JPH0637727A - Multiplex transmitter - Google Patents

Abstract

PURPOSE:To provide a multiplex transmitter in which a voice signal and plural modulation signals are simultaneously subject to multiplex transmission within a prescribed frequency band of a wired transmission line and the articulation and the intelligibility of the voice signal are not lost. CONSTITUTION:The transmitter is provided with 1st filter means (13,14) setting a transmission frequency band of a modulation signal multiplexed with a voice signal to a frequency band between formant frequencies of the voice signal, and with 2nd filter means (3-6) including band stop filters (4,5) setting a transmission band of the voice signal to a frequency band at which no voice missing takes place and attenuating the portion of the voice transmission band equivalent to the carrier frequency band of the modulation signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex transmission device for simultaneously transmitting a voice signal and a modulated signal such as digital data within a predetermined frequency band of a transmission line.

[0002]

2. Description of the Related Art Conventionally, in terminal equipment such as telephone lines,
A multiplex transmission system is known in which only one line is used to simultaneously transmit a low-frequency signal such as voice and measurement waveform data, and a plurality of signals such as digital data. For example, in wired or wireless communication, it is possible to simultaneously talk about the contents while transmitting the measurement waveform of the instrument and digital data. In order to perform this multiplex transmission method, conventionally, a frequency division method is used to distribute the low frequency band side to a voice and the high frequency band side to a modem or the like that outputs digital data and the like. In addition, by switching a plurality of modulated signals that are multiplexed and transmitted in addition to the voice signal, a scheme has been made to transmit the voice signal without deteriorating the intelligibility of the voice signal.

In a telephone, the frequency band of the wired transmission line is as narrow as 0.3 to 3.4 KHz. When voice and other modulated signals are multiplexed and transmitted, for example, as shown in FIG. The modulated signal is divided into the low frequency band side and the high frequency band side. When there are two types of modulated signals to be transmitted, as shown in FIG. 5B, the audio signal is distributed to the low frequency band side, and the high frequency band side is divided into two bands to be divided into two. It was distributed to modulated signals.

[0004]

Speech is composed of vowels and consonants, and vowels have formants in the frequency band shown in FIG. For example, the first vowel "a"
Since the formant is around 0.3 KHz, if the transmission frequency band of voice is set to 0.3-2 KHz,
Since the second formant of the vowel "a" is 2.4 to 3 KHz, the transmitted voice may be lost. Also in the consonant, "sa", "shi", "su", "se",
The frequency range pronounced as "so" has a main component at 2 KHz or higher, so that the transmitted voice is lost, and there is a problem that the clarity and intelligibility of the voice are significantly deteriorated. Further, when two or more types of modulated signals are transmitted from a modem or the like as shown in FIG. 5B, the band of the voice signal is further narrowed, so that only one modulation signal is transmitted in addition to voice. Was the limit.

An object of the present invention is to provide a multiplex transmission device capable of simultaneously multiplex-transmitting voice and a plurality of modulated signals within a predetermined frequency band of a transmission line, and which does not impair the clarity and intelligibility of voice. Is.

[0006]

The multiplex transmission apparatus of the present invention comprises a first filter means for setting a modulated signal to be multiplexed with a voice signal in a frequency band intermediate between the formants of the voice and the formants, and the voice signal of the voice signal. And a second filter means including a bandpass stop filter for setting a transmission band to a frequency band that does not cause voice loss and attenuating a voice transmission band portion corresponding to a carrier frequency band of the modulated signal. .

The second invention is characterized in that the modulation signal is a signal obtained by frequency-shift modulating digital data.

Further, the multiplex transmission apparatus of the third invention is characterized in that a low frequency signal is transmitted by frequency modulation in a low frequency band of the predetermined transmission frequency band outside the voice transmission frequency band.

[0009]

[Function] The transmission band of the voice signal is set to a frequency band in which the intelligibility and the intelligibility are not deteriorated, and the modulation signal multiplexed and transmitted with the voice has a frequency band between the formants which is less affected by the voice formants. used. Further, in order to eliminate mutual interference between the voice signal and the modulated signal, the band corresponding to the carrier frequency band of the modulated signal in the voice transmission band is attenuated by the bandpass stop filter, whereby the clarity and intelligibility of the voice are improved. Be improved.

[0010]

[Example] 0.3 to 3.4 KH used on a telephone line
multiplex-transmitted voice distributed to the z frequency band,
A frequency band of a modulated signal of digital data and a low frequency signal from a modem or the like will be described with reference to FIG. FIG. 1A shows a transmission frequency band of voice, which is about 0.5 to
The frequency band of 3.4 KHz is used. Figure 1 (B)
Indicates the frequency band of the modulated signal of the digital data transmitted from the modem, and two carrier frequencies f ₁ and f ₂ are used in this example. The carrier transmission frequencies f ₁ and f ₂ are selected between the formants and the formants between which the modem transmission frequency band from the modem is within the voice transmission frequency band and which has little influence on voice loss. As shown in FIG. 1A, a portion of the frequency corresponding to the carrier frequencies f ₁ and f ₂ in the voice transmission frequency band is attenuated so as to prevent passage of the voice signal. Further, a low frequency signal or a low speed signal such as a waveform signal from an instrument that is multiplexed and transmitted is a carrier wave f _{3 of the} waveform signal as shown in FIG.
Is allocated to a frequency band of 0.3 to 0.5 KHz.

FIG. 2 shows the frequency characteristics of the voice transmission frequency band and the modulation signal from the modem in the frequency band near the carrier frequencies f ₁ and f ₂ shown in FIGS. 1 (A) and 1 (B). . Digital data output from the modem "1" binary logic "0" is the frequency deviation modulation (FSK) in response to, sideband level of the carrier f _1, f ₂ generated at this time is FIG. 4 Since it is low as shown by the solid line, even if a part of the sideband from which the carriers f ₁ and f ₂ are removed by the voice transmission frequency band shown by the broken line in the figure passes, the influence on the voice is extremely small.

FIG. 3 shows the relationship between the cutoff frequency of the filter and the intelligibility of the voice.
When KHz is used as the upper limit of voice frequency, the intelligibility is 60%
However, when the cutoff frequency of 0.5 KHz by the high-pass filter (HP) is set as the lower limit, the clarity is only slightly decreased from 100%. That is, FIG. 3 shows that by allocating the voice transmission frequency band to 0.5 to 3.4 KHz, sufficient intelligibility can be obtained, and even if the first formant of voice is missing, conversation is not hindered. .

FIG. 4 is a block diagram showing an embodiment of the multiplex transmission apparatus of the present invention which realizes the principles of FIGS. In FIG. 4, the audio signal converted into the electric signal by the microphone 1 is amplified by the amplifier 2, and the audio signal of 0.5 KHz or less is cut off by the high-pass filter (HPF) 3, and the band-pass stop filter (BEF) 4, 5 are provided.
Are sequentially passed. In the passing process, the frequency bands of the carrier frequencies f ₁ and f ₂ are attenuated, and then the low pass filter (LPF) 6 cuts off the frequency band of 3.4 KHz or more. As a result, as shown in FIG. A voice signal in the voice transmission band shown is input to the adder 7.

Further, a low-frequency signal such as a measurement waveform or a low-speed transmission waveform is supplied from a measuring instrument to a voltage / frequency (V / F) converter 8, where it is modulated to a frequency corresponding to the voltage level and is converted into a high frequency range. The signals are sequentially sent to the filter 9 and the low pass filter 10. A low-frequency signal that passes through the frequency band of 0.3 to 0.5 KHz as shown in FIG. 1C in the high-pass filter 9 and the low-pass filter 10 is input to the adder 7.

The digital data from the measuring instrument is CP
U11, whose output is frequency shift keying (FS)
K) The signal is modulated at a low speed by the circuit 12, the modulated output is sequentially sent to the high-pass filter 13 and the low-pass filter 14, and the modulated signal that has passed the frequency band shown in FIG. 1B is input to the adder 7. To be done.

The adder 7 adds the voice signal of the limited frequency band through each filter, the modulation signal corresponding to the digital data from the modem and the low frequency signal and multiplexes them, and simultaneously, from the hybrid circuit 15 and the telephone line. Transmission line 1
Sent via 6. On the receiving side, the multiplexed signal sent via the transmission line 16 is received via the hybrid circuit 17, and the audio signal is passed through the high-pass filter 18, the band pass stop filters 19 and 20, and the low-pass filter 21 and the audio signal. Only the selected one is amplified through the amplifier 22 in sequence, and then the speaker 23 outputs the sound. In addition, the received multiplex signal includes a high-pass filter 24 and a low-pass filter 2.
Only the low-frequency signal is sorted out sequentially through 5, and demodulated into a voltage waveform by the frequency / voltage (F / V) converter 26. Further, the received multiplexed signal is sequentially passed through the high-pass filter 27 and the low-pass filter 28 to select only the modulated signal corresponding to the digital data, the frequency shift demodulation circuit 29 discriminates the digital data, and the digital data is passed through the CPU 30. Is output. As described above, the three kinds of signals of the voice, the digital data and the waveform signal sent from the transmitting side are simultaneously multiplexed by frequency division and sent to the receiving side through the transmission line 16 and separated into each type at the receiving side. Demodulated.

