System for generating a frequency-stabilized periodic signal.

Abstract

System for generating a frequency-stabilized periodic signal The invention relates to a system (110) for generating a frequency-stabilized periodic signal comprising: - a programmable device (120) for generating the periodic signal; - a device (140) for measuring a temperature of the device for generating the periodic signal; and - a device (130) for measuring the frequency of the periodic signal. Such a system further comprises a calculation device (160) configured to execute, the frequency of the periodic signal having been previously programmed via programming information: - a determination of a temperature drift of the device for generating the periodic signal relative to a reference temperature; and, if the temperature drift is greater than a predetermined threshold: - a calibration of the frequency of the periodic signal. ABSTRACT FIGURE: [Fig.1]

Description

Title of the invention: System for generating a frequency-stabilized periodic signal. Field of invention

[0001] The field of the invention is that of the generation of periodic signals.

[0002] The invention relates more particularly to a system for generating such a frequency-stabilized periodic signal.

[0003] Such a periodic signal is used eg for the generation of synchronous clocks or for frequency transposition. The invention thus has applications in particular, but not exclusively, in numerous fields related to data transmission, eg by radiofrequency, acoustic or optical link. The invention thus has applications eg in the field of mobile telephony (eg 4G, 5G networks or beyond as defined by the 3GPP (for "3rd Generation Partnership Project" in English)) or WLAN (for "Wireless Local Area Network" in English, eg using WiFi), high-speed wireless internet access (WiMAX), asymmetric digital links (xDSL), etc. Prior art and its drawbacks

[0004] Most electronic systems on a chip have several frequency references that can serve as a time base for alarm functions (RTC function for "Real Time Clock" in English), for serial or parallel data transmissions (e.g. via a USB connection (for "Universal Serial Bus" in English), UART (for "Universal Asynchronous Receiver Transmitter" in English), etc.) or for radiofrequency (RF) transceivers. The performance criteria of the reference oscillators are:

[0005] - The accuracy of the generated frequency;

[0006] - Consumption; and

[0007] - The drift of the generated frequency due to variations in the environment (eg supply voltage, temperature, etc.) and the aging of the components implemented in the oscillator diagram.

[0008] Usually, frequency references are made around quartz oscillators. The use of quartz resonators makes it possible to obtain good precision on the generated frequency (a few tens of parts per million (ppm)), a very low temperature drift (eg a few ppm per degree Celsius). As these resonators have high quality coefficients (a few thousand), these oscillators are very stable (low jitter and low phase noise) and have moderate consumption. In addition, the aging of these components is limited.

[0009] However, quartz crystals are not integrable and are bulky when compared to highly integrated electronics. On the other hand, their cost is not negligible. There is therefore an interest in limiting or reducing the number of quartz oscillators in electronic systems and particularly in embedded electronics.

[0010] The performance of RF transmitters and receivers depends heavily on the performance of their reference oscillator. It is therefore not realistic to consider replacing quartz oscillators for these applications. Conversely, it may be possible to consider replacing the low-frequency reference oscillators (e.g. at 32.768 kHz) used as the time base for the RTC function with fully integrated oscillators. The RTC function allows e.g. to ensure the wake-up of an RF transmitter or receiver (e.g. in a sensor node) at a precise time. The circuit implementing the RTC function is the only circuit of the RF transmitter or receiver that operates when it is in sleep mode. The consumption of such an RTC circuit must therefore be minimized. However, even if the constraint on jitter is relaxed in an RTC-type application, the accuracy and temperature drift must remain under control.

[0011] There is thus a need for a system for generating a frequency-stabilized periodic signal which has controlled energy consumption. Presentation of the invention

[0012] In one embodiment of the invention, a system is provided for generating a frequency-stabilized periodic signal around a predetermined target frequency. Such a system comprises:

[0013] - a device for generating the periodic signal, a frequency of the periodic signal generated being programmable over a predetermined frequency range;

[0014] - a device for measuring a temperature representative of a temperature of the periodic signal generating device; and

[0015] - a device for measuring a frequency representative of a signal frequency periodic by implementing a periodic reference signal.

[0016] Such a system further comprises a calculation device configured to execute, the frequency of the periodic signal having been previously programmed via programming information:

[0017] - a determination of a temperature drift of the signal generating device periodic with respect to a reference temperature associated with the programming information, the determination implementing the temperature measuring device; and, if the temperature drift is greater than a predetermined threshold:

[0018] - a calibration of the frequency of the periodic signal by implementing the frequency measuring device and the target frequency.

[0019] Thus, the invention proposes a new and inventive solution for generating a frequency-stabilized periodic signal which has controlled energy consumption.

[0020] More particularly, it is proposed to condition the calibration of the frequency of the generated periodic signal on a measurement of the temperature drift of the device for generating the periodic signal (e.g. an oscillator integrated on silicon). Indeed, the temperature of the electronic components used for the implementation of an oscillator being one of the main sources of drift of the oscillation frequency, the conditioning of the calibration on a temperature variation greater than a predetermined threshold makes it possible to carry out the calibration only when really necessary. This makes it possible to minimize the number of calibrations implemented and therefore the consumption of the system in the end.

[0021] In some embodiments, if the temperature drift is less than the predetermined threshold, the computing device is configured to re-execute the determination of a temperature drift of the periodic signal generating device delivering an updated temperature drift. If the updated temperature drift is greater than the predetermined threshold, the computing device is configured to re-execute the calibration of the frequency of the periodic signal.

[0022] In some embodiments, determining the temperature drift of the periodic signal generating device comprises:

[0023] - a generation of an activation signal of the temperature measuring device;

[0024] - a reception of temperature information from the generating device of the periodic signal, the temperature information being sent by the temperature measuring device in response to activation of the temperature measuring device; and

[0025] - a calculation of the temperature drift of the signal generation device pe periodic depending on the temperature information and the reference temperature.

[0026] In some embodiments, the calibration comprises:

[0027] - a generation of an activation signal of the frequency measuring device;

[0028] - a reception of frequency information representative of the frequency of the periodic signal, the frequency information being sent by the frequency measuring device in response to activation of the frequency measuring device;

[0029] - a generation of updated programming information based on the frequency information and the target frequency for the periodic signal; and

[0030] - a programming of the frequency of the periodic signal with the pro information updated programming.

[0031] In some embodiments, when the computing device executes a new iteration of the periodic signal frequency calibration, the reference temperature is updated based on the temperature information, the updated reference temperature being associated with the updated programming information.

[0032] Thus, the system is configured to be able to re-execute the determination of a temperature drift of the periodic signal generation device relative to the updated reference temperature.

[0033] In certain embodiments, the device for generating the periodic signal comprises:

[0034] - an oscillator configured to generate a first signal; and

[0035] - a programmable frequency division device configured to divide the frequency of the first signal delivering the periodic signal.

[0036] The programming information comprises at least one division rank for programming the frequency division device.

[0037] In some embodiments, the device for measuring the frequency representative of the frequency of the periodic signal comprises a reciprocal counter supplied, on the one hand, by the periodic signal and, on the other hand, by the reference signal. The reciprocal counter delivers a binary word representative of the frequency of the periodic signal, the frequency information comprising the binary word representative of the frequency of the periodic signal. The frequency division device comprises a programmable integer frequency divider via a binary word encoding the division rank of the integer frequency divider. A format of the binary word encoding the division rank is identical to a format of the binary word representative of the frequency of the periodic signal.

[0038] Thus, the binary word representing the frequency of the periodic signal is applied directly to the integer frequency divider, thereby making the implementation simple and efficient.

[0039] In some embodiments, the programmable frequency division device includes a fractional frequency divider configured to divide the frequency of the first signal providing a second signal. The programmable integer frequency divider is configured to divide the frequency of the second signal providing the periodic signal.

[0040] Thus, the frequency of the first signal does not need to be expressed as a power of 2 of the frequency of the final periodic signal. The frequency of the first signal can be chosen more flexibly.

