NO173908B - PROCEDURE FOR TRANSFER AND / OR FOR RECEIVER SIDE USE OF DIGITAL INFORMATION IN A RADIO SIGNAL - Google Patents

Abstract

The transmission system provides digital data corresp. to an alternative frequency or programme information code, identifying the other frequencies providing the same radio programme. This information is obtained by short-term switching of the receiver to each alternative frequency with evaluation of the reception quality to allow switching from the tuned frequency when an improved signal is obtained. Pref. the reception quality is evaluated using the signal distortion on its own or in addition to the reception field intensity, with the bit error rate of the radio data signal used as the criteria for the signal distortion.

Description

The invention relates to a method according to the introduction to patent claim 1. The invention also relates to a method according to the introduction to patent claim 8. Furthermore, the invention also relates to a method according to the introduction to patent claim 11.

Procedures of the type indicated at the outset are, for example, described in the Technical Document Doc. Techn, No. 3244 to the European Broadcasting Union. With the radio data system (RDS) specified there, the transmission of additional information, e.g. transmission of alternative frequencies (AF code), in particular in the form of alternative frequencies summarized in a list, arranged as content of a data stream which is modulated on a 57 kHz auxiliary carrier wave. This information is of interest both for mobile reception (e.g. with car radios) - perhaps when you leave the radiation area of a transmitter - and for stationary reception - perhaps when a transmitter is lost or disturbed. With suitably designed receivers with storage, such lists can be stored, and thus the time for setting the receiver to the respective optimal frequency in this list (e.g. according to optimal reception conditions) can be reduced.

The RDS data signal also includes, among other things, so-called program identification information (PI code), whereby the alternative transmission frequencies on which the program signal for the instantaneous reception frequency can also be received can be determined directly with the help of the AF code and indirectly with the help of the PI code .

The utilization or assessment on the receiver side of the alternative transmission frequencies can take place in such a way that the receiver for each alternative frequency is tuned briefly and successively to the alternative frequencies. Then the reception field strengths for the alternative frequencies and the instantaneous reception frequency are compared with each other, whereby the frequency that delivers the highest measured reception field strength is selected and set as the new reception frequency (this can of course also be the previously set reception frequency).

Thereby, however, the problem arises that there are cases in which the measurement of the reception field strength - especially in the case of multi-path reception - does not give any reliable quality statement about the reception. In the case of multipath reception, the reception disturbances caused by signal intrusion depend on the detours, on the instantaneous signal equipment (which is determined by the type of program - for example classical music or pop music), and in the case of mobile reception depending on the vehicle speed. A reception signal that is disturbed due to multipath reception, despite a relatively high reception field strength between the signal intrusions, can subjectively be felt as exceptionally disturbing, while, on the other hand, a reception signal that is only disturbed by noise can be felt to be significantly better.

As a result, the mentioned selection of the best possible reception of a selected program signal can lead to the reception being permanently damaged due to multipath reception interference. This undesired result cannot be changed significantly by - possibly with the help of a second tuning circuit ("Tuner") in the receiver - being tuned to both the alternative frequencies over a longer measurement period and the measured reception field strengths being integrated, as the reception signals disturbed due to multi-path reception also with such an integration usually exhibits a higher average reception field strength than the reception signals which are only disturbed due to noise.

However, such disturbances can not only damage the program signal. The additional information, for example transmitted in the RDS data stream, may also be implicated, so that on the receiving side either long waiting times may occur until correctly received RDS information is available again, or misinterpretations may occur. This is generally particularly negative in connection with data whose repetition cycle in the data stream is relatively long.

A further problem with regard to program signal quality has its cause in the transmitter network structure in some countries, particularly in such countries which have mutually overlapping transmitter networks. When the digital information sent centrally from a parent transmitter, perhaps a list of alternative frequencies, sometimes does not suit the one per re 1-éto reception from the mother transmitter fed daughter transmitter (e.g. converter), those after the relay receiver had to be filtered out and replaced with the list suitable for the respective daughter transmitter. This filtering out and re-introduction is associated with increased costs. In addition, the quality of the program signal also deteriorates due to the filtering.

It has therefore already been proposed (DE-PS 3 432 848) to radiate a number of lists of alternative frequencies from all transmitters in a transmitter group, each of these lists at its beginning receiving the operating frequency of the transmitter assigned to the list in question, for from the series of lists to be able to choose the appropriate one in each case and to the recipient sends an optimized list.

