Radio station for transmitting and receiving digital information in a mobile communications system

The invention relates to a radio station for transmitting and receiving digital information in a mobile communication system according to the preamble of claim 1.

Radio stations are used to transfer information with the aid of electromagnetic waves. The frequency spectrum of the possible electromagnetic waves from a few kHz up to several hundred GHz, with in particular the frequency spectrum won in the lower gigahertz by the development of mobile communications technology in importance. So radio stations for mobile communications technologies is about 0.9 and 1.8 GHz are used. A mobile communication system is, for example, the GSM mobile network (GSM), but well-known wireless communication networks, for example according to the DECT standard, realize such a mobile communication system.

Are these radio stations provided for this purpose, to send information as well as to receive, they comprise at least one receiving unit and at least one transmitting unit. In the transmitting unit, the information to be transmitted are modulated onto a carrier frequency and amplifies the generated transmission signals. The receiving unit is used to analyze the information of the received signals and their separation from the carrier and noise disturbances.

Such radio station is known, for example as a base station of the German Patent Application 195 472 88.8. These radio station further includes an antenna for transmitting and receiving. So this antenna both the transmission signals are sent, as well as receive the reception signals. However, this radio station has the disadvantage that no diversity reception is possible.

From the publication "teleprinter and data transmission on shortwave," L. Wiesner, Siemens Aktiengesellschaft, third edition, 1980, pages 94 to 104, different ways of implementing a diversity reception are known. Among other things, the possibility of polarization diversity is presented in which the diversity reception of two antennas are used, one of which, for example, and the other is vertically polarized horizontally. Such antenna system is also known from German Patent DE 2032002 B2. These writings present realizations of the diversity reception, however, are based on spatially separated antennas and also does not consider the problem of the transmission mode.

Conventional mobile communication systems, see Siemens Function Specification, A30862-X1001-A314-03-7659, MOBNET, from 25.08.1995, S.5-2, realize a radio station with diversity operation also in that separate antennas for transmission and for each diversity branch are present. However, the two antennas for the diversity reception must have a certain spatial separation, to ensure de-correlation of the received signals. Another possible embodiment provides the duplex transmit signals to the antennas for diversity reception vor.-but has also a spatial separation of the antennas are present for diversity reception.

From US 5,262,788 a data transmission is known, the send and receive sides antennas used with two different polarized excitation systems, which produce a polarized signal according to certain criteria or evaluate. With respect to the polarization and other signal parameters, the signal processing means of the reception side are matched to the signal generating means of the transmitting side. A diversity reception is not possible.

From EP 0642232 A1 a radio station with a plurality of exciter systems is known, wherein a transmission side provided excitation system is spatially separated from the receiving end provided excitation systems.

From US 4,704,733 a device for expansion of a radio cell is known. It is a signal of a "subscriber", which is received via two antennas of the device, passed through two signal paths to an antenna with two different polarizations for transmission to a base station.

In current mobile communications systems, however, there is considerable pressure on the operators to make do with a few antenna sites. Here, the provision of two separate antennas for diversity reception at a considerable disadvantage.

The invention is therefore based on the object to provide a radio station for transmitting and receiving digital information in a mobile communication system that for transmission and diversity reception has a small footprint for the antenna site. This object is solved by the inventive radio station of claim 1, starting from the features of the preamble by the features of characterizing portion. Advantageous further developments are specified in the dependent claims.

According to the invention, the antenna comprising a first and second exciter system with different polarization. To share the antenna for transmitting and receiving a first duplexer connects at least a first transmitter and a first receiver unit with a common first antenna line. The first excitation system is connected via the first antenna line to the first duplexer. The second exciter system comprises a connection to at least the first receiving unit via a second antenna line. This is at least the first Em a diversity reception pfangseinheit and both excitation systems ensured. Furthermore, the transmission is realized by digital information at least on the first excitation system.

Alternatively, at least three excitation systems, two for receiving and one for transmitting provided in the antenna, wherein the exciter systems differ by their polarization planes. Through this solution, the duplexer can be saved, however, it results in increased expenses for the realization of Antennne.

