FR2791213A1 - DEVICE AND METHOD FOR TRANSMITTING IN A MOBILE PHONE - Google Patents

Abstract

To produce a mobile telephone (1) of which elements of a transmission loop, such as filters, are designed at lower cost and therefore generate parasitic signals, then a table (22) comprising values is stored in the mobile telephone. relating to frequencies and for which the parasitic signals generated are of frequencies higher than a cutoff frequency associated with the transmission loop. For a frequency value of a signal to be transmitted, a pair of values can be read from the table (22) making it possible to adjust the frequencies of signals produced by oscillation circuits (4, 5) of the transmission loop.

Description

Device and method for transmitting in a mobile telephone

  The subject of the invention is a transmission device in a mobile telephone. It also relates to a method of transmitting a mobile phone. It applies, in the field of mobile telephony, more particularly to mobile phones operating according to GSM, DCS or PCS. More generally, it finds its application in transmission systems with frequency hopping. The object of the invention is to provide a mobile telephone whose transmission device does not produce parasitic signals in a frequency band in which the telephone

  mobile device, at a lower cost.

  Mobile phones currently produced include a transmitting device. This transmission device comprises in particular a transmission loop. An emission loop has the function of producing a transmission signal and of realizing a frequency servocontrol of this transmission signal. Generally, a transmission loop in a mobile phone has a first, a second and a third oscillation circuit. It further comprises a mixer and a phase comparator. Signals from the three oscillation circuits are combined with each other, via the mixer and the phase comparator, to produce a transmission signal at a desired frequency. This emission loop realizes

  thus a servocontrol of a frequency of the signal to be transmitted.

  The mixer has two inputs connected to the first oscillation circuit and the third oscillation circuit. The phase comparator receives on a first input a signal from the mixer and on a second input a signal from the second oscillation circuit. An output signal of this phase comparator is sent to the third oscillation circuit of which an output signal corresponds to a signal to be transmitted. Such an emission loop also makes it possible to produce a signal capable of

frequency agility.

  Currently, to produce a signal with frequency agility in a frequency band, for example that according to the GSM standard, a frequency of the first oscillation circuit is varied by frequency hopping multiples of 200 kHz. A signal frequency from the second

  Oscillation circuit is a fixed frequency in this frequency band.

  Thus, this frequency jump is found at the output of the third circuit

  oscillation, the one producing the signal to be emitted.

  Such an embodiment presents problems. Indeed, frequency values that a signal to be transmitted can have are known. When a frequency value of the signal to be transmitted must change, the frequency of the first oscillation circuit is varied accordingly by a value equal to the value of the frequency hopping to be performed. The different devices of the emission loop are non-linear, the most nonlinear being the mixer. These non-linearities produce parasitic signals at harmonic frequencies which will combine with each other in the transmission loop and produce a resulting signal which will disturb the signal to be transmitted. This

  disturbance degrades a requested quality of the signal to be transmitted.

  These combinations are additive or subtractive. In order to reduce the influence of these parasitic signals produced in the transmission loop, filtering means are mainly used. These have the disadvantage of increasing the cost price of the mobile phone, to increase congestion due to surplus equipment. Moreover, these means do not always guarantee a requested quality of the frequency characteristics of the signal to be transmitted when there is a

  cost constraint of realization of the mobile phone.

  The present invention proposes to remedy these problems by proposing a mobile telephone in which a frequency value of the second oscillation circuit is also variable, even for frequency hopping in a given frequency band, GSM for example. In the invention, a frequency value of the first oscillation circuit depends on a requested frequency value of the third oscillation circuit and

  a frequency value of the second oscillation circuit.

