JPH10163929A - Adaptive equalizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of equalization ability without being affected by noise components. SOLUTION: The noise components in a reception band are extracted by a BPF 90 and the reception level of the noise components is analyzed at all times in a detection circuit 91. When it is judged that the reception level of the noise components is higher than a prescribed level in a noise judgement device 92, a tap updating processing in an adaptive equalization part 81 is temporarily interrupted. When it is judged that the reception level of the noise components is lower than the prescribed level, the tap updating processing is restarted. Thus, abnormality or the like in a transmission route is easily detected and the degradation or divergence of the adaptability is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adaptive equalizer for automatically performing equalization processing during data transmission.

[0002]

2. Description of the Related Art A modem or the like which converts digital signal data into an analog signal and performs data transmission is usually used.
An adaptive equalizer that automatically performs an equalization process to follow a transmission characteristic that changes every moment is provided. This adaptive equalizer sends a training signal at a predetermined timing, thereby estimating the transmission characteristics of the transmission path, determining a correction specification for the transmission characteristics, changing the equalizer characteristics according to the correction specifications, and When an abnormality in the transmission path such as an instantaneous interruption is recognized, the equalization processing is temporarily interrupted to prevent the equalization capability of the equalizer from deteriorating or diverging.

[0003]

However, the above-mentioned conventional adaptive equalizer has the following problems. In some cases, it is difficult to detect abnormalities in the transmission path due to the influence of noise components in the receiving band.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is an adaptive equalizer capable of preventing deterioration of the equalization capability of an equalizer without being affected by noise components in a transmission path. The purpose is to provide.

[0005]

In order to achieve the above object, the invention according to claim 1 comprises an equalizing means for performing an equalizing process, a noise level in a reception band which is constantly detected, and a noise level in the receiving band. When the noise level becomes equal to or lower than a predetermined level, the equalization processing is temporarily stopped, and when the noise level becomes equal to or lower than the predetermined level, the equalization processing is restarted. That is, the equalization processing control means detects the noise level in the reception band, and temporarily interrupts the equalization processing when the noise level exceeds a predetermined level. Further, the noise detecting means detects the noise level even during the interruption of the equalization processing, and restarts the equalization processing when the noise level falls below a predetermined level.

According to a second aspect of the present invention, in the adaptive equalizer according to the first aspect, the equalization processing control means sets the reception band to a main signal frequency domain and other frequency domains. The noise level is detected by dividing the signal and measuring the reception level in a frequency region other than the main signal frequency region. For example, by providing a band-pass filter as the equalization processing control means, by trapping only the frequency region other than the main signal in the reception band via the band-pass filter and measuring the reception level,
Detect noise level.

Further, according to a third aspect of the present invention, in the adaptive equalizer according to the first or second aspect, the noise detecting means detects a noise level during underwater acoustic communication. For example, when digital imaging data from an underwater camera is converted into an analog sound signal and transmitted to an observation ship on the water surface, it is known that the noise level increases in a burst due to the operation of the thruster of the observation ship and the like. The noise level is positively detected to control the equalization processing.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an outline in which an adaptive equalizer according to an embodiment of the present invention is applied to underwater image transfer, FIG. 2 is a block diagram showing a configuration of an image data transmitting apparatus, and FIG. The configuration of the receiving device is shown by a block diagram.

In this embodiment, as shown in FIG. 1, underwater digital image data taken by
The signal is modulated into a signal such as a K signal or a QAM signal, and the signal is converted into an analog signal and transferred as an acoustic signal to the observation ship 10 on the water surface. The sound signal received by the observation ship 10 is converted into digital image data. The adaptive equalizer of the present invention is applied to modulation / demodulation processing of demodulation.

Of course, the scope of application of the present invention is not limited to the above-described one, and is applicable to all modulation and demodulation processes for converting digital signal data into analog signals and vice versa during data communication. For example, the present invention can be applied to a modem used for transmitting digital data via a general public line.

The diving observation boat 100 includes an image data transmitting device 110 whose block diagram is shown in FIG. 2. Digital image data captured by the underwater camera 120 is input to a modulator 130 and is supplied with a PSK signal or QAM. Modulated into a signal. Thereafter, the signal is converted into an analog signal by the D / A converter 140, power-amplified by the power amplifier 145, and transmitted as an acoustic signal via the transmitter 150.
On the other hand, as shown in the block diagram of FIG. 3, the observation ship 10 on the water surface has an image data receiving device 20 composed of a plurality of circuit groups.
The acoustic signal transmitted via the transmitter 150 is received by the receiver 30 and then the preamp 35
, And is converted into a digital signal by the A / D converter 40.

