JPH048033A - Digital transmitter - Google Patents

Abstract

PURPOSE:To transmit a transmission signal without phase deviation even when a communication satellite or an optical fiber cable, etc., is in use by adjusting a digital signal at every transmission line automatically so that each delay time difference is eliminated. CONSTITUTION:A switch 103 switches digital data at every data to the position of (a) or (b) and a signal whose bit rate is halved is outputted to the terminals (a), (b), signal adders 107, 108 add a sync pattern and the result is transmitted through separate transmission lines 201, 202. A delay time comparator 308 counts the time difference of a sync pulse from sync detectors 306, 307, outputs a signal to a timing generator 309 controlling FIFOs 304, 305 so as to control the FIFOs 304, 305 in a such a manner that the delay times of the transmission lines 201, 202 are made equal to each other. Thus, the transmission of the digital signal using plural transmission lines is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital transmission device that transmits digital signals using communication satellites, optical fiber cables, and the like.

[Conventional technology]

When transmitting digital signals to a remote location, communication satellites, optical fiber cables, etc. are used as the transmission path, but the amount of information that can be transmitted (bit rate) is limited individually, and when transmitting a large amount of information at the same time, multiple A transmission line was used.

[Problem to be solved by the invention]

However, when the transmission paths are different, the time it takes to transmit the digital signal, that is, the delay time, is different, and on the receiving side, the digital signal may have a skew (phase shift) between each transmission path.
will occur. Therefore, it was necessary to make adjustments using a delay line or the like to compensate for this skew. Furthermore, if jitter (changes in delay time) occurs due to changes in the distance between the communication satellite and the earth base, data transmission will not be possible with just the above adjustments.

The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a digital transmission device that compensates for delay time differences between communication bases over long distances.

(Means for solving the problem) Therefore, in the present invention, in a digital transmission device that transmits digital signals via a plurality of transmission paths, the delay time difference of each of the digital signals occurring between the transmission paths is compensated for. A digital transmission device is characterized in that it is equipped with a compensating means.

Further, the compensating means includes a transmitter that adds a sync pattern to each digital signal at regular intervals, and a receiver that detects the sync pattern, adjusts the delay time difference thereof to be the same, and removes the sync pattern. The object of the present invention is to achieve the above object.

[Effect]

With the above configuration, it is possible to automatically adjust the delay time difference between digital signals generated between a plurality of transmission paths, and to transmit and receive digital signals without phase shift.

Further, the compensation means adds a sync pattern at regular intervals to the digital signal in the transmitting section, detects the sync pattern added in the transmitting section in the receiving section, measures the delay time difference, and makes the delay time difference of the digital signals the same. Adjust so that
By removing the sync pattern, a digital signal with no delay time difference can be obtained.

〔Example〕

FIG. 1 is a block diagram of a digital transmission device according to an embodiment of the present invention, and FIG. 2 is a timing chart of the embodiment shown in FIG. In addition, the same symbols in each figure are the same (equivalent)
Indicates the constituent elements.

In the figure, 101 is a digital encoding device that outputs a digital signal, and 301 is a digital encoding device 10.
1 is a digital decoding device that receives a digital signal output from the device. The difficult device may be an image transmission device, an audio transmission device, or the like. 103 is a switch that electrically switches the digital signal from the digital encoding device 101 for each piece of data; 104 and 105 are FIFOs (FIFOs) that create a space for inserting a sync signal;
106 is a sync pattern generator, and 107 and 108 are signal adders for adding the sync pattern.

201 and 202 are transmission paths that connect the transmitter C on the transmitter side and the receiver on the receiver side via the communication satellites A and B. In this embodiment, communication satellites A and B are used, but the same effects as described above can be obtained using other transmission media, such as optical fiber cables.

304 and 305 are FIFOs that adjust the delay time in the transmission paths 201 and 202, 306 and 307 are sync detectors that detect the sync patterns added by the signal adding devices 107 and 108, and 308 are sync detectors 306 and 3
A delay time comparator 309 compares the delay time using the sync detection signal output from the delay comparator 308.
, 305, a timing generator that outputs the delay amount to 303;
102 is a switch for switching the transmission data outputted from the FIFOs 304 and 305 for each piece of data; 102 is a switch 103 on the transmitting side; the FIFOs 104 and 105; and a sync pattern generator 106. A timing controller that controls the timing of the signal adder 1.07, 108, 302 is a receiving side FIFO 304, 305° sync detector 306,
307. Delay time comparator 308, timing generator 30
9. This is a timing roller that controls the switch 303.

Each transmission line 201 in this embodiment. The compensating means E for compensating for the delay time difference of -202 is the switch 103.
FIFO 104, 105, sink pattern generator 106
．． A transmitter C that adds a sync pattern to a transmission signal at regular intervals using a signal adder 107108 and a timing controller 102 that controls the timing thereof, and sync detectors 306, 307, . Delay time comparator 30B, timing generator 309. The FIFOs 304, 305, the switch 303, and the timing controller 302 that controls the timing of these elements detect the sink butterflies added in the transmitter C, measure the delay time difference, and make the delay time of each transmission path the same. It consists of a receiving section for adjustment.