The radio station according to the invention advantageously fulfills simultaneously the demand for a reduction in the number of antennas and the requirements of a mobile communications system with diversity reception. This makes it possible to network operators to meet strict requirements, eg on optical and aesthetic effects of the antenna system, especially in conurbations.

According to advantageous developments, the first and second excitation system have a common geometric center. By such an arrangement of the exciting systems, the space requirement of the antenna can be further reduced. For a high antenna gain can be used for excitation systems advantageously member groups. By appropriate arrangements of the elements of the excitation systems can be without great additional expense to generate radiation patterns of different polarization realize.

It is also possible to integrate other excitation systems in this antenna, according to advantageous developments of the radio station of the invention, these additional exciter systems are used either for diversity reception or sending.

Is to take place not only on an excitation system, the radiation of the transmission signals, a further advantageous embodiment of the radio station of the invention provides for the connection of the second exciter system to the first receiving unit of a second duplexer, said second duplexer, a second transmission unit and the first receiving unit to the common second antenna line connects. According to various implementation options can thus be distributed or several transmitter units are each connected to an excitation system, the transmission power of a transmitter unit in two excitation systems.

If a plurality of receiving units are used in the radio station, it is advantageous to connect them respectively to a first and second isolating amplifier (with two excitation systems) and to distribute through the isolation amplifier the power of the signals received by the two exciter systems receiving signals corresponding to the receiving units. Through the use of isolation amplifiers, a larger number of receiving units are used.

According to further advantageous refinements of the radio station of the invention and in particular the antenna, the exciter systems are arranged such that the cross-polarization decoupling of the exciter systems is at least 30 dB. This decoupling corresponds to the decoupling of two antennas, one meter at 900 MHz. This measure is intended to ensure that the interaction between the sending and receiving excitation systems are low. A high cross polarization coupling is for example achieved by the polarization plane of the first and second exciter system are inclined toward each other about 90 degrees. The inclination of the planes of polarization of both Brregersysteme compared to the horizontal can be set to a variety of ways. it, both planes of polarization tilt about 45 degrees to the horizontal, so that they are after several reflections on the radio link or by direct propagation path equal at the receiving radio station is particularly advantageous. A further advantageous variant embodiment provides that the polarization plane of the transmission signals radiating excitation system is approximately perpendicular to the horizontal. This tendency corresponds to the usual arrangements of transmit antennas.

To connect a large number of transmission units Leistungskombiner are advantageously used, each connecting a plurality of transmitting units to a duplexer or directly with an excitation system. If a plurality of transmission units used and the losses of the transmission of the transmission power of the transmission signals can be kept low to the exciting systems, the invention is directed to Leistungskombiner is according to an advantageous further dispensed by a further antenna is added, the exciter systems for transmitting or for improving the diversity be receiving utilized.

The radio station according to the invention is illustrated below with the aid of graphic representations.

It shows<dl id="dl0001"><dt>1 shows</dt><dd>a radio station with two in each case by 45 degrees inclined to the horizontal exciter systems and four transmitting and receiving units,</dd><dt>FIG 2</dt><dd>a radio station with two mutually inclined by 90 degrees excitation systems and the vertical plane of polarization of the emitted transmission signals,</dd><dt>FIG 3</dt><dd>a radio station with a four exciter systems having antenna, and</dd><dt>FIG 4</dt><dd>a radio station with two antennas and four respectively connected to a transmitter unit exciter systems.</dd></dl>

The radio station FS of Figure 1 consists of an antenna A, four receiving units RX1..4 and four transmitting units TX1..4. The transmission signals tx of the first and second transmission unit TX1, TX2 are combined by a first Leistungskombiner H1 and fed to a first duplexer DX1. Accordingly, the transmission signals are tx the third and fourth transmitter TX3, TX4 summarized by a second Leistungskombiner H2 and fed to a second duplexer DX2. The Leistungskombiner H1, H2 realize the adapted transmission of transmitting power to the duplexers DX1, DX2.

