JPH0761049B2 - Time axis multiplexer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a time-axis multiplexing apparatus required for time-axis-multiplexing and transmitting a signal.

[Conventional technology]

In order to transmit the information generated from a plurality of signal generation sources through a transmission line smaller than the number of signal generation sources, it is necessary to multiplex the plurality of signals in a form separable on the receiving side. As one method of this signal multiplexing, there is time-axis multiplexing that switches and transmits a plurality of types of signals on one transmission path as time passes.

FIG. 4 (a) shows an example of the time-axis multiplexed signal.
S ₁ , S ₂ , and S ₃ represent respective signals generated from three types of signal sources. FIG. 4 (b) shows the time axis of the signal in FIG. 4 (a), and the waveform inserted between times t ₀ and t ₁ is the synchronization signal,
The reference timing when separating the signals S ₁ , S ₂ , and S ₃ on the receiving side is shown. Here, if the signal S _1, S _2, S ₃ continuously appearing signal rather than what appear at regular intervals as timing illustrated, to the signal _{S 1 (t 2 -t 1)} / (T ₇
−t ₀ ), for signal S ₂ (t ₄ −t ₃ ) / (t ₇ −t ₀ ), signal S ₃
On the other hand, if a time axis compression operation is performed at a ratio of (t ₆ −t ₅ ) / (t ₇ −t ₀ ), a signal can be transmitted without loss of information. At this time, each signal is separated at a cycle of (t ₇ −t ₀ ).

The levels of the start and end points of each signal separated in this way are
Since it is not always constant, when forming the signal shown in FIG. 4 (a), as shown in FIG. 5, a joint portion between the signals (here, only between the signals S ₁ and S ₂ is shown). A section of constant level is provided in A, the end of the signal S ₁ is once adjusted to that level, and then the start of the next signal S ₂ is adjusted to the constant level and connected. As described above, no particular consideration has been given to how to change the level difference at the joint portion.

[Problems to be solved by the invention]

As described above, the conventional time-axis multiplexer does not particularly take into consideration the level change that occurs at the end points of each signal.When a signal is switched by a switch, etc., a sharp level change occurs. Is limited, waveform distortion such as ringing will occur,
This causes distortion in the portions near each end of each signal.

The present invention has been made in order to solve the above problems. Even when the band is limited in the process of transmission, the time when waveform distortion such as ringing does not occur in the vicinity of the connection portion of time-axis multiplexed signals. The purpose is to obtain an axis multiplexer.

[Means for solving problems]

The time-axis multiplexer according to the present invention detects the end level of a preceding signal and the starting level of a following signal on the time axis and holds them, and an end-and-end level detecting and holding means, and a signal of the end and the starting end. A signal-to-signal connection means for generating a smooth signal-to-signal connection waveform based on the level and connecting the terminal end of the preceding signal and the signal start end of the next signal by the waveform is provided.

[Action]

In the present invention, the level at the end and the start of each signal that is time-axis multiplexed is detected and held, a smooth signal connection waveform is generated based on this detected level, and a smooth connection between the end points of each signal is made. Since a signal-to-signal connection waveform is generated to connect the start and end points of each signal, even if the high frequency component is attenuated due to band limitation during the transmission process, ringing etc. at the connection part of each signal that is time-axis multiplexed A time-axis multiplexed signal with less waveform distortion is output.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a time axis multiplexer according to an embodiment of the present invention. In the figure, 1, 2, 3 are A / D converters, 4, 5 and 6 are digital memories (RAM), 7 is a data selector, and 8 is R.
OM address generation circuit, 9 clock, control signal generation circuit, 10 ROM, 11 changeover switch, 12 D / A converter, 13-
Reference numeral 15 is an input terminal and 16 is an output terminal.

Numeral 20 is an end / start level detecting and holding means composed of a ROM address generating circuit 8 and a clock / control signal generating circuit 9. With this, the end level of the preceding signal on the time axis among the time axis multiplexed signals and the next level The start level of the signal following the and is detected and held. Reference numeral 30 denotes an inter-signal connecting means composed of a clock, a control signal generating circuit 9, a ROM 10 and a changeover switch 11, by which an appropriate waveform is generated according to the signal level of the terminal end and the starting end, and a signal preceding by the waveform is generated. Is connected to the beginning of the next succeeding signal.

Next, the operation will be described. Different signals S ₁ , S ₂ , S ₃ are input to the input terminals 13, 14, 15, respectively, and the respective signals are converted into digital signals by the A / D converters ₁ , ₂ , ₃ . The digital data of the signals S ₁ , S ₂ , S ₃ are written in the digital memories 4, 5, 6, respectively. The data written in the RAMs 4, 5 and 6 will be read out at a predetermined timing. At this time, the time axis compression operation is performed by reading out each data at a time interval shorter than that at the time of writing. The data for the signals S ₁ , S ₂ , and S ₃ written in the RAMs 4, 5 and 6 are read by the above method so that they do not overlap in time, and then output to one transmission path by the data selector 7,
It is connected to the input terminal 111 of the changeover switch 11. The data selector 7 selects and outputs one of the three data, and selects the output of the RAM currently read.

