Synchronizer for time division multiple access satellite communication system

Claim 2

A synchronizer for a time division multiple access orbital satellite communication system wherein plural earth stations transmit signal bursts to an orbiting satellite relay station to be relayed thereby to earth stations, each transmitting station being assigned a time slot in the satellite time frame, each station''s transmission including a synchronizing signal, one of said earth transmitting stations being designated a master station and the other being designated slave stations, and each slave station including detector means for detecting master synchronizing signals and said slave station''s synchronizing signals relayed from said orbiting satellite relay station to provide corresponding master and slave synchronizing pulses, respectively said synchronizer comprising: a. a correction rate circuit for normally selecting an associated pair or synchronizing pulses at correction times occurring once every (2Td+a) seconds, where Td is the time for a signal burst to travel from said slave station to the satellite and a >0, an associated pair of synchronizing pulses being defined as a master synchronizing pulse and a slave synchronizing pulse which occur in the same frame time; b. comparing means coupled to said correction rate circuit for comparing the phases of an associated pair of synchronizing pulses; c. means coupled to said comparing means for controlling the time at which said slave station transmits; and d. synchronization loss detector means coupled to said correction rate circuit for detecting the absence of either one of an associated pair of synchronizing pulses at one of said correction times.

Claim 3

A synchronizer as defined in claim 1 wherein said synchronization loss detecting means comprises means for causing said selecting means in said correction rate circuit to search for an associated pair of synchronizing pulses in successive frame times when an associated pair of pulses is not found at a correction time.

Claim 4

storage means for storing said error signal and for changing the period of said counter until said error signal is zero, thereby changing said slave station''s transmission time so that its burst appears in its assigned time slot.

Claim 5

storage means for storing said error signal and for changing the period of said counter until said error signal is zero, thereby changing said slave station''s transmission time so that its burst appears in its assigned time slot.

Claim 6

means for producing an error signal dependent upon the phase difference between said slave synchronizing pulse and said delayed master synchronizing pulse; and b. means for controlling the time at which said slave station transmits comprising:

Claim 7

means for producing an error signal dependent upon the phase difference between said slave synchronizing pulse and said delayed master synchronizing pulse; and b. means for controlling the time at which said slave station transmits comprising:

Claim 8

A synchronizer as defined in claim 2 wherein said synchronization loss detecting means comprises means for disabling the earth station transmitter when a predetermined number of successive frame times pass without a selection of an associated pair of master and slave synchronizing pulses.

Claim 9

A synchronizer as defined in claim 1 wherein said signal bursts contain information bit signals and further comprising: a. delay means coupled between said correction rate circuit and said comparing means foR delaying a selected master pulse for a time interval equal to the number of time slots between the master station and the time slot assigned to said slave station, whereby a time slot may be variable in both length and position within the frame, said comparing means further comprising: b. means for generating an error signal corresponding to the difference in phase between said selected slave pulse and the delayed selected master pulse.

Claim 10

A synchronizer as defined in claim 4 wherein said transmission time controlling means further comprises digital control means coupled to said comparing means and responsive to said error signal for adjusting said slave station''s transmission time one bit per frame for successive frames until said error signal is zero.

Claim 11

A synchronizer as defined in claim 5 wherein said digital control means further comprises: a. a burst position control counter coupled to said transmission time controlling means for initiating transmission of said slave station''s burst; b. a reversible counter for storing said error signal; and c. a burst control counter reset circuit coupled between said burst position control counter and said reversible counter for determining the scale of said burst control counter.

Claim 12

A synchronizer as defined in claim 6 wherein the normal period of said burst control counter is one frame time.

Claim 13

A synchronizer as defined in claim 7 wherein said digital control means further comprises: a. means responsive to a phase difference of one polarity to decrease the period of said burst control counter by one bit period and responsive to a phase difference of the opposite polarity to increase the period of said burst control counter by one bit period.

Claim 14

A synchronizer as defined in claim 8 further comprising means for changing the period of said burst control counter to any desired value for only one counter cycle and then returning said burst control counter to said normal period.

