JP2990063B2 - Gain adjustment circuit in hands-free communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gain adjustment circuit in a hands-free communication device such as an automobile telephone, which enables a speaker to make a two-way call without using a hand.

[0002]

2. Description of the Related Art Conventionally, for example, in a hands-free communication device (for example, an automobile telephone) in which a speaker can talk without using a hand, a gain adjustment for automatically adjusting each gain of a transmission signal and a reception signal is provided. A circuit is provided. This hands-free communication device has a microphone that collects a transmission voice, a speaker that loudspeaks a received voice, and a howling and acoustic echo generated when the received voice loudspeaked by the loudspeaker is collected by the microphone. And a gain adjustment circuit to be removed.

FIG. 2 is a block diagram showing a configuration of a gain adjustment circuit in the conventional hands-free communication device described above. In this figure, reference numeral 1 denotes a microphone, which converts a speaker's voice into a transmission signal SS. Reference numeral 2 denotes a transmission loss circuit whose gain is set to minus gain-GS or zero under the control of a switching control circuit 5 described later, and when the gain is minus gain-GS, a certain amount of loss with respect to the transmission signal SS. And outputs it as a transmission signal SSS by a wireless transmission unit (not shown). In addition, the above minus gain-GS
Is a value (fixed value) large enough to prevent acoustic echo and howling described below.

Reference numeral 3 denotes a reception loss circuit, whose gain is set to minus gain-GR or zero under the control of the switching control circuit 5, and when the gain is minus gain-GR, it is inputted from a radio receiving unit (not shown). A certain amount of loss is given to the reception signal SR, and this is output as the reception signal SRR. The minus gain-GR is a smaller value (fixed value) than the minus gain-GS described above.

[0005] Reference numeral 4 denotes a speaker, which converts an input reception signal SRR into voice. The switching control circuit 5 has a rectifier, and receives the input transmission signal SS and reception signal SR.
Are respectively rectified to obtain a transmission voltage and a reception voltage corresponding to the transmission signal SS and the reception signal SR, respectively. Further, the switching control circuit 5 compares the transmission voltage with the reception voltage, and when the transmission voltage is higher than the reception voltage, the switching control circuit 5 outputs a "Low" switching signal SK, and on the other hand, the transmission voltage is lower than the reception voltage. In this case, a "high" switching signal SK is output to the transmission loss circuit 2 and the reception loss circuit 3, respectively.

In the transmission loss circuit 2, the switching signal SK is "high".
At this time, a certain amount of loss is given to the transmission signal SS.
That is, at this time, the transmission loss circuit 2 has a gain of minus gain−GS, gives a loss amount corresponding to the minus gain−GS to the transmission signal SS, and outputs this as the transmission signal SSS. When the switching signal SK is "low", the transmission loss circuit 2 sets the gain of the transmission signal SS to zero, and transmits the transmission signal SS without loss to the transmission signal SS.
(≒ Transmission signal SS) is output.

On the other hand, the reception loss circuit 3 outputs the switching signal SK
When "low", a certain amount of loss is given to the reception signal SR. That is, at this time, the reception loss circuit 3 sets the gain to minus gain-GR, and sets the loss amount corresponding to this minus gain-GR to The received loss signal SR is output to the reception signal SR, and the reception loss circuit 3 sets the gain to zero when the switching signal SK is "high",
The received signal SR is output as the received signal SRR (≒ received signal SR) without any loss.

In the above configuration, when a speaker's voice is input to the microphone 1, the microphone 1 outputs a transmission signal SS corresponding to the voice to the transmission loss circuit 2 and the switching control circuit 5, respectively. . At the same time, when a reception signal SR is output from a wireless reception unit (not shown) of the automobile telephone, the reception signal SR is input to the reception loss circuit 3 and the switching control circuit 5, respectively.

Thus, the switching control circuit 5 rectifies the input transmission signal SS and reception signal SR and converts them into transmission voltage and reception voltage, respectively, and then compares these transmission voltage and reception voltage. . Assuming that the transmission voltage is higher than the reception voltage, the switching control circuit 5 issues a "low" signal.
Is output. As a result, the gain of the reception loss circuit 3 is set to minus gain-GR.
A received signal SRR having a loss corresponding to R is output to the speaker 4. As a result, a low volume sound is output from the speaker 4.

On the other hand, when the "low" switching signal SK is input to the transmission loss circuit 2, the transmission loss circuit 2 has its gain set to zero. The transmission signal SSS that has not been received (≒ transmission signal SS) is output to a wireless transmission unit (not shown) of the automobile telephone. In other words, the level of the received signal SRR is relatively smaller than the level of the transmitted signal SSS, so that howling and acoustic echo caused by acoustic coupling between the speaker 4 and the microphone 1 are prevented.

When the transmission voltage is lower than the reception voltage in the switching control circuit 5, the switching control circuit 5 outputs a "high" switching signal SK. Thus, the gain of the reception loss circuit 3 is set to zero by the operation opposite to the above-described operation, and the reception loss circuit 3 outputs the reception signal SRR (≒ reception signal SR) to which no loss is given.

On the other hand, when the "high" switching signal SK is input to the transmission loss circuit 2, the transmission loss circuit 2 has a gain of minus gain -GS, and accordingly, the transmission loss circuit 2
Outputs a transmission signal SSS having a loss corresponding to the minus gain-GS. That is, the transmission signal S
The level of SS becomes relatively smaller than the reception signal SRR, and thus the above-described howling and acoustic echo are prevented.

[0013]

By the way, in the above-described gain adjusting circuit in the conventional hands-free communication device, the transmission signal SS or the reception signal SR is applied to the transmission signal SS or the reception signal SR regardless of the levels of the transmission signal SS and the reception signal SR. A certain amount of loss is given. Thus, the gain adjustment circuit of a conventional hands-free communication device, for example, very times
When the line level is low, the speaker on the ground side is
Level of the received signal in which the above loss is added to the transmitted signal SS of
Because of the extremely small size, there is a drawback that a feeling of switching between transmission and reception is felt, and a natural call cannot be made. Therefore, in the above-described gain adjustment circuit in the conventional hands-free communication device, when the talker on the ground side and the talker on the car phone side talk at the same time, if the level of the reception signal SR is larger than the transmission signal SS, Transmission signal SS
Since the constant loss is given to, it has a drawback that simultaneous calls is impaired. The present invention has been made under such a background, and an object of the present invention is to provide a gain adjustment circuit in a hands-free communication device which does not have a feeling of switching between transmission and reception and has high simultaneous communication characteristics.

[0014]

According to the first aspect of the present invention, there is provided a microphone for converting a voice of a speaker into a transmission signal,
In a hands-free communication device provided near the microphone and having a speaker for converting an input reception signal into voice, a transmission loss that gives a loss to the transmission signal.
Loss giving means, and a reception loss for giving a loss to the reception signal.
Providing means, a level of the transmission signal and a level of the reception signal.
And the transmission signal based on the comparison result.
To give a loss according to the level of the received signal
Controlling the transmission loss applying means, or the reception signal
The receiving loss giving means is controlled so as to give a loss to
Switching control means, the transmission loss giving means,
Loss corresponding to the level of the received signal is applied to the transmitted signal.
Characterized in that it to grant.

According to a second aspect of the present invention, in the gain adjusting circuit in the hands-free communication apparatus according to the first aspect, the switching control means includes a level of the reception signal,
Based on the result of comparing with the set value
If the level of the previous SL received signal is larger than the set value, the first lost imparted to transmit signal, wherein when the level of the received signal is smaller than the set value, with respect to the transmission signal And providing a second loss smaller than the first loss.

According to a third aspect of the present invention, there is provided a hands-free microphone having a microphone for converting a speaker's voice into a transmission signal, and a speaker provided near the microphone for converting an input reception signal into voice. in the communication device, before
Transmission loss applying means for applying a loss to the recorded transmission signal;
And the reception loss assigning means for assigning loss received signal, the level of the received signal, and a plurality of comparing means for comparing each of the set values of the different predetermined width set in advance, the transmission signal
Signal level and the level of the received signal.
Based on the result, and the comparison result of the comparing means,
The level of the reception signal is within a predetermined range of the set value.
When the transmitted signal is
The transmission loss is added so that a loss corresponding to the set value is given.
Control means for giving a loss to the reception signal
Switching control means for controlling the reception loss giving means as described above,
Wherein the transmission loss providing means corresponds to the set value.
Loss to the transmission signal .

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a gain adjustment circuit in a hands-free communication device according to an embodiment of the present invention. In this figure, parts corresponding to the respective parts in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, a transmission loss circuit 6 is provided instead of the transmission loss circuit 2 shown in FIG. 2, and a rectifier circuit 7 and a comparison circuit 8 are additionally provided.

The transmission loss circuit 6 shown in FIG. 1 can be set to three kinds of gains of minus gains -GS, -G1 and zero. The above minus gain-G1
Is set to a value smaller than minus gain-GS. That is, the transmission loss circuit 6 gives the input transmission signal SS a first loss corresponding to minus gain G1 or a second loss corresponding to minus gain GR.

When both the "high" switching signal SK and a control signal SH described later are input, the gain of the transmission loss circuit 6 is set to minus gain -GS. On the other hand, when only the "high" switching signal SK is input, the gain of the transmission loss circuit 6 is set to minus gain-G1.

The rectifier circuit 7 rectifies the input reception signal SR and outputs a reception voltage VR. The comparison circuit 8 compares the input reception voltage VR with a preset voltage, and outputs a control signal SH based on the comparison result and the switching signal SK. That is, the comparison circuit 8
Indicates that when the receiving voltage VR is higher than the set voltage and the "high" switching signal SK is input, the control signal SH
On the other hand, when the reception voltage VR is smaller than the set voltage and the "high" switching signal SK is input, the control signal SH is not output.

Next, the operation of the gain adjustment circuit in the hands-free communication device according to the above-described embodiment will be described. First, when a speaker's voice is input to the microphone 1, the microphone 1 outputs a transmission signal SS corresponding to the voice to the transmission loss circuit 6 and the switching control circuit 5, respectively. At the same time, when a reception signal SR is output from a wireless reception unit (not shown) of the automobile telephone, the reception signal SR is input to the reception loss circuit 3, the switching control circuit 5, and the rectification circuit 7, respectively.

Thus, the switching control circuit 5 converts the input transmission signal SS and reception signal SR into transmission voltage and reception voltage, and then compares the transmission voltage with the reception voltage.
Assuming that the reception voltage is higher than the transmission voltage, the switching control circuit 5 outputs a "high" switching signal SK to the reception loss circuit 3, the transmission loss circuit 6, and the comparison circuit 8, respectively. .

At the same time, the rectifier circuit 7 rectifies the input reception signal SR and outputs a reception voltage VR. As a result, the comparison circuit 8 compares the previously set voltage with the reception voltage VR. Now, if the reception voltage VR is smaller than the set voltage, in other words, if the reception signal SR is smaller than a certain level,
No signal is output from the comparison circuit 8.

Therefore, when only the "high" switching signal SK is input to the transmission loss circuit 6, the gain of the transmission loss circuit 6 is set to minus gain-G1. Accordingly, the input transmission signal SS receives a first loss corresponding to the minus gain G1, and the transmission loss circuit 6 outputs the transmission signal SSS to a wireless transmission unit (not shown). .

The comparison circuit 8 outputs the control signal SH when the input reception voltage VR is higher than the set voltage, in other words, when the reception signal SR is higher than a certain level. Therefore, in this case, since the transmission loss circuit 6 receives both the "high" switching signal SK and the control signal SH, the gain thereof is minus the gain -GS.
(> Minus gain-G1). In other words, the transmission loss circuit 6 outputs the transmission signal SSS having received the second loss corresponding to the minus gain-GS.

That is, according to the gain adjustment circuit in the above-described hands-free communication device according to the embodiment of the present invention, when the reception signal SR is smaller than a certain level, a small loss corresponding thereto is added to the transmission signal SS. On the other hand, if the reception signal SR is higher than a certain level, a correspondingly large loss is given to the transmission signal SS. That is, according to the gain adjustment circuit in the hands-free communication device according to the above-described embodiment, an appropriate amount of loss (first or second loss) is generated in the transmission signal SS according to the size of the reception signal SR. As a result, the feeling of switching between transmission and reception as in the conventional case is eliminated, and therefore, an effect that a call with high simultaneous callability can be made can be obtained.

As described above, one embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention. For example, in the gain adjustment circuit in the hands-free communication device according to the above-described embodiment, an example has been described in which the comparison circuit 8 compares one set voltage with the reception voltage VR, but the present invention is not limited to this. May be provided.

In this case, different setting voltages are set in each of the comparison circuits with a predetermined voltage width, and the transmission loss circuit is set so as to correspond to each of the comparison circuits so as to have a plurality of stages of minus gain. 6 may be configured. Therefore, according to this modified example, since a fine loss amount can be given to the transmission signal SS, the effect that the simultaneous callability can be further improved can be obtained.

[0029]

According to the present invention, the amount of loss for the transmission signal is controlled in accordance with the level of the reception signal, so that the transmission loss is reduced as compared with the conventional case where the loss amount is fixed. There is an effect that there is no feeling of switching to receiving and that simultaneous callability is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a gain adjustment circuit in a hands-free communication device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a gain adjustment circuit in a conventional hands-free communication device.

[Explanation of symbols]

 Reference Signs List 1 microphone 3 reception loss circuit 4 speaker 5 switching control circuit 6 transmission loss circuit 7 rectification circuit 8 comparison circuit

Claims (3)

(57) [Claims] 1. A hands-free communication device comprising: a microphone for converting a voice of a speaker into a transmission signal; and a speaker provided near the microphone and converting an input reception signal to voice. A transmission loss applying means for applying a loss to a signal, a reception loss applying means for applying a loss to the received signal, and comparing a level of the transmitted signal with a level of the received signal.
Receiving the transmitted signal based on the comparison result
The transmission loss so as to give a loss according to the signal level.
Controlling the loss giving means or giving a loss to the received signal
Switching control means for controlling the reception loss giving means so as to perform
And a transmission loss providing means according to a level of the reception signal.
A gain adjustment circuit in the hands-free communication device , wherein the loss is added to the transmission signal . 2. The switching control means according to claim 1 , wherein
The result of comparing the bell with the preset value
Based on, when the level of the previous SL received signal is larger than the set value, and applying a first loss to the transmission signal, when the level of the received signal is smaller than the set value, the transmission The gain adjustment circuit according to claim 1, wherein a second loss smaller than the first loss is given to the signal. 3. A hands-free communication device comprising: a microphone for converting a voice of a speaker into a transmission signal; and a speaker provided near the microphone and converting an input reception signal to voice. A transmission loss applying means for applying a loss to a signal, a reception loss applying means for applying a loss to the received signal, and a level of the received signal and a set value having a different predetermined width set in advance. A plurality of comparing means for comparing a level of the transmission signal with a level of the reception signal;
Based on the comparison result and the comparison result of the comparing means.
There are, range of constant width at the level of the setting value of the reception signal
When it is in the box, the comparing means
To provide a loss corresponding to the set value
Controlling the transmission loss applying means, or
For controlling the receiving loss giving means so as to give
Control means, and the transmission loss giving means calculates a loss corresponding to the set value.
A gain adjustment circuit in the hands-free communication device, wherein the gain adjustment circuit is provided to the transmission signal .