Parallel precise time transfer to multiple GPS units

Details Parallel precise time transfer to multiple GPS units Parallel precise time transfer to multiple GPS units

2000-02-18

2004-01-27

Ngo, Ricky (Department: 2664)

Multiplex communications

Communication over free space

Combining or distributing information via time channels

C370S522000, C455S456100, C455S456500

Reexamination Certificate

active

06683867

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to global positioning systems (GPS), and more particularly relates to communication to multiple GPS receivers.
BACKGROUND OF THE INVENTION
In the past, designers of GPS receiver systems have frequently used one GPS receiver to provide precise time information to another GPS receiver. Typically, the time source GPS is coupled to the time receiving GPS receiver by a serial data interface and a timing interface line which provides a timing pulse (or pulse train). When two or more time receiving GPS receivers are used, then separate data and time interface lines would be run to each time receiving GPS receiver. In other cases, the time receiving GPS receivers might be ganged together by connecting separate data and time sync interface lines from the output of a broadcasting GPS receiver to the input of multiple GPS receivers.
In some applications, it may be desirable to include many GPS receivers in a single deployable unit. For example, numerous surveillance units may be dropped in an area to be monitored, via an airdrop. In such cases, to conserve battery life, the GPS receivers may be turned off until just before deployment. In such cases, it may be desirable to quickly initialize the many GPS receivers by a single time standard (such as a reference GPS receiver used by the airplane navigation system) prior to the airdrop.
While these prior art interfaces have been used extensively in the past, they have several drawbacks. First of all, the direct wiring approach becomes increasingly cumbersome as the number of time receiving GPS receivers grows. Additionally, the ganged approach is undesirable because as the number of time receiving GPS receivers grows, the number of connections grows. With each additional connection, there is an increased potential for a failed connection, which would affect all “downstream” GPS receivers. Furthermore, separate interfaces for serial data and time synchronization pulses doubles the total number of connections required. This becomes more burdensome when a larger number of receivers must be initialized.
Consequently, there exists a need for improvement in systems and methods for communicating with multiple GPS receivers.
SUMMARY OF THE INVENTION
It is an object of the present invention to facilitate ease of communication with multiple GPS receivers.
It is another object of the present invention to provide an enhanced method of communicating to a network of GPS receivers.
It is a feature of the present invention to utilize a single serial line to interconnect numerous GPS receivers.
It is another feature of the present invention to include a single 2-to-1 multiplexor coupled to a source of a precise time pulse and serial data.
It is an advantage of the present invention to better enable sharing of information with a network of GPS receivers.
It is another advantage of the present invention to reduce weight in a multiple GPS system.
It is yet another advantage of the present invention to reduce the potential for single connection faults that could break communication paths to multiple GPS receivers.
The present invention is an apparatus and method for communicating information with GPS receivers, which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. The present invention is carried out in a “direct wire” in a sense that the number of direct independent wires has been greatly reduced.
Accordingly, the present invention is a system and method for communicating information with multiple GPS receivers, which uses a single serial data/timing line interconnecting multiple GPS receivers. This line alternates between data transmission and time synchronization pulses functions in a time multiplexed fashion.


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