ARRANGEMENT AND METHOD IN RELATION TO A RADIO UNIT FIELD OF THE INVENTION The present invention relates to an arrangement and a method for controlling the output power of radiofrequency signals sent from a radio unit in a radio base station (RBS) and the input power of radiofrequency signals received by the radio unit. The array is specially designed to control the output power of radio base stations that include remote amplifier stages. BACKGROUND OF THE INVENTION Most countries have mobile radio systems. In order to allow system operators to meet capacity expectations with the frequency bands assigned 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 center of the cell, where a mobile terminal communicates with other mobile terminals and with a land-based telephony network through said radio base station. The cells are known as omnicellulas in the latter case. The same radio base station can cover several cells with the help of directional antennas, these cells are known as sector cells. Radio channels assigned to the mobile radio system areshared by the cells included in the system. A set of the same radio channels can be mutually employed in several cells. Cells that employ the same radio channels are spaced sufficiently apart so as not to interfere with each other. This reguires of a careful planning of the cells. The planning for the first time of a cell includes the choice of the respective positions of radio base stations and antennas, among other things. The power at which the antennas are allowed to transmit is governed by the positions of the radio base stations and the antennas, which in turn determines the area covered by the base stations. Improvements in capacity, for example, require that - the cells are smaller and therefore the maximum output power allowed must be reduced. In order to accurately plan a cell 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 accurately and quickly. EP 0684707 A1 teaches an arrangement and method for controlling the power of transmission of radio frequency signals. A sensitive element to the power placed inside an antenna element allows the monitoring of thepower of transmission of radio frequency signals. The signal power measured by the power-sensitive element is converted from analog to digital and supplied to a microprocessor. The microprocessor generates an output signal in relation to said input signal, said output signal controls a variable attenuator included in the transmitter chain of the array and consequently influences the output power of the radio frequency signals by virtue of different levels of attenuator attenuation. The control of the power is carried out with each segment and the power of a transmitted radio frequency signal does not change during a time segment but is adjusted between time segments. Document EP 0695031 A2 teaches a mobile communication arrangement that includes a control circuit to adjust, or set, the output power of radio frequency signals. A reference voltage generator generates a reference voltage that is compared to a voltage detected through a comparator. The detected voltage corresponds to a power of a radio frequency signal to be transmitted. The detected voltage is obtained by measuring the power of the radiofrequency signal with an output power sensor and the conversion of the measured power into a corresponding detected voltage with a detector. The reference voltage corresponds to an output powerdesired of the radio frequency signal. The comparator generates a difference signal, that is, 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 array. The control circuit establishes the amplification factor of the power amplifier in such a way that the output power of the radio frequency signal corresponds to the desired output power. Generated reference voltages are derived from measurements of received radiofrequency signals and the reference voltages are therefore dependent on the received radio frequency signals. JP 07250020 A discloses a regulator designed to control the output powers of radio frequency signals that must be transmitted from a portable telephone or a similar device. According to this solution, when measuring the power in which the radiofrequency signals are transmitted, an antenna is used that receives a part of these radiofrequency signals that are sent by the portable telephone. The received radiofrequency signals are detected and compared with a d.c. in a comparator and the difference indication signal generated in this way indirectly controls a variable amplifier in the transmitter link of the portable telephone.
SUMMARY OF THE INVENTION The present invention addresses the problem of how previously determined amplification factors (gain) can be established with good tolerance for transmitters and receivers in a radio unit regardless of the ambient temperature, even when a long feeder is used between the transmitter and receiver unit and a remote amplifier stage. Another problem solved by the present invention is the problem of guaranteeing a maximum output power of radiofrequency signals sent from the radio unit. Another problem to which the present invention is focused is the problem of eliminating the need for a manual adjustment of the maximum power transmitted from an antenna arranged in the radio unit, and the manual adjustment of the amplification of the receiver link in the radio unit when installed. Thus, an object of the present invention is to establish initial specific amplification factors (gain) with good tolerance for the transmitter and receiver of the radio unit. Another object of the present invention is to guarantee a maximum output power of radiofrequency signals sent from the radio unit.
