Methods of and apparatus for measuring time of arrival of remote Loran-C and related signals and effective time of transmission of local signals at transmitter sites

• US 4,791,422 A
• Filed: 07/14/1986
• Issued: 12/13/1988
• Est. Priority Date: 07/14/1986
• Status: Expired due to Fees

• Current Assignee: Megapulse, Inc.
• Original Assignee: Megapulse, Inc.
• Inventors: Goddard, Robert B.
• Primary Examiner(s): Blum, Theodore M.
• Assistant Examiner(s): Sotomayor, John B.
• Application Number:
  US06/886,258
• Time in Patent Office: 883 Days
• Field of Search: 342/389, 342/169, 342/165, 342/173, 434/5, 434/1, 434/2, 364/452
• US Class Current: 342/389
• CPC Class Codes: G01S 1/024 of beacon transmitters
• CPC Class Codes: G01S 1/24 the synchronised signals being pulses or equivalent modulations on carrier waves and the transit times being compared by measuring the difference in arrival time of a significant part of the modulations , e.g. LORAN systems
• CPC Class Codes: G01S 11/08 using synchronised clocks

Abstract

A method of and apparatus for measuring time of arrival of remote Loran-C and related signals and effective time of transmission of local signals at Loran transmitter sites through use of a simulated Loran signal locally generated and coupled into the receiving antenna system that receives the remote signals in a time slot not occupied by the local transmitted signal.

Claims

1. A method of measuring time of arrival (TOA) of Loran-C and similar signals from a remote transmitter at a local transmitter located at the same site at which the remote signal is to be received in a receiving antenna disposed within a short distance of the antenna field of the local transmitter, that comprises, receiving at the receiving antenna the remote signal from the said remote transmitter;

generating at said site a simulated Loran signal in a fixed, known time relationship to the signal locally transmitted by the local transmitter;

coupling the simulated signal into the receiving antenna;

measuring the time of arrival of the remote signal received in the receiving antenna from the same remote transmitter and comparing the same with the simulated signal; and

clocking the simulated signal to occur in a time slot not occupied by the signal from the local transmitter.

2. A method of measuring time of arrival of Loran-C and similar signals from a remote transmitter at a local transmitter located at the same site at which the remote signal is to be received, as claimed in claim 1 and in which the said receiving of the remote signal from the remote transmitter is effected in a loop antenna located at said site in the vicinity of the local transmitter antenna and other reflecting objects that also introduce scattered components of the said remote signal into the loop antenna;

orienting the loop in a plane substantially disposed at the right angles to the direction between the transmitters to obviate phase shifts in the received signals that could result from such scatter of the remote signal in order to obviate errors in the time of arrival measurement.

4. A method as claimed in claim 1 and in which the transmitters are operated in range-range Loran-C master-slave mode.

3. A method of measuring time of arrival of radio signals from a remote transmitter with respect to a local clock system located at the same site at which the remote signal is to be received in a receiving antenna that comprises, receiving at the receiving antenna the remote radio signal from the said remote transmitter;

generating from the clock system at said site a simulated similar radio signal in a fixed, known time relationship to the local clock system;

coupling the simulated radio signal into the receiving antenna; and

measuring the time of arrival of the remote radio signal received in the receiving antenna from the said remote transmitter and comparing the same with the simulated radio signal.

5. In the measuring of time of arrival of Loran C and similar signals from a remote transmitter at a local transmitter site at which the remote signal is to be received within a short distance of the antenna field of the local transmitter, the method that comprises, receiving the remote signal in a receiving antenna system on said site;

generating on said site a local simulated Loran-C signal in a coding delay time relationship to the signal to be transmitted at said site by the local transmitter;

closely coupling the simulated signal into said receiving antenna system;

the time delay between the said time of arrival of the remote signal and the time of the simulated signal minus the coding delay at the local transmitter to determine the time of signal transmission by the local transmitter.

6. A method of measuring time of arrival of Loran-C and similar signals from a remote transmitter at a local transmitter located at the same site at which the remote signal is to be received, that comprises receiving the remote signal from the remote transmitter in a loop antenna located at said site in the vicinity of the local transmitter antenna and other reflecting objects that also introduce scattered components of the said remote signal into the loop antenna;

measuring the time of arrival of said remote signal as received in the loop antenna; and

orienting the loop in a plane substantially disposed at rights angles to the direction between the transmitters to obviate phase shifts in the received signals that could result from such scatter of the remote signal in order to obviate errors in the time of arrival measurement.

7. Apparatus for measuring time of arrival of radio signals from a remote transmitter with respect to a local clock system located at the same site at which the remote signal is to be received in a receiving antenna, that comprises, means for receiving at the receiving antenna the remote radio signal from the said remote transmitter;

means for generating from the clock system at said site a simulated similar radio signal in a fixed, known time relationship to the local clock;

means for coupling the simulated radio signal into the receiving antenna; and

means for measuring the time of arrival of the remote radio signal received in the receiving antenna from the said remote transmitter and comparing the same with the simulated radio signal.

8. Apparatus, as claimed in claim 7 and in which the said signals are Loran-C signals and a local transmitter is located at the same site with the said receiving antenna disposed within a short distance of the antenna field of the local transmitter, the generated simulated signal is a simulated Loran signal, and means is provided for clocking the simulated signal to occur in a time slot not occupied by the signal from the local transmitter.

9. Apparatus, as claimed in claim 8 and in which said receiving antenna is a loop antenna oriented in a plane subsantially disposed at right angles to the direction between the transmitters to obviate phase shifts in the received signals that could result from such scatter of the remote signal in order to obviate errors in the time of arrival measurement.