WO2002033672A1

WO2002033672A1 - Assembly for locating objects

Info

Publication number: WO2002033672A1
Application number: PCT/NL2001/000768
Authority: WO
Inventors: Guustaaf Arthur Schwippert; Johannes Cornelis Hendrikus Van Leeuwen; Jacobus Cornelis Van Muiswinkel
Original assignee: Arthur's Consultancy V.O.F.; Adcon Rf Technology B.V.
Priority date: 2000-10-18
Filing date: 2001-10-18
Publication date: 2002-04-25
Also published as: NL1016423C2; AU2002214398A1

Abstract

The description refers to an assembly for locating objects, comprising a transmitter for transmitting a specific radio signal and a receiver to be attached to an object for receiving the transmitted radio signal and delivering a response signal in response thereto. The receiver is further provided with a return transmitter for transmitting a response radio signal, whilst the transmitter is further provided with a secondary receiver for receiving the response radio signal and generating a warning signal in response thereto. Preferably, the radio signal transmitted by the transmitter constitutes a microwave signal and preferably further is beam-shaped.

Description

Assembly for locating objects

The invention relates to an assembly for locating objects, comprising a transmitter for transmitting a specific radio signal and a receiver to be attached to an object for receiving the transmitted radio signal and delivering a response signal in response thereto.

An assembly of this type is known from US patent no. 4,476,469. The transmitter of this known assembly is capable of transmitting a large number of different specific (encoded) radio signals. Each specific radio signal is associated with a specific receiver and is recognized only by this specific receiver. When the specific radio signal reaches the associated receiver, the receiver will deliver a response signal in the form of a light signal or an acoustic signal. In this way, it is possible to locate an object on which the receiver is present .

An important drawback of this known assembly is the fact that the response signal in the form of a light signal or acoustic signal that is produced by the receiver can be blocked by objects which are present between the receiver and a user of the assembly (who is holding the transmitter) , so that the receiver is hidden from detection by the user to a greater or lesser extent. If the receiver that is fixed to an object is e.g. present in a closet, a light signal cannot be seen and an acoustic signal can hardly be heard, if at all.

It is an object of the present invention to eliminate the aforesaid drawbacks in a simple yet effective manner .

In order to accomplish that objective, the assembly according to the invention is characterized in that the receiver further comprises a return transmitter for transmitting a response radio signal, whilst the transmitter is furthermore provided with a secondary receiver for receiving the response radio signal and generating a warning signal in response thereto.

When the assembly according to the invention is used, a response signal in the form of a response radio signal being delivered by a specific receiver will reach the secondary receiver of the transmitter and lead to an alarm signal being activated. The specific receiver can be considered as a primary receiver in that case. From said warning signal, a user of the assembly can deduce that the object to be located is within the range of the transmitter. Objects that are present between the primary receiver and the transmitter have hardly any influence, if at all, on the detection by the user of the response signal being delivered by the receiver. In fact, it can be posed that the prior art response signal from the receiver (which in fact functions as a warning signal) has been replaced in the present invention by a transmitter-generated response signal (viz. the warning signal) . The nature of the receiver response signal has changed; it no longer functions as a warning signal that can be detected by the user, but as a response radio signal that can be detected by the transmitter (namely by the secondary receiver thereof) but not by the user.

It is important for the assembly to have a long life span. A long life span means that the energy consumption, in particular of the receiver, must be as low as possible. In order to help achieve that objective, it is proposed that the receiving part of the receiver be of a substantially passive type, whilst the return transmitter of the receiver is battery-powered. A passive-type receiving part means that in principle said receiving part consumes next to no energy. Only when the receiving part responds to a specific radio signal will the other part of the receiver, in particular the return transmitter thereof, be activated, which requires energy. As long as the receiver only receives radio signals that are not intended for the receiver in question (i.e. when it is attempted to locate another primary receiver with the transmitter) , it will not consume any energy. In

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secondary receiver of the transmitter will generate the warning signal. This enables quick and easy determination by a user of the direction in which an object to be located can be found. In order to further simplify the determination of said direction, the transmitter may be arranged for transmitting a light beam that falls substantially within the beam-shaped radio signal. The light beam, possibly in combination with a point of light projected by a laser, constitutes a visual indication of the direction in which a located receiver (object) can be found.

With the assembly according to the invention, the receiver can be fixed to an object in various ways. A few non-limitative examples are adhering the receiver to an object or connecting it thereto in the form of a key ring. Furthermore, the transmitter is preferably provided with a display. Various locating data can be displayed thereon. Thus, the designation of an object to be located and its specific receiver can be displayed, or a visual warning signal can be displayed in the case of a successful locating attempt.

