JPS6352502B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a repeater for a PCM (Pulse Code Modulation) or digital transmission system, and in particular to a device for compensating transmission line characteristics therein. It is related to.

[Technical background of the invention and its problems]

Normal automatic line build out
The circuit (hereinafter referred to as the ALBO circuit) provides variable equalization within a primary equalization feedback control loop to correct for primarily frequency-dependent losses due to line length changes. However, variations in cable characteristics and signal level changes due to cable type, such as whether the insulation is paper or plastic, all affect repeater characteristics. HDB3 signals may or may not be scrambled to use high efficiency line codes such as those known as 4B3T described in U.S. Pat. No. 3,611,141.
Since codes such as those known as (dense bipolar 3) contain more energy, especially in lower frequency bands, accurate equalization of line losses is required.

Highly multiplexed PCM systems, e.g.
A known equalizer for 43 channels at 2.37 Mbit/s is shown in FIG. This device uses a so-called "eye diagram" with a carefully designed ALBO circuit 12 to provide accurate equalization for different line length ranges.
(or "eye pattern") A primary equalization control loop is provided to maintain a constant height. The equalized signal is taken out from point X in Figure 1,
is applied to the ALBO peak detector 10. Detector 10 detects the peak or "height" of the eye diaphragm. This peak value is amplified and supplied to the diode circuit 11. diode circuit 1
The output of 1 is used to control equalization of the ALBO circuit 12.

However, when a specific frequency band (low frequency band in this case) contains a lot of energy like the 4B3T code described above, it is difficult to perform accurate equalization using this alone. Therefore, in conventional equipment, after installing the repeater,
An adjustment resistor is provided in the ALBO circuit 12 so that the repeater can be adjusted for a specific frequency band in the diagram, for example, a low frequency band component in the case of a 4B3T code.

However, in a device having such a configuration, it is necessary to adjust the adjustment resistance according to the type of cable, the characteristics of the input cable, etc., which not only requires complicated work but also is not easy to adjust accurately.

[Summary of the invention]

This invention was made in view of these points, and it is possible to automatically compensate for transmission line characteristics.
The purpose is to provide repeaters for PCM or digital transmission systems.

The present invention is characterized in that a repeater for a digital transmission line system is provided with an automatic line build-out circuit having a first equalization feedback control loop, the repeater comprising a controllable variable impedance means, and wherein the automatic line build-out circuit an equalizer circuit coupled to an input of the automatic line build-out circuit and at least one second feedback control loop coupled between an output of the automatic line build-out circuit and the equalizer circuit;
The second feedback control loop includes a wave generator coupled to the output of the automatic line build-out circuit;
a peak detector coupled to the output of the waver, the waver passing through a portion of the frequency spectrum of the output of the automatic line build-out circuit that contains a large amount of signal energy; The peak detector is in the configuration of a repeater for a digital transmission line system for controlling the controllable variable impedance means of the equalizer circuit to generate a control signal that is coupled to compensate for transmission line characteristics.

Thus, in the present invention, in a repeater with an automatic line build-out circuit having a first equalization feedback control loop, a Second
A feedback loop is provided, and in this feedback loop, only a specific frequency band containing a large amount of signal energy is extracted from the frequency spectrum of the output of the ALBO circuit using a wave generator, and the equalizer circuit is controlled based on this. Therefore, when a large amount of energy is contained in a specific frequency band like the 4B3T code mentioned above, the equalizer circuit should be adjusted to the transmission path characteristics corresponding to the signal in that specific frequency band. Automatically build/build the signal after equalizing the transmission path characteristics for the signal in a specific frequency band.
By equalizing in the out circuit, it is possible to accurately equalize the line loss even in a signal where the energy is concentrated in a specific band. Furthermore, unlike the manual adjustment of the ALBO circuit's resistance as described above, this equalization is automatic, provides quick and accurate equalization, and does not require adjustment each time it is installed.

The waveform generator used in this second feedback loop is one that selects the frequency band in which equalization control is performed as described above, but in the case of the 4B3T code, which has a lot of energy in the low frequency part as described above, , a low-pass waveformer capable of passing this band can be used.

[Embodiments of the invention]

Examples will be described below.

The repeater shown in FIG. 2 is the basic repeater of FIG. 1 with the addition of a second feedback control loop.
This second feedback control loop includes a wave generator 20 that receives a signal from point X which is the output of the ALBO circuit, similar to the ALBO peak detector 10, and
a peak detector 21 to which the outputs of the peak detector 21 are coupled and output a control signal for controlling a controllable variable impedance 22 in the equalizer circuit 13 (shown as a separate block from 13 for clarity in the figure); Contains. As mentioned above, the wave generator 21 extracts a signal in a frequency band in which a large amount of energy is concentrated in order to perform appropriate equalization on the signal in that band. Well then
Since the 4B3T code has energy concentrated in a low frequency band, a low-pass waver is used as the waver 20. The low frequency band signal extracted by this wave detector 20 is sent to a peak detector 2.
1, where the peak value is detected and amplified to the variable impedance 22 in the equalizer circuit 13.
is supplied as a control signal. Low pass wave generator 2
0 ensures that the second loop is only responsive to the low frequency content of the eye diagram for the control of the equalizer circuit 13. This automatic control of equalizer circuit 13 provides equalization for the best eye diagram regardless of cable type or input cable characteristics.

Although the principles of the invention have been explained based on specific examples, these are merely illustrative and do not limit the scope of the invention as set forth in the claims.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional equalizer.
FIG. 2 shows a repeater equalizer according to an embodiment of the present invention. 10... ALBO peak detector, 11... Diode circuit, 12... ALBO circuit, 13... Equalizer, 20... Low pass wave generator, 21... Peak detector, 22... Variable impedance.

Claims (1)

[Scope of Claims] 1. A repeater for a digital transmission line system equipped with an automatic line build-out circuit having a first equalization feedback control loop, comprising: a controllable variable impedance means; an equalizer circuit coupled to an input of the circuit; and at least one second feedback control loop coupled between an output of the automatic line build-out circuit and the equalizer circuit. , the second feedback control loop comprising a wave generator coupled to an output of the automatic line build-out circuit;
a peak detector coupled to the output of the wave generator, the wave generator passing substantially only those portions of the frequency spectrum of the output of the automatic line build-out circuit that are rich in signal energy. a digital transmission line, wherein the peak detector generates a control signal that is coupled to control the controllable variable impedance means of the equalizer circuit to compensate for transmission line characteristics. System repeater. 2. The repeater according to claim 1, wherein the wave device is a low-pass wave device. 3. The first loop includes a second peak detector coupled to the output of the automatic line build-out circuit, and between the output of the second peak detector and the automatic line build-out circuit. 3. A repeater according to claim 1, further comprising a diode circuit coupled to said automatic line build-out circuit for controlling said automatic line build-out circuit.