EP2862234B1 - Active antenna system - Google Patents

Description

Mobile networks are known to be structured so that they are divided into a plurality of individual mobile radio cells. The mobile radio cells are formed by supplying a specific area with radio signals through base stations. The base stations are equipped for this purpose with antennas having a suitable directional characteristic. Usually, club-shaped directional characteristics are used. The size of the cell and the area to be supplied can be changed, for example, by different setting of a lowering angle (down-tilt) of the directional characteristic, for which purpose differently adjustable phase shifters are used in the respective antenna. This change can also be made depending on the number of active users in a cell.

The antenna of such a mobile radio base station is known as an antenna array, which is used for transmission and reception. This is where the Communication is handled with a mobile subscriber located in the cell in question, which is often synonymous as a transmission (from the base station side of view) speaks of a downlink. The data transmitted by the mobile subscriber to the mobile station data that are thus received by the antenna array are often referred to as uplink.

In modern mobile networks, there is an imbalance between the uplink and the downlink operation with respect to the data rates or the respective received transmission power, that is viewed between the reception and the transmission mode of the base station.

Because the base stations usually have antennas with a relatively high antenna gain and have due to corresponding power amplifiers over a relatively high transmission power. Therefore, a relatively high power can be provided to the receiver in the downlink. On the other hand, however, the mobile devices (the so-called cell phones, smart phones or other mobile devices, for example, equipped with appropriate transmitting and receiving devices notebooks, etc.) antennas with only a relatively small antenna gain and a relatively low available transmit power. As a result, only a relatively low power can be provided to the receiver in the uplink. This imbalance between the services at each recipient in the uplink and downlink has a negative effect, especially at high data rates.

In order to come to certain improvements, it has already been proposed in the past to further optimize the uplink path. It has been attempted to electrically adjust the resulting vertical radiation pattern for uplink operation (ie, base station receive mode) and downlink operation.

This is also possible because meanwhile so-called active antenna systems with different technical designs are known. Common to all is in common that part of the base station technology, preferably the high-frequency electronics (RF electronics) has been integrated in the meantime in the antenna. This results in a number of advantages, such as energy savings, less need for cables and interfaces, a reduction in footprint, etc. Ultimately, this also leads to a more visually appealing design of such antenna arrays and base stations. A main technical feature is that the individual antenna radiators or radiator groups are equipped with the mentioned transmitting and receiving electronics. Thereby it is e.g. possible to set the downtilt for the uplink and for the downlink separately.

By such measures, for example, capacity increases of, for example, 5% to 20% compared to conventional solutions should be possible.

However, there is also a great risk with such active antennas. The biggest risk factor concerns the electronics mounted on the mast or in the antenna. After all, the products and, above all, the electronics should generally remain faultless for 10 to 15 years, and this in some of the most adverse environmental conditions. The so-called "meantime between failure" (MTBF), ie the interval until the failure of an electronics unit (ie a measure of the failure-free time), is an important factor to be able to describe the expected lifetime of an active antenna. The more electronics an active antenna contains, the lower the MTBF.

Conventional systems usually have such a failure-free time (MTBF) of about 50,000 hours. This number is in clear contradiction to the requirement that such products should fulfill a failure-free service life of, for example, 10 to 15 years.

A mobile radio system and an associated control system is basically from the WO 03/052866 A1 known. According to this prior publication, it is described how two antennas with different vertical diagrams can be operated in the same sector of the cell. It is discussed that the ratio of the transmission power between the antennas is changed, whereby the respective received power is optimized at the corresponding receiver.

From the technical literature it can be seen that it is useful for side lobe suppression in an antenna array, the power supply to extreme emitters of the antenna array less power than the central emitters. This principle is described e.g. in the textbook "Antenna Theory third edition" by Constantine A. Balanis in the section "6.8.2 Binomial Array".

According to the EP 1 684 378 A1 An array antenna is described which comprises two passive subgroups with mechanical phase shifters arranged vertically to one another. The phase difference between the two subgroups can be electrically adjusted. For this purpose, a phase shift adjustment module is arranged upstream of both subgroups of the antenna array, which is connected via a subsequent separate distribution network with the individual radiator elements of the two array subgroups.

A conventional antenna with superimposed and jointly powered by a network emitters is from the WO 2006/071152 A1 to be known as known.

An active antenna system is also from the US 2010/0311353 A1 to be known as known. It includes several antenna groups, each for the transmitting and Receiving operation are provided. These antenna groups are fed accordingly via a phase shifter group in order to be able to set a downtilt angle.

The sake of completeness should also on the DE 43 22 863 A1 refer to a mobile radio antenna system.

In this prior publication, an antenna system according to the prior art is described, which is referred to as "three-antenna solution", wherein one of the antennas is used exclusively as a transmitting antenna and the channels to be transmitted are summarized by crossovers or coupler networks and fed into the transmitting antenna. The two other antennas are used only for reception, each antenna receiving all the channels and with the antennas mounted so that the reception of the antennas is independent and thus the desired redundancy is ensured.

Another mobile radio antenna system is off US 2010/022552 known.

A generic transmitting / receiving antenna with any use of a Antennenapertur is from the DE 698 37 596 T2 to be known as known. It comprises two antennas arranged one above the other, both antenna groups being provided for receiving and an upper or a lower antenna group for transmitting in different frequency ranges.

In contrast, it is an object of the present invention to provide an improved solution that is suitable to reduce the existing imbalance between an uplink operation and a downlink operation of a mobile radio antenna system, ie between the receiving and transmitting mode or compensate and thus by the existing Imbalance between an uplink and a downlink operation to reduce existing disadvantages.

As on the mobile phone user side, so on the part of the phones used, smart phones or other devices enabling a mobile communication, due to the there only low available power supply and the design-related low antenna gain in principle not to expect a significant improvement sets the invention at the base station side.

The inventive antenna system is defined by claim 1.

In the context of the invention, it is proposed to use an antenna array comprising at least a first and a second antenna group.

While the first antenna group is provided for the transmitting and the receiving operation, the second antenna group should be used only or above all only for the receiving operation. The antenna groups, each comprising at least two antenna subgroups (each Antenna subgroup has at least one radiator) are arranged one above the other.

Via a feed network, the phases and powers for the antenna subgroups can be provided, for which purpose mechanical phase shifters are preferably provided.

In order now to enable an improvement between the uplink and downlink operation, the invention proposes a frequency-dependent amplitude distribution at least for the first antenna group which is provided for the transmission and the reception operation.

