JP2000092161A - Communication device - Google Patents

Abstract

(57) [Summary] [Problem] Even if a mute is performed during a talk, an unpleasant click sound is not generated. SOLUTION: A communication device for digitally encoding an analog audio signal and performing communication, which receives a digital audio signal and outputs a digital code corresponding to silence in response to an instruction signal, and a mute circuit for communication. And a control circuit 23 for instructing the mute circuits 12 and 13 to output a code corresponding to silence when necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a portable radio telephone,
The present invention relates to a communication device such as a cellular system or a personal communication system (PCS) for performing communication by digitally encoding an analog voice signal, and more particularly to a communication device capable of muting without generating unpleasant sound. It is about.

[0002]

2. Description of the Related Art In a mobile phone system that has become widespread in recent years, a large number of base stations are installed in a vast service area, and a communication frequency is switched during a call to continue the call. Further, in an area where radio waves are weak, such as an edge of a service area, communication with a base station becomes unstable, loss of synchronization may occur, and call voice may be disturbed.

[0003] When switching frequencies during a call, mute of the call voice is performed in order to reduce abnormal noise accompanying the switching. Also, in the event that the synchronization is lost during a call, the call voice is muted to reduce abnormal noise. This muting is conventionally performed by switching an analog switch.

[0004]

However, when the analog switch is switched, a DC bias offset potential is generated, and a click sound is generated. Therefore, when switching the frequency during a call, if the synchronization is lost during the call, there is a problem that an unpleasant click sound is generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional communication apparatus, and has an object to prevent an unpleasant click sound from being generated when a mute is performed during a call. To provide a communication device.

[0006]

According to a first aspect of the present invention, there is provided a communication apparatus for performing communication by digitally encoding an analog voice signal, receiving a digital voice signal, and performing silence in response to an instruction signal. And a control means for instructing the mute circuit to output a code corresponding to silence when necessary during communication. As a result, the output of a code corresponding to silence is instructed when necessary during communication, and a digital code corresponding to silence is output and muted in response to the instruction signal.

A communication device according to a second aspect of the present invention is characterized in that the control means outputs an instruction signal when switching the frequency of a communication signal during communication. Thus, when switching the frequency of the communication signal during communication, an instruction signal is output, a digital code corresponding to silence is output, and mute is performed.

According to a third aspect of the present invention, in the communication apparatus, the control means outputs an instruction signal when the synchronization is lost during communication. Thus, when out of synchronization occurs during communication, an instruction signal is output, a digital code corresponding to silence is output, and mute is performed.

According to a fourth aspect of the present invention, there is provided a communication device comprising a detecting means for detecting when a signal obtained by converting a digital audio signal into an analog signal crosses a predetermined level and outputting a detection signal, wherein the mute circuit is provided from the control means. Receiving the detection signal while receiving the instruction signal, outputs a digital code corresponding to silence. Thus, when the analog audio signal crosses the predetermined level, the output of the digital code corresponding to the silence is started, and the audio signal can be switched smoothly.

According to a fifth aspect of the present invention, there is provided a communication apparatus comprising a detecting means for detecting when a signal obtained by converting a digital audio signal into an analog signal crosses a predetermined level and outputting a detection signal, wherein the mute circuit is provided from the control means. When the detection signal is received while the instruction signal is canceled, the output of the digital code corresponding to silence is stopped and the digital audio signal is passed. Thus, when the analog audio signal crosses the predetermined level, the output of the digital code corresponding to silence is stopped, and the audio signal can be switched smoothly.

[0011] In a communication apparatus according to a sixth aspect of the present invention, the mute circuit includes storage means for storing a silent pattern, and reads out and outputs the silent pattern from the storage means when necessary. As a result, the silence pattern is read out from the storage means and output when necessary, and an appropriate mute is realized.

