Communications: directive radio wave systems and devices (e.g. – Directive – Utilizing correlation techniques
Reexamination Certificate
1998-07-28
2001-05-08
Issing, Gregory C. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Utilizing correlation techniques
C342S174000
Reexamination Certificate
active
06229483
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 9702818-7 filed in Sweden on Jul. 29, 1997; the entire content of which is hereby incorporated by reference.
TECHNICAL FIELD
The present invention relates to a device and a method at antenna calibration; in particular the invention relates to the calibration of group antenna systems.
BACKGROUND OF THE INVENTION
Many technical applications comprise some form of antenna function, in which signals are received or transmitted via air. Examples of such applications are radio devices, TV sets, mobile telephony systems and radar systems.
The demands of directional function of an antenna varies with the application. A radio device shall be able to receive signals from different radio stations independent of where it is placed and therefore, an antenna of the radio device shall be sensitive in all directions in the horizontal plane. However, a TV receiver shall only be sensitive for signals coming from the nearest TV antenna. An antenna of a TV receiver has to be arranged so it is sensitive in particular for signals coming from the nearest TV antenna. Thus, an antenna of a TV receiver has to be arranged so it is sensitive in particular for signals coming from a particular direction, and signals coming from other directions have to be reduced as much as possible. An antenna in a base station in a mobile telephony system shall be able to receive signals from mobile telephones independently of where they are situated. When the base station shall transmit to one of the mobile telephones it can be desirable to transmit signals only in one direction to the particular mobile telephone, to be able to save power and not to interfere with other radio communication.
A type of antenna which can have directional function is the so called group antenna. A group antenna comprises a number of radiation elements, co-operating to give desirable radiation characteristic. The radiation elements consist normally of dipoles, horns or micro-strip elements (so called patches). Furthermore, an active group antenna comprises a number of transmitters, via a distribution network receiving an input signal and transmitting output signals. The output signals are employed to feed the radiation elements. The distribution network together with the transmitters constitutes a lobe-forming network. The group antenna is constructed so the output signals transfer to the radiation elements directly or via some form of external lobe-forming network, e.g. a Butler matrix or a Blass matrix. Controlling of the directional function of a group antenna—an antenna diagram—is obtained by controlling mutually phase-shifting and amplification of the transmitters. The group antenna can of course also be used for reception. Then, the group antenna comprises a number of receivers, wherein the group antenna is so constructed that signals received by the radiation elements are transferred to the receivers, e.g. via the external lobe-forming network.
To be able to achieve a particular antenna diagram of a group antenna with relatively good accuracy it is required that the amplification of the transmitters and in particular the phase-shifting can be well controlled. To be able to obtain this the transmitters must be calibrated. Prior art discloses a large number of proposals of constructions and methods for calibration of group antennas. Often the calibration is done in calibration sets where special calibration signals are employed. For instance, U.S. Pat. No. 5,063,529 describes how a group antenna can be calibrated for reception employing special calibration signals.
A disadvantage with calibrating during calibration sets by employing special calibration signals is that the normal operation of the group antenna must be interrupted during the calibration. For instance in a mobile telephone system this causes that part of the time cannot be used for the normal communication, of course implying decreased incomes for an operator.
DISCLOSURE OF THE INVENTION
The present invention solves the problem how a group antenna system shall be able to be calibrated so a with time varying desired antenna diagram at transmission is obtained, without disruption of the normal operation of the group antenna system or influence in some other way of the calibration.
Above disclosed problems are generally solved according to the following. The group antenna system comprises a number of transmitters and a number of radiation elements. An input signal, which can be modulated for normal radio traffic, is applied to the transmitters, and thereby the transmitters transmit output signals. The output signals are transferred to the radiation elements for feeding the radiation elements. Mutual phase-shifting and amplification of the transmitters are controlled for the desired antenna diagram at transmission to be obtained. Hereby, phase-shifting and amplification for each transmitter shall correspond to a requested phase-shifting and a requested amplification for each transmitter. However, imperfections—error deviations—of the transmitters imply that this is not always fulfilled. According to the invention it is provided that the normal traffic, i.e., the input signal and the output signals, is employed for obtaining information about these error deviations. Therefore, according to the invention error signals are generated corresponding to the error deviations of the transmitters depending on the input signal, the output signals, the requested phase-shifts and the requested amplifications. The error signals are employed for correcting the control of the transmitters for the error deviations.
Thus, the object of the invention is to employ normal traffic for obtaining information about error deviations of the transmitters and by employing this information correct the controlling of the transmitters for error deviations, wherein the invention comprises devices and methods for obtaining this.
The disclosed problem above is solved more specifically according to the following. The group antenna system comprises means for generating a sum signal corresponding to a sum of the output signals from the transmitters. The means for generating the sum signal can for instance consist of an adder connected to the transmitters so it thereby receives signals corresponding to the output signals. The adder sums the received signals, wherein the sum signal is obtained. Furthermore, the group antenna system comprises means for generating the error signals from the input signal, the sum signal, the requested phase-shifts and the requested amplifications. The sum signal implies that the error signals for all transmitters can be generated simultaneously. Preferably, the group antenna system comprises filters for generating correction signals by a noise-reducing filtering of the error signals. The correction signals are employed when the control of the transmitters is corrected for the error signals.
A major advantage of the invention is that the group antenna can be employed in normal operation during calibration. Yet another advantage is that the calibration can be performed continuously so that the group antenna is always well calibrated.
The invention will now be further described in preferred embodiments and with reference to accompanying drawings.
REFERENCES:
patent: 4673939 (1987-06-01), Forrest
patent: 5063529 (1991-11-01), Chapoton
patent: 5412414 (1995-05-01), Ast et al.
patent: 5838674 (1998-11-01), Forssen et al.
patent: 0 762 541 (1996-03-01), None
patent: WO 95/34103 (1995-12-01), None
Burns Doane Swecker & Mathis L.L.P.
Issing Gregory C.
Telefonaktiebolaget LM Ericsson (publ)
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