, in the second half, the phase of said trasmission signal changes stepwise in a direction opposite to said predetermined direction to said reference phase value, and in correspondence to the "space" state of said digital signal the phase of said transmission signal is changed in a direction opposite to that in the case of the "mark" state of said digital signal, means for applying said digital signal to said producing means; and
,means for demodulating said transmission signal to reproduce said digital signal and comprising; means for dividing said transmission signal into two signals, means for delaying one of said two signals relative to the other to produce a pair of relatively delayed signals, and means for comparing said pair of relatively delayed signals to produce a signal representative of said digital signal. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. A modem system for digital data comprising,
means for producing a transmission signal which is phase-modulated in accordance with "mark" and "space" states of an applied digital signal in repetitive signal time slots, each of a predetermined duration, said transmission signal having a phase reference period of predetermined duration provided at at least one of the front and rear portions of each of said time slots during which said transmission signal assumes a reference phase value, and in the front half of the remaining period of each of said time slots a phase which changes for one of said states of said digital signal from said reference phase value to a predetermined value in a predetermined direction, while in the rear half of the remaining period, a phase which changes in the opposite direction back to said reference phase value, and in correspondence to the other state of said digital signal, only said reference phase value is formed over an entire time slot of said transmission signal; - and
means for applying said digital signal to said producing means.
- and
-
8. A modem system for digital data comprising
means for producing a transmission signal which is phase-modulated in accordance with "mark" and "space" states of an applied digital signal in repetitive signal time slots, each of a predetermined duration, said transmission signal having a phase reference period of predetermined duration provided at at least one of the front and rear portions of each of said time slots during which said transmission signal assumes a reference phase value, and in the front half of the remaining period of said time slots, a phase which changes for one of said states of said digital signal from said reference phase value to a predetermined value in a predetermined direction, while in the rear half of the remaining period, a phase which changes in the opposite direction back to said reference phase value, and in correspondence to the other state of said digital signal, only said reference phase part is formed over an entire time slot of said transmission signal, means for applying said digital signal to said producing means, and means for demodulating said transmission signal to reproduce said digital signal, said demodulating means comprising: -
means for dividing said transmission signal into two signals, means for delaying one of said two signals relative to the other to produce a pair of relatively delayed signals, and means for comparing said pair of relatively delayed signals to produce a signal representative of said digital signal. - View Dependent Claims (9, 10, 11)
-
-
12. A modem system for digital data, comprising:
-
means for producing a transmission signal which is phase modulated in accordance with "mark" and "space" states of an applied digital signal in repetitive signal time slots, each of a predetermined duration, said transmission signal having a phase reference period of predetermined time duration in total provided at at least one of the front and rear portions of each of said time slots during which said transmission signal assumes a reference phase value, and in the first half of the remaining portion of each said time slot the phase of said transmission signal changes stepwise in a predetermined direction in correspondence to the "mark" state of said digital signal while, in the second half, the phase of said transmission signal changes stepwise in a direction opposite to said predetermined direction to said reference phase value, and in correspondence to the "space" state of said digital signal the phase of said transmission signal is changed in a direction opposite to that in the case of the "mark" state of said digital signal, and, means for applying said digital signal to said producing means.
-
Specification