The transmitter and/or the user may furthermore be provided with security and/or initialisation facilities. The term security facilities in particular refers to facilities that prevent unauthorized use of the assembly. Thus, it may be necessary to input a PIN code. The receivers may comprise security facilities such that they can only be located by means of a specific transmitter.

The initialisation facilities may be intended, amongst other things, for attuning a new receiver to a specific transmitter when it is first put into service. In that case the receiver is presented to the transmitter, as it were, and for example provided with a designation.

The invention furthermore relates to a transmitter for use in an assembly according to the invention, as well as to a receiver for use in an assembly according to the invention. Such a receiver can also be referred to as a transponder. The invention will now be explained in more detail with reference to the drawing.

Fig. 1 schematically shows an assembly according to the invention; Fig. 2 is a block diagram of a transmitter according to the invention; and

Figs . 3 and 4 are block diagrams of a receiver according to the invention.

In Fig. 1 there is shown an assembly according to the invention for locating objects. The assembly comprises a transmitter 1 for transmitting a specific radio signal and, in the illustrated embodiment, a number of primary receivers (or transponders) 2, 3, 4 and 5 for receiving the transmitted radio signal, which receivers are to be fixed to various objects.

The radio signal 6 transmitted by the transmitter 1 is beam-shaped and preferably consists of a microwave signal having a frequency in the 2.4 GHz band.

As is shown in Fig. 1, the transmitter 1 is provided with a keypad 7 and a display 8 in the illustrated embodiment .

The transmitter 1 will now be explained in more detail with reference to Fig. 2. A microprocessor 9 is in communication with the display 8 and the keypad 7 on the one hand and with a microwave transmitter 10 provided with a transmitting antenna (e.g. a parabolic antenna or a Yagi antenna) and a secondary receiver 11 provided with a receiving antenna on the other hand. The microprocessor 9 is powered by a power supply 12, e.g. one or more batteries. The receivers 2-5 will now be explained in more detail with reference to Fig. 3. A processing unit 13 is in communication with a receiving part 14 fitted with a receiving antenna and a return transmitter 15 fitted with a transmitting antenna. The return transmitter 15 and the transmitting antenna are adapted for transmitting an omnidirectional (i.e. not beam-shaped) response radio signal having a frequency which is preferably lower than the frequency of the radio signal, in the above example of a radio signal in the 2.4 GHz band it will e.g. be in the 0.9 GHz band. A power supply 16 supplies energy to the processing unit 13.

When a specific transponder or receiver 2-5 is put into use, it is presented to transmitter 1 by means of an initialisation routine and given a unique code. Furthermore, a designation that the user can recognize can be linked to the receiver, for example the designation of the object associated with the receiver in question. This unique code is stored in the transmitter 1, so that a specific radio signal 6 can be transmitted by operating the keypad 7, which signal will only activate this specific receiver 2-5.

When an object is to be located by means of the assembly according to the invention, the following procedure is followed. In the first place, it is determined which receiver or transponder is associated with the object in question. Object designations (and the associated receivers) can be stored in a memory of the transmitter 1. An example of such a designation is "key" . The specific encoded radio signal associated with the specific receiver 2-5 is transmitted by pressing a respective key on the keypad of ^■ the transmitter 1. The term specific encoded radio signal is understood to mean a radio signal that is encoded in such a manner that only the specifically designated receiver or transponder will respond thereto.

If the key associated with "key" is pressed in the above example, the radio signal associated with the receiver that is attached to the key will be transmitted. It is also possible in such a case for the word "key" to be displayed in the display 8 of the transmitter 1.

The user picks up the receiver 1 and swings it back and forth whilst the radio signal 6 is being transmitted. If the radio signal beam covers the specific receiver being sought, said receiver will respond thereto by returning to the transmitter a response signal in the form of a response radio signal. In Fig. 1, the specific receiver is e.g. receiver 2. The receiver 3, which is also located within the range of the beam 6, does not respond, because the radio signal being transmitted does not correspond to the specific code for this receiver 3. The receivers 4 and 5 are located outside the range covered by the beam and will not respond, therefore, even if the code of the radio signal were to correspond with the code of said receivers .

Referring to Fig. 2, after the keypad 7 has been operated, the display 8 will be activated by the microprocessor 9 on the one hand and the respective specific encoded radio signal will be transmitted by means of the microwave transmitter 10. A correct specific signal received by the receiving part 14 (see Fig. 3) of the receiver will be converted by the processing unit 13 into a radio response signal, which will be transmitted by the return transmitter 15 of the receiver. Said response radio signal will be received by the secondary receiver 11 of the transmitter and converted into a warning signal under the control of the microprocessor 9.

