REPEATER-SYSTEM

Description

The invention relates to a repeater for forwarding radio signals

[0001] To meet the demand for ever-increasing data rates in wireless networks, millimeter-wave frequencies are currently being investigated, and it has already been confirmed that these frequencies will be used in the successor standard to LTE (5G). Applications for these frequencies range from fixed wireless access (FWA) to typical mobile networks.

[0002] Mobile network coverage in the millimeter wave range is more limited than with conventional mobile frequencies. For example, free-space attenuation at 28 GHz is 20 to 30 dB higher than with conventional mobile frequencies. In addition, there are significantly higher propagation losses due to vegetation and high penetration losses through building materials such as glass and concrete. Further complicating the situation is the fact that propagation around house corners or over rooftops is not possible in this frequency range due to high diffraction losses (see "Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!" by Theodore S. Rappaport et al., IEEE Access, vol. 1, pp. 335-349, 10 May 2013).

[0003] Furthermore, the performance of available analog hardware is limited (see 3GPP Technical Report No. 38.803 - v 14.2.0 from September 2017). The radiated power on the transmitter side is limited, in particular, by the efficiency of the power amplifiers. On the receive side, high line losses and the available LNA (low-noise amplifier) ​​technology limit the noise figure. This means that a nationwide network must be built with a denser mesh, which leads to increased costs (CAPEX and OPEX).

[0004] One solution to cost-effectively increase network coverage is the use of repeaters or relay technologies. Repeater functionality is already known from GSM, UMTS, and LTE networks (see 3GPP Technical Specifications TS 25.106, 25.107, 25.113, 25.116, 25.143, 25.153, 36.106). During the development of LTE-A, so-called relay nodes were also introduced in 3GPP Release 10 (3GPP TS 36.116, 36.117, 36.216).

[0005] Given the above-mentioned background, a solution to the network coverage problem, including in the millimeter wave range and future mobile communications standards, using repeaters is desirable. However, precisely because of the restrictions described above, concrete solutions pose a particular technical challenge that cannot be addressed with the current state of technology.

[0006] Repeaters for forwarding radio signals are known in the art. The repeater receives radio signals from a transmitter at a transmission frequency from one direction, amplifies the signals, and radiates the received radio signals in another direction. An example of such a repeater is shown in US Patent US7,577,398 B2 (Andrews LLC), which discloses a repeater with a housing having two opposite surfaces. At least one antenna is mounted on each of the two opposite surfaces, and the antennas radiate radio signals in opposite directions. Within the housing, a circuit is provided that forwards the signals between one of the antennas and the other antenna.

[0007] The repeater system described in this document is suitable, for example, for supplying the interior of a building. Several patent documents are known for supplying wireless networks within buildings. For example, US patent no. US 6,374,119 B1 (Jun et al.), international patent application no. WO 98 / 54844 (LGC Wireless), European patent no. EP 1 224 821 B1 (Qualcomm), and German patent application no. DE 10 2015 011 875 A1 (Kathrein) demonstrate such a system.

[0008] Figuren 1 and 2represent the typical structure of state-of-the-art repeater solutions. The repeater 10 has a donor antenna 40 and a service antenna 50. The donor antenna 40 receives signals from a base station 20, and the service antenna 50 transmits radio signals to a mobile station 30, such as a smartphone or tablet. The donor antennas 40 and the service antennas 50 connected to the repeater 10 can be installed at greater or lesser distances from the repeater 10, depending on the specific situation at the installation site.

[0009] In such cases, the donor antennas 40 and the service antennas 50 are connected to the repeater 10 via coaxial cables 45 and 55. The coaxial cables 45 and 55 used for this purpose are known to exhibit frequency-dependent signal attenuation, which increases with increasing frequencies and cable length (see https: / / de.wikipedia.org / wiki / Koaxialkabel).

[0010] The repeater itself contains two transmission paths. The upper transmission path in these figures includes a low-noise downlink amplifier 110, a downlink bandpass filter 120, and a downlink power amplifier 130 in a downlink (DL) path. The lower transmission path is the uplink (UL) path and includes a low-noise uplink amplifier 160, an uplink bandpass filter 170, and an uplink power amplifier 180. The donor antenna 40 is connected to a first duplexer 100, which selects the downlink path or the uplink path via filter separation in Frequency Division Duplex (FDD) operation. The service antenna 50 is connected to a second duplexer 150, which also selects between the downlink path and the uplink path via a filter function in FDD operation.

[0011] In Fig. 2 A similar embodiment according to the prior art is shown, this embodiment being a time division duplex implementation. Here, the first duplexer 100 is replaced by a first switch 105 and the second duplexer 150 by a second switch 155. The other components are the same as the elements in Fig. 1 and have the same reference numerals.

[0012] In Figur 3 is shown in a highly simplified manner, showing where in the system the signal attenuation (ATT) of the coaxial lines 45, 55 comes into play as a function of frequency (f) and cable length (l). The signal attenuation also scales with the diameter of the cable used in the coaxial lines 45, 55. As the diameter (d) decreases, the attenuation of the coaxial lines increases. These line-borne losses are approximately 160 dB / 100 m at a useful frequency of, for example, 28 GHz. With a typical repeater gain of 50 dB, a total cable length of approximately 32 m from the donor antenna 40 to the repeater 10 and further to the service antenna 50 would already attenuate the entire signal amplification back to the level received at the donor antenna. The installation of a repeater system, which is advantageous in terms of signal amplification, as is common, for example, on building roofs and at road intersections, cannot be carried out in this way or can only be carried out to a limited extent.

[0013] US 2019 / 020401 A1 discloses an active repeater device comprising a primary sector and one or more secondary sectors and receiving a first beam of input RF signals. A first set of analog baseband signals is generated based on the received first beam of input RF signals. The first set of analog baseband signals is converted into a first set of encoded data signals, and control information is extracted from the first set of encoded data signals by decoding only a header portion of the first set of encoded data signals without demodulating the data portion of the first set of encoded data signals.

[0014] KR 2004 0092621 A discloses a notch relay system for converting RF signals into IF frequency band signals by separating a repeater into a donor repeater and a service repeater, thereby minimizing signal transmission loss. A donor antenna (302) is installed to transmit and receive RF (radio frequency) signals to and from a BTS (base transceiver station) (102). A service antenna (308) is installed to transmit and receive other RF signals to and from a subscriber device (110). A donor repeater (304) converts the RF signals into first intermediate frequency signals and converts second intermediate frequency signals into the RF signals transmitted by the donor antenna (302).A service repeater (306) is connected to the donor repeater (304) via a cable and converts the RF signals received via the service antenna (308) into the second intermediate frequency signals to transmit the converted second intermediate frequency signals to the donor repeater (304) and converts the first intermediate frequency signals into the RF signals transmitted by the service antenna (308).

[0015] US 2012 / 188919 A1 discloses a method for determining the isolation status of an RF repeater. A modem in the repeater registers with a base transceiver station (BTS). The uplink output levels of a donor RF transceiver are calibrated and stored in the modem. The modem is synchronized with a BTS transmission received at the donor RF transceiver, and the synchronization information is transmitted to a server RF transceiver of the repeater. Isolation detection and measurement can then be performed between the donor transmit antenna and the receive server antenna of the RF repeater, and the automatic gain control parameters of the donor RF transceiver and the server RF transceiver are adjusted based on the isolation detection and measurement.

[0016] The invention is therefore based on the object of developing an improved repeater system. To achieve this object, the repeater system according to claim 1 is provided.

[0017] The separation of the antennas is necessary for a repeater that transmits the radio signals in TDD mode, from the Fig. 1 and 2 The state of the art shown is not known. As can be seen from the Fig. 2 As is well known, repeaters in a TDD design require multiple switches to switch the antennas between the signals on the transmission paths (uplink path and downlink path). These switches cause significant insertion loss in the centimeter and millimeter wave range, which has a very detrimental effect on the overall performance of the repeater system. However, the repeater system in this document does not have an internal synchronization signal to control the switches, and this synchronization signal would otherwise have to be generated from the received radio signals. The separate antennas eliminate the need for deriving or generating the synchronization signal.

[0018] According to the 5G standard, the frames in a radio signal do not have a fixed time grid and therefore no predetermined frame length, which further complicates switching between the transmission paths and thus the synchronization of the radio signals with a single, split donor antenna. Separating the antennas also avoids delays in signal transmission due to the switching times otherwise required for the switches and the derivation of the synchronization signal. Beam steering, which is used in 5G transmissions, can pose an additional challenge for synchronization, as this means that the base station signals are not always available, but only when the beam is pointing at the repeater system (10).

[0019] In one aspect, the repeater system comprises additional service units and a plurality of cables, each of which connects the donor unit and the other service units and transmits the converted radio signals over a distance between the donor unit and the connected, additional service units. These additional service units are adapted, for example, such that the service units can transmit and receive radio signals in different directions and serve different, possibly overlapping, sectors to enable largely complete coverage of the serviced area. During operation, the service units can transmit and receive radio signals at different transmission frequencies.

[0020] The decoupling between the uplink donor antennas and the downlink donor antenna should be at least 40 dB, and preferably 60 dB.

[0021] In the inventive aspect of the repeater system, the gain of the donor downlink amplifier is adjustable and is set such that the sum of the total gain between the donor downlink antenna and the service uplink antenna is less than the decoupling between the donor uplink antenna and the service downlink antenna. Oscillations in the repeater system are thereby avoided.

[0022] In order to reduce the energy consumption of the repeater system, the gain of the respective amplifiers of the downlink path in the donor unit and / or server unit in a TDD system can be switched off or the gain reduced at the time when no useful signal is passing through this amplifier.

[0023] The invention will now be explained in more detail with reference to the figures. They show: Fig. 1 a first example of a state-of-the-art repeater system in an FDD design; Fig. 2 a second example of a state-of-the-art repeater system in TDD design; Fig. 3 an explanation of the losses in coaxial cables; Fig. 4A-4F several aspects of the repeater system; Fig. 5A-5C several aspects of the repeater system with a common cable Fig. 6 shows a repeater system with a common cable at two different intermediate frequencies; Fig. 7 an application of the repeater system with multiple service antennas; Fig. 8A and 8B a sectorization of transmission channels; Fig. 9A a block diagram for a repeater with four service antennas; Fig. 9B the modular structure of the repeater system; Fig. 10 the modular structure of the repeater system; Fig. 11A-11E several aspects for bundling the radio signals; Fig. 12A-12E Repeater system in the frequency domain; Fig. 13 the control of the repeater system; Fig. 14 the use of the repeater system in a building; Fig. 15 the control of the repeater system.

[0024] Fig. 4A shows a first aspect of the invention with a first frequency converter unit 400 and a second frequency converter unit 450, which are connected via two cables 420 and 425. The cables 420 and 425 are connected to the units 400 and 450 by plugs and connectors and can also have other passive and active elements. The first frequency converter unit 400, which is referred to below as the donor unit 400, has a downlink donor antenna 40a for a downlink path DL and an uplink donor antenna 40b for an uplink path UL. The downlink path DL in the donor unit 400 includes a donor downlink bandpass filter 405, which is connected to the donor antenna 40a and filters the received radio signals. A low-noise donor downlink amplifier 410 is connected to the output of the downlink bandpass filter 405 and amplifies the received signals in the filtered frequency range.The output of the low-noise donor downlink amplifier 410 is connected to a donor downlink mixer 415. This donor mixer 415 is a frequency downconverter that converts the frequency of the received signals to a (low) intermediate frequency.

[0025] The uplink path UL in the donor unit 400 further comprises a donor uplink mixer 430, a donor uplink power amplifier 435, and a donor uplink bandpass filter 440. The uplink path UL receives the signals transmitted by the second frequency converter unit 450, which is further referred to as the service unit 450. The donor uplink mixer 430 is an upconverter and converts the frequency of the received signals from the intermediate frequency IF to the transmission frequency. The signals are then amplified in the donor uplink power amplifier 435 and filtered in the donor uplink bandpass filter 440. The output of the donor uplink bandpass filter 440 is connected to the second donor antenna 40b, and the filtered signals are transmitted at the transmission frequency.

[0026] The service unit 450 includes a service downlink mixer 455 in the downlink path DL, which is connected to the input of a service downlink power amplifier 460. The service downlink mixer 455 is an upconverter that converts the signals to be transmitted from the donor unit 400 from the intermediate frequency to the transmission frequency. The service downlink power amplifier 460 amplifies the signals. The output of the service downlink power amplifier 460 is connected to the input of a service downlink bandpass filter 465, which filters the signals. The output of the service downlink bandpass filter 465 is connected to the downlink service antenna 50a, and the downlink service antenna 50a radiates the signals at the transmission frequency.