[0041] In some embodiments, the device for generating the periodic signal comprises an oscillator configured to generate the periodic signal. The programming information comprises a control of at least one parameter of the oscillator on which the frequency of the periodic signal depends, the parameter belonging to the group including:

[0042] - a supply current value;

[0043] - a capacity value; and

[0044] - a resistance value.

[0045] The invention also relates to an integrated circuit comprising a system for generating a periodic signal as described previously (according to any one of the aforementioned embodiments).

[0046] The invention also relates to a system comprising:

[0047] - a system for generating a periodic signal as described previously (according to any of the aforementioned embodiments); and

[0048] - a frequency reference delivering the periodic reference signal.

[0049] The frequency reference is e.g. a quartz oscillator (e.g. at 52 MHz). List of figures

[0050] Other aims, characteristics and advantages of the invention will appear more clearly on reading the following description, given as a simple illustrative, and non-limiting, example, in relation to the figures, among which:

[0051] [Fig-1] illustrates a system for generating a frequency-stabilized periodic signal implementing a reference signal according to an embodiment of the invention;

[0052] [Fig. 1a] illustrates a periodic signal generation device implemented in the generation system of [Fig. 1] according to an embodiment of the invention;

[0053] [Fig.2] represents an example of the structure of the computing device of the system of ge generation of [Fig.l] allowing the implementation of the steps of the method for generating a frequency-stabilized periodic signal of [Fig.3] according to an embodiment of the invention;

[0054] [Fig.3] represents the steps of a method for generating the periodic signal frequency stabilized according to one embodiment of the invention;

[0055] [Fig.3a] represents the steps implemented in the step of determining the temperature drift of the method for generating the frequency-stabilized periodic signal of [Fig.3] according to an embodiment of the invention; and

[0056] [Fig.3b] represents the steps implemented in the calibration step of the frequency of the periodic signal of the method for generating the frequency-stabilized periodic signal of [Fig.3] according to an embodiment of the invention.

[0057] Detailed description of embodiments of the invention

[0058] The general principle of the invention is based on a system for generating a frequency-stabilized periodic signal in which the calibration of the frequency of the periodic signal is conditioned by a measurement of the temperature drift of the device for generating the periodic signal as such (e.g. an integrated silicon oscillator). Indeed, the temperature of the electronic components used for the implementation of an oscillator being one of the main sources of drift of the oscillation frequency, conditioning the calibration to a temperature variation greater than a predetermined threshold allows the calibration to be carried out only when really necessary. This makes it possible to minimize the number of calibrations implemented and therefore the consumption of the system in the end.

[0059] We now present, in relation to [Fig.l] a system 100 comprising a system 110 for generating a frequency-stabilized periodic Spsf signal implementing a periodic reference signal Sref according to an embodiment of the invention.

[0060] More particularly, the periodic reference signal Sref is generated by a frequency reference 150. For example, the frequency reference 150 is a quartz oscillator delivering a reference signal Sref, eg at a frequency of 52 MHz.

[0061] Returning to [Fig.l], the system 110 for generating the periodic Spsf signal comprises:

[0062] - a device 120 for generating the periodic Spsf signal, a frequency of the signal S generated periodic psf being programmable over a predetermined frequency range, eg via programming information;

[0063] - a device 140 for measuring a temperature representative of the temperature of the device for generating the periodic Spsf signal;

[0064] - a device 130 for measuring a frequency representative of the frequency of the periodic Spsf signal by implementing the reference Sref signal; and

[0065] - a computing device 160 comprising means for implementing the method of generating the frequency-stabilized periodic Spsf signal described below in relation to [Fig.3].

[0066] In practice, such a system 110 can be integrated into an integrated circuit using a technology known per se (BiCMOS, CMOS, etc.).

[0067] Furthermore, any type of temperature measuring device 140 may be implemented according to the present technique. For example, a device 140 implementing a relaxation oscillator, a PTAT current source and a reciprocal counter may be implemented in the device 140.

[0068] In certain embodiments, the device 120 for generating the periodic Spsf signal comprises ([Fig.1a]):

[0069] - an oscillator 121 configured to generate a first signal; and

[0070] - a programmable frequency division device 122 configured to divide the frequency of the first signal delivering the periodic Spsf signal. For example, when the frequency of the generated periodic Spsf signal is programmable via programming information, the programming information in question comprises a (or several) division rank for programming the frequency division device 122.

[0071] For example, oscillator 121 is a first-order temperature-compensated oscillator. It is composed of an active PMOS mirror. One branch is connected to a resistor R and the other feeds a ring oscillator. The current mirror ensures that the supply current of the ring oscillator is the same as that flowing through the resistor. The amplifier ensures that the potential across resistor R is equal to the supply potential of the ring oscillator. The frequency of the ring oscillator then depends only on the value of resistor R and the capacitive load C of each of the n stages of the ring oscillator. Capacitance C depends only very little on temperature. Resistor R can be chosen to have a very low temperature coefficient, which makes it possible to design an oscillator 121 having a moderate temperature drift.

[0072] Returning to [Fig.1a], the frequency division device 122 comprises:

[0073] - a programmable fractional frequency divider 122a via a binary word A encoding the division rank of the fractional frequency divider 122a. The fractional frequency divider 122a is configured to divide the frequency of the first signal providing a second signal; and

[0074] - a 122b integer frequency divider programmable via a binary word B coding the division rank of the integer 122b frequency divider. The programmable integer 122b frequency divider is configured to divide the frequency of the second signal delivering the periodic Spsf signal.

[0075] Thus, thanks to the fractional frequency divider 122a, the frequency of the first signal generated by the oscillator 121 does not need to be expressed as a power of 2 of the frequency of the final periodic Spsf signal. The frequency of the first signal can be chosen more flexibly. In particular, the higher the frequency of the first signal, the lower the phase noise of the final periodic Spsf signal for a given target frequency of the periodic Spsf signal.

[0076] For example, oscillator 121 is an integrated oscillator. Fractional frequency divider 122a may be configured to output a second signal having a frequency of 32.768 kHz. Thus, the entire frequency divider 122b may be programmed via a 16-bit binary word B to achieve a resolution of 1 Hz at the output of frequency division device 122.

[0077] In certain embodiments, the device 130 for measuring a frequency representative of the frequency of the periodic Spsf signal comprises a reciprocal counter powered, on the one hand, by the periodic Spsf signal and, on the other hand, by the reference Sref signal. According to such an implementation, the device 130 directly measures the frequency of the periodic Spsf signal.

[0078] More particularly, such a reciprocal counter is a counter which counts the occurrences (e.g. the rising or falling edges) of the periodic signal Sref during an opening duration equal to an integer number N of periods of the reference signal Spsf. The reciprocal counter delivers a binary word P representative of the frequency of the periodic signal Spsf according to the equation:

[0079] [Math.l] P=N~ i ps t

[0080] with Fpxf the frequency of the periodic Spsf signal and Fref the frequency of the reference Sref signal.

[0081] In other embodiments, the device 130 comprises a reciprocal counter supplied, on the one hand, by the first signal generated by the oscillator 121 and, on the other hand, by the reference signal Sref. According to such an implementation, the device 130 provides a measurement of the frequency of the first signal, i.e. an indirect measurement of the frequency of the periodic signal Spsf via knowledge of the division rank of the fractional frequency divider 122a and the division rank of the integer frequency divider 122b.

[0082] In other embodiments, the device 130 comprises a reciprocal counter supplied, on the one hand, by the second signal at the output of the fractional frequency divider 122a and, on the other hand, by the reference signal Sref. According to such an implementation, the device 130 provides a measurement of the frequency of the second signal, i.e. an indirect measurement of the frequency of the periodic signal Spsf via knowledge of the division rank of the integer frequency divider 122b.

[0083] In some of the embodiments in which the device 130 for measuring the frequency of the periodic Spsf signal comprises a reciprocal counter supplied, on the one hand, by the periodic Spsf signal and, on the other hand, by the reference Sref signal, a format of the binary word B coding the division rank is identical to a format of the binary word P representative of the frequency of the periodic Spsf signal.

[0084] More particularly, the frequency of the periodic Spsf signal obtained at the output of the frequency division device 122 is expressed according to the equation:

[0085] [Math.2] F f- —

[0086] with the frequency of the first signal generated by the oscillator 121.

[0087] By differentiating [Math.l] and [Math.2], we obtain that, to keep Fpsf constant while Fl varies:

[0088] [Math.3] dB = - j.dP

[0089] In particular, by choosing B - P, we obtain that dB — - dP. Thus, in embodiments in which the same format is implemented for the two binary words B and P, the variation of the binary words in question is identical. In such cases, for the frequency of the periodic signal Spsf to remain constant, it suffices to directly apply the two's complement of the binary word P delivered by the reciprocal counter to the integer frequency divider 122b. The implementation is thus simple and efficient. This result remains true when the device 130 comprises a reciprocal counter supplied, on the one hand, by the first signal generated by the oscillator 121 or by the second signal delivered by the fractional frequency divider 122a and, on the other hand, by the reference signal Sref.In this case also, to keep the frequency of the periodic Spsf signal constant, it is sufficient to directly apply the two's complement of the binary word P delivered by the reciprocal counter to the whole frequency divider 122b when the same format is used for both binary words B and P.

[0090] However, in other embodiments, the device 120 for generating the periodic Spsf signal does not comprise a frequency division device 122. The first signal is directly the periodic Spsf signal at the desired target frequency. In some of these embodiments, the programming information comprises e.g. a command of one (or more) parameters on which the frequency of the oscillator 121 depends (e.g. a supply current value, a capacitance value, a resistance value, etc.) in order to make the frequency of the generated periodic Spsf signal programmable.

[0091] We now present, in relation to [Fig.2], an example of the structure of the calculation device 160 allowing the execution of the steps of the method for generating the frequency-stabilized periodic Spsf signal of [Fig.3] according to an embodiment of the invention.

[0092] More particularly, the device 160 comprises a random access memory 203 (for example a RAM memory), a processing unit 202 equipped for example with a processor, and controlled by a computer program stored in a read-only memory 201 (for example a ROM memory or a hard disk). Upon initialization, the code instructions of the computer program are for example loaded into the random access memory 203 before being executed by the processor of the processing unit 202.

[0093] This [Fig.2] illustrates only one particular way, among several possible ones, of producing the device 160 so that it performs certain steps of the method for generating the frequency-stabilized periodic Spsf signal of [Fig.3] (according to any one of the embodiments described below in relation to [Fig.3], [Fig.3a] and [Fig.3b]). Indeed, these steps can be carried out indifferently on a reprogrammable computing machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (e.g. a set of logic gates such as an FPGA or an ASIC, or any other hardware module). Such a dedicated computing machine implements e.g. a state machine corresponding to the steps of the method for generating the frequency-stabilized periodic Spsf signal in [Fig.3].

[0094] In the case where the device 160 is produced with a reprogrammable computing machine, the corresponding program (i.e. the sequence of instructions) may be stored in a removable storage medium (such as for example a CD-ROM, a DVD-ROM, a USB key) or not, this storage medium being partially or totally readable by a computer or a processor.

[0095] We now present, in relation to [Fig.3], the steps of a method for generating the frequency-stabilized periodic Spsf signal according to an embodiment of the invention.

[0096] More particularly, such a method stabilizes the frequency of the periodic Spsf signal around a predetermined target frequency. To do this, the frequency of the periodic Spsf signal having been previously programmed at the level of the device 120 for generating the periodic Spsf signal via programming information, the calculation device 160 executes:

[0097] - a step E300 of determining a temperature drift of the device 120 of generation of the periodic signal relative to a reference temperature associated with the programming information.

[0098] For example, the reference temperature is substantially representative of a temperature of the device 120 for generating the periodic Spsf signal at the time when the calculation device 160 programs the device 120 for generating the periodic Spsf signal with the programming information.

