Telecommunications – Transmitter – With feedback of modulated output signal
Reexamination Certificate
1998-06-12
2001-12-25
Legree, Tracy (Department: 2681)
Telecommunications
Transmitter
With feedback of modulated output signal
C455S115200, C455S067150, C455S234100
Reexamination Certificate
active
06334050
ABSTRACT:
FIELD OF INVENTION
The present invention relates to an arrangement and to a method for controlling the output power of radio frequency signals sent from a radio unit in a radio base station (RBS) and the input power of radio frequency signals received by the radio unit. The arrangement is particularly designed to control the output power from radio base stations that include remote amplifier stages.
BACKGROUND OF THE INVENTION
The majority of countries have mobile radio systems. In order to enable the system operators to satisfy capacity expectations with the frequency bands allotted to the Operator, the mobile radio system is divided into geographical areas that are called cells. The cells may have a radio base station placed in the centre of the cell, wherein a mobile terminal communicates with other mobile terminals and with a land-based telephone network through said radio base station. The cells are designated omnicells in this latter case. One and the same radio base station can cover several cells with the aid of directional antennas, these cells then being designated sector cells.
Radio channels that are allotted to the mobile radio system are shared by those cells that are included in the system. A set of mutually the same radio channels can be used in several cells. Cells that use the same radio channels are spaced sufficiently apart so as not to interfere with one another. This demands careful cell planning.
First-time planning of a cell involves choosing the respective positions of radio base stations and antennas, among other things. The power at which the antennas are permitted to transmit is governed by the positions of the radio base stations and the antennas, which in turn governs the area covered by the base stations. Improvements in capacity, for instance, necessitates the cells being made smaller and therewith the maximum permitted output power to be reduced.
In order to plan a cell accurately and, at the same time, provide the highest possible output power without exceeding a permitted power level, it is necessary to control the power output of the antenna both accurately and quickly.
EP 0684707 A1 teaches an arrangement and a method for controlling the transmission power of radio frequency signals. A power-sensitive element placed within an antenna element enables the transmission power of radio frequency signals to be monitored. The signal power measured by the power sensitive element is converted analogue/digital and delivered to a microprocessor. The microprocessor generates an output signal in relation to said input signal, said output signal controlling a variable attenuator included in the transmitter chain of the arrangement and thus influencing the output power of radio frequency signals by virtue of different attenuation levels of the attenuator. The power control is carried out with each time slot and the power of a transmitted radio frequency signal is not changed during a time slot but is adjusted between time slots.
EP 0695031 A2 teaches a mobile communications arrangement that includes a control circuit for adjusting, or setting, the output power of radio frequency signals. A reference voltage generator generates a reference voltage that is compared with a detected voltage by means of a comparator. The voltage detected corresponds to a power of a radio frequency signal to be transmitted. The detected voltage is obtained by measuring the power of the radio frequency signal with an output power sensor and converting the measured power to a corresponding detected voltage with a detector. The reference voltage corresponds to a desired output power of the radio frequency signal. The comparator generates a difference signal, i.e. a signal corresponding to the difference between the measured power and the reference power, which controls a power amplifier in the transmitter link of the arrangement. The control circuit sets the amplification factor of the power amplifier so that the output power of the radio frequency signal will correspond to the desired output power. Generated reference voltages derive from measurements of received radio frequency signals and the reference voltages are thus dependent on the received radio frequency signals.
Described in JP 07250020 A is a regulator intended for controlling output powers of radio frequency signals that shall be transmitted from a portable telephone or like apparatus. According to this solution, when measuring the power at which radio frequency signals are transmitted, there is used an antenna which receives a part of those radio frequency signals that are sent by the portable telephone. Received radio frequency signals are detected and compared with a d.c. voltage in a comparator and the difference indicating signal generated thereby controls indirectly a variable amplifier in the transmitter link of the portable telephone.
SUMMARY OF THE INVENTION
The present invention addresses the problem of how earlier determined amplification factors (gain) can be set with good tolerance for transmitters and receivers in a radio unit irrespective of ambient temperature, even when a long feeder is used between a transmitter-and-receiver unit and a remote amplifier stage.
Another problem solved by the present invention is one of guaranteeing a maximum output power of radio frequency signals sent from the radio unit.
Another problem addressed by the present invention is one of eliminating the need of manually trimming maximum transmitted power from an antenna arranged at the radio unit, and manually trimming the amplification of the receiver link in the radio unit upon installation.
Thus, an object of the present invention is to set earlier specified amplification factors (gain) with good tolerance for the transmitter and the receiver of the radio unit.
Another object of the present invention is to guarantee a maximum output power of radio frequency signals sent from the radio unit.
Still another object of the invention is to eliminate the need of trimming-in the radio unit manually upon installation.
The above problems are solved in accordance with the present invention, by providing a power sensing means in the vicinity of an antenna at a radio base station. The power sensing means converts transmitted radio frequency signals to a detector voltage corresponding to the radio signal. The detector voltage is compared with a reference voltage in a difference amplifier. The reference voltage is generated in the radio base station and corresponds to a desired maximum output power of transmitted radio frequency signals. The difference amplifier generates a difference signal which is used to set the amplification of a first variable amplifier in the transmitter, link in one embodiment of the invention, and also of a second variable amplifier in the receiver link.
One advantage afforded by the present invention is that it compensates automatically for the temperature dependency of all components in the transmitter link with the exception of the difference amplifier.
Another advantage is that the amplification of the transmitter and of the receiver (gain) can be set simultaneously with one and the same control circuit.
A further advantage afforded by the present invention is that the amplification in the transmitter link and in the receiver link is independent of the attenuation in a feeder provided in a radio base station between a transmitter-and-receiver unit and a remote amplification stage.
Yet another advantage afforded by the invention is that it eliminates the need to trim the output power manually when installing the radio base station.
The present invention will now be described in more detail with reference to preferred embodiments thereof and also with reference to the accompanying drawings.
REFERENCES:
patent: 5335369 (1994-08-01), Aisaka
patent: 5459426 (1995-10-01), Hori
patent: 5524287 (1996-06-01), Yokoya et al.
patent: 5566363 (1996-10-01), Senda
patent: 5574993 (1996-11-01), Kobayashi et al.
patent: 5603106 (1997-02-01), Toda
patent: 5715527 (1998-02-01), Horii et al.
patent: 5805979 (1998-09-01), Mi
Burns Doane Swecker & Mathis L.L.P.
Legree Tracy
Telefonaktiebolaget LM Ericsson (publ)
LandOfFree
Arrangement and a method relating to a radio unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Arrangement and a method relating to a radio unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Arrangement and a method relating to a radio unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2590091