Another object of the present invention is to eliminate the need to manually adjust the radio unit at the time of installation. The aforementioned problems are solved in accordance with the present invention, by supplying a power sensor device in the vicinity of an antenna in a radio base station. The power sensor device converts the transmitted radiofrequency signals into a detector voltage corresponding to the radio signal. The detector voltage is compared to a reference voltage in a difference amplifier. The reference voltage is generated at 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 establish the amplification of a first variable amplifier in the transmitter link in an embodiment of the present invention, and also a second variable amplifier in the receiver link. An advantage offered by the present invention is that the temperature dependence of all the components on the transmitter link is automatically compensated except for the difference amplifier. Another advantage is that the amplification of the transmitter and thereceiver (gain) can be set simultaneously with the same control circuit. A further advantage provided by the present invention is that the amplification at the transmitter link and at the receiver link is independent of the attenuation at a feeder installed at a radio base station between a transmitter and receiver unit and a remote stage. of amplification. Another advantage offered by the present invention is that the need to manually adjust the output power when the radio base station is installed is eliminated. The present invention will now be described in greater detail with reference to preferred embodiments thereof and also with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates one embodiment of a radio unit of the present invention. Figure 2 shows the relationship between the transmitted power and the adjusted amplification level. Figure 3 shows how time segments with different power levels follow a reference signal corresponding to a specific power level. Figure 4 shows another embodiment of the radio unit of the present invention with two essentially identical radio units.
Figure 5 shows another embodiment of the radio unit of the present invention. Figure 6 shows another embodiment of the radio unit of the present invention. Figure 7 illustrates a temporal control of the output powers at the highest levels for some time segments. DESCRIPTION OF PREFERRED MODALITIES Figure 1 shows a radio unit 100 that is part of a radio base station. The radio unit 100 includes a transmitter and receiver unit 107 wherein essentially all of the signal processing for the radio base station is carried out. The radio frequency signals generated by the transmitter part of the transmitter and receiver unit 107 occurs at the connection 116 of the transmitter and receiver unit. The generated radiofrequency signals are fed through a feeder 117 to a connection 118 in an antenna unit 119 that is located on the top of a mast. A circulator 108 connects the generated radio signals to an input 102 of a remote amplifier transmitter unit 101. In another embodiment, the circulator 108 can be replaced by a duplex filter that operates in accordance with the same principles as the circulator 108. remote amplifier transmitter unit 101 includes a firstvariable amplifier 109 and a power amplifier 120. The first variable amplifier 109 may consist of a fixed attenuator, but is referred to below as an amplifier. The radio frequency signals arriving at the input 102 of the remote amplifier transmitter unit are amplified to a predetermined level by means of the remote amplifier transmitter unit 101 and are supplied to an output 103 of said remote amplifier transmitter unit 101. Radio frequency signals generated at the output 103 are supplied to an antenna 113 through a duplex filter 114. The radio frequency signals received by the antenna 113 are supplied to an input 105 of a remote amplifier receiver unit 104 through a filter duplex 114. The received radio frequency signals that occur at the input 105 of the amplifier receiver unit 105 are amplified to a given level and supplied to an output 106 of the remote amplifier receiver unit 104. The remote amplifier receiver unit 104 includes an amplifier 121, for example, a low noise amplifier, and a second variable amplifier 110. The radio frequency signals arriving at the output 106 of the remote amplifier receiver unit 104 are supplied to the amplifier. transmitter and receiver unit 107 through the circulator 108 and the feeder 117. All the detection of the signal ofreceived radio frequency is carried out in the receiver part of the transmitter and receiver unit 107. It is not necessary to use the same antenna for transmitting and receiving, and separate antennas can be used for this purpose. In the latter case, the power detection device (111) will be placed in the vicinity of the antenna provided for the transmission. The power of the transmitted radiofrequency signals must be limited so as not to interfere with other radiofrequency signals of the same frequencies that are used in a cellular radio system, among other things. There is also a maximum allowed power that can not be exceeded to transmit radio frequency signals in a cellular system. This maximum power is determined at the national level. Both the limitation and the control of the transmission powers are made with the help of a control circuit in the antenna unit 119. The control circuit includes a power detection device 111, a