JPH0257039A - Modem device - Google Patents

Abstract

PURPOSE:To prevent disturbance in correcting operation when momentary interruption is recovered by executing the detection of the instaneous interruption of a line based on the output timing of a high speed amplifying signal. CONSTITUTION:The high speed amplifying signal is supplied through an error signal switching part 7 to an equalizing and phase control part 3. Thus, the instaneous interruption of the line in the equalizing and phase control part 3 is detected based on the output timing of the high speed amplifying signal. A correcting value for correcting operation in the equalizing and phase control part 3 is held simultaneously when the high speed amplifying signal is turned on. Thus, when the instaneous interruption is recovered, the disturbance is not generated in the correcting operation. When the level of a reception signal is frequency lowered by the fluctuation, etc., of a line characteristic, since the holding operation of the correcting value for correcting operation is not executed, the correcting value for correcting operation is successively updated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement of a modem device suitable for, for example, QAM data transmission.

(Prior Art) FIG. 4 is a block diagram schematically showing the configuration of a modem device conventionally used for QAM data transmission.

As shown in the figure, this modem device converts a received signal into a variable gain amplification section 1. The demodulation section 22 is sequentially passed through the equalization and phase control section 3 and the code determination section 4, so that the code string constituting the received signal is successively reproduced and output.

The variable gain amplification section 1 is for making the level of the received signal constant, and this control is performed based on the low speed amplification signal and the high speed amplification signal output from the amplitude determination section 5.

That is, the amplitude determination section 5 outputs a low-speed amplified signal when the average value of the received signal is smaller than a specified value, and outputs a high-speed amplified signal when the peak value is continuously smaller than the specified value for a certain period of time. .

The gain in the variable gain amplification section 1 increases gradually when the low-speed amplification signal is turned on, but increases rapidly when the high-speed amplification signal is turned on.

Therefore, as shown in FIG. 5, for example, when a momentary interruption occurs in the received signal, first the low-speed amplification signal is turned on, and the gain of the amplification section 1 gradually increases, and then the high-speed amplification signal is turned on. When the amplification signal is turned on, the gain of the amplification section 1 increases rapidly.

On the other hand, the equalization and phase control section 3 performs predetermined equalization correction and phase correction based on the error signal detected by the error signal detection section 6 and supplied via the error signal switching section 7. This correction operation is performed by sequentially updating the correction value for correction based on the error signal.

When a momentary interruption occurs in the received signal, the value of this correction correction value is maintained at the state immediately before the momentary interruption in order to prevent disturbances in the correction operation when the momentary interruption is recovered. It looks like this.

Conventionally, this correction value holding operation has been performed at the timing when the low-speed amplification signal is turned on, as shown in FIG.

In addition, the part marked as raw correction value A in Fig. It is something.

(Problem to be solved by the invention) However, in such a conventional modem device,
When the level of the received signal drops frequently due to fluctuations in line characteristics, etc., as shown in Figure 6, the correction value for correction is frequently held by turning on the 11th speed incremental signal. However, there was a problem in that the characteristics of the modem deteriorated as a result.

This invention was made in order to solve the above-mentioned problem, and its purpose is to maintain the same level of performance even if the level of the received signal frequently decreases due to fluctuations in line characteristics, etc. It is an object of the present invention to provide a modem device which continuously performs correction operations in the phase side details 3 and does not cause deterioration of the characteristics of the modem.

(Structure of the Invention) (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides that when the average value of the received signal is smaller than the specified value, the low-speed amplified signal is
It includes an amplitude determination section that outputs a high-speed amplification signal when the droplet wave value is continuously smaller than a specified value for a certain period of time, and a variable gain amplification section that amplifies the received signal has a gradual gain due to the low-speed amplification signal. In the modem device, the modem device performs rapid gain correction using the high-speed amplified signal, and maintains a correction value for corrective operation in the equalization and phase control section during the period when a momentary line disconnection is detected. The present invention is characterized in that the instantaneous line interruption is detected based on the output timing of the high-speed amplified signal.

(Function) According to this configuration, even if the level of the received signal frequently decreases due to fluctuations in line characteristics, the high-speed amplified signal is kept in the off state. The holding operation in the equalization and phase control unit 3 is not performed due to level fluctuations in the received signal, and therefore the characteristics of the modem are not deteriorated.

On the other hand, when a momentary interruption occurs, the high-speed amplification signal is turned on and the correction value for correction is held in the equalization and phase control section, which may cause disturbances in the correction operation when the momentary interruption is restored. do not have.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a modem device according to the present invention.

Incidentally, in the figure, the same components as those in the conventional example shown in FIG.

The feature of this embodiment device is that by supplying a high-speed amplified signal to the equalization and phase control unit 3 via the error signal switching unit 7, instantaneous line interruption can be detected in the equalization and phase control unit 3. is performed based on the output timing of the high-speed amplified signal.

In other words, as shown in Fig. 2, when a momentary interruption occurs in the received signal, the gain of the amplifying section 1 is initially gradually increased and then sharply increased depending on the timing of each of the low-speed amplified signal and the high-speed amplified signal. increases to

In addition, the correction value for the correction operation in the equalization and phase restraint section 3 is held at the same time as the high-speed amplification signal is turned on, and as a result, as in the conventional case, when the momentary power interruption is restored, the correction value is generated at d3 and the correction operation is disturbed. I won't let you.

On the other hand, if the level of the received signal frequently drops due to changes in line characteristics, etc., as shown in Figure 3, the low-speed amplified signal is turned on each time, but corrective action is not taken. Since the correction value is not held,
The value of the correction value for the correction movement f[ is updated sequentially, and equalization correction and phase correction are continuously performed regardless of such level fluctuations, thereby preventing deterioration of modem characteristics.

[Effect beam of invention]

As is clear from the above explanation, the present invention includes the following parts:
...Error signal detection section, 7...Error Shintan switching section.

According to the modem device, the equalization and phase correction operation can be continued smoothly in the UD section when recovering from a momentary power outage, but when a small fluctuation in the received signal level is The equalization and phase control section can continue to perform correction operations regardless of the level change, making it possible to use high-speed modems especially on lines with frequent level fluctuations, reducing communication costs. Therefore, it is possible to improve transmission reliability.

[Brief explanation of the drawing]

Fig. 1 is a block diagram schematically showing the configuration of the modem device according to the present defense, Fig. 2 is a waveform diagram showing the signal state when a momentary interruption occurs in the device, and Fig. 3 is the reception level in the device. FIG. 4 is a block diagram schematically showing the configuration of the conventional device. FIG. 5 is a waveform diagram showing the state of the conventional device when a momentary interruption occurs. FIG. FIG. 2 is a waveform diagram showing a state when the received signal level drops in a conventional device.

Claims (1)

[Scope of Claims] The receiver comprises an amplitude determination unit that outputs a low-speed amplified signal when the average value of the received signal is smaller than a specified value, and outputs a high-speed amplified signal when the peak value is continuously smaller than the specified value for a certain period of time, For the variable gain amplification section that amplifies the signal, gradual gain modification is performed using the low-speed amplification signal, rapid gain modification is performed using the high-speed amplification signal, and equalization and phase control are performed when a momentary line interruption is detected. 1. A modem device in which a correction value for a corrective operation in a section is held for a period of time, wherein the detection of the instantaneous line interruption is performed based on the output timing of the high-speed amplified signal.