A safe reception of such a series of lists, however, requires that the hereinafter referred to as "header" beginning of each list with the operating frequency of the transmitter assigned to the list in question is received correctly. If this is not the case, for example as a result of interference due to multipath reception, the receiving side cannot take advantage of the alternative frequencies that follow the header of each list, and then not even when it is received in the correct way, as it cannot correct assignment to the relevant operating frequency.

It has therefore also already been proposed (Firma Blaupunkt-Werke GmbH, Hildesheim) to transmit all alternative frequencies for a transmitter chain - which may consist of several transmitter groups (e.g. BR-North and BR-South) - in the form of a matrix, whereby the associated alternative frequencies for each transmitter are grouped as matrix neighbors within the matrix. However, this so-called "matrix method" has the disadvantage that frequencies which in reality are not alternative frequencies at all in the above-mentioned sense, as a result of the grouping regulation, can inevitably be neighbours, so that on the receiver side, correspondingly incorrect polling of such neighbors can occur. Moreover, the production and modification of a matrix is exceptionally complicated, so that a new assignment of a broadcast frequency that has become free would sometimes not be possible simply because an existing matrix does not allow such a change.

Against this background, the purpose of the invention is to improve the reception quality by a method of the type indicated at the outset.

According to the invention, this task is solved by means of the special features specified in patent claim 1. This task is also solved with the help of the special features specified in requirement 8. Furthermore, this task is also solved with the help of the special features specified in claim 11.

The invention is based on the recognition that, firstly, the reception quality can be improved by the alternative frequencies being transmitted in such a way that they can be more securely assigned to the respective transmitter operating frequencies on the receiving side. This has the advantage that, if necessary, the receiver can then be tuned more quickly to an alternative frequency that offers better reception. This even applies if the recipient were to show only a small storage capacity.

The invention is also further based on the realization that the reception quality can be improved by not using the reception field strength, or at least not exclusively the reception field strength, for the assessment of the reception quality, but instead acoustic distortions and/or program signal distortions. This has the advantage that such alternative frequencies, which only "apparently" - namely due to a higher reception field strength - offer a better reception, but in reality are felt by the user to be worse, can be rejected or discarded on the receiving end. If the additional data transmitted within the radio signal is available in the form of digital information, such as with the RDS data signal, the bit errors in the RDS data signal can be used as a measure of the program signal distortions. Namely, it has been shown that the bit errors in the RDS data signal are relatively accurately correlated with the program signal distortions, even if the program signal is transmitted in the baseband from 0 to 53 kHz and the RDS data signal is transmitted on a 57 kHz carrier wave with a minimum swing of ±1, 2 kHz.

Due to this correlation, one embodiment of the invention can exploit the circumstance that disturbances due to multipath reception or interference cause serially occurring bit errors in the RDS data signal, while, on the other hand, disturbances due to noise have uniformly distributed bit errors as a result. The degree of all disturbances can then be derived from the block failure frequency

which can be determined completely independently of the data content.

For an optimal selection of the frequency which enables the best instantaneous reception, a tuning circuit or tuner in the receiver is tuned successively at time intervals both to the alternative frequencies and to the set reception frequency. In the case of a somewhat more comfortable receiver design, in order to optimally select the frequency that enables the best, instantaneous reception, a second tuner is arranged in the receiver which, in intervals of at least 2 seconds, is successively tuned both to the alternative frequencies and to the set reception frequency for the first one agrees.

