EP0588042A2 - Radio clock - Google Patents

Abstract

The invention relates to an autonomous radio clock, the time-incrementing of which is monitored by reception of a so-called time message output by a radio transmitter and is also corrected when deviating from the so-called absolute time radiated by the radio transmitter. In the case of disadvantageous conditions of reception at the site of the radio clock, its receiver (2), cooperating with a decoder (5), can frequently only receive faulty time messages which are no longer decodable. According to the invention, a filter unit (4) is connected between receiver (2) and decoder (5), which filter unit, when the receiver (2) is switched on, generates from the time message a filtered time message (32) obtained on the basis of the analysis of typical reception faults and generates as an indicator of the conditions of reception at the selected site a control signal (33) which occurs at least once, and is rendered recognisable to the user of the radio clock, when a faulty time message is received. <IMAGE>

Description

The invention relates to a radio clock according to the preamble of patent claim 1.

Such a radio clock is known for example from DE-C1-34 39 638. Its particularly accurate time display is based on the fact that it is checked from time to time whether the current time display, which due to the advancement of a time register controlled by a time-keeping circuit, matches the current absolute time. The current absolute time is broadcast in coded form by a transmitter and decoded by a receiver built into the radio clock and tuned to this transmitter. The absolute time is coded in the form of a so-called time telegram, which is continuously broadcast in Germany by a long-wave transmitter, for example.

In particular, the time telegram of this long-wave transmitter consists of 59 pulses, each starting at a second. A logical "0" is transmitted by a pulse length of 100 milliseconds and a logical "1" by a pulse length of 200 milliseconds. The exact definition of the signals of the time telegram can e.g. in W. Hilberg, Funkuhrtechnik, Oldenbourg Verlag, Munich, 1988, pp. 29 - 45.

The time determined from the time telegram by means of a decoder is entered in the time register of the time-keeping circuit. In the event that the absolute time deviates from the time held in the time register, the time display is corrected on the basis of the time information received.

In order to be able to determine when commissioning or during the operation of the radio clock whether under the given reception conditions at the installation location of the radio clock a display correction by means of a received time telegram is to be expected at all, an indicator pointer is provided in the known radio clock, which continues to switch at the decoding frequency until an absolute time information could be decoded. A restless run of the indicator pointer is a sure indication that, under the current reception conditions at the location of the radio clock, it is not possible to receive the coded time information undisturbed. A correction of the time display is therefore not to be expected under these reception conditions.

From DE-A1-37 31 956 a radio clock with an additional two-digit digital display is known, which is increased by the value "1" every hour starting from the value "0" and by the value "1 when the time telegram, which is also queried every hour, is received completely "is lowered. If this digital display shows the value "0", this means that all time telegrams received since the start of operation could be completely evaluated. A value of, for example, 10 on the digital display indicates that a total of 10 time telegrams were received so badly that they could no longer be decoded and therefore could not be used.

A major disadvantage of this known radio clock is that its user - although he knows with a correspondingly high counter reading that the reception conditions at the chosen installation location are not sufficient - can only recognize after a change in the installation location after an hour whether the change of installation location the desired effect, namely an error-free reception of the last time telegram. Because the reception conditions, particularly within buildings, also at locations that are not very different from each other can be very different, many attempts and a correspondingly high expenditure of time are often necessary to find a suitable installation site by "trying".

From EP-A2-0 455 183 an autonomous radio clock with an indicator for the reception conditions at the chosen installation location is also known. In this case, the indicator consists of a display for the reception field strength. The display is expediently activated only when the receiver is switched on, which can be done either manually by the user of the watch by pressing a specific button or by the control unit of the watch automatically at certain time intervals, preferably after the hour has elapsed. Although the user can search for a location of higher field strength rather quickly by means of the reception field strength display, this known radio clock has the disadvantage that the user must firstly remember which field strength value is generally sufficient for undisturbed reception of a time telegram. On the other hand, he receives no direct statement as to whether the time telegram itself has been received without interference, but only the indirect statement that the reception field strength at the selected installation location should be sufficient for this. Finally, the user of the radio clock has to put up with the fact that in many cases he cannot receive a complete and therefore no usable time telegram at reception field strengths that are in the limit range.