signal difference amplifier 112 which includes a peak retention detector and an amplifier, the first variable amplifier 109. The magnitude of the power of a transmitted radiofrequency signal is determined by a magnitude of a reference signal Uref. The power detection device 111 converts the power value of a radio frequency signal measured ina detector signal Udet corresponding to said power value. As shown in Figure 1, the power detector device 111 can be placed in the vicinity of the antenna 113 or at any other position on the transmitter link downstream of the first variable amplifier 109. The difference amplifier 113 compares a Udet detector signal with reference signal Uref? whereby a difference signal Ue is obtained through which the difference between the value of the detector signal and the value of the reference signal is indicated. The obtained difference signal Ue is used to control the amplification factor of both the first amplifier 109 and the second amplifier 110. The amplification factors for respective variable amplifiers are controlled in a known manner. A closed loop comprising the difference amplifier 112, the first variable amplifier 109, the power amplifier 120, the antenna 113 and the power detection device 111 therefore continues to play a control function until the detector signal Udet be equal to the reference signal Uref. The radio base station sets the reference signal Uref to a maximum value allowed for the cell of the radio base station. Since there is always a maximum for each cell in each time segment that corresponds to a power outputmaximum, the difference amplifier 112 will adjust the amplification of the first variable amplifier 109 in such a way that the detector signal Udet is equal to the reference signal Uref. Radio frequency signals that are sent to the transmitter and receiver unit 107 and from said unit through the feeder 117 will be subjected to attenuation during transport in the feeder. The attenuation in the feeder 117 depends, among other things, on the length of the feeder and its temperature. It is extremely important that a cellular system has a good capacity for power regulation, partly to comply with the regiments established by the authorities regarding the highest allowed power output, and partly to obtain a good spectrum efficiency, in other words determine the cell size with the help of different transmission powers in order to be able to repeat (reuse) the same frequencies as soon as possible. This results in a lower interference with the other calls in the vicinity. The power in which a mobile terminal transmits is determined in the Base Station Subsystem (BSS). A BSS calculates the transmission power required by the mobile terminal, by measuring the power received fromof the mobile terminal. In this way, the BSS takes into account the maximum transmission power of the mobile terminal and also quality measurements made by a base transceiver station (BTS). The amplification (gain) is calibrated in combination with the production of the radio unit 100, both in terms of the transmitter link and the receiver link in said unit. This also applies to the remote stage of the amplifier. The transmitter link amplification is the total amplification from the connection 116 in the transmitter and receiver unit 107 to an output of the duplex filter 114, through the remote amplifier transmitter unit 101. When the output power of a signal of radio frequency from the transmitter and receiver unit 107 is designated as Puts / M, the attenuation at the feeder 117 is designated AF, the amplification of the first variable amplifier 109 is designated Gtra of the power amplifier 120 is designated Gt, an output power Ps towards the antenna can be calculated in accordance with Ps =Where 1 x Gra x Gt must be kept constant in the transmitter link. The Puts / M output power from the transmitter and receiver unit 107 is known. The amplification Gt of the power amplifier 120 is known. The AF feeder attenuation varies greatly, with thedegree of attenuation according to the installation, for example, according to the length of the feeder, and also with the temperature. The Gtra amplification of the first variable amplifier can be controlled. When the output power of the BCCH emission control channel is controlled, in order to keep constant, a change in the GA amplification of the first variable amplifier will occur in response to a change in the attenuation of the AF feeder due, for example , at a temperature change, such that the combined amplification for the feeder 117 and the first variable amplifier 109 will remain constant, that is, the product of 1 x Gtra will remain constant. When the AF feeder attenuation doubles as a result of a temperature change, for example, the control circuit will regulate the Gtra amplification of the first variable amplifier in order to double its amplification. The output power is maintained in this constant manner, despite an increase of twice as much as the attenuation of the AF feeder. The aforementioned difference signal Ue is therefore a measurement of the AF feeder attenuation, among other things. The amplification of the receiver link is the total amplification of the antenna 113 to the connection 116 in the transmitter and receiver unit 107, through the remote amplifier receiver unit 104. When the power of a signal ofradio frequency received by the antenna 113 is designated Pmot / antenn / the amplification of the low noise amplifier 121 is known as GR, the amplification of the second variable amplifier 110 is designated Grec and the feeder attenuation is designated AF, the