FR2816472A1 - Multiband mobile telephone having transmitter with power amplifier chain with individual amplifiers settable saturated/non saturated regime providing separate frequency bands. - Google Patents

Abstract

The multiband mobile telephone has a power amplifier chain (300) with amplifier stages (301 to 303) in series. A unit (401,402) switches each of the amplifier stages from a saturated regime to a linear regime for each of the stages. The two modes correspond to different frequency bands.

Description

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Mobile phone with multiband transmission device. The present invention relates to a mobile telephone with a multiband transmission device. More particularly, the invention relates to a multiband mobile telephone which comprises a device for transmitting signals in different frequency bands, and which is equipped in particular with several power amplification chains, some of these chains being able to be used in emission for the transmission of signals according to different cellular radiotelephony standards. In general, the field of the invention is therefore that of mobile telephony. It can be implemented in all mobile telephones capable of transmitting signals according to specific cellular radio telephone standards.

 The field of cellular radiotelephony has evolved considerably and rapidly. In this field, telecommunications standards determine a set of technical principles to be observed. Among these standards are the GSM standard, the DCS-PCS standards, the UMTS standard and the EDGE standard. These standards are different insofar as they use in particular different signal modulations, different transmission frequencies or even different information coding means.

Some of these telecommunications standards have coexisted or coexist during the same period. This is the case, for example, of the GSM and DCS-PCS standards, which operate respectively at frequencies close to 900 MHz (megahertz) and 1800/1900 MHz, the DCS-PCS standards being essentially intended for areas with a high concentration of population. Other standards follow, for their part, previously implemented standards. This is for example the case of the UMTS standard, whose transmission frequencies are close to 2100 MHz, which is led to succeed in particular the GSM standard.

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 In the case of a standard coexisting with another standard, as in the case of a standard succeeding another standard, provision must be made for multiband mobile telephones, that is to say capable of operating in frequency bands different and / or according to different information transmission systems. The functioning of the mobile phone is thus ensured in a large part of a territory, and during the periods of transition between two standards.

 As is known, there are as many power amplification chains in a multiband mobile telephone as there are different standards which are capable of being used with this telephone. Each of these power amplification chains is used for the emission of signals which are specific to a standard, and according to an operation which is specific to this chain in order to comply with the standard. FIG. 1 shows the operation of an amplification chain in the case where the telecommunication standard used is the GSM standard. In this figure, a first stage 100, a second stage 101 and a third amplification stage 102 are shown.

The fact of multiplying the amplification stages in an amplification chain makes it possible to obtain the desired gain and sufficient for the emission, while eliminating any noise, oscillation or even current density problems. . The amplification stages are arranged in series with an adaptation circuit 103, itself connected to an antenna 105.

 The amplification stages 100, 101 and 102 in particular have two so-called polarization links, respectively referenced 106 and 107, 108 and 109, and 110 and 11. These polarization links are all connected to a polarization circuit 112.

In the case of GSM, the different amplification stages operate in a saturated mode. Thus, the bias circuit 112 makes it possible to generate the appropriate voltages so that each of the amplification stages 100, 101 and 102 operates in saturated mode.

 Generally, the bias circuit 112 allows

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 to apply fixed bias voltages, which do not change over time, a reception chain being, in the state of the art, intended to process signals which are always transmitted according to the same standard.

 Operation in saturated mode is used in particular to limit the influence of intermodulation lines. Indeed, if we consider a frequency spectrum, lines corresponding to spurious signals of frequency f1, for example generated by a modulator, give rise at the output of an amplifier to image lines corresponding to spurious image signals of frequency f2 . These parasitic lines are centered on the line corresponding to the signal to be transmitted of frequency fO, respecting the relation f2 = 2 * fO-f1. The signals corresponding to the parasitic lines have an attenuated power thanks to the use of the amplifier in a saturated mode. They are thus made less annoying when transmitting signals. The use of a saturated mode in transmission for the GSM standard is authorized due to the modulation used in this standard.

 The adaptation circuit 103 comprises electronic components, for example of the capacity type 104, which make it possible to produce a filter centered on the transmission frequencies of the signals in the standard considered. The choice of component values makes it possible to determine and refine the frequency band which will be used for transmission.

 In the multiband mobile telephone, a power amplification chain such as that described in FIG. 1 is necessary for each standard capable of being used with the mobile telephone. For example, in the GSM / DCS-PCS mobile phone, there are two distinct power amplification chains, each of the amplifiers operating in saturated mode, and the adaptation circuit of each of these chains being different to obtain optimal power. and an optimal yield for the standard considered. To obtain a triband GSM, DCS-PCS and UMTS telephone, it appears necessary to have several amplification chains of

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 power in the transmitting device. However, the creation of a third power amplification chain within a mobile phone is restrictive and costly. It contradicts the efforts made by manufacturers to always reduce the size and manufacturing costs of phones.