  In addition, an emission loop can be modeled by a second order low pass filter with a cutoff frequency. In the invention, as a function of a requested frequency value for the signal to be transmitted, a frequency value of the first oscillation circuit and a frequency value of the second oscillation circuit are selected so that parasitic harmonic signals are obtained. additional products by the mixer have a frequency value greater than the value of the previous cutoff frequency. Spurious signals at a frequency higher than this cutoff frequency of this low-pass filter are attenuated. More generally, the more parasitic signal frequencies are greater than this cutoff frequency value and the more effective the solution of the invention is. This ensures an attenuation of parasitic signals with respect to the signal to be transmitted. Filtering means are consequently simpler or even deleted, and or less expensive and therefore less bulky. In the invention, at each frequency hopping, a table is read in a memory of the mobile telephone in which, for a frequency value of the signal to be transmitted, parameters relating to a selected frequency value of the first oscillation circuit are found. and at a selected frequency value of the second oscillation circuit. We set the first and the second

  oscillation circuit according to a value of the parameters read.

  The present invention thus relates to a mobile telephone comprising a transmission device provided with oscillation circuits combined, among these oscillation circuits a first oscillation circuit produces a signal at a transition frequency FRF and a second oscillation circuit produces a signal at an intermediate IF frequency, the transition frequency and the intermediate frequency being different from an FTX frequency of a transmission signal characterized in that it comprises a table having two coefficients U and V to read for a frequency value of the transmission signal, each coefficient being transformed into a signal applied to an input of

  control of an oscillation circuit.

  It also relates to a transmission method in a mobile telephone comprising a modulator, a first, a second and a third oscillation circuit, the first oscillation circuit producing a signal at a transition frequency FRF and comprising a first divider of frequency by U, the second oscillation circuit producing a signal at an intermediate frequency Fi and having a second frequency divider by V, and the third oscillation circuit producing a signal at an emission frequency FTX characterized in that - storing a table of pairs of values of two coefficients U and V, representing division values of the first and second frequency divider respectively in a memory of the mobile telephone, - determining an FTX frequency for the third oscillation circuit and a pair of values of the two coefficients U and V corresponding to this frequency FTX are read from the table; first frequency divider and the second frequency divider with the values of the coefficients U and V read in the table respectively.

  The invention will be better understood on reading the description which follows

  and examining the figures that accompany it. These are presented only as an indication and in no way limitative of the invention. The figures show: FIG. 1: a mobile telephone with a transmission device according to the invention; Figure 2 a representation in the form of an algorithm of a

  operation of the emission process of the invention.

  Figure 1 shows a mobile phone 1 according to the invention. This mobile telephone 1 comprises a reception device 2 and a transmission device 3. The invention applies more particularly to the transmission device 3. However, the invention could equally well apply to the receiving device 2. The transmission device 3 comprises an oscillation circuit 4, an oscillation circuit 5 and an oscillation circuit 6. The oscillation circuit 6 is most often a voltage-controlled oscillator that will be called oscillator 6 thereafter. These circuits 4 and 5 and this oscillator 6 are combined, in particular by means of a mixer 7 and a generator. 8 comparator

  phases, to form an emission loop.

  The mixer 7 has two inputs 9 and 10. The input 9 is connected to

  an output of the circuit 4 and the input 10 is connected to an output of the oscillator 6.

  The comparator 8 has two inputs 11 and 12. The input 11 is connected to

  an output of the comparator 7 and the input 12 is connected to an output of the circuit 5.

  Oscillator 6 has an input 13 connected to an output of comparator 8.

  The transmission loop thus produced produces a signal to be transmitted on an output 14 of the oscillator 6. Most often a connection between the output 14 of

  The oscillator 6 and the inlet 10 of the mixer 7 is produced by a sensor 15.

  This sensor 15 takes an image signal of the signal to be transmitted and transmits it to the input 10 of the mixer 7. The signal to be output is output 14 is sent to a power amplifier 16 whose output is connected to a

  antenna 161 of the mobile phone 1.

  The mobile telephone 1 further comprises a microprocessor 17, a program 18 in a program memory 19, a data memory 20 and a bus 21 of commands, data and addresses. The mobile phone 1 further comprises a table 22 in the data memory 20 with rows and columns. The table 22 comprises a first column 23 with fields in which the frequency values Fi of the signal to be transmitted are placed. The table 22 further comprises a second column 24 and a third column 25 relating to pairs of values of the coefficients U and V to read respectively. A value of a coefficient is transformed into a signal applied by the bus 21 to the circuit 4 or the circuit 5 respectively. A line of this table 22 thus comprises, in respective fields, all the parameters, in particular a pair of values, related to a frequency of the signal to be transmitted, a value of which is

  in a field in column 23 of that same line.

  The program 18 controls the microprocessor 17 so that it calculates, in a first step, a new frequency value for the signal to be transmitted. In a second step, the microprocessor 17 reads from the table 22 a pair of values of the coefficients U and V of a line identified.

  by a value Fi of the frequency of the signal to be transmitted.

  In a preferred example, the oscillation circuit 4 is a phase-locked loop comprising a reference oscillator 26, for example a quartz crystal, a phase comparator 27, a loop low-pass filter 28, a voltage-controlled oscillator 29 and a frequency divider 30 by a coefficient U. Similarly, the oscillation circuit 5 comprises a quartz reference oscillator 31, a phase comparator 32, a loop low pass filter 33, a voltage controlled oscillator 34 and a frequency divider 35 by a coefficient V. An output of the oscillator 29 is connected to the input 9 of the mixer 7. An output of the oscillator 34 is connected

at the input 12 of the comparator 8.

  The mobile telephone 1, in a GSM frequency band, for example, is capable of frequency agility. In this example, the frequency agility of the signal to be transmitted is achieved by frequency hopping, a value of which is a multiple of 200 kHz. In one example the oscillator 26 produces a signal at a frequency of 200 kHz. Table 22 has as many lines as frequency values used in the frequency band under consideration, such as GSM. In a general case, two successive fields in column 23 in table 22 comprise two successive values, a difference of which is equal to 200 kHz, of the frequency of the

signal to be transmitted.

  Thus, at a frequency value F of the signal to be transmitted corresponds, in the same line, a coefficient U of value A and a coefficient V of value B. More generally, at a frequency Fi corresponds to a coefficient U equal to A + i and at a coefficient V equal to B. The oscillator 26 produces, in a preferred example, a signal at a frequency of 200 kHz. A value of the coefficient U makes it possible to know a frequency value at the output of the circuit 4. In fact, with a phase-locked loop, a frequency value of the output signal is equal to the frequency value of the reference oscillator 26 multiplied by the value of the coefficient U. This value is taken from the table 22 by the microprocessor 17. So to change a value of the frequency of the output signal of the oscillator 29 in steps of 200 kHz it is sufficient to increase a value of the coefficient U of one unit each time. In table 22 when passing from a line associated with a frequency of value Fi to a frequency of value Fi +, then a value of the coefficient U passes from a value A + i to a value A + i + 1. On the other hand, the coefficient V is always equal to the value B. For a value of frequency equal to Fi + k the coefficient U is equal to A + i + k and the coefficient V is equal to B. In the invention, when a frequency of the signal to be transmitted goes from a value Fi.k to a value Fi + k + 1, then the value of the coefficient U goes from the value A + i + k to a value A + j, with j X i + k + 1 and the coefficient V goes to a value C E B. In a variant, the values of frequencies are stored in the table 22 rather than values of the coefficients U and V. To obtain a value of the coefficients U or V, a value is divided a frequency read by a frequency value of the oscillator 26 or 31 respectively. This makes it possible to use a universal table 22 that is independent of a frequency value of the oscillators 26 and 31. However, in the invention, pairs of values of the coefficients are memorized in the table 22. U and V. The invention also relates to a transmission method in the mobile telephone 1. The oscillation circuit 4 produces a signal at a frequency FRF. The

  oscillation circuit 5 produces a signal at an intermediate frequency Fi.