receiver power Pmot in the connection 116 for a received radio frequency signal can be calculated in accordance with Pmot = P8ot / antenn GR x Grec x 1, where GR x Grec x 1 is an amplification that must be kept constant at the receiver link. Since the aforementioned difference signal Ue is a measurement of the AF feeder attenuation, the difference signal is also used to control the second variable amplifier 110. A change in AF feeder attenuation results in a corresponding GR amplification. to the amplification of the second variable amplifier, in such a way that the product of GR x Grec x 1 remains constant. The reference signal Uref can be varied in at least two ways. This will be described below with reference to figure two and figure three. A method of the present invention for controlling the amplification for the first variable amplifier 109 and the second variable amplifier 110 will be described below with reference to FIG. 3. This method of the present invention for controlling the power will be explainedin relation to a Time Division Multiple Access (TDMA) system of the GSM type. It will be understood, however, that the invention can also be applied in other mobile radio systems. A mobile radio system constructed in accordance with TDMA technology has several frequencies, all of which are divided into a specific number of time segments. There are 8 time segments for each frequency in the GSM system. Each control channel or traffic channel is sent from the radio base station and the mobile telephone in these time segments. An emission control channel (BCCH) is a control channel that contains important information for mobile terminals. The BBCCH transmits from the radio base station all mobile stations located within the area covered by the radio base station. The BCCH transmits with the maximum power allowed for the cell in order to be able to reach all the mobile stations present in the cell. All cellular radio systems include a channel transmitted at the highest possible power level and which functions to supply information to all mobile stations. The channel is generally known as the broadcast channel, even though it has its own specific designation in relation to our system (?). Figure 2 is a time diagram illustrating aSequential transmission of time segments. A first time segment 200 corresponds to the control channel BCCH, while a second time segment 201, a third time segment 202, a fourth time segment 203 and a fifth time segment correspond to another signal, which may be already be a traffic channel or a control channel. The magnitude of the output power of the BCCH is established by suitably choosing the magnitude of the reference signal Uref. In the case of this mode, it is only necessary to change the reference signal when changing the size of the cell. The difference amplifier 112 is implemented with a peak retention detector having a fast rise time and a slow fall time. This is shown in Figure 2 by an interrupted line 210, which corresponds to the amplification of the transmitter link. The transmitter link amplification decreases as a result of the generation by the difference amplifier 112 of the difference signal Ue that the amplification of the first variable amplifier 109 influences. The slope of the interrupted line 210 has been greatly exaggerated in order to clarify this principle. In this case, the difference signal Ue occurs because the stored value of the measured detection signal Udet decreases as a result of theknown construction of the peak retention detector. When the first time segment 200 is sent, the amplification of the first variable amplifier 109 is adjusted in the manner explained above. The output power of the BCCH is adjusted in a transmitter part of the radio unit 100. The output power of the second time segment 201 is adjusted through the radio unit 100, amplified in the remote amplifier transmitter unit 101, and is transmitted by means of the antenna 113. Since the difference amplifier 112 includes a peak retention detector, the regulation or control circuit will avoid adjusting the second time segment to a level corresponding to the reference signal. Uref. The peak retention detector will only take into account the highest measurement signal. The difference amplifier 112 including said peak retention detector thus remembers the highest measured power. As will be understood, the method of the present invention for controlling the maximum output power is not limited to the measurement and control of the output power of the BCCH. The same measurement and control processes can be carried out for any known signal and time segment having a maximum output power. Alternatively, the reference signal may vary for each segment? E time, in which case the adjustment is madeof power by means of the regulation circuit in the antenna unit 119 for all time segments. In this embodiment, a standard difference amplifier is used instead of a peak retention detector, said amplifier provides a rapid adjustment of the output power of each time segment. The transmitter part of the transmitter and receiver unit 107 contains information on the magnitude of the power at which the time segments will be transmitted. In this case, the reference signal Uref is generated in the transmitter part of the transmitter and receiver unit 107, and is supplied to the regulation or control circuit of the antenna unit 119 for each time slot. This is not illustrated in any of the figures. However, several solutions are available regarding this aspect. An example is found in a circuit that includes a memory store and a digital-to-analog signal converter. The memory contains a table in which the various values correspond to a reference signal Uref. In turn, the reference signal Uref corresponds to a desired power output given radio frequency signals. The radio base station generates a digital value that indicates a table value in memory. The indicated value is converted from digital to analog, obtaining in itself the reference signal Uref. A new reference signal is generated for each time segment.
