WO2003030386A1

WO2003030386A1 - Circuit arrangement, switching module comprising said circuit arrangement and use of switching module

Info

Publication number: WO2003030386A1
Application number: PCT/DE2002/003687
Authority: WO
Inventors: Christian Block; Holger FLÜHR; Kurt Wiesbauer; Johann Riedler; Heinz Ragossnig; Heinz Florian; Günther GREIER
Original assignee: Epcos Ag
Priority date: 2001-09-28
Filing date: 2002-09-30
Publication date: 2003-04-10
Also published as: JP2005505188A

Abstract

The invention relates to a circuit arrangement comprising an antenna input (1), a signal input (2), a signal output (3), in addition to a switching unit (4). In said arrangement, the antenna input (1) is connected to a first protective device (6) against electrostatic discharges (ESD), said protective device (6) having an antenna input (111) and a switch output (112), which are interconnected by a line (113). A voltage limiting element (114) is connected to ground (8) in parallel with the line (113). The advantage of the inventive circuit arrangement is that the protective device (6) has a low insertion loss. The invention also relates to a switching module and to the use of said switching module as a front-end module.

Description

description

Circuit arrangement, switching module with the circuit arrangement and use of the switching module

The invention relates to a circuit arrangement with a switching unit, which has an antenna input, a signal input and a signal output. In addition, the switching unit has a control line, with the help of which the optional switching of a connection between the antenna input and the signal input or the signal output can be controlled. The antenna input of the circuit arrangement is connected to a protective device against electrostatic discharges.

Circuit arrangements of the type mentioned are often used as multiband front-end modules for mobile telephones. In this application, they are connected to the antenna of the mobile phone at the antenna input. Touching the antenna by an electrically charged user can cause electrostatic

Lead discharge, as they are also known under the name "Electrostatic Discharge ESD". These electrostatic discharges can generate voltage peaks that are suitable for destroying the circuit arrangement. Accordingly, it is necessary to equip circuit arrangements of the type mentioned at the outset with a protective device against ESD.

From the document WO 00/57515, circuit arrangements of the type mentioned at the outset are known which are equipped with a protective device against ESD. The protection device is formed by an electrical high-pass filter, in which a capacitance is connected in series and an inductance is connected in parallel to the antenna input path.

The known circuit arrangement has the disadvantage that with

With the help of the ESD protection device, only the ESD pulse coupled directly into the circuit arrangement via the antenna is can be reduced. In addition to the pulse entering the viewing arrangement directly via the antenna, an electrostatic discharge can also generate a high voltage on the circuit arrangement via ground coupling. This can be done, for example, in that the control input usually used in a switch is either at a high potential (high) or at a low potential (low). The high potential is defined in that it is, for example, 2.3 V above the ground potential of the circuit arrangement. Since in a mobile phone, just like in many other devices based on signal transmission by means of antennas, the signal coupling runs from the antenna to the earth of the system, an electrostatic discharge can also have a direct effect on the ground potential of the circuit arrangement in the case of a circuit arrangement mentioned at the beginning. Via the direct coupling of a control line to the ground through the "high" condition, the voltage pulse resulting from an electrostatic discharge can have an effect on the circuit arrangement in addition to the path via the antenna and also via the control line.

The known circuit arrangement is not protected against these effects.

In addition, the high-pass filter used in the known circuit arrangement has the property of being a very simply constructed filter which allows all frequency components of a signal to pass almost unhindered from a certain cut-off frequency. In general, however, only a very narrow frequency range is decisive for the further processing of the signals captured by the antenna in a mobile phone. For example, frequencies between approximately 1 and 2 GHz are used in mobile telephones according to the GSM, PCN or PCS standard. All other frequencies captured by the antenna are rather annoying and must therefore be filtered out. Accordingly, at least one bandpass filter is necessary in order to make the signals collected by the circuit arrangement mentioned above processable for a mobile phone. The high-pass filter arranged in the known circuit arrangement can only cut off frequencies below a cut-off frequency. It must therefore be followed by at least one filter circuit in order to cut out the frequency range of interest for the mobile phone from the signals picked up by the antenna.

Accordingly, the known circuit arrangement has the disadvantage that the high-pass filter circuit used to protect against ESD has an insertion loss, due to which the useful signals also experience a certain amount of attenuation, but the transmitted frequency band is not yet clipped. Accordingly, the known circuit arrangement in conjunction with the further filtering required has the disadvantage of an overall high insertion loss.

