JPS6046641A - Digital transmission repeater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a digital transmission repeater that compensates for low-frequency cut-off distortion caused by a power transfer device or the like in baseband transmission.

[Prior Art] Generally, in order to convert an analog signal into a digital signal and transmit it, the signal is sent out to a transmission line through the following steps: purlin conversion (sampling) → digitization → encoding.

Conventionally, balanced codes (bipolar codes) have been mainly used for code sequences after encoding, taking transmission path loss and repeater structure into account, but unipolar codes have been used from the perspective of transmission efficiency. Transmission is more efficient when using . However, when a unipolar code sequence is used, there is a drawback that the isoflowering causes interference between codes due to low frequency cut-off distortion, resulting in code errors and impossibility of correct transmission.

[Objective] The present invention has been made in view of the above-mentioned drawbacks of the prior art, and provides a digital system that prevents equalizer code amount interference and enables accurate transmission by providing a feedback circuit that compensates for low-frequency cut-off distortion. The purpose is to provide a transmission relay device.

[Example] An example of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining the configuration of an embodiment. In the figure, ■ is a transmission line signal input section, and 0 is a transmission line signal output section. A is a power separation filter, in which a pulse signal and a DC component for driving the repeater are superimposed on the signal transmission path, and the power separation filter a separates this signal and the DC component (low frequency component). This is a bypass filter that separates the b
is a waveform equalizer that removes the distortion caused by the frequency characteristics of the line from the received waveform that is distorted and attenuated in the transmission line, and amplifies and shapes it into an equalized waveform (squared sinusoidal wave) with a good S/N ratio. do. C is a timing circuit that generates trigger pulses for regenerating the phase of the pulses sent from the transmission line signal output section 0 at correct time intervals. d is an identification/regeneration circuit which identifies whether or not the value of the equalizer is greater than a threshold value at the time when the tri-force pulse occurs, and based on the result, regenerates and transmits the code.

In the conventional repeater, the signal component that has passed through the bypass filter a is input to the waveform equalizer, but if left as is, low frequency cut-off distortion causes code amount interference in the equalizer. ■ is a compensation circuit for low-frequency cutoff distortion according to the present invention;
It consists of a feedback circuit e, a delay circuit f, and a delay time control circuit g. If the bypass filter a is a 081st-order filter as shown in Figure 2 (A), then the transfer function is P-
As jω, V2 /Vl = 1-1/ (PCR+1) ・
It is expressed as (1). The second term on the right side of equation (1) indicates the transfer characteristic of the low-pass filter connected with a negative sign. Since the low-frequency cut-off by the bypass filter a is caused by the low-pass filter component, the feedback circuit e has a transfer characteristic that cancels out the low-pass filter component. The equivalent circuit is shown in FIG. 2(B). The delay circuit f is used to delay the low-frequency cutoff component inputted through the power filter 1111 a, and to make it coincide in time with the feedback compensation component from the transmission line signal output section O. The delay time control circuit g is a circuit that monitors the feedback compensation signal from the transmission line signal output section O and controls the delay time of the delay circuit f so that time matching with the input low-frequency cutoff component is always optimally performed. be. In addition, Fig. 3 (A) shows the electric scum vector distribution of unipolar code,
FIG. 3(B) shows the electric scum vector distribution of a balanced code. Here, f in FIGS. 3(A) and 3(B). is the pulse repetition frequency (clock frequency).

[Effects] As described above, according to the present invention, by providing a conventional repeater with a feedback circuit, a delay circuit, and a delay time control circuit, it is possible to completely compensate for the low-frequency cutoff distortion of the signal in the time domain and frequency domain. 5, it is possible to perform digital transmission with a low bit error rate using an efficient unipolar code sequence.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of one embodiment, and FIG. 2 (A
) is an equivalent circuit diagram showing the characteristics of the power separation filter, Figure 2 (B) is an equivalent circuit diagram showing the characteristics of the feedback circuit, and Figure 3 (A) is a graph diagram showing the electric scum vector distribution of a single-pole code. , FIG. 3(B) is a graph showing the electric scum vector distribution of a balanced code. Here, a...power separation filter, b...waveform vase, C...timing circuit, d...discrimination and regeneration circuit. e...Feedback circuit, f...Delay circuit 9g...Delay time control circuit. Figure 2 (B) Figure 3 (A) (B>

Claims (1)

[Claims] A digital transmission repeater for PCM communication, comprising feedback means for extracting a high-frequency cutoff component of a relay output signal and superimposing it on an input-side low-frequency cutoff signal, and a phase control means for matching the phase of the superimposition, the input side A digital transmission repeater characterized by compensating for low-frequency cutoff distortion of a low-frequency cutoff signal.