Claim 15

A synchronizer for a time division multiple access orbital satellite communications system wherein plural earth stations transmit signal bursts to an orbiting satellite relay station to be relayed thereby to earth stations, each transmitting station being assigned a time slot in the satellite time frame, each station''s transmission including a synchronizing signal, one of said earth transmitting stations being designated a master station and the others being designated slave stations, and each slave station including detector means for detecting master synchronizing signals and said slave station''s synchronizing signals relayed from said orbiting satellite relay station to provide corresponding master and slave synchronizing pulses, respectively, said synchronizer comprising: a. means for comparing a master synchronizing pulse and a slave station synchronizing pulse occurring in the same frame time, said comparing means comprising:

Claim 16

A synchronizer for a time division multiple access orbital satellite communications system wherein plural earth stations transmit signal bursts to an orbiting satellite relay station to be relayed thereby to earth stations, each transmitting station being assigned a time slot in the satellite time frame, each station''s transmission including a synchronizing signal, one of said earth transmitting stations being designated a master station and the others being designated slave stations, and each slave station including detector means for detecting master synchronizing signals and said slave station''s synchronizing signals relayed from said orbiting satellite relay station to provide corresponding master and slave synchronizing pulses, respectively, said synchronizer comprising: a. means for comparing a master synchronizing pulse and a slave station synchronizing pulse occurring in the same frame time, said comparing means comprising:

Claim 17

A synchronizer as defined in claim 10 wherein said counter means is a burst position control counter, and said storage means changes said period each frame for successive frames by an amount less tHan the total phase difference until said slave station''s burst appears in its assigned time slot.

Claim 18

A synchronizer as defined in claim 11 wherein said bursts consist of bit signals and wherein said storage means changes said period one bit per frame for successive frames.

Claim 19

A synchronizer as defined in claim 10 further comprising: a. a correction rate circuit for normally selecting an associated pair of synchronizing pulses at correction times occurring once every (2Td+a) seconds, where Td is the time for a signal burst to travel from said slave station to the satellite and a >0, an associated pair of synchronizing pulses being defined as a master synchronizing pulse and a slave synchronizing pulse which occur in the same frame time; and b. synchronization loss detector means coupled to said correction rate circuit for detecting the absence of either one of an associated pair of synchronizing pulses at one of said correction times.

Claim 20

A synchronizer as defined in claim 13 wherein said synchronization loss detecting means comprises means for causing said selecting means in said correction rate circuit to search for an associated pair of synchronizing pulses in successive frame times when an associate pair of synchronizing pulses in successive frame times when an associate pair of pulses is not found at a correction time.

Claim 21

A synchronizer as defined in claim 14 wherein said synchronization loss detecting means comprises means for disabling the earth station transmitter when a predetermined number of successive frame times pass without a selection of an associated pair of master and slave synchronizing pulses.

Claim 22

In a time division multiple access orbital satellite communication system wherein plural earth stations transmit signal bursts to an orbiting satellite relay station to be relayed thereby to earth stations, each transmitting station being assigned a time slot in the satellite time frame, each station''s transmission including a synchronizing signal, one of said earth transmitting stations being designated a master station and the others being designated slave stations, and each slave station including detector means for detecting master synchronizing signals and said slave station''s synchronizing signals relayed from said orbiting satellite relay station to provide corresponding master and slave synchronizing pulses, respectively, the method of synchronizing a slave station with said master station comprising the steps of: a. normally selecting at said slave station an associated pair of synchronizing pulses at correction times occurring once every (2Td+a) seconds, where Td is the time for a signal burst to travel from said slave station to the satellite and a >0, an associated pair of synchronizing pulses being defined as a master synchronizing pulse and a slave synchronizing pulse which occur in the same frame time; b. comparing the phases of said associated pair of synchronizing pulses to produce an error signal indicative of the difference in phase there between; and c. controlling the time at which said slave station transmits in accordance with said error signal, and detecting the absence of either one of said associated pair of synchronizing pulses at one of said correction times.