The amplitude distribution within an antenna array is understood here to be the relative distribution of the signal levels present at the various individual antenna subgroups in the transmission or reception mode. The signal is preferably an electrical one in the form of a voltage, a current or a power. This is standardized by specifying a level in dB. Usually, the signal levels are normalized to the maximum signal level of one of the antenna subgroups applied in the transmit or receive mode. However, it may also be useful to relate the signal levels to the level of a selected antenna subset in transmit or receive mode. Instead of signal level is also spoken here simply by an amplitude, which are given relative to simplify the sake of simplicity.

The amplitude distribution for the transmission and reception operation of the first antenna group is different. In simple terms, the difference may be that the amplitude of the antenna subgroups decreases from a highest value, preferably represented by a central antenna subgroup, to the antenna antenna subgroups in the transmit mode (downlink). Furthermore, there are also applications in which all antenna subgroups in the downlink are fed with the same amplitude or only individual antenna subgroups get a little more power. However, the preferred embodiment is the former. In the receive mode (uplink), however, the amplitudes of the outermost or next to last antenna subgroups of the first antenna group, based on a highest amplitude of one of these antenna subgroups, are changed. The amplitudes may be equal to the maximum amplitude of one of the antenna subgroups (that is, preferably not smaller), or preferably only comparatively less or else more steeply sloping than in the transmit mode.

Assuming that the amplitude of the outermost or the penultimate antenna subgroup in relation to the highest amplitude of the antenna subgroup has a value A _Rx at a reception frequency, and in that case further assuming that the amplitude of the outermost or penultimate antenna subgroup based on the highest amplitude of the antenna subgroup a value A _Tx at a transmission frequency, the amount of the difference between the two aforementioned values shall be at least 0.2 dB multiplied by the number of antenna subgroups and a maximum of 5 dB multiplied by the number of antenna subgroups within the scope of the invention.

Above all, this measure ensures that the described imbalance between uplink and downlink operation is significantly improved compared to conventional solutions, and this also applies to more heavily damped side lobes. Damped side lobes have the advantage that in particular the first side lobe above the main lobe radiates weaker into adjacent mobile radio cells. The resulting interference is thus reduced.

In a preferred embodiment of the invention, the signals received over the two antenna arrays may be used via methods such as MRC (Maximum Ration Combining) or ERC (Equal Ratio Combining) or methods such as IRC (Interference Rejection Combining) or the like. The processing takes place in a transmitting and receiving unit. The method is the combination of signals from individual antennas or groups that can be exploited for diversity gain with available reception diversity. Furthermore, it is conceivable the phases of the signals, the two antenna groups be changed within the transmitting and receiving unit to change. As a result, for example, a separate downtilt can be set for the receive mode in comparison to the transmit mode.

A simple implementation of the invention results above all even if mechanical phase shifters are used for the frequency-dependent amplitude distribution in the feed network.

However, frequency-dependent power dividers can also be used for the frequency-dependent amplitude distribution in the feed network.

The new architecture of the antenna array according to the invention and its supply also shows that, for example, in the case of a dual-polarized radiator arrangement, only one transmitter (transmitter) and only two receivers (receiver) are necessary per polarization. A dual-polarized active antenna according to the invention can thus be used, for example, with only two remote radio heads (or comparable components) with the associated electronic and filter components for two integrated transmission branches (TX branches) and four reception branches (RX branches) of a dual-polarized antenna array will be realized. If one wanted to use a conventional architecture in order to implement and implement only slightly similar effects, then an electronics and filters for at least ten transmission branches and twenty reception branches would have to be integrated for this (eg with five antenna subgroups per antenna group), to achieve a similar result. Above all, the fact that within the scope of the invention in the receiving operation of the mobile radio antenna (uplink relative to the base station) the signals of two antenna arrays are combined, one obtains an additional antenna gain of about 2.5 to 3.0 dB more than in the downlink (Transmit mode) using only one antenna array. Due to the mentioned modern methods for combining signals from individual antennas (for example MRC, ERC, IRC, etc.), one additionally obtains 1.0 to 3.0 dB. By such a new active antenna is thus obtained in uplink operation (receiving mode) in the sum of a performance improvement by about 3.5 to 6.0 dB compared to the downlink operation (transmission mode). This leads to a blatant improvement in data rates. In addition, the uplink and downlink signals can be set to different down-tilt values, allowing further optimization of data rates. This was previously only possible with so-called distributed active antenna architectures.

It would also be possible to operate both antenna groups in the transmission mode. Thus, for example, an intelligent method such as MIMO, SIMO or MISO can be used as well as the joint operation of the antennas in the downlink mode eg for a higher profit.

Figuren 1 bis 3:

drei Ausführungsbeispiele eines erfindungsgemäßen Antennenarrays mit zugehöriger frequenzabhängiger Amplitudenverteilung;

Figuren 4 bis 7:

vier weitere abgewandelte Ausführungsbeispiele eines erfindungsgemäßen Antennenarrays;

Figur 8a :

ein Antennenarray nach dem Stand der Technik;

Figur 8b :

eine Speisung des nach dem Stand der Technik gemäß Figur 8a bekannten Antennenarrays, ebenfalls nach dem Stand der Technik;

Figuren 9 und 10:

zwei weitere abgewandelte Ausführungsbeispiele eines erfindungsgemäßen Antennenarrays;

Figur 11 :

ein vertikales Strahlungsdiagramm eines Antennenarrays gemäß Figur 8a bei einer Amplitudenverteilung gemäß Figur 8b im Empfangsbetrieb; und

Figur 12:

ein vertikales Strahlungsdiagramm eines Antennenarrays gemäß Figur 8a bei einer Amplitudenverteilung gemäß Figur 1 im Empfangsbetrieb.

The invention will be explained in more detail by means of embodiments with reference to the accompanying drawings. This shows in detail

FIGS. 1 to 3:

three embodiments of an antenna array according to the invention with associated frequency-dependent amplitude distribution;

FIGS. 4 to 7:

four further modified embodiments of an antenna array according to the invention;

FIG. 8a:

an antenna array according to the prior art;

FIG. 8b:

a supply of the according to the prior art according to FIG. 8a known antenna arrays, also according to the prior art;

FIGS. 9 and 10:

two further modified embodiments of an antenna array according to the invention;

FIG. 11:

a vertical radiation pattern of an antenna array according to FIG. 8a in an amplitude distribution according to FIG. 8b in the reception business; and

FIG. 12:

a vertical radiation pattern of an antenna array according to FIG. 8a in an amplitude distribution according to FIG. 1 in the reception business.

