APPARATUS FOR DETECTING FAILURE OF AN ANTENNA AMPLIFIER UNIT WITH A HOT STANDBY REDUNDANCY

Abstract: The invention relates to an apparatus for detecting failure of an antenna amplifier unit (1), replicated on the hot standby principle, in a receiving unit (2) positioned apart from an antenna (3), the receiving unit comprising power supply means (20) for supplying operating voltage to the antenna amplifier unit through an antenna cable (4). To transmit information on the failure of the amplifier to the receiving unit, the apparatus of the invention is characterized in that the antenna amplifier unit (1) comprises control means (10) responsive to a failure of an amplifier for disconnecting an amplifier (LNA1, LNA2) from the supply of operating voltage, and that the power supply means (20) are capable of detecting a change in power consumption resulting from the disconnection of the amplifier from the supply of operating voltage and thereby the failure of the amplifier (LNA1, LNA2).

Description: Apparatus for detecting failure of an antenna amplifier unit with a hot standby redundancy The invention relates to an apparatus for detecting failure of an antenna amplifier unit, replicated on the hot standby principle, in a receiving unit positioned apart from an antenna, the receiving unit comprising power supply means for supplying operating voltage to the antenna amplifier unit through an antenna cable. To improve the sensitivity of radio receivers, an antenna amplifier or preamplifier is often placed at the top of the antenna mast in close vicinity to the antenna, whereby a signal received by the antenna can be amplified before it is applied through an antenna cable to the primary receiver positioned at the foot of the mast or close to it. To increase the reliability and redundancy, the antenna amplifier is often replicated on the hot standby principle: both the amplifier in use and the amplifier in reserve assumes a full operating mode, so that when the amplifier in use fails, the signal can be passed immediately to the standby amplifier without inter¬ fering with the reception. The power source is usual- ly positioned in connection with the receiver at the foot of the mast and the operating voltage is supplied to the amplifier positioned in the mast through the antenna cable, so that the need for a separate power supply cable is avoided. A problem with such an arrangement is, however, that information concerning the failure of the amplifier positioned in the mast and the replacement of it with the other amplifier should be transmitted to the receiver in order to be able to start the required repair operations. One approach is to use an extra cable for the transmission of the alarm. This, however, is inconvenient if there are no provisions for extra cables. The need for an extra cable can be avoided by transmitting the alarm information in the form of a modulated signal through the antenna cable to the receiver. Among the disadvantages of this method are that it causes interferences and requires a complicated equipment with resulting costs. The object of the present invention is to provide an apparatus by means of which alarm informa¬ tion can be transmitted from the mast simply and advantageously without the need for separate cables. This is achieved by means of an apparatus of the type disclosed in ' the introduction, which according to the invention is characterized in that the antenna amplifier unit comprises control means responsive to a failure of an amplifier for dis¬ connecting the amplifier from the supply of operating voltage, and that the power supply means are capable of detecting a change in power consumption resulting from the disconnection of the amplifier from the supply of operating voltage and thereby the failure of the amplifier. In the following the invention will be described in greater detail by means of an exemplify¬ ing embodiment with reference to the attached figure, which is a block diagram of an apparatus according to the invention. The figure shows an antenna amplificer or pre- amplifier unit 1 positioned in close vicinity to a receiving antenna 3, e.g. in an antenna mast or some other place where the antenna is positioned, so as to amplify a radio-frequency signal received by the antenna 3 before the signal is applied through an antenna cable 4 to a receiving unit 2 positioned at a greater distance from the antenna, e.g. at the foot of the antenna mast or close to it. According to the requirements in each particular case, the receiving unit 2 may be of any type, such as a base station in a cellular mobile telephone system. The receiving unit 2 comprises a power source unit 20 for supplying operating voltage through a coaxial antenna cable 4 to the amplifier unit 1. Even though the power source unit 20 is considered to be a functional part of the receiving unit 2, it may be positioned in practice apart from the radio sections of the receiving unit 2. The amplifier unit 1 comprises a bandpass filter 10 for separating a desired frequency band from the signal fed by the antenna 3. To assure the reliability and redundancy of the amplifier unit, it is replicated on the hot standby principle. For this purpose the unit comprises at least two separate high-frequency amplifiers LNA1 and LNA2 of which one serves as an active amplifier through which the signal is passed, and the other is in reserve ready for operation, that is, in a hot standby mode. For the selection of the amplifier, the amplifier unit 1 comprises a change-over switch SI, which connects the output of the filter 10 to the input of the amplifier LNAl or LNA2, and a change-over switch S2 which connects, through a blocking capacitor Cl, the output of the amplifier LNAl or LNA2, respectively, to the output of the unit 1. The amplifier unit 1 further comprises a control unit 10 which is connected through a coil LI to the center wire of the coaxial antenna cable 4 for receiving operating voltage and for generating separate operating voltages Vccl and Vcc2 to be applied to the amplifiers LNAl and LNA2. The control unit 10 monitors the condition of the amplifiers LNAl and LNA2 by observing their power consumption by means of measuring circuits formed by resistors RI and R2 and differential amplifiers CNA1 and CNA2, respectively. The measuring circuits produce signals cdl and cd2 proportional to the power consumption of the amplifiers LNAl and LNA2, respectively. The signals are applied to the control unit 10, and when the control unit 10 detects, e.g. in the situation of the figure on the basis of the signal cdl, that the amplifier LNA 1 has a failure, it immediately changes the state of a switch control signal SC so that the switches SI and S2 switch the received signal to pass through the amplifier LNA2. In addition, the control unit 10 disconnects the amplifier LNAl from the supply of the operating voltage Vccl. If, in the situation of the figure, the failing amplifier is the amplifier LNA2, the control unit 10 only cuts off the operating voltage Vcc2. The power control unit 20 comprises a voltage source and control unit 21 which is connected through a coil L2 to the center wire of the antenna cable 4 for supplying the operating voltage +12V to the amplifier unit 1. The unit 21 monitors the power consumption of the amplifier unit 1 and when it detects a reduction in the power consumption as a result of an interruption in the supply of one of the operating voltages Vccl and Vcc2, indicating failure of one amplifier, it generates an alarm signal ALARM for the control system of the receiving unit 2 or the operating staff. The measuring of the power consump¬ tion and the generation of the alarm signal can be realized in many ways obvious to one skilled in the art. The figure and the description related to it are only intended to illustrate the present inven¬ tion. In its details, the apparatus of the invention may vary within the scope of the attached claims.

Claims: Claim: Apparatus for detecting failure of an antenna amplifier unit (1), replicated on the hot standby principle, in a receiving unit ( 2 ) positioned apart from an antenna (3), the receiving unit comprising power supply means (20) for supplying operating voltage to the antenna amplifier unit through an antenna cable (4), c h a r a c t e r i z e d in that the antenna amplifier unit (1) comprises control means (10) responsive to a failure of an amplifier for disconnecting the amplifier (LNAl, LNA2) from the supply of operating voltage, and that the power supply means (20) are capable of detecting a change in power consumption resulting from the disconnection of the amplifier from the supply of operating voltage and thereby the failure of the amplifier (LNAl, LNA2).

Inventors: SAVUSALO JUHA, SAVUSALO, JUHA
Applicants: TELENOKIA OY
Application year: 1991
Main classification: H04B1
IPC codes: H03F1, H04B1