During these - in the case of the receiver design with two tuners relatively long - tuning intervals, the bit errors are determined for the total, received RDS data signal (which, in addition to the alternative frequencies, contains an abundance of additional information). Then, the bit error distributions and block error frequencies determined for each alternative frequency and for the instantaneous reception frequency are used in the following way: If all tested or controlled frequencies only show series-like or only evenly distributed bit errors, which means that at all frequencies there are reception signal disturbances due to multipath reception, interference* or noise, the associated block error frequencies are compared with each other, whereby the frequency with the smallest block error frequency is selected as the optimal reception frequency. The receiver's tuner - respectively the first tuner in the case of a receiver that has two tuners - is then tuned to this selected frequency, provided that the already set reception frequency is not identical to the selected frequency. ;In the event that the controlled frequencies exhibit different disturbances, i.e. both due to noise and bit errors caused by multipath reception, the frequencies which are essentially disturbed due to noise and not due to multipath reception, i.e. the frequencies which mainly show evenly distributed errors. In order to exclude highly noisy signals, such frequencies can only be selected if the maximum permissible block error frequency of the RDS data signal is not exceeded. The preselected frequencies are then compared with each other with respect to their established block error rate, whereby again the frequency with the lowest block error rate is selected as the optimal reception frequency. The above-mentioned selection of the optimal frequency can, with a sufficiently long measurement interval for each alternative transmission frequency, take place without taking into account the relevant reception field strength. Particularly at smaller measurement intervals, the reception field strength can also be used for the selection, whereby the trade-off between reception field strength on the one hand and signal distortions on the other hand can be established empirically. ;The alternative frequencies can be determined using the PI code or the AF code, or using and possibly supplementing - in case of ambiguities or incomplete transmission - with both codes. The PI code identifies frequencies on which the same program signal can be received. By means of a comparison of the PI code during the transmitter search run, an unambiguous allocation of the instantaneous reception frequency and its alternative frequencies can take place. This assignment can be found directly from the AF code. If the AF code is not transmitted in the RDS data signal or if the AF code is affected by errors, the alternative frequencies can therefore also be derived or is supplemented based on the PI code. With the help of the method according to the invention, it is for the first time, with the help of a concept of a completely new kind for determining the optimal reception quality, possible to realize the advantages sought with the introduction of the RDS system and the contained alternative frequencies with a constantly optimal reception for radio receivers (both for mobile and for stationary radio receivers). With the help of the RDS data signal, the problems with multipath reception of the utility signal can be surprisingly significantly reduced. ;In the order of individual lists, which are contained in the RDS data stream's digital information and which in turn contain alternative frequencies which are assigned to the relevant transmitters in a transmitter chain or are optimized for these relevant transmitters, it is in the method according to the invention' according to a further embodiment ensured that the operating frequency arranged in or for each list for the associated transmitter is transmitted not only at the beginning of the list, but also before each individual, alternative frequency of the relevant list, so that each alternative frequency is "addressed " with the operating frequency. Each list thus consists of a sequence of digital information blocks, each block consisting of two pieces of information. One of these pieces of information for each block is (with very special exceptions) the operating frequency of the transmitter assigned to the list in question. If therefore part of the list is transmitted or received incorrectly, the correctly received, alternative frequencies as a result of their pairing with the operating frequency can be unambiguously assigned to the corresponding transmitter and on the receiving side sorted into its list. Since it is unlikely that the same block of information is continuously disturbed in a considered list, the complete list can be stored on the receiving side from two or three consecutively received, disturbed lists for the same sender. The previously described pairing of each alternative frequency with the operating frequency of the transmitter assigned to the list increases the number of frequency information to be transmitted for each list to twice as much compared to the method according to DE-PS 3 432 848, so that the cycle duration for each order of lists is increased accordingly. One could therefore assume that the probability and security of reception will be degraded rather than improved by such an extended cycle duration. For the initially mentioned matrix method, the smaller cycle duration for a matrix in relation to a sequence of individual lists is in fact claimed as an advantage in relation to the list method according to DE-PS 3 432 848, and from this a higher reception reliability is derived. It must therefore be surprising to experts in the field that the reception reliability, despite the significant increase in the cycle duration of the sequence of lists transmitted according to the invention, is decisively higher than with the matrix method and with the species-matching list method. The unforeseeable reason for this surprising advantage consists in the fact that a secure assignment of the correctly received, alternative frequencies is still possible even in extremely poor reception conditions, as a result of the aforementioned addressing of each alternative frequency with the operating frequency. This is not the case with the other two methods, so that their shorter cycle duration is of no use in such reception situations. ;Further distinctive features, advantages and details of the invention shall be described in more detail below in connection with three exemplary embodiments with reference to the drawings, where fig. 1 shows a schematic representation of the sequence of lists with alternative frequencies radiated from each transmitter in a transmitter chain according to a first embodiment of the invention, fig. 2 shows a block diagram of a receiver for a method according to a second embodiment of the invention, and fig. 3 shows a block diagram of a receiver for a method according to a third exemplary embodiment of the invention. ; On fig. 1 schematically shows a system of alternative lists that are transmitted as additional information for a radio transmitter. In the example considered, it is assumed from a radio signal in which an auxiliary carrier wave of 57 kHz has been inserted. The auxiliary carrier wave can contain an amplitude modulation which has a traffic radio characteristic (Verkehrsfunkkennung) as content. As modulation or as additional modulation, a data signal coded in a specific way is imprinted on the auxiliary carrier wave, which is not of further interest here. This data signal is transmitted in a consistent form with the same program by all transmitters in a transmitter chain, for example by all transmitters in the transmitter chain "Bayern 3" in the coverage area of Bayerischer Rundfunk (abbreviated: BR). The correspondingly transmitted data signal contains, among other things, a number of lists with alternative frequencies for all transmitters in the transmitter chain, in the example shown the list for transmitter no. 1, the list for transmitter no. 2, the list for transmitter no. 3 up to the list for transmitter no. 29 for the case of a transmitter chain with 29 transmitters. Each list is specially tailored for the transmitter in question and contains the alternative frequencies arranged for this transmitter, i.e. the frequencies for the transmitter that can be received alternatively on the same program in the reception area of the transmitter in question. For example, the program "Bayern 3" in the Munich area can alternatively be received by the transmitter "Wendelstein" or by the transmitter "Ismaning". If the receiver is tuned to the Wendelstein transmitter, the receiver can, in the event of a reception error, e.g. as a result of multipath reception, due to his knowledge of the "alternative" Ismaning, briefly tune to the Ismaning transmitter and check its reception field strength. If the latter is better, it is switched to the transmitter Ismaning, whereby this test sequence is practically not audible to the listener. Each list consists of a sequence of digital information blocks as shown in fig. 1 is indicated as horizontal lines within the list. Each information block consists of a pair of information, as indicated by the vertical division of the list into a left and a right half. The first block in each list, designated as "header", contains in the left half of the block the number of alternative frequencies within the relevant list. In the case of the list for transmitter #1 with four alternative frequencies, the header contains the number #4, and in the case of the list for transmitter #29 with seven alternative frequencies, the header contains the number #7. In the right half block, the header of each list contains the operating frequency of the 'transmitter' assigned to the list. In the case of the list for transmitter #1 with the operating frequency of 98.5 MHz, the 98.5 MHz frequency information is contained in the right half of the header. In the case of the list for transmitter No. 29 with the operating frequency of 97.9 MHz, the frequency information "97.9 MHz" is transmitted in the header. ;So far, there is agreement with the method according to DE-PS 3 432 848. There, deti.de after the header text, two alternative frequencies are transmitted for each list, so that in the case of list no. 1 with four alternative frequencies, two alternative frequencies follow the header text blocks with 2<*>2=4 alternative frequencies.

