JPH06334458A - Radio receiver - Google Patents

Abstract

PURPOSE:To reduce a high frequency noise such as multi-path when an FM radio program is received. CONSTITUTION:A switching circuit 9 is turned on by an output of a control circuit 8 in modes such as an AM radio mode and a CD mode other than an FM radio mode, a capacity of C1+C2 is connected to an electronic attenuator 4 and a signal having a usual loudness characteristic is obtained. In the FM mode, the switching circuit 9 is turned off and only the capacity of C1 is connected to the electronic attenuator 4 and a median of a high loudness frequency is shifted toward high frequencies and a gain nearly 10kHz is reduced to reduce the effect of multi-path noise or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiving device in an on-vehicle audio device or the like.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional radio receiver. In the figure, 1 is an antenna, 2 is an FM front end, and 3 is an I output from the FM front end 2.
IF / NK to detect F signal and demodulate to audio signal
/ MPX circuit, 4 is an electronic attenuator for controlling the level of the audio signal, 5 is an amplifier for amplifying the audio signal, 6 is a speaker, and 7 is a control including a PLL circuit for tuning the FM front end 2 to a desired frequency. The circuit, C3, is a capacitor that determines the center value of the high frequency loudness frequency of the electronic attenuator 4.

The electronic attenuator 4 uses an integrated circuit. For example, a TA8184P type stereo volume / tone control IC manufactured by Toshiba Corporation (Toshiba "TOSHIBA integrated circuit technical data" TA8184) is used.
P., 1990-12-7)). This IC is
System IC with loudness control added to volume / balance / treble / bass control to turn on loudness. You can turn it off and adjust the loudness amount. Further, a control method using a DC voltage is used. The capacitor C3 determines the center value of the high range loudness frequency of this IC.

Next, a description will be given together with the loudness characteristic diagram of FIG. FIG. 4 is a graph of frequency characteristics when the volume is set to MAX and frequency characteristics when the volume is decreased by −20 dB from the time of the volume MAX. At a sound volume of -20 dB, the normal loudness characteristic raises the 6 dB level when the standard is 10 kHz and 1 kHz. When noise of a high frequency component is received during FM radio reception, the noise is very loud and the noise sound is heard well because the 6 dB level is high. The noise in the case of this FM reception is mostly multipath noise, and this frequency component is mainly 5 kHz to 20.
kHz.

[0005]

Since the conventional radio receiving apparatus is configured as described above, when receiving FM broadcasting, if noise of high frequency components such as multipath noise is received, the sound is lost. There was a problem that it was difficult to hear.

The present invention has been made to solve the above problems, and an object thereof is to reduce noise of high frequency components such as multipath noise during FM radio reception.

[0007]

A radio receiving apparatus according to the present invention comprises a high frequency range loudness characteristic moving means for moving the high frequency range loudness characteristic to a higher frequency side.

Further, the high frequency range loudness characteristic moving means which operates when the FM radio mode is selected is provided.

Further, the high frequency range loudness characteristic moving means for moving the high frequency range loudness characteristic to the higher frequency side in accordance with the decrease in volume is provided.

[0010]

In the radio receiving apparatus according to the present invention, when at least the FM radio mode is selected, the high band loudness characteristic moving means can be activated to move the high band loudness characteristic to the higher band side.

When the FM radio mode is selected, the loudness characteristic moving means is operated to move the high frequency loudness characteristic to the higher frequency side.

Further, the high range loudness characteristic is moved to the higher range side as the volume decreases.

[0013]

EXAMPLES Example 1. An embodiment of a radio receiving apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram when applied to a vehicle-mounted radio receiver. In the figure, 1 is an antenna, 2 is an FM front end, 3 is F
The IF signal output from the M front end 2 is detected,
IF / NK / MPX circuit for demodulating audio signals, 4
Is an electronic attenuator for controlling the level of the audio signal, 5 is an amplifier for amplifying the audio signal, 6 is a speaker, 8 is a control circuit including a PLL circuit for tuning the FM front end 2 to a desired frequency.
In modes other than the mode, the switching circuit 9 is set to “High”, F
In the M mode, a "Low" signal is output.

The electronic attenuator 6 is described as using a conventional TA8184P type stereo volume / tone control IC manufactured by Toshiba Corporation.

C1 and C2 are capacitors that determine the center value of the high-range loudness frequency of the electronic attenuator 4. In modes other than FM, the control circuit 8 sends a control signal of "H" to cause the switching circuit 9 to operate. Is turned on, and the capacitance of the capacitor that determines the center value of the high frequency loudness frequency of the electronic attenuator 4 is C
It becomes 1 + C2. C1 + C2 is set almost equal to C3. In the FM mode, the control circuit 8 sends a control signal of "L" to turn off the switching circuit 9 and release the capacitor C2 from the circuit to determine the center value of the high frequency loudness frequency of the electronic attenuator 4. The capacity of the existing capacitor is only C1.

Next, the description of the loudness characteristic of FIG. 2 will be made together. FIG. 2 is a graph of frequency characteristics when the volume is set to MAX and frequency characteristics when the volume is decreased by −20 dB from the time of the volume MAX. When receiving high-frequency noise such as multipath noise during FM radio reception at a volume of -20 dB, the conventional circuit has a high noise level of 6 dB at 10 kHz with reference to 1 kHz. However, only in the FM mode, the capacitance of the capacitor is switched from C1 + C2 (which is almost equal to C3) to C1 to move the center value of the high frequency loudness frequency from 10 kHz to 30 kHz.

As a result, the level at 10 kHz becomes
From + 6dB in case of 1kHz reference, + 0.5dB
Noise of high frequency components such as multipath noise is reduced. This +0.5 dB is a measured value.

Example 2. In the first embodiment, when the FM radio mode is selected, the switching circuit 9 automatically switches the capacitors C1 + C2 and C1.
When the radio mode is selected, the capacitors may be switched separately. This circuit is provided with a manual switch in parallel with the switching circuit 9. When this manual switch is OFF, the same operation as that of the first embodiment is performed, and when it is ON, C1 + C2 is reached, and the high frequency loudness characteristic does not move, so that multipath noise and the like are prevented Available when there are few.

Example 3. Further, in the AM radio mode and the CD mode other than the FM radio mode, high frequency noise generated from the factory or high frequency noise from the train line may be received. In this case, the high-range loudness characteristic moving means may be operated in a mode other than the FM radio mode. In this case, the circuit is disengaged from the control circuit 8, the switching circuit 9 is omitted, and the capacitor C alone is used.
You may make it switch 1 + C2 and C1.

Example 4. In the above-described embodiment, the movement of the high-range loudness characteristic is switched in two stages by using the capacitors C1 and C2, but the capacitors are increased and the electrostatic capacitances are switched in multiple stages so that the high-range loudness characteristics are sequentially moved. You may Further, the capacitor may be made to have a variable capacity and continuously moved to the high frequency side.

Example 5. The multi-step switching or continuous switching of the fourth embodiment may be interlocked with the volume adjusting volume. That is, when the volume is about -10 dB, the influence of noise is relatively small. Therefore, it is more natural for human hearing to shift gradually to a high frequency band without shifting to a high frequency band at a time. Therefore, it is advisable to shift the high-range loudness characteristics to the high-range side in sequence as the volume decreases.

Embodiment 6. Further, the means for changing the high-frequency loudness characteristic according to the volume of the fifth embodiment and the means for switching the first and second embodiments may be used in combination to allow arbitrary selection.

Example 7. In the first embodiment, in order to change the loudness characteristic by using the electronic attenuator, the center value of the high frequency loudness frequency is changed as shown in FIG. 2, but there are other circuits that have the loudness characteristic, and it is not always the center value. Instead of moving the value, it is sufficient to satisfy the characteristic that the gain increases as the frequency becomes higher (matching human hearing). That is, any means may be used as long as the loudness characteristic in the high frequency range is moved to the high frequency side.

[0024]

As described above, according to the present invention, the high-range loudness characteristic moving means is provided so that the high-range loudness characteristic can be moved to the higher frequency side. Area noise can be reduced.

When the FM radio mode is selected, the loudness characteristic moving means is activated.
When the M radio mode is set, the high frequency loudness characteristic is automatically moved to the higher frequency side, and high frequency noise such as multipath noise can be reduced.

Further, since the high-frequency loudness characteristic moving means for moving the high-frequency loudness characteristic to the higher frequency side in accordance with the decrease in the volume is used, it is possible to reduce the high-frequency noise such as multi-pass noise depending on the volume. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a radio receiving apparatus of the present invention.

FIG. 2 is a frequency characteristic diagram showing the loudness characteristic of the radio receiving apparatus of the present invention.

FIG. 3 is a block diagram showing a conventional radio receiver.

FIG. 4 is a frequency characteristic diagram showing a loudness characteristic of a conventional radio receiving apparatus.

[Explanation of symbols]

 1 Antenna 2 FM Front End 3 IF / NK / MPX Circuit 4 Electronic Attenuator 5 Amplifier 6 Speaker 7 Control Circuit 8 Control Circuit 9 Switching Circuit 10 High Range Loudness Characteristic Moving Means

Claims (4)

[Claims] 1. A radio receiving apparatus having modes such as FM radio, AM radio, and CD, and having a loudness characteristic as an acoustic characteristic, a high-range loudness characteristic moving means for moving the high-range loudness characteristic to a higher frequency side. Radio receiver equipped. 2. A radio receiving device having modes such as FM radio, AM radio, and CD, and having a loudness characteristic as an acoustic characteristic, comprising a high-range loudness characteristic moving means for moving the high-range loudness characteristic to a higher frequency side. A radio receiving apparatus comprising: the high frequency range loudness characteristic moving means operable at least when the FM radio mode is selected. 3. A radio receiving apparatus having modes such as FM radio, AM radio, and CD, and having a loudness characteristic as an acoustic characteristic, further comprising a high-range loudness characteristic moving means for moving the high-range loudness characteristic to a higher frequency side. Prepare, above F
A radio receiving apparatus, characterized in that, when the M radio mode is selected, the high band loudness characteristic moving means is operated. 4. The high-frequency loudness characteristic moving means is means for moving the high-frequency loudness characteristic to a higher frequency side in response to a decrease in sound volume. Radio receiver.