JPH09205480A - Connection system for portable telephone and hand-free equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection system for a portable telephone and a hand- free equipment capable of transmitting voice signals between a portable telephone set and a hand-free communication equipment without being affected by external noise. SOLUTION: In this connection system for connecting the portable telephone 1 and the exterior hand-free equipment 7, the portable telephone 1 and the hand-free equipment 7 are respectively provided with pulse width modulation circuits 12 and 14 for modulating and outputting electric voice signals from the portable telephone set 1 and the hand-free equipment 7 and pulse width demodulation circuits 13 and 15 for demodulating and inputting the electric voice signals from the portable telephone 1 and the hand-free equipment 7. Thus, the electric voice signals are transmitted between the portable telephone 1 and the hand-free equipment 7 by pulse width modulation signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hands-free use of a mobile phone in an automobile or the like, and more particularly to an electric connection system between the mobile phone and an external hands-free device.

[0002]

2. Description of the Related Art Conventionally, an electric voice signal is exchanged between a mobile phone and a hands-free device by using a so-called analog signal, which is a voice signal directly converted into an electric signal. For example, FIG. 4 is a block diagram showing a conventional example of connection between a mobile phone and a hands-free device. In FIG. 4, a voice signal from a hands-free microphone 39 is amplified by a microphone amplifier 38 and then the mobile phone 3
1 is transmitted. On the other hand, the base signal output from the speaker is transmitted as a voice signal from the mobile phone 31, amplified by the speaker amplifier 41, and output from the speaker 40.

[0003]

In the prior art, since the signal transmission between the mobile phone and the hands-free device is performed as an analog signal, when noise from the surroundings is mixed in the transmission line, There is a problem that the call quality is deteriorated by this noise. Especially when connecting a mobile phone and a hands-free device in a car,
Ignition noise from the car engine,
Noise from the motor that rotates the fan of the air conditioner, noise from the motor that drives the wiper, etc. often enter the line that connects the mobile phone to the hands-free device, impairing call quality.

FIG. 5 shows an example of this with a waveform.
In FIG. 5, (a) is an example of a voice signal waveform, but if the noise shown in (b) is mixed in this signal, a waveform in which both are added is obtained as in (c), which is the same as in the conventional technique. It is output from the speaker 40 of No. 4 or is transmitted to the base station by the wireless unit 32, and as a result, the call quality is deteriorated.

In order to prevent this, a special cable with a shield is used for connection between the mobile phone and the hands-free device, and in order to shorten the wiring, for example, the hands-free device placed in the trunk of a car is used. There were cases where special installation work was required, such as arranging in a narrow vehicle compartment.

An object of the present invention is to provide a connection system between a mobile phone and a hands-free device that can transmit a voice signal between the mobile phone and the hands-free communication device without being affected by external noise. .

[0007]

According to the present invention, in a connection system for connecting a mobile phone and an external hands-free device in a mobile phone terminal, the mobile phone and the hands-free device are respectively connected to the mobile phone. And a pulse width demodulation circuit for modulating and outputting an electric voice signal from the hands-free device, and a pulse width demodulation circuit for demodulating and inputting an electric voice signal from the mobile phone and the hands-free device. There is provided a connection system between a mobile phone and a handsfree device, which is characterized in that the transmission of an electric voice signal between the telephone and the handsfree device is transmitted by a pulse width modulation signal.

Further, according to the present invention, the portable telephone switches whether to output the voice signal to the hands-free device side or the receiver side in the downlink voice signal system from the base station, and to the base station. A mobile phone and a handset having a switch circuit for recognizing and switching between an audio signal from a microphone of the mobile phone and an audio signal from the handsfree device in an upstream audio signal system. A connection system with a free device can be obtained.

Further, according to the present invention, the portable telephone has an audio processing unit for performing processing such as volume adjustment of an audio signal sent from the base station and an audio signal sent to the base station. It is possible to obtain a connection system between a mobile phone and a hands-free device, which is characterized in that

[0010]

In the connection system between the mobile phone and the hands-free device of the present invention, since the pulse width modulation that does not have information amount in the amplitude component is used for signal transmission, the influence of the amplitude component of noise mixed from the outside is affected. It can be removed.

[0011]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, with respect to the downlink voice signal from the base station, the signal demodulated by the radio unit 2 in the mobile phone 1 is subjected to processing such as volume adjustment in the voice processing unit 3 and input to the switch circuit 4. . The switch circuit 4 switches between outputting the voice signal to the receiver 5 in the mobile phone 1 or the handsfree device 7. When the handsfree side is selected, the signal is input to the pulse width modulation circuit 12. The modulated output is sent to the hands-free device 7 and input to the pulse width demodulation circuit 15, where it is converted into a voice (analog) signal again,
It is amplified by the speaker amplifier 11, is output from the speaker 10, and reaches the user's ear.

