Common coding for baseband transmission

AMI encoding

1 yards is usually called the pass number, 0 yards is called the empty number, this is used in the early telegraph communication in the name. From the morphological perspective, it is a three-state signal, so the AMI code is a pseudo-three-in-one code.

First, the coding rules:

0 in the 0 transmission code in the message code
+ 1,-1 alternating in the 1 transmission code in the message code
For example:

Message Code:	1	0	1	0	1	0	0	0	1	0	1	1	1
AMI Code:	+1	0	-1	0	+1	0	0	0	-1	0	+1	-1	+1

Second, the characteristics of AMI code:

1 The base band signal determined by AMI code is alternating between positive and negative pulses, while the 0 potential remains unchanged, so the baseband signal determined by AMI code has no DC component and only a small low frequency component;
2 at the receiving end is not easy to extract timing signal, because it may appear long even 0 strings;
3 has the ability to detect errors, if in the entire transmission process, because the transmission number polarity alternating law is damaged and error, it is easy to find the fault at the receiving end.

H d b 3 Span style= "Display:inline-block; width:0px; Height:2.198em; " > Code one, coding rules:

• (1) Transform the message code into AMI code;
• (2) Check the AMI code for connection 0, when there are no 4 or more than 4 connected 0 strings, the form of the AMI remains the same, and if 4 or 4 or more 0 strings are present, the 4th 1 after 0 becomes the symbol of the same polarity as the previous non-O-code (+1 or 1), denoted by V (+n is +v,-n-V);

• (3) Check the adjacent v code between the number of non-0 yards is even, if it is even, then the current v Code of the previous non 0 yards after the 1th 0 into +b or-B code, and the polarity of B and the previous non-O-code polarity opposite, and so that the subsequent non-0 yards from the beginning of the alternating change.

  The process of converting NRZ code to HDB3 code is shown in the following table:
  　　

Second, the characteristics of HDB3 code

(1) The baseband signal determined by HDB3 code has no DC component, and only a very small low frequency component;
(2) The number of 0 strings in HDB3 is up to 3, so it is easy to extract timing signals.
(3) Coding rules are complex, but decoding is simpler.

Miller Code

Miller code, also known as the delay modulation code, it can be regarded as a two-phase code deformation.

First, the coding rules:

1 in the message code is denoted by 10 or 01;
In the message code, there are 0 of two cases:
The single "0" does not appear level hopping in the code element duration, and does not jump at the boundary of the adjacent code element;
Even the "0" string has a level jump at the boundary of two "0" yards, alternating between "00" and "11".

For example:

Second, the characteristics of Miller code:

1 The baseband signal determined by the Miller Code has no DC component;
2 in Miller code, the maximum width of the waveform appears, this property can be used for error detection;

CMI Code

The CMI code is also called the transmission number reversal code.

First, the coding rules:

1 in the message code is represented alternately by 11 or 00;
0 in the message code is represented by 01.
For example:

Code:	0	1	1	0	0	1	0	1
Dual-Phase code:	01	11	00	01	01	11	01	00

As shown in the waveform diagram:

　　

Second, the characteristics of CMI code:

There are a lot of level transitions in the CMI pattern, so it contains rich timing information.

Common coding for baseband transmission