  The voltage controlled oscillator 6 produces a signal at an emission frequency FTX. In the method of the invention, the table 22 is stored with two coefficients U and V representative of a dividing value of the divider 30 and the divider 35, respectively, in the memory 20 of the mobile telephone 1. The program 18, in FIG. using the microprocessor 17, determines an FTX frequency of the oscillator 6 for the signal to be transmitted. The program uses a law of variation of the FTX frequency values which makes it possible to obtain a pseudo-random temporal distribution of these FTX frequencies. To obtain such a law, the GSM standard is known for example. Once this value has been calculated, we search for the field of the column 23 corresponding to this frequency value FTX and we obtain. In this row, in columns 24 and 25,

  the values of the pair of values of the coefficients U and V respectively are read.

  The divider 30 is set to the value read from the coefficient U and the divider 35 to the value read from the coefficient V. More specifically, the mobile telephone 1 exchanges information 36 with a mobile telephone network 37. In a preferred example, this information 36 is sent respecting the access protocol TDMA (Time Division Multiple Access in English, or Multiple Access Time Distribution in French TDMA). So, two phone shows

  mobile 1 are separated by a fixed duration greater than a transmission duration.

  Thus, divisors 30 and 35 are set with values of coefficients U and V respectively during these fixed times. In the GSM example, a transmission duration is of the order of 577 ps and two transmissions are separated by at least a duration of the order of 4.6 ms. As a result, the microprocessor 17 sets frequency values of the circuits 4 and 5 in less than 4.6 ms, so that the device 3 is ready to transmit at the beginning of

the next issuing phase.

  To memorize the table 22, used by the transmission method of the mobile phone 1, the following steps are carried out. We seek for a frequency FTX retained candidate IF and FRF frequencies. A retained FTX frequency is a frequency selected from all possible FTX frequencies of a given frequency band. The following calculation steps are actually steps to modeling a signal production

  parasites in the transmit loop.

  Indeed, the elements of the transmission loop, in particular the mixer 7, are non-linear elements. The mixer 7 thus produces at the output parasitic signals resulting from combinations between harmonic signals of the signal at the frequency FRF and harmonic signals of the signal at the frequency FTX. These parasitic signals are also combined with harmonic signals produced from the signal at the frequency F1. This produces parasitic signals whose parasitic frequency is a combination, additive or subtractive, or both, between harmonic signals originating from the three IF signals. , FRF and FTX. The transmission loop can be modeled by a low pass filter of cut-off frequency Fc. This filter thus attenuates spurious signals whose frequency is greater than the frequency Fc. It attenuates them all the more as a parasitic frequency is greater than the frequency Fc, and more generally greater than one

frequency X x Fc.

  This operation can be modeled by calculating the harmonic frequencies nFI, mFRF and kFTX of these candidate frequencies and the

  frequency retained. The parasitic frequency nFl + mFRF + kFTX is calculated.

  For the calculation of this parasitic frequency, it is considered that the values n, m and k are relative integers. A parasitic frequency value is thus obtained by additive and / or subtractive combination of the different harmonic frequencies. The values n, m and k are varied. It is verified that all the values of the parasitic frequency thus calculated are greater than

  the frequency XFc, where X is a positive integer.

  Thus, FRF and FI frequencies are sought, all combinations of harmonic signals producing parasitic signals at frequencies greater than X × Fc. This search is done for

  all FTX frequency values.

  A group of frequencies is formed from a set of frequencies FI, FRF and FTX. This frequency group is a group for which harmonic frequencies generate parasitic frequencies out of

  the bandwidth of the transmit loop.

  Each element of this group of frequencies is then stored in corresponding fields of a row of the table 22 with two coefficients U and V. In fact, values of the coefficients U and V are stored, making it possible to obtain, by multiplication by a reference frequency, the FRF and FI frequencies respectively of the frequency group

  corresponding. A group of frequencies is therefore associated with a line

  same identified by an FTX frequency value. For a new FTX frequency value, the previous steps are repeated to determine a pair of FRF and FI frequencies that satisfy the criterion. We

  thus fulfills the table 22 step by step.

