WO2013150171A1

WO2013150171A1 - Radio frequency circuitry for multi-modem radio device

Info

Publication number: WO2013150171A1
Application number: PCT/FI2012/050338
Authority: WO
Inventors: Timo Hakala
Original assignee: Nokia Corporation
Priority date: 2012-04-03
Filing date: 2012-04-03
Publication date: 2013-10-10

Abstract

This document discloses coupling radio modems (22, 24) to antennas (40, 42) in a radio apparatus. In an embodiment, a first antenna (40) of the radio apparatus is coupled to a first signal line connecting the first antenna (40) to a first radio modem (22) of the radio apparatus; a second antenna (42) of the radio apparatus is coupled to a first signal interface (32) of a second radio modem (24) via a second signal line; and, simultaneously with coupling the first antenna (40) to the first signal line, the first antenna (40) is coupled to a third signal line connecting the first antenna (40) to a second signal interface (30) of the second radio modem (24).

Description

RADIO FREQUENCY CIRCUITRY FOR MULTI-MODEM RADIO DEVICE Field

The invention relates to the field of radio communications and, particularly, to a radio device provided with multiple radio modems. Background

Some modern radio devices such as mobile telephones provide a dual- modem capability. For example, a mobile telephone with dual-SIM (Subscriber Identity Module) capability may comprise two radio modems, one for each SIM.

Brief description

According to an aspect of the present invention, there is provided an apparatus comprising: a first radio modem; a second radio modem comprising a first signal interface and a second signal interface; a first antenna coupled to the first radio modem via a first signal line; a second antenna coupled to the first signal interface of the second radio modem via a second signal line; and a radio frequency coupling element arranged to couple the first antenna simultaneously to the first signal line and to a third signal line leading from the radio frequency coupling element to the second signal interface of the second radio modem.

According to another aspect of the present invention, there is provided a method comprising: coupling a first antenna of a radio apparatus to a first signal line connecting the first antenna to a first radio modem of the radio apparatus; coupling a second antenna of the radio apparatus to a first signal interface of a second radio modem via a second signal line; and coupling, simultaneously with coupling the first antenna to the first signal line, the first antenna to a third signal line connecting the first antenna to a second signal interface of the second radio modem.

According to another aspect of the present invention, there is provided an apparatus comprising means for coupling a first antenna of the apparatus to a first signal line connecting the first antenna to a first radio modem of the radio apparatus; means for coupling a second antenna of the apparatus to a first signal interface of a second radio modem via a second signal line; and means for coupling, simultaneously with coupling the first antenna to the first signal line, the first antenna to a third signal line connecting the first antenna to a second signal interface of the second radio modem.

According to another aspect of the present invention, there is provided a computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into the computer, execute a computer process comprising: triggering a transmission mode of a first radio modem utilizing time division duplexing and, as a consequence, causing disconnection of a second radio modem from a radio frequency coupling element and from a first antenna shared by the first radio modem and one of a plurality of signal interfaces of a second radio modem; triggering a reception mode of the first radio modem and, as a consequence, causing simultaneous connection of the first radio modem and the second radio modem to the radio frequency coupling element and the first antenna.

Embodiments of the invention are defined in the dependent claims.

List of drawings

Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which

Figure 1 illustrates communication between a radio device and a cellular communication system;

Figure 2 illustrates radio circuitries of an apparatus according to an embodiment of the invention;

Figure 3 illustrates another, detailed embodiment of the apparatus;

Figure 4 illustrates a flow diagram of operation of a controller circuitry according to an embodiment of the invention;

Figure 5 is a flow diagram illustrating a method of the operation of a radio apparatus according to an embodiment of the invention; and

Figure 6 illustrates yet another detailed embodiment of the apparatus.