[0027] The uplink path of service unit 450 is connected to the uplink service antenna 50b, which is connected to the input of a service uplink bandpass filter 470. This service upload bandpass filter 470 filters the received radio signals in a specific frequency range and forwards only these filtered radio signals to a low-noise service upload amplifier 475, where the radio signals are amplified. The amplified signals from the low-noise service uplink amplifier 475 are forwarded to a service uplink mixer 480, where they are converted to an intermediate frequency for transmission to the donor unit 400 via cable 425 (a coaxial line).

[0028] In the donor unit 400, the received signals on the uplink path are forwarded to a donor uplink mixer 430 and upconverted to the transmit frequency for transmission, as described above.

[0029] By converting the frequencies between the donor unit 400 and the service unit 450 to a lower intermediate frequency (IF), it is possible to use longer coaxial cables for the cables 420 and 425. This means that the donor unit 400 and the service unit 450 can be operated separately from each other.

[0030] Fig. 4B shows an aspect of the repeater system 10 in which identical elements are present in the donor unit 400 and the service unit 450. These identical elements are identified by the same reference numerals.

[0031] The Fig. 4B The aspect presented differs from the aspect of Fig. 4A by a single donor antenna 40 instead of the two donor antennas 40a and 40b and a single service antenna 50 instead of the two service antennas 50a and 50b. The single donor antenna 40 is connected to the donor unit 400 and the single service antenna 50 is connected to the service unit 450.

[0032] The donor unit 400 has a donor switch 402 connected to the single donor antenna 40 and to both the downlink path DL and the uplink path UL. The donor switch 402 is used to switch the donor antenna 40 between the downlink path DL and the uplink path UL, depending on whether signals are being received or transmitted via the donor antenna 40. Similarly, a service switch 490 is present in the service unit 450. This service switch 490 is also connected to the downlink path DL and the uplink path UL of the service unit 450 and to the single service antenna 50. The service switch 490 can switch the signals to and from the service antenna 50 between the two paths (downlink path DL and uplink path UL).

[0033] In a third aspect of the invention ( Fig. 4C ) the donor downlink bandpass filter 405 and the donor uplink bandpass filter 440 are replaced by a single donor bandpass filter 405 / 440 and the Fig. 4B known donor switch 402 is moved behind the common bandpass filter 405 / 440. Likewise, in the service unit 450, the service downlink bandpass filter 465 and the service uplink bandpass filter 470 are replaced by a common service bandpass filter 465 / 470 and the Fig. 4B known service switch 490 has been relocated between the common service bandpass filter 465 / 470 and the service downlink power amplifier 460 and the low-noise service uplink amplifier 475.

[0034] A fourth aspect of the repeater system 10 is Fig. 4D In this aspect of the invention, the two cables 420, 425 have been replaced by a common cable 427 (also a coaxial cable). As can be seen from Fig. 4D As can be seen, the donor unit 400 therefore requires a donor output switch 403, which switches the radio signals between the common cable 427 and the donor downlink mixer 415 and the donor uplink mixer 430. A service input switch 452 is also present in the service unit 450. This service input switch 452 is also connected to the service downlink mixer 455 in the downlink path DL and to the service uplink mixer 480 in the uplink path UL of the service unit 450 and switches the radio signals to the common cable 427.

[0035] A fifth aspect of the repeater system 10 is Fig. 4E As can be seen from the Fig. 4E As can be seen, the common cable 427 is present between the donor unit 400 and the service unit 450. It can also be seen that the donor switch 402 and the service switch 490 are in positions as in the Fig. 4C presented aspect are present.

[0036] Another aspect of the invention is in Fig. 4F In the aspect of Fig. 4F There is also a common cable 427 between the donor unit 400 and the service unit 450. This aspect otherwise corresponds to the first aspect of the invention ( Fig. 4A ) with the two donor antennas 40a and 40b and the two service antennas 50a and 50b. Of course, this aspect of the invention requires the donor output switch 403 and the service input switch 452 to switch the radio signals to the common cable 427 at the intermediate frequency IF.

[0037] Another aspect of the invention is in Fig. 5A This aspect of the invention largely corresponds to the earlier aspects of the invention, with this aspect differing in that the common cable 427 transmits signals at two different frequencies, IF1 and IF2. For example, the radio signals on the downlink path DL between the donor unit 400 and the service unit 450 are transmitted at a first intermediate frequency IF1 via the common cable 427, and the radio signals on the downlink path DL between the service unit 450 and the donor unit 400 are transmitted at a second frequency IF2. A donor duplexer 500 is present in the donor unit 400, which redirects the radio signals to the appropriate path. A service duplexer 510 is also present in the service unit 450, the function of which is to redirect the radio signals to the appropriate paths in the uplink (UL) and downlink (DL).

[0038] In Fig. 5B A similar aspect of the repeater system 10 is shown, wherein the two donor antennas 40a and 40b of the repeater system 10 are Fig. 5A is replaced by a single donor antenna 40. Accordingly, the first donor unit 400 also includes a donor switch 402. The two service antennas 50a and 50b of Fig. 5A are also connected by a common service antenna 50 in the aspect of Fig. 5B replaced and a service switch 490 is also present in the service unit 450.

[0039] In Fig. 5C the donor switch 402 is displaced in the donor unit 400, as can be seen from the aspect of the Figuren 4C and 4E is known. The donor switch 490 is also advanced in the service unit 450.

[0040] Fig. 6 shows a further aspect of the invention with a common cable 427, which transmits radio signals at two different frequencies IF1 and IF2. As can be seen from the figures, the donor unit 400 contains two downlink paths DL and two uplink paths UL, each with a mixer 600a, 600b, 610a, 610b. The mixers 600a, 600b, 610a, 610b can convert the frequency of the radio signals either to the intermediate frequency IF1 or to the intermediate frequency IF2, and these are forwarded to the service unit 450, in which the radio signals are converted back to the transmission frequency. The service unit 450 also contains two downlink paths DL and two uplink paths UL, each with a mixer 650a, 650b, 660a, 660b. The other elements are shown in the Figuren 4A-4F and 5A-5D.

[0041] An application of the repeater system 10 of this document is in Fig. 7 In this Figur 7 A plurality of service units 450-1, 450-2, 450-3, and 450-4 are shown, each connected to a service antenna 50-1, 50-2, 50-3, and 50-4. The plurality of service units 450-1, 450-2, 450-3, and 450-4 are connected via coaxial lines 720-1, 720-2, 720-3, and 720-4 to a splitter 700, which divides and forwards the radio signals from the donor unit 400 to the plurality of service units 450-1, 450-2, 450-3, and 450-4. The splitter 700 is connected to the donor unit 400 via a cable 710. This Fig. 7 The aspect of the invention shown has the advantage that different radiation characteristics for the radio signals can be used in the majority of the service units 450-1, 450-2, 450-3 and 450-4.

[0042] Fig. 8A shows an example of these radiation characteristics, where the donor antenna 40 receives radio signals in four different frequency ranges f1, f2, f3 and f4 from the base station (not shown) and Fig. 7 The known repeater system 10 can radiate the received radio signals in four different directions in all received frequency ranges f1, f2, f3, and f4 in a kind of "cube shape" via the four different service antennas 50a-d. Each service antenna 50a-d radiates all four frequency ranges f1, f2, f3, and f4.

[0043] In contrast, Fig. 8B another variation of the radiation characteristics. In this Fig. 8B Each service antenna 50a-d radiates radio signals in only one frequency range f1, f2, f3, f4. In other words, the radio signals received via the donor antenna 40 in the four frequency ranges f1, f2, f3, and f4 are each radiated in one direction at different frequency ranges f1, f2, f3, or f4 via the respective service antennas 50a-d. With the help of this repeater system, specific sectors (reception areas) can be supplied with radio signals of a specific frequency; the radio signals in other sectors have a different frequency.

[0044] Fig. 9A shows a block diagram for the implementation of the repeater system 10 from Fig. 7 with a donor unit 400, which is connected via cable 427a-c to four different service units 450a-c. As can be seen from the Fig. 9A As can be seen, the donor unit 400 is connected to a signal selector 900. The signal selector 900 comprises four bandpass filters, each of which selects only the radio signals of one of the four intermediate frequencies IF1, IF2, IF3, and IF4, and transmits these selected radio signals to a corresponding service unit 450-1, 450-2, 450-3, and 450-4.

[0045] Fig. 9B shows the modular design of the repeater system 10. As can be seen from the figure, the donor antenna with bandpass filter 940 is separated from the electronic module 960 in the donor unit 400. The service units 450 are also divided into modules. The electronic modules 960a, 960b, 960c, and 960d are similarly constructed and are separated from the service antennas 50 with bandpass filters 950a, 950b, 950c, and 950d. This modular design is also shown in Fig. 10 presented in a simple form.