  In a preferred example, k is set equal to 5 and values of n, m and k are limited to 60. Higher values correspond to harmonic frequencies of signals whose amplitudes are sufficiently small so as not to disturb the signal at issue. Fl and FRF frequencies are thus sought, of which a combination of harmonic signals, of maximum rank 60 for m in particular, does not produce parasitic signals at a frequency less than 5 Fc. In a non-limiting example of the invention, the cut-off frequency Fc is of the order of 800 kHz. This value of Fc depends on the characteristics of the elements of the transmission loop. Generally, a low pass filter is placed (no

  shown) between the output of the comparator 8 and the input 13 of the oscillator 6.

  A function of this low-pass filter is the same as that of a loop filter in a phase-locked loop, in particular as regards the filtering of the signals coming from the comparator 8. Thus, it is possible to obtain another value of Fc by modifying for example the characteristics

of this low-pass filter.

  In the description, it was considered that the mobile phone 1 was

  single-band and operated in a frequency band defined according to the GSM standard. In a preferred variant, the mobile phone 1 is of multiband type, that is to say that it can operate, at the request of a user of the mobile phone 1, in several frequency bands defined in particular by standards. In a preferred example, the mobile phone 1 can operate in frequency bands according to the GSM, DCS or PCS standard. It could also operate in frequency bands according to the GSM or DCS standard only or more generally, in bands of

  frequencies in which the invention can be applied.

  In the case of possible operation of the mobile telephone 1 in three frequency bands, GSM, DCS and PCS for example, the device 3 comprises a voltage-controlled oscillator 38, an input 39 of which is connected to the input 13 of the Oscillator 6. The function of the oscillator 38 is to produce signals to be transmitted in the DCS and PCS frequency bands, these two frequency bands being close to one single oscillator. An output 40 of the oscillator 38 is sent into a power amplifier 41 before being sent to the antenna 161. In one example, a diplexer circuit 42 is placed between the outputs of the amplifiers 16 and 41 and the antenna 161. This diplexer 42 serves to filter signals from amplifiers 16 and 41 so that a transmission signal does not have parasitic components outside a frequency band for which it is intended. This diplexer circuit 42 comprises two inputs 43 and 44. The input 43 is connected to the output of the amplifier 16 and the input 44 is connected to the output of the amplifier 41, the output of this diplexer circuit being connected to the antenna 161. In order to be able to switch from the GSM band to the DCS band for example, the transmission device 3 comprises a divider 45 of frequency by N and a divider 46 of frequency by R. The divider 45 is inserted between the output of the mixer 7 and the input 11 of the comparator 8. The divider 46 is inserted between the output of the oscillator 34 and the input 12 of the comparator 8. The two dividers 45 and 46 are also connected to the bus 21. In the invention, values of N and R can be varied in the same frequency band. As a result, for an FTX frequency we have a larger

  choice of candidate Fl and FRF frequencies.

  In a preferred variant, the table 22 further comprises two additional columns 47 and 48 comprising fields relating to values of the coefficients N and R respectively. Thus, the microprocessor 17 sets, for each frequency value FTX, the values of the coefficients U,

V NETR.

  In a preferred example the oscillator 34 varies in a range between 855 MHz and 880 MHz regardless of the band in which the mobile phone operates. This low frequency deviation makes it possible to use only one oscillator 34 for any frequency value of the signal to be transmitted and this whatever the frequency band in which the mobile phone 1 transmits. Oscillator 31 provides in one example a signal at a frequency of 1 MHz. In a preferred example, the candidate Fl frequencies are selected in an interval between 855

  MHz and 880 MHz. A value of V therefore varies between 855 and 880.