It is therefore an object of the invention to improve a generic radio clock in such a way that, on the one hand, its user can determine a location with sufficient reception conditions relatively quickly by "trying" directly on the quality of the received time telegram, and on the other hand the quality of a received time telegram in the limit range of the received field strength is improved so that it can still be used for checking or correcting the time register of the autonomous radio clock.

This object is achieved for a radio clock according to the preamble of claim 1 by its characterizing features.

Due to the characterizing features of patent claim 1, the user of the radio clock is initially shown whether the received time telegram could itself be decoded without interference or not. The user thus receives a direct statement about the question that ultimately interests him only, namely the usability of the radio signal given by the receiver to the decoder. He is therefore not dependent on indirect information, such as the reception field strength at the installation site, which can lead to misleading conclusions in one case or another - especially in the border area of the necessary reception field strength. In addition, a filtered output signal is generated by the filter unit whenever a reception disturbance is detected, with the filtering process utilizing knowledge that has been obtained in the analysis of typical reception disturbances. If no reception disturbance is detected, the pulses of the filtered time telegram match those given by the decoder. In this case, the control signal also disappears.

The user is thus not only provided with a means of checking the reception conditions, but also a radio clock in which there are very good chances even in the limit range of the reception conditions that the filtered output signal can be used by the control unit. The radio clock is also still with poor reception conditions are continuously synchronized, ie the content of the time register is compared with the time telegram and corrected accordingly in the event of a deviation.

The development of the invention according to claim 2 has the advantage that N signals are available at the N outputs of the shift register, which come from the last N samples of the time telegram controlled by the oscillator. If one feeds the N signals to the N inputs of a read-only memory and considers a special N-tuple of values as the address of a specific memory location in the read-only memory, one can store three bits under this address, which are based on the analysis of typical reception disturbances have been obtained. This 3-bit pattern consists of the control signal itself and the other two bits for setting and resetting an R / S flip-flop, at the output of which the filtered time telegram is output.

It has been shown that, in practice, very good results can already be achieved with a 4-stage shift register, ie with the last four scans of the time telegram controlled by the oscillator (cf. claim 3). This applies both with regard to the result of the filtering of the time telegram and with regard to the meaningfulness of the control signal. In practice it has been shown that in a 4-stage shift register with the link described in claim 4 between the address inputs and the storage space occupancy of the read-only memory and the link also described in this claim between the outputs of the read-only memory on the one hand and the both inputs of the R / S flip-flop, on the other hand, already achieved quite good results. The links described there result in both good filter results and a high informative value of the control signal for the faults in the time telegram that occur in practice.

The visualization of the control signal on the display panel (claim 5) is advantageous in that the reception conditions at the installation site of the radio clock can be most easily assessed by its user with an optical indicator, without having to disturb other people present in the room.

The embodiment of the invention according to claim 6 has the advantage that for the user on the one hand only short-lasting fluctuations in the control signal and on the other hand very frequently occurring control signal disturbances are displayed in an easier to read manner.

• "Empfänger ausgeschaltet, letzter Empfang gelungen"
• "Empfänger ausgeschaltet, während des letzten Einschaltens kein verwertbares Zeittelegramm empfangen"
• "Empfänger eingeschaltet, keine Empfangsstörungen"
• "Empfänger eingeschaltet, gestörtes Zeittelegramm".

It is also advantageous if the user has a further optical indicator available, which is activated on the one hand when the receiver is switched on (claim 7), and on the other hand remains activated even after the receiver has been switched off if during the on-period of the Receiver could not be decoded a complete time telegram (claim 8). The user of the radio clock thus has the possibility of recognizing four operating states of the radio clock, namely:

• "Receiver switched off, last reception successful"
• "Receiver switched off, no usable time telegram received during the last switch-on"
• "Receiver switched on, no interference"
• "Receiver switched on, faulty time telegram".

The development of the radio clock according to claim 9 has the advantage that the user is provided with an optical indicator, which he already knows in the case of the so-called "magic eye" from radio technology or with which in the case of the "magic eye" surrounding circle a clearly recognizable, but the information displayed on the display unit (time and possibly also date) is not disruptive.

Finally, if the radio-controlled watch is further developed according to claim 10, it can be manufactured without some discrete components and thus with less assembly effort. In addition, space can be saved on the circuit board in question, so that the clock can be made more compact overall. Finally, in many cases a microprocessor is already used for time advancement and also for controlling special functions, for example the delivery of a wake-up signal, which is generally not fully utilized, so that it can also take over the function of the filter.

Fig. 1

ein Blockschaltbild der erfindungsgemäßen Funkuhr, bei der zwischen Empfänger und Decoder ein Filter geschaltet ist,

Fig. 2

den internen Aufbau des Filters mit diskreten Bauteilen,

Fig. 3a-3d

verschiedene Impulsdiagramme, die bei Abtastung eines ungestörten und eines gestörten "0" bzw. "1"-Pulses des Zeittelegramms erhalten werden, und

Fig. 4

eine Tabelle mit der Verknüpfung zwischen Adresse und der Belegung des 3-Bit-Musters des Nur-Lesespeichers.

An exemplary embodiment of the invention is described in more detail below. Show it:

Fig. 1

2 shows a block diagram of the radio clock according to the invention, in which a filter is connected between the receiver and decoder,

Fig. 2

the internal structure of the filter with discrete components,

3a-3d

Various pulse diagrams, which are obtained when scanning an undisturbed and a disturbed "0" or "1" pulse of the time telegram, and

Fig. 4

a table with the link between the address and the assignment of the 3-bit pattern of the read-only memory.

The block diagram of a radio-controlled clock designated by reference number 1 in FIG. 1 consists of a receiver 2, a decoder 5, a control unit 6, a time-keeping circuit 7 and a display unit 8. The receiver 2 in turn has an antenna, an amplifier and a demodulator (All components not shown), the demodulator converting the received radio signal back into a serial digital signal. The digital signal - hereinafter referred to as a time telegram - provides absolute time information. The transmitter can be the long-wave transmitter DCF 77, which broadcasts the legal time of the Federal Republic of Germany, controlled by a so-called "atomic clock". The following description is based on the example of the time information distributed by this transmitter.

The transmission of a complete time telegram, which contains 59 pulses, each beginning one second apart, takes one minute. A logical "0" is transmitted by a pulse length of 100 ms and a logical "1" by a pulse length of 200 ms. The absolute time is transmitted in BCD-coded form. The exact definition of the time telegram can be found in the relevant literature, e.g. in W. Hilberg, Funkuhren-Technik, Oldenbourg-Verlag, Munich, 1988, pp. 29 - 45.

The decoder 5 determines the current time from such a time telegram and forwards it to the control unit 6. The control unit 6 has access to the time-keeping circuit 7, which switches the time autonomously by means of a quartz resonator when the receiver 2 is switched off or the transmitter fails. Each time after receiving an error-free time telegram, the time information received via the transmitter is transmitted to the time-keeping circuit 7.

The current time (not shown) is output on a display unit 83 on a display unit 8. An optical indicator 82 and a further optical signal 81 can also be output on the display unit 8, the meaning of which will be described in detail below.

According to the invention, a filter 4 is connected between the decoder 5 and the receiver 2, which receives the time telegram 31 at its input and is connected to the decoder 5 at one of its two outputs, while its other output is connected to an input of the control unit 6 . The output of the filter 4 connected to the decoder 5 emits a filtered time telegram 32, while the output connected to the control unit 6 emits a so-called control signal 33, which is fed to another input of the control unit 6 and as an indicator of the reception conditions at the installation site Radio clock is used.

