Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-12-28
2003-03-18
Chin, Vivian (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S443000
Reexamination Certificate
active
06535744
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a system for the spatial allocation of at least one transponder to the cells of a detection area. More particularly, the invention relates to a system where the cells differ from one another by changeable or permanently different properties of an electromagnetic field.
2. The Prior Art
Transponders are mobile electronic switching circuits, which serve primarily for the identification of persons, animals, or objects, and allow for data exchange with a base station without contact. Transponders are also used to track moving objects for logistical purposes or for securing items of value.
With the application situations known hitherto, the spatial allocation of the transponder was effected by way of identification by means of a base station, in the range of which the transponder was located. This arrangement was restricted to the more immediate vicinity of an area created by an antenna of the base station. There was a need for spatial identification also to be achieved in a larger area than the range of a base station antenna.
In principle, the method of determining the position of mobile receiver devices is known. Thus, for example, the GSM mobile radio network is subdivided into radio cells, to which fixed-position radio stations are allocated. The mobile telephone receives several transmitting stations simultaneously in time slots and on different reception frequencies. The telephone then creates a connection with a particular radio station, or changes to another radio station with which the best possible radio transmission is guaranteed.
A mobile telephone also monitors fixed signaling zones for the purpose of signaling incoming calls. A message is passed to the network as soon as the mobile telephone switches to an adjacent signaling zone. In this situation, however, the spatial position determination is of subsidiary importance. More important is the issue of the best possible quality of the radio transmission. This means that another allocation might be effected due to screening or reflexions than would accord with the geographical position of the locations of the fixed-position radio stations.
Another type of position determination is effected with the GPS system. In this case, the signal from a number of fixed-position satellites in orbit is received by means of a GPS receiver, and the position of the receiver is determined from the difference in propagation times between the signals received.
An animal control system is known from WO 95/28691 A1. This system comprises a transmitter, which creates an electromagnetic field in an area from which the animal is to be kept away. The animal, in the drawing a dachshund, wears a collar with a transponder, an audible alarm which can be activated by the transponder, and an electric shock device. When the animal enters the electromagnetic field, this is detected by the transponder, which compares it with two threshold values. If an initial threshold value is exceeded, the audible alarm will first be activated, in order to warn the animal. If the animal ignores the audible alarm, and goes further, which is typical of dachshunds, the electric shock device will be activated when the second threshold value is exceeded. This should cause the animal to retrace its steps with alacrity. No location determination is provided for with this disclosure.
SUMMARY OF THE INVENTION
The invention is based on the objective of allowing for an unambiguous allocation of each transponder to cells of the detection area, on the basis of data transfer between a base station and at least one transponder.
This objective is attained in accordance with the invention with a system for the spatial allocation of at least one transponder to cells of a detection area, the cells of which differ from one another by changeable or permanently different properties of an electromagnetic field. The transponder receives the properties of the electromagnetic fields of the cells at its position individually, selectively, or as resultants. The properties are evaluated and the allocation to the cells is effected automatically in accordance with the characteristics of the individual electromagnetic fields received, the ratio of the proportions of the electromagnetic fields received selectively or as resultants, or the proportion predominant in the field strength of the electromagnetic fields received selectively or as resultants. Further developments and advantageous embodiments of the invention are discussed below.
For spatial allocation, it is sufficient if at least two cells are provided, which have electromagnetic field properties capable of being changed or permanently different. Capable of being changed in this context may mean that the properties are constantly changing, or that the properties are only different during a limited period of time, which serves, for example, for the detection process. The transponder evaluates the properties of the fields received. With non-overlapping fields, these are received and evaluated one after another. As long as the transponder is located in one of the fields, the different properties of the fields provide at least a rough indication of the position, in that the transponder remains in the cell which pertains to this field. It is also possible to derive a direction of movement from the sequence of fields into which the transponder has entered. Because of the constant or temporary difference between the fields, when the transponder enters a field from outside it is also capable of making an unambiguous allocation as to which field it has entered.
In the event of overlapping fields, a number of different situations may arise. If the fields have different frequencies, and if the transponder is equipped with several receivers, it is possible for several fields to be evaluated simultaneously. If the transponder is equipped with one receiver, it is likewise possible to monitor several fields if the fields are switched on or off respectively in the time multiplex, or if the frequency of the receiver is switched over.
It is also possible for the fields to be superimposed with the same or almost the same frequency, and therefore for the resultant of the superimposed fields to be evaluated by the receiver. The allocation of the transponder to the individual cells is then effected by the fact that the properties are compared between several selectively received fields. The allocation is determined in accordance with either the fraction which predominates in field strength, or from the proportions between the fractions. With a resultant field, the allocation is made on the basis of which fractions of the resultant fields predominate and are therefore capable of being reliably evaluated.
An evaluation becomes particularly simple and unambiguous if operations are being conducted with fields of the same frequency, and if the phase of the fields of adjacent cells differ by 180 degrees. The properties of the fields can in this case be varied to such a degree that, for the purpose of a position determination, for the duration of a measuring period the phase angle of the fields of some cells is switched over cyclically between 0 degrees and 180 degrees, while the phase angle of the fields of the other adjacent cells is retained. The transponder can then easily determine which cell it is located in, by evaluating the phases within the measuring period.
If the characteristics of the fields of the cells differ markedly, at least a rough indicative allocation is possible as to which cell the transponder is located in. A precise position would, by contrast, also make it necessary for the conditions of the field strengths of the individual fields to be evaluated.
Because the transponders carry out the allocation independently, in the simplest case no dialogue is required between the transponder and the base station. Rather, the presence of the electromagnetic fields is sufficient. As a result, it is also possible for several transponders, located simultaneously in the detection a
Merk Holger
Stobbe Anatoli
Chin Vivian
Collard & Roe P.C.
Nguyen Tu X
Stobbe Anatoli
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