In contrast to this, in the present embodiment according to the invention, in each block that follows the header, the operating frequency assigned to the list is transmitted, and then together with an alternative frequency. These pairs thus contain the operating frequency as an address for the alternative frequency in question, which has the already mentioned advantage that the reception security is drastically increased, even if the number of blocks required for each list that follows the header is doubled.

In the case of the list for transmitter no. 1, instead of two blocks, as according to DE-PS 3 432 848, four blocks must now be transferred after the header, which entails a corresponding increase in the transfer time for the series of 29 considered lists. As this transmission time is equal to the cycle duration for each series of lists, one could believe that the reception security in case of transmission disturbances deteriorates as a result of this extension of the cycle time. As already explained, however, this assumption is incorrect, so that one must note the surprising effect that the reception security of the method provided according to the invention according to this embodiment despite the extension of the cycle time is clearly increased in relation to the list method and the matrix method.

In the case of transmitters whose operating frequency is not in the 100 kHz grid, but in between (so-called offset frequencies), e.g. amounts to 92.85 MHz, the operating frequency is not transmitted in the header of the relevant list, but instead a special information, a so-called "filler code" ("Fillercode") according to the initially mentioned document from the European Broadcasting Union. In the following block, the offset frequency, e.g. "92.85 MHz" and then the "quasi-operating frequency", e.g. "92.8 MHz" transmitted. In the subsequent blocks, this quasi-operating frequency is first transmitted as an address for the alternative frequencies.

A further deviation from the transmission rule shown in the drawing for the individual lists occurs if one of the alternative frequencies is an offset frequency. In this case, the offset frequency of the alternative frequency is transmitted instead of the operating frequency in the corresponding block, and then together with the "quasi-alternative frequency" located in the 100 kHz grid.