The operation of the filter is explained below with reference to FIGS. 2 and 3a-3d. The filter 4 has an oscillator 41, the output of which clocks the clock input of a 4-bit shift register 42 periodically at a frequency of 64 Hz. The unfiltered time telegram 31 is present at the input of the shift register 42, while its four outputs Q1, Q2, Q3 and Q4 are connected to the corresponding four inputs A1, A2, A3 and A4 of a read-only memory (ROM) 43. The last four signal levels sampled on the time telegram 31 are thus at the outputs of the shift register 42. The ROM 43 contains 16 x 3 memory cells, which are permanently programmed. The four inputs A1, A2, A3 and A4 serve to receive the so-called address lines starting from the shift register 42, ie the 4-bit pattern offered to the ROM 43 on each of these clock cycles represents an address under which a specific 3-bit pattern is stored in each case. This 3-bit pattern is then in each case at the three outputs D1, D2 and D3 of the ROM 43. The output D1 of the ROM 43 is connected to the set input S of an R / S flip-flop 44, while the output D2 of the ROM 43 is connected to the reset input of the R / S flip-flop 44, the output Q of the flip-flop 44 Flops 44 the filtered time telegram 32 is present. The remaining output D3 of the ROM 43 emits the control signal 33, which is intended to identify faults in the time telegram 31.

It has been found that, in practice, very satisfactory results are achieved if the 3-bit patterns stored under different addresses of the ROM 43 are assigned as shown in FIG. This table shows that, for example, the 3-bit pattern "0, 0, 1" is stored under the address "0, 0, 1, 0". This means that this bit pattern is present at the outputs D1, D2 and D3 in the order mentioned, so that a "0" signal is present both at the set and at the reset input of the R / S flip-flop 44. The binary control signal 33 has the value "1" and thus indicates that the time telegram 31 contains at least one fault, which in turn allows conclusions to be drawn about the reception conditions at the installation site of the radio clock. The situation is different if the address "0, 0, 1, 1" is present at the input of the ROM 43, since in this case the control signal 33 has the binary value "0" at the output D3, but the outputs D1 and D2 follow as before both keep the binary value "0".

The filter works as follows:
By programming the ROM 43, it can be determined which signal sequences lead to the setting or resetting of the R / S flip-flop 44 and which signal sequences contain faults which are then displayed via the output D3 of the ROM 43 - ie the control signal 33 . 3a are the binary values Q1, Q2, Q3 and Q4 at the output of the shift register 42 and the binary value of the filtered time telegram 32 can be seen in the event that an undisturbed "0" pulse is contained in the time telegram 31. The "0" pulse is sampled seven times with the value "1" at a duration of 100 ms and a clock frequency of 64 Hz, so that the outputs Q1, Q2, Q3 and Q4 are offset by one clock, seven times the binary value " 1 "appears. If one checks all the addresses defined by the outputs Q1, Q2, Q3 and Q4 on the basis of the table shown in FIG. 4, one finds that the bit D3 has the value "0" in all associated 3-bit patterns. At the same time it can be seen that the R / S flip-flop 44 is set by the address "1, 1, 1, 1" (D1 has the value "1") and only by the address "0, 0, 0, 0 "is reset (bit D2 then has the value" 1 "). In this way, the filtered time telegram 33 at the output Q of the R / S flip-flop 44 also consists of the binary value "1" for seven consecutive clocks, ie the undisturbed 31 and the filtered 32 time telegram match, but are through the effect of the filter 4 staggered in time. This constant time offset is taken into account by decoder 5 when determining the current time.

In the event of an undisturbed "0" pulse in the time telegram 31, a control signal 33 that disappears consistently on the one hand and identity between the filtered time telegram 32 and the unfiltered time telegram 31 on the other hand result.

The same applies if an undisturbed "1" pulse occurs in a time telegram that lasts 200 ms and is therefore sampled 13 times at a frequency of 64 Hz. This can be understood in detail in the same way with reference to FIG. 3b and the table shown in FIG. 4.

FIG. 3c shows a strongly disturbed "0" pulse in the time telegram 31. If the table shown in FIG. 4 is used again, the result "Q" at the output Q of the R / S flip-flop 44 is completely undisturbed by the filtering "Pulse, which - like the undisturbed" 0 "pulse from Fig. 3a - consists of seven consecutive signals with the binary value" 1 ". A significant improvement in the time telegram 31 has thus been achieved by the filter 3, so that the time telegram 31 can also be used in locations with moderate or even poor reception conditions. The control signal 33 is quite different from the undisturbed "0" or "1" pulses. While the control signal 33 with undisturbed "0" and "1" pulses after each cycle of the oscillator 41, the value " 3 ", the control signal 33 has the value" 1 "11 times in total for a pulse according to FIG. 3c and thus clearly indicates the considerable disturbance of the" 0 "pulse. For the first time, the control signal 33 has the value "1" after the fifth cycle of the oscillator 41 (cf. the table in FIG. 4). The same applies to clocks 6, 12, 13 etc., with control signal 33 also having the value "1" during the last three clocks.

