SYNCHRONIZATION AND POSITION LOCATION SYSTEM

• US 3,742,498 A
• Filed: 05/06/1970
• Issued: 06/26/1973
• Est. Priority Date: 05/06/1970
• Status: Expired due to Term

• Current Assignee: ITT Corporation (ITT, Inc.)
• Original Assignee: James G. Dunn
• Inventors: Dunn, James G.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Montone, G. E.
• Application Number:
  US05/035,049
• Time in Patent Office: 1,147 Days
• Field of Search: 343/7.5,6.5R,5.6LC,112TC,1ST 179/15BS 325/4
• US Class Current: 342/88
• CPC Class Codes: G01S 13/82 wherein continuous-type signals are transmitted
• CPC Class Codes: H04B 7/18508 with satellite system used as relay, i.e. aeronautical mobile satellite service
• CPC Class Codes: H04B 7/2126 using a reference station
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A master station and N slave stations include synchronization equipment to enable each of the stations to have access to a common repeater in a different one of M time slots of a TDM format at the repeater, there being motion between the master and slave stations and the repeater. Each time slot is employed on a push-to-talk basis for N/M slave stations. The master station propagates a reference sync burst through the repeater. Each of the stations receive this master sync burst from the repeater. The master station adjusts the frequency of the timing signals therein to compensate for the doppler shift experienced in the propagation path from the master station to the repeater and each of the slave stations adjusts the frequency of the timing signals therein to compensate for the doppler shift experienced in the propagation path from each of the slave stations to the repeater so that the desired frequency of the timing signals is present at the repeater. The master station in response to the received master sync adjusts its timing signals so that the signals propagated therefrom arrive in the proper time slot of the TDM format at the repeater. Each of the slave stations propagate a different low power level, psuedo noise code ranging signal through the repeater to the master station. The phase information of this ranging signal is detected in the master station, coded, and transmitted to the appropriate one of the slave stations. This phase information is responded to in the appropriate slave station to adjust the phase of its timing signals so that data bursts of each of the slave stations appear in the proper time slot of the TDM format at the repeater. The ground station responds to the phase of the received master reference signal and the phase information of the ranging signal to provide a measure of the satellite-to-slave station range at the ground station. In a single satellite system, the altitude of the slave stations and the rate of change or range, obtained from measuring the doppler of the carrier signal received at the associated slave station and is transmitted to the ground station in slow speed data channels provided during the synchronizing interval of each of the data bursts. These two bits of information together with the satellite-to-slave station range enables the ground station to locate the position of a particular slave station. In a two satellite system, the equipment for determining the satellite-toslave station range is duplicated for cooperation with a second satellite so that the altitude of the slave station and the satellite-to-repeater range for both satellites enable the position location of a particular slave station at the ground station.

Claims

1. A time division multiple access synchronization system to control the transmission of signals from each of a master station and N slave stations to be propagated through at least one common repeater in a selected one of M time slots of a time division multiplex frame format at said repeater, said stations and said repeater having relative motion therebetween, where N is an integer greater than one and M is an integer greater than one but less than N and an even multiple of N, first means disposed in said master station to transmit a master sync burst through said repeater in one of said time slots;

second means disposed in said master station responsive to said master sync burst from said repeater to control the production of timing signals employed to control the time of transmission of said master sync and others of said transmitted signals from said master station;

third means disposed in each of said slave stations responsive to said master sync from said repeater to control the production of timing signals employed to control the time of transmission of said transmitted signals from the associated one of said slave stations;

fourth means disposed in each of said slave stations coupled to the associated one of said third means to transmit a ranging signal through said repeater in its associated one of said time slots;

fifth means disposed in said master station coupled to said second means to detect the phase difference between said master sync burst from said repeater and said ranging signal received from said associated one of said slave stations through said repeater;

sixth means disposed in said master station coupled to said second and fifth means to transmit said phase difference through said repeater in said associated one of said time slots to the associated one of said slave station; and

seventh means disposed in each of said slave stations coupled to said third means responsive to said phase difference pertinent to the associated one of said slave stations to adjust the phase of said timing signals produced by said third means so that said time of transmission of said transmitted signals from the associated one of said slave stations is such that said transmitted signals occur in the proper one of said time slots at said repeater.

2. A system according to claim 1, further including eighth means disposed in said master station coupled to said second means and said fifth means responsive to said master sync burst from said repeater and said ranging signal received from said associated one of said slave stations through said repeater to measure and provide an indication of the range between said repeater and said associated one of said slave stations.

3. A system according to claim 1, wherein said ranging signal includes a low power level pseudo noise code signal.

4. A system according to claim 1, wherein each of said time slots of said frame includes a first interval for transmission of at least said ranging signal, and a second interval for data transmission;

N/M slave stations utilize said second interval of each of said time slots on a push-to-talk basis; and

said second and third means produce first timing signals to define each of said time slots of said frame, and second timing signals to define at least N/M of said first interval of each of said time slots to enable synchronization of said N/M slave stations utilizing said second interval of each of said time slots on said push-to-talk basis.

5. A system according to claim 4, wherein said second and third means further produce third timing signals to define at least L of said N/M of said first interval of each of said time slots to enable X of said L of said N/M of said first interval of each of said time slots to provide said ranging signal in the form of a low power level pseudo noise type of code signal, where L is an integer greater than N/M but less than N and X is an integer greater than one but less than L.

6. A system according to claim 5, further including eighth means disposed in each of said slave stations coupled to said third means and ninth means disposed in said master station coupled to said second means to enable utilization of (X-1) of said L of said N/M of said first interval of each of said time slots as slow speed data channels between said master station and said slave stations.

7. A system according to claim 6, further including tenth means disposed in each of said slave stations coupled to said third and eighth means to detect the rate of change of range between said repeater and the associated one of said slave stations and to transmit said rate of change of range to said master station on a selected one of said slow speed data channels;

and eleventh means disposed in each of said slave stations to determine the altitude thereof and to transmit said altitude to said master station on another one of said slow speed data channels.

8. A system according to claim 7, further including twelfth means disposed in said master station coupled to said second means and said fifth means to measure and provide an indication of the range between said repeater and the associated one of said slave stations;

and thirteenth means disposed in said master station to provide an indication of said rate of change of range and said altitude;

said rate of change of range, said range and said altitude cooperating to locate the position of the associated one of said slave stations.

9. A system according to claim 6, further including a second common repeater;

duplication of said first through ninth means for operation with said second repeater;

tenth means disposed in each of said slave stations to determine the altitude thereof and to transmit said altitude to said master station on a selected one of said slow speed data channels;

eleventh means disposed in said master station coupled to said second means and said fifth means to measure and provide an indication of the first range between said first repeater and the associated one of said slave stations; and

twelfth means disposed in said master station coupled to said duplicate second means and said duplicate fifth means to measure and provide an indication of the second range between said second repeater and said associated one of said slave stations;

said altitude, said first range and said second range cooperating to locate the position of said associated one of said slave stations.

10. A system according to claim 6, wherein said sixth means transmits said phase difference on a selected one of said slow speed data channels.