For the identification of alternative frequencies for such transmitters which, within the framework of regional programs, are disconnected from the assigned transmitter chain for part of a broadcasting day or a broadcasting week, e.g. transmitters that from 6:00 a.m. to 12:00 p.m. transmits the program "Bayern 3", from From 12.00 to 1.30 p.m., the regional program "New from Swabia" broadcasts and from 13.30 to 24.00 the program "Bayern 3" again transmits, it may be advantageous to switch the order of operating frequency and alternative frequency in the assigned block, i.e. first to transmit the alternative frequency and then the address "operating frequency" in the block.

Each list is specially tailored to the transmitter in question and, in accordance with the agreement within the European Broadcasting Union, contains a maximum of 25 frequencies, but in the normal case considerably fewer. At the beginning of each list is the operating frequency for the corresponding transmitter, i.e. in the list for transmitter no. 1 the operating frequency for transmitter no. 1 is at the beginning, e.g. 98.5 MHz. As mentioned, the displayed series of 29 lists of each transmitter in the transmitter chain is transmitted as a data signal.

The receiver receives and decodes the transmitted data signal, i.e. the series of lists with alternative frequencies. To select the valid list for the currently polled transmitter from the list sequence received, the receiver only needs to compare the first frequency of each list with the current polling frequency, which even with 29 lists can be done in a very short time. This selection can take place either by on-line operation or by off-line operation, i.e. without or with interconnection of the received series of lists. In a preferred embodiment, the selected list is stored in each case.

When processing the received and possibly buffered series of lists, the receiver selects the list whose first frequency (equal to the operating frequency of the assigned transmitter) corresponds to the current polling frequency. If this first frequency for several lists matches the set operating frequency, all these lists must be selected. Only the selected list or the selected lists are used for the subsequent optimization of the vote.

This polling process takes place either by means of a corresponding command from the listener or automatically, when, for example, the currently received transmitter is no longer worthy of reception. During the voting process, the receiver is automatically tuned to the alternative frequencies listed in the selected list or lists, and selects the alternative frequency that offers the best possible reception. With the aid of the transmitted data signal RDS, rapid optimization of the tuning of mobile receivers can also be carried out in the case of transmitter chains with more than the specified maximum number of alternative frequencies, without filtering out and re-entering frequency lists at the location from daughter transmitters being necessary.

Fig. 2 shows a block diagram of a receiver for a method according to a second embodiment of the invention. It is thereby taken into account that on the basis of fig. 1 described system, although in the second embodiment it does not depend that the additional information is transmitted in digital form.

The broadcast or radio signals received with an antenna 1, which contain additional data, are supplied on the one hand to a tuner 2 and on the other hand to a tuner 3. The tuner 2 forms part of a radio receiver apparatus which comprises an intermediate frequency amplifier 4 for the intermediate frequency emitted from the tuner, a demodulator 5 for recovering the low-frequency signals, an amplifier 6 for the low-frequency signals, and a speaker 7 for the acoustic reproduction. To the signal path, e.g. on the output of the tuner 2, a connector 10 is connected for selecting the 57 kHz carrier wave, which is connected to a connector 11 for recovering the data. The data is supplied to a storage 12. In this storage 12, the alternative frequencies (AF) of the operating frequency transmitter received by the tuner 2 are constantly read. The tuner 3 serves for continuous scanning or sampling of the frequency range that can be received from the tuner 2. Its high- or medium-frequency output signals are likewise supplied to the storage 12. The frequencies scanned by the tuner 3 are constantly compared with the corresponding stored frequencies, in order to provide a measure for the transmitter which can currently be received best. The frequency to be set by the tuner 3 in each case is determined by the storage 12 by means of a microprocessor 13 over a line 14 and the tuner 3 is tuned accordingly.

A coupling 15 serves to measure the field strength of the transmitter received in each case. As soon as the field strength measurement shows that the signals from another transmitter have a greater field strength than the drif tsf frequency transmitter set by the tuner 2, the tuner 2 is switched over a wire 16 to the transmitter with the currently greater field strength.

With the connection described so far, it is possible that due to interferences, e.g. such as those caused by reflections, distortions of the acoustically reproduced sound signal occur. Such interference mostly occurs in the vicinity of very strong transmitters. Due to a large field strength at the momentary receiving location, an overshoot of the receiver can also occur, due to which the acoustic reproduction is distorted.

With known methods, for example according to DE-PS 3 448 043, after selection of a transmitter, a fully automatic vote is made possible without the user's participation on that transmitter with the same program that can be received best at the momentary receiver stand, i.e. delivers the largest field strength.

