JP2571249B2 - Receiving frequency selection method for radio data receiver - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radio data system receiver (hereinafter referred to as RD).
(Referred to as S receiver).

BACKGROUND ART When a broadcast station broadcasts, broadcast-related information such as information related to the program content is transmitted as data by multiplex modulation, and a desired program content can be selected on the receiving side based on the demodulated data. Radio data system (RD)
S) there.

In this radio data system, 57 kHz, which is the third harmonic of the 19 KHz stereo pilot signal outside the frequency band of the FM modulation wave, is used as a subcarrier, and the subcarrier is filtered and biphase-coded. The radio data signal is amplitude-modulated by a data signal indicating information related to the broadcast such as the content, and the amplitude-modulated subcarrier is frequency-modulated to the main carrier for broadcasting.

As is clear from FIG. 3 showing the baseband coding structure of the radio data signal, 104 bits correspond to 1 bit.
It is repeatedly multiplexed and transmitted as a group. One group is composed of four blocks each having a 26-bit configuration, and each block is composed of a 16-bit information word and a 10-bit check word. In FIG. 4, block 1 broadcasts program recognition (PI) data representing a network, block 2 broadcasts traffic program recognition (TP) data and traffic announcement recognition (TA) data, and block 3 broadcasts the same program. In the block 4, frequency (AF) data of a group of network stations, and information (PS) data of program services such as a broadcast station name and a network name are arranged in the block 4, respectively. In addition, each group has 4 bits of type 0 to 15 according to its contents.
There are 16 different types, and two versions of A and B are defined for each type (0 to 15). These recognition codes are arranged in block 2. In addition,
The AF data of the network station is transmitted only in the type 0A group.

By the way, in the case of an in-vehicle receiver, the reception state of the broadcast wave being received may deteriorate as the vehicle travels. However, in the case of RDS broadcasting, as described above, 1
When receiving two RDS broadcast waves, it is possible to obtain AF data of a group of network stations broadcasting the same program, and use this AF data to set the reception frequency to the frequency of another network station with good reception conditions. It is possible to switch.

For example, in the standby state of TA interruption by TA data, a TA interruption can be performed by taking in TA data obtained by demodulating a received broadcast wave. However, modulation of a main carrier (FM carrier) by a radio data signal is performed. Since the data demodulation sensitivity is low due to the low degree, there is a possibility that accurate demodulated data may not be obtained if the reception condition deteriorates, and in such a case, accurate TA data will not be obtained, The interrupt processing by the data cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is directed to a radio data receiver capable of reliably performing interrupt processing by interrupt data by selecting the same network station frequency having a good reception state. An object of the present invention is to provide a receiving frequency selection method.

The method of selecting a reception frequency in the radio data receiver of the present invention can receive a radio data broadcast wave in which radio data including frequency data of the same network station group, program identification data, and interrupt data indicating the type of program content are multiplex-modulated. A data demodulation circuit for demodulating a radio data component from a received radio data broadcast wave, and synchronizing radio data obtained by decoding the demodulated data of the data demodulation circuit in units of a predetermined number of data. And a synchronization circuit that takes a radio frequency signal in a radio data receiver, the method comprising: in a standby state of an interrupt waiting for a start of a specific program content based on interrupt data in radio data obtained by decoding; The synchronization circuit determines whether or not the radio data obtained by decoding is synchronized, If the synchronization is not achieved it is in the period circuit, switching from the current receiving frequency to another station frequency of the same network, given the frequency data receiving frequency,
If a radio data broadcast wave is received at any one other station frequency of the same network, one other station frequency is set as a new reception frequency.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1 showing an example of the configuration of an RDS receiver to which a receiving frequency selection method according to the present invention is applied, a desired station is selected by a front end 2 of an FM multiplex broadcast wave received by an antenna 1, and an intermediate frequency ( After being converted to IF), it is supplied to the FM detector 4 via the IF amplifier 3. The front end 2 employs, for example, a PLL synthesizer method using a PLL circuit including a programmable frequency divider, and performs a channel selection operation by controlling the frequency division ratio of the programmable frequency divider by a controller 14 described later. It has become.
The detection output of the FM detector 4 is supplied to an MPX (multiplex) demodulation circuit 5, and in the case of stereo broadcasting, L (left), R
The audio signal is separated into (right) channel audio signals, and is passed through the function switching circuit 19 to be reproduced audio output.
The function switching circuit 19 selectively outputs an audio signal from the MPX demodulation circuit 5 or, for example, the tape player 20, and its switching control is performed by the controller 14.

When the detection output of the FM detector 4 passes through the filter 6, a 57 KHz subcarrier amplitude-modulated by the biphase-coded data signal, that is, a radio data signal is extracted and demodulated by the PLL circuit 7. . This demodulated output is supplied to a digital (D) PLL circuit 8 and a decoder 9.
Supplied to In the D-PLL circuit 8, a clock for data demodulation is generated based on the demodulated output of the PLL circuit 7. The generated clock is supplied to the gate circuit 10. The lock detection circuit 11 detects that the D-PLL circuit 8 has locked, generates a lock detection signal, and supplies this to the gate circuit 10 to control the circuit 10 to open. The decoder 9 decodes the biphase-coded data signal, which is the demodulated output of the PLL circuit 7, in synchronization with the clock generated by the D-PLL circuit 8.

As shown in FIG. 3, the output data of the decoder 9 is in units of 104 bits consisting of four blocks each having a 26-bit configuration, and is sequentially supplied to the group and block synchronization & error detection circuit 12. The group / block synchronization & error detection circuit 12 synchronizes the group with the block based on the 10-bit offset word assigned to the 10-bit check word of each block, and 16-bit information based on the check word. Word error detection is performed. Also, the group / block synchronization & error detection circuit 12 outputs an out-of-synchronization detection signal to the controller 14 when the blocks are out of synchronization. The error detected data is sent to the next-stage error correction circuit 13.
Is supplied to the controller 14 after error correction.

The controller 14 is constituted by a microcomputer, and the code information of each block in the radio data sequentially inputted in the group unit, that is, the radio data information (the PI data and the AF data described above) related to the program contents of the broadcasting station currently being received. , PS data, etc.) and stores them in the memory 15. Based on a channel selection command from the operation unit 16, a programmable frequency divider (not shown) of the PLL circuit which constitutes a part of the front end 2. The tuning operation is performed by controlling the reception frequency data value that determines the frequency ratio. Further, the controller 14 is supplied with an out-of-synchronization detection signal from the group / block synchronization & error detection circuit 12, and when the out-of-synchronization detection signal is supplied, the controller 14 receives the out-of-sync signal from the broadcast station currently being received. Assuming that the state has deteriorated, an operation of controlling to select another same network station based on the AF data of the same network station group stored in the memory 15 in advance is also performed.

Further, a level detection circuit 17 for detecting a reception signal level (electric field strength) based on the IF signal level in the IF amplifier 3.
And a station detection circuit for detecting a receiving station and outputting a station detection signal when the IF signal level in the IF amplifier 3 is equal to or higher than a predetermined level and the detection output of so-called S curve characteristics in the FM detector 4 is within a predetermined level range. 18 and is provided,
The received signal level detected by the level detection circuit 17 and the station detection signal output from the station detection circuit 18 are supplied to the controller 14.

Next, the procedure of the receiving frequency selection method according to the present invention, which is executed by the processor of the controller 14, will be described in the second.
The description will be made according to the flowchart shown in FIG. Note that AF data obtained by demodulating the received broadcast wave is taken into the memory 15 and AF data lists f ₁ , f _2, ... F _{n of the} same network station as the currently receiving broadcast station have already been created. Shall be

The processor first, the flag F _A indicating that TA interruption waiting process is completed, it is determined whether it is "1" (step S
1) If F _A ≠ 1, it is determined whether the TA interrupt button on the operation unit 16 is on (step S2). If TA interrupt button is on, for example, TA interrupt waiting processing is performed (step S3) for controlling the function switching circuit 19 so as to select the audio signal from the tape player 20, followed by the previous flag F _A "1" Then, it is determined whether an out-of-synchronization detection signal has been generated from the group / block synchronization & error detection circuit 12 (step S5). On the other hand, when it is determined that F _A = 1 in step S1, it is determined whether the TA data is “1” (step S1).
6) If TA = 1, the process shifts to the interrupt mode based on the TA data. If TA ≠ 1, the process shifts to step S5.

If it is determined in step S5 that the out-of-synchronization detection signal has been generated, it is determined whether or not the signal has continued for a predetermined time (step S7). The PI data obtained from the currently received broadcast wave and the reception frequency are taken as the reception condition is deteriorated, and stored in an accumulator or the like (step S8). Subsequently, according to the AF data list, one AF data in the list is read from the memory 15 (step S9), and this AF data is output to a PLL circuit (not shown) in the front end 2 to perform a tuning operation (step S9). S1
0). Then, it is determined whether or not the reception signal level V _S obtained from the level detecting circuit 17 is set level V _H or (step S11), and if V _S ≧ V _H, takes in the signal level of the received frequency Is stored in the memory 15 in association with each AF data (step S12). The set level V _H or more received signal level of incorporation, until it is determined that a check of the received signal levels of all the network station frequency has been completed (step S13), and sequentially repeated according to AF data list. On the other hand, if V _S <V _H in step S11, it is determined whether the check of the received signal levels of all the network station frequencies has been completed (step S14). If not, the process returns to step S9. The above operation is repeated. If completed, it is determined whether there is a reception frequency of the set level V _H or the received signal level (step S1
5) If there is, move to the next step.

When the reception signal levels for all the network station frequencies have been checked, the AF data with the highest level is read out from the reception signal levels stored in the memory 15 in advance (step S16), and tuning based on this AF data is performed. The operation is performed (step S17), and PI data representing the network station of the receiving station is fetched (step S18), and it is determined whether or not the PI data matches the PI data stored in the memory 15 (step S18). Step S1
9). If the PI data match, it is further determined whether the TP data is "1" (step S20). If TP = 1, the same network station frequency currently being received is set as a new reception frequency. Shift to normal reception mode.

If it is determined in step S19 that the PI data does not match, it is determined whether the check of the PI data for all the network station frequencies for which the received signal levels are stored in the memory 15 has been completed (step S21), and the process ends. If not, the AF data with the next highest received signal level is read (step S22), and the process returns to step S17 to perform a tuning operation based on the AF data. If the check of the PI data for all the network station frequency has been completed, because mean that the reception frequency of the received signal level is above the set level V _S in the same network station group were not present, held in step S8 The called AF data is called up and returns to the original reception frequency (step S23).

If it is determined in step S20 that TP ≠ 1, it is determined whether the check of the TP data for all the network station frequencies for which the received signal levels are stored in the memory 15 has been completed (step S24). If not, the AF data with the next highest received signal level is read out (step S25), and the process returns to step S17 to perform a tuning operation based on the AF data. If the check of the TP data for all the network station frequency ends, because the received signal level is the broadcast station even if there is the same network station frequencies above the set level V _S is necessarily not a traffic information broadcasting station Then, the AF data held in step S8 is called to return to the original reception frequency (step S26).

As described above, in the standby state of the TA interrupt, if the synchronization in the group / block synchronization & error detection circuit 12 is lost, it is considered that the reception state of the currently receiving broadcast station has deteriorated and the same network having a good reception state is considered. By switching the receiving frequency to the station frequency, accurate demodulated data can always be obtained by demodulating the data in a stable receiving state, so that the interrupt processing by the TA data is performed reliably, and the traffic information is heard. Can be reliably performed. In particular, by selecting the same network station frequency having the highest received signal level, the interrupt processing can be performed more reliably.

In the above-described embodiment, the case of the TA interrupt by the TA data which is the interrupt data has been described. However, the present invention is not limited to this, and PTY (program type) data or M / S
The present invention is also applicable to the case of interruption by interruption data such as (music / speechswitch) data. In this case, the processing of step S24 and steps S28 to S30 becomes unnecessary.

Effect of the Invention As described above, according to the reception frequency selection method of the present invention, decoding is performed in a standby state of an interrupt waiting for the start of a specific program based on interrupt data in radio data obtained by decoding. Is out of synchronization with the obtained radio data, the receiving frequency is switched from the current receiving frequency to another station frequency of the same network given by the frequency data, and any other station of the same network is switched. If a radio data broadcast wave is received at a frequency, the other station frequency is set as a new reception frequency, so that accurate demodulated data is always obtained by performing data demodulation in a stable reception state. Therefore, the interrupt processing based on the interrupt data can be reliably performed.

[Brief description of the drawings]

FIG. 1 shows a case where a receiving frequency selecting method according to the present invention is applied.
FIG. 2 is a block diagram showing the configuration of the RDS receiver, FIG. 2 is a flowchart showing a procedure of a receiving frequency selection method according to the present invention executed by a processor in the controller of FIG. 1, and FIG. 3 is baseband coding of a radio data signal. FIG. 4 is a diagram showing a structure, and FIG. 4 is a diagram showing a format of a type 0A group. Description of main parts 2... Front end, 4... FM detector 5... Multiplex demodulation circuit 8... Digital PLL circuit 9... Decoder, 14.

Claims (1)

(57) [Claims] 1. A radio data broadcast wave obtained by multiplex-modulating radio data including frequency data, program identification data, and interrupt data indicating the type of program content of the same network station group. A radio comprising: a data demodulation circuit for demodulating a radio data component from a broadcast wave; and a synchronization circuit for synchronizing radio data obtained by decoding the demodulated data of the data demodulation circuit in units of a predetermined number of data. A method of selecting a reception frequency in a data receiver, the method comprising the steps of: receiving the decoded data in a standby state of waiting for the start of a specific program content based on the interrupt data in the radio data obtained by decoding; It is determined whether or not the radio data is synchronized by the synchronization circuit, and the synchronization is performed by the synchronization circuit. If not, the receiving frequency is switched from the current receiving frequency to another station frequency of the same network given by the frequency data, and if a radio data broadcast wave is received at any one of the other station frequencies of the same network, A method for selecting a reception frequency in a radio data receiver, wherein the one other station frequency is set as a new reception frequency.