The interrupted line 310 in Figure 3 illustrates how the power for the transmitter link varies with the transmitted time segments. This makes the output power independent of both temperature variations and frequency variations. This is due to the fact that the output power of the transmitter and receiver unit 107 changes at the same time as the reference signal Urßf. The reference voltage Uref is set to a power value or which corresponds to the power value for a first time segment 300 which can be a BCCH, for example. When a second time segment with a lower output power is to be transmitted, the reference output Uref is changed to a lower value corresponding to the output power Pi. The output power from the transmitter and receiver unit 107 is changed at the same time. When a third time segment 302 having an output power P2 is to be transmitted, the reference voltage Uref is set to a value corresponding to the power P2. The power detection device 111 measures the power of the radiofrequency signal of each time segment and generates a detector signal Udet corresponding to each power. The output power adjustment continues in this manner for all time segments sent from the radio unit 100. A radio unit having a transmission capacity andreception higher than the radio unit 100 described with reference to Figure 1 is obtained by combining two identical combination units 400 (a), 400 (b), so that a radio unit 400 is provided. Figure 4 illustrates said highest capacity radio unit 400. The communication units 400 (a), 400 (b) are essentially formed of the same components as the radio unit 100. The radio unit 100 was described above with reference Figure 1. In this embodiment, however, on the one hand a first detector signal Udeti is obtained which corresponds to the power of a radiofrequency signal sent from a first antenna 113 (a), the power of said signal The radio is converted by means of a first power detection device 111 (a) into said first detector signal, and, on the other hand, a second detector signal Udet2 corresponding to the power of the radio frequency signal sent from a second antenna 113 (b), the power of said radio signal is converted through a second power device 111 (b). With this embodiment the use of the reference signal Uref is provided to control the system in such a way that the output powers of the radio signals sent respectively from the first antenna 113 (a) and from the second antenna 113 ( b) do not exceed the maximum allowed power.
The radio unit 400 also includes a first peak retention detector 412 (a) with amplification and a second peak retention detector 412 (b) with amplification, said sensors each generate a respective first reference signal Uei and a second Ue2 difference signal. The first signal of difference Ue? is obtained from the first peak retention detector 412 (a) by comparing the first detector signal Udet? with the reference signal Uref. The second reference signal Ue2 is obtained from the second peak retention detector 412 (b) by comparing the second detector signal Udet2 with the reference signal Uref. The first difference signal Uel is compared to the second difference signal U? 2 with the aid of a comparator 425 which generates an output signal that moves a switch 436 either to a first state 1 or to a second state 2. The peak retention detectors 412 (a), 412 (b), comparator 425 and switch 426 form a difference amplifier 412. If the first difference signal Ue? has the highest value, the switch 426 is switched to its first state 1, whereas if the second difference signal Ue2 has the highest value, the switch 426 is switched to its second state 2. The first difference signal corresponds to the detector signal of the highest value. The highest difference signal of the first difference signal Ue? and the second difference signal Ue2 is chosen by means of theyou.comparator 425 as mentioned above, and this accordingly corresponds to the difference signal Ue present at the output 425 of the difference amplifier 412 in FIG. 4. The obtained difference signal Ue is used to adjust a first variable amplifier 409 (a) , a second variable amplifier 409 (b) a third variable amplifier 410 (a) and a fourth variable amplifier 410 (b). With a common adjustment of the variable amplification in a first remote transmitter amplifier unit 401 (a) and a second remote amplifier transmitter unit 401 (b), the first remote amplifier transmitter unit 401 (a) and the second remote transmitter unit Transmitter amplifier 401 (b) will have the same high amplification. Because the remaining components of the respective communication units for 400 (a), 400 (b) are essentially identical, the same amplification will be obtained at the transmitter links of the respective communication units 400 (a), 400 (b) ). They apply to the receiver link of respective communication units 400 (a), 400 (b). In other words, when the variable amplification in a first remote amplifier receiver unit 404 (a) and in a second amplifier receiver remote unit 404 (b) have a common setting, the same amplification factor will be obtained for the first remote unit. of amplifier receiver 404 and for