For this purpose, each transmitter will not only broadcast its own list, but in sequence will also broadcast the lists of all further transmitters in the same transmitter chain, whereby the operating frequencies for the individual transmitters in each case are at the beginning of the individual lists. The receiver can thus, after receiving all lists due to its momentary voting frequency, select the list that belongs to the currently set transmitter, the receiver comparing the voting frequency with the first frequency of each list within the list row. Furthermore, the receiver also recognizes the alternative frequencies on which, when it leaves the coverage area of the currently set transmitter, it can continue to receive the same program without having to try the alternative frequencies for the other lists. In this way, switching to another transmitter in the same transmitter chain can usually be carried out very quickly.

Precisely when receiving from transmitters with a large nearby field strength, however, the acoustic reproduction can be distorted. This can, for example, be due to an override as a result of excessively strong reception field strength, or to interference phenomena due to reflections.

In the present embodiment according to the invention, care has therefore been taken to enable a transmitter setting while maintaining the automatic switching to other transmitters that broadcast the same programme, whereby acoustic distortions during reproduction are largely avoided or reduced.

By means of a switch 17, a switching state is produced in the microprocessor 13 in which not the strongest transmitter, but a weaker transmitter, in particular the second strongest transmitter, is used for the comparison with the respective set operating frequency transmitter.

By further designing the switch 17 as a reset key, it is achieved that the setting of the device on transmitters with less than the instantaneous, greatest field strength can be canceled when the transmitter's near zone or disturbance zone is left. A repeated connection process is thus possible in an easier way. The effect of the switch 17 on the microprocessor 13 can also be designed so that all transmitters can be set one after the other with decreasing field strength by means of repeated, brief touches of switches 17 in accordance with the stored, alternative list. "With the help of a longer operation of the interrupter 17, e.g. over several seconds, can reset

ling sequence is triggered.

The tuner 3 can on fig. 2 have a different design than the tuner 2, as its real task is only to scan the frequency band for control of potentially stronger transmitters. A signal quality must therefore not be achieved.

When using only one tuner, it is also possible to carry out a field strength switching in the described form, as it is true that transmitters with smaller field strengths can be received by the user during the interrogation process.

Fig. 3 shows, in a third embodiment of the invention, a modification of the one in fig. 2 showed a connection in which two equal tuners 2 and 3 are connected to two separate amplifier trains A, B which each supply a low-frequency (LF) output signal LFA»LFg to an LF switch 18 which forwards one or the other of the two signals to the LF amplifier 6 and the loudspeaker 7. From the tuner 2 the data signals (e.g. from the RDS data stream) are selected by means of the selection coupling 10, 11 and supplied to the storage 12 by the microprocessor 13. From the tuner 3 are also selected the data signals and fed to the storage 12 with the microprocessor 13. The tuner 2 can be tuned using manual or arbitrary input. The tuner 3 becomes by means of the bearing 12 or the microprocessor 13 over the wire 14 interrogated in accordance with the stored alternative list.

The recognition of the relevant transmitter with the greatest field strength takes place in the coupling 15 by means of a comparison of the received signals from the tuner 2 and the tuner 3. In the event that the transmitter with the field strength to be optimally received is not set with the tuner 2, the tuner takes over 3 this transmits with the strongest field strength, and its LF output signal LF is fed via the switch 18 to the LF amplifier 6 and the loudspeaker 7.

In this connection state, the tuner 2 is interrogated via a wire 20 from the microprocessor 12/13 in accordance with the frequencies stored in the alternative lists.

The LF signals LF^ and LFg are supplied to a coupling 19 for comparison of the modulation of both signals. In this modulation comparison connection, the modulation content of the transmitter set with the greatest field strength is compared with the modulation content of the transmitter selected from the alternative list. Appropriately, this comparison takes place in each case with the second strongest transmitter from the list.

The comparison can be made by direct comparison of the low-frequency voltage's time course or by comparing the envelope curves for the two LF signals. If thereby the transmitter with the greatest field strength due to reflection effects shows modulation breaks or modulation depressions and cut-offs of the low frequency (LF) due to override, the switch 18 is automatically switched by the microprocessor 12/13 to the next strongest transmitter, so that the distortions are hardly noticeable to the user. If both signals are identical, the transmitter with the respective greater field strength remains connected. Since then, the switch 18 of the currently active receiver A, B can constantly be switched to the respective other receiver B, Ai depending on the microprocessor's control. Exclusively in the case of manual or other input by the user, the tuner 2 is again first given priority, and then further subjected to the automatic, RDS-controlled mode of operation.