Subsequently, first on FIG. 8a Reference is made, which shows a schematic representation of an antenna array 1, as previously operated in the prior art. The antenna array 1 comprises, for example, two antenna groups 5, 10 arranged one above the other (usually vertically one above the other). The lower antenna group 5 is also referred to below as the first antenna group 5. The upper antenna group 10 is also referred to as a second antenna group.

Each of the two antenna groups 5, 10 consists of at least two antenna subgroups 6 and 11, each antenna subgroup having at least one radiator. In the illustrated embodiment according to the prior Technique includes both the first and the second antenna group 5, 10 each have five antenna subgroups 6 and 11, wherein each of the antenna subgroups at least one, ie in the embodiment shown two emitters 7 and two emitters 12 includes. In the exemplary embodiment shown, the radiators consist of dual-polarized radiators, which are preferably aligned in each case in a + 45 ° and at a -45 ° angle relative to the horizontal or vertical. In that regard, is often spoken of X-polarized radiators, which can be operated in two mutually perpendicular polarization planes.

Each of the radiators, which belong to a common antenna subgroup, can be fed with the same phase position and / or power, although preferably permanently assigned phase shift elements can be arranged between each two such radiators belonging to a radiator subgroup, so that two to an antenna sub-group belonging emitters with a fixed, ie usually not adjustable phase difference can be fed.

The emitters 7 of the first antenna group 5 are used both in the transmitting and receiving mode, whereas the emitters 12 of the second antenna group are used only in the receiving mode.

In the illustrated example according to the prior art according to FIG. 8a Thus, the radiators 7 and 12 in the antenna groups 5, 10 of the antenna array via cables or coaxial systems or other systems using phase shifters 15 are interconnected. The antenna array is usually designed broadband and covers the reception and transmission frequencies. In order to obtain the best possible side lobe suppression (sidelobe suppression) for interference reduction, the phase shifters are designed with a so-called declining power distribution (power tapering). That is, the radiators, which are arranged in the middle or in the middle region of the respective antenna group 5, 10, receive higher power proportions than the radiators 7, 12 or antenna subgroups 6, 11 lying on the outer edge or adjacent to the outer edge (s. FIG. 8b ). This results in the in FIG. 8b shown power distribution, which may be optimal for the downlink case, but represents a problem for the uplink case, since now results for the overall antenna array in the middle region X, a lower power distribution, resulting in larger side praise, ie larger side lobes , especially in horizontal orientation or slightly below, which are extremely undesirable because they radiate into neighboring cells. The FIG. 11 shows a corresponding vertical radiation pattern. In FIG. 8b In this case, the respective amplitude or power for the respective radiators 7, 12 of the respective antenna subgroup 6, 11 of the two antenna groups 5, 10 is shown above the X axis.

To avoid these disadvantages will now be described with reference to FIG. 1 a first improved embodiment of the invention explained. The statements made so far with regard to the design and construction of the antenna array explained apply equally to the antenna arrays subsequently used in the context of the invention, unless further variants and modifications are provided. The same reference numerals relate to the same extent also parts and components and components, as previously based on FIG. 8a were explained.

An antenna according to the invention can be operated, for example, in the transmission mode in a frequency band from 2110 MHz to 2155 MHz. The reception range can be, for example, between 1710 MHz and 1755 MHz. The statements made below apply in principle to any transmission standard or to any frequency band applied, in particular in the mobile radio field, ie, for example, the 900 MHz band, the 1800 MHz or 1900 MHz band, for the UMTS mobile radio standard (in various countries and regions in different frequency ranges, for example in the 1920 MHz to 2170 MHz band) and / or, for example, for the LTE mobile standard, etc. Restrictions on certain frequency ranges do not apply in this respect. It is only assumed that offset for the uplink (receive mode) and the downlink (transmission mode) mutually adjacent frequency bands or frequency ranges are provided. For the exemplary embodiments according to the invention explained below, it is furthermore advantageous if the number of antenna subgroups 6, 11 and also the number of radiators 7, 12 per antenna group 5, 10 are the same, although an unequal number of antennae Subgroups 6, 11 or of emitters 7, 12 may be present.

The preferred with reference to FIG. 8a described dual polarized radiator can also be polarized in the antenna arrays according to the invention in a + 45 ° and -45 ° plane (without this being a mandatory requirement). Furthermore, they can also be horizontal or vertical, right-handed or left-handed, circular-polarized, elliptically polarized or even only horizontally or vertically polarized. All mentioned polarizations or polarization combinations can likewise be used in the context of the exemplary embodiments of the invention which are explained below.

The structure of the antenna array according to the invention FIG. 1 So in principle corresponds to that, as he said on the basis of FIG. 8a has been explained for the prior art. In the receive mode, ie in uplink mode, the corresponding receive signals Rx (uplink) for each of the two antenna groups 5, 10 and for each polarization via a feed network N11 and N12 for the first antenna group 5 (for signals in the first Polarization level or transmitted in the second polarization plane) of a feed Rx1 or Rx2 supplied. The supply points Rx1 and Rx2 also serve as feed points for the transmit signals (downlink), ie as feed points Tx1 and Tx2, in order to feed in the signals for the two polarizations for the first antenna group 5 into the associated feed network N11 or N12 (polarization-dependent).

For the second or upper antenna array 10 a corresponding feed network is provided N21 and N22 for the two polarization planes, said here about only reception signals R _x (uplink) received and _x is usually no transmission signals T (downlink) are transmitted. Should a simple polarized antenna array be used, of course, only a corresponding feed network would be provided for each one used for the polarization of the first and second antenna group.

The explained antenna groups 5, 10 are in this case connected to a common transceiver unit SE, which consists for example of an antenna near or in the antenna (on the antenna mast) mounted remote radio head (RRH) or a remote radio head (RRH ). It is also possible that the transceiver unit additionally acts as a baseband unit and performs appropriate processing, in particular intelligent methods.

A frequency-dependent power or amplitude distribution for the resulting radiation pattern, ie a different power or amplitude distribution for the uplink and the downlink case, now comes into use within the scope of the invention. In the first embodiment of the invention, as it is based on FIG. 1 is explained in turn FIG. 1 On the left side, an antenna array with a first or lower antenna group 5 and an upper (usually vertically above) or second antenna group 10 shown simplified, each antenna group in the embodiment shown again comprises five antenna subgroups 6, 11. Each of the antenna subgroups has at least one or more radiators 7, 12, as described with reference to FIG FIG. 8a was explained.