In a communication apparatus according to a seventh aspect of the present invention, the mute circuit includes a predetermined potential generating means for outputting a silent pattern corresponding to all 1s, and switches to the predetermined potential generating means when necessary to switch to a silent state. It is characterized by outputting a pattern. As a result, a silence pattern corresponding to all 1 is output from the predetermined potential generating means when necessary, and an appropriate mute is realized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a communication device according to an embodiment of the present invention will be described with reference to the accompanying drawings. In each figure,
The same components are denoted by the same reference numerals, and redundant description will be omitted. In the present embodiment, a mobile phone (PDC)
However, the present invention is not limited to PDC, but can be applied to general mobile wireless devices having a function of converting a digital voice signal into an analog signal, and communication devices. The type of wireless communication system in the mobile wireless device does not matter.

FIG. 1 shows the configuration of a portable radio telephone. This portable radio telephone has an antenna 1,
A signal can be taken in from the duplexer 2, and transmission can be performed from the duplexer 2 via the antenna 1.

In order to process the received signal, the receiving circuit 3,
A / D converter 6, modem 8, channel codec 9, speech codec 10, reception digital mute circuit 1
2, a D / A converter 14, a receiving mute switch 16, a receiving amplifier 18, and a receiver 19 are provided. Also,
The microphone 21 and the transmission amplifier 2 for processing the transmission signal
0, transmission mute switch 17, A / D converter 15, transmission digital mute circuit 13, speech codec 1
0, a channel codec 9, a modem 8, a D / A converter 7, and a transmission circuit 5. A synthesizer circuit 4 is provided to control the frequencies of the receiving circuit 3 and the transmitting circuit 5.

In order to control each part of the portable radio telephone,
CPU 29, RAM 31, ROM 30 via bus 11
A control circuit (ASIC) 23 is connected to the modem 8, the channel codec 9, and the speech codec 10. Here, the control circuit 23 mainly processes the output of the control signal of each circuit and the output signal of each circuit. The CPU 29 performs a control operation according to a program stored in the ROM 30. RAM
31 is used as a setting state of a portable radio telephone, a telephone number memory, and a digitally processed recording signal memory;
Stored information is retained by a backup battery (not shown) even when the device is not turned on. ROM30
Is composed of an EEPROM or a flash ROM, and stores, in addition to a program for a mobile phone, an individual number and adjustment information of a wireless device.

The control circuit 23 includes an LCD 24 for displaying information and a key operation unit 2 having various keys.
5, an amplifier 26 and an oscillation circuit 28 are connected. LC
At D24, a telephone number display and other mobile phone status displays are performed. The key operation unit 25 is used for performing a telephone number, outgoing call, end call, function setting, and the like. Amplifier 26
Is connected to a sounder 27. A corresponding signal is output from the control circuit 23, amplified by the amplifier 26, outputted as sound from the sounder 27, and notified to the user of the ringtone and the operation confirmation sound. The oscillation circuit 28 supplies a predetermined clock signal to the control circuit 23. Further, a battery 33 is provided, and a predetermined voltage _Vcc is obtained by the stabilized power supply circuit 32 in response to the output of the battery 33.

Next, the receiving operation in the portable radio telephone will be described. The signal captured by the antenna 1 is received by the receiving circuit 3 via the antenna duplexer 2. The receiving circuit 3 receives the output of the synthesizer circuit 4 under the control of the control circuit 23, performs down-conversion of the received signal, obtains and amplifies the intermediate frequency signal,
The K signal is orthogonally demodulated and sent to the A / D converter 6.

The A / D converter 6 converts the signal into a digital signal, performs delay detection with the modem 8, establishes frame synchronization,
Perform color code detection. Further, the channel codec 9 performs deinterleaving and error correction decoding,
VSELP (Vector S
um Excited Linear Prediction).

The output of the speech decoder 10 is supplied to a D / A converter 14 via a receiving digital mute circuit 12.
The audio signal is demodulated by the amplifier, and is amplified by the amplifier 18 via the receiving mute switch 16. The receiver 19 is driven by this signal to be converted into an acoustic signal, and the audio is transmitted to the user.

On the other hand, the voice of the user is converted into an electric signal by the microphone 21, amplified by the amplifier 20, converted to a digital signal by the A / D converter 15 via the transmission mute switch 17, and transmitted. The signal is transmitted to the speech codec 10 via the talk digital mute circuit 13, and the speech codec 10 performs VSELP encoding.

The output of the speech codec 10 is subjected to error correction coding and interleave processing by a channel codec 9, addition of a frame signal and addition of a color code signal by a modem 8, signal mapping processing, and transmission timing setting. Is converted to an analog signal by the D / A converter 7 and output to the transmission circuit.

The transmitting circuit 5 performs quadrature modulation of the analog signal, further performs mixing up from the local signal of the synthesizer circuit 4, amplifies the signal as a predetermined transmitting frequency, and transmits the signal as a radio wave from the antenna 1 via the antenna duplexer 2. Is done.

FIG. 2 shows in detail the mute processing portion according to the present invention. The received voice passes from the speech codec 10 through the receiving mute circuit 12 and is converted into an analog signal by the D / A converter 14. The D / A converter 14 is a control circuit 2
3 based on the synchro signal 55 and the clock signal 56 generated.

In the above description, the channel codec 9 detects out-of-synchronism using a CRC (cyclic redundancy check) code included in a received frame. Then, when the synchronization is lost, the synchronization is re-established and the mute is performed until the synchronization is established. That is, the channel codec 9 notifies the CPU 29 of the out-of-synchronization and the establishment of the synchronization.
3 and the receiving mute control signal 52 is output to the receiving digital mute circuit 12.

The CPU 29 detects the deterioration of the reception quality and the decrease of the reception level by the above-mentioned channel codec, and when the predetermined reception quality is not obtained or the reception level drops below the predetermined level, the CPU 29 detects and detects this. Circuit 23
Notify to As a result, the reception mute control signal 52 is output from the control circuit 23 to the reception digital mute circuit 12, and the transmission mute control signal 54 is output to the transmission digital mute circuit 13.

As shown in FIG. 3, the control waits for the reception mute control signal 52 to be supplied to the reception mute circuit 12 (S1). When the reception mute control signal 52 is supplied to the reception digital mute circuit 12, the reception voice mute control signal 52 is received. Waiting for the reception mute start signal 51 output every time the analog signal level crosses the signal ground level (S
2) The receiving mute circuit 12 operates, a bit string of a silent pattern is given to the D / A converter 14, and a silent analog signal is output (S3).

On the other hand, as shown in FIG.
The digital signal is converted by the / D converter 15 into a digital signal based on the sync signal 55 and the clock signal 56 generated by the control circuit 23, passed through the transmission digital mute circuit 13, and input to the speech codec 10.

Waiting for the transmission mute control signal 54 to be supplied to the transmission digital mute circuit 13 (S1), and when the transmission mute control signal 54 is supplied to the transmission mute circuit 13, the analog signal level of the transmission voice is reduced. After waiting for a transmission mute start signal 53 output every time the signal crosses the signal ground level (S2), the transmission mute circuit 13 operates and the bit sequence of the silent pattern is converted to the speech codec 1
0 (S3).

As shown in FIG. 4, a potential _{Vcc from} a stabilized power supply circuit 32 (predetermined potential generating means) for outputting a silent pattern corresponding to all 1s is supplied to a terminal S2 of the receiving digital mute circuit 12. Has been given. As a result, when the receiving mute control signal 52 is supplied to the receiving digital mute circuit 12, the bit string of the all-one silence pattern waits for the receiving mute start signal 51.
The analog signal is supplied to the A converter 14 to output a silent analog signal. In the first embodiment, the transmission digital mute circuit 13 is configured in the same manner as the configuration of the reception digital mute circuit 12 shown in FIG. 4, and the potential V _cc for outputting the silent pattern corresponding to all _1s is Has been given. In another embodiment, the reception digital mute circuit 12 is connected to the SP-CODEC 10 or the D / A converter 1.
4, the TRIG signal 51 can be generated by arithmetic processing in the SP-CODEC 10, for example.