On the other hand, as for the upstream voice, the voice uttered by the user is converted into an electric signal by the microphone 9, and the output of the microphone itself is generally very small and difficult to handle, so that it is amplified by the microphone amplifier 8 and pulse width modulated. It is input to the circuit 14. The signal modulated by the pulse width modulation circuit 14 is sent from the hands-free device 7 to the mobile phone 1, converted into an audio signal by the pulse width demodulation circuit 13, and then enters the audio processing unit 3 via the switch circuit 4. Further, it is converted into a radio signal by the radio unit 2 and transmitted to the base station. Similar to the downlink signal, the switch circuit 4 switches the signal from the microphone 6 inside the mobile phone 1 and the signal from the hands-free device 7 with respect to the uplink signal, so that the mobile phone call or the hands-free call is not performed. Depending on the above, either one of the upstream signal and the downstream signal is selected and switched.

The noise removing operation in this embodiment will be described below. 2 is a hands-free device 7 of FIG.
The waveform shown in FIG. 2A is an example in which noise is mixed between the pulse width modulation circuit 14 and the pulse width demodulation circuit 13 of the mobile phone 1. The waveform shown in FIG. 14 is an input signal waveform, and (b) is its output waveform. Here, if noise similar to that in FIG. 5B is mixed into the signal in FIG. 2B, the combined waveform is as shown by the solid line in FIG. 2C.

FIG. 3 shows an embodiment of the pulse width demodulation circuit. In FIG. 3, one input terminal of the comparator 21 is connected with the pulse width modulation signal and the other input terminal is converted into a rectangular wave. A bias power source 22 that determines a threshold voltage for conversion is connected to form a rectangular wave conversion circuit. This threshold voltage is shown by the alternate long and short dash line in FIG. 2C. If the voltage of the solid line is higher than the alternate long and short dash line, the comparator 21 of FIG. 3 outputs a high level, and the solid line of FIG. If it is low, the comparator 21 of FIG. 3 outputs a low level, so the output waveform of the comparator 21 is as shown in FIG.
Noise effects are excluded.

The reproducing operation from the rectangular wave of FIG. 2 to the audio signal will be described. The average value of the input signal is taken out by the time constant of the resistor 23 and the capacitor 24, and even with such a simple circuit, if the time constant is set to be sufficient compared with the frequency of the pulse width modulated wave. ,
Sufficient performance can be obtained very inexpensively, and this is a feature of the present invention that employs pulse modulation / demodulation.

[0016]

As described above, according to the present invention,
By transmitting a pulse width modulated signal between the mobile phone and the hands-free device, the influence of noise mixed from the outside can be reduced. Therefore, the wiring between the mobile phone and the hands-free device can be easily performed, and special installation work can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing mutual connection of a mobile phone and a hands-free device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing the operation and effect of the present invention.

FIG. 3 is a diagram showing an embodiment of a pulse width demodulation circuit of the present invention.

FIG. 4 is a block diagram showing a mutual connection of a conventional mobile phone and a hands-free device.

FIG. 5 is a waveform diagram showing the influence of noise in the related art.

[Explanation of symbols]

 1 Mobile Phone 2 Radio Section 3 Voice Processing Section 4 Switch Circuit 5 Receiver 6 Microphone 7 Hands-Free Device 8 Microphone Amplifier 9 Microphone 10 Speaker 11 Speaker Amplifier 12 Pulse Width Modulation Circuit 13 Pulse Width Demodulation Circuit 14 Pulse Width Modulation Circuit 15 Pulse Width Demodulation Circuit 21 Comparator 22 Bias power supply 23 Resistor 24 Capacitor

Claims (3)

[Claims] 1. A connection method for connecting a mobile phone and an external hands-free device in a mobile phone terminal, wherein an electrical voice from the mobile phone and the hands-free device is supplied to the mobile phone and the hands-free device, respectively. A pulse width modulation circuit that modulates and outputs a signal and a pulse width demodulation circuit that demodulates and inputs an electric voice signal from the mobile phone and the handsfree device are provided, and between the mobile phone and the handsfree device. A connection method between a mobile phone and a hands-free device, which is characterized in that electric voice signals are transmitted by pulse width modulation signals. 2. The mobile phone switches whether to output a voice signal to the hands-free device side or the receiver side in a downlink voice signal system from a base station, and the mobile phone sets the voice signal to the base station in an uplink voice signal system to the base station. The mobile phone according to claim 1, further comprising a switch circuit for recognizing and switching between a voice signal from a microphone of the mobile phone and a voice signal from the handsfree device. Connection method with the device. 3. The mobile phone has an audio processing unit for performing processing such as volume adjustment of an audio signal sent from the base station and an audio signal sent to the base station. A connection system between the mobile phone according to claim 2 and a hands-free device.