the second remote amplifier receiver unit 404 (b). The knowledge that one of the twounits 400 (a), 400 (b) transmits a radio frequency signal with a maximum allowed output power allows the amplification of the transmitter link and the setting of the receiver link of the communication units 400 (a), 400 (b) . As mentioned above, the signal that is sent with a maximum power can be the BCCH broadcast control channel in a GSM system, for example. Figure 5 shows another embodiment of a radio unit of the present invention 500. The radio unit 500 includes two essentially identical communication units 500 (a), 500 (b). The embodiment illustrated in Figure 5 differs from the embodiment of Figure 4 insofar as a first feeder 517 (a) is connected between the transmitter and receiver unit 507 (a) and the first remote amplifier transmitter unit 401 (a), a second feeder 550 (a) is connected between the transmitter and receiver unit 507 (a) and the first remote amplifier receiver unit 504 (a), and a third feeder 517 (b) is connected between the transmitter and receiver unit 507 (b) and the second remote transmitter amplifier unit 401 (a), and a fourth feeder 550 (b) is connected between the transmitter and receiver unit 507 (b) and the second remote unit of transmitter amplifier 401 (b). Another difference is in the use of separate transmitter and receiver antennas for each unit ofcommunication. The first remote amplifier transmitter unit 401 (a) is connected to a first transmitter antenna 513 (a) through a first band pass filter BPla, while the first remote amplifier receiver unit 504 (a) is connected to a first receiver antenna 551 (a) through a second bandpass filter. The communication unit 500 (b) is constructed correspondingly, ie the second remote amplifier transmitter unit 401 (b) is connected to a second transmitter unit 513 (b) through a third bandpass filter BPlb, while the second remote amplifier receiver unit 504 (b) is connected to a second receiver unit 551 (b) through a fourth bandpass filter BP2b. The control of the power is carried out in the radio unit according to FIG. 5 in the same manner as illustrated in FIG. 4 in relation to the radio unit 400 of the present invention described above. In a further embodiment of a radio unit of the present invention which includes more than a communication unit 600 (a), 600 (b), compensation is made for possible variations of the accumulation between the feeders 117 (a), 117 (b) of the respective units 600 (a), 600 (b). This additional embodiment is described with reference to Figure 6. The 600 radio unit includes twocommunication units 600 (a), 600 (b), similar to the radio unit described with reference to figure 4. Each of the communication units 600 (a), 600 (b) differs slightly from the units illustrated in Figure 1 and Figure 4, to the extent that the variable amplifier 609 (a), 609 (b) of the remote transmitter stage is connected between the feeder 117 (a), 117 (b) and the circulator. This placement makes the variable amplifier 609 (a), 609 (b) common both to the remote amplifier transmitter unit and to the remote amplifier receiver unit. As in relation to the embodiments described above, each remote amplifier transmitter unit includes a remote power amplifier 620 (a), 620 (b), in addition to the variable amplifier 609 (a), 609 (b). Each remote amplifier receiver unit includes an amplifier receiver 621 (a), 621 (b) in addition to the variable amplifier 609 (a), 609 (b). The amplifier receiver 621 (a), 621 (b) and the power amplifier 620 (a), 620 (b) are connected in parallel between the circulator and the duplex filter. The duplex filter is connected to the antenna 613. Each communication unit 600 (a), 600 (b) includes a power detection device 111 (a), 111 (b) and a separate reference amplifier 612 (a) , 612 (b). The difference amplifier 612 (a), 612 (b) receives the power level measured from the device at an inputpower detection 111 (a), 111 (b) and in another input a reference signal Uref. the output of the difference amplifier 612 (a), 612 (b) is connected to the variable amplifier 609 (a), 609 (b) and controls its amplification through the medium of a difference signal Ue ?, Ue2 • The unit of radio 600 also includes a control unit 630 having connections 631, 632 (a), 632 (b), in accordance with what is described below. Thus, each communication unit 600 (a), 600 (b) of this mode has its own power level control system that operates independently of the other communication units 600 (a), 600 (b). Only BCCH is always transmitted at a maximum power level and only one 600 (a), 600 (b) communication unit can send BCCH at a time. Thus, with separate power regulation loops, only one communication unit 600 (a), 600 (b) can set the level of the difference amplifier 612 (a), 612 (b) with the help of BCCH at the same time. Since channels other than BCCH also sometimes transmit above the maximum power, the difference amplifier can also adjust the correct level when one of these channels is transmitted at maximum power. One way to ensure that the maximum power will be constantly transmitted in a channel from each communication unit 600 (a), 600 (b), is to move theBCCH transmission between the two communication units 600 (a), 600 (b). In this case, a communication unit 600 (a), 600 (b) will transmit in BCCH in a short period of time and establish the correct power level and may then wait for at least a few minutes before requiring a new adjustment of the power. power level. The BCCH is moved again and the radio power output is adjusted to the correct power level. This implies that the difference amplifier 