JPH0226419A - Modem - Google Patents

Abstract

PURPOSE:To easily set a suitable prescribed signal level by switching automatically a signal level control by a preset means for a sound signal and a signal level control by a preset means for a data signal based on the disable signal of a tone disabler circuit output. CONSTITUTION:An automatic transmission level setting circuit 13 has a function to give the sound signal an attenuation quantity preset beforehand to obtain the optimum prescribed signal level, and a function to give the data signal the attenuation quantity preset beforehand to obtain the optimum prescribed signal level. Based on a disable signal 105 (a signal to show whether a base band signal is the sound signal or the data signal) which is the output of a tone disabler circuit 6, either of the two functions is selected and operated and thus, the optimum signal level is set automatically. Thus, the suitable signal level can be easily set for the data signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applied to frequency division multiple access in the field of communication in which voice signals and data signals in the telephone signal band are transmitted using satellite communication lines.
Multiple Access (hereinafter referred to as FDMA) system (% formula%% formula%)) Adjustment of the optimal baseband signal input level for each of voice signal transmission and data signal transmission, especially for modulators and demodulators for communication systems. This invention relates to a modulator/demodulator with improved means.

(Prior Art) Conventionally, as an example of a modulator/demodulator for FDMA/SCPC communication system, one shown in the configuration diagram of a modulator/demodulator in FIG. 3 is known. 1 is a manual transmission level setting circuit, 2 is a transmission echo switch circuit, 3 is a transmission baseband processing circuit, 4 is a modulation circuit, 5 is a transmission echo control circuit, 6 is a tone disabler circuit, 7 is an echo suppressor circuit, and 8 is a Reception echo control circuit, 9 demodulation circuit, 10 reception baseband processing circuit, 11 reception echo attenuation circuit, 12 reception level setting circuit, 101 baseband input signal, 102 IF
103 is an IF input signal, 104 is a baseband output signal, 105 is a disable signal, 106 is a transmission echo suppression signal, and 107 is a reception echo suppression signal.

A baseband input signal 101 input to the modem is input to a manual transmission level setting circuit 1.

The baseband input signal 101 is an audio signal or a data signal in the telephone signal band, and is manually adjusted and set to a predetermined optimal signal level for each audio signal or data signal in the manual transmission level setting circuit 1. The output signal of the manual transmission level setting circuit 1 is input to a transmission echo switch circuit 2, a tone disabler circuit 6, and an echo suppressor circuit 7. Baseband input signal 10
1 is an audio signal, the input of the transmitting echo switch circuit 2 is used to avoid retransmitting the echo signal caused by the time delay of the round trip to the communication satellite. The signal is transmitted by echo switch circuit 2
Retransmission is prohibited by switch operation. The audio signal or data signal that is output from the transmission echo switch circuit 2 and is not determined to be an echo signal is input to the transmission baseband processing circuit 3, where it is subjected to transmission baseband signal processing. The output signal of the transmission baseband processing circuit 3 is input to the modulation circuit 4, which modulates a carrier wave of intermediate frequency (hereinafter referred to as ■F), and an IF output signal 102 for FDMA/SCPC communication is output from the modulation circuit 4. and becomes the output of the modem. On the other hand, the FDMA/SCPC input to the modem
■F input signal 103 for communication is input to demodulation circuit 9,
The baseband signal is demodulated. The output signal of the demodulation circuit 9 is input to a reception baseband processing circuit 10, where reception baseband signal processing is performed. The output signal of the reception baseband processing circuit 10 is input to a reception echo attenuation circuit 11, a tone disabler circuit 6, and an echo suppressor circuit 7. If the received signal is a voice signal and is determined to be an echo signal, the receiving echo attenuation circuit 11 applies a predetermined amount of attenuation (for example, 6 dB attenuation) to the input signal. The output signal of the reception echo attenuation circuit 11 (audio signal or data signal that is not determined to be an echo signal) is input to the reception level setting circuit 12.

The input signal of the reception level setting circuit 12 is set to a predetermined signal level, and the baseband output signal 104 is output from the reception level setting circuit 12 and becomes the output of the modem. As mentioned above, when the signal to be transmitted or the signal received is an audio signal, transmission is prohibited or reception is attenuated for the echo signal, but if the signal to be transmitted or received is an audio signal or a data signal This determination is made by the tone disabler circuit 6. Since a tone signal (for example, 2.10 (lHz signal)) is inserted into the data signal, and no tone signal is inserted into the audio signal, the tone disabler circuit 6 detects the tone signal from the input signal. If a tone signal is detected, it is determined that the signal is an input signal or a data signal, and a disable signal 105 is output for disabling the operation of the transmitting echo switch circuit 2 or the receiving echo attenuation circuit 11. The disable signal 105 is input to the transmit echo control circuit 5 and the receive echo control circuit 8.

