Abstract:
An RDS-system radio having an automatic tuning function which is configured to compare program information codes of a currently received broadcasting and other broadcastings in a seeking or scanning operation to avoid switching to new broadcastings which are identical to the currently received broadcasting in order to prevent useless steps in the seeking or scanning operation.

Description:
FIELD OF THE INVENTION 
     This invention relates to an RDS system radio, in particular, of a type having a seek, scan or other automatic tuning function. 
     DESCRIPTION OF THE PRIOR ART 
     Not only in an RDS (radio data system) system radio but also in other prior art radio having an automatic tuning function, when a scan or seek operation is effected, the radio stops its scan or seek operation upon catching a broadcasting of a field strength above a predetermined level and starts reception of the broadcasting. In the case, since a condition for stopping the automatic tuning and starting the reception is only that the field strength is above a predetermined level, the radio stops its tuning operation and starts the reception also when it is the same broadcasting as that heretofore listened to. 
     However, considering the reason why a user effects a seek or scan operation, a user has a purpose of searching any other broadcasting he desires. Therefore, it is a useless operation to tune at the same broadcasting as that heretofore received. This useless operation causes a delay of the seek or scan operation, and particularly in a seek operation, a certain key operation is required once more to search another broadcasting. 
     SUMMARY OF THE INVENTION 
     This invention has been made to improve the aforementioned drawbacks of the prior art, and is characterized basically in that in sequentially changing the received frequency in order to change the received broadcasting from one to another, a PI (program identification) code of a broadcasting heretofore received is compared to a PI code of a newly received broadcasting so that the newly received broadcasting is not selected when these PI codes coincide. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing an arrangement of an RDS-system radio to which the invention can be applied; 
     FIG. 2 is a flowchart showing a general seek operation according to the invention; and 
     FIG. 3 is a flowchart showing a general scan operation according to the invention. 
    
    
     DETAILED DESCRIPTION 
     The invention is described below, referring to a preferred embodiment illustrated in the drawings. 
     FIG. 1 shows an arrangement of an RDS-system radio. 
     An RDS (radio data system) broadcasting received by a tuner 1 through an antenna is decoded in an RDS decoder 2 and is subsequently entered in a microcomputer 3 as RDS data. The RDS data includes a PI (program identification) code which identifies the broadcasting. 
     The tuner 1 sends an S meter (signal meter) output showing the field strength of the broadcasting in reception to the microcomputer 3 through an A/D (analog-to-digital) converter 4. Reference numeral 5 denotes a low-pass filter. 
     When a signal for instructing a seek operation is applied by an operation means 6, the microcomputer 3 controls the tuner 1 o change the received frequency sequentially and, in receipt of field strength information from the A/D converter 4, stop the seek operation at the frequency having a predetermined field intensity and effect reception at the frequency. 
     Similarly, when a signal for instructing a scan operation is applied from the operation means 6 to the microcomputer 3, the microcomputer 3 controls the tuner 1 to repeat motions of sequentially receiving station having received field intensities above a predetermined level by a predetermined time. 
     In the prior art, if a frequency has a predetermined field intensity, reception is always effected at the frequency, and it was not judged at all whether it is the same as the broadcasting program heretofore received. 
     In the embodiment of the invention, the microcomputer 3 effects comparison of the PI code included in the RDS data from the RDS decoder 2. That is, the PI code of the broadcasting program heretofore received is compared to a PI code of a broadcasting program to be received subsequently by changing the frequency. If these PI codes are identical, the same broadcasting is identified. Therefore, the microcomputer 3 controls the tuner 1 to not receive the broadcasting of the frequency and switch to a subsequent frequency to receive another broadcasting. 
     FIG. 2 shows a flowchart of a seek operation. When an operator effects a seek-starting operation, the microcomputer 3 controls the tuner 1 to start the seek (step 20). At first, the microcomputer 3 sets the tuner 1 at a predetermined frequency, enters its S meter output from the A/D converter 4, and judges whether the field strength is above a predetermined level (step 21). When the field strength is above the level, the PI code (PI) of the presently received broadcasting program is compared to the PI code (PI&#39;) of the newly selected broadcasting program in the RDS data from the RDS decoder 2 (step 22). When PI is different from PI&#39;, the newly selected broadcasting is received (step 23). When PI and PI&#39; are identical, the microcomputer 3 controls the tuner 1 to not receive the newly selected broadcasting, and after checking whether it returned to the original frequency or not (step 25), raise (or drop) the frequency by the minimum inter-station frequency (step 26) and select a next broadcasting, returning to step 21. After a newly selected broadcasting is received in step 23, the seek is finished (step 24). When the seek returns to the original frequency in step 25, this means that there is no new broadcasting to switch to, and it returns to the originally received broadcasting (step 27), and the seek operation is finished. 
     FIG. 3 shows a flowchart of a scanning operation. 
     Upon a user&#39;s operation for starting a scanning, the microcomputer 3 controls the tuner 1 to start such a scanning (step 30), sets the tuner 1 at a predetermined frequency, enters its field strength signal from the A/D converter 4, and judges whether the field strength of the broadcasting is above a predetermined value or not (step 31). When the field strength is above the level, the PI code PI of the presently received broadcasting program is compared to the PI code PI&#39; of the newly selected broadcasting program (step 32). When PI and PI&#39; are not identical, the newly selected broadcasting is received for a predetermined time (step 33). 
     When PI and PI&#39; are identical, the microcomputer 3 controls the RDS decoder 2 to not receive the newly selected broadcasting and jump step 33 to check whether it has returned to the originally received frequency or not (step 34), raise (or drop) the frequency by the lowest inter-station frequency (step 37), select a next broadcasting, returning to step 31, and repeat the same operation. Also when the frequency does not reach the predetermined field strength, the scanning jumps to step 34. 
     After reception for a predetermined time in step 33, the scanning traces step 34, and in step 37 selects a next broadcasting, repeating the aforementioned operation. 
     When the scanning returns to the originally received frequency in step 34, this means that there is not new broadcasting to switch to, and it returns to the originally received broadcasting (step 35), and the scanning is finished (step 36). 
     As described above, since the inventive reception method is arranged so that when changing from a presently received broadcasting to another broadcasting by switching the received frequency sequentially, a PI code of the presently received broadcasting is compared to a PI code of a newly received broadcasting in order to not receive the new broadcasting when these PI codes are identical, no useless operation occurs, and the operating speed of the radio in scanning or seeking operations is improved.