Claims (19)

1. Method for the transmission of digital information in a radio signal as a polling aid during broadcast reception, in which the digital information contains a number of separate lists of alternative frequencies assigned to the relevant transmitters in a transmission chain or optimized for these relevant transmitters, CHARACTERIZED IN THAT upon transmission of each list as a series of digital blocks with two digital pieces of information for each block, as a rule applies a) that in the first block of each individual list both information on the number of alternative frequencies for the list in question and the operating frequency for the transmitter assigned to the list in question, and b) in the remaining blocks of each individual list, both the operating frequency of the transmitter assigned to the list in question and the alternative frequency are transmitted. 2. Method according to claim 1, CHARACTERIZED IN THAT the operating frequency transmitted in the first block and/or in the remaining blocks of each list on the receiver side is used for assigning the alternative frequencies to the transmitter chain in question with a view to unambiguous, interference-proof addressing. 3. Method according to claim 1 or 2, CHARACTERIZED BY the fact that of the received, alternative frequencies for all frequency lists, only the alternative frequencies are stored and/or used for the voting for which the assigned operating frequency matches the radio device's currently set reception frequency. 4. Method according to one of claims 1-3, CHARACTERIZED BY the fact that the operating frequency for the relevant, alternative frequency in the remaining blocks is pre-set or post-set. 5. Method according to one of the claims 1-4, CHARACTERIZED BY the fact that the received digital information is subject to error correction, and that an addressing of the alternative frequencies occurring in accordance with the error-corrected digital information is carried out on the basis of the in or for each list - possibly several times - transmitted transmitter operating frequency. 6. Method according to claim 5, CHARACTERIZED BY the fact that detected bit errors are used for the received digital information as a quality assessment alone or in addition to the reception field strength. 7. Method according to claim 6, CHARACTERIZED BY the fact that the bit errors are used to assess program signal distortions in such a way that a) disturbances due to multi-path reception or interference are present in series-like appearing bit errors, b) disturbances due to noise are present in uniformly distributed errors, and c) the degree of all disturbances is derived from the block error rate of the block-structured RDS data signal, and whereby the following selection decisions are derived based on the bit errors determined both for each alternative transmission frequency and for the instantaneous reception frequency: d) if all tested frequencies mainly show only series-like or only evenly distributed bit errors, they are compared with each other with regard to their block error frequency, wherein the frequency with the lowest block error rate is selected for the receiver poll; e) if the tested frequencies show different bit error distributions, first the frequencies which in the main show only evenly distributed bit errors are pre-selected - possibly depending that a fixed, maximum permissible block error frequency is not exceeded at these frequencies -, and then the pre-selected frequencies are compared with each other with regard to to its block error rate, the preselected frequency with the lowest block error rate being selected for the receiver poll. 8. Procedure for receiver-side utilization of digital information transmitted in a radio signal, e.g. AF code and/or PI code in an RDS data signal, from which it can be immediately concluded or deduced on which alternative transmission frequencies the program signal for the instantaneous reception frequency can also be received, at which a) alternative transmission frequencies are determined for the instantaneous reception frequency at utilization of the AF code and/or the PI code and/or comparable codes, b) a receiving part of the receiver is briefly tuned to one or successively to several alternative frequencies, and the reception quality both for each of these alternative frequencies and for the instantaneous reception frequency is determined, and c) the frequency that currently offers the best possible reception quality is chosen as the optimal reception frequency, CHARACTERIZED IN THAT the reception quality is assessed in such a way that bit errors detected in the received digital information (for example in the received RDS data signal) are used as a measure for error correction and/or for quality assessment for program signal distortions to be determined, either alone or in addition to the receiving field strength. 9. Method according to claim 8, CHARACTERIZED BY the fact that the bit errors in the RDS data signal are used to assess the program signal distortions in such a way that a) disturbances due to multipath reception or interference are present in the case of series-like appearing bit errors, b) disturbances due to noise are present in the case of even distributed errors, and c) the degree of all disturbances is derived from the block error rate of the block-structured RDS data signal, and whereby the following selection decisions are derived on the basis of the bit errors determined both for each alternative transmission frequency and for the instantaneous reception frequency: d) if all tested frequencies in the main show only series-like or only evenly distributed bit errors, they are compared with each other with regard to their block error frequency, wherein the frequency with the lowest block error rate is selected for the receiver poll; e) if the tested frequencies show different bit error distributions, first