(1) in FIG. 2 is the digital encoding device 101 on the transmitting side.
(2) is an output signal separated into a side and b side by switch 103, (3) is a transmission signal whose time axis is exchanged by FIFOs 104 and 105 and a sync pattern is added by signal adders 107 and 108. shows. Further, (4) shows the input signal of the sync detector 306 on the receiving side, (5) shows the output signal of the sync pulse, and (6) shows the sync detector 306.
7 shows the input signal, and (7) shows the output signal of the sync pulse. Furthermore, (8) eliminates the delay time difference with FIFOs 304 and 305, and the output signal after removing the sync pattern,
(9) shows the output signal decoded by the switch 303.

Next, the operation will be explained with reference to FIGS. 1 and 2.

FIG. 2 (1) output from the digital encoding device 101
) is input to the switch 103. The switch 103 switches the digital data one data at a time between the a side and the b side as shown in FIG. 2 (2), and outputs a signal whose bit rate has been halved to the a and b terminals.

A space for inserting a sync signal is created for each signal in FIFos 104 and 105, and signal adders 107 and 10
A sync pattern is added in step 8, and a transmission signal as shown in FIG. 2 (3) is sent out. In this sync pattern, signal adders 107 and 108 add signals at the same timing at certain intervals.

Each signal with a sync pattern is sent to a separate transmission path 201.
．． 202. Since the transmission paths 201 and 202 are completely different transmission paths, the transmission signals have a skew in delay time. In addition, communication satellites tend to have jitter in their transmitted signals due to the Doppler effect due to changes in distance from the earth.

Sink detectors 306, 307LL FIG. 2 (4).

Detecting the sink pattern of the transmission signal shown in (6),
When the sink pattern is created manually, the results are shown in Figure 2 (5) and (7).
) Outputs the sync pulse shown in Transmission lines 201, 20
2, if there is a difference in delay time, sync detection 8306.30
The sync pulses outputted by No. 7 are also outputted with the same time difference.

The delay time comparator 308 measures the time difference between the sync pulses shown in FIG. timing generator 309
is the signal from the delay time comparator 308, and the delay time of the transmission line 201 and the transmission line 202 are set to be the same.
Control 04,305.

At the same time as the above operations, the FIFOs 304 and 305 operate to remove the sync signal added on the transmitting side, as shown in FIG. 2 (8). Further, the signal shown in FIG. 2 (8) output from the FIFOs 304 and 305 is
, b terminal, and is returned to the form shown in FIG. 2 (9), which is the same as the signal output from the digital encoding device M101, and is input to the digital decoding device. As described above, digital signal transmission using a plurality of transmission paths becomes possible.

(Other Embodiments) In the above embodiment, two communication satellites A and B are used, and the transmission path 201
, 202 are two lines, but the switches 103, 303 . Signal adders 107, 108.
FIFO104,105°304.305. By increasing the number of sink detectors 306, 307, etc., it is possible to increase the number of transmission lines used.

Moreover, any combination of communication satellites, optical fiber cables, etc. can be used as the transmission lines 201 and 202.

(Effects of the Invention) As explained above, according to the present invention, even if there are a plurality of different transmission paths, it is automatically adjusted to eliminate the difference in delay time of digital signals for each transmission path. satellite,
Even if optical fiber cables are used, transmission signals without phase shift can be transmitted.

Therefore, a plurality of transmission paths can be used, which is convenient for large-capacity data transmission.

Further, the compensation means can be realized by a simple adding device by adding a sync pattern to a digital signal in a transmitting section, detecting the sync pattern in a receiving section, and adjusting the delay time difference.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital transmission device according to an embodiment of the present invention, and FIG. 2 is a timing chart of the embodiment shown in FIG. Note that in each figure, the same reference numerals indicate the same (equivalent) components. 102, 103----Timing controller 103.303-,... Switch 104.105,304,305-----FIFO
l 06------Sync pattern generator to7. t
os---Signal adder 201.202--Transmission line 306.307---Sink detector 308---
-Delay time comparator 309--Timing generators A, B--Communication satellite C--Transmitting section D--Receiving section E--Compensation means

Claims (2)

[Claims] (1) A digital transmission device for transmitting digital signals through a plurality of transmission paths, characterized in that the digital transmission device comprises compensation means for compensating for delay time differences between the digital signals occurring between the transmission paths. (2) The compensation means includes a transmitter that adds a sync pattern to each of the digital signals at regular intervals, and a receiver that detects the sync pattern, adjusts the delay time difference to be the same, and removes the sync pattern. 2. The digital transmission device according to claim 1, further comprising: