JPH09326855A - Gain adjustment circuit for hand-free communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the gain adjustment circuit for a hand-free communication equipment without a sense of changeover between a transmission and a reception with high simultaneous speech performance by providing a loss provision means to provide a loss in response to the level of a reception signal to a transmission signal. SOLUTION: When a voice is inputted to a microphone 1, a transmission signal SS corresponding to the voice is outputted to a transmission loss circuit 6 and a changeover control circuit 5. Simultaneously when a reception signal SR is outputted from a radio reception section, the reception signal SR is simultaneously inputted to a reception signal loss circuit 3, a changeover control circuit 5 and a rectifier circuit 7. The changeover control circuit 5 converts an inputted transmission signal SS and the reception signal SR into a transmission voltage and a reception voltage and compares the both. When the reception signal SR is smaller than a prescribed level, a small loss is given to the transmission signal SS accordingly and when the reception signal SR is a prescribed level or over, a large loss is given to the transmission signal SS accordingly.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, for example, in a hands-free communication device (for example, a mobile phone) that allows a speaker to talk without using a hand, a gain adjustment for automatically adjusting each gain of a transmission signal and a reception signal. A circuit is provided. This hands-free communication device prevents a howling and an acoustic echo generated by a microphone that collects a transmitted voice, a speaker that amplifies a received voice, and a microphone that collects a received voice that is amplified by the speaker. It is composed of a gain adjusting circuit for removing.

FIG. 2 is a block diagram showing the configuration of a gain adjusting circuit in the above-mentioned conventional hands-free communication device. In the figure, reference numeral 1 is a microphone, which converts the voice of the speaker into a transmission signal SS. Reference numeral 2 is a transmission loss circuit, the gain of which is a minus gain GS or zero under the control of the switching control circuit 5 which will be described later, and when the gain is the above minus gain GS, a certain amount of loss with respect to the transmission signal SS. Is output, and this is output as a transmission signal SSS by a wireless transmission unit (not shown). Also, the above minus gain GS
Is a sufficiently large value (fixed value) to prevent acoustic echo and howling described later.

Reference numeral 3 is a reception loss circuit, the gain of which is a negative gain GR or zero under the control of the switching control circuit 5, and when the gain is the negative gain GR, it is inputted from a radio receiving section (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 value (fixed value) smaller than the minus gain-GS described above.

Reference numeral 4 denotes a speaker, which converts the received reception signal SRR into voice. The switching control circuit 5 has a rectifier and is input with the transmission signal SS and the reception signal SR.
Are rectified respectively to obtain a transmission voltage and a reception voltage corresponding to the transmission signal SS and the reception signal SR. 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 signal SK is "low", while the transmission voltage is lower than the reception voltage. In this case, the switching signal SK of "high" 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 sets the gain to the minus gain GS, gives a loss amount corresponding to this minus gain GS to the transmission signal SS, and outputs it as the transmission signal SSS. Further, the transmission loss circuit 2 sets the gain to zero when the switching signal SK is "low", so that the transmission signal SS can be transmitted without loss.
Output as (≈sending signal SS).

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

In the above configuration, when the voice of the speaker is input to the microphone 1, the microphone 1 outputs the 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 the reception signal SR is output from the radio receiving unit (not shown) of the car telephone, the reception signal SR is input to the reception loss circuit 3 and the switching control circuit 5, respectively.

As a result, the switching control circuit 5 rectifies the input transmission signal SS and the reception signal SR by converting them into the transmission voltage and the reception voltage, respectively, and then compares the transmission voltage and the reception voltage. . Now, assuming that the transmission voltage is higher than the reception voltage, the switching control circuit 5 outputs "low".
The switching signal SK of is output. As a result, the gain of the reception loss circuit 3 is set to the negative gain-GR, and accordingly, from the reception loss circuit 3, the above-mentioned negative gain-G.
The reception signal SRR that has received 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 gain of the transmission loss circuit 2 becomes zero, and therefore the transmission loss circuit 2 outputs a loss. The untransmitted transmission signal SSS (≈transmission signal SS) is output to the wireless transmission unit (not shown) of the mobile phone. That is, the level of the reception signal SRR becomes relatively smaller than that of the transmission signal SSS, so that howling and acoustic echo generated by acoustic coupling between the speaker 4 and the microphone 1 are prevented.

If the transmission control voltage is lower than the reception voltage in the switching control circuit 5, the switching control circuit 5 outputs a "high" switching signal SK. As a result, 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 with no loss (≈the reception signal SR).

On the other hand, when the "high" switching signal SK is input to the transmission loss circuit 2, the transmission loss circuit 2 has its gain set to the minus gain GS, and therefore the transmission loss circuit 2
Outputs a transmission signal SSS which has received a loss corresponding to the minus gain GS. That is, the transmission signal S
The level of SS becomes relatively smaller than the received signal SRR, so that the above-mentioned howling and acoustic echo are prevented.

[0013]

By the way, in the above-described gain adjustment circuit in the conventional hands-free communication device, the transmission signal SS or the reception signal SR is output regardless of the levels of the transmission signal SS and the reception signal SR. A certain amount of loss is added. Therefore, in the gain adjustment circuit in the conventional hands-free communication device, for example, when the above-mentioned loss is added to the reception signal SR having a very low level, the speaker 4 outputs too little sound, and the speaker transmits There was a drawback that I could not make a natural call because I felt a feeling of switching to the call. 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 telephone side talk at the same time, if the level of the reception signal SR is higher than the transmission signal SS, Since a loss is added to the transmission signal SS, there is a drawback that the simultaneous communication property 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.

[0014]

According to a 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, which is provided in the vicinity of the microphone and has a speaker for converting an input reception signal into voice, a loss that gives a loss amount corresponding to the level of the reception signal to the transmission signal. It is characterized in that it is provided with a provision means.

According to a second aspect of the present invention, in the gain adjustment circuit in the hands-free communication device according to the first aspect, a comparison means is provided for comparing the level of the received signal with a preset set value. If the level of the reception signal is higher than the set value based on the comparison result of the comparison unit, the loss giving unit gives a first loss to the transmission signal, and the reception signal Is less than the set value, the first signal is transmitted to the transmission signal.
And a second loss smaller than the loss of

The invention according to claim 3 is a hands-free device having a microphone for converting a speaker's voice into a transmission signal and a speaker provided in the vicinity of the microphone for converting an input reception signal into a voice. In the communication device, a plurality of comparing means for respectively comparing the level of the received signal and preset setting values of different predetermined widths, and the level of the received signal based on the comparison result of the plurality of comparing means. Is within a predetermined range of the set value, a loss giving means for giving a loss corresponding to the set value in the comparing means to the transmission signal is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the 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 in place of the transmission loss circuit 2 shown in FIG. 2, and a rectifier circuit 7 and a comparison circuit 8 are newly provided.

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

Further, when the "high" switching signal SK and a control signal SH which will be described later are both input, the transmission loss circuit 6 has a gain of minus gain GS. On the other hand, when only the "high" switching signal SK is input, the transmission loss circuit 6 has its gain set to the 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
Is the control signal SH when the receiving voltage VR is higher than the set voltage and the switching signal SK of "high" is input.
On the other hand, when the reception voltage VR is lower than the set voltage and the switching signal SK of "high" 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 the voice of the speaker is input to the microphone 1, the transmission signal SS corresponding to the voice is output from the microphone 1 to the transmission loss circuit 6 and the switching control circuit 5, respectively. At the same time, when a radio reception signal SR is output from the radio receiving unit (not shown) of the car telephone, the reception signal SR is input to the reception loss circuit 3, the switching control circuit 5 and the rectification circuit 7, respectively.

As a result, the switching control circuit 5 converts the input transmission signal SS and reception signal SR into the transmission voltage and the reception voltage, and then compares the transmission voltage with the reception voltage.
Now, 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 received reception signal SR and outputs the reception voltage VR. As a result, the comparison circuit 8 compares the preset voltage with the reception voltage VR. Now, assuming that the reception voltage VR is smaller than the set voltage, in other words, 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 the minus gain G1. Therefore, the input transmission signal SS is subjected to the first loss corresponding to the minus gain G1 and the transmission loss circuit 6 outputs the transmission signal SSS to the wireless transmission unit (not shown). .

Further, 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, its gain is minus gain GS.
(> Minus gain-G1). That is, the transmission loss circuit 6 outputs the transmission signal SSS which has received the second loss corresponding to the minus gain GS.

That is, according to the gain adjusting circuit in the hands-free communication device according to the embodiment of the present invention described above, 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 corresponding loss is added 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 magnitude of the reception signal SR. Since it is added, the feeling of switching between transmitting and receiving as in the conventional case is eliminated, and therefore, an effect that a call with high simultaneous communication can be performed is 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 in which one set voltage is compared with the reception voltage VR in the comparison circuit 8 has been described, but the present invention is not limited to this and many The comparator circuit may be provided.

In this case, each comparison circuit is set with a different set voltage with a predetermined voltage width, and a transmission loss circuit is provided so as to correspond to each comparison circuit and to obtain a negative gain of a plurality of stages. 6 may be configured. Therefore, according to this modified example, since a fine loss amount can be added to the transmission signal SS, the effect that the simultaneous callability can be further enhanced is obtained.

[0029]

As described above, according to the present invention, the loss amount for the transmission signal is controlled according to the level of the reception signal, so that the transmission amount is lower than that in the conventional case where the loss amount is fixed. It is possible to obtain the effect that there is no feeling of switching to the reception and the simultaneous callability is improved.

[Brief description of 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]

 1 Microphone 3 Reception loss circuit 4 Speaker 5 Switching control circuit 6 Transmission loss circuit 7 Rectifier circuit 8 Comparison circuit

Claims (3)

[Claims] 1. A hands-free communication device comprising: a microphone for converting a speaker's voice into a transmission signal; and a speaker provided in the vicinity of the microphone for converting an input reception signal into a voice. A gain adjusting circuit in a hands-free communication device, comprising: loss giving means for giving a loss amount according to the level of the received signal to a signal. 2. A comparison means for comparing the level of the reception signal with a preset setting value, wherein the loss giving means has a level of the reception signal based on a comparison result of the comparison means. Is larger than the set value,
A first loss is given to the transmission signal, and when the level of the reception signal is smaller than the set value, a second loss smaller than the first loss is given to the transmission signal. The gain adjustment circuit in the hands-free communication device according to claim 1, wherein 3. A hands-free communication device having a microphone for converting a speaker's voice into a transmission signal and a speaker provided in the vicinity of the microphone for converting an input reception signal into a voice, the reception signal And a plurality of comparing means for respectively comparing preset levels with different preset widths, and based on the comparison results of the plurality of comparing means, the level of the received signal is a predetermined width of the preset value. When within the range of
A gain adjusting circuit in a hands-free communication device, comprising: a loss giving unit that gives a loss corresponding to the set value in the comparing unit to the transmission signal.