The aim of the present invention is therefore to provide a circuit arrangement of the type mentioned at the beginning, in which the protective device against electrostatic discharges has a low insertion vaporization.

This goal is achieved by a circuit arrangement according to claim 1. Further advantageous embodiments of the invention and a switching module and the use of the switching module can be found in the dependent claims.

A circuit arrangement is described which contains a switching unit with an antenna input, a signal input and a signal output. The switching unit is suitable for connecting the antenna input to the signal input or the signal output in an electrically conductive manner. In addition, the antenna input is connected to a first protective device against electrostatic discharge.

The first protective device against electrostatic discharges has an antenna input and a switch output, the switch output having the antenna input Switch unit is connected. The antenna input of the protection device and the switch output of the protection device are connected by a line. A voltage limiting element, which can be, for example, a varistor, a spark gap or a surge arrester, is connected in parallel to ground. The voltage limiting element is connected to a ground.

With the help of the voltage limiting element, overvoltages present at the antenna input of the protective device can be derived against ground. This means that the essential function of the protective device is to limit the voltage present at the antenna input of the circuit unit.

The circuit arrangement according to the invention has the advantage that a filter function is dispensed with due to the special design of the protective device, as a result of which the insertion loss of the first protective device is low.

However, the protective mechanism of the circuit arrangement can be improved by connecting an inductor in parallel with the voltage limiting element. This inductance is in turn connected to the ground. The inductance connected in parallel to the voltage limiting element is suitable for deriving very low frequencies to ground. The protective device thus transmits high frequencies unchanged from the antenna input to the switching unit.

Furthermore, it is advantageous if a first inductance is connected between the antenna input and the voltage limiting element and a second inductance is connected in series with the line between the voltage limiting element and the switch output. By means of these two additional inductances, the impedance of the protective device can be adapted to the value of 50 Ω which is usual in the high frequency range. In particular, by a suitable choice of the inductances between 0 and 47 nH, a low insertion loss of the first protective device <0.3 dB can be achieved.

In addition, a control line can be arranged on the switching unit, which controls the switch position of the switching unit.

In addition, protection against overvoltages (ESD protection) can be further improved by also connecting the control line of the circuit arrangement to a second protective device against electrostatic discharges. As a result, the overvoltages applied to the control unit via ground couplings and present at the control line can be reduced particularly effectively.

The protective devices against electrostatic discharges are advantageously connected to a ground connection, into which the overvoltages of the electrostatic discharge can be derived.

The switching unit can be, for example, a voltage-controlled switch, as is usually used in mobile telephones due to its low power consumption.

A gallium arsenide switch is particularly suitable as the switching unit.

The switching unit can also have a plurality of signal inputs and outputs. Accordingly, several control lines are required.

The gallium arsenide switch can also be provided with a decoder, which can be used to reduce the number of control lines. Such a decoder usually requires a power supply that is connected via a supply line. The ESD protection of one Such a circuit can be further improved by connecting the supply line to a third protective device against electrostatic discharge.

A switching module is also specified which contains a circuit arrangement according to the invention. The switch module also contains a multilayer ceramic substrate with integrated passive components that form electrical frequency filters. These frequency filters are assigned to the signal inputs and outputs. The switching unit is arranged on the top of the multilayer ceramic substrate and can be implemented, for example, with the aid of PIN diodes or in the form of a gallium arsenide switch. Furthermore, the first and second protective devices against electrostatic discharges are integrated in the switching module.

The circuit arrangement can also contain frequency filters which are assigned to individual signal inputs or signal outputs. They are particularly suitable for filtering the frequencies picked up by the antenna in a mobile phone so that the filtered signals passed through the signal output can be processed further by the mobile phone. The same applies to the signal inputs of the circuit arrangement that are used in a mobile phone to send voice signals generated in the mobile phone to a receiver via the antenna.

A second protective device against electrostatic discharge is, for example, the use of a varistor which is connected in parallel with the control line and which is connected to a ground potential. From a certain limit voltage, such a varistor has a very low ohmic resistance, so that overvoltages can be diverted to ground. In particular, varistors with a low switching voltage are suitable, since in this case the circuit arrangement occurring during a voltage pulse residual stress is lowest. It is therefore possible to use varistors with a varistor voltage between 4 and 20 V. Accordingly, the terminal voltage loading the circuit arrangement in the case of a voltage pulse is approximately 8 to approximately 50 V. As a result, the circuit arrangement can be reliably protected against destruction in the event of an ESD pulse.