Next, the above process will be described with reference to FIG. Figure 2 (a), representing the (b), (c), respectively signals S ₁ is, S _2, S _3. 1D shows a time-axis multiplexed signal obtained by the apparatus of FIG. 1, and FIG. 1E shows its time axis. The time-axis multiplexed signal is composed of a cycle T (= t ₈ −t ₀ ), but since the input signals S ₁ , S ₂ , and S ₃ are continuous, it is considered that it is divided by the cycle T and S Let's say ₁₀ , S ₁₁ ,, S ₁₂ , .... t ₀ to t ₇
The signals S ₁₁ , S ₂₁ , and S ₃₁ input up to are RAM 4, 5, and 6, respectively.
Signal S ₁₁ between t ₁₀ and t ₁₁ , signal S ₂₁ between t ₁₂ and t ₁₃ , and signal S ₃₁ between t ₁₄ and t ₁₅
In between, the data is read at a shorter time interval than the time of writing. After a certain series of data is read out, until the next data is read out, a fixed time interval (t ₄ −t ₃ , t ₆ −t ₅ ,
t ₁₂ −t ₁₁ , t ₁₄ −t ₁₃ ) and switch 11
Is connected to the contact 112, and the data from the read-only memory ROM 10 is output. In addition, synchronization signals (t _{0 to} t ₁ , t _{8 to} t ₉ )
The waveforms before and after the waveform are also formed by the data output from the ROM 10. The waveform that connects between each of these signals is
It can be changed by changing the read address of ROM.

When the signals S ₁ , S ₂ , and S ₃ are time-axis multiplexed, the signals are divided every period T, and the data at the two ends of each divided signal is stored in the ROM address generation circuit 8. The ROM address generating circuit receives the input and outputs an address for selecting the waveform data used for connecting the above signals. The waveform for connecting the signals thus obtained is set in advance so that the level difference between the signals is connected by a smooth curve as shown in FIG.

It is assumed that these series of operations are performed at a predetermined time for the clock, the clock generated in the control signal generating circuit 9 and the control signal generated from the clock.

The time-axis-multiplexed digital signal obtained at the output terminal of the changeover switch 11 in the above process becomes an analog signal at the D / A converter 12, and is output from the output terminal 16.

As the connection waveform data to be written in the ROM 12 in advance, it is preferable to use data obtained by sampling a curve of a window function such as a Hamming window, a Hanning window, a Blackman window, and a Kaiser window used in digital signal processing. You can expect results.

Although the number of types of signals to be multiplexed is three in the above embodiment, the number of types of signals may be any number.

Further, the form of the time-axis multiplexed signal is not limited to the form shown in FIG. 2, and can be applied to other forms of the time-axis multiplexed signal.

〔The invention's effect〕

As described above, according to the time base multiplexing apparatus of the present invention, when the signals from a plurality of signal sources are time base multiplexed, the levels of the terminal end and the start end of each time base multiplexed signal are detected,
Hold and generate a smooth signal-to-signal connection waveform based on this detected level, and generate a smooth signal-to-signal connection waveform that connects the end points of each signal so that the start and end points of each signal are connected. So, even if the bandwidth is limited in the process of transmission,
There is an effect that almost no waveform distortion such as ringing that occurs near the joint between signals can be seen.

[Brief description of drawings]

FIG. 1 is a block diagram showing a time axis multiplexing apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a process of time axis multiplexing by the apparatus of FIG. 1, and FIGS. ) And (c) are diagrams showing signals to be time-axis multiplexed, FIG. 2 (d) is a diagram showing time-axis multiplexed signals, and FIG. 2 (e) is shown in FIGS.
It is a figure which shows the time-axis of (d). FIG. 3 is an enlarged view of the vicinity of the joint of the time-axis multiplexed signal obtained by the apparatus of FIG. 1, and FIG. 4 is a view showing a conventional time-axis multiplexed signal. ) Is a diagram showing an example of the configuration of the signal,
FIG. 4 (b) is a diagram showing the time axis. FIG. 5 is an enlarged view of the spliced portion of the signal of FIG. In the figure, 1 to 3 are A / D converters, 4 to 6 are RAMs, 7 is digital, 8 is a ROM address generation circuit, 9 is a clock,
Control signal generation circuit, 10 ROM, 11 changeover switch, 12 D
An / A converter, 20 is an end-to-end level detection holding means, and 30 is a signal connection means.

Claims (2)

[Claims] 1. A time division multiplexing apparatus for transmitting signals from a plurality of signal sources in a time division manner through the same transmission path, wherein each signal to be time-axis multiplexed has a terminal end of a preceding signal on the time axis. An end-to-end level detecting and holding means for detecting and holding the level and the level of the following end of the signal, and a smooth inter-signal connection waveform is generated based on the signal levels of the end and the start, and the preceding signal is generated by the waveform. And an inter-signal connecting means for connecting the end of the signal and the start of the next succeeding signal. 2. A waveform having the same shape as a part of a window function of any one of a Hanning window, a Hamming window, a Blackman window and a Kaiser window used in digital signal processing is used as the signal connection waveform. The time axis multiplexing device according to claim 1.