Claim 23

In a time division multiple access orbital satellite communication system wherein plural earth stations transmit signal bursts to an orbiting satellite relay station to be relayed thereby to earth stations, each transmitting station being assigned a time slot in the satellite time frame, each station''s transmission including a synchronizing signal, one of said earth transmitting stations being designated a master station and the others being designated slave stations, and each slave station including detector means for detecting master synchronizing signals and said slave station''s synchronizing signals relayed from said orbiting satellite relay station to provide corresponding master and slave synchronizing pulses, respectively, the method of synchronizing a slave station with said master station comprising the steps of: a. normally selecting at said slave station an associated pair of synchronizing pulses at correction times occurring once every (2Td+a) seconds, where Td is the time for a signal burst to travel from said slave station to the satellite and a >0, an associated pair of synchronizing pulses being defined as a master synchronizing pulse and a slave synchronizing pulse which occur in the same frame time; b. comparing the phases of said associated pair of synchronizing pulses to produce an error signal indicative of the difference in phase there between; and c. controlling the time at which said slave station transmits in accordance with said error signal, and detecting the absence of either one of said associated pair of synchronizing pulses at one of said correction times.

Claim 24

The method as defined in claim 16 further comprising the step of searching for an associated pair of synchronizing pulses in successive frame times when an associated pair of pulses is not found at a correction time.

Claim 25

The method as defined in claim 17 further comprising the step of disabling the slave station''s transmitter when a predetermined number of successive frame times pass without a selection of an associated pair of master and slave synchronizing pulses.

Claim 26

In a time division multiple access orbital satellite communication system wherein plural earth stations transmit signal bursts consisting of bit signals to an orbiting satellite relay station to be relayEd thereby to earth stations, each transmitting station being assigned a time slot in the satellite time frame, each station''s transmission including a synchronizing signal, one of said each transmitting stations being designated a master station and the others being designated slave stations, and each slave station including detector means for detecting master synchronizing signals and said slave station''s synchronizing signals relayed from said orbiting satellite relay station to provide corresponding master and slave synchronizing pulses, respectively, the method of synchronizing a slave station with said master station comprising the steps of: a. delaying a master synchronizing pulse for a time interval equal to the number of time slots between the master station''s time slot and the time slot assigned to a slave station; b. comparing the phases of said slave synchronizing pulse and said delayed master synchronizing pulse to produce an error signal indicative of the difference in phase therebetween; c. storing the error signal; d. initiating the transmission of a burst from said slave station once each frame time under the control of counter means; and e. changing the time of initiation of the transmission of said burst by changing the period of said counting means in accordance with said stored error signal, thereby changing said slave station''s transmission time so that its burst appears in its assigned time slot.

Claim 27

In a time division multiple access orbital satellite communication system wherein plural earth stations transmit signal bursts consisting of bit signals to an orbiting satellite relay station to be relayEd thereby to earth stations, each transmitting station being assigned a time slot in the satellite time frame, each station''s transmission including a synchronizing signal, one of said each transmitting stations being designated a master station and the others being designated slave stations, and each slave station including detector means for detecting master synchronizing signals and said slave station''s synchronizing signals relayed from said orbiting satellite relay station to provide corresponding master and slave synchronizing pulses, respectively, the method of synchronizing a slave station with said master station comprising the steps of: a. delaying a master synchronizing pulse for a time interval equal to the number of time slots between the master station''s time slot and the time slot assigned to a slave station; b. comparing the phases of said slave synchronizing pulse and said delayed master synchronizing pulse to produce an error signal indicative of the difference in phase therebetween; c. storing the error signal; d. initiating the transmission of a burst from said slave station once each frame time under the control of counter means; and e. changing the time of initiation of the transmission of said burst by changing the period of said counting means in accordance with said stored error signal, thereby changing said slave station''s transmission time so that its burst appears in its assigned time slot.

Claim 28

The method as defined in claim 19 further comprising changing said period each frame for successive frames by an amount less than the total phase difference until said slave station''s burst appears in its assigned time slot.

Claim 29

The method as defined in claim 20 further comprising changing said period one bit per frame for successive frames.

Claim 30

The method as defined in claim 19 wherein said comparing step is normally performed once every (2Td+a) seconds, where Td is the time for a signal burst to travel from said slave station to the satellite and a >0, an associated pair of synchronizing pulses being defined as a master synchronizing pulse and a slave synchronizing pulse which occur in the same frame time, and further comprising detecting the the absence of either a master of slave synchronizing pulse, and disabling said slave station''s transmitter upon the occurrence of such an absence.