EP0433904B1 - RDS broadcast receiver with a device for preferential reception of programs with the same country code - Google Patents

Abstract

The RDS broadcast receiver described starts an automatic station-finding run for a new program chain if no further alternative frequencies of the program previously received are available to it which are suitable for reception when there is a deterioration in the conditions of reception. To avoid the receiving set adjusting itself to a program chain of the neighbouring country in mobile use in the area of the border to a foreign-language neighbouring country because its quality of reception is found to be particularly good, a device is provided with which the receiver preferably only searches for transmitters suitable for reception, the country code of which corresponds to that of the transmitter previously received. Transmitters with deviating country code are also accepted only after the entire receiving range has been searched without success. <IMAGE>

Description

With the radio data system (RDS), a binary data stream is transmitted inaudibly for the radio listener parallel to the broadcast radio program, which provides the receiver with a range of tuning, switching and operating information. Among other things, so-called PI codes (Program Identification Codes) and AF codes (Alternative Frequency Codes) are sent continuously as a tuning aid, which allow the receiver to assign a transmitter frequency to a specific program chain and offer him alternative frequencies with which the same program can be received. Furthermore, the device can use the so-called TP code (Traffic Program Code) to recognize which stations transmit traffic messages, and it receives a switching signal with the TA code (Traffic Announcement Code), with the help of which it can be used, for B. during the playback of a music cassette or on hold with the radio program suppressed, a traffic message can be given primarily through the loudspeakers.

A deterioration in the reception conditions, especially in the case of mobile radio reception, can be eliminated by the receiving device by switching to an alternative frequency at lightning speed, so that the radio receiver can follow the current program practically without interruption. This rapid change to an alternate frequency naturally presupposes that at least one alternative frequency with sufficient reception quality is available. If this is not the case (either because there is no alternative frequency for a local broadcaster; or because the vehicle equipped with a car radio leaves a limited transmission area so that the alternative frequencies are no longer receivable), von Manually or automatically to search for a new program chain with sufficient reception quality. This is particularly important if you expect the latest traffic announcements while playing a music cassette or while the receiving device is waiting while the radio program is muted.

In this case, EFA 0 326 746 A2 suggests that the device user be warned of the loss of the program chain by means of a warning signal so that he can manually select another transmitter station. However, this type of information was also common for car radios for the ARI system (driver broadcasting information), which is disclosed in the "Grundig Technical Information" 4 / 5-1980, page 255.

According to the prior art, as described for example in EPA 0 326 747 A2, it is also known to start an automatic station search if a previously selected program can no longer be received via the alternative frequencies. This has the disadvantage, however, that in areas of contiguous nation states, the receiving device will adjust to a program chain of the neighboring country if its reception quality is rated higher than that of a domestic program. However, this is usually not desirable, especially with foreign-language neighboring countries, as long as a program from the home country can still be received with sufficient reception quality.

The present invention is therefore based on the object of creating an RDS radio receiver, in particular an RDS car radio, which, in the event of a deterioration in the reception conditions, initially only searches for stations with the same country code and only then accepts a program from the neighboring country when the search is started remains unsuccessful after a home station. Depending on the programming of the device, the station search can only be limited to traffic information stations or include all RDS stations.

Furthermore, the receiving device should optionally be programmable via a switch in such a way that, after an automatic search, it only transmits frequencies with the country code received before the search started RAM takes over. During the search, the power amplifier of the device should be muted and the mute should only be deactivated when a program with sufficient reception quality is received again.

Fig. 1

das Strukturschema des PI-Codes

Fig. 2

das Blockschaltbild für ein Ausführungsbeispiel des erfindungsgemäßen RDS-Rundfunkempfängers

Fig. 3

ein Flußdiagramm für den Steuerungsablauf beim Wechsel auf eine andere Empfangsfrequenz.

The invention is explained below with reference to the drawings. It shows:

Fig. 1

the structural scheme of the PI code

Fig. 2

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

Fig. 3

a flowchart for the control sequence when changing to a different reception frequency.

As from the specification of the radio data system, pr. EN 50 067 from October 1988, the PI code consists of a four-digit hexadecimal character string, each HEX number being binary coded with 4 bits, so that the PI code comprises a total of 16 bits (see Fig. 1).

The first HEX number (bits 1 to 4) contains the country code, ie it indicates the state sovereignty to which the transmitter 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 various program groups that are allocated to the federal states.

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.

The RDS radio receiver shown in FIG. 2 contains, in a manner known per se, 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 output stage 4. The microprocessor 9, which also supplies the necessary tuning signal to the synthesizer tuner 1 for setting the transmitter, serves as the central control unit, connected to the control unit 12. The reception quality is monitored with the level detector 5 and the multi-path detector 6. The level detector 5 takes a measured variable from the IF amplifier 2 in accordance with the IF signal level to determine the signal field strength, while the multipath detector 6 has high-frequency interference amplitudes in the multiplex signal, caused by multipath reception, evaluates. The analog / digital conversion of the control signals for the microprocessor 9 takes place either in the two detectors 5, 6 or in the microprocessor 9, provided that it is provided with corresponding converter inputs. The RDS decoder 7 is also fed with the demodulated multiplex signal. After a 57 kHz bandpass filtering, the quadrature-amplitude-modulated RDS signal is demodulated and the digital data obtained after a subsequent biphase and differential decoding are fed to the microprocessor 9 for further processing.