Furthermore, it is possible to use a switching spark gap or a Zener diode as the second protective device against electrostatic discharge.

Furthermore, the invention provides a circuit arrangement in which the antenna input is connected to an antenna and in which the signal output is connected to a receiving amplifier of a mobile phone and the signal input is connected to a transmitting amplifier of a mobile phone.

A switching module is also specified which contains a circuit arrangement according to the invention. The switching module also contains a multilayer ceramic substrate with integrated passive components that form electrical frequency filters. These frequency filters are assigned to the signal inputs and outputs. The switching unit is arranged on the upper side of the multilayer ceramic substrate and can be implemented, for example, with the aid of PIN diodes or also in the form of a gallium arsenide switch. Furthermore, the first and optionally second protective device against electrostatic discharge is integrated into the switching module.

The switching module has the advantage that, due to the integration of the passive components in the ceramic substrate and the integration of the protective device into the switching module, a high level of integration is achieved, which is advantageous to the

Space requirement of the switching module affects. The integration of the first and possibly the second protective device into the Switching module can take place, for example, by building these components on the surface of the ceramic substrate next to the switching unit.

In particular, it is also advantageous to use the switching module as a front-end module in a mobile phone.

The invention is explained in more detail below with the aid of exemplary embodiments and the associated figures.

FIG. 1 shows an example of a circuit arrangement according to the invention in a basic circuit diagram.

FIG. 2 shows an example of a further circuit arrangement according to the invention in a basic circuit diagram.

FIG. 3 shows the use of the circuit arrangement according to the invention in a mobile telephone based on a basic circuit diagram.

FIG. 4 shows an example of a switching module according to the invention in a schematic longitudinal section.

It applies to all figures that the same reference numerals designate the same elements.

Figure 1 shows a circuit arrangement with a switching unit 4, which is provided with a ground 8. The switching unit 4 has an antenna input 1, which is connected to an antenna 18. The antenna input 1 is connected to a first protective device 6 against electrostatic discharge (symbolized by the lightning in FIG. 1). The switching unit 4 contains at least one control line 5 which controls the switching process for connecting the antenna input 1 to the signal inputs 2 or the signal outputs 3 of the switching unit 4. Three control lines 5 are shown in FIG. At least one of these control Lines 5 is provided with a second protective device 7 against electrostatic discharge. This second protective device 7 is designed in the form of a varistor, which is connected to ground 8. The switching unit 4 shown in FIG. 1 also has a decoder, for which a supply line 11 is required. The supply line 11 is connected to a supply voltage + Vcc. In addition, the supply line 11 is connected to a third protective device 12 against electrostatic discharge. The protective device 12 can be a varistor, for example, which is connected to the ground 8.

The first protective device 6 has an antenna input 111 and a switch output 112. Antenna input 111 and switch output 112 are connected to one another by a line 113. Two inductors L1 and L2 are connected in series with line 113. These two inductors L1, L2 serve to match the impedance to the value of 50 Ω. Between the inductors L1, L2 branch in parallel

Line 113 a further inductor L3 and a voltage limiting element 114. The voltage limiting element 114 can be a varistor, for example. The inductance L3 and the varistor are connected to the ground 8 of the circuit arrangement. The voltage coupled into the switching unit 4 is limited by the varistor. Of particular importance at this point is the switching voltage of the varistor, which should be between 4 and 8 V. The lower the switching voltage of the varistor, the better the overvoltages can be derived and thus suppressed with regard to the switching unit 4. A switching voltage of the varistor of 6 V or less is advantageous. This also applies to the second and third protective devices 7, 12. The switching voltage of the varistor indicates the residual voltage that remains from the high-voltage pulse and that is passed through the protective device to the switching unit 4. The inductances in the first protective device preferably have the following values:

Ll = from 0 to 5 nH L2 = from 0 to 5 nH L3 = from 0 to 47 nH

In particular, a suitable choice of inductances (Ll = 0 nH, L2 = 1 nH, L3 = 47 nH) enables insertion loss of the first protective device to be less than 0.3 dB.