  In this preferred example, the values of the frequencies FI and FRF respect the following table:

FTX FRF FI N R

880.2 1393.2 855

880.4 1393.4 855 3 5

894.2 1407.2 855

894.4 1410.4 860

GSM 894.6 1410.6 860 3 5

900.6 1416.6 860

900.8 1425.2 874

901.0 1425.4 874 3 5

914.8 1439.2 874 _

1710.0 2060.4 876

1710.2 2060.6 876 2 5

1736.8 2087.2 876 _

1737.0 2081.4 861

DCS 1737.2 2081.6 861 2 5

1762.8 2107.2 861

1763.0 2111.8 872

1763.2 2112.0 872 2 5

1785.0 2133.8 872

1850.2 2199.4 873

1850.4 2199.6 873 2 5

1862.0 2211.2 873

1862.2 2214.2 880

1862.4 2214.4 880 2 5

1875.0 2227.0 880

1875.2 2226.0 877

1875.4 2226.2 877 2 5

PCS 1884.8 2235.6 877

1885.0 2231.8 867

1885.2 2232.0 867 2 5

1892.6 2239.4 867

1892.8 2241.2 871

1893.0 2241.4 871 2 5

1901.0 2249.4 871

1901.2 2251.2 875

1901.4 2251.4 875 2 5

___ 1910.0 2260.0 875

  The values of the coefficients N and R are fixed in a frequency band. This example is in no way limiting of the invention. This table indicates only preferred frequency values, but other frequency values, for which spurious frequencies generated are higher than the frequency Fc, are possible. In addition, one could very well have chosen FI and FRF frequencies which imply changes of the values of the coefficients N and R. To obtain other values of frequency one seeks frequencies FI and FRF which combinations of

  harmonic frequencies check nFl + mFRF + kFTX> XFc.

  FIG. 2 shows a representation in a form of an algorithm of an operation of the transmission method of the invention. In a first step 49, the method of the invention is in a waiting phase of a request for a frequency hopping. As long as there is no frequency hopping request, the method of the invention remains in this step 49. A request occurs, preferably, on the order of the program 18 during a period during which the mobile phone 1 does not emit. It could just as easily happen during a communication phase and be put on hold until the end of the show. In case of request for a frequency hopping, during a step 50, the program 18 controls the

  microprocessor 17 for calculating a new FTX frequency value.

  For this, the program 18 uses a law of pseudo-random variation, that is to say a deterministic law but whose statistical characteristics are those of a random law, to determine this new value. In fact this step 50, of preparatory calculations, could be carried out during a transmission period. In a step 51, the microprocessor 17 searches the table 22 for the line identified by this frequency value FTX. Columns 24, 25, 47 and 48 of this line read the values of the coefficients U, V, N and R respectively. The microprocessor 17 regulates, in a step 52, the dividers 30, 35, 45 and 46 with the values of the coefficients U, V, N and R read in step 51. The process is found again in

  the waiting step 49 of a frequency hopping request.

  In an alternative embodiment of the device of the invention is placed in the mobile phone 1 a dedicated circuit (not shown). This specialized circuit has the function of implementing, using the program 18, the method of the invention and to adjust the dividers 30, 35, 45 and 46. It is synchronized by the microprocessor 17 which indicates the durations during

  which settings can be made.

Claims (9)