 The mobile phone according to the invention overcomes this problem. In fact, in the mobile telephone according to the invention, a power amplification chain already present in a mobile telephone is used, this chain being adapted to a first telecommunications standard in order to transmit first signals, to transmit second signals according to a second telecommunications standard.

 Preferably, in the invention, the first signals are modulated according to a phase modulation and not an amplitude modulation. Thus, the different amplification stages of the amplification chain can operate in saturated mode. In the invention, the second signals can be modulated according to a modulation involving the amplitude of the signals. They then require an operation of the amplification stages in a linear mode; this is for example the case of UMTS signals which use an HQPSK type modulation, which is a phase modulation however inducing an amplitude modulation. The mobile phone according to the invention makes it possible to adapt to this type of situation. To this end, it is proposed to carry out a switching of the different power stages to pass from a saturated operating mode to a linear operating mode and vice versa. The adaptation circuit specific to the amplification chain in question also undergoes an adaptation in order to be able to be centered on the frequency band appropriate to each of the operating modes.

 The invention therefore relates to a multiband mobile telephone comprising a device for transmitting signals in different frequency bands, said device comprising in particular a first power amplification chain provided with stages

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 amplification arranged in series characterized in that it comprises means for switching between a mode of operation in saturated mode and a mode of operation in linear mode of each of the amplification stages.

 In a preferred embodiment of the invention, the operating mode in saturated mode and the operating mode in linear mode are, in the first power amplification chain, respectively dedicated to a first telecommunications standard using a first band transmission frequency and a second telecommunication standard using a second transmission frequency band. Preferably, a variable impedance matching circuit is used in the first power amplification chain. In a particular embodiment of the invention, the adaptation circuit has a switching circuit for switching between a first impedance value corresponding to optimal operation in the first telecommunications standard, and a second value of impedance corresponding to optimal operation in the second telecommunications standard. The invention can today be implemented in particular when the first telecommunications standard is one of the DCS-PCS standards, and the second telecommunications standard is the UMTS standard. In another embodiment of the invention, the second telecommunication standard is the EDGE standard, the first transmission frequency band and the second transmission frequency band in this case being combined.

 In an improvement of the invention, the signal transmission device comprises a second power amplification chain provided with amplification stages arranged in series with means for switching between a mode of operation in saturated mode and a mode of operation in linear mode of each of the amplification stages. In this case, the operating mode in

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 saturated mode and the operating mode in linear mode are, in the second power amplification chain, respectively dedicated to a third telecommunication standard using a third transmission frequency band and to a fourth telecommunication standard using the third band transmission frequency. In this case, the present invention can be used with the GSM standard as the third telecommunication standard, and the EDGE standard as the fourth telecommunication standard.

- à la figure 2, un dispositif d'émission dans un téléphone mobile multibande selon l'invention. The invention and its various applications will be better understood on reading the description which follows and on examining the figures which it accompanies. These are presented for information only and in no way limit the invention. The figures show: - in FIG. 1, already described, a representation of a conventional amplification chain in the example of the GSM;

- In Figure 2, a transmission device in a multiband mobile phone according to the invention.

 FIG. 2 shows a transmission device comprising a first amplification chain 200 and a second amplification chain 300. Each of these chains comprises a first amplification stage, 301 and 201 respectively, a second amplification stage, respectively 302 and 202 and a third amplification stage, respectively 303 and 203. Each of the amplification stages 201,202, 203,301, 302 and 303 has two polarization links referenced respectively 206 and 207,208 and 209,210 and 211,306 and 307, 308 and 309 , and 310 and 311. All the polarization links are connected to a polarization circuit 402.

In other embodiments of the invention, a specific bias circuit could be associated with each of the power amplification chains.

 In the first and second amplification chains, the amplification stages are arranged in series with respectively a first and a second adaptation circuit,

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 referenced respectively 304 and 204, themselves connected to an antenna 212. The adaptation circuits include in particular components of the capacity type, referenced respectively 305 and 205, and arranged so that they constitute a filter in pi. A diode 312 is arranged in the first adaptation circuit 304 between one of the capacitors and the link coming from the third amplification stage.

 A control circuit 403 makes it possible to control the supply of the diode 312. This so-called switching or control circuit 403 is connected to a communication bus 404, which is also connected to a microprocessor 400 and a switching circuit 401. The communication bus 404 allows the microprocessor to transmit commands to the various elements to which it is connected. These various elements are, in the example described, electronic circuits, but they could be replaced by applications contained in a program memory whose operation would be governed by the microprocessor 400.