FIG. 2 shows a voltage-controlled GaAs switch 9 with an antenna input 1, to which an antenna 18 is connected. The GaAs switch 9 has transmitter inputs TX _] _, TX2 and receiver inputs RXi, RX2 and RX3. The GaAs switch 9 is controlled via control inputs S ^, S2, S3, S4, S5. The control takes place in such a way that exactly one of the control inputs S _] _, S2, S3, S4 and S5 is set to "high", while the other control inputs are set to "low". Due to the decoder 10 connected to the GaAs switch 9, the

Number of inputs required can be reduced. The decoder 10 can be, for example, a 1 out of 5 decoder. It has control inputs E] _, E2 and E3 as well as control outputs A] _, A2, A3, A4 and A5. The control outputs A ^, A2, A3, A4 and A5 are connected by control lines 24 to the control inputs S] _, S2, S3, S4, S5 of the GaAs switch 9.

The control inputs E] _, E2 and E3 of the decoder 10 are connected to control lines 5.

The exemplary decoding of a logic signal present at the inputs E ^, E2 and E3 of the decoder 10 into signals suitable for controlling the GaAs switch 9 and present at the control inputs S _] _, S2, S3, S4, S5 of the GaAs switch 9 Signals is described by the following translation table: Table 1: Logical states of the control inputs S] _, S2, S3, S4, S5 depending on the logic states at the control inputs E ^, E2 and E3. It means 1 = "high" and 0 = "low".

The transmitter inputs TX ^, X ₂ correspond to the signal inputs 2 from FIG. 1. The receiver inputs RX] _, RX _/ and RX3 correspond to the signal outputs 3 from FIG. 1.

FIG. 3 shows a switching module with a GaAs switch 9, which has an antenna input 1 and two signal inputs 2 and three signal outputs 3. In addition, the switching module has two low-pass filters 13, 14, the low-pass filter 13 for the GSM frequency band and the low-pass filter 14 for the PCN / PCS frequency band. The GaAs switch 9 optionally connects one of the inputs / outputs 2, 3 to its antenna input 1. The switching module also has bandpass filters 15, 16, 17, which are connected to the signal outputs 3. The bandpass filter 15 is adapted to the GSM frequency, the bandpass filter 16 to the PCN frequency and the bandpass filter 17 to the PCS frequency.

There are the signal inputs 2 of the GaAs switch 9 with transmitter amplifiers 19 electrically connected. The transmitter amplifiers 19, like the low-pass filters 13, 14, are adapted to the radio frequencies GSM or PCN / PCS. The signal outputs 3 are electrically conductively connected to receiver amplifiers 19a via the bandpass filters 15, 16, 17, the receiver amplifiers 19a being adapted to the frequency bands GSM, PCN or PCS. The antenna input 1 of the GaAs Switch 9 is connected to an antenna 18. The signals received by the antenna 18 can now be fed to either the bandpass filter 16, the bandpass filter 17 or the bandpass filter 15 by means of the GaAs switch 9, where they are filtered depending on the radio frequency used and further processed in amplifiers 19a. The signals supplied by the transmitter amplifiers 19 are filtered by the low-pass filters 13, 14 and optionally supplied to the antenna 18 for transmitting a signal.

FIG. 4 shows a switching module with a multilayer ceramic substrate 20, in which passive components 21, 22, 23 are integrated. These passive components 21, 22, 23 can be, for example, resistors 21, capacitors 22 and inductors 23. The multilayer ceramic substrate 20 can be designed in a manner known per se. Ceramic layers 30 stacked on top of one another, which are separated from one another by metallic layers 31, can be used as a multilayer ceramic substrate 20. Some of the metallic layers 31 are connected to one another by vias 32 running inside the ceramic layers 30. On the top of the ceramic substrate 20, a switching unit 4 is mounted, which can be, for example, a gallium arsenide multiple switch mounted in flip-chip technology.

The switching unit 4 can be attached and electrically contacted, for example, by gluing and additional wire bonding. A GaAs multiple switch is preferably used as the switching unit 4. Such a switch can have an insertion loss of 0.8 dB in the frequency range between 1 and 2 GHz. This can be an integrated circuit with FET, based on gallium arsenide, the pin surfaces of which can be connected to the ceramic substrate 20 by soldering. The switching unit 4 can also be attached to the multilayer ceramic substrate 20 and electrically connected by means of wire bonding. A connection by means of soldering is preferably used if the switching unit 4 is used with an additional housing.

The passive components 21, 22, 23 can form the filters 13, 14, 15, 16, 17 required according to FIG.

In addition to the switching unit 4, the first protective device 6 and the second protective device 7 are also mounted on the surface of the substrate 20. This achieves a high degree of integration for the switching module according to the invention, which has a positive effect on the space requirement of the switching module.

