JPH1075283A - Portable terminal equipment for communication and noise reducing system therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a portable terminal equipment for communication by which reception voice is prevented from being difficult to hear in an adjacent area before an RSSI (reception electric field intensity display) signal value is reduced to be a prescribed value in addition to the attainment of noise reduction, and to provide the noise reducing system therefor. SOLUTION: This equipment is provided with RSSI signal discriminating means 16 and 18 for discriminating the size of an RSSI signal when the communication portable terminal receives transmission from another communication portable terminal, SAT signal detecting means 18 and 20 for detecting a SAT signal, voice decay means 22 and 24 for decaying a reception voice level and a control means 18 controlling the voice decay means 22 and 24 so as to execute the decay of a first stage concerning the reception voice level before the RSSI signal value becomes equal to below the prescribed value (F) in the course of reduction (B) and to execute the decay of the second stage when the RSSI signal value is reduced so as to disenable detecting the SAT signal (P).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable communication terminal such as a cellular (cellular phone) or a PHS (simplified portable telephone), and more particularly to a communication portable terminal for reducing noise during a call and its noise. It relates to a reduction method.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 3, when the intensity of a received radio wave (reception electric field intensity) becomes smaller than a sensitivity point F, noise increases, and noise such as "Za" is heard. I feel very noisy when talking about.

For this reason, as a conventional method for reducing noise during a telephone call of a mobile phone, a reception field strength indication signal (RSSI) output from a receiving section of the mobile phone on the receiving side and indicating the strength of a received radio wave is received. As shown in FIG. 4, the received signal level is greatly attenuated before the received signal intensity becomes less than or equal to a predetermined value (sensitivity point F) in the process of decreasing the received electric field intensity, as shown in FIG. Even if it becomes considerably smaller than the point F, the noise (noise) can be reduced.

[0004]

Since the RSSI signal indicates the intensity of the received radio wave, the ratio of noise is large below the sensitivity point (point F in FIGS. 3 and 4) at which the radio wave becomes very weak. In addition, the elements and circuits do not function due to the so-called saturation, and the intended circuits cannot perform the operation of attenuating the received sound level. Therefore, as shown in FIG. 4, the circuit must perform an operation of attenuating the received voice level before the RSSI signal value decreases to the sensitivity point F.

However, up to the sensitivity point F, the RSSI
There is not much noise in the vicinity before the signal value decreases, and the situation does not hinder the call.
For this reason, if the RSSI signal value rises or falls so as to enter or leave the area in the transition period while the RSSI signal value is decreasing during a call, the received voice level is greatly attenuated or returned to the original level. There is a problem that the sound level changes greatly due to unstable and so-called chattering phenomena, so that the sound volume greatly fluctuates, and the received sound becomes very difficult to hear.

Accordingly, the present invention provides not only a noise reduction but also a communication communication which can prevent a received voice from being difficult to hear in a region near an RSSI signal value dropping to a predetermined value. An object of the present invention is to provide a mobile terminal and a noise reduction method thereof.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an RSSI signal for determining the magnitude of an RSSI signal when a communication portable terminal receives a transmission from another communication portable terminal. Determining means for detecting an SAT signal;
AT signal detecting means, sound attenuating means for attenuating a received sound level, and a first step of reducing the received sound level before the RSSI signal value becomes smaller than a predetermined value.
And control means for controlling the voice attenuating means so as to perform a second-stage attenuation when the RSSI signal value becomes small and the SAT signal cannot be detected anymore. Things.

According to the communication portable terminal having such a configuration, when the communication portable terminal receives a transmission from another communication portable terminal, the communication portable terminal determines the magnitude of the RSSI signal and detects the SAT signal. When the RSSI signal value is reduced and the received voice level is attenuated in the first stage just before the RSSI signal value becomes equal to or less than a predetermined value, and when the RSSI signal value further decreases and the SAT signal cannot be detected. By performing the second-stage attenuation on the received voice level, the noise of the received voice during a call can be reduced stepwise.

Therefore, when the received voice level is attenuated in the first stage before the RSSI signal value becomes smaller than a predetermined value in the course of decreasing, the degree of attenuation of the received voice level is reduced by the conventional noise reduction method. By making the number smaller, it is possible to prevent the received sound from being difficult to hear even when the volume slightly rises or falls due to the attenuation of the received sound level.

[0010] The RSSI signal value is further reduced and the noise becomes intense. At the RSSI value at which the SAT signal cannot be detected, the received audio level is attenuated in the second stage, whereby such RSSI signal is reduced.
It is possible to reliably reduce noise that hinders communication in a region where the value falls below the I value.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 and FIG. 2 are diagrams showing a first embodiment of a communication portable terminal and its noise reduction system according to the present invention.