In the representations according to the invention according to the FIGS. 1 to 7 In this case, the first or lower antenna group 5 and the upper or second antenna group 10 with the antenna subgroups 6, 11 are shown only in simplified form. The individual antenna subgroups are characterized for the first antenna group 5 as well as for the second antenna group 10 in each case from top to bottom with the individual assignments a1, a2, a3, a4 and a5 continuously. These antenna subgroups 6, 11 may be embodiments in which the emitters provided are simply polarized or dual polarized, as explained, in the form of a so-called X polarization, etc. Accordingly, the physical structure is dual polarized To perform emitters, as in principle with reference to FIG. 8a is explained. In the following, therefore, the amplitude distribution for the individual radiators of the individual antenna subgroups is shown in each case only for one polarization. In the case of dual-polarized antennas, this generally applies correspondingly to both polarizations, ie to the signals received or transmitted via them. However, it is also possible to apply the amplitude distribution according to the invention only to one polarization or a use of different amplitude distributions according to the invention per polarization.

In addition to the simplified representation of the first and second antenna group 5, 10 in FIG. 1 On the left side, to the right of this, the power or amplitude distribution is now shown for each of the antenna subgroups, on an associated horizontal X-axis. Since in the invention for the reception mode (uplink) of the base station preferably not only the first, but the first and the second antenna group 5, 10 is used, the power and / or amplitude distribution is not only for the first antenna group 5, but also for the second antenna group 10. To the right of this, the power and / or amplitude distribution for the first or lower antenna group 5 is shown, which is used only for the transmission mode, which is why only for the first antenna group 5 a corresponding Amplitude distribution for transmit mode (Tx operation) is present.

As a result, with respect to the antenna subgroups 6 of the first antenna array 5, there is provided a power or amplitude distribution in the receiving mode, alternating between a higher and a lower stage, e.g. between 0 dB and -3 dB. These are signal level levels.

It can also be seen from this diagram that, especially in the central region X, there is now a power or amplitude distribution no longer relatively reduced in the receive mode (uplink) compared with the prior art according to FIG. 8b, but an amplitude distribution with a relatively higher or higher relative Amplitude, so that especially in the critical uplink case, the side-praise (side lobes) are smaller. The resulting radiation pattern for the reception case is in FIG. 12 to see. The comparison with the FIG. 11 , which shows a corresponding diagram for the indicated prior art, illustrates the advantage of the solution according to the invention.

However, in order to produce an optimal radiation pattern also for the downlink case, the invention also proposes that in transmit or downlink mode only one antenna group, in the exemplary embodiment shown, the lower or first antenna group 5 is active while the second or upper antenna array 10 is ineffective for downlink operation, ie no signals are broadcast. In this case, similar to the state of the art, a power tapering is carried out in which a higher relative signal level is applied to the middle antenna subgroups 11 and / or the associated radiators 12 than to the outer or the second last antenna subgroups 11.

Thus, according to the illustration according to FIG. 1, the preferred solution according to the invention results (for example for an antenna array with a first and a second antenna group 5, 10, which respectively comprises five antenna subgroups 6, 11, with one or more radiators in each antenna array). Subgroup), in which for the reception mode for the individual side-by-side radiators in the antenna groups, for example, the basis of FIG. 1 in the middle shows relative amplitude distribution. In the transmission mode, however - in which only the first antenna group and the associated radiators are active - results from the basis of FIG. 1 shown on the right side optimal power distribution across the antenna subgroups, in which the radiators of the central antenna subgroup receive a much higher power or amplitude than those radiators in the outermost or adjacent to the outermost antenna subgroups 6, 11 are arranged.

Based on FIG. 2 is shown for a further embodiment according to the invention, as the relative power or amplitude distribution is set in a first receiving operation associated with the invention.

wodurch sich der treppenförmige Verlauf der Leistungs- oder Amplitudenverteilung in der oberen oder zweiten Antennengruppe 10 im Uplink- oder Empfangsbetrieb ergibt. Dieser Verlauf kann auch, wie bei der ersten Antennengruppe, frequenzabhängig sein. Denkbar wäre dieser Fall zum Beispiel, wenn die zweite Antennengruppe ebenfalls unabhängig von einer anderen Antenngruppe im Sendebetrieb arbeiten soll.The embodiment according to FIG. 2 differs from that according to FIG. 1 in that, for the second antenna group 10, the associated lowermost radiator 12 or the associated lowest antenna subgroup 11, which is connected to a5 in FIG FIG. 2 is characterized and immediately adjacent (above) comes to lie to the marked with a1 first or top antenna subgroup 6 of the first or lower antenna group 5, with respect to all provided in the second antenna group 10 antenna subgroups 11 receives the highest power or amplitude. From this lowest-lying antenna subgroup 11 (which as mentioned with a5 in FIG. 2 characterized by the power or amplitude distribution to the uppermost antenna subgroup 11 (which in FIG. 2 labeled a1) gradually, for example by -3 dB per antenna subgroup. As a result, the relative power or amplitude of the radiators belonging to the innermost or lowest antenna subgroup 11 to the radiators belonging to the outermost or highest antenna subgroup 11 decreases with them FIG. 2 apparent amplitude steps, namely, for example, with the following steps (dB) $$0/-3/-6/-9/-12$$

resulting in the staircase shape of the power or amplitude distribution in the upper or second antenna array 10 in the uplink or receive mode. This course can also be frequency-dependent, as in the case of the first antenna group. This case would be conceivable, for example, if the second antenna group should also operate independently of another antenna group in the transmission mode.

The variants according to FIGS. 1 and 2 should only prove that, in particular with respect to the second antenna array 10 in a wide range of different amplitude distribution is possible, but preferably one in which the amplitude in the lowest antenna subgroup 11 of the second antenna array 10 of the amplitude in the adjacent uppermost antenna subgroup. 6 the first antenna group 5 corresponds. The specified amplitudes are normalized to the maximum. In operation, the amplitudes of the antenna groups via the transceiver unit SE are preferably adjusted so that both antenna groups are fed with substantially the same amplitude. As an equivalent to the reception case, it can also be said that the received signals in the transceiver unit SE are preferably weighted equally.

