WO2004088865A1

WO2004088865A1 - Circuit arrangement for a communication terminal with a multi-mode operation

Info

Publication number: WO2004088865A1
Application number: PCT/EP2004/002222
Authority: WO
Inventors: Damian Wisniowski; Carlos Civeira Munoz
Original assignee: Siemens Aktiengesellschaft
Priority date: 2003-04-02
Filing date: 2004-03-04
Publication date: 2004-10-14
Also published as: DE10315046B4; TW200425649A; DE10315046A1

Abstract

The aim of the invention is to simplify the circuit arrangement which is used to connect an antenna arrangement to an amplifier arrangement in a mobile communication terminal, comprising a reception path (RX) which comprises a reception filter device which is used to select reception signals, and also comprising a transmitter path (TX) which comprises a transmitter filter device which is used to attenuate transmitter signals in relation to the reception path, which are connected to the antenna arrangement by means of a common line. Said aim is achieved by virtue of the fact that the transmitter path (TX), which is used to guide transmitter signals, is formed by at least two mobile radio standards and one section of the transmitter path comprises two re-united branches (FDD, TDD) which are different with respect to the attenuation of the transmitter signals vis a vis the reception path (RX), and a section of the transmitter path (TX) is fitted with switches (S1, ...., S12) in such a manner that they can be switched for the transmitter signals between the two branches (FDD, TDD).

Description

description

Circuit arrangement for a communication terminal with multi-mode operation

The invention relates to a circuit arrangement for connecting an antenna arrangement to an amplifier arrangement in a communication terminal, having a reception path which has a reception filter device for selecting reception signals, and a transmission path which has a transmission filter device for damping transmission signals with respect to the reception path are each connected to the antenna arrangement via a common line, and to a communication terminal equipped with such a circuit arrangement.

Such a circuit arrangement is also generally referred to with the term “front end” and describes a hardware which is arranged between the antenna arrangement, which can also comprise several antennas, and the amplifier arrangement with possibly several amplifiers. This hardware includes frequency-fixed filters, duplexers and switches ,

A general distinction is made in communication systems between full duplex and non-full duplex systems. Examples of full-duplex systems that are characterized by simultaneous transmission and reception of signals are IS95, CDMA2000 and UMTS UTRA FDD. In the case of non-full-duplex systems, simultaneous sending and receiving is not provided. Examples of this are UMTS UTRA TDD, GSM and DECT.

Different frequency bands should be able to use communication terminals suitable for multi-mode, whereby both full-duplex systems and non-full-duplex systems can be used. In both types of communication systems, the fact that both the Transmit as well as the receive path makes use of the same antenna arrangement, so that a decoupling of the transmit and receive path has to be accomplished. This is done primarily with the help of the transmit filter device, which avoids that signals or noise to be emitted cause disturbances which affect the receive path.

With regard to the decoupling of the transmission and reception path, there are different requirements for full-duplex and non-full-duplex systems. In order to suppress unwanted frequency components of a transmission signal that lie outside the actual transmission band and not to transmit them via the antenna, non-full duplex systems require a tie pass, whereas full duplex systems provide a band pass. The low pass for the transmission branch in a non-full-duplex system is used to suppress harmonic harmonics of a transmission signal. In this connection, the reception path of the non-full-duplex system has a bandpass filter for blocker suppression.

In the full-duplex system, the transmission filter device has to meet comparatively higher requirements, with regard to the band attenuation, than with a non-full-duplex system, in particular its low-pass filter. The reason for this is that interference can also be suppressed when transmitting and receiving at the same time. Such interference can arise between transmission signals and reception signals received at the same time.

In order to enable multi-mode operation with communication terminals, the previous procedure was to provide a path with the associated transmit filter and amplifier for each frequency band. Non-full duplex paths and full duplex paths were also separated. This means an enormous amount of hardware to implement multi-mode circuit arrangements of the type mentioned at the beginning. Proceeding from this, the object of the invention is to provide a simplified circuit arrangement for connecting an antenna arrangement to an amplifier arrangement in a communication terminal and to provide a communication terminal therefor.

With regard to the circuit arrangement, the object is achieved by a circuit arrangement for connecting an antenna arrangement to an amplifier arrangement in a communication terminal, with a reception path which has a reception filter device for selecting reception signals, and a transmission path which has a transmission filter device for damping transmission signals with respect to the reception path has, which are each connected to the antenna arrangement via a common line, the transmission path being designed to carry transmission signals of at least two mobile radio standards and a section of the transmission path having two reuniting branches which differ in terms of their attenuation of the transmission signals compared to the Distinguish the reception path, and the section of the transmission path is equipped with switches in such a way that the transmission signals can be switched between the two branches.

