JPH03184427A - Fm broadcasting receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Industrial Application Field" This invention frequency-modulates and broadcasts a main signal and a signal of a specific frequency outside the band of the main signal, and when broadcasting traffic information, the traffic information is transmitted to the main signal. FM for frequency modulation broadcasting in which data is superimposed on the specific frequency signal.
The present invention relates to a broadcast receiver, and particularly to means for identifying whether or not traffic information is being received.

"Prior Art" In Europe, traffic information is broadcast using FM broadcasting in which carrier waves (89.5 to 108 MHz) are frequency-modulated and broadcast using main signals such as voice and music. For this reason, a signal of a specific frequency outside the frequency band of the main signal, for example, a 57 kHz subcarrier signal, is always transmitted together with the main signal, and when broadcasting traffic information, the traffic information is broadcast as the main signal, and the specific frequency signal When the data is superimposed on the subcarrier signal, that is, the 57kllz subcarrier signal is amplitude-modulated with the 125th tone signal (data) and transmitted, and the broadcast of traffic information is stopped, the superimposition of the data is also stopped. Therefore, it is possible to know whether traffic information is being broadcast or not based on the presence or absence of the above data (tone signal). If you are listening to music on another audio device such as a cassette tape recorder or CD (compact disc) player in your car, and traffic information is received, the operation of that audio device is temporarily stopped and the FM broadcast receiver is turned off. The system automatically switches the traffic information received from the system to be broadcast from the speaker, and when the broadcast of the traffic information is finished, restarts the stopped audio equipment and returns to listening to the traffic information.

This switching is controlled by the presence or absence of data (tone signal), but if it is controlled only by the presence or absence of this data (tone signal), noise will be mistakenly detected as data (tone signal), and the switching will be performed even though traffic information is not being broadcast. There may be some inconvenience caused. From this point of view, a specific frequency signal (57k
llz subcarrier signal) and data (tone signal) are detected simultaneously, it is determined that traffic information is being broadcast.

However, due to propagation conditions of broadcast radio waves, multipath, external noise, etc., a specific frequency signal (57kHz) is transmitted during traffic information broadcast.
z subcarrier signal) and/or data (tone signal) -
Occasionally, there is a temporary interruption, and this temporal interruption causes the inconvenience that it is determined that the traffic information broadcast has ended and the broadcast is switched to another audio device.

Means for Solving the Problems J According to this invention, a specific frequency signal is detected by a specific frequency detection circuit, data is detected by a data detection circuit, and these specific frequency signal detection output and data detection output are used for traffic information identification. When a specific frequency signal detection output and a data detection output are present at the same time, an identification signal indicating that traffic information is being received is output, and while this identification signal is being sent, the specific frequency signal detection output and/or data detection output is supplied to the circuit. When the data detection output is disconnected, it continues to output an identification signal indicating that traffic information is being received for a predetermined time, and when the data detection output continues to be disconnected for a predetermined time or more, the identification signal is changed to indicate that traffic information is not being received.

"Embodiment" FIG. 1 shows an embodiment of the present invention. FM broadcast radio waves are received by antenna 11, channel selection, high frequency amplification, and FM demodulation are performed in FM reception circuit 12, and the demodulated main signal is supplied to speaker 14 through amplifier 13. Also, the subcarrier band from the FM demodulated output is filtered by the bandpass filter 1.
5, and its output is supplied to a specific frequency detection circuit 16 and a detection circuit 17. The specific frequency detection circuit 16 detects a specific frequency signal, that is, a subcarrier signal of 57 kHz, and is composed of, for example, a PLL (phase locked loop), and a signal indicating whether or not the PLL has accessed the specific frequency signal is detected. It is output as a signal indicating the presence or absence of a specific frequency signal. The subcarrier signal is subjected to AM demodulation in the detection circuit 17 , and the AM demodulation output is supplied to the data detection circuit 18 . The data detection circuit 18 selects, for example, a data frequency, that is, a tone signal of 12511z, using a filter, detects the output, converts it into a direct current, and outputs the output as a signal indicating the presence or absence of data.

The detection output SK of the specific frequency detection circuit 16 and the detection output DK of the data detection circuit 18 are supplied to the traffic information identification circuit 19, and the traffic information identification circuit engineer 9 determines whether or not traffic information is being received according to the power of both of them. The identification signal shown is outputted to the output terminal 21. That is, when the specific frequency signal detection output SK and the data detection output DK exist at the same time, the identification signal ID is set to be receiving traffic information, and in this state, both or one of the specific frequency signal detection output SK and the data detection output DK is disconnected. Even if the traffic information is being received, the identification signal 10 is set to be receiving traffic information for a predetermined time,
When the data detection output DK is turned off for a predetermined period of time or more, the identification signal! D is changed while traffic information is not being received.

Next, a specific example of the traffic information identification circuit 19 will be explained with reference to FIG. In this example, the circuit 19 is configured with a logic circuit, and the specific frequency signal detection output SK is set to a high level H when a specific frequency signal is detected (when there is a detection output).
When a specific frequency signal is not detected (when the detection output is off)
is supplied to the AND circuit 22 as a low level L, and the data detection output DK is a high level H when data is detected (when there is a detection output), and when no data is detected (when the detection output is off). AND circuit 22 as low level L
supplied to The output of the AND circuit 22 is supplied to an inverter 24 through a delay circuit 23, and the output of the inverter 24 is supplied to a NOR circuit 26 through an inverter 25. Further, the output of the AND circuit 22 is supplied to a monostable multi-by-break 27 triggered by a falling edge, the output of the monostable multi-pipe break 27 is supplied to a NOR circuit 26, and the output of the NOR circuit 26 is sent to the output terminal 21 as an identification signal. Output the ID.

For example, as shown in FIG. 3, in the state A, the specific frequency signal detection output SK and the data detection output DK exist at the same time, that is, the output of the AND circuit 22 becomes a high level I4, and this , the delay circuit 23, and the inverter 24.25 to the NOR circuit 26, and the identification signal +D at the output terminal 21 becomes low level L, indicating that traffic information is being received.The specific frequency signal detection output SK and the data detection output DK are At the same time, when the output of the AND circuit 22 becomes low level L, the monostable multi-by-break 27 is triggered by the fall at this time, and its output is output for a time T,
For example, it is at a high level H for 1.5 seconds, and during this time, the output [D of the NOR circuit 26 remains at a low level L. Note that there is a delay between when the monostable multi-by-break 27 is triggered and when its output becomes high level H, but since the delay amount of the delay circuit 23 is said to be larger than the delay, the rise of the output of the AND circuit 22 is delayed. Continuing from the descent, T time is NOR circuit 26
The output ID of is still low and remains at health L. After the time T, the output of the monostable multi-pipe lake 27 becomes low and becomes a low level L, and the NOR circuit 26 has a low level L as well as the meat input, so its output ID becomes a high level 11, and the identification signal! D indicates that traffic information is not being received.

As in the state shown in FIG. 3B, when the detection outputs SK and DK are present at the same time (high level H at the same time) and the specific frequency detection output SK is temporarily interrupted (low level L) due to erroneous detection,
Since the monostable multipipe rake 27 is triggered by the fall of the output of the AND circuit 22 at that time, if the time of this false detection is 7 hours or less, even if the detection output SK is momentarily interrupted, the output of the NOR circuit 26 is low level! , the traffic information is being received is output, and there is no malfunction. Similarly, even if the data detection output DK is temporarily interrupted due to an erroneous detection while the detection outputs SK and DK are present at the same time, as in the state shown in FIG. is maintained.

FIG. 4 shows an example in which the traffic information identification circuit 19 is constructed from an analog circuit. The configuration of this example will be described while explaining the operation. A specific frequency signal detection output SK is supplied to the input terminal 28. It is assumed that this detection output SK becomes high when a specific frequency signal is detected, and becomes low when not detected. This detection output SK is supplied to the base of a transistor 29 as a switching element, and the detection output S
When K is at a high level, transistor 2♀ is turned on, and its collector becomes approximately ground potential, and the charge in capacitor 31 is discharged through diode 32 and further through transistor 29, and the voltage of capacitor 31 becomes approximately ground potential, and this and the threshold voltage E are compared by the comparator 33, and the output of the comparator 33 becomes a low level. Since this low level is applied to the base of the transistor 34 as a switching element, the transistor 34 is turned off, and this transistor The base of the transistor 35 as a switching element is not grounded through the transistor 34.

In other words, normally the specific frequency signal is always received, the specific frequency signal detection output SK is always obtained, and the transistor 34
is in the off state.

Data is only received when traffic information is being broadcast, in this example:
This data detection output DK is inverted and supplied to the input terminal 36. Therefore, the input terminal shall be at a low level when data is detected, and shall be at a high level when no data is detected at the data acid. When no data is detected, a high level is applied from the input terminal 36 to the base of a transistor 38 as a switching element through a resistor 37, turning on the transistor 38, discharging the capacitor 39 through the transistor 38, and reducing the voltage of the capacitor 39. The voltage becomes lower than the threshold voltage E2, and the output of the comparator 41 that compares these becomes a low level. This low level is supplied to the base of the transistor 35, the transistor 35 is turned off, and the collector of the transistor 35 becomes a high potential. , is supplied to the output terminal 21, that is, the identification signal ID is at a high level, indicating that traffic information is not being received.

In this state, when traffic information is broadcast and data is received, the data detection output DK goes high and the input terminal 36
is at a low level, transistor 3 is turned off, capacitor 39 is charged through resistor 42, and the voltage of capacitor 39 gradually increases. Data detection output D
When K is obtained continuously for a predetermined time or more, the capacitor 39
voltage becomes higher than the threshold voltage E2, the output of the comparator 41 becomes high level, the detection output SK exists, and the transistor 34 is off, so the transistor 35
is turned on, the collector voltage of the transistor 35 drops to approximately the ground potential, and the identification signal ID at the output terminal 21 becomes low level, indicating that traffic information is being received.

In this state, that is, in a state where both detection outputs SK and DK are present, if the detection output SK is turned off, the transistor 2
9 is turned off, diode 32 is reverse biased, capacitor 31 is charged through resistor 43, and the voltage on capacitor 31 gradually increases. When the detection output SK recovers while this voltage does not exceed the threshold voltage E, the transistor 29 is turned on again, the voltage of the capacitor 31 decreases, and the output of the comparator 33 remains at a low level. However, if the disconnection of the detection output SK continues for more than a predetermined time,
When the voltage of the capacitor 31 exceeds the threshold voltage E, the output of the comparator 33 becomes high level, and the transistor 34 is turned on.
The base potential of is lowered, the transistor 35 is turned off, the output terminal 21 becomes high potential, and the identification signal ID indicates that traffic information is not being received.In other words, while the detection outputs SK and DK are both present, the detection output SK Even if the start time is interrupted due to erroneous detection, the identification signal ID is held while receiving traffic information.

If the detection output DK is disconnected while both the detection outputs SK and DK are present, the input terminal 36 becomes a high level, and at this time, the output terminal 21 is at a low level. A current that charges the capacitor 45 flows toward the output terminal 21 through the capacitor 45, and the base potential of the transistor 38 gradually increases. If the input terminal 36 becomes low level again before this base potential exceeds the emic potential of the transistor 38,
Transistors 46 and 47 as switching elements are immediately turned on, shorting the capacitor 45 and discharging its charge. Therefore, when the input terminal 36 becomes high level again, the capacitor 45 is charged and the base potential of the transistor 38 gradually rises. When the input terminal 36 remains at a high level for a predetermined period of time or more, the base potential of the transistor 38 exceeds its straw ivy potential, and
This transistor 38 is turned on, the output of the comparator 41 becomes low level, and the transistor 35 is turned off.
The output terminal 21 becomes high level, and the identification signal fD indicates that traffic information is not being received. In other words, rain detection output SK,
Even if the data detection output DK is interrupted at the start time while both DKs are present, the identification signal ID is retained during traffic information reception.

According to the circuit shown in FIG. 4, when the rain detection outputs SK and DK are present, the period for holding the identification signal in the traffic information receiving state in response to a momentary interruption of one of them is longer than the capacitor 31 for the detection output SK. It is determined by the time constant of the resistor 43 and the detection output D
K is determined by the time constants of the resistor 37 and capacitor 45, and these times can be selected depending on the characteristics of each signal. Transistor 34, 35.46
Comparators can also be used instead of .

As yet another example of the traffic information receiving fIs19, it may be processed by a microcomputer.

In other words, the rain detection outputs SK and DK are manually inputted to a microcomputer, and the microcomputer inputs the detection output SK manually, and when it continues for a predetermined time, it is determined that the detection output SK is present, and the detection output DK is input in the same way. If the time continues, it is determined that the detection output DK is present, and when both determination outputs are obtained at the same time, the identification signal ID is output as a low level (receiving traffic information), and in this state, the detection output SK is disconnected. Then, if the interruption continues for a predetermined time or more, the identification signal ID is output as a high level (traffic information not being received),
Similarly, when the detection output DK is disconnected and the disconnection continues for a predetermined period of time or more, the identification signal ID is set to a high level.

"Effects of the Invention" As described above, according to the present invention, the specific frequency signal detection output SK and the data detection output DK can be obtained simultaneously, and the detection output S
Even if one or both of K and DK is disconnected, unless the disconnection continues for a predetermined period of time, the identification signal will not indicate that traffic information is not being received, so the detection output SK, due to multipath, external noise, etc. Even if the DK is temporarily disconnected, there is no risk of switching to the audio equipment side while receiving traffic information.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a logic circuit diagram showing an example of the traffic information identification circuit 19, FIG. 3 is a waveform diagram showing an example of its operation, and FIG. 4 is a traffic information identification circuit. 3 is a connection diagram showing another example of the identification circuit 19. FIG.

Claims (1)

[Claims] (1) Frequency-modulated broadcasting of a main signal and a signal of a specific frequency outside the band of the main signal, and when broadcasting traffic information, broadcast the traffic information as the main signal and superimpose data on the specific frequency signal. A receiver for frequency modulation broadcasting, comprising a specific frequency detection circuit for detecting the specific frequency signal, a data detection circuit for detecting the data, an output of the specific frequency detection circuit, and an output of the data detection circuit. When the specific frequency signal detection output and the data detection output are present at the same time, an identification signal indicating that traffic information is being received is output, and while this identification signal is being sent, the specific frequency signal detection output and/or the data When the detection output is cut off, the identification signal indicating that the traffic information is being received continues to be output for a predetermined period of time, and when the data detection output continues to be cut off for a predetermined period of time or more, the identification signal is changed to indicate that the traffic information is not being received. An FM broadcast receiver comprising an identification circuit and the following.