Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1998-11-19
2001-02-27
Nguyen, Lee (Department: 2746)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S013300, C455S101000, C455S123000, C455S562100, C342S359000, C342S372000, C342S434000, C342S445000
Reexamination Certificate
active
06195559
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication system. Such a communication system can be a cellular or cordless telephony system, or any other suitable system. The system can be a terrestrial and/or satellite cellular mobile radio system in which the one radio station can be a radio base station in a terrestrial network or a mobile terminal, and the other radio station can be a satellite. The system can be an analog or digital system. In the event of a digital system, the system can be a so-called FD/TDMA-system (Frequency Division/Time Division Multiple Access), a CDMA-system (Code Division Multiple Access), or a mixed FD/TDMA- and CDMA-system, or any other suitable system.
The present invention further relates to a primary and a secondary radio station and a radio communication method for use in such a communication system.
2. Description of the Related Art
A communication system of the above kind is known from the handbook “Mobile Antenna Systems Handbook”, K. Fujimoto et al., Artech House, Inc., 1994, pp. 436-451. The known system is a land mobile satellite communications system in which the primary radio stations are satellites and the secondary radio stations are mobile radio station in a vehicle. The secondary radio stations comprise a phased-array antenna as a controllable antenna structure. At pages 438-441 a satellite tracking method is described. The phased-array antenna is controlled on the basis of sensing information acquired by an optical-fibre gyro and a geomagnetic sensor, the sensing information being used in an open-loop control method. As is described on page 441, the geomagnetic sensor is used for sensing an absolute direction to calibrate the cumulative angular error of the optical-fibre gyro which can only sense relative directional variations. Optical-fibre gyros are relatively expensive or to slow to follow quick movements. Furthermore, measuring the absolute direction of the earth magnetic field is subject to static and dynamic magnetic field disturbances caused by the vehicle passing large buildings containing metal, inter alia. Also, since the earth magnetic field varies in a compicated way with geograpic position, sophisticated correction methods are needed, often requiring expensive additional sensors. It is at least difficult or even not feasible to implement the known method in a portable radio station such as a cellular radio handset which can be freely and rapidly oriented in different positions with respect to a fixed coordinate system.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a communication system of the above kind having a robust and cheap control mechanism for directing radiation of a controllable antenna structure in a freely orientable secondary radio station in a direction providing optimum conditions for communication.
To this end the communication system according to the present invention comprises a portable radio station which can be freely oriented with respect to a fixed coordinate system, the portable radio station comprising a controllable antenna structure, a three dimensional geomagnetic sensor for three-dimensionally sensing a local magnetic field, control means for controlling the controllable antenna structure on the basis of sensing information obtained with the three dimensional sensor, such that, after initial adjustment of the controllable antenna structure to a predetermined direction, the antenna structure substantially retains its radiation directed in the predetermined direction, irrespective of subsequent orientation of the portable radio station. The present invention is based upon the insight that, after initial adjustement of the controllable antenna structure in a defined direction such as an orientation direction in a line from the secondary station to a primary station, at least in principle, steering of the controllable antenna structure purely on the basis of information about the relative direction of the local magnetic field at the location of the secondary radio station gives a very robust control. It is realised that such a control, in principle, is independent of the geographical position of the secondary radio station and can be made insensitive to static magnetic disturbances superimposed on the local earth magnetic field. Preferably, the three dimensional sensor is a sensor using three, preferably orthogonal, AMR (Anisotropic Magneto Resistive) magnetic field sensor elements which are cheap and have a very fast real time response characteristic. If all sensor elements should be mounted on a single substrate, one of the AMR-sensor-elements could be replaced by a Hall-effect sensor element. Such a type of a three dimensional sensor, and electronics to process sensing information, is described in the still unpublished European patent application of the same Applicant, European Application No. 97202104.2, filed Jul. 8, 1997, the contents of this patent application herewith being incorporated by refrence in the present patent application. From three output signals of the three-dimensional sensor, the magnitude of the total field strength can be determined. Herewith, it can be checked whether, due to a strong local dynamic disturbance, there is a sudden change in the local magnetic field. In such an event, an appropriate correction and possibly re-calibration procedure could be initiated as used for the initial adjustment. Because of the ability of a secondary radio station to directionally radiate to radio station in a network, in principle, once a radio link has been established, either in idle mode or in call mode, without using substantial exchange of information via such a link, a considerable power consumption reduection is achieved in the secondary radio station. Particularly for a portable communication device this means longer standby time and/or longer connection time.
Further embodiments are claimed in the dependent claims. The further embodiments are mainly directed to the solving of the remaining problem how to initially adjust the controllable antenna structure to the predetermined direction, e.g. from a mobile station in a cellular radio system to a radio base station, which can be a terrestrial station or a satellite station.
In a number of dependent claims measures are given in the system to obtain information allowing initial adjustment of the controllable antenna structure. At the primary radio station magnetic field information at its own location and its surroundings can be stored in a data base in the form of a priori known data acquired by earth magnetic field measurements at various locations, or the primary radio station can also have a similar three-dimensional sensor which then measures an absolute earth magnetic field vector. The primary radio station transmits such reference information to secondary stations as of the present invention so that an initial alignment as regards the fixed coordinate system can be made in the secondary station.
In other dependent claims embodiments are given how to establish a pointer of orientation of a secondary station as regards a primary station. Once this pointer of orientation has been established, and the controllable antenna structure is controlled such that a main antenna lobe is directed into the direction of the primary station, the secondary station can transmit with a lower power because a directional antenna is then used instead of an omnidirectional antenna. In the event of an imminent loss of an established communication link or even a loss of the link, e.g., because the secondary radio station nters a radio shadow, the omnidirectional antenna could be used again to find a better link or to recover the link. In one embodiment, the omnidirectional antenna camps on a cell while the controllable antenna structure is used to scan different directions and carries out energy measurements in such directions to find the best link. When found, the controllable antenna structure takes over the link. In another embodiment, the secondary station tran
Lenssen Kars-Michiel H.
Rapeli Juha
Nguyen Lee
Nguyen Simon
U.S. Philips Corporation
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