In the second embodiment, as shown in FIG. 5, the receiving digital mute circuit 12 comprises a ROM 90 and a switch 91, and a ROM (storage means) 90.
Stores several silent patterns. ROM
The output of the signal 90 is supplied to a terminal S2, the output of the speech codec 10 is supplied to a terminal S1, a reception mute control signal 52 is supplied, and a reception mute start signal 51 is supplied.
Is switched to the terminal S2 side. In the second embodiment, the transmission digital mute circuit 13 is also similar to the reception digital mute circuit 12 shown in FIG.
90, and a switch 91.
Several silence patterns are stored, and the switching has the same configuration. In another embodiment, at least one of the ROM 90 and the switch 91 is SP
-Provided in the CODEC 10 or the D / A converter 14, for example, in the SP-CODEC 10
It is also possible to generate the signal 51.

Then, as shown in FIG. 3, when the frequency switching or the out-of-synchronization is completed and the reception mute control signal 52 or the transmission mute control signal 54 is given (S4), the analog signal level of the reception voice is changed. Waiting for the reception mute start signal 51 output every time the signal ground level is crossed, or waiting for the transmission mute start signal 53 output every time the analog signal level of the transmission voice crosses the signal ground level (S5). ), The audio mute is stopped (S6).

That is, the receiving digital mute circuit 12
Connects the speech codec 10 and the D / A converter 14, and the transmission digital mute circuit 13 connects the speech codec 10 and the A / D converter 15.

Here, waiting for a reception mute start signal 51 which is output every time the analog signal level of the received voice crosses the signal ground level, and transmission which is output every time the analog signal level crosses the signal ground level The reason for operating after waiting for the mute start signal 53 will be described.

Since the transmitted voice is the same as the received voice, the case of the received voice is taken as an example.
A digital audio signal is supplied to the D / A converter 14, and this digital audio signal varies in a range of 2.8V to 0V as shown in FIG. 6 when converted to an analog signal (however, It is not always a sine wave as shown in FIG. 6). And the signal ground level is
1.4V.

When the analog signal level shown in FIG. 6 crosses the signal ground level (P1, P2)
(2, P3), the silent pattern is transmitted, or the transmission of the silent pattern is stopped. Here, in the digital audio signal, all 1s are assigned to the pattern corresponding to silence as shown in FIG. This all-one digital signal corresponds to analog 1.4V.

Therefore, when the signal crossing the signal ground level is waited and the pattern corresponding to silence is transmitted, 1.4 V (pattern corresponding to silence) is continuously output when the analog voltage reaches 1.4 V, and the level fluctuation is reduced. No click sound is generated due to the discontinuity of the switching level.

As shown in FIG. 7, the digital signal is shifted from 1.4 V to 0 V (above 1.4 V in FIG. 7).
Since the most significant bit is “1” and the most significant bit is “0” on the 1.4V to 3V side (below 1.4V in the figure), the most significant bit is from 0 to 1 or from 1 Upon detecting the displacement to 0, the D / A converter 14 outputs a reception mute start signal 51. A / D converter 15
In the same manner, the D / A converter 14 detects that the most significant bit changes from 0 to 1 or from 1 to 0, and outputs the transmission mute start signal 53.

[0039]

As described above, according to the communication apparatus of the first aspect, the output of a code corresponding to silence is instructed when necessary during communication, and silence is responded to in response to this instruction signal. Since the digital code is output and muted, appropriate muting can be performed without generating a click sound due to the offset potential at the time of switching, unlike muting by an analog switch.

As described above, according to the communication apparatus of the second aspect, when switching the frequency of a communication signal during communication, an instruction signal is output, a digital code corresponding to silence is output, and mute is performed. Therefore, an unpleasant clicking sound does not occur when switching the frequency.

As described above, according to the communication device of the third aspect, when out of synchronization occurs during communication, an instruction signal is output, a digital code corresponding to silence is output, and mute is performed. In addition, no unpleasant clicking sound is generated when the synchronization is lost.