[0046] Fig. 11A-11E show the use of the repeater system 10 for bundling the radio signals on the service side. The radio signals are received via a line 1110 from the donor unit 400 and distributed or reshaped in a distribution network 1120 or beamforming network (also referred to as a beamforming network or lobe formation network) and forwarded to the service antennas 50. Through this distribution, different radiation patterns of the service antennas 50 can be created. For example, Fig. 11A a simple radiation pattern with a main lobe 1130 and two secondary lobes 1135.

[0047] The use of the dielectric lens 1140 is in Fig. 11B This results in a very strong main lobe 1150 with side lobes 1155. In Fig. 11C A beamforming network is shown with a dielectric lens 1140, which also has a radiation pattern with a strong main lobe 1160 and side lobes 1165, which is pivoted in this aspect of the invention. The pivoting of the main lobe 1170 with side lobes 1175 of the radio signals by the beamforming network 1125 is known and is described in Fig. 11D shown. In a further aspect of the invention, a Rotmann lens 1180 is used as a distribution network. This allows the radio signals to be bundled into a plurality of radiation directions (beams) 1190.

[0048] The invention can also be used for repeater systems 10 with frequency division duplex (FDD), as can be seen from Fig. 12A-12E can be seen. The structure of the respective figures is similar to that for repeater systems 10 with time division duplex (TDD). Fig. 12A shows the transmission of radio signals between the donor unit 400 and the service unit 450. Fig. 12B shows a joint transmission of the radio signals on the common cable 427 with two different intermediate frequencies in IF1 and IF2 with a duplexer 444 in the donor unit 400 and a duplexer 492 in the service unit 450. Fig. 12C shows the use of a single donor antenna 40 and a single service antenna 50 by combining the uplink and downlink signals at the donor antenna 40 with a duplexer 442 and combining the uplink and downlink signals at the service antenna 50 with a duplexer 494. Fig. 12D shows the repeater system Fig. 12C with two different transmission paths and Fig. 12E How the common cable 427 can be used with the donor unit 400 and the service unit 450 by using different intermediate frequencies IF1, IF2, IF3, and IF4. Additional donor units 400 and service units 450 can be added.

[0049] In Fig. 13 It is shown that the control of the repeater system 10 can be controlled externally via an IT network 1310 via a so-called IoT modem 1300.

[0050] An application of the repeater system 10 of this document is, for example, in Fig. 14 and is located in a building 1405 that is already wired with coaxial lines 1420. These existing coaxial lines can be reused using the repeater system 10 of this document. In this case, the intermediate frequency IF is selected such that the signals on the existing coaxial line 1420 are not interfered with by the radio signal transmitted between the donor unit 1400 and the service unit 1410. This allows mobile stations (user equipment) 1430 in a building to be supplied with radio signals. Fig. 15 shows another aspect of the repeater system 10 of this document. At least one transmission path (e.g., 1530) via lines 1540 between the donor unit 1500 and the service unit 1510 can be supplied with additional control signals and, for example, transmit data from or to the IT network 1560 via an additional transmission path 1550. Reference symbol

[0051] 10Repeater 20Base station 30Mobile station 40Donor antenna 40aDownlink donor antenna 40bUplink donor antenna 45Coaxial line 50Service antenna 50aDownlink service antenna 50bUplink service antenna 55Coaxial line 100First duplexer 105First switch 110Downlink amplifier 120Downlink bandpass filter 130Downlink power amplifier 150Second duplexer 155Second switch 160Uplink amplifier 170Uplink bandpass filter 180Uplink power amplifier 400First Frequency Converter Unit / Donor Unit 402Donor Switch 403Donor Output Switch 405Donor Downlink Bandpass Filter 410Donor Downlink Amplifier 415Donor Downlink Mixer 420Cable 425Cable 427Common Cable 430Donor Uplink Mixer 435Donor Uplink Power Amplifier 440Donor Uplink Bandpass Filter 442Duplexer 444Duplexer 450Service Unit 452Service Input Switch 455Service Downlink Mixer 460Service Downlink Power Amplifier 465Service Downlink Bandpass Filter 470Service Uplink Bandpass Filter 475Service Uplink Amplifier 480Service Uplink Mixer 490Service Switch 492 Duplexer 494 Duplexer 500Donor duplexer 510Service duplexer 600a,bMixing device 610a,bMixing device 650a,bMixing device 660a,bMixing device 700Splitter 710Cable 900 Signal selector 940 Donor antenna with bandpass filter 950 Service antenna with bandpass filter 960 Electronics module 1110Line 1120Distribution network 1125Beamforming network 1130Main lobe 1135Side lobe 1140Dielectric lens 1150Main lobe 1155Side lobe 1160Main lobe 1165Side lobe 1170Main lobe 1180Rotmann lens 1190Beam direction 1300IoT Model 1310ITG Network 1400Donor Unit 1405Building 1410Service Unit 1420Coaxial Cables 1430User Equipment 1500Donor Unit 1510Service Unit 1530Transmission Path 1540Lines 1550Additional Transmission Path 1560IT Network

