EP0415132B1 - RDS broadcast receiver with device for automatically switching over to an alternative regional programme - Google Patents

Abstract

In the radio data system, transmitting stations having the same programme identify themselves by transmitting the same PI code. If the programme is regionalised at particular times of the day within one programme chain, the PI code should be switched over. However, there are transmitting stations which always radiate a regionalised PI code, even when they are transmitting a joint general programme at times via the individual transmitting stations. To avoid an additional operating control at the RDS receiver which can lead to operating errors, a mobile RDS receiving set is presented in which, when a regional programme chain is lost, the alternative frequencies stored from earlier receiving routines are examined to see whether another regional programme of the same transmitting station can be received which is then tuned in by preference and is accepted as part of a new programme chain. <IMAGE>

Description

The radio data system (RDS) is used to transmit additional information parallel to the broadcast radio program. A 57 kHz subcarrier is amplitude modulated in quadrature with a binary data stream and then impressed via frequency modulation of the main carrier wave. So-called PI codes (program identification codes) and AF codes (alternative frequencies codes) are transmitted, which allow the receiver to assign a transmitter frequency to a specific program chain and offer him alternative frequencies under which the same program can also be received. This is particularly important for mobile radio receivers because the reception conditions can change continuously due to a change of location.

Modern RDS car radios use the information transmitted to them to automatically switch to another reception frequency immediately and usually inaudibly for the device user if the reception conditions deteriorate, without interrupting the currently received program is created. While in the previous ARI traffic radio system, a driver had to continuously observe the corresponding signs on the motorway to find a frequency of the same program chain, he is now automatically provided with the same program over longer driving routes.

As is apparent from the specification of the radio data system, pr.EN 50 067 from October 1988, the PI code consists of a four-digit hexadecimal string, each HEX number being binary coded with 4 bits, so that the PI Code comprises a total of a sequence of 16 bits (see Fig. 2).

The first HEX number (bits 1 to 4) contains the country code, i.e. it indicates to which state sovereignty the sender is to be assigned.

The second HEX number (bits 5 to 8) defines the broadcast area, i.e. it differentiates between local, regional, supra-regional, national and international programs.

The third and fourth HEX numbers (bits 9 to 16) identify the different program groups, which are divided according to country.

For example, the PI code for the "Bayern 3" program chain in hexadecimal notation "D 323". This results in the bit sequence "1101 0011 0010 0011" in binary notation.

Broadcasters that broadcast regionalized programs at certain times of the day either switch the PI code of their regional broadcasting stations during this period, or the regional broadcasting stations continuously transmit a regionalized PI code, even if a nationwide program is broadcast jointly across all stations in the broadcasting chain. The program chain "NDR 1" (Norddeutscher Rundfunk, 1st program) can be used as an example for the second case. The broadcasting area of this broadcaster is divided into the federal states "Schleswig-Holstein", "Hamburg" and "Lower Saxony", which are supplied with different regional programs. The state area "Lower Saxony" is again divided into four regional areas with individual broadcasting area identifiers. The individual regional broadcasting area IDs within the PI codes are also broadcast if all stations of the NDR 1 have a common framework program, e.g. send out during the night.

As already mentioned, in addition to the PI code in the RDS signal, a list of alternative frequencies is also transmitted. After that predominantly in Germany applied method B, the overall AF list consists of a sequence of local sublists, each of which begins with a code for the number of AFs, followed by the frequency of the associated parent transmitter to which the local list applies, and then in pairs Blocks shows an alternative frequency alternating with the frequency of the mother transmitter. From the sequence of numbers in which the alternative frequency to the mother frequency appears, it can be seen whether the AF is to be assigned to a station of the same or a neighboring transmission region of the same broadcaster. With a decreasing sequence of numbers for the frequency transmission, the AF belongs to a neighboring area in which a different regional program is broadcast at least temporarily. In this way, it is possible to program a radio receiver in such a way that it ignores AFs from regional transmission regions of the same broadcaster in the case of regionalized PI codes, in order not to permit a constantly random change of program, especially in the border area between the different transmission regions.

Now, to stick to the above example, a driver on the journey from Flensburg to Osnabrück, ie when crossing the state areas "Schleswig-Holstein", "Hamburg" and "Lower Saxony", wants to run the framework program "NDR", which is broadcast jointly during the night 1 "received, there are not enough alternative frequencies available to him for a lightning-fast and therefore inaudible frequency change due to the regionality of the PI codes.

In order to remedy this deficiency, it is known in the prior art to provide a manually operated switch on the receiving device which optionally allows the transmission area identifier in the PI code (bits 5 to 8) to be evaluated or ignored. This switch is called the "regional switch".

If the regional switch has now been programmed to suppress the broadcasting area identifier, an indiscriminate program change will then occur in times of regionalized program broadcasting, especially when driving through the border area of the adjoining regional broadcasting areas. The radio listener is forced to switch the regional switch to recognize the transmission area code when the program is changed for the first time if he does not want to lose the regional program he was listening to. If he does not react quickly enough so that another program change has already taken place, the regional program originally received cannot be retrieved by operating the counter.

On the other hand, the problem arises in the case of regionalized program broadcasting and fixedly programmed transmission area identification of the receiving device that the radio reception can be accompanied by strong interference when traveling from a regional to an adjacent regional transmission area, since the receiver is worse because of it Reception conditions can no longer be matched to alternative frequencies of the previous transmission region, but the mother frequency received so far is not left due to a lack of replacement.

Furthermore, an RDS radio receiver is known from EP-A-0 305 172, which has electronic tuning, control and storage elements, as well as a device for assessing the reception quality, and which enables the reception of a regional program identified by PI code. If the reception conditions deteriorate, a change to an alternative frequency can be effected.

The present invention is therefore based on the object of specifying an RDS radio receiver, in particular an RDS car radio, in which the alternative frequencies stored from previous reception routines are examined to determine whether another regional program of the same broadcaster is being received if additional regional control elements are lost in the event of loss of a regional program chain can, which is then preferably set and accepted as part of a new program chain.

Another object of the invention is to automatically supply the user of a mobile RDS radio receiver with the originally selected program as long as the transmission conditions of the transmitter chain and the reception conditions at the reception location permit this.

Fig. 1

das Blockschaltbild für ein Ausführungsbeispiel des erfindungsgemäßen RDS-Rundfunkempfängers,

Fig. 2

das Strukturschema des PI-Codes,

Fig. 3

ein Flußdiagramm für den Steuerungsablauf beim Wechsel auf ein alternatives Regionalprogramm.

The invention is explained in more detail below with reference to the drawings. It shows

Fig. 1

the block diagram for an embodiment of the RDS radio receiver according to the invention,

Fig. 2

the structural scheme of the PI code,

Fig. 3

a flowchart for the control sequence when changing to an alternative regional program.

In a manner known per se, the RDS radio receiver shown in FIG. 1 contains a synthesizer tuner 1, an IF amplifier 2 for selectively amplifying and demodulating the intermediate frequency, a stereo decoder 3 for decoding the stereo multiplex signal and a stereo amplifier 4. The microprocessor 8 serves as the central control unit and also supplies the necessary tuning signal to the synthesizer tuner 1 for setting the transmitter. The reception quality is monitored with the level detector 10 and the multi-path detector 7. The level detector 10 takes the IF amplifier 2 according to the IF signal level to measure the signal field strength and converts it into a digital control signal for the microprocessor 8. The multipath detector 7 is fed with the demodulated MPX signal and also delivers a multipath reception digital control signal to the microprocessor 8. The analog / digital conversion of the control signals can also take place in the microprocessor, provided the processor is provided with corresponding converter inputs.

The RDS decoder 5 is also controlled with the demodulated multiplex signal. After a 57 kHz bandpass filtering, the quadrature-amplitude-modulated RDS signal is demodulated and the after A subsequent biphase and differential decoding of the digital data obtained for further processing is fed to the microprocessor 8.

In addition to the already mentioned PI code and AF code, the RDS signal includes also contain a so-called PS code (Program Service Name Code) (with the aid of which the name of the station received can be displayed alphanumerically. For this purpose, the microprocessor 8 delivers corresponding control signals to the display 11.

For all manual control functions, the microprocessor 8 receives the associated control commands from the control panel 12.

The microprocessor 8 has RAM 6 with several memory levels as working and additional memory. The EEPROM memory 9 serves as a non-volatile program memory, in the individual memory levels of which, in addition to the PI code and the PS code, for example up to 24 alternative frequencies per program can be stored for a spontaneous program call.

The data contained in the respective memory levels of the program memory 9 are copied into the working memory (first memory level of the RAM memory 6) by the microprocessor 8 when a specific program is called up. The AFs are then checked by briefly tuning the receiver in terms of field strength, multi-path reception, transmitter center, RDS transmission quality and PI code checked and sorted in order of their reception quality. Finally, the tuner 1 is tuned by the microprocessor 8 to the frequency with the highest field strength. Each time you switch to an alternative frequency due to deteriorating reception conditions, briefly tuning the receiver updates the quality rating and the ranking of the alternative frequencies again.

It is important that the PI code is also checked in each case, because during the reception of a program or in the period between the storage of a specific program in the program memory 9 and the retrieval of this program in the working memory 6 of the transmitters because of the broadcasting of a regional program in the corresponding one Receiving area may have switched the PI code. The main memory 6 must then be loaded via the microprocessor 8 with the new PI code, which now differs in the second digit of the hexadecimal sequence of numbers (see FIG. 2), with the PS code (transmitter name) and the AFs the RDS data received via wave propagation parallel to the radio program are adapted to the regionalization.

The program chain "Bayern 2" with the alphanumeric transmitter display "BAY 2" and the PI code "D 322" should be used as a fictitious example. During certain broadcast times, the program parts "BAY 2 NB" with the Split the PI code "D 422" for Lower Bavaria and "BAY 2 FR" with the PI code "D 522" for Franconia from the "Bayern 2" program chain. Although all broadcasting stations of "Bayern 2" continue to broadcast the same AF list, the sequence of numbers of the frequency information in the local sublists shows which AFs belong to areas with temporarily different programs. This makes it possible to remove these AFs from direct access when adapting the AF data in the working memory 6 to the regionalization.

In this case, the working memory 6 holds only AFs from the regional transmission area in the "local part" of the AF list for a rapid frequency change. The AFs in the program chain, which are subordinated in the "global part" of the AF list, are initially ignored.

If the microprocessor 8 determines via the multipath detector 7 and the level detector 10 that the reception quality is no longer sufficient, because the user of the mobile RDS receiver, for. B. leaves the regional broadcast area or moves in the border area to neighboring broadcast regions, he will initiate an automatic frequency change, as exemplified in the flow chart of FIG. 3.

In program step 1, the set transmitter is monitored for reception interference. If the reception quality drops below a certain minimum, the local part of the AF list in Working memory 6 removed the next-rank AF from the microprocessor 8 and checked for reception in step 3. If the minimum requirements are met, a comparison of the PI code with that of the mother frequency previously set follows in step 4. If the tests in steps 3 and 4 are negative, the program returns to step 2, ie the next AF that follows is taken from the local AF list. If the comparison in step 4 yielded a different PI code, the AF in step 5 is relegated from the local AF list to a part of the global AF list which is degraded as a subordinate. The search for a suitable AF continues until an alternative frequency worthy of receipt with exactly the same PI code is found, in which case the local AF list is reevaluated in step 6, or until step 7 recognizes that all AFs on the local AF list have been tested unsuccessfully. In this case, the tuner 1 is tuned back to the original mother frequency in step 8 by the microprocessor 8, and a time counter is set to zero in step 10, it being ensured in step 9 that the time counter is only reset during the first run within one Frequency change routine takes place.

As long as the time t has not reached a certain time limit t 1, the program path leads back to the starting point (step 1) via step 11, ie further frequency change attempts are made.

After the time t 1, all AFs stored outside the local AF list in the working memory 6 are checked for reception in step 12 and their PI codes are evaluated. If there is an AF with exactly the same PI code compared to the previous mother frequency, it can be assumed that the local AF list was not complete. This frequency is then fixed in step 14 with the old PI code. If the microprocessor 8 only recognizes differing PI codes in step 13, then in step 15 a search is made for PI codes of regionally adjacent broadcasting stations of the same broadcaster. In step 16, the regional chain with the highest field strength is selected and the non-associated AFs are sorted out from the local AF list.

If the microprocessor 8 did not find any regionalized PI code of the same broadcaster while testing the entire AF list in step 15, an automatic RDS search over the entire reception area is started in step 17. The microprocessor 8 stores the RDS transmitter frequencies tested for reception quality and PI code in a second memory level of the RAM memory 6 and selects the frequency with the highest field strength for transfer to the main memory (first memory level of the RAM memory 6). When selecting, frequencies whose PI code, with the exception of the transmission range identifier, are assigned the PI code of the previous reception frequency matches, preferred. If the microprocessor 8 recognizes in step 18 that no RDS station worth receiving has been found, then returning to step 17, the search is repeated until an RDS station with sufficient quality characteristics is recognized by changed reception conditions.

In step 19, the microprocessor 8 tunes the tuner 1 to the new mother frequency obtained from steps 6, 14, 16 or 18. The program then returns to step 1 and initiates the same frequency change routine described above in the event of another reception disturbance.

For the program sequence shown, it was initially assumed that the reception conditions deteriorate during reception. The same logical sequence for the selection of alternative frequencies also takes place when a station is called up, ie when a station button on the receiving device is pressed. As already mentioned, the data contained in the program memory 9 are copied into the main memory 6 and all AFs are checked for reception quality and PI code. If, due to temporary regionalization, the PI code in the selected transmission area has changed compared to the state at the time the program was saved, the same priority requirements apply to the selection of alternative frequencies.

From the foregoing description it is apparent that the RDS receiving device tries to maintain an originally selected program as long as an alternative frequency that is worth receiving is available. Only then does it look for a frequency of a neighboring broadcast region of the same broadcaster. A change to a frequency of a different type of program chain only takes place if neither the mother frequency nor the associated AFs are recognized as RDS transmitter signals within a set period of time, or if no AFs can be set over a longer period due to poor reception quality and the mother frequency is already severely disturbed, although the parent transmitter is just identified as an RDS transmitter.

Claims (1)

1. RDS radio receiver, in particular RDS car radio, having electronic tuning, control and memory elements for the reception of regional stations which are identified by PI code, and having a device for evaluating the reception quality and whose output signal brings about automatic changing to an alternative frequency when the reception conditions become poorer, characterized in that the RDS radio receiver is designed in such a way that, in the case of the reception of a regional station which is identified by PI code, for which regional station no other frequencies which are suitable for reception are available under the same PI code, the other stored alternative frequencies of the same group of stations are successively briefly tuned to, a different regional station with the best deviating regional code of the same group of stations which can be received is selected and the said station is then preferably tuned to and accepted as the new group of regional stations, and in that the respective alternative frequencies, which can be received, of the new regional group of stations are ranked in the memory according to their suitability for reception.

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