JPS6055743A - Bi-directional repeater - Google Patents

Abstract

PURPOSE:To improve the stability of sounding by connecting a loss circuit, which has a resonance point on the outside of a transmission band, in series to an amplifier in a bi-directional repeater of direction separating filter type which uses the single amplifier. CONSTITUTION:One loss circuit LS is connected in series to each of the input side and the output side of an amplifier AMP. Therefore, even if the impedance of the line side viwed from a direction separating filter DF is changed to change the phase between sneak signals A and B, the quantity of sneak attenuation in a separate band is held large because of insertion of loss circuits LS. Consequently, the generation of sounding is suppressed sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a bidirectional repeater using a single amplifier that is inserted into a transmission line and improves sound stability.

(2) Background of the technology When bidirectional communication is performed through a transmission path consisting of a single line such as a submarine cable, several stages of repeaters using a single amplifier are connected in cascade. For example, in the direction separation filter type shown in FIG. 1, the frequency band is separated into a high group transmission band and a low group transmission band, and the frequency bands are amplified so as not to interfere with each other. If a fault occurs along the transmission line and the line impedance seen from the repeater changes from its designed value, the repeater may oscillate. The signal of the 5V-OSC supervisory signal oscillator built into each repeater can be measured from the terminal station to determine where in the transmission path the fault has occurred, but due to the noise caused by the repeater oscillation mentioned above, It becomes difficult to determine the location of the failure point because sufficient measurements cannot be made. Therefore, it is necessary to improve the sound stability of the repeater due to changes in line impedance.

(3) Prior art and problems In the bidirectional repeater shown in Fig. 1, an amplifier AMP is connected as shown in the figure to a direction separation filter DF connected to the transmission fiber TL via power separation filters PSFI and PSF2. ing. The low group transmission band signal is transmitted from the left side, passed through the low pass filter LPF, amplified by the amplifier AMP, passed through the low pass filter LPF again, and then transmitted to the right side via the power separation filter PSF2. The high transmission band signal from the right reaches the amplifier AMP via the high-pass filter/phase inversion transformer T2 and is amplified. The amplifier output is then transmitted to the left via the phase inversion transformer 7.1, the high-pass filter HPF, and the power separation filter PSF1. At this time, from the direction separation filter DF to the power separation filter PS
If the line impedance looking at the F side is the design value in the normal state, looking at the wrap-around signals shown by arrows A and B in the direction separation filter DF, the composite signal of A and B in the separation band is phase inversion transformed. offset by the vessel. At this time, as shown by the solid line in FIG. 2, if we take the ratio of the frequency to the amount of wrap-around attenuation, the amount of wrap-around attenuation in the separation band is large. At that time, compared to the gain of the amplifier AMP, if the wrap-around attenuation in the separation band was larger, the amplifier would not oscillate no matter how many times the signal wrap-around was repeated. If a fault occurs in the transmission line, the line impedance seen from the directional separation filter DF changes, and a loop signal A is generated.

The phase difference of B is different from normal. Therefore, in the phase inversion transformer, even if the signal phase is inverted, the loop signals A+B in the separation band are not canceled out, and as shown by the broken line in Figure 2, the loop attenuation is less than the gain of the amplifier, and the A signal is transmitted in a loop within the separation filter many times, producing a sound. Therefore, the characteristics of the low-pass filter and high-pass filter are made steep, and the wraparound attenuation is designed to be kept as large as possible. However, due to mounting issues, there is a limit to the number of components that make up the filter, and the desired number of components is limited. Characteristics were difficult to obtain. In Fig. 2, the dashed line is the amplifier AM.
2 shows a frequency versus gain characteristic curve of P. The amplifier gain is designed to be high for high frequencies.

(4) Object of the Invention An object of the present invention is to provide a two-way repeater using a vehicle-amplifier, which improves the above-mentioned drawbacks and improves sound stability with a relatively simple structure.

(5) Configuration of the Invention The configuration of the present invention to achieve the above-mentioned object is a two-way repeater that is inserted into a transmission line and uses a single amplifier in the form of a directional separation filter, which has a resonance point in the separation band. An amplifier in which loss circuits are connected in series is configured in place of the amplifier.

(6) Embodiment of the Invention FIG. 3 is a block diagram showing an embodiment of the invention, corresponding to FIG. 1. In FIG. 3, LS is a circuit having a loss peak in the separation band. 1 each on the input and output sides of the amplifier AMP.
loss circuits are connected in series, and the amplifier AMP shown in FIG. : The configuration has been replaced. Therefore, even when the impedance seen from the directional separation filter on the line side changes and the phase difference between the wraparound signals A and B changes, the loss circuit LS is inserted, so the wraparound attenuation within the separation band can be maintained large. , the generation of noise can be sufficiently suppressed.

Further, the loss circuit may be only 14 rM and may be provided on the input side or the output side of the amplifier.

(7) Effects of the Invention In this way, according to the present invention, it is possible to obtain a bidirectional repeater that operates stably against noise using a single amplifier, even with a relatively simple configuration.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a conventional bidirectional repeater, Fig. 2 is a diagram showing the characteristics of the amount of wrap-around attenuation versus frequency in Fig. 1, and Fig. 3 is a diagram showing the configuration of an embodiment of the present invention. It is a diagram. DF one-way separation filter TL--One transmission line AMP-・Amplifier L P F-Low pass filter HP F
”-m-High-pass filter TI, T2-Phase inversion transformer LS--Loss circuit Patent applicant Fujitsu Co., Ltd. Agent Patent attorney Eisuke Suzuki

Claims (1)

[Claims] In a bidirectional repeater that is inserted into a transmission path and uses a single amplifier in the form of a direction separation filter, the amplifier is replaced with an amplifier in which a loss circuit having a resonance point outside the transmission band is connected in series. A two-way repeater featuring: