EP1253488B1 - Time keeping device with automatic time correction and method for correcting such a time keeper - Google Patents

Description

The present invention relates to the radiosynchronization of timepieces whose setting can be done automatically from an RDS radio broadcasting transmitter (acronym of "Radio Data System").

It is known that the radio stations working in the FM frequency modulation band according to the RDS standard emit a time signal containing the time and date, this signal being encoded in a so-called CT portion of a frame transmitted with the audio signal. from the station.

FIG. 1 of the appended drawings shows the normalized baseband spectrum emitted by the stations of this type and modulating in frequency a carrier P whose frequency is specific to the transmitting station. We see that this spectrum has a first band B1, monophonic, located between 0 and 15 kHz and in which is contained the sum of the audio signals of the right and left channels of the signal to be transmitted. A 19 kHz FP pilot frequency is used to decode the stereo information, while a second stereophonic B2 band from 23 to 53 kHz contains the difference of the right and left audio signals. Finally, a third band B3 contains the RDS data. This spectrum band is centered on 57 kHz with a bandwidth between 54.5 and 59.5 kHz.

• une base de temps;
• des moyens pour afficher des données temporelles fournies par ladite base de temps; et
• des moyens pour corriger les données temporelles fournies; et dans lequel ledit dispositif de réception radio de type RDS comprend
• des moyens pour délivrer des données de type RDS tirées d'un spectre RDS reçu sur une porteuse à haute fréquence; et
• des moyens de commande qui, à partir des données de type RDS délivrées, commandent lesdits moyens de correction pour assurer la mise à l'heure du garde-temps.

Patent GB 2 238 438 discloses a timepiece equipped with a radio reception device of the RDS type and comprising:

• a time base;
• means for displaying temporal data provided by said time base; and
• means for correcting the temporal data provided; and wherein said RDS radio receiving device comprises
• means for delivering RDS data from an RDS spectrum received on a high frequency carrier; and
• control means which, from the delivered RDS type data, control said correction means to ensure time setting of the timepiece.

The radio reception device RDS described in the aforementioned patent uses the time data of the RDS frame contained in the band B3 of the spectrum of Figure 1 to ensure the radio synchronization of a clock provided as a timekeeper in the receiver. However, since the reception device is primarily intended for listening to the audio programs provided by the stations on which it can be granted, it must include reception circuits and sound reproduction that require a relatively large amount of energy to operate.

The receiving device must have a power source of large capacity whose radio synchronization removes a very small part. In the example given in the patent in question, in the case of a motor vehicle radio receiver, such a source is naturally readily available in the form of the on-board vehicle network so that the amount of energy required for the radio synchronization does not pose any problem to the designer.

It would be the same in the case of an RDS-type receiver made in the form of a conventional radio with radio synchronization of a built-in clock, because the dimensions of such a position would allow to house there batteries of sufficient capacity to provide power to all receiver circuits, including those of radio-synchronization, for a period of time acceptable to a user. Such radio sets could also be powered by the sector or an onboard network of a vehicle.

In the field of watchmaking, the energy storage capacity available in a timepiece, such as a wristwatch, is a permanent problem that watchmakers try to answer by reducing, as far as possible, the consumption of all the components of the timepiece in order to give it as much autonomy as possible with a battery of size compatible with that of the timepiece. The transposition of the concept described in the aforementioned patent to a timepiece worn for the purpose of radiosynchronizing using RDS data, thus faces a problem of power supply, because it is understood that a timepiece, such as a wristwatch, can not accommodate a power source of sufficient capacity that the assembly, including an RDS-type radio frequency receiver and radio-synchronized clock circuits can operate for a reasonable period of time.

Indeed, it is known that a wristwatch battery, for example, typically has a voltage of 1.3 V able to deliver a current of the order of 1 mA maximum only, with a lifetime of the stack extending preferably over a year or more.

Radiosynchronized watches are also known in which there is provided a radio receiver tuned to a station transmitting a time signal on a long wave carrier, typically between 40 and 80 kHz. These stations are exclusively dedicated to radio-synchronization and, because of their frequency of transmission and their power, they cover a territory extending over several time zones at a time. The time on which the watch equipped with the appropriate reception means will be synchronized will therefore not necessarily correspond to the time zone in which the user of the watch is located. On the other hand, the consumption related to the radio-synchronization function of such a watch is relatively low and in any case compatible with a period of normal use of the power source of the watch. The reason is that the low radio frequency, carrying the synchronization information, allows the use of means whose consumption is low. This prior concept can therefore also provide a satisfactory solution for the realization of a timepiece carried radio-synchronized by the broadcasts of high frequency radio stations transmitting time data according to the RDS standard.

The object of the invention is to provide a timepiece equipped with an RDS type radio reception device for the radio synchronization using the time data of the transmissions performed by any station of the RDS type received by the radio reception device. RDS type, the energy consumption of this timepiece is compatible with the energy storage capacity of batteries usually used in watchmaking.

The invention therefore relates to a timepiece as defined in independent claim 1.

Thanks to these characteristics, the internal time of the timepiece can be corrected according to the local time provided by an RDS-type transmitting station, the consumption of the radio reception part of the timepiece being reduced to a minimum by the that only the frequency band on which the temporal data is modulated is extracted from the demodulated frequency band of the received high frequency carrier.

In addition, since an RDS-type transmitting station has a reduced range, significantly smaller than the geographical area covered by a time zone, and since otherwise RDS stations are widely distributed in all geographical areas, the timepiece according to the invention will in all circumstances adopt the local time of the RDS-type transmitting station which, in the geographical area of the watch, has the transmission power necessary and sufficient for good reception. The change of time zone or the transition from winter time to summer time or vice versa is therefore automatic with the timepiece according to the invention.

In the present description, local time is understood to mean the time data provided by the RDS part of the FM signal and which indicates the date as well as the universal time GMT accompanied by the offset value corresponding to the geographical position of the transmitting station.

According to a preferred characteristic of the invention, said FM radio reception device of the RDS type comprises a frequency lock loop in the reaction branch from which is inserted a band rejection filter that does not let said frequency band comprising the RDS type data.

• lesdits moyens de commande comprennent des premiers moyens de mémoire pour enregistrer les données horaires internes fournies par ladite base de temps, des seconds moyens de mémoire pour enregistrer les données horaires locales décodées à partir des données de type RDS reçues d'au moins un émetteur à modulation de fréquence, et des moyens d'analyse pour comparer les données horaires locales aux données horaires internes et pour corriger l'heure du garde-temps, lorsque ces données locales et internes diffèrent.

According to still other interesting features of said timepiece:

• said control means comprises first memory means for storing the internal time data provided by said time base; second memory means for storing the decoded local time data from the RDS data received from at least one transmitter; frequency modulation, and analysis means for comparing the local time data with the internal time data and for correcting the time of the timepiece, when these local and internal data differ.

The subject of the invention is also a method for setting a timepiece by radio-synchronization, said method being defined by independent claim 4.

• il est exécuté à des instants séparés par des intervalles de temps prédéterminés et il consiste à interrompre la réception dudit signal d'émission pendant lesdits intervalles prédéterminés;
• il consiste à capter le signal d'émission d'un premier émetteur à modulation de fréquence contenant des données de type RDS, à extraire de ce signal des premières données horaires locales, à comparer ces premières données horaires locales à l'heure interne dudit garde-temps, en cas d'écart entre les premières données horaires locales et l'heure interne, à capter au moins un second signal d'émission d'un second émetteur à modulation de fréquence contenant des données de type RDS, à extraire de ce second signal de type RDS des secondes données horaires locales, à comparer les secondes données horaires locales aux premières données horaires locales, et à procéder à la mise à l'heure dudit garde-temps pour n'annuler ledit écart que si les premières données horaires locales sont égales aux secondes données horaires locales;
• dans le cas où ladite heure interne diffère desdites données horaires locales d'une ou plusieurs heures entières, il consiste à ne corriger que l'information des heures dudit garde-temps;
• il consiste à analyser l'évolution de la différence entre ladite heure interne et lesdites données horaires locales et à exécuter une correction de la convergence de marche dudit garde-temps, si ladite différence indique une erreur systématique sur plusieurs opérations de comparaison successives de ladite heure interne et desdites données horaires locales.

According to other advantageous features of this process:

• it is executed at times separated by predetermined time intervals and it consists in interrupting the reception of said transmission signal during said predetermined intervals;
• it consists in sensing the transmission signal of a first frequency modulation transmitter containing RDS type data, in extracting from this signal first local time data, in comparing these first local time data with the internal time of said guard time, in the event of a difference between the first local time data and the internal time, to receive at least a second transmission signal from a second frequency modulation transmitter containing data of the RDS type, to extract from this second RDS-type signal of the second local time data, to compare the second local time data with the first local time data, and to proceed to the time setting of said timepiece to cancel said difference only if the first time data local are equal to second local time data;
• in the case where said internal time differs from said local time data by one or more whole hours, it consists in correcting only the information of the hours of said timepiece;
• it consists of analyzing the evolution of the difference between said internal time and said local time data and performing a correction of the running convergence of said timepiece, if said difference indicates a systematic error on several successive comparison operations of said time internal and local time data.

• la figure 1 déjà décrite est un diagramme représentant le spectre normalisé en bande de base d'une émission radio FM comportant un signal de type RDS;
• la figure 2 est un schéma simplifié d'un garde-temps porté radiosynchronisé selon l'invention;
• la figure 3 est un organigramme illustrant le fonctionnement du garde-temps selon l'invention; et
• la figure 4 montre une variante de réalisation du dispositif de réception radio du garde-temps suivant l'invention.

Other features and advantages of the present invention will become apparent from the following description, given solely by way of example and with reference to the appended drawings, in which:

• FIG. 1 already described is a diagram representing the normalized baseband spectrum of an FM radio transmission comprising an RDS type signal;
• Figure 2 is a schematic diagram of a timepiece worn radio-synchronized according to the invention;
• Figure 3 is a flowchart illustrating the operation of the timepiece according to the invention; and
• Figure 4 shows an alternative embodiment of the radio reception device of the timepiece according to the invention.

In Figure 2, there is shown a radio-synchronized timepiece according to the invention, preferably in the form of a wristwatch, comprising a time base 1 providing hourly data. These are applied to time setting means 2 allowing manual adjustment of the timepiece by means of a crown mechanism 3. The hourly data are loaded into memory means 4 and applied to a display device 5. The memory means 4 contain progressive information of the seconds, minutes and hours and other temporal information such as the day, the date, the year, etc. These data will be referred to hereinafter as "internal data". They correspond to the "internal time" of the timepiece.

All the means that have just been described are well known to watchmakers and therefore do not need to be described in detail. They can be subject to many variants, all equally well known. For example, the display device 5 may be analog or digital or may present both types of display at a time. Likewise, other time indication functions, for example day and date, chronograph and / or countdown function, etc. can be provided. All of these means is managed for example by a microcontroller 6.

The worn timepiece also includes a radio reception device 7 type RDS. An antenna 8 capable of sensing the FM band of FM stations transmitting RDS information applies a received carrier signal to a low noise amplifier 9 whose output signal is transmitted to a frequency lock loop 10 The antenna 8 can be made as described in EP 0 399 482, for example.

The frequency locked loop 10 comprises a mixer 11, an intermediate frequency amplification and filtering circuit 12, an oversampling circuit 13, a demodulator 14 of the frequency modulation, a local oscillator 15 controlled by a voltage and a band stop filter 16 mounted in the reaction branch of the frequency locked loop, the local oscillator 15 being looped back to the mixer 11.

Apart from the filter 16, the frequency lock loop 10 may be similar to that described in US Patent 4,426,735, for example. The oversampling circuit 13 may be that described in patent EP 0 624 959.

The filter 16 is made in such a way that it lets all the demodulated frequency spectrum pass except for the standardized frequency band for the transmission of the RDS information. Therefore, the filter 16 does not let the frequency band between 54.5 and 59.5 kHz, centered on the frequency of 57 kHz. It can be done in accordance with the requirements described in an AB Williams and FJ Taylor Manual entitled "Electronic Filter Design Handbook". Electronic Filter Design) and edited by McGraw-Hill, Inc., New York, USA

Thanks to the presence of the filter 16, the frequency lock loop 10 attenuates all the frequencies of the modulated spectrum on the carrier of the transmitting station except the RDS band B3 (Figure 1) which will therefore appear in demodulated form at the output of the demodulator 14 The latter is further connected to an RDS demodulator 17, in which the RDS information is demodulated and transmitted to a decoding circuit 18. The latter is designed to extract from the RDS information the hourly data representing the time of day. a radio station of local RDS type in the reception area of which is the timepiece equipped as just described. In other words, the receiver device 7 rejects the spectrum of the demodulated band contained in the received radio signal, with the exception of the frequency band in which the CT frame of the RDS information is coded.

Thus, the radio reception device 7 of the timepiece according to the invention is devoid of the circuits for restoring the audio information contained in the received signal so that its consumption can be limited to a strict minimum while being compatible with the duration of life that is usually required of a watch battery.

The local time data provided by the decoding circuit 18 are introduced into memory means 19. The memory means 4 and 19 are connected to the microcontroller 6 responsible for operating them as described below. These hourly data contained in the memory 19 are scalable and will be called "local data". They correspond to a "local time" of the transmitter picked up at a given moment.

Thus, receiving the "internal" time determined by the time base 1 and the "local" time contained in the RDS information received over the air via the radio reception device 7, the microcontroller 6 can be programmed to implement a strategy for controlling the internal time and, if necessary, setting the timepiece.

According to an advantageous variant, the microcontroller 6 can also be used to monitor the evolution over time of the differences between the internal and local hours and, if this evolution shows a systematic error of operation of the timepiece, to order a correction of walk. US Pat. No. 3,895,486 describes a timepiece having such correction means.

An example of such a strategy is illustrated by the flow chart of Figure 3.

To check the time of the timepiece, it is first carried out at step E1, in search of a transmitter providing a radio program in frequency modulation comprising an RDS type signal. To control a search, the microcontroller 6 applies an appropriate signal to the local oscillator 15 via a connection 20, the search being able to be performed by varying the tuning frequency in steps of 100 kHz, for example . A transmitter will be retained, when the received signal level exceeds a predetermined value sufficient to ensure good detection of the RDS type signal.

As soon as such a transmitter is found, the demodulated RDS signal appears at the output of the demodulator 17. The corresponding signal is applied to the decoder 18 and the local time data is placed in the memory means 19 (step E2).

Step E3 compares the current internal data placed in the memory means 4 with the decoded local data and placed in the memory means 19. If the data coincide, the internal time of the timepiece corresponds to the local time. of the transmitter in question and it is assumed that the timepiece indicates the correct time, no action being taken.

Preferably, the microcontroller 6 controls the standby of the receiver 7 (step E4) so as to save power supply.

The microcontroller 6 is preferably programmed so that the receiver 7 is powered again after a predetermined period of time (step E5), so that a new control of the internal time can take place. Preferably, the time interval between two consecutive checks of the internal time will be made adjustable by means of the setting control 2, an appropriate display of this interval and its possible modification may also take place on the device. 5. It is also possible to provide in addition to or instead of an automatic command, a manual control of the time control which can then be triggered at the discretion of the user of the timepiece, for example by via a function assigned for this purpose to the crown mechanism 3 and to the time setting device 2.