[0099] Furthermore, the determination implements the temperature measurement device 140. For example, in certain embodiments ([Fig.3a]), the step E300 of determining the temperature drift of the device 120 for generating the periodic Spsf signal comprises:

[0100] - a step E300a of generating an activation signal for the measuring device 140 of temperature;

[0101] - a step E300b of receiving temperature information from the device 120 generating the periodic Spsf signal, the temperature information being sent by the temperature measuring device 140 in response to the activation of the temperature measuring device 140; and

[0102] - a step E300c of calculating the temperature drift of the device 120 of ge generation of the periodic Spsf signal as a function of the temperature information and the reference temperature. For example, the temperature drift is calculated from the difference between, on the one hand, the temperature conveyed by the temperature information and, on the other hand, the reference temperature.

[0103] However, in other embodiments, alternative implementations of the step E300 of determining the temperature drift of the device 120 for generating the periodic Spsf signal are envisaged. For example, the temperature measurement device 140 implements a logic part configured to directly provide such a temperature drift upon request from the calculation device 160 (e.g. according to a polling mechanism), rather than the temperature information itself.

[0104] Returning to [Fig.3], if the temperature drift is greater than a predetermined threshold, during a step E310, the calculation device 160 performs a calibration of the frequency of the periodic Spsf signal.

[0105] Conversely, if the temperature drift is less than the predetermined threshold, the calculation device 160 is configured to re-execute step E300 of determining a temperature drift of the device 120 for generating the periodic Spsf signal delivering an updated temperature drift. If the updated temperature drift is greater than the predetermined threshold, the calculation device 160 is configured to re-execute step E310 of calibrating the frequency of the periodic Spsf signal. If the updated temperature drift is still less than the predetermined threshold, the calculation device 160 is configured to re-execute step E300. In other words, the calculation device 160 is configured to periodically (or at predetermined dates) execute step E300 until the updated temperature drift is greater than the predetermined threshold.

[0106] Furthermore, the calibration of the frequency of the periodic Spsf signal implements the frequency measurement device 130 and the target frequency. For example, in certain embodiments ([Fig.3b]), the step E310 of calibrating the frequency of the periodic S psf signal comprises:

[0107] - a step E310a of generating an activation signal for the measuring device 130 of frequency;

[0108] - a step E310b of receiving frequency information representative of the frequency of the periodic Spsf signal. The frequency information is sent by the frequency measuring device 130 in response to the activation of the frequency measuring device 130;

[0109] - a step E310c of generating updated programming information in function of frequency information and target frequency for periodic Spsf signal; and

[0110] - a step E310d of programming the frequency of the periodic Spsf signal with updated programming information.

[0111] In such embodiments, when the computing device 160 executes a new iteration of step E310 of calibrating the frequency of the periodic Spsf signal, the reference temperature is updated on the basis of the temperature information. Such an updated reference temperature is associated with the updated programming information. Indeed, the updated reference temperature is substantially representative of the temperature of the device 120 for generating the periodic Spsf signal at the time when the calculation device 160 programs the device 120 for generating the periodic Spsf signal with the updated programming information, the latencies in the calculation device 160 being assumed to be low compared to the characteristic time of evolution of the temperature of the device 120 for generating the periodic SPsf signal.

[0112] However, in other embodiments, alternative implementations of the calibration of the frequency of the periodic Spsf signal are envisaged. For example, the device 120 for generating the periodic Spsf signal implements a logic portion configured to calibrate the frequency of the periodic Spsf signal according to the frequency information provided by the frequency measurement device 130. For example, the updated programming information directly includes the frequency information and the target frequency.

[0113] In certain embodiments, during step E310a, the calculation device 160 further generates a signal for activating the frequency reference 150. Correspondingly, during step E310b, the calculation device 160 generates a signal for deactivating the frequency reference 150. Thus, the frequency reference 150 is only activated when necessary for measuring the frequency drift. The consumption of the system 100 is thus further reduced.

Claims

Claims

1. System (110) for generating a frequency-stabilized periodic signal around a predetermined target frequency, comprising: - a device (120) for generating the periodic signal, a frequency of the generated periodic signal being programmable over a predetermined frequency range; - a device (140) for measuring a temperature representative of a temperature of the device for generating the periodic signal;and - a device (130) for measuring a frequency representative of a frequency of the periodic signal by implementing a periodic reference signal, characterized in that it comprises a calculation device (160) configured to execute, the frequency of the periodic signal having been previously programmed via programming information: - a determination (E300) of a temperature drift of the device for generating the periodic signal with respect to a reference temperature associated with the programming information, the determination implementing the temperature measurement device; and, if the temperature drift is greater than a predetermined threshold: - a calibration (E310) of the frequency of the periodic signal by implementing the frequency measurement device and the target frequency.;

2. The system of claim 1, wherein, if the temperature drift is less than the predetermined threshold, the computing device is configured to re-execute the determination of a temperature drift of the periodic signal generating device delivering an updated temperature drift, wherein, if the updated temperature drift is greater than the predetermined threshold, the computing device is configured to re-execute the calibration of the frequency of the periodic signal.

3. System according to claim 1 or 2, wherein the determination (E300) of the temperature drift of the device for generating the periodic signal comprises: - a generation (E300a) of an activation signal of the temperature measuring device; - a reception (E300b) of temperature information from the device for generating the periodic signal, the temperature information being sent by the temperature measuring device in response to activation of the temperature measuring device; and - a calculation (E300c) of the temperature drift of the periodic signal generation device as a function of the temperature information and the reference temperature.

4. System according to any one of claims 1 to 3, wherein the calibration (E310) comprises: - a generation (E310a) of an activation signal of the frequency measuring device; - a reception (E310b) of frequency information representative of the frequency of the periodic signal, the frequency information being sent by the frequency measuring device in response to the activation of the frequency measuring device; - a generation (E310c) of programming information updated as a function of the frequency information and the target frequency for the periodic signal; and - a programming (E310d) of the frequency of the periodic signal with the updated programming information.

5. A system according to claim 4 as dependent on claims 3 and 2, wherein, when the computing device performs a new iteration of the calibration of the frequency of the periodic signal, the reference temperature is updated on the basis of the temperature information, the updated reference temperature being associated with the updated programming information.

6. System according to any one of claims 1 to 5, wherein the device for generating the periodic signal comprises: - an oscillator (121) configured to generate a first signal; and - a programmable frequency division device (122) configured to divide the frequency of the first signal delivering the periodic signal, the programming information comprising at least one division rank for programming the frequency division device.

7. System according to claim 6, in which the device for measuring the frequency representative of the frequency of the periodic signal comprises a reciprocal counter supplied, on the one hand, by the periodic signal and, on the other hand, by the reference signal, the reciprocal counter delivering a binary word representative of the frequency of the periodic signal, the frequency information comprising the binary word representative of the frequency of the periodic signal, and wherein the frequency division device comprises an integer frequency divider (122b) programmable via a binary word encoding the division rank of the integer frequency divider, a format of the binary word encoding the division rank being identical to the two's complement of the binary word representative of the frequency of the periodic signal.

8. The system of claim 7, wherein the programmable frequency division device comprises a fractional frequency divider (122a) configured to divide the frequency of the first signal providing a second signal, the programmable integer frequency divider being configured to divide the frequency of the second signal providing the periodic signal.

9. System according to any one of claims 1 to 5, in which the device for generating the periodic signal comprises an oscillator configured to generate the periodic signal, the programming information comprising a control of at least one parameter of the oscillator on which the frequency of the periodic signal depends, the parameter belonging to the group comprising: - a supply current value; - a capacitance value; and - a resistance value.

10. Integrated circuit comprising a system (110) for generating a periodic signal according to any one of claims 1 to 9.

11. System (100) comprising: - a system (110) for generating a periodic signal according to any one of claims 1 to 9; and - a frequency reference (150) delivering the periodic reference signal.

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