Location confirming system

• US 5,621,414 A
• Filed: 06/08/1994
• Issued: 04/15/1997
• Est. Priority Date: 06/08/1993
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Nakagawa, Yoshikatsu
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): PHAN, DAO LINDA
• Application Number:
  US08/257,678
• Time in Patent Office: 1,042 Days
• Field of Search: 342/463, 342/457, 342/465, 342/460, 342/464, 342/350, 455/33.1
• US Class Current: 342/350
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

It is enabled to perform the location confirmation as precisely as possible at a small number of receiving stations. In the respective stations, after performing the operation of filtering and amplifying at the front end portion, the signal passes through the discriminating portion corresponding to the transmission signal from the transmitter. Thereafter, the electric power or amplitude of the signal emitted from each transmitter is measured. The measured value is sent to the central station through the backbone communication network. The more the transmission distance of the electric wave is, the more the electric wave attenuates.

Consequently, it is possible to know the zone in which the worker carrying the transmitter is staying nearby by respectively comparing with each other the electric powers of the respective signals; a, b, and c transmitted from the transmitters a-c measured by the respective receivers.

The transmitters generating the specific signals respectively are given to the respective workers, and it is possible to estimate the zone in which the worker is staying and to confirm the location of the worker by giving the receiver in each zone a function of discriminating all of those signals from the others.

Claims

1. A location confirming system having movable objects existing in a limited area and carrying respective transmitters emitting respective signals, comprising:

means for monitoring and receiving the respective signals at a plurality of receiving stations arranged respectively in zones using only a unidirectional signal path from said transmitters to said receiving stations, and

means for determining one of said zones in which one of said transmitters is present by comparing magnitudes of electric power of said signals with each other at said respective receiving stations.

2. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 1, wherein said system further comprises:

means for allocating in each of said zones a carrier wave which is successively transmitted by said respective objects, said carrier waves having different frequencies, and

filters of a number equal to that of the allocated frequency prepared in said receiving stations of the respective zones in said system, the signals from said each object are separated from each other, and

a zone in which said object exists is determined by comparing the respective electric powers or amplitudes of said received signals with each other between said respective stations.

3. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 2, wherein said system further comprises:

first means for determining an existing-area zone in which a carrier wave of same frequency is employed,

a signal diffusively modulated with a suspected noise code unique to each said object is emitted from each of said transmitters carried by said respective objects and is successively transmitted,

a suspected noise signal same as a suspected noise code allocated to each of said respective objects at said receiving stations of said each zone is calculated correlatively as a reference signal for each said zone, and

a zone in which said object exists is determined by comparing the magnitudes of said suspected noise signals for each signal with each other between said respective receiving stations.

4. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 2, wherein said system further comprises:

transmitting means for operating intermittently said transmitter carried by said each object and employing said means for allocating at a time interval corresponding to a time required for said measured object to move in said zone.

5. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 2, wherein

said system is a receiving station of said location confirming system by use of said means for allocating and employing a transmitting means for operating intermittently said transmitter carried by said each object at a time interval corresponding to a time required for said measured object to move in said zone, and

said system further comprises receiving means for determining an existing-area zone capable of measuring the electric power or amplitude of said signal only during the time period of transmitting said signal.

6. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 1, wherein said system further comprises:

means for determining an existing-area zone in which discrimination data inherent in said respective objects are allocated,

a carrier wave of same frequency as that of the data is modulated with an optional modulating method by said discrimination data as the signal transmitted by said respective objects is employed,

said respective objects transmit intermittently said discrimination data signal for each object at different time intervals,

said receiving station of said each zone demodulates said modulated signal, takes out said discrimination data, and discriminates said received signal, and

a zone in which said object exists is determined by comparing electric power or amplitudes of said received signals with each other.

7. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 3, wherein said system further comprises:

intermittent transmitting means for operating intermittently said transmitter carried by said each object at a time interval corresponding to a time required for said measured object to move in said zone,

means for setting the transmitting time intervals of the signals emitted from each said object to different time intervals for each of said respective objects.

8. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 1, wherein said system further comprises:

receiving means for determining an existing-area zone capable of measuring the electric power or amplitude of said signal only during a time period of transmitting said signal, and

transmitting means for said discrimination signal for controlling the time point of starting the transmission from said transmitter carried by said each object so as to change in time during a predetermined constant time period.

9. A location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 1, wherein said system further comprises:

receiving means for determining an existing-area zone capable of measuring the electric power or amplitude of said signal only during a time period of transmitting said signal, and

transmitting means for said discrimination signal for controlling the transmission time from said transmitter carried by said object so as to change in time during a predetermined constant time period.

23. A location confirming system as defined in claim 1, comprising a plurality of said receivers being disposed in a single building structure.

24. A location confirming system as defined in claim 23, wherein said building structure is one of an office and a factory.

25. A location confirming system as defined in claim 1, comprising a local area network interconnecting said receivers.

10. A location confirming system in which a movable object existing in a limited area carries a transmitter emitting respective signals unique to each transmitter, wherein

said respective signals are monitored and received at plural receiving stations arranged in zones using only a unidirectional signal path from said transmitters to said receiving stations, and a zone in which said transmitter carried by each object exists is determined by comparing the respective magnitudes of the received signal power with each other at said respective receiving stations,

said system comprises existing-area zone determining means having a local oscillator which allocates and successively transmits carrier waves of different frequencies corresponding to the respective signals to be transmitted by each object,

said receiving station comprises a frequency convertor for frequency-converting received signals to a constant intermediate frequency,

the signals from said respective objects are separated from each other by changing over the frequency at an optional timing, and

the zone in which said object exists is determined by comparing the electric power or amplitudes of said received signals with each other for each signal.