Claims

1. A repeater system (10) for forwarding radio signals, comprising: a donor unit (400) for converting the frequencies of the radio signals from the transmission frequency to an intermediate frequency (ZF); at least one service unit (450) for converting the converted radio signals from the intermediate frequency (ZF) to the transmission frequency; and at least one cable (420, 425, 427), connecting the donor unit (400) to the service unit (450) for transmitting the converted radio signals over a distance between the donor unit (400) and the service unit (450) at the intermediate frequency (ZF), wherein at least the donor unit (400) comprises an uplink donor antenna (40b) and an isolated, separate downlink donor antenna (40a) and the service unit (450) comprises an uplink service antenna (50b) and also a separate downlink service antenna (50a), and wherein the repeater system (10) further comprises a donor downlink amplifier (410) with adjustable gain, wherein the total gain is adjusted by adjusting the donor downlink amplifier (410) such that the sum of the total gain between the downlink donor antenna (40a) and the uplink service antenna (50b) is less than the decoupling between the uplink donor antenna (40b) and the downlink service antenna (50a).

2. The repeater system (10) according to Claim 1, wherein in operation the radio signals are transmitted in the TDD mode.

3. The repeater system (10) according to Claim 1 or 2, wherein in operation the radio signals are transmitted in the centimetre and millimetre range.

4. The repeater system (10) according to any one of the preceding claims, wherein the donor unit (400) comprises a separate donor uplink path and a separate donor downlink path, and the service unit (450) comprises a service uplink path and a separate service downlink path.

5. The repeater system (10) according to any one of the preceding claims, comprising additional service units (450) and a plurality of cables (420, 425, 427), wherein the plurality of cables connect the donor unit (400) to each of the additional service units (450) and transmit the converted radio signals over a distance between the donor unit (400) and the connected additional service units (450).

6. The repeater system (10) according to Claim 5, wherein the additional service units (450) are adapted such that the service units (450) radiate and receive radio signals in different directions.

7. The repeater system (10) according to Claim 6, wherein the service units (450) are located at one location and radiate and receive in different, possibly overlapping, sectors.

8. The repeater system (10) according to any one of Claims 1, 3, 5, 6 or 7, wherein in operation, the service units (450) radiate and receive radio signals at different transmission frequencies.

9. The repeater system (10) according to any one of Claims 1 to 6, wherein the donor unit (400) comprises a donor uplink bandpass filter (440) connected to the uplink donor antenna (40b), and a donor downlink bandpass filter (405) connected to the downlink donor antenna (40a) for transmitting the radio signals.

10. The repeater system (10) according to Claim 9, wherein the donor unit (400) comprises the donor uplink bandpass filter (440) and the donor downlink bandpass filter (405) for the same operating frequency in a TDD system.

11. The repeater system (10) according to any one of Claims 2 to 7, wherein the donor downlink path comprises the donor downlink amplifier (410) and a donor downlink mixing device (415), wherein the donor downlink mixing device (415) is connected to the cable (420, 425, 427).

12. The repeater system (10) according to any one of the preceding claims, wherein the decoupling between the uplink donor antenna (40b) and the downlink donor antenna (40a) is at least 40 dB and, optionally, wherein the decoupling between the uplink donor antenna (40b) and the downlink donor antenna (40a) for a TDD system is at least 60 dB.

13. The repeater system (10) according to any one of the preceding claims, wherein at a time when no useful signal is passing through the amplifier, the amplification of the downlink path in the donor unit (400) and / or the service unit (450) in a TDD system is switched off or reduced in gain.

14. The repeater system (10) according to any one of the preceding claims, wherein the donor unit (400) comprises a donor downlink amplifier (410) and the at least one service unit (450) comprises a service uplink amplifier (475), wherein at a time when no useful signal is passing through said amplifier, the amplifier is switched off or reduced in gain.