The microprocessor 9 has the RAM 13 with several memory levels as working memory and additional memory. The operating program is stored in the ROM memory 14. The EEPROM memory 15 serves as a non-volatile program memory and contains in its individual memory levels for each stored program in addition to the PI code and the PS code (program service name code for displaying the name of a program chain) a number of selected alternative frequencies for one spontaneous program call.

The data contained in the respective memory level of the program memory 15 are transferred into the main memory (first memory level of the RAM memory 13) by the microprocessor 9 when a specific program is called up. Then the AFs are related by briefly tuning the receiver checked for field strength, multi-path reception, transmitter center, RDS transmission quality and PI code and sorted in order according to their reception quality. Finally, the tuner 1 is tuned by the microprocessor 9 to the frequency with the highest field strength.

In the further course, the microprocessor 9 determines via the level detector 5 and the multipath detector 6 that the reception quality is no longer sufficient because the user of the mobile RDS receiver e.g. leaving the broadcasting area of a program chain or moving in the border area to neighboring nation states, it will initiate an automatic frequency change, as exemplified in the flow chart of FIG. 3.

In program step 1, the set transmitter is continuously monitored for reception interference. If the reception quality drops below a certain minimum, the next-order AF of the AF list contained in the working memory (first memory level of the RAM memory 13) is removed by the microprocessor 9 in step 2 and checked in step 4 by briefly tuning the tuner 1 for reception worthiness. Before that, in step 3, the output stage 4 is muted by the microprocessor 9 via the electronic two-way switch 8.

If the minimum requirements for the reception quality are met, the PI code is compared in step 5 with that of the previously set one Mother frequency. If the tests in steps 4 or 5 are negative, the program returns to step 2, that is, the next following AF is taken from the AF list contained in the working memory 13 and the test cycle is continued until an alternative frequency that is worth receiving is included exactly the same PI code is found. In this case, the ranking of the alternative frequencies in the AF list of the working memory 13 is reevaluated in step 6.

If no alternative frequency with an identical PI code that is worth receiving is found and it is recognized in step 7 that all the alternative frequencies contained in the working memory 13 have been tested, in step 8 a search for RDS stations or for RDS traffic radio stations (depending on the device programming) is carried out via the entire reception frequency range started. A list of all the RDS stations found, sorted by PI code, is created in the second memory level of the RAM 13. Step 9 then checks whether RDS stations worth receiving have been found. If the result is negative, the search is repeated, returning to step 8; if the result is positive, the RDS stations found are evaluated with regard to their field strength and their country code and read from the station list. The check whether the country code of a reception frequency taken from the station list corresponds to the nationality of the station originally received is carried out in step 11.

As long as a different country code is determined, the program returns to step 10 via step 12 until the entire station list has been read out. From this point on, step 12 is followed by program step 13, in which it is asked whether only RDS stations with identical country codes are permitted. The question in program step 13 is decided by the position of the switch 10 symbolically represented in the block diagram, FIG. 2. If switch 10 is open (if the question in program step 13 is answered in the negative), then when the station list is read again, an RDS station with a different country code is also loaded from the microprocessor 9 into the main memory (first memory level of the RAM memory 13). If the switch 10 is closed, i.e. if only RDS stations with identical country codes are allowed, the program returns from step 13 to step 8, which triggers a new station search.

Program step 14 follows when step 6, 11 or 13 offers a new reception frequency for tuning tuner 1. This frequency is fixed together with the PI code as the new mother frequency in the main memory (first memory level of the RAM memory 13). As a result of program step 13, a new country code can also be defined as reference information for further station searches.

In step 15, the muting of the final stage 4 is finally canceled via the switching device 8. The program then returns to step 1 and initiates the same frequency change routine described above in the event of another reception disturbance.

From the preceding description it is apparent that the RDS receiving device in the event of deterioration in the reception quality with switch 10 open (synonymous with non-existent switch) initially only searches for RDS transmission frequencies which are broadcast with the same country code in the PI code. Only if the search is unsuccessful, even over the entire reception frequency range, is an RDS transmitter with a different country code accepted and recorded as a new mother transmitter in the working memory.

The output stage of the receiving device is muted until a program worth receiving is available again.

When switch 10 is closed, the search for alternative frequencies is limited only to transmitting stations with the same country code, which will be welcomed by a radio listener who often moves with his mobile receiving device along the border to a foreign-language neighboring country. If the limit is exceeded, he must then at least temporarily open switch 10 to adapt the receiving device to a new country code.

Claims (3)

1. RDS radio receiver, in particular RDS car radio, having electronic tuning and memory elements, having a device for assessing the reception quality and having a central control unit which initiates an automatic station search as soon as the programme currently received and its associated alternative frequencies are no longer receivable, characterized in that the central control unit (9) evaluates the country identification supplied by the RDS decoder (7) and contained in the PI code of the RDS data signal and, on comparing it with the country identification of the programme received before the start of the search, preferably transfers only receivable RDS reception frequencies having the same country identification to the working memory (13) and also stores programmes of the neighbouring country only after an unsuccessful search of the entire reception frequency range.
2. RDS radio receiver according to Claim 1, characterized in that a central control unit (9) is designed as a microprocessor and can be additionally programmed via a mechanical or an electronic switch (10) in such a way that, during an automatic search, only stations are selected which have the country identification received before the start of the search.
3. RDS radio receiver according to Claim 1 or 2, characterized in that, during the station search, the output stage (4) is muted by the central control unit (9) by means of a switching device (8) and in that said muting continues to be maintained until a programme having adequate reception quality can be received again.

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