EP1241814A1 - RDS-TMC Broadcast Receiver and Method for Calibrating an Internal Clock of a Broadcast Receiver - Google Patents

Abstract

The method for calibrating the internal clock of a radio receiver that is designed to receive and evaluate an external time signal received at regular intervals. The internal clock is used to measure a time interval between the receipt of two external time signals, the measured time interval is compared with the expected time interval and a calibration factor is determined for the internal clock which is then used to calibrate the internal clock. An independent claim is made for a radio receiver in which the internal clock is calibrated using an external RDS radio time signal (CT).

Description

The invention relates to a method for calibrating an internal timer in a radio receiver that is used to receive and evaluate at intervals received external time data signals is designed. Furthermore concerns the invention a radio receiver for the reception of RDS-TMC data, one tuner, one RDS decoder connected to the tuner, one Has timer and a central control unit that works with the RDS decoder is connected, wherein the timer from the central control unit with RDS time data signals can be synchronized and by the control unit Inclusion of the timer signal time window can be set, within which the radio receiver is ready to receive RDS-TMC data.

Corresponding radio receivers are known and are offered commercially. With the introduction of the Radio Data System (RDS), the Functionality of radio receivers and in particular car radios can be increased significantly. RDS is a standardized one Procedure for transferring data from broadcasters to one Radio receiver. The transmitted data includes, for example, information about alternative frequencies (AF), the name of the broadcaster (PS), the program type (PTY), the marking of a traffic announcement (TA) or the transmission of a date and time coding (CT). The RDS standard is laid down in the international standard IEC 62106.

A further development of RDS is the so-called RDS-TMC (TMC: Traffic Message Channel), with the traffic reports in coded form from a Broadcasters can be transmitted to a radio receiver. The The RDS-TMC standard is among others in the European pre-standard ENV 12313-1.

An RDS-TMC radio receiver must perform various functions which includes in particular the search for alternative frequencies. For this the tuner of the radio receiver must briefly switch to these alternatives Frequencies are set to check the reception quality. At the same time, however, it must be ensured that during these switching phases missed any traffic reports on another frequency become. This can be done in particular through the so-called RDS-TMC enhanced mode be achieved in the aforementioned RDS-TMC standard is described in more detail. For this purpose, the standard mentioned provides that the Transmission of traffic information only within a defined time window he follows. By correspondingly synchronizing these time windows with the test procedures the desired goal can be achieved at alternative frequencies. In TMC enhanced mode, every minute is converted into an integer number of Time ranges disassembled. Each of these time periods is again divided into sub-areas divided in which traffic reports broadcast or not broadcast become. In the time periods in which no traffic reports are transmitted can then be switched to alternative transmission frequencies for a short time be performed.

To take full advantage of the TMC enhanced mode, is a very accurate internal timer required in the broadcast receiver. By the time and date coding (CT) transmitted with the RDS signal can synchronization of the internal clock with the CT signal can be achieved. There however, the CT signal is only transmitted at specified time intervals in the meantime the time setting and thus the setting of the individual Time ranges for receiving traffic messages from the internal only Timer dependent. Especially with car radios that are within a relative wide temperature range can be operated by an inaccurate Timers Time deviations occur due to the traffic information data be missed.

This is where the invention comes in, which initially made it its task a method for calibrating the internal timer in a radio receiver specify. A second object of the invention is a Method for receiving RDS-TMC data with a radio receiver to indicate that a higher reliability when receiving coded TMC traffic data can be expected in the so-called TMC enhanced mode. A third task is ultimately a radio receiver for the Specify receipt of RDS-TMC data that work in TMC enhanced mode can and in which it is ensured that that of the radio receiver set time window with high accuracy with the standard or match the time slots set by the radio broadcaster.

The first-mentioned object is achieved by a method for calibrating a internal timer in a radio receiver that is used to receive and for evaluating external time data signals received at intervals is designed, with the aid of the timer a first duration value between the reception of two time data signals is determined and the first duration value is compared with an expected duration value from the comparison a calibration factor is determined for the internal timer and the internal one Timer is calibrated with the calibration factor.