FIG. 1 is a diagram showing a circuit configuration of a communication portable terminal such as a cellular phone or PHS according to the first embodiment. The mobile communication terminal shown in FIG. 1 includes an antenna 12 for performing radio communication with a base station (not shown) by radio waves.
Having. The antenna 12 includes a mobile phone receiving circuit 14.
The mobile phone receiving circuit 14 demodulates the modulated radio signal transmitted from the base station, outputs a demodulated signal, and outputs an RSSI signal and an SAT signal.

The RSSI signal is a signal indicating the received electric field strength, that is, a signal indicating the strength of the received radio wave.
The SAT signal is a supervisory (monitoring) audio tone signal, and this SAT signal is one of the reference signals for knowing the received electric field strength.

[0014] The SAT signal originally monitors the communication state between the base station and the terminal, and when the communication portable terminal moves away from the base station and the communication state deteriorates, another SAT signal closer to the destination is used. It is used for discrimination when transferring a line to a base station. The SAT signal is used based on a car telephone system such as J-TACS using an analog signal.

RS output from the mobile phone receiving circuit 14
The SI signal is input to an RSSI signal amplifying circuit 16 for amplifying the SI signal, and the RSSI signal amplified by the RSSI signal amplifying circuit 16 is supplied to a control circuit (control unit, RS means).
(SI signal discriminating means) 18.

The SAT signal output from the mobile phone receiving circuit 14 is input to an SAT signal detecting circuit (SAT signal detecting means) 20, and the SAT signal detecting circuit 20
The detection signal of the AT signal is input to the control circuit 18.

On the other hand, the demodulated signal output from the portable telephone receiving circuit 14 is supplied to a gain switching circuit (speech attenuating means) 22,
The signal is input to a speaker 26 via a voltage variable attenuator circuit (voice attenuation means) 24. The control circuit 18 controls the operation of the voltage variable attenuator circuit 24 based on the fluctuation of the signal from the RSSI signal amplification circuit 16 or controls the operation of the gain switching circuit 22 based on the fluctuation of the signal from the SAT signal detection circuit 20. Control.

Next, a description will be given of a noise reduction method in the operation of the communication portable terminal having the above configuration. When your mobile device receives a transmission from another mobile device,
When the control circuit 18 determines from the RSSI signal from the RSSI signal amplification circuit 16 that the received electric field strength is larger than the value B slightly larger than the sensitivity point F at which the received radio wave becomes very weak as shown in FIG. Since the level is almost constant, the noise is small, and a clear voice can be heard from the speaker 26, the operation of the voltage variable attenuator circuit 24 is not particularly controlled.

RSSI from RSSI signal amplification circuit 16
If the signal value falls below the sensitivity point F in the course of decreasing, the received electric field intensity becomes very weak, and the saturation can prevent the control circuit 18 from controlling the voltage variable attenuator circuit 24. When the control circuit 18 detects a value B which is slightly larger than that before reaching the point A, the control circuit 18 controls the operation of the voltage variable attenuator circuit 24 so that the sound level is shown in a section between points B and P in FIG. (Attenuation in the first stage).

As described above, by slightly attenuating the audio level as the first stage, it is possible to prevent the audio level from attenuating so that the received audio is difficult to hear and to reduce the RSS.
It is possible to prevent the noise from increasing when the I signal value decreases and falls below the sensitivity point F.

When the RSSI signal value further decreases, S
The SAT signal is no longer detected in the AT signal detection circuit 20, and the detection signal is no longer input to the control circuit 18 (the section on the left side of the point P in the figure). Then, the control circuit 18
Controls the operation of the gain switching circuit 22 to attenuate the audio level in another stage (attenuation in the second stage).

By performing the second-stage attenuation as described above, it is possible to reduce noise that increases at a reception electric field strength below the point P. At this time, unlike the variable voltage attenuator circuit 24, the gain switching circuit 22 does not hinder the control operation of the control circuit 18 due to the saturation.

According to the first embodiment, when the communication portable terminal receives a transmission from another communication portable terminal, the control circuit 18 determines the magnitude of the RSSI signal and , The SAT signal is detected, and at the point B before the RSSI signal value becomes smaller than the sensitivity point F, the received voice level is subjected to the first stage attenuation by the voltage variable attenuator circuit 24, and the RSSI signal is further reduced. When the value decreases and the SAT signal cannot be detected, the received voice level is attenuated in the second stage by the gain switching circuit 22, so that the noise of the received voice during a call can be reduced stepwise. .

