Communications: directive radio wave systems and devices (e.g. – Determining distance – With remote cooperating station
Patent
1987-07-20
1989-02-14
Tubbesing, T. H.
Communications: directive radio wave systems and devices (e.g.,
Determining distance
With remote cooperating station
342 42, 342127, G01S 1380, G01S 1384
Patent
active
048049611
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and to apparatus for measuring the distance between a transmitter-receiver unit and a transponder.
There are many instances where it is desirable to be able to determine with great accuracy the position of an object, e.g. a motor vehicle within a limited area, inter alia in order to be able to navigate the vehicle within said area. A common method of determining the position of an object in relation to a reference system is to measure the distance between the object and a number of reference points in the system. The position of the object can then be established quite readily from the distance values obtained, with the aid of trigonometrical functions. The accuracy to which the position of the vehicle is established is directly proportional to the accuracy at which the distances are determined. The present invention is particularly suited for measuring the distance between a transmitter-receiver unit, hereinafter called the master unit, and a transponder. In this respect the master unit may be located on a motor vehicle and a plurality of transponders placed at locations within the aforesaid area or around the demarcation lines thereof.
Two major distance measuring methods are known in the art. The first of these is based on the time taken for a pulse transmitted from the master unit to be reflected by the transponder and returned to the master unit, this method being the pulse radar method. The other of these two main methods is based on a phase comparison in the master unit between the signal transmitted to the transponder and the signal received therefrom, this method being the phase difference method.
The phase difference method is to be preferred in the case of limited ranges where a high degree of accuracy is required.
The present invention utilizes the phase difference method.
In accordance with the invention there is used in the simplest case a passive transponder. A passive transponder can only be used at short distances, since otherwise a master unit of high transmission power must be used.
For the purpose of increasing the range over which distances can be measured with the aid of limited transmitting powers, there is used a transponder which has its own transmitter oscillator. One known method of solving the problem concerning the phase relationship between transmitted and received signals is to phase-lock the transponder transmitter oscillator to the master unit oscillator, with the aid of a phase-locked loop. In order to avoid in the phase-locked loop feedback of the signal transmitted from the transponder, it is necessary to separate the transmission and reception of pulses in the transponder in time, so that they do not both occur at one and the same time. In order for a phase-locked loop to function satisfactorily, it is necessary to provide the transponder with a phase memory. Such a transponder is unavoidably highly complicated and very expensive. A system of this nature is also highly sensitive to disturbances.
In accordance with the invention there is provided a method for transferring information relating to the phase relationships in the transponder to the master unit, by means of a separate modulation process in which the signal transmitted by the transponder is separated from the signal transmitted by the master unit. This enables the master unit and the transponder to transmit and receive simultaneously therewith obviating the need for time division between transmission and receiving sequences in the system.
One particularly important advantage obtained with simultaneous transmission is that distances can be measured much more rapidly than is otherwise the case, which is highly beneficial under dynamic conditions, i.e. when the master unit is moving in relation to the transponder.
The aforementioned method according to the invention enables both active and passive transponders to be used for measuring distances by means of the phase difference method, instead of solely one reflector or of a complicated system with time division with regar
REFERENCES:
patent: 2907999 (1959-10-01), Wadley
patent: 3701151 (1972-10-01), Sato et al.
patent: 4063237 (1977-12-01), Nier et al.
patent: 4278977 (1981-07-01), Nossen
patent: 4307397 (1981-12-01), Holscher
patent: 4315260 (1982-02-01), Kupfer
patent: 4464662 (1984-08-01), Tomasi
patent: 4577150 (1986-03-01), Schreuder
patent: 4646092 (1987-02-01), Schreuder
patent: 4677441 (1987-06-01), Hofgen et al.
Hellner Mark
Stiftelsen Institutet for Mikrovagsteknik vid Tekniska Hogskolan
Tubbesing T. H.
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