The invention therefore assumes that the transmission path of the

Circuit arrangement can be used for several mobile radio standards. Depending on the mobile radio standard being used, it is possible to switch between two branches of the transmission path in order to provide the required attenuation in relation to the reception path.

This procedure is based on the fact that the attenuation requirements of different mobile radio standards differ from each other, so that one branch of a mobile radio standard with a lower damping requirement and the other branch of a mobile radio standard with a higher damping requirement of the transmission path can be used. For this purpose, you can switch between the two branches.

In a preferred embodiment, one branch with higher attenuation is designed for full duplex operation and the other branch with lower attenuation is designed for non-full duplex operation. This is based on the fact that the attenuation requirements for the transmission path are lower in a non-full-duplex system than in a full-duplex system. There are therefore lower suppression requirements for, for example, a low-pass filter of the branch with lower attenuation, so that this can be implemented with significantly lower passband attenuation. In this respect, there are favorable values for the passband attenuation for the transmission path in the circuit arrangement. Losses that occur on the way from the amplifier arrangement to the antenna arrangement are to be regarded as particularly disadvantageous since they lead to a much higher power consumption of the amplifier arrangement, which results in a significantly shorter battery time. Problems with heat dissipation can also arise.

The section of the transmission path preferably has a low-pass filter common to all transmission signals. This has the advantage that transmit signals of a mobile radio standard with lower attenuation requirements can only be carried through the low-pass filter, while transmit signals of a mobile radio standard with higher attenuation requirements pass through further filter elements which, in combination with the common low-pass filter, meet the attenuation requirements. The two branches of the transmission path section must be adapted to these requirements.

The higher attenuation branch can have a bandstop filter which is combined with the common lowpass filter, ie transmission signals first pass through the common lowpass filter and then through the bandstop filter. The use of a bandstop filter has the particular advantage that Noise signals from the amplifier arrangement are attenuated to a suitable value. The bandstop filter is preferably tunable. In this way, the filter properties of the branch of the transmission path which has a higher attenuation can be adapted to different mobile radio standards.

As an alternative to the bandstop filter, the higher attenuation branch can also have a bandpass filter, which can preferably be tuned.

In an alternative embodiment, the section of the transmission path can have a first bandpass filter common to all transmission signals and the branch with higher attenuation can have a second bandpass filter. In this case, such a bandpass filter can be used for the common first bandpass filter, which has a lower attenuation than that which is required, for example, in full-duplex operation for isolation from the reception path. The second bandpass filter in the higher attenuation branch then ensures that the attenuation requirements for a full duplex system, for example, are met. Both bandpass filters can preferably be tuned to adapt to different mobile radio standards.

In a further alternative embodiment, the section of the transmission path can have a low-pass filter common to all transmission signals and the branch with higher attenuation can have a high-pass filter. Both filters can preferably be tuned and correspond in function to the two in

Series switched bandpass filters of the embodiment explained above.

The switches provided for switching over between the two branches of the transmission path can lie outside the common line which is present between the antenna arrangement and the connection point between the transmission and reception path. In this case, all transmission signals pass through at least two switches regardless of the branch of the transmission path used in each case and experience the associated insertion loss of the switches. With such a circuit arrangement, there is an optimization for the reception path since reception signals do not have to pass a switch.

Alternatively, one of the switches can also be in the common line. This opens up the possibility, for example, of separating the path of lower attenuation from an intended duplexer in terms of circuitry, so that due to this arrangement there is already considerable isolation between the branch of lower attenuation of the transmission path and the reception path. This has the advantage that any receive filters are subject to lower attenuation requirements with regard to their attenuation compared to transmit signals of the transmit path.

Another advantage of the invention is that the communication terminal, which can be a mobile communication terminal or a base station, is flexible with regard to the usable mobile radio standards. An adaptive front end is provided which can support a large number of frequency bands and standards within practical limits, which are determined by the frequency properties of the filters. Such one

The front end is particularly favorable with regard to the implementation of projects such as "World Phone" and "Software Defined Radio".

Embodiments of the invention are explained in more detail below with reference to the drawings. Show it:

1 and 2 circuit arrangements for a multimode operation of a communication terminal with a branched transmission path, a first switch in the transmission path and a second switch in a common seed transmission / reception path are arranged,

Figures 3, 4, 5, 6 each have circuit arrangements for a multi-mode operation of a communication terminal, in which a transmission path is branched and a first and a second switch are provided in the transmission path.

All of the circuit arrangements shown in FIGS. 1 to 6 have in common that a bandpass filter BP1 of a reception path RX is combined with a filter associated with a transmission path TX to form a duplexer. The bandpass filter BP1 of the reception path RX is designed to be tunable in order to enable reception of signals of different mobile radio standards and due to its different frequency.