Based on FIG. 3 a further modification is shown in which the amplitude distribution of the first antenna group 5 for the receive mode (uplink) from the lowest (outer) antenna subgroup (with a5 in FIG. 3 labeled) to the uppermost antenna subgroup 6 (with a1 in FIG FIG. 3 labeled) increases in steps of 3 dB each. Again, the amplitude distribution is made such that the amplitude of the uppermost in this case antenna subset 6 of the first antenna group 5 is equal to the amplitude of the adjacent thereto lowest antenna subgroup 11 of the second antenna array 10. The graduated amplitude curve with respect to Antenna subsets 11 of the second antenna group 10 otherwise corresponds to the course, as it was explained with reference to the embodiment 2.

In the context of the invention, the relative power and amplitude distribution between the antenna subgroups 6 of the first antenna group 5 for the reception mode on the one hand and the transmission mode on the other hand is primarily important. Important here is the proposed in the context of the invention frequency-dependent amplitude distribution for the transmitting and the receiving operation. The amplitude distribution for the second antenna group 10 provided only for the reception mode can have preferred values within the scope of different variants.

gekennzeichnet, wobei diese betragsmäßige Differenz D

• mindestens 0,2 dB multipliziert mit der Anzahl Z der Antennen-Untergruppen 6 der ersten Antennengruppe 5 und
• maximal 5,0 dB multipliziert mit der Anzahl Z der Antennen-Untergruppen 6 der ersten Antennengruppe 5 beträgt, wobei
• A_Rx die relative Amplitude der äußeren oder vorletzten Antennen-Untergruppe 6 bezogen auf die höchste Amplitude der Antennen-Untergruppen 6 der ersten Antennengruppe 5 bei einer Empfangsfrequenz und
• A_Tx die relative Amplitude der äußeren oder vorletzten Antennen-Untergruppe 6 bezogen auf die höchste Amplitude der Antennen-Untergruppen 6 der ersten Antennengruppe 5 bei einer Sendefrequenz ist.

The solution according to the invention is by the amount of the difference $$\mathrm{D}=\left|{\mathrm{A}}_{\mathrm{Rx}}-{\mathrm{A}}_{\mathrm{Tx}}\right|$$

characterized in that this difference in magnitude D

• at least 0.2 dB multiplied by the number Z of the antenna subgroups 6 of the first antenna group 5 and
• is at most 5.0 dB multiplied by the number Z of the antenna subgroups 6 of the first antenna group 5, wherein
• A _Rx the relative amplitude of the outer or penultimate antenna subgroup 6 with respect to the highest amplitude of the antenna subgroups 6 of the first antenna group 5 at a reception frequency and
• A _{Tx is} the relative amplitude of the outer or penultimate antenna subgroup 6 relative to the highest amplitude of the antenna subgroups 6 of the first antenna group 5 at a transmission frequency.

If the difference D is used in the following, it means, as defined above, the respective amount of the difference.

In a preferred embodiment of the invention, however, the lower limit for the aforementioned difference D can also be multiplied by 0.3 dB multiplied by the number Z of the antenna subgroups 6 of the first antenna group 5 or, in some cases, even greater than at least 0.4 dB with the number Z of the antenna subgroups 6 of the first antenna group 5.

Likewise, it may preferably be provided that the upper limit of the difference in question D is a maximum of 4.0 dB or a maximum of 3.0 dB or in some other cases even a maximum of 2.5 dB or even for some applications 2.0 dB each multiplied by the Number Z of the antenna subgroups 6 of the first antenna group 5 be.

If, as above and in the context of the embodiments of "outer" or "penultimate" antenna subgroups 6 (or 11) is spoken, so in the "outer antenna subgroup", for example, in the first antenna group 5 is preferably the lowest (and / or also the uppermost) lying antenna subgroup 6, which is marked in the attached embodiments 1 to 3 with a5 (or a1) and in the embodiments 4 to 7 with a9 (or a1). Thus, the external antenna subgroup is preferably that which is arranged on the side of the first antenna group which is preferably remote from the second or upper antenna group 10. If the penultimate antenna subgroup 6 of the first antenna group 5 is used, this is the adjacent antenna subgroup, which is likewise preferably remote from the second or upper antenna group 10, but optionally also adjacent to it (and therefore into the antenna array) FIGS. 1 to 3 with a4 or a2 and in the FIGS. 4 to 7 marked with a8 or a2).

For the conditions given above, the corresponding values for the first antenna group for the transmission mode and the reception mode are in the FIGS. 1 to 3 wiedergebeben.

The following are based on the FIGS. 4 to 7 some other examples of solutions according to the invention described, namely, for example, an antenna array having a first and second antenna array 5, 10, each comprising nine antenna subgroups 6 and 11, respectively. In the figures, each of the antenna subgroups on the left side is labeled a1 at the top beginning to a9 at the bottom of each antenna group. As in the other embodiments, in the figures to the right of the simplified illustrated antenna array, the associated relative amplitude or power distribution for the individual antenna subgroups and / or for the provided in the antenna subunits emitters first for the receiving operation and again right thereof reproduced the amplitude distribution for the transmission operation, which is handled only on the first (lower) antenna group 5.

FIG. 4 also describes a differently graduated amplitude pattern for the reception mode. In this case, an amplitude distribution over three different level levels takes place such that the outermost antenna subgroups 6 of the first antenna group 5 as well as the outer antenna subgroup 11 of the second antenna array 10 are at a same relative amplitude level. The next-to-last penultimate antenna subgroups also have the same amplitude level but lower by -3 dB.

In the figures, in each case the difference D reproduced above is given for the first antenna group 5, once with respect to the outermost antenna subgroup and secondly with respect to the penultimate antenna subgroup, in each case based on the highest amplitude with respect to a first antenna group 5 The difference is calculated from the relative signal level applied to the respective antenna subgroup in the receive frequency range and the relative signal level applied to the respective antenna subgroup in the transmit frequency range. This difference results in a value of 12 dB or 6 dB.

Furthermore, it is still on the Figures 5 . 6 and 7 referenced the corresponding further modified embodiments show.

Based on the in the FIGS. 1 to 7 explained values for the difference D, the relative values A _Rx and A _Tx and the limits within which the difference D is to move within the scope of the invention, are summarized in the table below. These are for the embodiments according to the FIGS. 1 . 2 and 3 also entered the corresponding values, for the case that the corresponding relative amplitude values are not considered for the respective outer antenna subgroup, but for the penultimate antenna subgroup with respect to the highest amplitude of an antenna subgroup. Given in the following table in the second column, whether the difference D of the amplitude of an outer antenna subgroup A / M relative to a maximum amplitude or of the amplitude of a penultimate antenna subgroup V / M with respect to the maximum amplitude in this antenna group is taken into account.