the frequencies which in the main show only evenly distributed bit errors are pre-selected - possibly depending that a fixed, maximum permissible block error frequency is not exceeded at these frequencies -, and then the pre-selected frequencies are compared with each other with regard to to its block error rate, the preselected frequency with the lowest block error rate being selected for the receiver poll. 10. Method according to claim 8 or 9, in which the digital information contains a number of separate lists of alternative frequencies assigned to the relevant transmitters in a transmitter chain or optimized for these relevant transmitters, whereby the operating frequencies for the individual transmitters in the transmitter chain in each case are arranged at the beginning of the individual lists, CHARACTERIZED BY the fact that the received digital information is subjected to error correction, and that an addressing of the alternative frequencies is carried out in accordance with the error-corrected digital information on the basis of the one in or for each list - possibly several times - transmitted transmitter operating frequency. 11. Procedure for receiver-side utilization of digital information transmitted in a radio signal, e.g. AF code and/or Pl code in an RDS data signal, from which it can be immediately concluded or deduced on which alternative transmission frequencies the program signal for the instantaneous reception frequency can also be received, at which a) alternative transmission frequencies are determined for the instantaneous reception frequency at utilization of the AF code and/or the PI code and/or comparable codes, b) a receiving part of the receiver is briefly tuned to one or successively to several alternative frequencies, and the reception quality both for each of these alternative frequencies and for the instantaneous reception frequency is determined, and c) the frequency that currently offers the best possible reception quality is chosen as the optimal reception frequency, in that the digital information contains a number of separate lists of alternative frequencies assigned to the relevant transmitters in a transmitter chain or optimized for these relevant transmitters, whereby the operating frequencies for the individual transmitters in the transmitter chain are in each case arranged at the beginning of the individual lists, CHARACTERIZED BY that the received digital information is subjected to an error correction, and that an addressing of the alternative frequencies is carried out according to the error-corrected digital information on the basis of the transmitter operating frequency transmitted in or for each list - possibly several times. 12. Method according to one of claims 8-11, CHARACTERIZED BY the fact that the alternative frequencies contained in digital information, which in each case are transmitted as frequency pairs together with an associated transmitter operating frequency, are addressed and possibly stored according to it in relation to these immediately preceding or immediately following transmitter operation tsf frequency. 13. Method according to one of claims 8-12, as tuning aid during broadcast reception, in which the digital information contains a number of separate lists of alternative frequencies assigned to the relevant transmitters in a transmitter chain or optimized for these relevant transmitters, CHARACTERIZED IN THAT upon transmission of each list as a series of digital blocks with two digital pieces of information for each block, as a rule applies a) that in the first block of each individual list both information on the number of alternative frequencies for the list in question and the operating frequency for the transmitter assigned to the list in question, and b) in the remaining blocks of each individual list, both the operating frequency of the transmitter assigned to the list in question and the alternative frequency are transmitted. 14. Method according to claim 13, CHARACTERIZED IN THAT the operating frequency transmitted in the blocks in each list on the receiving side is used for assigning the alternative frequencies to the relevant list with a view to unambiguous, interference-proof addressing. 15. Method according to one of claims 8-14, CHARACTERIZED BY the fact that of the received, alternative frequencies for all frequency lists, only the alternative frequencies are stored and/or used for the vote for which the assigned operating frequency matches the radio device's currently set reception frequency. 16. Method according to one of claims 1-15, CHARACTERIZED IN THAT the alternative frequency which offers the currently best possible reception is checked with a view to whether it enables an acoustically acceptable reproduction, and that another alternative frequency is chosen in the event that the proven, alternative frequency only enables an acoustically distorted reproduction. 17. Method according to claim 16, CHARACTERIZED IN that manually adjustable means are used to select another alternative frequency. 18. Method according to claim 16 or 17, CHARACTERIZED IN that for the selection of another alternative frequency means are used which can be adjusted by a signal, the said signal - possibly also differently weighted - is derived both from the comparison of received field strengths and based on the comparison of low-frequency distortions assigned to the field strengths. 19. Method according to one of claims 1-18, CHARACTERIZED IN THAT the alternative frequencies on the receiver side are determined by utilizing a program identification code (PI code) contained in the digital RDS data signal, the receiving part performing a transmitter search and comparing the PI codes to the RDS data signals received on the individual transmitter frequencies in the direction that similar PI codes identify the frequencies on which the same program signal can be received.