The transmission path TX of all exemplary embodiments for circuit arrangements lies between an amplifier arrangement

(not shown) and an antenna arrangement (not shown), which is used both for receiving and for transmitting signals.

In the circuit arrangement according to FIG. 1, the bandpass filter BP1 of the reception path RX is combined with a bandstop filter BS1 of the transmission path TX to form a duplexer. A common line leads from the duplexer to the antenna arrangement. A first switch S1 is provided in this common line. A second switch S2 is located in the transmission path TX. In a first position of the switches S1, S2, transmission signals pass through the band-stop filter BS1, while in a second position the switches S1, S2 transmit signals pass directly from the second switch S2 to the first switch S1 and do not experience any filter attenuation in this way. From the switch S2 in the direction opposite to a signal direction of the transmission path TX is in the transmission path TX a low-pass filter TP1 is arranged, which is passed through by all transmission signals. The transmission signal direction is from right to left in all the circuit arrangements in the figures.

According to FIG. 1, this results in a branching of the transmission path between switches S1 and S2, one branch TDD having no filter damping and the other branch FDD having filter damping, which is determined by the band-stop filter BS1. The latter branch FDD with higher attenuation can be used for full-duplex operation of an FDD system, while the branch TDD with low attenuation is suitable for a non-full-duplex system, since a required attenuation of harmonics of a transmission signal from the common low-pass filter TP1 provided. The bandstop filter BS1 is used primarily to suppress noise from the amplifier device in the reception band of the reception path RX.

The embodiment of a circuit arrangement according to FIG. 2 differs from that according to FIG. 1 in that, instead of the low-pass filter TP1, a low-pass filter TP2 is provided, that between two switches S3, S4 is arranged in the branch TDD of lower attenuation from FIG. Furthermore, the bandstop filter BS1 from FIG. 1 in FIG. 2 is replaced by a bandpass filter BP2, which has the necessary damping properties for full-duplex operation and can be tuned.

The switches S3, S4 take over the function of the switches S1, S2 from the circuit arrangement according to FIG. 1.

FIGS. 3 to 6 have in common that the transmission path TX is branched using switches S5, Sβ,... S12 and S12, which are arranged exclusively in the transmission path TX. In FIGS. 3 and 4, low-pass filters TP3, TP4 each form a duplexer with the band-pass filter BP1, which has the same function as in the circuit arrangement according to FIG. 1. The low-pass filters TP3, TP4 are intended for non-full-duplex operation and have the required attenuation of harmonics of the transmission signals of the communication terminal. In a first position of the switches S5, S6 or S7, S8, transmission signals are passed through a tunable filter, which is embodied in FIG. 3 as a bandpass filter BP3 and in FIG. 4 as a bandstop filter BS2. In a respective second switch position, the transmission signals in the circuit arrangements according to FIGS. 3 and 4 do not pass through any filters, so that the TDD branch with low attenuation is used for the transmission path TX.

The circuit arrangements according to FIGS. 3 and 4 are more favorable than the circuit arrangements according to FIGS. 1 and 2 with regard to the attenuation for received signals, since the received signals do not pass through a switch and, in this respect, do not experience any associated insertion loss.

The bandstop filter BS2 of the circuit arrangement from FIG. 4 is functionally equivalent to the bandstop filter BSl from FIG.

The circuit arrangements according to FIGS. 2 and 3, in which the paths of higher attenuation have the bandpass filters BP2, BP3, have the advantage that signals can be received via the reception path RX, even if their frequency is below the transmission frequency of a currently used mobile radio standard , Mobile radio standards that can be received in the lower frequency range are, for example, DAB, DVB, FM. Examples of combinations of low-frequency reception band and high-frequency transmission band are UMTS TX / GSM 900 RX, GSM 1800 TX / GPS RX, GSM 1900 TX / GPS RX, DECT TX / GPS RX, DECT TX / Bluetooth or DECT TX / WLAN. This pre Parts also apply to the circuit arrangements according to Figures 5 and 6, which are explained below.