Based on the disable signal 105 output from the tone disabler circuit 6, the transmit echo control circuit 5 (or the receive echo control circuit 8) suppresses the transmit echo suppress signal 1 output from the echo suppressor circuit 7 during data signal transmission.
06 (or the reception echo suppression signal 107) is prohibited from being input to the transmission echo switch circuit 2 (or the reception echo attenuation circuit 11). The echo suppressor circuit 7 is 2
Compare the levels of two input signals (i.e., the transmitted signal and the received signal), and if the transmitted signal is smaller than the received signal by more than a predetermined level difference, the transmitted signal is determined to be an echo signal. and outputs a transmission echo suppress signal 106 to the transmission echo control circuit 5. If the received signal is smaller than the transmitted signal by a predetermined level difference or more, it is determined that the received signal is an echo signal, and a received echo suppress signal 107 is output to the received echo control circuit 8. During audio signal transmission, the transmission echo suppression signal 106 is input to the transmission echo switch circuit 2 through the transmission echo control circuit 5, and controls prohibition of retransmission of the echo signal. Alternatively, the reception echo suppression signal 107 is inputted to the reception echo attenuation circuit 11 through the reception echo control circuit 8 to control the reception attenuation of the echo signal. Through this operation, echo signals are suppressed (!oppress) during audio signal transmission.

Further, as described above, the baseband input signal 101 is input to the manual transmission level setting circuit 1 at a predetermined level! & It is manually adjusted and set to an appropriate signal level, but if the baseband input signal 101 is an audio signal, a predetermined signal level is set so that the transmission baseband processing circuit 3 does not cause distortion over the dynamic range of the audio signal. The signal level is adjusted and set to the optimum level.

On the other hand, when the baseband input signal 101 is a data signal, it is adjusted and set to a predetermined optimal signal level that optimizes the bit error rate (hereinafter referred to as BER).

For example, the BER characteristics during data transmission at 9600bps and 48QObps are determined by determining the carrier power to noise power ratio (C/N ratio), as shown in the baseband input signal level vs. bit error rate characteristic diagram in Figure 4. Then, the optimum level (■.pt) of the baseband input signal level changes as the baseband input signal level changes.
The best result is This is ■. When a baseband input signal is input at a level higher than pt, the BER deteriorates due to distortion characteristics in baseband signal processing, and V
, ) If the baseband input signal is input at a level lower than p1, the BER will deteriorate due to thermal noise. Therefore, the data signal is adjusted to V Op (level) in the manual transmission level setting circuit 1.
Set. In this way, the level is manually adjusted and set for the audio signal to a predetermined signal level that is optimal for the audio signal, and for the data signal to the predetermined signal level that is optimal for the data signal. A major change was taking place.

(Problem to be Solved by the Invention) However, in the conventional modem described above, the optimal predetermined signal level for voice signals and the optimal predetermined signal level for data signals are different values, so voice signal transmission There is a problem in that the baseband input signal level must be manually adjusted and set each time there is a change from data signal transmission to data signal transmission, or from data signal transmission to audio signal transmission.

Furthermore, as the data signal transmission speed increases, the amount of change in BER with respect to changes in the baseband input signal level increases. For example, when transmitting a 9600 bps data signal, the baseband input signal level is V.

, t±5 dB- will have a large effect on the BER characteristics, so it is necessary to perform detailed manual signal level adjustments and settings each time the baseband input signal changes, making it easy to set the predetermined optimal signal. Level (Vo, t)
There is a problem that it cannot be adjusted or set.

SUMMARY OF THE INVENTION In order to solve the above problems of the prior art, an object of the present invention is to provide a preset means for adjusting and setting a predetermined signal level suitable for an audio signal, and a preset means for adjusting and setting a predetermined signal level suitable for a data signal. and a transmission level setting circuit to automatically switch between signal level control by the audio signal preset means and signal level control by the data signal preset means based on the disable signal output from the tone disabler circuit to achieve an appropriate level control. An object of the present invention is to provide a modulator/demodulator that sets a predetermined signal level.

(Means for Solving the Problems) In order to achieve the above object, the present invention has the following means configuration.

That is, the modulator/demodulator according to the present invention has a function of inputting a baseband signal, which is a voice signal or a data signal in the telephone signal band, and setting the input signal to a predetermined signal level suitable for the voice signal, and a function of setting the input signal to a predetermined signal level suitable for the voice signal. and a function to set the baseband signal to a predetermined signal level, and select the two functions by controlling a disable signal indicating whether the baseband signal is an audio signal or a data signal, and set the baseband signal to an appropriate signal level. automatic transmission level setting means that automatically sets and outputs; a transmission echo suppression control signal that takes the output signal of the automatic transmission level setting means as input and indicates that the baseband signal is a transmission echo signal when the baseband signal is an audio signal; transmission echo switch means that performs an output prohibition operation for a transmission echo signal in an input signal based on; transmission baseband processing means that performs transmission baseband signal processing using the output signal of the transmission echo switch means as input; and; modulating means for modulating an intermediate frequency (IF) carrier wave signal using the output signal of the transmission baseband processing means as input and outputting an IF output signal for FDMA/SCPC communication; and: received FDMA/SCPC communication. demodulation means for demodulating a baseband signal from an IF input signal of the demodulation means; reception baseband processing means for inputting the output signal of the demodulation means and processing the reception baseband signal; Receiving echo attenuating means performs an attenuating operation on the received echo signal in the input signal based on, as an input, a receiving echo suppress control signal indicating that the baseband signal is a received echo signal when the baseband signal is an audio signal; reception level setting means for inputting the output signal of the reception echo attenuation means and outputting a baseband signal set to a predetermined signal level; the output signal of the automatic transmission level setting means and the output of the reception baseband processing means; With the signal as input,
It has a function of detecting tone signals from baseband signals, determines whether the tone signal is detected as a data signal or an audio signal, and outputs a disable signal indicating whether the baseband signal is an audio signal or a data signal. tone disabling means; having a function of detecting an echo signal by receiving the output signal of the automatic transmission level setting means and the output signal of the reception baseband processing means and comparing the levels of the transmitted signal and the received signal; Based on the disable signal output from the tone disabler means, a transmission echo suppression control signal indicating that the baseband signal is a transmission echo signal when the baseband signal is an audio signal, and a transmission echo suppression control signal indicating that the baseband signal is a reception echo signal when the baseband signal is an audio signal. The present invention is characterized by comprising: echo suppression control means for outputting a received echo suppression control signal indicating that there is a received echo suppression control signal; and;

(Function) Hereinafter, the function of the modulator/demodulator of the present invention having the above means configuration will be explained.

The baseband signal input to the modem is automatically set to an appropriate signal level by automatic transmission level setting means. The automatic transmission level setting means has a function of setting a predetermined signal level suitable for an audio signal and a function of setting a predetermined signal level suitable for a data signal. The baseband signal is selected by controlling a disable signal indicating whether it is an audio signal or a data signal, and the baseband signal is automatically set to an appropriate signal level. The output signal of the automatic transmission level setting means is input to the transmission echo switch means.

The transmission echo switch means performs an output inhibiting effect on the transmission echo signal in the input signal based on a transmission echo suppression control signal indicating that the baseband signal is a transmission echo signal when the baseband signal is an audio signal. The output signal of the transmitting echo switch means is input to the transmitting baseband processing means and subjected to transmitting baseband signal processing. The output signal of the transmission baseband processing means is input to the modulation means.

The modulating means modulates an intermediate frequency (IF) carrier wave signal and outputs an IF output signal for FDMA/SCPC communication.

On the other hand, the received IF input signal for FDMA/SCPC communication is input to the demodulation means, and the baseband signal is demodulated. The output signal of the demodulation means is input to the reception baseband processing means and subjected to reception baseband signal processing. The output signal of the reception baseband processing means is input to the reception echo attenuation means. The reception echo attenuator attenuates the reception echo signal in the input signal based on a reception echo suppression control signal indicating that the baseband signal is a reception echo signal when the baseband signal is an audio signal. The output signal of the reception echo attenuation means is input to the reception level setting means.

The reception level setting means outputs a baseband signal set to a predetermined signal level. The output signal of the automatic transmission level setting means and the output signal of the reception baseband processing means are input to the tone disabler means. The tone disabler means has a function of detecting a tone signal from a baseband signal, and when a tone signal is detected, the baseband signal is a data signal, and when a tone signal is not detected, it is determined that the baseband signal is a data signal. determines that the baseband signal is an audio signal and outputs a disable signal indicating whether the baseband signal is an audio signal or a data signal. This disable signal is input to automatic transmission level setting means to control appropriate signal level setting. Further, the output signal of the automatic transmission level setting means and the output signal of the reception baseband processing means are also input to the echo suppression control means. The echo suppress control means has a function of detecting an echo signal by comparing the levels of the transmitted signal and the received signal, and the baseband signal is adjusted to match the audio signal based on the disable signal inputted from the tone disabler means. If the baseband signal is an audio signal, it outputs a transmission echo suppression control signal indicating that it is a transmission echo signal, and if the baseband signal is an audio signal, it outputs a reception echo suppression control signal indicating that it is a reception echo signal.

This transmission echo suppression control signal is input to the transmission echo switch means to control the output inhibition effect of the transmission echo signal, and the reception echo suppression control signal is input to the reception echo attenuation means to control the attenuation effect of the reception echo signal.

(Embodiment) Next, an embodiment of the modem according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a modulator/demodulator according to an embodiment of the present invention.
14 is an automatic transmission level setting circuit, 14 is an echo suppression control circuit, 108 is a transmission echo suppression control signal, and 109 is a reception echo suppression control signal. In addition, number 2.3
．． 4.6.9.10.11.12.101.102.1
Components or signals labeled 03.104 and 105 are similar to the components or signals labeled with the same numbers in the conventional modulator/demodulator block diagram of FIG.

That is, the difference between the embodiment of the present invention shown in FIG. 1 and the conventional example shown in FIG.
An automatic transmission level setting circuit 13 is used instead of the tone disabler circuit 6, and a disable signal 105 output from the tone disabler circuit 6 is used.
controls the automatic transmission level setting circuit 13, and an echo suppressor control circuit 14 is used in place of the echo suppressor circuit 7, transmission echo control circuit 5, and reception echo control circuit 8. In the following description of the embodiments of the present invention, detailed descriptions of components or signals similar to those of the conventional example will be omitted.

A baseband input signal 101 input to the modem is input to an automatic transmission level setting circuit 13.

The automatic transmission level setting circuit 13 sets a predetermined signal level optimal for audio signal transmission when the baseband input signal 101 is an audio signal, and a predetermined signal level optimal for data signal transmission when the baseband input signal 101 is a data signal. To automatically set an optimal signal level to a predetermined signal level and output a baseband signal. Automatic optimum signal level setting is performed by the following operation. The automatic transmission level setting circuit 13 has a function of providing a preset amount of attenuation to bring the audio signal to an optimal predetermined signal level, and a function of giving a preset amount of attenuation to give the optimal predetermined signal level to the data signal. Based on the disable signal 105 (signal indicating whether the baseband signal is an audio signal or a data signal) output from the tone disabler circuit 6, Next, one embodiment of the automatic transmission level setting circuit 13, which automatically sets the optimum signal level by selecting and operating one of the two functions, will be described with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of the automatic transmission level setting circuit, in which 15 is an operational amplifier, 16 is a field effect transistor (FET), and 17 is a switch circuit.

The switch circuit 17 has an audio signal reference voltage (Vr-r□
) is connected to the data signal reference voltage (Vrsr2), and Vrsr2 is connected to the data signal reference voltage (Vrsr2).
r*fL or Vraf2 is connected to FE via resistor R4
Added to T16. FET 16 controls the gain of operational amplifier 15 based on the applied voltage value. That is,
If the disable signal 105 indicates an audio signal, the switch circuit 17 selects V r*fl and switches the FET
V r*rl is added to the signal 16, and the operational amplifier 15 provides an attenuation amount to obtain a predetermined signal level that is optimal for the audio signal. When the disable signal 105 indicates a data signal, the switch circuit 17 selects Vr@rz, and vo is applied to the FET 16, and the amount of attenuation is set to a predetermined signal level that is optimal for the data signal. It is given by an operational amplifier 15.

As described above, the preset audio signal reference voltage and data signal reference voltage are set to the disable signal 1.
05 and applying it to the FET 16, it is easy to automatically set the optimum signal level.

Further, the echo suppressor control circuit 14 is a circuit that has the respective functions of the echo suppressor circuit 7, the transmission echo control circuit 5, and the reception echo control circuit 8 in the conventional example shown in FIG.

That is, the echo suppression control circuit 14 receives the output signal of the automatic transmission level setting circuit 13 and the output signal of the reception baseband processing circuit 10 as input, and detects an echo signal by comparing the levels of the transmitted signal and the received signal. Based on the disable signal 105 output from the tone disabler circuit 6, it outputs a transmission echo suppression control signal 108 indicating that the baseband signal is a transmission echo signal when the baseband signal is an audio signal, and suppresses the transmission echo. Controls the switch circuit 2 to inhibit output of an echo signal. In addition, when the baseband signal is an audio signal, reception echo suppression control signal 1 indicating that it is a reception echo signal
09 to control the reception echo attenuation circuit 11 to attenuate the echo signal.

(Effects of the Invention) As explained above, the present invention enables a baseband signal to be set to a predetermined signal level suitable for an audio signal based on a disable signal indicating whether the baseband signal is an audio signal or a data signal. By automatically selecting a means for setting the baseband signal to a predetermined signal level appropriate for the data signal and a means for setting the signal level to a predetermined signal level appropriate for the data signal, the baseband signal can be automatically set to the appropriate signal level in either audio signal transmission or data signal transmission. This has the advantage of being easy to set up.

In addition, there is no need to manually make detailed signal level adjustments and settings each time audio signal transmission changes to data signal transmission.If you set an appropriate signal level for the data signal at the initial stage, the data signal By automatically setting an appropriate signal level for a data signal, it is possible to transmit a data signal with good BER characteristics even for a data signal with a high transmission rate.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a modulator/demodulator according to an embodiment of the present invention, Fig. 2 is a circuit diagram of an automatic transmission level setting circuit, Fig. 3 is a block diagram of a conventional modem/modulator, and Fig. 4 is a diagram of a baseband input signal level pair. FIG. 3 is a code error rate characteristic diagram. 1... Manual transmission level setting circuit, 2...
...Transmission echo switch circuit, 3...Transmission baseband processing circuit, 4...Modulation circuit, 5
......Transmission echo control circuit, 6...Tone disabler circuit, 7...Echo suppressor circuit, 8...Reception echo control circuit, 9.
... Demodulation circuit, 10 ... Reception baseband processing circuit, 11 ... Reception echo attenuation circuit, 12 ... Reception level setting circuit, 13 ...
...Automatic transmission level setting circuit, 14...
-Echo suppression control circuit, 15... operational amplifier, 16... field effect transistor, 17
......Switch circuit, 101...Baseband input signal, 102...IF output signal,
103...IF input signal, 104...
... Baseband output signal, 105 ... Disable signal, 106 ... Transmission echo suppression signal, 107 ... Reception echo suppression signal, 108 ... Transmission echo suppress control signal,
109... Reception echo suppression control signal. Agent Patent Attorney Yoshi Hachiman Hiroshi Hiroshi's exhortation to expropriation of n-ticket power ``Senban'' ? 3. R1fi-
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Claims (1)

[Claims] A function to set the input signal to a predetermined signal level suitable for a voice signal and a function to set the input signal to a predetermined signal level suitable for a data signal by inputting a baseband signal that is a voice signal or a data signal in a telephone signal band. and selects the two functions by controlling a disable signal indicating whether the baseband signal is an audio signal or a data signal, and automatically sets and outputs the baseband signal at an appropriate signal level. a transmission level setting means; taking the output signal of the automatic transmission level setting means as an input and controlling the output signal of the input signal based on a transmission echo suppression control signal indicating that the baseband signal is a transmission echo signal when the baseband signal is an audio signal; a transmitting echo switch means that performs an output prohibition operation with respect to the transmitting echo signal; a transmitting baseband processing means that processes the transmitting baseband signal by inputting the output signal of the transmitting echo switch means; a modulator for modulating an intermediate frequency (IF) carrier wave signal using the output signal as an input and outputting an IF output signal for FDMA/SCPC communication; a received FDMA/SC
demodulation means for demodulating a baseband signal from an IF input signal for PC communication; reception baseband processing means for inputting the output signal of the demodulation means and processing a reception baseband signal; and output of the reception baseband processing means. Receiving echo attenuation means receives a signal as input and performs an attenuation operation on the received echo signal in the input signal based on a received echo suppress control signal indicating that the baseband signal is a received echo signal when the baseband signal is an audio signal. and; reception level setting means for inputting the output signal of the reception echo attenuation means and outputting a baseband signal set to a predetermined signal level; and the output signal of the automatic transmission level setting means and the reception baseband processing means. With the output signal of and as input,
It has a function to detect tone signals from baseband signals, determines whether the tone signal is detected as a data signal or an audio signal, and outputs a disable signal indicating whether the baseband signal is an audio signal or a data signal. tone disabling means; having a function of detecting an echo signal by receiving the output signal of the automatic transmission level setting means and the output signal of the reception baseband processing means and comparing the levels of the transmitted signal and the received signal; Based on the disable signal output from the tone disabler means, a transmission echo suppression control signal indicating that the baseband signal is a transmission echo signal when the baseband signal is an audio signal, and a transmission echo suppression control signal indicating that the baseband signal is a reception echo signal when the baseband signal is an audio signal. A modulator/demodulator comprising: echo suppression control means for outputting a received echo suppression control signal indicating that there is a received echo suppression control signal.