The time data signal received at intervals is in particular the RDS-CT signal of an RDS data transmitter with which a date and Time coding is transmitted. This CT signal is from the broadcasters sent periodically, according to the currently applicable standard a minute cycle is provided. In the method according to the invention is now initially provided a first duration value based on the internal timer signal of the radio receiver to be determined, the first duration value the time between reception as measured by the timer of two CT signals. The duration value thus determined is now compared to an expected duration value, whereby the deviation of the internal timer can be determined from the external time data signals. These external time data signals (CT signals) are decisive for the classification the time window for receiving TMC messages. About the described A calibration factor for the internal timer is determined for comparison and the internal timer is calibrated with this calibration factor. This ensures that even in the period between receipt of two external CT signals the internal timer with the time specifications of the RDS station is correlated. The internal timer is advantageously added periodically synchronized with the external CT signal.

In particular, the expected duration value can be the difference between the two received CT time codes can be determined. In an alternative embodiment However, the expected duration value can be a saved one Act worth.

In a first embodiment it is provided that two immediately following one another Time data signals (CT signals) for determining the calibration factor be used. This embodiment is particularly simple feasible because two consecutive time data signals are used directly come. A certain disadvantage, however, is that the length of time between two consecutive CT signals with a minute relatively low is. This limits the accuracy of the calibration factor determined. In another embodiment, two are therefore not immediately provided successive time data signals for determining the calibration factor to use. This allows a longer period for determining the Calibration factor selected and thus its accuracy can be increased. Here, you can choose freely in steps of one minute the duration of the time measurement for determining the calibration factor should be done. The determination of the calibration factor is general the more precise the longer the underlying period is.

In a further embodiment it is provided that the calibration factor periodically determined anew. In extreme cases, any time between two successive CT signals to determine a new calibration factor be used. In practical cases, however, this is usually the case not be necessary as changes in the accuracy of the internal timer, for example due to temperature changes, rather slowly respectively.

The second object is achieved by a method for receiving RDS-TMC data with a radio receiver that has a tuner, one with the RDS decoder connected to the tuner, a timer and a central control unit has RDS-TMC data from the RDS decoder and periodically Contains time data signals with which the timer from the central control unit is synchronized, with the control unit including the Timing signal time window are set, within which the radio receiver is ready to receive new RDS-TMC data, according to the invention the timer is additionally calibrated with the help of the time data signals becomes.

The third task is performed by a generic radio receiver solved, according to the invention means for calibrating the timer with the help which contains RDS time data signals. The calibration of the timer can be carried out in particular according to the aforementioned methods. Preferably the radio receiver has at least two tuners, so that a tuner for receiving TMC data and testing alternative transmission frequencies can be used while another tuner for the Reception of the radio program is provided. Thus short-term Interruptions in radio reception to check alternative frequencies avoided.

Figur 1

ein Blockschaltbild eines Rundfunkempfängers mit zwei Tunern

Figur 2

die zur Durchführung des erfindungsgemäßen Verfahrens wesentlichen Komponenten eines Rundfunkempfängers

Figur 3

ein Verfahrensablauf zur Bestimmung des Kalibrierungsfaktors

Figur 4

ein Verfahrensablauf zur Kalibrierung des internen Taktgebers

Figur 5

ein Zeitdiagramm im TMC-Enhanced-Mode

The invention is described below with reference to an embodiment and the drawing. Show it:

Figure 1

a block diagram of a radio receiver with two tuners

Figure 2

the components of a radio receiver essential for carrying out the method according to the invention

Figure 3

a procedure for determining the calibration factor

Figure 4

a procedure for calibrating the internal clock

Figure 5

a timing diagram in TMC enhanced mode

Figure 1 shows a simplified block diagram of a radio receiver, in particular a car radio, with two tuners, namely an audio tuner 1 and a data tuner 2. The tuners 1, 2 receive their input signals from an antenna 3. Both tuners 1, 2 each generate a multiplex signal MPX. The MPX signal of the data tuner 2 is fed to an RDS decoder 5. The module referred to here as the RDS decoder 5 can in particular be a known one Pre-processor, for example of the type SAA6588, the other Takes on tasks. The output signal of the audio tuner 1 becomes one Sound processor 6 fed, which also receives input signals from other audio sources such as a CD player, a cassette player or a phone. The audio signals generated by the sound processor 6 are fed to an amplifier 7, which amplifies them to speakers 8 passes through which the audio signals are output.