In FIG. 5, the bandpass filter BP1 of the reception path RX forms a duplexer with a bandpass filter BP4 of the transmission path, through which all signals pass. Switches S9, S10 cause the transmission path TX to branch. A branch of higher attenuation FDD has a tunable bandpass filter BP5 which, in combination with the bandpass filter BP4 of the duplexer, provides the necessary attenuation properties for full duplex operation. The branch FDD of higher damping is used for transmit signals in a first position of the switches S9, S10. In a second switch position, the transmission signals on the path between switches S9, S10 do not pass through a filter, so that the branch that results has a comparatively lower attenuation that is suitable for non-full-duplex operation. It should be noted that the bandpass filter BP5 between the switches S9 and S10 on the branch FDD of higher attenuation, combined with the bandpass filter BP4 of the duplexer, provides the attenuation required for full-duplex operation. Therefore, the bandpass filter BP4 of the duplexer can be chosen lower in terms of its attenuation values than a bandpass filter which alone effects an attenuation suitable for full duplex operation. This leads to reductions in insertion loss in non-full-duplex operation.

In the circuit arrangement according to FIG. 6, a duplexer is formed by the bandpass filter BP1 of the reception path and a lowpass filter TP5, through which all signals of the transmission path TX pass. The switches S11, S12 correspond to the switches S9, S10 of FIG. 5. The bandpass filter of the higher attenuation branch of FIG. 5 is replaced in FIG. 6 by a high-pass filter HP1. The high-pass filter HP1 together with the low-pass filter TP5 of the duplexer ensures the attenuation required for full-duplex operation, while the low-pass filter TP5 alone provides the necessary attenuation of harmonics in non-full-duplex operation. Switching between the switches S11, S12 takes place in the same way as in the circuit arrangements explained above.

MEMS switches can be used in an advantageous manner for the switches S1-S12, whose very low insertion loss in the range from 0.1 to 0.2 dB are particularly suitable for the invention. For a non-full-duplex transmission mode, a considerable gain in performance in terms of insertion loss is obtained compared to known circuit arrangements. A loss of performance for a full-duplex mode is accepted as a result of the switches S1-S12 used, but this can be kept very low by using the type of switches mentioned. In this respect, the invention makes it possible to provide a front end for multi-mode operation of a communication terminal. A decision as to which branch of the transmission path TX is to be switched should not only depend on whether a non-full-duplex transmission path or a full-duplex transmission path should be activated. Rather, a multi-link mode is generally to be supported, in which a simultaneous reception and transmission of different mobile radio systems or standards is required.

Claims

claims

1. Circuit arrangement for connecting an antenna arrangement to an amplifier arrangement in a communication terminal, with a reception path that has a reception filter device for selecting reception signals, and a transmission path that has a transmission filter device for damping transmission signals with respect to the reception path, each with the antenna arrangement are connected via a common line, characterized in that the transmission path (TX) is designed to carry transmission signals of at least two mobile radio standards and a section of the transmission path (TX) has two reuniting branches (FDD, TDD), which differ in terms of their attenuation of the transmission signals compared to the reception path (RX), and the section of the transmission path (TX) is equipped with switches (S1, S2, S3, ..., S12) in such a way that the transmission signals between the two branches (FDD, TDD) can be switched.

2. Circuit arrangement according to claim 1, characterized in that the one branch with higher attenuation is designed for full-duplex operation and the other branch with lower attenuation for non-full-duplex operation.

3. A circuit arrangement according to claim 1 or 2, characterized in that the section of the transmission path has a low-pass filter (TP1, TP3, TP4, TP5) common to all transmission signals.

4. Circuit arrangement according to claim 3, characterized in that the higher attenuation branch (FDD) has a bandstop filter (BS1, BS2).

5. Circuit arrangement according to claim 4, characterized in that the bandstop filter (BSl, BS2) is tunable.

6. Circuit arrangement according to one of claims 1 to 4, characterized in that the branch (FDD) higher attenuation has a bandpass filter (BP2, BP3, BP4, BP5).

7. Circuit arrangement according to claim 6, characterized in that the bandpass filter bandpass filter (BP2, BP3, BP4, BP5) is tunable.

8. Circuit arrangement according to one of claims 1 or 2, characterized in that the section of the transmission path has a transmission band common first bandpass filter (BP4) and the branch (FDD) higher attenuation a second bandpass filter (BP5).

9. Circuit arrangement according to claim 8, characterized in that the bandpass filters (BP4, BP5) are tunable.

10. Circuit arrangement according to one of claims 1 or 2, characterized in that the section of the transmission path (TX) has a low-pass filter (TP5) common to all transmission signals and the branch FDD) higher attenuation has a high-pass filter (HP1).

11. Circuit arrangement according to claim 10, characterized in that the low-pass filter (TP5) and the high-pass filter (HP1) are tunable.

12. Circuit arrangement according to one of claims 1 to 11, characterized in that the switches (S2, S4, ..., S12) are outside the common line.

13. Circuit arrangement according to one of claims 1 to 11, characterized in that one of the switches (Sl, S3) is in the common line,

14. Communication terminal equipped with a circuit arrangement according to one of claims 1 to 13.