Here, a signal frequency component in a reception band in which the receiver 30 can receive a signal will be considered. FIG. 4 is a graph showing signal frequency components in the reception band (frequencies fL to fH), and a band extending to a higher frequency band (fs2 to fH) corresponds to a band of the acoustic signal as a main signal component. And the lower frequency band (f
The band extending from L to fS1) corresponds to a band for detecting noise. The noise component is mainly caused by the operation of the thruster or the like of the observation ship 10, and when the level of the noise component becomes extremely high, the equalization capability of the adaptive equalizer described later deteriorates,
An adverse effect such as divergence occurs.

The digital signal converted by the A / D converter 40 in order to extract the main signal component is input to a BPF (Band Pass Filter) 50, where the band is converted into a band between the frequency ranges fS2 to fH. After the restriction, the demodulation processing is performed in the synchronous detection circuit 60, and the demodulation processing is input to the adaptive equalizer 70. The adaptive equalizer 70 includes a timing extraction circuit 80, an adaptive equalizer 81, an error determiner 82, a phase control circuit 83, and a phase equalizer 84 as the above equalizing means.

The digital signal demodulated by the synchronous detection circuit 60 is supplied to a timing extraction circuit 80 and an adaptive equalizer 8.
1 and the timing extraction circuit 80 determines an appropriate time interval such as a transmission symbol interval.
The input signal is sampled by the adaptive equalizer 81 based on the same time interval, and supplied to an adaptive filter (not shown). Then, the output from the adaptive filter is input to an error determiner 82 via a phase equalizer 84 described later.

On the other hand, the error determiner 82 can determine the adaptive error and the phase error, and at the sampling timing determined by the timing extracting circuit 80, determines the tap coefficient of the adaptive filter based on the adaptive error. It sequentially updates (tap update processing) and outputs the same phase error to the phase control circuit 83. Then, the phase control circuit 83 operates the phase equalizer 84 to compensate for the input phase error. The digital signal that has been subjected to the equalization processing in this way is input to a display 85 via an error determiner 82, and displayed on the display 85 as an image.

Further, the adaptive equalizer 70 includes a BPF 90, a detection circuit 91, and a noise discriminator 92 as the equalization processing control means. The BPF 90 limits the receiving band to a signal consisting of only noise distributed in the low-frequency side frequency range fL to fH and outputs the signal to the detection circuit 91.
Then, the reception level of the noise is analyzed by the detection circuit 91 and is input to the noise determination unit 92. The noise determiner 92 determines whether or not the reception level of the noise analyzed by the detection circuit 91 is equal to or higher than a predetermined level. When the noise is determined to be equal to or higher than the predetermined level, the tap update processing is performed. Send a signal to interrupt. When this signal is received by the adaptive equalization unit 81, the tap update processing is immediately interrupted.

On the other hand, while the adaptive equalizer 81 interrupts the tap update process, the detection circuit 91 analyzes the reception level of the input noise, and the noise determination unit 92 outputs the noise. When recognizing that the reception level has become equal to or lower than a predetermined level, the adaptive equalization unit 81 transmits a signal for restarting the tap update process, and upon receiving this signal, restarts the tap update process.

That is, when the reception level of the noise increases, the adaptive error increases, and the equalization capability of the adaptive equalizer 81 is significantly deteriorated or diverged. The tap update processing is temporarily interrupted when the noise level is equal to or higher than a predetermined level, and the tap update processing is resumed when the noise reception level is equal to or lower than the predetermined level, thereby avoiding such a problem.

In this embodiment, the noise (fL) in the lower frequency band of the main signal components (fs2 to fH) is used.
To fs1), it goes without saying that the level can be changed as appropriate as long as it detects noise components in the receiving band. To explain this, for example, when a main signal component is divided into a plurality of noise components on a low frequency side and a high frequency side in a receiving band and a noise component is present, the noise level is once set in a plurality of bands by dividing each band. , The tap update process may be controlled to be interrupted when the noise level in one of the bands is equal to or higher than a predetermined value.