As described above, according to the communication device of the fourth aspect, when the analog audio signal crosses the predetermined level, the output of the digital code corresponding to the silence is started, and the switching of the audio signal is smoothly performed. This can prevent noise from being generated due to discontinuity of the audio signal.

As described above, according to the communication device of the fifth aspect, when the analog audio signal crosses the predetermined level, the output of the digital code corresponding to the silence is stopped, and the switching of the audio signal is smoothly performed. This can prevent noise from being generated due to discontinuity of the audio signal.

As described above, according to the communication device of the sixth aspect, since the mute circuit includes the storage means for storing the silent pattern, the silent pattern is read out from the storage means and output when necessary. Appropriate mute is achieved.

As described above, according to the communication device of the seventh aspect, since the mute circuit includes the predetermined potential generating means for outputting the silent pattern corresponding to all 1s, the predetermined potential generation is performed when necessary. The silence pattern corresponding to all 1 is output from the means, and an appropriate mute is realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a portable wireless telephone according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of the portable wireless telephone according to the embodiment of the present invention.

FIG. 3 is a flowchart for explaining the operation of the mobile wireless telephone according to the embodiment of the present invention.

FIG. 4 is a diagram showing a second configuration example for transmitting a silent pattern of the audio mute circuit of the portable wireless telephone according to the embodiment of the present invention.

FIG. 5 is a diagram showing a second configuration example for transmitting a silent pattern of the audio mute circuit of the portable wireless telephone according to the embodiment of the present invention.

FIG. 6 is a waveform chart for explaining an audio mute operation of the portable wireless telephone according to the embodiment of the present invention.

FIG. 7 is a diagram showing a correspondence table between a digital signal and an analog potential for describing an audio mute operation of the portable wireless telephone according to the embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 antenna 2 antenna duplexer 3 receiving circuit 4 synthesizer circuit 5 transmitting circuit 6 A / D converter 7 D / A converter 8 modem 9 channel codec 10 speech codec 11 bus 12 receiving digital mute circuit 13 transmitting digital mute circuit 14 D / A converter 15 A / D converter 16 Receive mute switch 17 Transmit mute switch 18 Receive amplifier 19 Receiver 20 Transmit amplifier 21 Microphone 23 Control circuit (A
SIC) 24 LCD display 25 Key unit 26 Amplifier 27 Sounder 28 Oscillation circuit 29 CPU 30 RAM 31 ROM (E
EPROM) 32 Stabilized power supply circuit 33 Battery

Claims (7)

[Claims] 1. A communication device for communicating by digitally encoding an analog audio signal, comprising: a mute circuit for receiving a digital audio signal and outputting a digital code corresponding to silence in response to an instruction signal; Control means for instructing the mute circuit to output a code corresponding to silence in such a case. 2. The communication device according to claim 1, wherein the control unit outputs an instruction signal when switching the frequency of the communication signal during communication. 3. The control means outputs an instruction signal when out of synchronization occurs during communication.
The communication device according to claim 1. 4. A detecting means for detecting when a signal obtained by converting a digital audio signal into an analog signal crosses a predetermined level and outputting a detection signal, wherein the mute circuit receives an instruction signal from the control means. 4. A digital code corresponding to silence is output upon receiving the detection signal.
The communication device according to claim 1. 5. A detecting means for detecting when a signal obtained by converting a digital audio signal into an analog signal crosses a predetermined level and outputting a detection signal, wherein a mute circuit is provided when an instruction signal from the control means is canceled. 5. The communication apparatus according to claim 1, wherein receiving the detection signal stops outputting a digital code corresponding to silence and allows a digital audio signal to pass. 6. The mute circuit according to claim 1, further comprising storage means for storing a silence pattern, and reading and outputting the silence pattern from the storage means when necessary. Communication device. 7. The mute circuit includes a predetermined potential generating means for outputting a silent pattern corresponding to all 1s, and switches to the predetermined potential generating means when necessary to output a silent pattern. Item 6. The communication device according to any one of Items 1 to 5.