 The communication circuit 401 is capable of transmitting control instructions to the bias circuit 402 via a link 405. Thus, it can control the passage of the amplification stages of each of the amplification chains 200 and / or 300 from one first polarization mode to a second polarization mode. For example, if the first amplification chain 300 transmits signals according to the DCS-PCS standard, the different amplification stages operate in saturated mode.

 To be able to transmit signals according to the UMTS standard, in a first phase, the switching circuit 201 will have to control the bias circuit so that it applies the appropriate voltages to the various amplification stages 301, 302 and 303 so that these operate in linear mode, a mandatory condition to respect the proper transmission of signals according to the UMTS standard; in a second phase, the control circuit 403 will control the adaptation circuit 304

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 so that it shifts the bandwidth of the circuit, thus passing from a bandwidth centered on 1750 MHz in the case of DCS-PCS, to a bandwidth centered on 1950 MHz in the case of UMTS, and this of so that the impedance matching is optimal over a relatively narrow frequency band. To this end, the control circuit 403 supplies or not the diode 312. In the case where it is supplied, it behaves in short circuit, the impedance of the capacitor 305 to which it is connected then intervening; in the case where it is not supplied, it behaves as a circuit breaker, the impedance of the capacitance 305 to which it is connected then not being taken into account. For this reason, the adaptation circuit 304 is said to have variable impedance.

 The invention is advantageously implemented in the case where the DCS-PCS and UMTS standards are used for transmitting signals by means of a single transmission chain. Indeed, the frequency bands used in transmission by these two standards are close.

 The presence of the second power amplification chain 200 illustrates the fact that the invention can be implemented directly in dual-band GSM / DCS-PCS mobile phones. Furthermore, the invention can also be implemented with other telecommunication standards such as the EDGE standard. This standard has the particularity of authorizing the transmission of signals in two distinct frequency bands, a first being located around 900 MHz, like the GSM standard, and a second being located around 1800 MHz, like the DCS-PCS standard. . Due to the modulation used for the EDGE standard, the different amplification stages must operate in linear mode.

 In the example described, the first amplification chain 300 can therefore operate with signals transmitted in accordance with the DCS-PCS, EDGE 1800 or UMTS standards, if necessary carrying out the necessary polarization switching operations and for adaptations of impedance required. The

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 second amplification chain 200 can for its part operate with signals transmitted according to GSM or EDGE 900 standards, after having carried out the necessary polarization switching operation; no impedance matching operation is necessary here, the transmission frequency bands being used for these two standards being substantially the same.

 The microprocessor 400 controls the switching circuit following a command from the user who has expressed the wish to transmit at a particular frequency, or according to the standard which was used to transmit the last signals which have been received by the mobile phone.

Claims (9)

 CLAIMS 1-Multiband mobile telephone comprising a device for transmitting signals in different frequency bands, said device comprising in particular a first power amplification chain (300) provided with amplification stages (301; 302; 303) arranged in series, characterized in that it comprises means (401; 402) for switching between a mode of operation in saturated mode and a mode of operation in linear mode of each of the amplification stages (301; 302; 303) .  2-multiband mobile phone according to the preceding claim characterized in that, in the first power amplification chain (300), the operating mode in saturated mode and the operating mode in linear mode are respectively dedicated to a first standard of telecommunication using a first transmit frequency band and a second telecommunication standard using a second transmit frequency band.  3-multiband mobile phone according to one of the preceding claims characterized in that it comprises a variable impedance matching circuit (304).  4-multiband mobile phone according to the preceding claim characterized in that the adaptation circuit (304) has a switching circuit (403) for switching between a first impedance value corresponding to optimal operation in the first standard of telecommunication, and a second impedance value corresponding to optimal operation in the second telecommunication standard.  5-multiband mobile phone according to one of claims 2 to 4 characterized in that the first telecommunications standard is one of the DCS / PCS standards and the second telecommunications standard is the UMTS standard. <Desc / Clms Page number 11>  6-multiband mobile phone according to one of claims 2 to 4 characterized in that the first telecommunications standard is one of the DCS / PCS standards and the second telecommunications standard is the EDGE standard, the first frequency band of emission and the second emission frequency band then being combined.  7-multiband mobile telephone according to one of the preceding claims characterized in that the signal transmission device comprises a second power amplification chain (200) provided with amplification stages (201; 202; 203) arranged in series with means (401; 402) for switching between an operating mode in saturated mode and an operating mode in linear mode of each of the amplification stages (201; 202; 203).  8-multiband mobile phone according to the preceding claim characterized in that, in the second power amplification chain (200), the operating mode in saturated mode and the operating mode in linear mode are respectively dedicated to a third standard of telecommunication using a third transmit frequency band and a fourth telecommunication standard using the third transmit frequency band.  9-multiband mobile phone according to the preceding claim characterized in that the third telecommunication standard is the GSM standard, and the fourth telecommunication standard is the EDGE standard.