If, during step E3, the internal time does not correspond to the local time, it is of course possible that the timepiece does not have the exact time, but it is also possible that the transmitter found indicates an incorrect time. This is why in step E6, a new transmitter search is carried out. This search takes place under the same conditions as during the execution of step E3.

As soon as a new transmitter is found, in step E7, the second local time data provided by this transmitter are decoded and also placed in the memory means 19. The microcontroller 6 compares with during step E8 between the local time provided by the previous transmitter and the time that has just been decoded and coming from the second transmitter.

If there is coincidence between the two time values, it can be concluded that the internal time is false and that the local time data provided successively by the two transmitters are accurate.

In step E9, the microcontroller 6 then controls the storage of the difference Δt between the local time and the internal time.

If, on the contrary, the local hours of the two transmitters established during steps E2 and E7 respectively do not coincide, it must be assumed that these transmitters have neither the exact time. Preferably, the microcontroller 6 then controls the standby of the receiver 7 (step E4), a new time control can be performed after expiration of the standby interval.

In the case shown, it is assumed that the timepiece is provided with a so-called coherence function whereby the microcontroller 6 is able to adjust the step of the time base 1 when it presents a drift as mentioned previously. The method described makes it possible to correct the step, for example, when a systematic error due to this drift is observed in the timepiece's progress.

Thus, in the example described, in step E10, a test is carried out to check whether the Δt values recorded successively, at regular time intervals, during consecutive control processes increase or decrease systematically. If this is not the case, during a step E11 it is then proceeded to setting the time of the timepiece by correcting the internal time of the value Δt.

Of course, in the absence of said step coherence function, the microcontroller 6 can proceed to the correction of the internal time as soon as a difference Δt is detected (step E9).

During the time setting of the timepiece (step E11), it is possible to correct not only the time, but also the date (day, month, year). The method according to the invention thus allows to reset the timepiece according to the time zones in which it is worn, this registration can be made as and when the spindles are crossed, for example during a trip. It does not matter then that the next time zone is shifted by half an hour compared to the previous one as it is the case for certain time zones, the time setting being also carried out in this case. Of course, if the shift is one or more hours, it is enough to correct only the internal data of the hours as well as the display of the hours.

If the test in E10 leads to an affirmation, the microcontroller 6 proceeds to the setting of the convergence of step (step E12) by acting, in a manner known per se on the basis of time 1, before proceeding to the setting time of step E11.

It is clear to specialists that the radio-synchronization as just described is particularly useful in worn timepieces such as wristwatches in which the power supply is provided by a low-capacity rechargeable battery by a generator animated by movements to wear. Indeed, such watches stop quickly when they are not worn. The method according to the invention allows, when the watch is resumed, not only a precise time setting, but also the correction of other time data such as day, date and year.

The method according to the invention is also very effective for all the timepieces powered by a battery. After changing the battery, the correction of its hourly data is then automatic and precise.

As already indicated above, if after comparison of the internal time and the local time, only the values of the hours differ, the microcontroller 6 can conclude either at a passage from the winter time to the daylight saving time, or a change of time zone due to the passage of the timepiece holder from one time zone to another.

FIG. 4 represents an alternative radio reception device 7A which, in addition to the circuits similar to those of FIG. 2 and provided with the same references, comprises a phase-shifter 21 connected to the output of the broadband amplifier 9. A first signal received modulated carrier, not out of phase, is applied to a first mixer 22, while a second modulated carrier signal received, out of phase by 90 °, is applied to a second mixer 23. The outputs of the two mixers 22 and 23 are connected the circuit 12 of amplification and filtering intermediate frequency.