11. A location confirming system as defined in claim 10, wherein

said system comprises existing-area zone determining means in which a carrier wave of same frequency is employed,

a signal diffusively modulated with the suspected noise code inherent in said each object is successively transmitted from said transmitter carried by said each object,

a set of reference signal generator included in said system generates all suspected noise codes allocated to said each object at said receiving station of said each zone,

a reference signal generator is changed at an optional time interval,

correlative calculation is performed in order, and

the zone in which said each object exists is determined by comparing the magnitudes of said respective suspected noise signal with each other for each signal between said respective receiving stations.

12. A transmitter location confirming system having movable objects existing in a limited area and carrying respective transmitters emitting respective signals, wherein said system comprises:

means for monitoring and receiving the respective signals at a plurality of receiving stations arranged in zones using only a unidirectional signal path from said transmitters to said receiving stations, and

means for determining said zone in which said transmitter owned by said each object exists by comparing the magnitudes of the electric power of said respective signals received at said respective receiving stations with each other.

13. A transmitter location confirming system having movable objects existing in the limited are and carrying respective transmitters emitting the respective signals as defined in claim 12, wherein said system further comprises:

means for allocating carrier waves of different frequencies and successively transmitting said carrier waves as said respective signals transmitted by said respective objects,

and filters of a number equal to that of the allocated frequency are prepared in said receiving stations of the respective zones in said system, the signals from said each object are separated from each other, and

a zone in which said object exists is determined by comparing the respective electric power or amplitude of said received signals with each other.

14. A transmitter location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 12, wherein said system further comprises:

means for allocating a carrier wave of one frequency,

a signal diffusively modulated with a suspected noise code inherent in said each object emitted from said transmitter carried by said respective objects is successively transmitted,

a suspected noise signal the same as a suspected noise code allocated to said respective objects at said receiving station of said each zone is calculated correlatively as a reference signal, and

a zone in which said object exists is determined by comparing the magnitudes of said suspected noise signals for each signal with each other.

15. A transmitter location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting respective signals as defined in claim 13, wherein said system further comprises:

transmitting means for operating intermittently said transmitter carried by said each object employing said means for allocating at a time interval corresponding to the time required for said measured object to move in said zone.

16. A transmitter location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 12, wherein

said system is a receiving station of said location confirming system by use of said means for allocating and employing transmitting means for operating intermittently said transmitter carried by said each object at a time interval corresponding to the time required for said measured object to move in said zone, and

said system further comprises receiving means for determining an existing-area zone capable of measuring the electric power or amplitude of said signals only during the time period of transmitting said signals.

17. A transmitter location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 12, wherein

said system further comprises means for determining an existing-area zone in which discrimination data inherent in said respective objects are allocated,

a carrier wave having a frequency the same as that of the data modulated with an optional modulating method by said discrimination data as the signal transmitted by said respective objects is employed,

said respective objects transmit intermittently said discrimination data signal for each object at different time intervals, said receiving station of said each zone demodulates said modulated signal, takes out said discrimination data, and discriminates said received signal, and

a zone in which said object exists is determined by comparing the electric power or amplitude of said received signals with each other for each signal.

18. A transmitter location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 16, wherein

said system further comprises transmitting means for setting the transmitting time intervals of the signals emitted from said each object to different time intervals for said respective objects.

19. A transmitter location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 16, wherein

said system further comprises transmitting means for said discrimination signal for controlling the time point of starting the transmission from said transmitter carried by said each object so as to change in time during a predetermined constant time period.

20. A transmitter location confirming system having movable objects existing in the limited area and carrying respective transmitters emitting the respective signals as defined in claim 16, wherein said system further comprises:

transmitting means for a discrimination signal for controlling a transmission time from said transmitter carried by each object so as to change with time during a predetermined constant time period.

21. A transmitter location confirming system in which a movable object existing in a limited area carries a transmitter emitting respective signals unique to each transmitter, wherein

said respective signals are monitored and received at plural receiving stations arranged in zones using only a unidirectional signal path from said transmitters to said receiving stations, and a zone in which said transmitter carried by each object exists is determined by comparing with each other the respective magnitudes of the power of the respective signals received at said respective receiving stations,

said system comprises existing-area zone determining means having a local oscillator which allocates and successively transmits carrier waves of different frequencies corresponding to said respective signals transmitted by each object,

said receiving station comprises a frequency convertor for frequency-converting received signals to a constant intermediate frequency,

the signals from said respective objects are separated from each other by changing over the frequency at an optional timing, and

the zone in which said object exists is determined by comparing the electric power or amplitude of said received signals with each other for each signal.

22. A transmitter location confirming system as defined in claim 21, wherein

said existing-area zone determining means employs a carrier wave of one frequency,

a signal diffusively modulated with a suspected noise code unique to said each object is successively transmitted from said transmitter carried by said each object,

a set of reference signal generators included in said system generates all suspected noise codes allocated to said each object at said receiving station of said each zone,

a reference signal generator is changed at an optional time interval,

correlative calculation is performed in order, and

the zone in which said each object exists is determined by comparing the magnitudes of said respective suspected noise signals with each other for each signal.