Next, the operation of this embodiment will be described. The dive survey boat 100 includes an image data transmission device 110. Photographing data captured by the underwater camera 120 is modulated into a PSK signal or a QAM signal by the modulator 130, and is transmitted by the D / A converter 140. After being converted into an analog signal, the power is amplified by the power amplifier 145 and the
The signal is transmitted as an acoustic signal via the reference numeral 50. On the other hand, the observation ship 10 on the water surface is provided with the image data receiving device 20, receives the above acoustic signal by the receiver 30, amplifies it by the preamplifier 35, and then amplifies it by the A / D converter 40. Convert audio signals to digital signals. Thereafter, only the main signal components (frequency fS2 to fH) are extracted by the BPF 50, demodulated by the synchronous detection circuit 60, and input to the adaptive equalizer 70. Then, as described above, the timing extraction circuit 8
The tap updating process is performed using a circuit group including 0, an adaptive equalizer 81, an error determiner 82, a phase control circuit 83, and a phase equalizer 84.

Further, the adaptive equalizer 70 includes a BPF 9
At 0, the noise component in the receiving band (frequency fL to fS1)
Only, and the reception level of this noise component is detected by a detection circuit 9.
1 is always analyzed, and the result is input to the noise determiner 92. When the reception level of the noise component becomes equal to or higher than a predetermined level, the noise determiner 92 sends a signal for temporarily interrupting the tap update processing, and the adaptive equalizer 81
Suspends the tap update processing upon receiving this signal.

When the reception level of the noise component falls below a predetermined level, the noise determiner 92 sends out a signal for restarting the tap update processing, and when the adaptive equalizer 81 receives this signal, the tap update processing is started. Resume.

As described above, the noise component in the reception band is extracted by the BPF 90, the reception level of the noise component is always analyzed by the detection circuit 91, and the noise determination unit 92
When it is determined that the reception level of the same noise component is equal to or higher than the predetermined level, the tap updating process in the adaptive equalizer 81 is temporarily interrupted, and the reception level of the same noise component is determined to be equal to or lower than the predetermined level. Then, since the tap update process is restarted, an abnormality or the like in the transmission path can be easily detected to prevent deterioration of the adaptive capability or divergence.

[0024]

As described above, the present invention can provide an adaptive equalizer capable of easily detecting an abnormality or the like in a transmission path and preventing deterioration of adaptive capability or divergence. According to the second aspect of the present invention, the reception band is divided into bands in a predetermined frequency range, so that noise components can be easily detected. Further, according to the third aspect of the present invention, the reliability at the time of acoustic communication can be improved by positively detecting a burst-like noise component caused by the thruster operation of the observation ship.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline in which an adaptive equalizer according to an embodiment of the present invention is applied to underwater image transfer using an acoustic signal.

FIG. 2 is a block diagram illustrating a configuration of an image data transmission device.

FIG. 3 is a block diagram illustrating a configuration of an image data receiving device.

FIG. 4 is a graph showing a frequency distribution of a main signal component and a noise component in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Observation ship 20 Image data receiving apparatus 30 Receiver 35 Preamplifier 40 A / D converter 50 BPF 60 Synchronous detection circuit 70 Adaptive equalizer 80 Timing extraction circuit 81 Adaptive equalizer 82 Error discriminator 83 Phase control circuit 84 Phase Equalizer 85 Indicator 90 BPF 91 Detection circuit 92 Noise determiner 100 Diving survey boat 110 Image data transfer device 120 Underwater camera 130 Modulator 140 D / A converter 145 Power amplifier 150 Transmitter

Claims (3)

[Claims] An equalizing means for performing an equalizing process, and a noise level in a receiving band is constantly detected,
Equalization processing control means for temporarily suspending the equalization processing when the noise level becomes equal to or higher than a predetermined level, and restarting the equalization processing when the noise level becomes equal to or lower than the predetermined level. An adaptive equalizer characterized by the following. 2. The adaptive equalizer according to claim 1, wherein said equalization processing control means divides a reception band into a main signal frequency region and a frequency region other than the main signal frequency region. An adaptive equalizer characterized by detecting the noise level by measuring a reception level in a frequency domain other than the above. 3. The adaptive equalizer according to claim 1, wherein said noise detecting means detects a noise level during underwater acoustic communication.