In the foregoing description, the term "timepiece" worn should be interpreted broadly. Thus, it applies not only to wristwatches in particular, but also to any timepiece equipped with a low-capacity energy source, such as travel alarms or the like.

It is also clear that the method described in relation, in particular, with FIG. 3 is capable of numerous variants as a function of the correction strategies adopted.

Claims (9)

1. A portable timekeeper equipped with a radio reception device capable of decoding radio data system (RDS) information (7; 7A) and comprising:

   - a timebase (1),

   - means (5) for displaying time data supplied by said timebase, and

   - means (2, 3) for correcting said time data,

   and in which said radio reception device (7; 7A) comprises:

   - means (10) for delivering RDS data derived from an RDS spectrum received on a high-frequency carrier; and

   - control means (4, 6, 19) which, on the basis of the delivered RDS data control said correction means (2) to ensure time setting of the timekeeper,

   characterized in that:

   - said radio reception device (7; 7A) further includes means (10) designed for rejecting the baseband audio spectrum received from a frequency modulated transmitter supplying RDS data, except for the frequency band containing the RDS data, and in that

   - the timekeeper comprises RDS data decoding means (18) adapted to decode only local time data in said RDS data.
2. A timekeeper according to claim 1, characterized in that said radio reception device (7; 7A) includes a frequency locking loop (10) in the feedback branch of which is inserted a band stop filter (16) blocking said band of frequencies containing the RDS data.
3. A timekeeper according to claim 1 or 2, characterized in that said control means (4, 6, 19) comprise:

   - first memory means (4) for storing the internal time data supplied by said time base (1),

   - second memory means (19) for storing local time data decoded from RDS data received from at least one frequency modulation transmitter, and

   - analyzer means (6) for comparing the local time data to the internal time data and for correcting the time of the timekeeper if the local data and the internal data are different.
4. A method of setting a portable timekeeper to the correct time by radiosynchronization, consisting of:

   - searching for the transmission signal of a frequency modulation transmitter whose spectrum contains RDS data,

   - demodulating the RDS data and decoding the local time data contained in said RDS data,

   - comparing the internal time of said timekeeper to the local time data decoded in this way, and

   - where applicable, adjusting the internal time of said timekeeper if said internal time differs from said decoded local time data,

   which method is characterized in that:

   - it also comprises a step of rejecting the baseband audio spectrum received from said transmitter, except for the band of frequencies containing the RDS data, and a step which consists in decoding only local time data in said RDS data.
5. A method according to claim 4, characterized in that it is executed at times separated by predetermined time periods and consists in interrupting the reception of said transmission signal during said predetermined time periods.
6. A method according to either claim 4 or claim 5, characterized in that it consists in:

   - receiving the transmission signal containing RDS data from a first frequency modulation transmitter,

   - extracting first local time data from said signal,

   - comparing said first local time data with the internal time of said timekeeper,

   - in the event of any discrepancy between the first local time data and the internal time, receiving at least a second transmission signal containing RDS data from a second frequency modulation transmitter,

   - extracting from said second transmission signal second local time data,

   - comparing the second local time data to the first local time data, and

   - setting the time of said timekeeper to cancel said discrepancy only if the first local time data is equal to the second local time data.
7. A method according to any one of claims 4 to 6, characterized in that, if said internal time differs from said local time data by one entire hour or a plurality of entire hours, the method corrects only the hours information in said timekeeper.
8. A method according to any one of claims 4 to 7, characterized in that it consists in analyzing the evolution of the difference between said internal time and said local time data and correcting the rate convergence of said timekeeper if said difference indicates a systematic error over several consecutive operations of comparing said internal time and said local time data.
9. A method according to any one of claims 4 to 8, characterized in that the rejection of the baseband audio spectrum received from said transmitter, except for the band of frequencies containing a RDS data, is realized thanks to the insertion, in the feedback branch of a frequency locking loop (10) of the timekeeper, of a band stop filter (6) blocking said band of frequencies containing the RDS data.

Images