Therefore, at the point B before the RSSI signal value becomes equal to or lower than the sensitivity point F, when the received voice level is attenuated in the first stage, the received voice level is attenuated less than in the conventional noise reduction system. By doing so, it is possible to prevent the received sound from becoming difficult to hear due to the attenuation of the received sound level.

The RSSI signal value is further reduced and the noise becomes intense. At the RSSI signal value at which the SAT signal cannot be detected, the received sound level is attenuated in the second stage to thereby reduce the R value.
It is possible to reliably reduce noise that hinders communication in an area lower than the SSI signal value.

In the first embodiment, the SAT signal when the received signal is an analog signal is used. However, when the received signal is a digital signal, the same function is exhibited by using the DSAT signal. Can be done. In this case, a DSAT signal detection circuit may be used instead of the SAT signal detection circuit 20 in the first embodiment. The DSAT signal is used based on a car telephone system such as N-TACS using a digital signal.

[0027]

As described above, according to the communication portable terminal of the present invention, when the communication portable terminal receives a transmission from another communication portable terminal, the size of the RSSI signal is determined. At the same time, the SAT signal is detected, the received voice level is attenuated in the first stage before the RSSI signal value becomes smaller than a predetermined value in the course of decreasing, and the RSSI signal value further decreases to reduce the SAT signal. It is possible to implement the noise reduction method of the communication portable terminal according to the present invention, in which the level of the received voice is attenuated in the second stage when the detection becomes impossible, thereby gradually reducing the noise of the received voice during a call. it can.

For this reason, when the received voice level is attenuated in the first stage before the RSSI signal value becomes smaller than a predetermined value in the course of decreasing, the level of the received voice level is reduced by the conventional noise reduction method. By making the number smaller, it is possible to prevent the received sound from being difficult to hear even when the volume slightly rises or falls due to the attenuation of the received sound level.

Further, the RSSI signal value is further reduced, the noise becomes intense, and at the RSSI value at which the SAT signal cannot be detected, the received audio level is attenuated in the second stage, whereby such RSSI value is reduced.
It is possible to reliably reduce noise that hinders communication in a region where the value falls below the I value.

Therefore, according to the present invention, it is possible to not only reduce the noise but also prevent the reception sound from becoming difficult to hear in a region near the point where the RSSI signal value decreases to a predetermined value. A mobile communication terminal and a noise reduction method thereof can be provided.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a communication portable terminal according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram graphically showing a noise reduction method of the communication portable terminal according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a received voice level and a received electric field strength in a graph.

FIG. 4 is a characteristic diagram showing a graph of a conventional noise reduction method for a communication portable terminal.

[Explanation of symbols]

 REFERENCE SIGNS LIST 12 antenna 14 mobile phone reception circuit 16 RSSI signal amplification circuit 18 control circuit 20 SAT signal detection circuit 22 gain switching circuit 24 voltage variable attenuator circuit 26 speaker

Claims (3)

[Claims] 1. An RSSI signal discriminating means for discriminating a magnitude of an RSSI signal when a communication portable terminal receives a transmission from another communication portable terminal; a SAT signal detecting means for detecting a SAT signal; Voice attenuating means for attenuating the received voice level; performing a first-stage attenuation on the received voice level before the RSSI signal value becomes less than or equal to a predetermined value in the course of decreasing, and further reducing the RSSI signal value, S
Control means for controlling the voice attenuating means so as to perform a second-stage attenuation when an AT signal can no longer be detected. 2. An RSSI signal discriminating means for discriminating a magnitude of an RSSI signal when a communication portable terminal receives a transmission from another communication portable terminal; a DSAT signal detecting means for detecting a DSAT signal; Voice attenuating means for attenuating the received voice level; performing a first-stage attenuation on the received voice level before the RSSI signal value becomes less than or equal to a predetermined value in the course of decreasing, and further reducing the RSSI signal value, D
Control means for controlling the voice attenuating means so as to perform a second-stage attenuation when the SAT signal cannot be detected. 3. When the portable communication terminal receives a transmission from another portable communication terminal, the portable communication terminal determines the magnitude of the RSSI signal, detects the SAT signal or the DSAT signal, and reduces the RSSI signal value. The first step of attenuation is performed on the received audio level just before it becomes less than or equal to a predetermined value in the process of becoming, and when the RSSI signal value becomes smaller and the SAT signal or DSAT signal becomes undetectable, the received audio level is reduced. A noise reduction method for a communication portable terminal, characterized in that noise of a received voice during a call is reduced stepwise by performing two-stage attenuation.