In the same way, it can be seen from Fig. 3d that the disturbed "1" pulse in the time telegram 31 after passing through the filter 4 appears as a completely undisturbed "1" pulse in the filtered time telegram 32, since the latter again during 13 cycles Has a value of "1". Unlike an undisturbed "1" pulse, the value "1" occurs for the control signal 33 during eight cycles, which in turn indicates that the "1" pulse is subject to considerable interference.

A signal inverse to the control signal 33 is made visible on the display unit 8 by means of an optical indicator 82, which has the shape of a so-called "magic eye".

By making a signal inverse to the control signal 33 visible, the indicator 82 is permanently visible in the time telegram 31 in the case of undisturbed pulses, so that the user of the radio clock receives confirmation of the good reception conditions at its installation site.

Since all of the control signals 33 ascertained from FIGS. 3c and 3d occur relatively frequently, the indicator 82 is made visible by the control unit 6 by a measure of no interest here in a 1-second cycle, each with a half-second pause. In this way, the user of the radio clock is made noticeably aware of the relatively poor reception conditions at its place of installation. In the event that the control signal assumes the value "1" only for a short time, for example for less than 0.5 seconds and then assumes the value "0" for a longer time, for example a few seconds, the inverse signal becomes to the control signal 33 for this period of time, that is to say made visible for, for example, 0.5 seconds, in order to indicate to the user clearly even minor reception disturbances.

Betriebszustand 1:

Kreis 81 sichtbar und Indikator 82 dauersichtbar, d.h. Empfänger 2 eingeschaltet, verschwindendes Kontrollsignal, damit gute Empfangsbedingungen.

Betriebszustand 2:

Kreis 81 sichtbar, Indikator 82 aber immer wieder für 0,5 Sekunden bzw. im 1-Sekunden-Takt sichtbar, d.h. Empfänger 2 eingeschaltet und gelegentliche, häufige Störungen des Zeittelegramms 31.

Betriebszustand 3:

Kreis 81 sichtbar, Indikator 82 aber weder dauernd noch für für 0,5 Sekunden noch im 1-Sekunden-Takt sichtbar, d.h. Empfänger 2 ausgeschaltet, letztes Zeittelegramm deutlich gestört, Übernahme des Zeittelegramms in die zeithaltende Schaltung 7 nicht erfolgt.

Betriebszustand 4:

weder Kreis 81 noch Indikator 82 in irgendeiner Form sichtbar, d.h. Empfänger 2 ausgeschaltet, letztes Zeittelegramm wurde als gefiltertes Zeittelegramm 32 in die zeithaltende Schaltung 7 übernommen, und - sofern notwendig - die die Zeitanzeige (nicht dargestellt) auf der Anzeigeeinheit 8 wurde berichtigt.

As can be seen from FIG. 1, a further optical signal in the form of a circle 81 can be made visible on the display unit 8. The visualization is again carried out by the control unit 6 in such a way that the circuit 81 is made visible both when the receiver 2 is switched on and when the last time telegram 31 was relatively severely disturbed before the receiver 2 was switched off and therefore the control signal 33 has occurred relatively frequently. In this way, the following operating states of the radio clock can be indicated by the optical indicator 82 in connection with the circle 81:

Operating state 1:

Circle 81 visible and indicator 82 permanently visible, ie receiver 2 switched on, disappearing control signal, so good reception conditions.

Operating state 2:

Circle 81 visible, but indicator 82 always visible for 0.5 seconds or every 1 second, ie receiver 2 switched on and occasional, frequent disturbances of the time telegram 31.

Operating state 3:

Circle 81 visible, but indicator 82 is neither permanent nor visible for 0.5 seconds or every 1 second, ie receiver 2 switched off, last time telegram clearly disturbed, time telegram was not adopted in time-keeping circuit 7.

Operating state 4:

neither circle 81 nor indicator 82 is visible in any form, ie receiver 2 is switched off, the last time telegram was transferred to the time-keeping circuit 7 as a filtered time telegram 32, and - if necessary - the time display (not shown) on the display unit 8 was corrected.

Claims (10)

Radio clock with a receiver (2) that receives a so-called time telegram consisting of serial digital pulses, with a decoder (5) connected downstream of the receiver (2) that determines the current time from the time telegram and feeds it to a control unit (6) that in turn transmits the current time to the time register of a time-keeping circuit (7) which autonomously advances the time register until the next receipt of a time telegram, the time currently contained in the time register being output on a display unit (8) and with an indicator for the reception conditions at the chosen location,
characterized,
that between the receiver (2) and decoder (5) a filter unit (4) is connected which, when the receiver (2) is switched on, a filtered time telegram (32) obtained from the individual pulses of the time telegram based on the analysis of typical reception interference, and as Indicator for the reception conditions at the selected installation site also generates a digital control signal (33) which does not occur in the case of undisturbed pulses, but occurs at least once when a disturbed pulse is received and is made recognizable to the user of the radio clock. Radio clock according to claim 1,
characterized,
that the filter (4) has an N-bit shift register (42), the input (31) of which the received time telegram is fed and which is periodically clocked by an oscillator (41), that the N outputs of the shift register (42) each with an address input of a read-only memory (43) are connected, which has three outputs, of which two outputs are connected to the two inputs (R, S) of an RS flip-flop and the third output emits the control signal (33) and that at the output of the RS flip -Flops (44) the filtered time telegram (32) is delivered. Radio clock according to claim 2,
characterized,
that the shift register (42) is 4-stage and that the read-only memory (43) has four address inputs (A1, A2, A3, A4) and has a memory volume of 16 times 3 bits, each of which 2 bits (D1, D2) are assigned to the two inputs (R, S) of the RS flip-flop (44) and the third bit (D3) represents the control signal (33). Radio clock according to claim 3,
characterized,
that between the address inputs (A1, A2, A3, A4) of the read-only memory (43) and its memory space occupancy, the link shown in Fig. 4 exists that the first (Q₁) or second (Q₂) or third (Q₃) or fourth (Q₄) output of the shift register (31) is connected to the first (A1) or second (A2) or third (A3) or fourth (A4) address input of the read-only memory (43), the first output of which (D1) is connected to the set input (5) and its second output (D2) is connected to the reset input (R) and that the control signal (33) is emitted at its third output (D3). Radio clock according to claim 1,
characterized,
that also a signal inverse to the control signal (33) is supplied to the control unit (6) and is made visible by it on the display panel (8) by means of an optical indicator (82). Radio clock according to claim 5,
characterized,
that the control unit (6) nevertheless makes the indicator (82) visible for this period in the event that a control signal (33) lasts less than a predeterminable period of time, for example 0.5 seconds, and in the event that the control signal ( 33) occurs relatively frequently, the indicator (82) makes it visible periodically at one-second intervals with a pulse duration of 0.5 seconds. Radio clock according to claim 6,
characterized,
that a further optical signal (81) is activated by the control unit (6) on the display unit (8) in addition to the optical indicator (82) when the receiver (2) is switched on. Radio clock according to claim 7,
characterized,
that the further optical signal (81) in the event that a correctly decodable filtered time telegram (32) could not be generated during a predetermined switch-on time of the receiver (2) remains activated even after the receiver (2) is switched off, while the control signal ( 33) inverse signal is then no longer made visible. Radio clock according to claim 7,
characterized,
that the optical indicator has the shape of a so-called magic eye (82) and that the further optical signal is made visible in the form of a circle (81) surrounding the magic eye. Radio clock according to claim 2,
characterized,
that the function of all components (41, 42, 43 and 44) of the filter (4) can be realized by a customer-specific integrated circuit or by a microcontroller.

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