Description of embodiments

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

Figure 1 illustrates a communication scenario in which a radio device 104 communicates with two cellular communication networks represented by base stations 100, 102. One of the cellular communication networks may employ one radio access technology (RAT), while the other cellular communication network may employ a different RAT. The radio device 104 may be a terminal device of both cellular communication networks and comprise separate radio modems for the two or, in some embodiments, more cellular communication networks. The radio device 104 may be a multi-radio device supporting simultaneous operation in multiple cellular communication networks, and it may comprise a plurality of subscriber identity modules (SIMs) for simultaneous operation and simultaneous connections in the multiple cellular communication networks. The radio device 104 may be defined as a dual SIM dual active (DSDA) radio device, as it has dual SIMs that are operable simultaneously by providing a connected state simultaneously in two cellular communication networks. The concept may be expanded to radio devices with more than two SIMs, thus defining the radio device 104 as a multi SIM multi active device. The cellular communication networks may operate according to at least some of the following specifications: Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunication System (UMTS) based on Wideband Code Division Multiple Access (W-CDMA), High-Speed Uplink/Downlink Packet Access (HSUPA/HSDPA), UMTS Long-Term Evolution (LTE), UMTS LTE-Advanced, and IEEE 802.16. In an embodiment, the radio device 104 comprises a radio modem supporting a second generation cellular technology, e.g. GSM with EDGE, and a radio modem supporting a third and/or fourth generation cellular technology, e.g. UMTS W-CDMA and/or LTE-Advanced.

The radio device 104 operating as the terminal device may be a mobile communication device or a portable radio communication device, a cellular telephone with high-speed packet data transfer capability, a laptop computer, a palm computer, a tablet computer, or even a vehicle to which the terminal device has been integrated.

Let us now describe an apparatus according to an embodiment of the invention in greater detail. The apparatus may be comprised in the radio device 104. Referring to Figure 2, the apparatus comprises a first radio modem 22 and a second radio modem 24. The first radio modem 22 may employ a different RAT than a RAT employed by the second radio modem 24. The second radio modem may support multi-antenna reception, e.g. multiple-input-multiple-output (MIMO) reception or spatial diversity reception. Therefore, the second radio modem 24 comprises a first signal interface 32 for receiving a first signal and a second signal interface 30 for communication of a second signal. The apparatus further comprises a first antenna 40 coupled to the first radio modem 22 via a first signal line, and a second antenna 42 coupled to the first signal interface 32 of the second radio modem 24 via a second signal line.

In order to provide the second radio modem with the multi-antenna reception capability, the apparatus comprises a radio frequency (RF) coupling element 26 arranged on the first signal line to couple the first antenna 40 simultaneously to the first signal line and to a third signal line leading from the radio frequency coupling element 26 to the second signal interface 30 of the second radio modem 24.

The RF coupling element 26 thus implements antenna sharing between the first radio modem 22 and the second signal interface 30 of the second radio modem 24, thereby enabling simultaneous operation of the first radio modem 22 and the second signal interface 30 of the second radio modem 24. Technical advantages may include reduction in the size of the radio device 104, improved data rates and improved user experience. The reduction in size may be achieved by avoiding a need for a third antenna. It should also be noted that this embodiment may also enable the antenna sharing between two radio modems in devices where it is not possible to implement three antennas. With respect to the improved data rates and improved user experience, let us assume a scenario where a user is having a telephone conversation, wherein a voice call is established through the first radio modem 22 and the first antenna 40. As the RF coupling element 26 provides simultaneous antenna sharing to both radio modems 22, 24, the user may carry out data transfer on the background of the voice call through the second radio modem 24, and the second radio modem 24 may employ the spatial diversity communication through the first antenna 40 during the voice call. Thus, the second radio modem 24 may provide high data rates even during the voice call. The performance of the multi-antenna reception of the second radio modem 24 may be improved when the first radio modem 22 is in an idle mode.

As mentioned above, the second radio modem 24 may support the

MIMO communication and/or the diversity communication as multi-antenna transmission schemes, wherein the multi-antenna signals are communicated through the first signal interface 32 and the second signal interface 30. The difference between multi-antenna communication techniques may reside in signal processing carried out in the second radio modem 24 and/or in other signal processing circuitries of the apparatus, so the same RF components and signal interfaces may be operable in connection with different multi-antenna transmission techniques. Below, the description focuses to the diversity reception as an embodiment of the multi-antenna communication and, as a consequence, the first signal interface 32 of the second radio modem 24 is called a main signal interface, the second signal interface 30 is called a diversity signal interface, and the third signal line is called a diversity signal line. It should, however, be understood that the same description applies equally to other multi-antenna reception techniques operable in the second radio modem 24.

A coupling factor of the radio frequency coupling element 26 may attenuate the signals coupled by the coupling element 26 to some degree. Operation of the modern cellular communication systems is, however, rarely limited by thermal noise. Therefore, advantages gained by providing radio modems 22, 24 with the simultaneous connection to the first antenna 40 overcome the slight signal attenuation caused by the coupling element 26.

In an embodiment, the RF coupling element 26 is a RF coupler. The RF coupler may be realized by providing two transmission lines in a printed wiring board (PWB) comprising the RF coupler and other RF components such that a first transmission line conveys an antenna interface connected to the first antenna 40 to an interface connected to one of the first signal line and the diversity signal line. A second transmission line connected to the other of the first signal line and the diversity signal line is brought so close to the first transmission line that the RF signal conveyed through the first transmission line is coupled also to the second transmission line. In another, a dedicated RF coupler component may be used.

In another embodiment, the RF coupling element 26 is a power divider or a power splitter configured to divide or split an RF signal from the first antenna 40 to both the first radio modem 22 and the diversity signal interface 30 of the second radio modem.

The RF coupling element 26 may be a directional coupler configured to couple a signal from the first antenna 40 to both the first signal line and the diversity signal line, a signal from the first signal line to the first antenna 40, and a signal from the diversity signal line to the first antenna 40. The RF coupling element 26 may in some embodiments be configured to isolate the diversity signal line from the first signal line such that a signal from the first signal line is not forwarded to the diversity signal line or at least the signal is strongly attenuated.

The RF coupling element 26 should be understood to encompass at least the above-described RF coupling elements. The RF coupling element may be understood to encompass any RF element that is configured to realize the sharing of the first antenna 40 simultaneously between said at least two radio modems.

Figure 3 illustrates an embodiment of the apparatus of Figure 2 in greater detail. In this embodiment, the RF coupling element 26 is illustrated as the RF coupler. The first radio modem 22 comprises a transmitter circuitry 52 configured to carry out transmission signal processing for signals transmitted from the radio device 104 through the first antenna 40, and a receiver circuitry 50 configured to carry out transmission signal processing for signals received in the radio device 104 through the first antenna. The received RF signals may be applied to a bandpass filter 72 provided between the coupler 26 and the receiver circuitry 50 and tuned to a reception band of the first radio modem 22. An RF signal output from the transmitter circuitry 52 may be applied to a power amplifier circuitry 80 configured to power-amplify the RF signal before outputting the RF signal to the first antenna through the coupler 26.

Similarly, the second radio modem 24 may comprise a transmitter circuitry 64 and a receiver circuitry 62 connected to the second antenna 42 via bandpass filters 76, 78 tuned respectively to the reception and transmission frequencies of the second radio modem 24. A duplex filter may realize both bandpass filters 76, 78. A power amplifier circuitry 82 may be configured to power- amplify RF transmission signals output from the transmitter circuitry 64. A bandpass filter 74 may be arranged between the diversity signal interface 30 and the RF coupler 26 and tuned to the reception band of the second radio modem 24.

The first radio modem 22 and the second radio modem 24 may comprise a RF circuitry configured to carry out RF signal processing of the transmitted and received signals, and a baseband circuitry configured to carry out baseband signal processing of the transmitted and received signals. The RF circuitries and the baseband circuitries may be realized by separate integrated circuits, for example. The first radio modem 22 may comprise or be connected to a first subscriber identity module interface 300 configured to connect a first subscriber identity module (SIM) to the first radio modem 22. Similarly, the second radio modem 24 may comprise or be connected to a second subscriber identity module interface 302 configured to connect a second SIM to the second radio modem 24.

The first radio modem 22 may operate according to time-division principles, e.g. time division multiple access (TDMA) or time-division duplexing (TDD). Accordingly, only one of the transmitter circuitry 52 and the receiver circuitry 50 may be operational at a time, and the first radio modem 22 may comprise a controller circuitry 54 configured to switch the operational mode of the first radio modem 22 between a transmission mode and a reception mode. In the transmission mode, the controller circuitry 54 may be configured to enable the operation of the transmitter circuitry 52 and to disable the operation of the receiver circuitry 50, while in the reception mode the controller circuitry 54 may be configured to disable the operation of the transmitter circuitry 52 and to enable the operation of the receiver circuitry 50. However, if the transmission band of the first radio modem is sufficiently separated from the reception band of the diversity signal interface 30, the diversity signal interface 30 may be connected to the first antenna 40 also in the transmission mode of the first radio modem. The sufficient separation may be defined in terms of sufficient attenuation of the transmission signal of the first radio modem on the reception band of the diversity signal in the second radio modem. In another embodiment, the first radio modem 22 operates in a frequency division duplexing (FDD). Then, the diversity signal interface 30 may be connected to the first antenna 40 all the time, when the transmission circuitry of the first radio modem 22 is off, or when the first radio modem is off or in an idle state. The second radio modem may operate in a TDD mode or in the FDD mode. In general, in some embodiments the diversity signal interface 30 is connected to the first antenna 40 during the transmission mode of the first radio modem 22, while in other embodiments the diversity signal interface 30 is disconnected from the first antenna 40 during the transmission mode of the first radio modem 22.

In an embodiment where the second radio modem 24 utilizes spatial diversity or, in general, multi-antenna reception through the first antenna 40, the transmitter circuitry 52 of the first radio modem 22 may be coupled in its transmission mode with the third signal line leading to the second radio modem 24 through the coupler 26 and the diversity signal interface 30. Even if the coupler provides isolation between its ports connected to the first radio modem 22 and the diversity signal interface 30 of the second radio modem 24, RF power may still leak from the transmitter circuitry 52 to the diversity signal interface 30, and this RF power may even break reception circuitries of the second radio modem 24. Some embodiments of the invention address such issues, as described next.

In an embodiment, the controller circuitry 54 is configured to indicate to the second radio modem 24 about its communication mode, and the second radio modem 24 is configured to shut down its diversity reception circuitries or disconnect them from the radio frequency coupling element 26 upon receiving from the controller circuitry 54 a signal indicating that the first radio modem 22 is in the transmission mode. On the other hand, the second radio modem 24 may be configured to activate its diversity reception circuitries or connect them to the radio frequency coupling element 26 upon receiving from the controller circuitry 54 a signal indicating that the first radio modem 22 is in the reception mode or in an idle mode. As a consequence, the controller circuitry 54 may be configured to blank the diversity reception of the second radio modem 24 when the first radio modem 22 is in the transmission mode. The control signal output from the controller circuitry 54 to the second radio modem is indicated in Figure 3 by an arrow from the controller circuitry 54 to the diversity signal interface 30.

In another embodiment, the apparatus comprises a first switch 84 arranged on the diversity signal line. The first switch is arranged to disconnect the diversity signal interface 30 of the second modem 24 from the first antenna 40. The controller circuitry 54 may be configured to operate the first switch 84 to disconnect the diversity signal interface 30 from the first antenna 40 when the transmitter circuitry 52 of the first radio modem 22 is carrying out a transmission. As a consequence, the controller circuitry 54 may be configured synchronize the operation of the first switch 84 with the switching of the first radio modem 22 between the transmission mode and the reception mode. The first switch 84 may be comprised in a set of switches that are used to select an appropriate bandpass filter, e.g. the bandpass filter 74, tuned to the reception frequency of the second radio modem 24. As a consequence, the first switch 84 may have a dual functionality, e.g. selecting the bandpass filter and disconnecting the second radio modem 24 from the RF coupling element 26.

The apparatus may further comprise a second switch 86 arranged on the first signal line between the radio frequency coupling element 26 and the first radio modem 22. The second switch 86 may be arranged to switch either the transmitter circuitry or the receiver circuitry to the radio frequency coupling element 26 under the control of the controller circuitry 54. In the transmission mode, the controller circuitry 54 may operate the second switch 86 to connect the transmitter circuitry 52 to the RF coupling element 26. In the reception mode, the controller circuitry 54 may operate the second switch 86 to connect the receiver circuitry 50 to the RF coupling element 26. The controller circuitry 54 may be configured to synchronize the operation of the first switch 84 with the operation of the second switch 86 such that when the controller circuitry 54 operates the second switch 86 to connect the transmitter circuitry 52 to the radio frequency coupling element 26, the controller circuitry 54 operates also the first switch 84 to disconnect the diversity interface 30 of the second radio modem 24 from the radio frequency coupling element 26. On the other hand, when the controller circuitry 54 operates the second switch 86 to connect the receiver circuitry 50 to the radio frequency coupling element 26, the controller circuitry 54 operates the first switch 84 to connect the diversity interface 30 of the second radio modem 24 to the radio frequency coupling element 26.

The two embodiments for preventing the RF power from the transmitter circuitry 52 to the diversity signal interface 30 may also be combined, e.g. the controller circuitry 54 may operate the first and second switch 84, 86 in the above- described manner and output to the second radio modem 24 an indication of the communication mode of the first radio modem 22. Accordingly, the second radio modem may shut down the diversity reception circuitries or disregard any data or signals received during the transmission mode of the first radio modem 22, and the first switch 84 also disconnects the diversity signal interface 30 physically from the radio frequency coupling element 26 and from the transmitter circuitry 52.

The signal output from the controller circuitry 54 to the second radio modem 24 may be the same control signal that switches the communication mode of the first radio modem. As a consequence, the controller circuitry 54 may use the same control signal to change the communication mode of the first radio modem 22 and to activate/disable the diversity reception in the second radio modem 24.

Figure 6 illustrates yet another embodiment of the invention where the radio frequency coupling element 26 is arranged on a receiver (RX) line of the first signal line connecting the first antenna 40 to the receiver circuitry 50 of the first radio modem 22. As a consequence, the number of switches may be reduced by removing the first switch 84. The function of the second switch 86 may be similar to the embodiment of Figure 3, and it may be configured to connect the transmitter circuitry 52 or the receiver circuitry 50 to the first antenna 40 according to the operational mode of the first radio modem 22. The controller circuitry 54 may control the second switch 86 in the above-described manner. As the radio frequency coupling element 26 is provided on the receiver line and inherently disconnected from the first antenna 40 during the transmission mode of the first radio modem 22, the controller circuitry 54 does not need to separately disconnect or shut down circuitries of the second radio modem 24 during the transmission mode of the first radio modem 22. Thus, the complexity may be reduced. In an embodiment, a low-noise amplifier 90 is provided on the receiver line between the radio frequency coupling element 26 and the first antenna 40 to compensate for possible attenuation caused by the coupling element 26, but in some embodiments the amplifier 90 may be omitted. It should be appreciated that while the controller circuitry 54 is described as a part of the first radio modem, it may be provided as a separate logical and/or physical element, e.g. it may be provided as a separate circuitry.

As used in this application, the term 'circuitry' refers to all of the following: (a) hardware-only circuit implementations such as implementations in only analog and/or digital circuitry; (b) combinations of circuits and software and/or firmware, such as: (i) a combination of processor(s) or processor cores; or (ii) portions of processor(s)/software including digital signal processor(s), software, and at least one memory that work together to cause an apparatus to perform specific functions; and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of 'circuitry' applies to all uses of this term in this application. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor, e.g. one core of a multi-core processor, and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular element, a baseband integrated circuit, an application-specific integrated circuit (ASIC), and/or a field-programmable grid array (FPGA) circuit for the apparatus according to an embodiment of the invention. For example, the operation of the controller circuitry 54 may be at least partly defined by a computer program product which may be embodied on a distributable or a non-distributable computer-readable medium. The computer program product may comprise computer program code in a source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include transitory and/or non-transitory computer media, e.g. a record medium, computer memory, read-only memory, electrical carrier signal, and software distribution package.

With reference to a flow diagram of Figure 4, let us now describe an embodiment of a computer process executed by the controller circuitry 54 upon reading the above-described computer program code. The controller circuitry 54 may comprise at least one processor and at least one memory including the computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to operate in an apparatus where two radio modems share the same antenna, e.g. the above- described apparatus, and to carry out the steps of Figure 4. Referring to Figure 4, the transmission mode of the first radio modem 22 is triggered in block 400. As a result, the controller circuitry 54 may activate the transmitter circuitry 52 and cause disconnection of the second radio modem 24 from the radio frequency coupling element 26 and from the first antenna 40 (block 402). As described above, the controller circuitry 54 may output a signal that physically disconnects the second radio modem 24 from the radio frequency coupling element 26 and from the first antenna 40. The signal may operate at least the first switch 84 and/or inform the second radio modem 24 to carry out the disconnection, e.g. by switching off at least some parts of a multi-antenna signal processing circuitry of the second radio modem 24. In block 404, the reception mode of the first radio modem 22 is triggered. As a result, the controller circuitry 54 activates the receiver circuitry 50 and causes connection of the second radio modem 24 to the radio frequency coupling element 26 and to the first antenna 40 (block 406). As described above, the controller circuitry 54 may output a signal that physically connects the second radio modem 24 to the radio frequency coupling element 26 and to the first antenna 40. The signal may operate at least the first switch 84 and/or inform the second radio modem 24 to carry out the connection, e.g. by switching on the multi- antenna signal processing circuitry of the second radio modem 24. Then, the process may return to block 400 when the transmission mode of the first radio modem 22 is once again triggered.

In practice, the second radio modem 24 may need to be disconnected from the coupling element 26 only when the transmitter circuitry 52 is actually transmitting a radio signal, e.g. the second radio modem 24 may be connected to the coupling element 26 not only during the reception mode of the first radio modem in the above-described manner but also during transition period or a guard time between the transmission mode and the reception mode of the first radio modem 22. Therefore, in an embodiment the controller circuitry 54 is configured to connect the second radio modem 24 to the radio frequency coupling element 26 after the transmitter circuitry 52 has been deactivated and before activating the receiver circuitry 50. In an embodiment, the controller circuitry 54 simultaneously deactivates the transmitter circuitry 52 and connects the second radio modem 24 to the coupling element 26. As a consequence, the second radio modem is connected to the coupling element 26 during the guard period between the transmission mode and the reception mode of the first radio modem 22.

From the point of view of the operation of the apparatus according to an embodiment, the apparatus may be configured to carry out a method illustrated in Figure 5. An embodiment provides the apparatus with means for causing the apparatus to carry out the method. The method may be carried out in the above- mentioned apparatus which may be a radio apparatus. Referring to Figure 5, the method comprises coupling the first antenna 40 of the radio apparatus to the first signal line connecting the first antenna 40 to the first radio modem 22 of the radio apparatus (block 500). Simultaneously, the first antenna 40 is coupled to the third signal line connecting the first antenna 40 to the second signal interface 30 of the second radio modem 24.

In block 502, the second antenna 42 of the radio apparatus is coupled to the first signal interface 32 of the second radio modem 24 via the second signal line.

In an embodiment, block 500 comprises operating the first switch 84 arranged on the third signal line to disconnect the second signal interface 30 of the second modem 24 from the first antenna 40 when the first radio modem 22 is carrying out a transmission.

In an embodiment, the method further comprises switching the first radio modem 22 between the transmission mode and the reception mode. In an embodiment, block 500 comprises synchronizing the operation of the first switch 84 with the switching of the first radio modem 22 between the transmission mode and the reception mode. In an embodiment, block 500 further comprises operating the second switch 86 arranged on the first signal line to switch either the transmitter circuitry 52 or the receiver circuitry 50 of the first radio modem 22 to the first antenna 40. In an embodiment, block 500 further comprises synchronizing the operation of the first switch 84 with the operation of the second switch 86 such that when the second switch 86 is operated to connect the transmitter circuitry 52 to the first antenna 40, the first switch 84 is operated to disconnect the second signal interface 30 of the second radio modem 24 from the first antenna 40.