612 (a), 612 (b) keeps the difference signal level Ue ?, Ue2 between these periods in which the transmission is at a maximum radio power. The difference amplifier may include the peak retention detector described above 412 (a), 412 (b), as it has a very slow decay time. Alternatively, the difference amplifier may have a digital memory function that preserves the output signal constant at the level set in the last transmission at the maximum power output. Attenuation variations in the feeder are generally slow and the control loop that compensates for this attenuation can also be slow. An alternative solution is to increase the transmission power to a maximum level allowed in a short sequence for one or several time segments and therefore update the level from the difference amplifier.612 (a), 612 (b). This range can become a long interval, for example, a range of 10 minutes or more, between short sequences of maximum power transmission. The principle of this solution is shown in Figure 7, where the difference signal Ue ?, Ue2 supplied by the difference amplifier 612 (a), 612 (b) is indicated by means of an interrupted line, which corresponds to the amplification from difference amplifier 612 (a), 612 (b). It is considered in this case that a difference signal Uei, Ue2 from the difference amplifier 612 (a), 612 (b) is conserved at a constant level between updates with the help of a digital memory circuit. When the power output is temporarily raised to a maximum level in this case, the difference signal Ue? Ue2 supplied by the difference amplifier 612 (a), 612 (b) will be slightly lowered, in accordance with what is indicated by the line interrupted in Figure 7. Instead of allowing the difference amplifier to maintain the level of the difference signal Ue ?, Ue2 over a long period of time, the communication unit 600 (a), 600 (b) can be Quickly switched for BCCH transmission. This switch can be elaborated for each time segment, for example. The radio unit 600 illustrated in figure 6 includes allthe components from the end of the two feeders 117 (a), 117 (b), to the antennas 113 (a), 113 (b), in the antenna unit 619, and including said antennas 113 (a), 113 ( b) The antenna unit 619 also includes a control unit630. The control unit 630 is connected to a monitoring unit located adjacent to the transmitter and receiver unit 107, through a data collector631. The monitoring unit is not illustrated in Figure 6. The level or levels of the reference signal Uref is set (n) in the radio unit 600 with the help of the monitoring unit. The control unit is also connected to the two difference amplifiers 612 (a), 612 (b) through data collectors. The level of the difference signal Uref is sent to the control unit 630 in the antenna unit 619 from the monitoring unit. The control unit supplies the difference amplifiers 612 (a), 612 (b) with the reference voltage Uref through the data collectors 632 (a), 632 (b). The reference voltage Uref is provided as a digital value and converted from digital to analog value by difference amplifiers 612 (a), 612 (b) respectively. When a power adjustment is made for each transmitted time segment, in accordance with that described above with Figure 3, the control unit 630 changes the level of thereference signal transmitted Uref for each time segment and each difference amplifier 612 (a), 612 (b). The data collectors 632 (a), 632 (b) which connect the control unit 630 with the difference amplifier 612 (a (, 612 (b) are bidirectional.) The control unit 630 reads the detector voltage Udet received by each difference amplifier 621 (a), 621 (b) through the power detecting device 111 (a), 111 (b) If the received detector voltage Udet is excessively low, the control unit 630 reports this situation to the monitoring unit Any malfunction of the link feeder 117 (a), 117 (b), remote power amplifier, or antenna 113, 113 (b) a with respective connections will be discovered through this report of differences Naturally, more than two radio units can be combined in a single radio unit, in order to obtain even greater capacity: the amplification in the transmitter link and in the receiver link of each communication unit (400 ( a), 400 (b), 600 (a), 600 (b) ) in a radio unit consisting of more than two communication units is controlled and adjusted in the same way as explained with reference to figure 4 and figure 6. Transmissions in BCCH can also be controlled to alternate between more than two units of radio. Several known radio base stations include aantenna that is common for both uplink and downlink, while other known radio base stations include separate uplink and downlink antennas. The present invention can be applied with both variants and, for example, the radio unit in Figure 1 can be equipped with an antenna for uplink and an antenna for downlink. In this presentation, it has been considered for the sake of simplicity that the antenna unit 119 is placed on top of a mast, or other than the transmitter and receiver unit 107. The transmitter and receiver unit 107 is normally placed in the base of the mast and the antenna unit 119 up on the mast. However, there are numerous variations in the placement of the antenna and transmitter and receiver unit. An example in this regard is an internal cell where the transmitter and receiver unit 107 should be placed in a different position relative to the antenna unit 119, for aesthetic reasons or for reasons of space. It will be understood that the invention is not limited to the embodiments described and illustrated and that modifications may be made within the scope of the appended claims.