Each of these duplexers DX1, DX2 has a connection to a first isolation amplifier FRX1 and a second isolation amplifier FRX2. This isolation amplifier FRX1, FRX2 output side are connected to four receiving units RX1..4. In isolation amplifier FRX1, FRX2 a broadband-ended filtering according to the system bandwidth takes place and there is a renewed reinforcement before the power of the received signals rx equally among all receiving units RX1..4 is distributed. In the receiving units RX1..4 the evaluation of the received signals RX follows a diversity method. Known diversity reception method is for example JGProakis, "Digital Communications", McGraw Hill, 1989, referenced.

The first and second duplexers DX1, DX2 connects the transmitting units and receiving units DX1..4 RX1..4 with a first and second antenna line Ltg1, Ltg2. This antenna cables Ltg1, Ltg2 lead to antenna A. This antenna A comprises two exciter systems AE1, AE2. The first excitation system AE1 is the first antenna line Ltg1 and the second exciter system AE2 is connected to the second antenna line Ltg2. Both excitation systems AE1, AE2 are approximately 45 degrees to the horizontal of the earth and mutually inclined by about 90 degrees. Accordingly, the polarization planes of their radiation directions are inclined. The excitation systems are, for example to array antennas, each consisting of several individual elements.

The radio station FS of FIG 2 is again RX..4 from an antenna A, four transmission units TX1..4 and four receiving units. The combination of the transmit powers of the transmission signals TX to the four transmitting units TX1..4 takes place but in contrast to the radio station FS of Figure 1 in another way. After combining the transmission signals of the first and second transmission unit TX1, TX2 tx in a first Leistungskombiner H1 and the combination of the transmission signals tx the third and fourth transmitter TX3, TX4 in a second Leistungskombiner H2 these transmission signals tx again in a third Leistungskombiner H3 summarized and only supplied to the first duplexer DX1. The second duplexer DX2 is completed adapted sending unit side. The connection of the receiver units RX1..4 carried out according to the arrangement of the receiving units RX1..4 of Fig. 1

The connection of the first and second exciter system AE1, AE2 of the antenna A again takes place via a first and second antenna line Ltg1, Ltg2 to the first and second duplexers DX1, DX2. The first excitation system AE1 is arranged perpendicular to the horizontal and inclined 90 degrees to the second exciter system AE2. Thus, the radiating diagram of the transmission signals TX to a vertical polarization. As in FIG 1, the reception signals rx received in two polarization planes. By this arrangement, the exciter systems AE1, AE2 a polarization diversity reception, as well as the radio station FS of FIG 1, implemented.

The radio station according to FS 3 shows a possible realization according to the invention, the antenna A comprises four excitation systems AE..4. These are inclined exemplified respectively to each other about 45 degrees, but it could be used on a different number of excitation systems with different type of inclination. A first excitation system AE1 is connected to a first isolation amplifier FRX2 and a second exciter system AE2 is connected to a second isolation amplifier FRX1. Both isolation amplifier FRX1, FRX2 are each connected to a first and second receiving unit RX1, RX2 and run two respectively received by the first and second excitation system AE1, AE2 reception signals rx to. A first and a second transmission unit TX1, TX2 are connected directly to a third and fourth excitation system AE3, AE4. In this embodiment can be dispensed with and Leistungskombiner duplexer. However, it would also be possible to combine the services of the first and second transmitting unit TX1, TX2 and a single excitation system. supply AE3 and to renounce the fourth excitation system AE4.

The radio station FS of FIG 4 but guaranteed with increased space requirements to significantly reduce the attenuation of the transmitted signals tx. There are by the use of two separate antennas A with two example cross-polarized excitation systems AE1, AE2 the Leistungskombiner saved, for the same output power of the transmitter units TX1..4 enables higher power radiation of the radio station FS. The exciter systems of the additional antenna A are used for diversity reception, so is also a possible triple diversity and for sending the transmission signals TX from two transmitter units TX1, TX2 used. The distribution of the use of the exciter systems AE1, AE2 of the two antennas A, however, can also take place in other ways, according to the invention here are different variants according to the specific requirements of the space required and the transmission power possible.

For the radio stations FS according to the Figures 1 to 4, the antenna lines Ltg1, Ltg2 also to a single or to a number that is less than that of the exciter systems AE1..4 be reduced by duplexes.