RDS broadcast receiver with a device for accelerated seeking of alternative frequencies.

p0001The Radio Data System (RDS), a binary data stream is parallel to the broadcast radio program, inaudible to the radio listener, transmitted, which provides the receiver a series of tuning, switching and operating information. Among other things, such. As a tuning aid continuously called transmitted PI code (Program Identification code) that allow the receiver to assign a station frequency to a specific program chain and offer him alternative frequencies with which the same program can be received. This RDS service is especially useful for mobile broadcast receiver, because can change the reception conditions constantly displacements.

p0002However, the transmission of alternative frequencies from the transmitter to the receiver through wave propagation can take up to two minutes in the limit (interference-free reception provided) since the AFs in the form of lists are received sequentially. The organization of these lists, for which there are two variants A and B, is in the specification of the radio data system, DIN pr. EN 50 067. detail in October 1988, will be explained in more detail here.

p0003In order to supply the radio listener without prolonged interruption of the current program, it is therefore necessary that the receiving device in deterioration of reception conditions may have recourse to already registered alternative frequencies within an internal memory. This method, as one of the bases of the radio data system is known from DE-PS 34 48 043rd

p0004If, however, the first time the radio receiver set by manual tuning or station search to a RDS station, it may take a long time until one of the currently received frequency assigned list of alternative frequencies is stored as u when disturbed reception of RDS data. must wait U. a multiple pass of the AF lists to unique decoding.

p0005To shorten the time and increase the safety in the generation of a list of alternative frequencies in the memory of the receiving device is therefore in the DE-PS 37 37 535 proposed in the transmission of alternative frequencies from the transmitter to the receiver according to the method B in accordance with DIN pr. EN 50067 not only wait for the currently received frequency associated AF list, but also with the AF-lists, the other transmission towers on the broadcasting network are assigned to pay attention to whether the currently received frequency as AF another mother frequency emerges. In this case the master frequency is to be stored as an alternative frequency of the current reception frequency.

p0006The disadvantage of this method is that even frequencies can be saved as alleged AFs who are not members of the regional list of the received frequency. this ambiguity is triggered by the fact that a mother frequency within the coverage area of ​​a program chain can repeatedly be used. So sends z. B. the Bayerische Rundfunk his second radio program on a frequency of 88.4 MHz on both the transmitter Ismaning near Munich and via the transmitter Pfaffenberg near Aschaffenburg. The transmitter Pfaffenberg dive (93.1 MHz) in its regional AF list than alternative frequency to the transmitter Kreuzberg. If now the frequency of the transmitter Kreuzberg as AF of z. B. currently received frequency of the transmitter Ismaning is stored in the local coverage area in Munich, this frequency is worthless for a fast frequency hopping and only delays the tuning to a reception worthy alternative frequency.

p0007DE-PS 38 35 870 in contrast, describes a method by which during an automatic or user-initiated channel scan on the one hand the decodable PI codes and secondly the available RDS-frequencies are stored with respective assignment to the corresponding PI codes. This resulting AF lists that u due to reception conditions at the location of the recipient. May not include all actually existing alternative frequencies of the program chain, are then supplemented by the addition AFs in the RDS data signal.

p0008Although this process leads to an accelerated development of the AF lists the device's own memory, but shows flaws in terms of really existing reception quality of the alternative frequencies in a given coverage area, as an evaluation of the receivability within the individual everyday action circle of radio listener, especially the motorist , is not made.

p0009Object of the present invention was in contrast, an RDS radio receiver, in particular RDS car radio, to be provided with a device that the acquired into memory RDS receiving frequency supplemented by a manually triggered RDS station search with those alternative Freqenzen which in a or more program memories of the receiving device are stored with prior confirmation of their receivability. To this end, the PI codes existing in the program memories RDS frequencies with the PI code of the memory currently acquired RDS receiving frequency are compared, and if they match the alternative frequencies are transmitted directly into the dynamic AF list of memory.

p0010The advantage of this arrangement is that in the program storing for prolonged periods of empirically grown AF lists are available immediately and at a necessary frequency changes the likelihood that one or more alternative frequencies are also poor signal quality. This is particularly useful when at the receiving frequency found in the search, the transmission of alternative frequencies is disturbed in the RDS data signal.

p0011The invention, whose essential characteristics are set out in Claim 1 and set forth the advantageous embodiments in the dependent claims will be explained below using the drawings.

p0012It shows:<dl id="dl0001"><dt>Fig. 1</dt><dd> the block diagram for one embodiment of the radio receiver according to the invention </dd><dt>FIG. 2</dt><dd> a flowchart of the control sequence for manual triggering of the RDS channel search</dd></dl>

p0013The illustrated in Fig. 1 RDS broadcast receiver includes in a conventional manner 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. As a central control unit connected to the control unit 11, the microprocessor 9, which also provides for tuning the necessary tuning of the synthesizer tuner 1 is used. The reception quality is monitored by the level detector 5 and the multi-path detector. 6 The level detector 5 extracts the IF amplifier 2 according to the IF signal level a process variable to determine the signal strength while the multipath detector 6 high-frequency interference amplitudes multiplexed signal caused by multipath reception evaluates. The analog / digital conversion of the control signals for the microprocessor 9 is carried out either in the two detectors 5, 6 or in the microprocessor 9, unless it is provided with corresponding transducer inputs. The RDS demodulator 7 is also fed with the demodulated multiplex signal. After a 57 kHz band-pass filtering the amplitude modulated in quadrature RDS signal is demodulated and the recovered after a subsequent differential biphase and decoding digital data supplied to the microprocessor 9 for subsequent processing.

p0014As a working memory of the microprocessor 9 has the RAM memory 12. The operation program is stored in ROM memory. 13 The EEPROM 14 serves as a non-volatile program memory and includes in its individual storage levels for each stored program in addition to the PI code and the PS code (Programme Service Name Code to display the name of a program chain in the display 10), a number of selected alternative frequencies for a spontaneous program retrieval. The AF lists this program memory 14 are constructed empirically extended period because whenever the PI code of a tested on reception frequency in the memory 12 coincides with the PI code of a program memory, this frequency as proven AF by the microprocessor 9 in the associated program memory is transferred automatically. Thus, the program memory contains not all offered with the RDS data signal alternative frequencies, but only a limited range, which is important for the device user, given his usual itinerary. The access time when changing to a reception worthy alternative frequency is considerably reduced by this measure.

p0015If an RDS station search is started via the operating unit 11, the microprocessor 9 to initiate a tuning and memorizing process, as it is exemplified in the flowchart of FIG. 2.

p0016After starting the RDS station search is checked in program step 1, if a frequency change is locked, as adopted in this case, a scan command from the microprocessor 9 and the program is terminated immediately. Is not active the change lock, the power stage 4 is muted via the electronic switch 8 and the tuner 1 from the microprocessor 9 tuned gradually in step. 2 Detects the microprocessor 9 in step 3 a station it where it evaluates the signals of the level detector 5 and possibly also the multipath detector 6, he first stops the search and initializes a counter for the time t. In program step 5 controls the microprocessor 9 if he gets 7 RDS signals via the RDS demodulator. If not, it sets this test on step 8 for as long until the time t has exceeded the value t₁. In this case, the program returns to the step 2, that is, the tuner 1 is further tuned.

p0017T₁ be RDS signals decoded within the time, the microprocessor 9 checks in step 7 whether a valid PI code is recognized. This test, which respects at a special search for RDS traffic information stations on the proper decoding of the TP-bits (Traffic Programme bit), will be continued maximally t₂ to time; thereafter the program Step 8 to Step 2 feeds back.

p0018Detects the microprocessor 9 faultless PI code, so he takes the step 9, the RDS concerned or RDS-TP frequency into memory 12 and unmutes the amplifier 4. In program step 10, it activates a change lock to receive no further search command from the operating unit 11 and sets a timer for the elapsed time t_ws to zero. He then compares at step 11 the PI code of the loaded into the main memory 12 frequency with the PI code of the program store 14 (or equivalent additional storage) frequencies contained and transfers in accordance in step 12, the frequencies of the corresponding program memory level as alternative frequencies in the RAM 12, program step 13 returns to step 11, as long as the elapsed time t_ws has not reached the value t₃ for changing lock. Only after the change of lock is released and terminated the program run in step 14th

p0019Not shown in the flowchart of FIG. 2, that at each frequency change because of deteriorating reception conditions, the quality evaluation of the alternative frequencies in the working memory 12 is updated and that alternative frequencies are determined from the RDS data stream through wave propagation, subordinated in the evaluation result or, if no AFs could be transferred from the program memory 14, are stored as the only alternative frequencies. For this reason the list of alternative frequencies can be referred to as dynamic AF list in memory 12th