Communications: directive radio wave systems and devices (e.g. – Determining distance – With remote cooperating station
Patent
1997-02-05
1998-09-08
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Determining distance
With remote cooperating station
342 42, 342145, 342189, G01S 1326
Patent
active
058051058
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to tracking systems and in particular to a radio range finder to measure the distance between a remote transponder and a reference location.
BACKGROUND ART
Communication systems for identifying and locating a mobile transponder from a fixed reference location are well known in the art and have been used in many environments including aeronautics. For example, one known tracking system includes an RF transmitter located at the reference location for transmitting a signal encoded with identification data which is to be received by the mobile transponders to be tracked. Upon receiving the encoded signal and determining that the encoded signal is addressed to the mobile transponder, the mobile transponder transponds a return signal at a different frequency than the original transmitted signal which is to be received by a receiver at the reference location. Ancillary and conditional functioning information of the mobile transponder can be superimposed on the transponded signal.
When the receiver receives the transponded signal, the identity and location of the addressed mobile transponder can be determined. However, although the location of the mobile transponder is known, its distance from the reference location is not readily available.
It is therefore an object of the present invention to provide a novel radio range finder and a radio range finding system to measure the distance between a remote transponder and a reference location.
DISCLOSURE OF THE INVENTION
According to one aspect of the present invention there is provided a radio range finder comprising: transponded in response to said transmitted signal; and generating an output signal proportional to the distance of said remote transponder from said radio range finder.
According to another aspect of the present invention there is provided a radio range finding system comprising: transponding a return signal in response to said transmitted signal; generating an output signal proportional to the distance of said remote transponder from said receiver.
In one embodiment it is preferred that the processing means includes means to determine the delay between the transmitted and return signals and means to generate the output signal in response to the determining means. It is also preferred that the radio range finding system further includes addressing means acting in conjunction with the transmitter for addressing transmitted signals to identify a particular remote transponder. In this case, each of the at least one remote transponders includes address detection means to detect transmitted signals addressed thereto and for enabling the remote transponder to transpond a return signal when a properly addressed transmitted signal is received.
The present invention provides advantages in that the design of the radio range finder is simple yet permits accurate distance measurements between the reference location and the remote transponder to be made.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the present invention will now be described more fully with reference to the accompanying drawings in which:
FIG. 1 is a block diagram showing the overall configuration of a full duplex radio range finding system according to the present invention;
FIG. 2 is a block diagram of the radio range finder circuitry forming part of the system of FIG. 1;
FIG. 3 is a block diagram of a chip code generator forming part of the circuitry of FIG. 2; and
FIG. 4 is a diagrammatic representation of an original transmitted signal, a return signal received from the transponder, and the time delay between the two signals.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to FIG. 1, a radio range finding system is shown and is generally indicated by reference numeral 10. System 10 includes a radio range finder 12 and a plurality of remote mobile transponders 14, only one of which is shown. The radio range finder 12 transmits a modulated signal M.sub.s which is received by each of the mobile transponders 14. The transmitted
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