The output signals of the RDS decoder 5 are a central control unit 9 fed, which takes over the preparation of the RDS information. The Control unit 9 is also with input / output units, not shown (e.g. keyboard, display) connected. Such a radio receiver is known and the individual components can be built with standard components.

The data tuner 2 can also be accommodated in a separate additional device be, for example, acquired as a retrofit device and with the actual Car radio (for audio operation), which itself has the audio tuner 1, connected becomes. Such an additional device with data tuner 2 is thus also a radio receiver, in which the calibration of an internal timer is carried out can be.

The method according to the invention and the method according to the invention are described below Radio receiver essentially in connection with a data tuner 2 explained. With a radio receiver with only one tuner, the then only tuner in particular will work as data tuner 2 if no audio playback or another audio source (CD, cassette or the like) is played. The only tuner can then run all functions described below can be used like the data tuner 2 of the two-tuner receiver according to FIG. 1.

FIG. 2 shows the data tuner 2, the RDS decoder 5 and the central control unit 9 shown in more detail. The signal received by the antenna 3 is the data tuner 2, which supplies the RDS decoder 5 with the multiplex signal MPX supplied. From the RDS decoder 5 an RDS clock signal and RDS data signals of an input / output interface 10 of the central control unit 9 fed. The input / output interface 10 is with a CPU 11 connected. The CPU 11 thus receives the RDS data and can evaluate it. The RDS data supplied to the CPU 11 includes the CT signal, which contains a date and time coding, especially every minute Will be received.

The CPU 11 has a working memory 12 and a permanent memory 13 connected. Furthermore, the CPU 11 is connected to a timer register 14, which in turn receives signals from an oscillator 15. The oscillator 15 forms with parts of the central control unit 9 an internal timer. To do this the periodic clock signals of the oscillator 15 in the timer register 14 stored and can by the CPU 11 according to a predetermined algorithm can be converted into time signals. The method according to the invention is essentially in the form of a program in the central control unit implemented.

FIG. 3 shows a process sequence for determining the calibration factor within the inventive method. The program sequence starts in Step S1. In step S2 it is subsequently checked whether an RDS-CT signal is received which contains the time and date coding according to the RDS standard. If this is not the case, a waiting loop is run through in step S3. If an RDS-CT signal was received, then in step S4 internal timer register 14, which is connected to the internal oscillator 15, read out and the read out value is stored in the working memory 12. It is then checked again in step S5 whether another RDS-CT signal was received. If this is not the case, then step S6 in turn to be on hold. If another RDS-CT signal is received, the current value of the timer register 14 is read out in step S7 and stored in the working memory 12. Then in step S8 timer register value previously stored in the working memory in step S4.

In step S9 is read from the two in steps S4 and S7 Timer register values formed a difference that is a first duration value represents. This first time duration value corresponds to the time duration between two received RDS-CT signals as determined by the internal timer has been. In step S10, the expected duration value is then between the reception of the two RDS-CT signals in steps S2 and S5. For this purpose, a fixed, predetermined value for the duration between two received RDS-CT signals of one minute or a multiple of one minute or this expected value can be taken directly from the received RDS-CT signals are calculated in accordance with steps S2 and S5, if these are also stored in the working memory.

In step S11, the calibration factor is determined by dividing the in Step S9 determined duration value and the expected in step S10 expected Duration value is made. This results in a calibration factor which is stored in the working memory 12.

FIG. 4 shows the procedure for calibrating the internal timer. The method starts in step S20. Then the current one in step S21 The value of the timer register 14 is read out and stored in the working memory 12. Then, the read-out timer value becomes in step S22 using a predefined conversion formula in hours, minutes and seconds converted. In step S23, the method described in FIG. 3 is used certain calibration factor is read from the working memory 12 and the time determined in step S22 is corrected with the calibration factor. This makes a high regardless of the accuracy of the oscillator 15 Accuracy of the internally determined time reached. In particular, the internally determined Time always correlated with the time according to the RDS-CT signal, even if this is not received.

The method according to the invention is used to calibrate the internal one Timer in particular for procedures or radio receivers for Receiving RDS-TMC data in the so-called TMC enhanced mode. In enhanced mode becomes the length of time between the receipt of two CT signals CT1 or CT2, which corresponds to one minute, are divided into equally long time segments. In the example shown in FIG. 3a, six time segments A, B, C, D, E and F are provided. Each of these periods is in turn in subsections Ta and Tw divided, which a delay section Td may be preceded (Fig. 3b). All transmitted according to the TMC standard Traffic information should start within a time period Ta. she can, however, be ended outside the time period Ta.

If there is no traffic data at the beginning of time period Tw, this has not been done the transmission of traffic data ends within the time period Tw, so you can then until the beginning of the new period Ta in the period B alternative transmission frequencies can be checked without the danger there is traffic data to be missed. Other functions within Tw A search run can also be carried out via the entire FM frequency band, one not restricted to one transmitter chain Search for traffic information ("customer TA") and the like.

From the time sequences shown it can be seen that the beginning of the time period Ta in the radio receiver must be determined very precisely. This requires high precision of the radio receiver's internal timer, which is achieved with the method according to the invention, which is permanent Ensure correlation of the internal timer with the external RDS time code.

Claims (17)

Method for calibrating an internal timer in a radio receiver, which is designed for receiving and evaluating external time data signals received at intervals, wherein a first time duration value between the reception of two time data signals is determined on the basis of the timer and the first duration value is compared with an expected duration value, a calibration factor for the internal timer is determined from the comparison and the internal timer is calibrated with the calibration factor. A method according to claim 1, characterized in that the expected duration value is determined from two external time data signals. Method according to claim 1 or 2, characterized in that the internal timer is additionally periodically synchronized with the external time data signal. Method according to one of the preceding claims, characterized in that the time data signal received at intervals is the RDS-CT signal of an RDS data transmitter. Method according to one of the preceding claims, characterized in that the time data signal is received periodically, in particular every minute. Method according to one of the preceding claims, characterized in that two immediately successive time data signals are used to determine the calibration factor. Method according to one of the preceding claims, characterized in that two non-immediately successive time data signals are used to determine the calibration factor. Method according to one of the preceding claims, characterized in that the calibration factor is periodically determined anew. Method according to one of the preceding claims, characterized in that the radio receiver receives and evaluates RDS-TMC data. Method according to one of the preceding claims, characterized in that the radio receiver has at least two tuners, one of the tuners being provided for receiving RDS-TMC data and for checking reception quality on alternative reception frequencies. Method according to one of the preceding claims, characterized in that, with the aid of the calibrated timer, time windows are defined within which the tuner provided for the reception of RDS-TMC data is kept ready for the reception of new RDS-TMC data. Method for receiving RDS-TMC data with a radio receiver which has a tuner, an RDS decoder connected to the tuner, a timer and a central control unit which receives RDS-TMC data and periodic time data signals from the RDS decoder, with which the timer is synchronized by the central control unit, with the control unit, including the timer signal, defining time windows within which the radio receiver is ready to receive new RDS-TMC data, characterized in that the timer is additionally assisted by the time data signals is calibrated. Radio receiver for receiving RDS-TMC data, which has a tuner (2), an RDS decoder (5) connected to the tuner (2), a timer and a central control unit (9) connected to the RDS decoder (5) is connected, wherein the timer can be synchronized by the central control unit (9) with RDS time data signals (CT) and by the control unit (9), including the timer signal, time windows (Ta) can be set, within which the radio receiver can receive RDS-TMC data is ready, characterized in that the radio receiver contains means for calibrating the timer with the aid of the RDS time data signals (CT). Radio receiver according to claim 13, characterized in that the radio receiver has at least two tuners (1, 2). Radio receiver according to claim 14, characterized in that the first tuner (audio tuner 1) is provided for receiving a radio program and the second tuner (data tuner 2) for receiving RDS-TMC data and for checking reception quality on alternative reception frequencies , Radio receiver according to one of the preceding claims 14 or 15, characterized in that the second tuner (data tuner 2) is contained in a separate additional device. Radio receiver according to claim 13, characterized in that the radio receiver is designed as a separate additional device for a further radio receiver which contains an audio tuner (1).

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