In an embodiment, block 500 comprises operating a multi-antenna signal processing circuitry of the second radio modem 24 to suspend multi- antenna signal processing when the first radio modem 22 is carrying out a transmission.

The present invention is applicable to the radio device 104 of any one of the cellular or mobile communication systems defined above but also to other suitable radio devices. The radio communication protocols and the specifications of such radio devices and cellular communication systems develop rapidly. Such development may require extra changes to the described embodiments. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1 . An apparatus comprising:

a first radio modem;

a second radio modem comprising a first signal interface and a second signal interface;

a first antenna coupled to the first radio modem via a first signal line; a second antenna coupled to the first signal interface of the second radio modem via a second signal line;

a radio frequency coupling element arranged to couple the first antenna simultaneously to the first signal line and to a third signal line leading from the radio frequency coupling element to the second signal interface of the second radio modem.

2. The apparatus of claim 1 , further comprising:

a first switch arranged on the third signal line, wherein the first switch is arranged to disconnect the second signal interface of the second modem from the first antenna; and

a controller circuitry configured to operate the first switch to disconnect the second signal interface of the second modem from the first antenna when the first radio modem is carrying out a transmission.

3. The apparatus of claim 2, wherein the controller circuitry is comprised in the first radio modem and further configured to switch the first radio modem between a transmission mode and a reception mode.

4. The apparatus of claim 3, wherein the controller circuitry is configured to synchronize the operation of the first switch with the switching of the first radio modem between the transmission mode and the reception mode.

5. The apparatus of any preceding claim 2 to 4, further comprising a second switch on the first signal line between the radio frequency coupling element and the first radio modem, the first radio modem comprising a transmitter circuitry and a receiver circuitry, wherein the second switch is arranged to switch either the transmitter circuitry or the receiver circuitry to the radio frequency coupling element under the control of the controller circuitry.

6. The apparatus of claim 5, wherein the controller circuitry is configured to synchronize the operation of the first switch with the operation of the second switch such that when the controller circuitry operates the second switch to connect the transmitter circuitry to the radio frequency coupling element, the controller circuitry operates the first switch to disconnect the second signal interface of the second radio modem from the radio frequency coupling element.

7. The apparatus of any preceding claim 2 to 6, the second radio modem further comprising a multi-antenna signal processing circuitry, wherein the controller circuitry is further configured to output a signal to the multi-antenna signal processing circuitry, wherein the signal indicates the operation of the first switch, and wherein the multi-antenna signal processing circuitry is configured, in response to the signal acquired from the controller circuitry, to suspend multi- antenna signal processing when the first radio modem is carrying out a transmission.

8. The apparatus of any preceding claim 1 to 4, wherein the first signal line comprises a transmitter line connecting a transmitter circuitry of the first radio modem to the first antenna and a receiver line connecting receiver circuitry of the first radio modem to the first antenna, and wherein the radio frequency coupling element is arranged on the receiver line.

9. The apparatus of any preceding claim, wherein the radio frequency coupling element comprises a radio frequency directional coupler.

10. The apparatus of any preceding claim 1 to 8, wherein the radio frequency coupling element comprises a power divider.

1 1 . The apparatus of any preceding claim, wherein the second signal interface is an antenna diversity reception signal interface configured to receive a diversity radio signal through the first antenna.

12. The apparatus of any preceding claim, wherein the first signal interface and the second signal interface are configured to receive multiple-input- multiple-output radio signals through the first antenna and the second antenna.

13. The apparatus of any preceding claim, wherein the apparatus is a terminal device of a cellular communication system.

14. The apparatus of any preceding claim, wherein the first radio modem is configured to operate according to a first cellular radio access technology, and wherein the second radio modem is configured to operate according to a second cellular radio access technology different from the first cellular radio access technology.

15. The apparatus of claim 14, wherein the first cellular radio access technology utilizes time division principles.

16. The apparatus of any preceding claim, further comprising a first subscriber identity module interface configured to connect a first subscriber identity module to the first radio modem and a second subscriber identity module interface configured to connect a second subscriber identity module to the second radio modem.

17. The apparatus of any preceding claim, wherein the first radio modem and the second radio modem are configured to communicate radio frequency signals simultaneously.

18. A method comprising:

coupling a first antenna of a radio apparatus to a first signal line connecting the first antenna to a first radio modem of the radio apparatus;

coupling a second antenna of the radio apparatus to a first signal interface of a second radio modem via a second signal line; and

coupling, simultaneously with coupling the first antenna to the first signal line, the first antenna to a third signal line connecting the first antenna to a second signal interface of the second radio modem.

19. The method of claim 18, further comprising operating a first switch arranged on the third signal line to disconnect the second signal interface of the second modem from the first antenna when the first radio modem is carrying out a transmission.

20. The method of claim 18 or 19, further comprising switching the first radio modem between a transmission mode and a reception mode.

21 . The method of claim 20, further comprising synchronizing the operation of the first switch with the switching of the first radio modem between the transmission mode and the reception mode.

22. The method of any preceding claim 19 to 21 , further comprising operating a second switch arranged on the first signal line to switch either a transmitter circuitry or a receiver circuitry of the first radio modem to the first antenna.

23. The method of claim 22, further comprising synchronizing the operation of the first switch with the operation of the second switch such that when the second switch is operated to connect the transmitter circuitry to the first antenna, the first switch is operated to disconnect the second signal interface of the second radio modem from the first antenna.

24. The method of any preceding claim 18 to 23, further comprising operating a multi-antenna signal processing circuitry of the second radio modem to suspend multi-antenna signal processing when the first radio modem is carrying out a transmission.

25. The method of any preceding claim 18 to 21 , wherein the first signal line comprises a transmitter line connecting a transmitter circuitry of the first radio modem to the first antenna and a receiver line connecting receiver circuitry of the first radio modem to the first antenna, the method further comprising coupling the third signal line to the first antenna through the receiver line.

26. The method of any preceding claim 18 to 25, wherein the coupling of the first antenna simultaneously to the first signal line and to the third signal line is realized by using a radio frequency directional coupler.

27. The method of any preceding claim 18 to 25, wherein the coupling of the first antenna simultaneously to the first signal line and to the third signal line is realized by using a power divider.

28. The method of any preceding claim 18 to 27, further comprising configuring the second signal interface to receive a diversity radio signal through the first antenna.

29. The method of any preceding claim 18 to 28, further comprising configuring the first signal interface and the second signal interface to receive multiple-input-multiple-output radio signals through the first antenna and the second antenna.

30. The method of any preceding claim 18 to 29, wherein the radio apparatus is a terminal device of a cellular communication system.

31 . The method of any preceding claim 18 to 30, further comprising configuring the first radio modem to operate according to a first cellular radio access technology and the second radio modem to operate according to a second cellular radio access technology different from the first cellular radio access technology.

32. The method of claim 31 , further comprising configuring the first radio modem to operate according to time division principles.

33. The method of any preceding claim 18 to 32, further comprising configuring a first subscriber identity module interface to connect a first subscriber identity module to the first radio modem and a second subscriber identity module interface to connect a second subscriber identity module to the second radio modem.

34. The method of any preceding claim 18 to 33, further comprising configuring the first radio modem and the second radio modem to communicate radio frequency signals simultaneously.

35. An apparatus comprising means for causing the apparatus to carry out the method according to any preceding claim 18 to 34.

36. A computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into the computer, execute a computer process comprising: triggering a transmission mode of a first radio modem utilizing time division duplexing and, as a consequence, causing disconnection of a second radio modem from a radio frequency coupling element and from a first antenna shared by the first radio modem and one of a plurality of signal interfaces of a second radio modem;

triggering a reception mode of the first radio modem and, as a consequence, causing simultaneous connection of the first radio modem and the second radio modem to the radio frequency coupling element and the first antenna.