Based on Figures 9 and 10 Further modifications for an antenna according to the invention are shown, in which also the first and second antenna group each comprise nine antenna subgroups 6 and 11, respectively. The amplitude gradations in this embodiment are for the reception operation across the antenna subgroups as in the embodiment of FIG FIG. 7 executed.

While, however, as with FIG. 7 in that the first antenna group 5 in the transmission mode receives signals via the antenna subgroups whose signal level or amplitude decreases from the central antenna subgroup (marked a5) to the outer antenna groups (marked a1 or a9) in equal stages, shows the embodiment according to FIG. 9 a variant, in which all antenna subgroups 6 are fed with the same signal level or amplitude.

In the embodiment according to FIG. 10 receive in transmission all the antenna subgroups 6 of the first antenna group 5 a same signal level (are fed in the same amplitude), wherein only the antenna subgroups a4 and a6 receive a higher by a 3dB level signal level or higher amplitude. Fig A / MV / M A _rx (dB) A _tx (dB) D (dB) Z min Max 1 AT THE 0 -6 D _1.5 = 6 5 1 25 2 AT THE 0 -6 D _1.5 = 6 5 1 25 3 AT THE 0 -6 D ₁ = 6 5 1 25 3 AT THE -12 -6 D = 6 5 1 25 4 AT THE 0 -12 D _1,9 = 12 9 1.8 45 4 V / M -3 -9 D _2.8 = 6 9 1.8 45 5 AT THE 0 -12 D _1,9 = 12 9 1.8 45 5 V / M -6 -9 D _2.8 = 3 9 1.8 45 6 AT THE 0 -12 D _1,9 = 12 9 1.8 45 6 V / M 0 -9 D _2.8 = 9 9 1.8 45 7 AT THE 0 -12 D ₁ = 12 9 1.8 45 7 V / M -3 -9 D ₂ = 6 9 1.8 45 7 V / M -21 -9 D ₈ = 12 9 1.8 45 7 AT THE -24 -12 D ₉ = 12 9 1.8 45 9 V / M -3 0 D ₂ = 3 9 1.8 45 9 V / M -21 0 D ₈ = 21 9 1.8 45 9 AT THE -24 0 D ₉ = 24 9 1.8 45 10 AT THE 0 -3 D ₂ = 3 9 1.8 45 10 V / M -21 -3 D ₈ = 18 9 1.8 45 10 AT THE -24 -3 D ₉ = 21 9 1.8 45

It can also be seen from the exemplary embodiments explained that the power and amplitude distribution with respect to the antenna subgroups 11 of the upper or second antenna group 10 can also be chosen very differently within wide ranges. Preferably, the amplitude distribution is such that the amplitude of the lowest antenna subgroup 11, which comes to lie in the immediate vicinity of the lower or first antenna group 5, an amplitude or power level, ie an amplitude which is preferably equal to the amplitude of the amplitude top antenna subgroup 6 of the first antenna group 5, although here certain not too large amplitude differences may be provided here. In the illustrated embodiments, however, these amplitude levels of the immediately adjacent antenna subgroups of the first antenna array at the same level, so are fed with the same amplitude. Otherwise, however, the amplitude profile over the antenna subgroups 11 of the second antenna group 6 can also be configured very differently, as can be seen from the exemplary embodiments.

However, in all these variants, it is preferred that in receive mode, in which both antenna groups 5, 10 are used, the receive signals of both antenna groups 5, 10 in the transceiver SE, ie in the receiver or receiver, for example in the form of a remote radio Heads or the like, via modern methods such as MRC (Maximum Ration Combining) or ERC (Equal Ratio Combining) or similar methods such as IRC or the like can be combined. The individual signals are weighted and corrected in amplitude and phase and optimally combined with each other. Thus, the result can also be expressed as a combined antenna program.

In the illustrated embodiments, amplitude gradations of, for example, 3 dB have been used. Of course, arbitrary other amplitude gradations can also be used here, for example gradations of 2 dB, 1.5 dB or even in gradations that have at least partially different values from stage to stage. The amplitude gradation between two adjacent antenna subgroups will generally have a value between 1 dB and 4 dB, in particular between 2 dB and 3 dB.

It should also be noted that the mentioned phase shifters or phase shifter assemblies 15 are preferably mechanical phase shifters which are in particular electrically adjustable. Thus, therefore, a different reduction (downtilt) with respect to the first Antenna group 5, but also with respect to the second antenna group 10 are made. Preferably, the Downtilseinstellung the first and second antenna group 5, 10 is coupled together. It is also possible via the transmitting and receiving unit to adjust or readjust the downtilt in the reception frequency range separately.

The mentioned phase shifter 15 serve not only to adjust the vertical radiation pattern, but preferably also allow a frequency-dependent power distribution. In other words, the phase shifters for transmit or downlink operation (Tx) have a different power split than for receive or uplink operation (Rx). The frequency-dependent amplitude distribution is in this case carried out generally in the feed network N11, N12, N21 or N22, wherein, as mentioned, the frequency-dependent amplitude distribution can preferably be realized by the mentioned phase shifters, in particular in the form of the mechanical phase shifters. However, it is also possible to realize the frequency-dependent amplitude distribution via a frequency-dependent power divider or only via the corresponding feed network in the form of a so-called distributed system in which frequency-dependent impedances in or through lines are realized. The phase shifter is therefore not absolutely necessary for the invention and represents a preferred embodiment. Without a phase shifter one could also create a variant of this system with unchangeable or only conditionally changeable downtilt (only in the reception frequency range through the SE).

For both uplink and downlink operation, the phase shifters can be set so that the resulting electrical radiation patterns allow the same vertical lowering (the same electric downtilt) or a different vertical lowering (electrical downtilt).

The electronics explained in the context of the invention are designed such that at least two antenna groups 5, 10 are provided for the uplink or receive operation and an antenna group 5 for the transmit or downlink operation and the receive or uplink operation (or a multiple thereof). It is also possible, for example, that further antenna groups are provided for the uplink operation, for example three antenna groups for the uplink operation (of the three antenna groups only one antenna group is additionally used for the downlink operation).