Such a switching module can be used, for example, in mobile telephones, which is why the advantageous use of the switching module according to the invention as a front-end module in a mobile radio device is a further subject of the invention.

The invention is not limited to the examples mentioned for the second and third protective device, rather all conceivable protective devices can be used in the circuit arrangement according to the invention. In addition, the circuit arrangement or the switching module is not restricted to use in mobile telephones.

LIST OF REFERENCE NUMBERS

1 antenna input

2 signal input 3 signal output

4 switching unit

5 control line

6, 7, 12 first, second, third protection device

8 ground 9 gallium arsenide switch

10 decoders

11 supply line 13, 14 low-pass filter

15, 16, 17 bandpass filter 18 antenna

19 transmitter amplifiers

19a receiving amplifier

20 multilayer ceramic substrate 21 resistance 22 capacitance

23 inductance

24 control line

30 ceramic layers

31 metallic layers 32 vias

TX _} _, TX ₂ transmitter inputs

RX _] _, RX ₂ , R 3 receiver inputs

S _] _, S ₂ , S3, S4, S5 control inputs of the switch

A _] _, A ₂ , A3, A4, A5 control outputs of the decoder E ^, E _{2 /} E3 control inputs of the decoder

Vcc supply voltage

111 antenna input

112 switch output

113 line 114 voltage limiting element

Ll, L2, L3 inductors

Claims

claims

1. Circuit arrangement

- With an antenna input (1), a signal input (2) and a signal output (3),

- With a switching unit (4), the antenna input (1) either with the signal input (2) or the signal output

(3) can connect

- in which the antenna input (1) is connected to a first protective device (6) against electrostatic discharges and,

- In which the first protective device (6) has an antenna input (111) and a switch output (112) which are connected to one another by a line (113) and in which in the first protective device (6) in parallel with the line (113) Voltage limiting element (114) is connected to a ground (8).

2. Circuit arrangement according to claim 1, in which a parallel to the voltage limiting element (114)

Inductance (L3) is switched.

3. Circuit arrangement according to one of claims 1 or 2, in which between the antenna input (111) and the voltage limiting element (114) a first inductor (L1) and between the voltage limiting element (114) and the switch output (112) a second inductor ( L2) is connected in series to line (113).

4. Circuit arrangement according to one of claims 1 to 3, wherein the first protective device (6) has an insertion loss <0.3 dB.

5. Circuit arrangement according to one of claims 1 to 4,

- Which has a control line (5) which controls the switch position of the switching unit (4) and,

- In which the control line (5) is connected to a second protective device (7) against electrostatic discharge.

6. Circuit arrangement according to one of claims 1 to 5, in which the protective devices (6, 7) are connected to a ground (8).

7. Circuit arrangement according to one of claims 1 to 6, wherein the switching unit (4) is a voltage-controlled switch.

8. Circuit arrangement according to claim 7, wherein the switching unit (4) is a gallium arsenide switch (9).

9. Circuit arrangement according to one of claims 1 to 8, in which a decoder (10) is additionally provided, which has a supply line (11) and in which the supply line (11) is provided with a third protective device (12) against electrostatic discharges.

10. Circuit arrangement according to one of claims 1 to 9, which additionally contains frequency filters (13, 14, 15, 16, 17), which are each assigned to a signal input (2) or a signal output (3) and are each connected in series ,

11. Circuit arrangement according to one of claims 5 to 10, in which ^' the voltage limiting element (114) is a varistor.

12. Circuit arrangement according to one of claims 5 to 10, in which the second protective device (7) is a spark gap, a varistor or a Zener diode.

13. Circuit arrangement according to one of claims 11 to 12, in which at least one of the varistors has a switching voltage which is less than 6 V.

14. Circuit arrangement according to one of claims 1 to 13, wherein the antenna input (1) with an antenna (18), the signal input (2) with a transmission amplifier (19) and the

Signal output (3) is connected to a receiving amplifier (19a).

15. Switch module with a circuit arrangement according to one of claims 1 to 14,

comprising a multilayer ceramic substrate (20) with integrated passive components (21, 22, 23) which form frequency filters (13, 14, 15, 16, 17),

- On the top of which the switching unit (4) is arranged, - and in which the first protective device (6) is integrated.

16. Use of a switching module according to claim 15 as a front end module in a mobile phone.