  1 - Mobile telephone (1) comprising a transmission device (3) provided with oscillation circuits (4, 5) combined, among these oscillation circuits a first oscillation circuit (4) produces a signal at a frequency Transition FRF and a second oscillation circuit (5) produces a signal at an intermediate frequency F1, the transition frequency and the intermediate frequency being different from an FTX frequency of an emission signal characterized in that comprises a table (22) having two coefficients U and V to read for a frequency value Fi of the transmission signal, each coefficient being converted into a signal applied to a control input of a oscillation circuit.   2 - Mobile telephone (1) according to claim 1 characterized in that when the frequency of the transmission signal goes from a value Fi to a successive value F, + 1 the two coefficients U and V are of values A + i and B at values A + i + 1 and B respectively, and in that when the frequency of the transmission signal changes from a value Fi + k to a successive value Fi + k + 1 the two coefficients U and V pass values A + i + k and B to   values A + j and C respectively, with j X i + k + 1 and C ó B and k> 0.   3 - transmission method in a mobile telephone (1) comprising a modulator, a first, a second and a third oscillation circuit, the first oscillation circuit (4) producing a signal at a transition frequency FRF and comprising a first frequency divider (30) by U, the second oscillation circuit (5) producing a signal at an intermediate IF frequency and having a second frequency divider (35) by V, and the third circuit (6) of oscillation generating a signal at an emission frequency FTX characterized in that - a table (22) is stored of pairs of values of two coefficients U and V, representative of division values of the first and second divisors (30, 35) respectively in a memory (20) of the mobile telephone (1), - a frequency FTX for the third oscillation circuit (6) is determined and a pair of values of the two coefficients U and in the table (22) are read V corresponding this frequency FTX, - adjusting the first divider (30) and the second frequency divider (35) of frequency with the values of the coefficients U and V read in the table (22) respectively.   4 - Process according to claim 3 characterized in that to store the table (22) is performed the following steps: a) - one retains a frequency FTX, b) - one chooses, for this frequency FTX, frequencies FI and FRF candidates , c) - the harmonic frequencies nFI, m FRF and kFTX of these candidate frequencies are calculated, d) - a resulting frequency nFI + m FRF + k FTX is calculated with n, m and k which are relative integers, e) - it is verified that whatever the values of n, m and k the resultant frequency is greater than XFc where X is an integer greater than zero and Fc is a cutoff frequency of a low-pass filter constituted by the three circuits (4-6) with the second oscillation circuit (5) as input and the third oscillation circuit (6) at the output, f) - a frequency group is formed from a set of frequencies FI, FRF and FTX frequency candidates that satisfy the verification, g) - in the table (22), comprising rows and columns (24, 25), a pair of values of the representative coefficients U and V, by multiplication by a transition reference frequency or by an intermediate reference frequency, of the FRF frequencies and satisfactory candidate FI, respectively, a pair of frequencies being identified by a frequency FTX associated with one line of the table, h) - steps a) to g) are repeated for a new frequency FTX of the output signal at the transmission frequency , a new FTX frequency being obtained from an old FTX frequency jumped frequency. 5 - Process according to claim 4 characterized in that   - values of n, m and k less than 60 are chosen.   6 - Method according to one of claims 4 or 5 characterized in that than   - is set at a value greater than or equal to 2, preferably 5.   7 - Method according to one of claims 4 to 6 characterized in that   FTX is varied in a transmission frequency band defined by the GSM, DCS or PCS standard depending on the use, and jumps are made in   frequency of a multiple value of 200 KHz.   8 - Process according to one of claims 4 to 7 characterized in that   the candidate intermediate frequencies Fl are selected in a   range between 855MHz and 880MHz.   9 - Process according to one of claims 3 to 8 characterized in that   the values of frequencies FI and FRF respect the table hereafter: FTX FRF FI N R 880.2 1393.2 855 880.4 1393.4 855 3 5 894.2 1407.2 855 894.4 1410.4 860 GSM 894.6 1410.6 860 3 5 900.6 1416.6 860 900.8 1425.2 874 901.0 1425.4 874 3 5 914.8 1439.2 874 1710.0 2060.4 876 1710.2 2060.6 876 2 5 1736.8 2087.2 876 _ 1737.0 2081.4 861 DCS 1737.2 2081.6 861 2 5 1762.8 2107.2 861 1763.0 2111.8 872 1763.2 2112.0 872 2 5 1785.0 2133.8 872 1850.2 2199.4 873 1850.4 2199.6 873 2 5 1862.0 2211.2 873 1862.2 2214.2 880 1862.4 2214.4 880 2 5 1875.0 2227.0 880 1875.2 2226.0 877 1875.4 2226.2 877 2 5 PCS 1884.8 2235.6 877 1885.0 2231.8 867 1885.2 2232.0 867 2 5 1892.6 2239.4 867 1892.8 2241.2 871 1893.0 2241.4 871 2 5 1901.0 2249.4 871 1901.2 2251.2 875 1901.4 2251.4 875 2 5 1910.0 2260.0 875