Furthermore, it is again pointed out that applications are also conceivable in which both antenna groups are used in the transmission mode. Thus, in particular, for example, an intelligent method such as MIMO, SIMO or MISO can be used, just as the common operation of the antennas in downlink mode is possible, for example to achieve a higher antenna gain. The above-mentioned methods MIMO, SIMO or MISO are known to be used in telecommunications to use multiple transmit and receive antennas for wireless communication, where the MIMO technique involves the use of multiple transmit and receive antennas, the SIMO technique involves the use of a transmit and multiple receive antennas, and MISO technique is a transmit that involves multiple transmit antennas but only one receiving antenna can be used.

The invention has been described with reference to antenna arrays which operate with so-called X-polarized radiators, that is to say dual-polarized radiators. As mentioned, but it can also be simply polarized radiator. In particular, when using dual-polarized radiators, it is also possible that the amplitude distribution of the invention is applied only to one polarization or even the use of different amplitude distributions according to the invention per polarization comes into play.

Finally, but also completely different embodiments and modes with different level differences are possible. For this purpose, reference is also made to the following additional table. n these are called further level differences that are useful for the operation of the antenna system according to the invention. In the first column the respective operating modes are named according to the figures. The columns A _Rx and A _{Tx represent} amplitudes, as they may be useful in addition to the already mentioned embodiments. The level differences arise accordingly.

The illustrated active antenna system has been described generally. In other words, the active antenna system with the corresponding antenna groups and the antenna subgroups belonging to the individual antenna groups and the radiators or radiators belonging to the individual antenna subgroups can in principle be used for a single-column antenna system as well as for a two-column or generally multi-column antenna system Find.

That is, the described and claimed active antenna system may be provided in a column. Likewise, however, corresponding active antenna systems can also be designed and / or provided in a second, a third or generally a plurality of further columns. In all these cases, the antenna gaps are usually oriented so that they either extend in the vertical direction or slightly inclined relative to the vertical, that is at an angle of preferably less than 45 °, in particular less than 30 °, 15 °, 10 ° and in particular 5 °. Embodiment according to FIG A _Rx / dB A _Tx / dB D / dB 1 0 -2 D _1.5 = 2 1 0 -4 D _1.5 = 4 2 0 -2 D _1.5 = 2 2 0 -4 D _1.5 = 4 3 0 -2 D ₁ = 2 3 -4 -2 D ₅ = 2 3 0 -4 D ₁ = 4 3 -8th -4 D ₅ = 4 4 0 -4 D _1,9 = 4 4 0 -8th D _1.9 = 8 4 -1 -4 D _2.8 = 3 4 -2 -8th D _2.8 = 6 5 0 -4 D _1,9 = 4 5 0 -8th D _1,9 = 8 5 -2 -4 D _2.8 = 2 5 -4 -8th D _2.8 = 4 6 0 -4 D _1,9 = 4 6 0 -8th D _1,9 = 8 6 0 -4 D _2.8 = 4 6 0 -8th D _2.8 = 8 7 0 -4 D ₁ = 4 7 0 -8th D ₁ = 8 7 -1 -3 D ₂ = 2 7 -2 -6 D ₂ = 4 7 -7 -3 D ₈ = 4 7 -14 -6 D ₈ = 8 7 -8th -4 D ₉ = 4 7 -16 -8th D ₉ = 8 9 -1 0 D ₂ = 1 9 -2 0 D ₂ = 2 9 -7 0 D ₈ = 7 9 -14 0 D ₈ = 14 9 -8th 0 D ₉ = 8 9 -16 0 D ₉ = 16 10 0 -1 D ₁ = 1 10 0 -2 D ₁ = 2 10 -7 -1 D ₈ = 6 10 -14 -2 D ₈ = 12 10 -8th -1 D ₉ = 7 10 -16 -2 D ₉ = 14

Claims (23)

1. Active antenna system, having the following features:

   - comprising a first antenna group (5) which is provided for transmitting and receiving operation,

   - comprising a second antenna group (10) which is provided for receiving operation,

   - the two antenna groups (5, 10) are arranged above one another,

   - each antenna group (5, 10) comprises at least two antenna subgroups (6 or 11), the first antenna group (5) comprising at least two antenna subgroups (6) each comprising at least one radiator (7) and the second antenna group (10) comprising at least two antenna subgroups (11) each comprising at least one radiator (12),

   - the antenna subgroups (6, 11) of an antenna group (5, 10) are interconnected via a supply network (N11, N12; N21, N22) in each case,

   - the supply networks (N11, N12; N21, N22) are constructed in such a way that phases and amplitudes are provided for each antenna subgroup (6, 11), the supply networks (N11, N12; N21, N22) comprising phase shifters (15), and

   - the antenna groups (5, 10) are connected to a shared transmitting and receiving unit (SE),

   characterised by the following further features

   - the supply network (N11, N12) of the first antenna group (5) has an amplitude distribution which is frequency-dependent, i.e. a different amplitude distribution for a transmitting and a receiving frequency,

   - the supply network (N11, N12) of the first antenna group (5) is constructed in such a way that the following condition is met $$\mathrm{Z}*0.2\mathrm{dB}\le \left|{\mathrm{A}}_{\mathrm{Rx}}-{\mathrm{A}}_{\mathrm{Tx}}\right|\le \mathrm{Z}*5.0\mathrm{dB}$$

   

   wherein

   - A_Rx is the amplitude of the outer antenna subgroup (6) on the basis of the maximum amplitude of the antenna subgroups (6) at a receiving frequency, and A_Tx is the amplitude of the outer antenna subgroup (6) based on the highest amplitude of the antenna subgroups (6) at a transmitting frequency, the outer antenna subgroup (6) being the outer antenna subgroup (6) that is not adjacent to, but rather remote from, the second antenna group (10), or
   A_Rx is the amplitude of the penultimate antenna subgroup (6) on the basis of the maximum amplitude of the antenna subgroups (6) at a receiving frequency, and A_Tx is the amplitude of the penultimate antenna subgroup (6) based on the highest amplitude of the antenna subgroups (6) at a transmitting frequency, the penultimate antenna subgroup (6) being the penultimate antenna subgroup (6) that is not adjacent to, but rather remote from, the second antenna group (10),

   - Z is the number of antenna subgroups (6) of the first antenna group (5),

   - the antenna subgroup (11) of the second antenna group (10) and the antenna subgroup (6) of the first antenna group (5) that are located in the direct vicinity of one another have the same amplitude,

   - the antenna subgroup (11) of the second antenna group (10) that is directly adjacent to the first antenna group (5) obtains the highest amplitude in relation to all of the antenna subgroups (11) which are provided in the second antenna group (10),