On the other hand, the voice from the other party is the microphone 3
1, the high-pass filter 32, the band-pass stop filters 33 and 34, the low-pass filter 35, the hybrid circuit 17, the transmission line 16, and the hybrid circuit 15, and the high-pass filter 41 and the band-pass stop filters 42 and 4 are received.
3, a low-pass filter 44, an amplifier 45, and a speaker 46.
Is output from. Thus, while transmitting the waveform signal and the digital data using the telephone line, the data can be simultaneously spoken by voice. Moreover, Figure 1
Since a specific transmission frequency band is set depending on the types of signals to be multiplexed as described in 3 to 3, low frequency signals,
There is no loss of digital data or loss of transparency and intelligibility of the voice.

The multiplex transmission apparatus of the present invention is not limited to the configuration of FIG. 4, and various modifications are possible as long as they satisfy the gist of the present invention described with reference to FIGS. Is.

[0019]

According to the present invention, a plurality of types of signals including voice can be multiplex-transmitted within a limited frequency band of a transmission line without impairing the intelligibility and intelligibility of the voice. By comparison, the transmission of voice can be improved, and two or more types of signals other than voice can be multiplexed. Also,
The circuit configuration of the multiplex transmission device is simple and can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a diagram for explaining distribution of transmission frequency bands of voice and various signals according to the present invention.

FIG. 2 is an enlarged view for explaining a band of an attenuated carrier frequency portion of FIG. 1 of the present invention.

FIG. 3 is a diagram showing a relationship between a cutoff frequency of a filter and voice clarity.

FIG. 4 is a block diagram showing an embodiment of a multiplex transmission device of the present invention.

FIG. 5 is a diagram showing distribution of transmission frequency bands of conventional audio signals and modulated signals.

FIG. 6 is a diagram showing a distribution of vowel format.

[Explanation of symbols]

3, 9, 13, 18, 24, 27, 41 High-pass filter 6, 10, 14, 21, 25, 28 44 Low-pass filter 4, 5, 19, 20, 34, 35, 42, 43 Band-pass stop filter 7 adder 16 transmission line

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[Procedure amendment]

[Submission date] August 21, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

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[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

FIG. 2 shows the frequency characteristics of the voice transmission frequency band and the modulation signal from the modem in the frequency band near the carrier frequencies f ₁ and f ₂ shown in FIGS. 1 (A) and 1 (B). . Digital data output from the modem "1" binary logic "0" is the frequency deviation modulation (FSK) in response to, sideband level of the carrier f _1, f ₂ generated at this time is FIG. 4 Since it is low as shown by the solid line, even if a part of the sideband from which the carriers f ₁ and f ₂ are removed by the voice transmission frequency band shown by the broken line in the figure passes, the influence on the voice is extremely small. In addition, a band pass stop filter for attenuating the voice transmission band part is used as a modem carrier f ₁ ,
By providing each carrier to be used like f _2, the band shown by the dotted line between the carriers in FIG. 2 is also effectively used as a voice band, and the clarity and analysis of voice are improved. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 25, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

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[Fig. 2]

Claims (3)

[Claims] 1. A transmission device that multiplex-transmits a voice signal and a modulation signal within a predetermined transmission frequency band of a transmission path, wherein the modulation signal to be multiplexed with the voice signal is in a frequency band intermediate between the formant of the voice and the formant. A first filter means for setting, and a band pass stop filter for setting a voice transmission band of the voice signal to a frequency band that does not cause voice loss and attenuating a voice transmission band portion corresponding to a carrier frequency band of the modulated signal. And a second filter unit including the multiplex transmission device. 2. The multiplex transmission device according to claim 1, wherein the modulated signal is a signal obtained by frequency-shifting modulating digital data. 3. The low frequency signal is transmitted by frequency modulation in a low frequency band of the predetermined transmission frequency band outside the voice transmission band.
The multiplex transmission device as set forth in.