JP2564391Y2 - Radio data system receiver - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio data system (RDS) receiver, and more particularly to a radio data system (RDS) having a reduced mute time during an alternative frequency search (AF search) in an RDS system. Regarding the receiver.

[0002]

2. Description of the Related Art RDS is a system described in the European Broadcasting Union Technical Specification (EBU document 3244), which enables a listener to easily search for a desired radio program. Among the functions of this system is a function to notify the radio receiver that the frequency is allocated to another broadcasting station that is broadcasting the same program as the program currently being received. If the station frequency can obtain a stronger signal, it is possible to switch the receiver there. Therefore, an AF search is performed.

[0003] The AF search operation in a conventional RDS receiver detects the electric field strength of a receiving station from an intermediate frequency output to judge whether or not it is higher than a predetermined level, and demodulates RDS information from a detection output. The alternative frequency information (AF data) from the demodulated RSD information is stored in the RAM in the system microcomputer, and when the detected electric field intensity is lower than a predetermined level, the mute state is controlled. The AF data stored in the RAM is read, and the frequency-divided data of the variable frequency divider of the PLL frequency synthesizer constituting the local oscillator is changed to frequency-divided data based on the AF data.
The electric field strength of the station corresponding to the divided data is detected, and when the detected electric field strength is equal to or higher than the electric field strength set as the movable condition, the station is determined to be movable and the reception is switched to the station corresponding to the divided data. At the same time, the mute state is released.

[0004]

However, in the conventional RDS receiver, the noise canceler is always operating, and the noise canceler works due to the noise generated during the AF search, thereby increasing the noise or conversely the voice. There has been a problem that the mute period must be lengthened in order to drop the signal.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an RDS receiver in which the occurrence of noise during an AF search is reduced, the mute period during an AF search is shortened, and the feeling of sound interruption is reduced.

[0006]

The RDS receiver of the present invention sends the output from the detection circuit to the next stage including a mute circuit.
A radio data system comprising a noise canceller for outputting RDS information, and capable of automatically switching a receiving station to a station having a good reception state by searching for AF data in the RDS information. at the receiver, the
Open the mute circuit at the start of the search and
To close the mute circuit at the end of the above search.
Output muting control signal to the mute circuit
Mute control signal generator and search mute control signal
Control to open the mute circuit by
Stop the noise canceling operation of the canceller, and
The noise cancel is delayed for a predetermined period from the time when the cut circuit is closed.
Signal to start the noise cancellation operation of the
Generates a noise cancel stop signal output to the canceller
Means .

[0007]

According to the RDS receiver of the present invention, the noise canceling operation of the noise canceller is started by the noise canceling stop signal output from the noise canceling stop signal generating means when the mute state starts during the search. The noise canceling stop state is canceled almost at the same time, and the noise canceling stop state is canceled with a delay of a predetermined period from the cancellation of the mute state. Since the operation of the noise canceller is stopped, the sound signal is not damaged by an unnecessary cancel operation, and the mute period during the search does not need to be made longer than necessary, and the feeling of interruption of sound disappears. In addition, noise sensation due to noise cancellation malfunction is reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. FIG.
FIG. 2 is a block diagram showing a configuration of an embodiment of the present invention. The RDS receiver according to the present embodiment includes a front end 1, an intermediate frequency circuit for amplifying an intermediate frequency signal output from the front end 1, an intermediate frequency / detection circuit 2 for detecting an output of the intermediate frequency circuit, and noise in the detection output. Noise canceller-3 to be removed, stereo demodulation circuit 4 for receiving and demodulating the detection output from which noise has been removed, volume control circuit 5 for controlling the volume of the output of stereo demodulation circuit 4, and muting the volume-controlled audio signal. Mute circuit 6, Mute circuit 6
-Frequency amplifier 7 for amplifying the output from the amplifier, low-frequency amplifier 7
Is provided with a speaker 8 driven by the output. The noise canceller 3 is configured to stop the noise cancel operation in response to the noise cancel stop signal, and the mute circuit 6 receives the mute control signal to mute the noise.
It is configured to perform a reset operation.

The RDS receiver further includes a PLL frequency synthesizer 9 constituting a local oscillator, an RDS demodulator 10 for demodulating the RDS information from the detected output from the detected output, and detecting the RDS information in synchronization with the demodulated RSD information. Synchronization microcomputer 11, an electric field strength signal detected from the intermediate frequency output, and a synchronization microcomputer.
The RDS information extracted from the data 11 is input, the AF data in the RDS information is stored in the RAM, the frequency-divided data is sent to the variable frequency divider of the PLL frequency synthesizer 9, and the AF search is performed. The system microcomputer 12 stops the mute operation and stops the noise cancel operation for a predetermined period.

The operation of the embodiment constructed as described above will be described with reference to the flowchart shown in FIG. Front end 1, intermediate frequency / detection circuit 2, noise canceller-3, stereo demodulation circuit 4, volume control circuit 5, mute circuit 6, low frequency amplifier 7, speaker 8, and PLL frequency synthesizer 9 receive in cooperation. The operation is performed, and the audio signal is reproduced by the speaker 8. This operation is the same as that of the conventional example, and the description is omitted.

The RDS information transmitted from the receiving station is R
The RDS information demodulated by the DS demodulator 10 and detected by the micro computer 11 for synchronization, synchronized, subjected to processing such as error correction, and supplied to the system micro computer 12. The system microcomputer 12 separates the AF data from the RDS information and stores the AF data in a RAM constituting a part of the system microcomputer 12.

On the other hand, the system microcomputer 12
Is supplied with the current receiving station electric field strength signal output from the intermediate frequency circuit of the intermediate frequency / detection circuit 2.
By checking whether the electric field intensity Vs corresponding to the electric field intensity signal is equal to or higher than a predetermined set electric field intensity Va, AF
It is checked whether or not a search is to be performed (step S1). As a result of this check, when it is determined that the electric field intensity Vs is lower than the set electric field intensity Va, it is determined that the AF search is to be performed, and the next AF data stored in the RAM is stored. It is read (step S2).

After step S2, a mute control signal is output to the mute circuit 6, a noise cancel stop signal is output to the noise canceller 3, and then frequency-divided data corresponding to the read AF data. The frequency divider is supplied to the variable frequency divider of the PLL frequency synthesizer 9 to set the frequency division ratio (step S3). By executing step S3, the mute circuit 6 is controlled to be in a mute state, the noise canceller 3 is controlled to be in a state in which a noise cancel operation is stopped, and the PLL frequency synthesizer 9 oscillates at a frequency corresponding to the AF data. To receive radio waves from a station having a frequency corresponding to the AF data.

In this state, the electric field strength Vs of the new receiving station is checked, and it is checked whether the electric field strength Vs is equal to or higher than the receiving station movable electric field strength Vb (step S4). As a result of the check, when it is determined that the electric field strength Vs is equal to or higher than the receiving station movable electric field strength Vb, the mute state of the mute circuit 7 is released (step S5). Following this release, a predetermined period t
When the time has elapsed (step S6), the noise canceller-3
Of the noise cancel operation stop state is released, and the noise canceller-3 is controlled to the operation state (step S).
7). Step S1 is executed following step S7.

On the other hand, in step S4, the electric field intensity Vs
Is determined to be less than the receiving station movable set electric field strength Vb, it is checked after step S4 whether or not there is still unread AF data stored in the RAM (step S8). If it is determined that there is still no AF data, step S2 is executed following step S8, and the AF search is continued.

A not read in step S8
When it is determined that the F data has been lost, that is, when RA
If the electric field strength Vs is less than the receiving station movable set electric field strength Vb even after performing the AF search over all the AF data stored in M, the AF search is performed after step S8.
The original frequency-divided data before performing the search is supplied to the variable frequency divider of the PLL frequency synthesizer 9 to return to the receiving state of the original receiving station before the AF search (step S9), and then to step S5 Is executed.

Therefore, at the time of the AF search, the noise canceler 3 stops the noise cancel operation simultaneously with the start of the mute operation of the mute circuit 6 as shown in FIG. Period t after release
The noise canceling operation state is controlled with a delay, so that the noise canceling operation is stopped during the AF search and also for the t period even after the end of the AF search. Therefore, even if noise occurs during the AF search, the noise canceller 3 does not operate during that time, so that the audio signal is not damaged by unnecessary noise canceling operation.

In the above-described embodiment, the noise canceller is controlled by the system microcomputer 12.
In the other embodiment, a mute control signal is supplied to a diode 13 for rectification as shown in FIG. 4, and a rectified DC signal is supplied to a resistor and a capacitor as shown in FIG. Supply to the time constant circuit 14 connected in parallel,
The same operation as described above is performed even when the output of the time constant circuit 14 is output as a noise canceling stop signal to control the noise canceller-3. In this manner, a hard configuration may be employed.

[0019]

As described above, according to the RDS receiver of the present invention, the noise cancellation is stopped almost at the same time as the start of the mute state during the AF search, and the mud is stopped.
Since the noise cancel stop signal for canceling the noise cancel stop state is output after a predetermined period from the release of the mute state, even if noise occurs during the AF search, the noise canceler is canceled for a predetermined period after the mute operation is canceled. −
Has been stopped, so that the audio signal is not damaged by unnecessary noise canceling operation.
There is an effect that it is not necessary to lengthen the mute period during the AF search more than necessary. Therefore, there is also an effect that the feeling of interruption of sound is eliminated, and the feeling of noise due to the malfunction of noise cancellation is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a flow chart for explaining the operation of an embodiment of the present invention.
It is a chart.

FIG. 3 is a timing chart for explaining the operation of the embodiment of the present invention;

FIG. 4 is a circuit diagram of a noise canceling stop signal generating circuit of a noise canceller constituting another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 noise canceller 6 mute circuit 9 PLL frequency synthesizer 10 RDS data demodulator 11 micro computer for synchronization 12 system micro computer

Claims (1)

(57) [Scope of request for utility model registration] An output from a detection circuit includes a mute circuit.
A noise canceller for transmitting to the next stage , and configured to be able to receive RDS information.
In a radio data system receiver capable of automatically switching a receiving station to a station having a good receiving state by searching for a mute circuit, a mute circuit is opened with the start of the search.
And the mute circuit is closed upon completion of the search.
Output the mute control signal to the mute circuit when searching.
Output mute control signal generation means and mute during search
Almost simultaneously with control to mute circuit open state by control signal
Stops the noise canceler's noise cancel operation.
And the noise is delayed for a predetermined period after the mute circuit is closed.
Signal to start the noise canceler
Noise cancel stop that outputs the signal to the noise canceller
Radio signal comprising a stop signal generating means.
System receiver.