   - the antenna subgroups (6, 11) comprise an equal number of radiators (7, 12),

   - the antenna system is configured in such a way that the first and second antenna groups (5, 10) are used in receiving operation, and

   - the antenna system is configured in such a way that only the first antenna group (5) is used in transmitting operation.
2. Antenna system according to claim 1, characterised in that a transmitting and receiving unit (SE) is provided which is constructed in such a way that the signals which are received via the at least two antenna groups (5, 10) are processed by an MRC, ERC or IRC method.
3. Antenna system according to either claim 1 or claim 2, characterised in that mechanical phase shifters (15) are provided as phase shifters (15).
4. Antenna system according to any one of claims 1 to 3, characterised in that the supply network (N11, N12; N21, N22) comprises frequency-dependent power splitters.
5. Antenna system according to any one of claims 1 to 4, characterised in that the phase shifters (15), preferably in the form of mechanical phase shifters (15), have a frequency-dependent power share for setting the radiation downtilt.
6. Antenna system according to any one of claims 1 to 5, characterised in that the antenna system comprises at least three antenna groups (5, 10), three antenna groups (5, 10) being provided for the receiving operation and one antenna group (5) being provided for the transmitting operation.
7. Antenna system according to any one of claims 1 to 6, characterised in that the antenna groups (5, 10) comprise an equal number of antenna subgroups (6, 11) and/or the antenna subgroups (6, 11) comprise an equal number of radiators (7, 12), namely two radiators (7, 12) in each case.
8. Antenna system according to claim 7, characterised in that the radiators (7, 12) of an antenna subgroup (6, 11) are supplied with a phase difference.
9. Antenna system according to any one of claims 1 to 8, characterised in that the antenna system comprises an electrically adjustable radiation downtilt means which comprises phase shifters (15).
10. Antenna system according to claim 9, characterised in that a plurality of radiation downtilt means are provided, and that the radiation downtilt means of the antenna groups (5, 10) are interconnected.
11. Antenna system according to any one of claims 1 to 10, characterised in that the antenna system can be operated by means of the transmitting and receiving unit (SE) and/or the supply networks (N11, N12; N21, N22) in such a way that the resulting electrical radiation diagram for the receiving and transmitting operation (Rx, Tx) can be set to a different vertical downtilt, in particular by setting the different phase shift and/or a different power division between the receiving and the transmitting operation (Rx, Tx).
12. Antenna system according to any one of claims 1 to 10, characterised in that the antenna system can be operated by means of the transmitting and receiving unit (SE) and/or the supply networks (N11, N12; N21, N22) in such a way that the resulting electrical radiation diagram can be set to an equal vertical downtilt for the receiving and the transmitting operation (Rx, Tx).
13. Antenna system according to any one of claims 1 to 12, characterised in that the second and/or third antenna group (10) corresponds to the first antenna group (5), in particular in that the antenna groups are of the same type.
14. Antenna system according to any one of claims 1 to 13, characterised in that the radiators (7, 12) of the antenna subgroups (6, 11) of the antenna groups (5, 10) are dual-polarised, in particular linearly (± 45°, horizontally or vertically), circularly (left-handed or right-handed) or elliptically.
15. Antenna system according to claim 14, characterised in that the antenna system is constructed in such a way that a different frequency-dependent power distribution is implemented or used for only one of the two polarisations, or in such a way that a different frequency-dependent power distribution is implemented or used for each of the two polarisations of the dual-polarised radiators (7, 12).
16. Antenna system according to any one of claims 1 to 15, characterised in that the antenna system is constructed in such a way that the antenna subgroups (6) of the first antenna group (5) are operated in transmitting operation at a different power, a central antenna subgroup (6) preferably being supplied with the highest amplitude, whilst the amplitudes decrease in steps to the outermost antenna subgroups (6), the change in amplitude from an antenna subgroup (6) to an adjacent antenna subgroup (6) preferably being between 1 dB and 4 dB.
17. Antenna system according to any one of claims 1 to 15, characterised in that the antenna system is constructed in such a way that when the first antenna group (5) is in transmitting operation, the antenna subgroups are supplied with approximately the same power or amplitude or only individual antenna subgroups (6) receive more power than the remaining antenna subgroups.
18. Antenna system according to any one of claims 1 to 17, characterised in that the antenna system is constructed in such a way that the power or amplitude distribution of the antenna subgroups (6) of the first antenna group (5) is symmetrical about a central antenna subgroup (6) or two central antenna subgroups (6) in receiving operation and/or in transmitting operation, and/or in that approximately the same power or amplitude distribution is used.
19. Antenna system according to any one of claims 1 to 17, characterised in that the antenna system is constructed in such a way that in receiving operation the antenna subgroup (6), which is provided immediately adjacent to the second antenna group (10), of the first antenna group (5) is operated at the highest power or amplitude, and in that each subsequent antenna subgroup (6) of the first antenna group (5) up to the outermost antenna subgroup (6), which is the furthest away from the second antenna group (10), obtains lower power or amplitude values in steps.
20. Antenna system according to claim 19, characterised in that the amplitude distribution of the antenna subgroups of the second antenna group at a receiving frequency is selected in such a way that the overall amplitude distribution of all of the antenna subgroups of the two antenna groups at a receiving frequency substantially corresponds to a progression which decreases from the inner to the outer antenna subgroups, as considered over the antenna system as a whole.
21. Antenna system according to any one of claims 1 to 18, characterised in that the amplitude distribution in relation to the antenna subgroups (6) of the first antenna group (5) corresponds to the amplitude distribution of the antenna subgroups (11) of the second antenna group (10).
22. Antenna system according to any one of claims 1 to 21, characterised in that the amplitude of the antenna subgroup (6) of the first antenna group (5) directly adjacent to the second antenna group (11) has a value which corresponds to the amplitude of the lowest antenna subgroup (11) of the second antenna group (10).
23. Antenna system according to any one of claims 1 to 22, characterised in that the supply network (N11, N12) of the first antenna group (5) is constructed in such a way that the following condition is met $$\mathrm{Z}*\mathrm{x\; dB}\le \left|{\mathrm{A}}_{\mathrm{Rx}}-{\mathrm{A}}_{\mathrm{Tx}}\right|\le \mathrm{Z}*\mathrm{y\; dB}$$

    

    wherein x corresponds to a value of 0.3 and/or preferably 0.4, and y corresponds to a value of 4.0 or 3.0 or preferably 2.5 or 2.0.

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