JP2531692B2 - Receiver with control function by radio data - Google Patents

Description

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

Background Art When a program is broadcast by a general broadcasting station, information related to the program content is transmitted as data by multiplex modulation, and the desired program content can be selected based on the demodulated data on the receiving side so that a radio listener can select it. There is a radio data system (RDS) that makes it possible to provide that service to.

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

As is clear from FIG. 2 showing the baseband coding structure, the radio data signal is repeatedly multiplexed and transmitted with 104 bits as one 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. 2, a block 1 is a program recognition (PI) code, a block 2 is a traffic program identification (TP) code, and a block 3 is a station frequency (AF) code of a network station broadcasting the same program. However, in block 4, program service name information (PS) such as broadcasting station name and network name
Data is arranged respectively. In addition, each group is classified into 16 types of types 0 to 15 by 4 bits according to the contents, and each type (0 to 15) has two types of A and B respectively.
One version is defined and these identification codes are located in block 2. The station frequency (hereinafter abbreviated as AF) code of the network station is to be transmitted only in the type 0A group.

In this way, the type 0A group radio data also includes AF data of network stations that are broadcasting the same program as the currently receiving broadcast station, and AF data obtained by demodulation during reception If the reception sensitivity of the broadcasting station currently being received is reduced due to disturbance such as a decrease in the signal strength (level) of the received broadcast wave, it is based on the AF data of the network station stored in advance. By selecting another network station according to the above, it is possible to always listen to the same program in a good reception state without being affected by disturbance.

By the way, if the received broadcast wave signal level drops while some AF data is stored in advance, you can select another network station as described above, but AF data cannot be stored yet. If the signal level drops when there is no signal, it is obtained from the broadcast wave currently being received.
The network station will be selected based on the AF data. However, if the network station is selected based on the currently received AF data, the reception status is deteriorated when the signal level of the received broadcast wave drops, so reception at the data error correction stage. There is a possibility that erroneous error correction will be performed due to the deterioration of the state, and in this case erroneously corrected data will be fetched.

Also, not only AF data but also radio data has data contents that constantly change over time, and it is necessary to capture such data each time.In this case as well, the signal level of the received broadcast wave is When is decreased, there is a possibility that the error-corrected data may be fetched due to the deterioration of the reception state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a receiver having a control function by radio data capable of preventing the acquisition of erroneous correction data when the signal level of a received broadcast wave is lowered. The purpose is to do.

A receiver according to the present invention is based on a data demodulation circuit that demodulates radio data included in a received broadcast wave, an error detection circuit that detects an error in demodulation data of the data demodulation circuit, and a detection output of the error detection circuit. A receiver having a radio data control function having an error correction circuit that performs error correction on the demodulated data and a controller that performs various controls based on the output data of the error correction circuit, and is a signal of a received broadcast wave. First level
A level below which the first detection signal is generated and a level above which the second detection signal is generated when the level exceeds the first setting level and is below the second setting level which is higher than the first setting level. A detection circuit, which inhibits data fetching to the controller when the first detection signal is generated, inhibits the error correction when the second detection signal is generated, and performs only the error detection; When both the first and second detection signals are in the non-occurrence state, the error detection and the error correction are performed.

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

FIG. 1 shows an RDS equipped with a data control device according to the present invention.
It is a block diagram which shows the outline of a basic structure of a receiver.
In the figure, for the FM multiplex broadcast wave received by the antenna 1, the desired station is selected by the front end 2 and the intermediate frequency (I
After being converted into F), it is supplied to the FM detector 4 via the IF amplifier 3. The front end 2 adopts, 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. Has become. The detection output of FM detector 4 is MPX
It is supplied to the (multiplex) demodulation circuit 5 and is separated into L (left) and R (right) channel audio signals in the case of stereo broadcasting.

Further, the detection output of the FM detector 4 passes through the filter 6, so that the 57 KHz subcarrier amplitude-modulated by the biphase-coded data signal, that is, the radio data signal is extracted and demodulated by the PLL circuit 7. . This demodulated output is the digital (D) PLL circuit 8 and the decoder 9.
Is supplied to. The D-PLL circuit 8 generates a data demodulation clock based on the demodulation 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 is locked, generates a lock detection signal, supplies the lock detection signal to the gate circuit 10, and controls the circuit 10 to be in an open state. In the decoder 9, the bi-phase coded data signal which is the demodulated output of the PLL circuit 7 is decoded in synchronization with the clock generated in the D-PLL circuit 8.

The output data of the decoder 9 is 26bi as shown in FIG.
It is a 104-bit group unit consisting of 4 blocks of t configuration, and is supplied to the group / block synchronization & error detection circuit 12 via the switch circuit 17 together with the clock passed through the gate circuit 10. In the group / block synchronization & error detection circuit 12, the group and the block are synchronized based on the 10-bit offset word assigned to the 10-bit check word of each block, and the error of the 16-bit information word is generated based on the check word. Detection is performed. The error-detected data is subjected to error correction by an error correction circuit 13 at the next stage, and then the controller
Supplied to 14.

The controller 14 is composed of a microcomputer, and takes in code information of each block in the radio data sequentially input in units of groups, that is, information related to the program contents of the broadcasting station currently being received, and a memory 1 such as a RAM.
5 and the frequency division ratio of a programmable frequency divider (not shown) of a PLL circuit constituting a part of the front end 2 is controlled based on a channel selection command from the operation unit 16. Perform the operation.

Further, a level detection circuit 18 that detects that the signal strength (level) of the received broadcast wave has decreased based on the IF signal level.
The level detection circuit 18 is provided with a first set level corresponding to the signal level of the received broadcast wave and the first set level.
Has a second setting level higher than the setting level of
A first detection signal is generated when the signal level is below the first set level, and a second detection signal is generated when the signal level is above the first set level and below the second set level, and supplied to the controller 14. The controller 14 controls the switch circuit 17 to be in an open state when the first detection signal is generated, and the second
When the detection signal is generated, the switch circuit 17 is closed and the error correction circuit 13 is controlled to prohibit the error correction.

As a result, when the first detection output is generated, that is, when the signal level of the received broadcast wave is extremely lowered, the supply of the demodulated data and the clock to the group / block synchronization & error detection circuit 12 is stopped. Data acquisition to 14 will be prohibited. Meanwhile, the second
When the detection signal is generated, that is, when the signal level of the received broadcast wave is lowered to some extent, error correction is prohibited and only error detection is performed. Therefore, regarding the error-detected data, the controller 14 as it is according to the data content.
It will be taken in by or thrown away. Note that when the IF signal level exceeds the second set level, the reception sensitivity is in a good state, so that both error detection and error correction are performed, and only data that has been correctly error-corrected is taken into the controller 14. become.

In this way, when the signal level of the received broadcast wave decreases, if the level decrease is extreme, the controller 14
By prohibiting the fetching of data into, it is possible to prevent fetching of erroneously corrected data in the case where error correction is erroneously performed due to deterioration of the reception state due to a decrease in level. Further, when the level is lowered to some extent, the error correction is prohibited and only the error is detected, so that the error-detected data can be fetched according to the data content and the erroneous correction of the data can be prevented. become.

In the above embodiment, the case where the acquisition of radio data is prohibited by stopping the supply of demodulated data and clock to the group / block synchronization & error detection circuit 12 has been described, but the present invention is not limited to this. Rather, the point is that the radio signal can be prohibited from being taken into the controller 14 when the signal level of the received broadcast wave becomes equal to or lower than the first set level.

As described in detail above, according to the present invention, a data demodulation circuit that demodulates radio data included in a received broadcast wave, and an error detection circuit that detects an error in the demodulated data,
Reception having a radio data control function having an error correction circuit for performing error correction on the demodulated data based on the detection output of the error detection circuit and a controller for performing various controls based on the output data of the error correction circuit In the machine, when the signal level of the received broadcast wave is equal to or lower than the first preset level, the first detection signal is equal to or lower than the second preset level which exceeds the first preset level and is larger than the first preset level. At this time, a level detection circuit for respectively generating the second detection signal is provided, and when the first detection signal is generated, the fetching of data into the controller is prohibited.
When the detection signal is generated, the error correction is prohibited and only the error detection is performed. When both the first and second detection signals are in the non-occurrence state, the error detection and the error correction are performed. As a result, it is possible to adopt a three-step data processing mode according to the reception level, which can prevent erroneous correction of data and acquisition of erroneously corrected data that are likely to occur due to deterioration of the reception state, and Even if the condition deteriorates, the data can be used according to the degree of the condition, and the control by the data can be continued as much as possible without malfunction even in the bad reception environment.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a basic configuration of an RDS receiver provided with a data control device according to the present invention, and FIG. 2 is a diagram showing a baseband coding structure of radio data. Explanation of symbols of main parts 2 …… Front end, 4 …… FM detector 5 …… Multiplex demodulation circuit 8 …… Digital PLL circuit 9 …… Decoder, 14 …… Controller 17 …… Switch circuit 18 …… Level detection circuit

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display area H04L 27/22 H04L 27/22 Z

Claims (1)

(57) [Claims] 1. A data demodulation circuit for demodulating radio data included in a received broadcast wave, an error detection circuit for detecting an error in demodulated data of the data demodulation circuit, and the demodulation based on a detection output of the error detection circuit. A receiver having a radio data control function having an error correction circuit for performing data error correction and a controller for performing various controls based on output data of the error correction circuit, wherein a signal level of a received broadcast wave is A first detection signal is generated when it is below a first set level, and a second detection signal is generated when it is below a second set level which exceeds the first set level and is larger than the first set level. And a level detection circuit for controlling the generation of the second detection signal when the first detection signal is generated. Sometimes the error correction is prohibited and only the error detection is performed. When both the first and second detection signals are in the non-occurrence state, the radio data is characterized in that the error detection and the error correction are performed. Receiver with control function.