Said warning signal may be a representation on the display 8 or a different type of signal, such as an acoustic signal or a light signal. It is also conceivable for the transmitter to deliver a designation signal during the transmission of the radio signal 6, for example a light signal and/or an acoustic signal, and to change the intensity or the frequency of said designation signal when the secondary receiver 11 of the transmitter 1 receives a radio signal from the receiver.

The receiving part 14 of the receiver 2-5 can be a passive-type receiver and thus be excited by the radio signal 6 it receives; basically, however, it will not consume any energy itself. The processing unit 13 will not respond until the received radio signal 6 corresponds to the specific code of the receiver and energy will be received from the power supply 16. The energy consumption of the receivers 2-5 can be minimized this way, so that lost objects can be located even after a prolonged period.

A more detailed block diagram of the receiving part 14 and the processing unit 13 is shown in Fig. 4. The figure shows that the receiving part 14 comprises an antenna 17, which is connected to a band filter 18. Said band filter 18 furthermore comprises a circuit, by means of which the input impedance of the band filter 18 is adapted to the output impedance of the antenna 17, which is done in order to supply the strongest possible signal to the band filter 18.

The band filter 18 is connected to a detector, e.g. a passive diode detector 19, which is in turn connected to a pre-amplifier 20.

The band filter 18 ensures that the receiver will not be activated unnecessarily by signals in a different frequency band, whilst the diode detector 19 converts the high-frequency energy that is being passed into a DC voltage. Since said voltage is frequently insufficient for driving the digital logic in the processing unit 13, the (microwave) pre-amplifier 20 is provided.

The pre-amplifier 20 is connected to a monostable multivibrator 21 and to an (data) input of the processing unit 13. The use of a monostable multivibrator makes it possible to derive clock information from the signal being presented. The aforesaid digital logic will remain clockless as long as said logic is not activated and consequently it will not consume any energy.

The clock that drives the circuit for transmitting the response radio signal is not started until the logic has determined that the signal is intended for the receiver in question.

Important advantages of this receiver are its compact construction, which enables its use in files, for example, and its long life due to its (very) low energy consumption.

The microprocessor 9 or the processing unit 13 may comprise circuits which require the inputting of personal codes before the parts of the assembly according to the invention can operate. Thus, improper use of the assembly according to the invention is prevented. Furthermore, it is possible to link specific receivers 2-5 to a specific transmitter 1 in this way, so that receivers cannot respond to another transmitter 1. Thus, improper use of the assembly according to the invention is prevented as well.

The assembly according to the invention enables easy location of objects. By swinging the transmitter 1 back and forth, the radio signal beam 6 will cover a pre-selected search area. When the radio signal beam 6 covers (passes) a specific receiver, the transmitter 1 will receive a response radio signal, which is an indication that the object being searched is located within the range of the beam 6. The invention is not limited to the above-described embodiment, which can be varied in many ways within the scope of the invention as defined in the claims .

Claims

1. An assembly for locating objects, comprising a transmitter for transmitting a specific radio signal and a receiver to be attached to an object for receiving the transmitted radio signal and delivering a response signal in response thereto, characterized in that the receiver further comprises a return transmitter for transmitting a response radio signal, whilst the transmitter is furthermore provided with a secondary receiver for receiving the response radio signal and generating a warning signal in response thereto.

2. An assembly according to claim 1, wherein the receiving part of the receiver is of a substantially passive type, whilst the return transmitter of the receiver is battery-powered.

3. An assembly according to claim 2, wherein the return transmitter is not activated until the received radio signal corresponds to a specific code of the receiver.

4. An assembly according to claim 3, wherein the receiver comprises a circuit which is arranged for deriving clock information from said radio signal and using said information for processing said radio signal.

5. An assembly according to any one of the preceding claims, wherein said signal has a frequency in the 2.4 GHz band.

6. An assembly according to any one of the preceding claims, wherein the frequency of the response radio signal is lower than the frequency of the radio signal.

7. An assembly according to any one of the preceding claims, wherein the transmitter comprises means for delivering an indication signal, e.g. a light signal and/or an acoustic signal, upon transmission of the radio signal.

8. An assembly according to claim 7, wherein the indication signal undergoes a change, such as an intensity change or a frequency change, upon receipt of a return radio signal by the secondary receiver of the transmitter.

9. An assembly according to any one of the preceding claims, wherein the transmitter is arranged for transmitting a beam-shaped radio signal.

10. An assembly according to claim 9, wherein the transmitter is arranged for transmitting a light beam that falls substantially within the beam-shaped radio signal.

11. An assembly according to any one of the preceding claims, wherein the transmitter and/or the user are provided with security and/or initialisation facilities.

12. A receiver for use in an assembly according to any one of the preceding claims .