06_tt2510eu01al_

7/29/2019 06_tt2510eu01al_

1/28

Baseband Transmission of Digital Signals Siemens

TT2510EU01AL_011

Contents

1 Introduction 3

2 Interface Codes 7

3 Digital Signal Regeneration 15

4 Reasons for Bit Errors 23

Baseband Transmission of DigitalSignals

7/29/2019 06_tt2510eu01al_

2/28

Siemens Baseband Transmission of Digital Signals

TT2510EU01AL_012

7/29/2019 06_tt2510eu01al_

3/28


TT2510EU01AL_013

1 Introduction

7/29/2019 06_tt2510eu01al_

4/28


TT2510EU01AL_014

Digital signal devices process the signals as purely binary information, i.e. the signallevel does not change between bits with the same logical state. For this reason,these so-called NRZ-signals (No return to zero) can only be processed together with

the corresponding clock, which enables the identification of individual bit positions.

7/29/2019 06_tt2510eu01al_

5/28


TT2510EU01AL_015

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 bit

NRZ signal

Clock

Binary information 1 1 1 0 0 0 1 0 1 1 0 0

Fig. 1 Processing of NRZ signals with the aid of separate clock

7/29/2019 06_tt2510eu01al_

6/28


TT2510EU01AL_016

This clock is not separately transmitted and thus it has to be possible to derive (i.e.regenerate) the clock from the data signal on the receiving side. It is obvious that fora NRZ code this is very complicated, if not virtually impossible. A further

disadvantage of the NRZ code is that it carries a certain amount of dc-voltage whichexcluded the signals galvanic isolation at the interface (transformer etc.). Due tothese disadvantages, various interface codes have been developed; all of whichcomply with the following requirements:

l good clock retrieval features

l no dc-component.

7/29/2019 06_tt2510eu01al_

7/28


TT2510EU01AL_017

2 Interface Codes

7/29/2019 06_tt2510eu01al_

8/28


TT2510EU01AL_018

A suitable interface code has a maximum of transitions between the different signallevels, even for the transmission of lengthy sequences of identical logical states; ithas no dc-component. The survey shows the development of individual codes (fig. 2).

RZ Code A log. 1 is represented as half-bit with a change of signals levelsfrom Low High Low.

Advantage: Clock retrieval possible also for adjacent log.1 bits.

Disadvantage: No clock information for zero sequences, dc-component.

AMI Code The state log. 1 is represented alternatively as positive or negativesignal level.

Advantage: Clock retrieval possible also for adjacent log.1 bits,no dc-component.

Disadvantage: No clock information for zero sequences.

HDB 3 Code Is derived form the AMI code? Here, four consequent zero bits arereplaced by a 1001 or 0001 combination. This is done in such a waythat the signal receiver detects the mutilation of informationalcontents and cancels it.

Advantage: Maximum clock information, no dc-component.

Disadvantage: None

This code is applied for the device interfaces from 2 Mbit/s up to 34Mbit/s (baseband transmission). The exact coding rules areenumerated in the following.

CMI Code Due to its easy generation with delay lines and simple gate functionsthe CMI code is suited especially for interfaces with high bitrates.Therefore, this code is standardized for the 140 Mbit/s device inter-faces.

A further important advantage of the interface code is the possibility it offers to detecttransmission errors by supervising the coding rules. With the HDB3 code, forexample, the receiving of four zero bits would represent the violation of a coding rule,i.e. at least one bit error must have been occurred during transmission.

The standardization of interface codes only refers to device interfaces. The codes forconductor-bound transmission paths are manufacturer-dependent and are generallyadapted to the requirements of the respective terming unit.

7/29/2019 06_tt2510eu01al_

9/28


TT2510EU01AL_019

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Digital Line Codes

Signal

Clock

NRZ

binary

RZ

binary

AMI

HDB3

CMI

Fig. 2

7/29/2019 06_tt2510eu01al_

10/28


TT2510EU01AL_0110

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

2.01.81.61.41.21.00.80.60.40.20

power

idensity

frequency/bitrate

Binary NRZ

HDB3

CMI

Fig. 3 Amplitude spectrum of various codes

Fig. 3 shows the amplitude spectrum of various interface codes. For codes without adc-component the maximum energy is within the range of a frequency whichcorresponds to half of the bitrate value. This is obvious when comparing the

definitions of frequency and bitrate respectively.

7/29/2019 06_tt2510eu01al_

11/28


TT2510EU01AL_0111

0 1 1 1 10 0 0 0

2 bit

= 1 period

Fig. 4 Bit sequences 0101....

The bit sequence represented in fig. 4 shall serve as an example. One signal periodcovers 2 bits and corresponds to the basic wave of the data signal. This wavecontains the greatest amount of energy and has a frequency which equals half of thebitrate value. This is also the frequency that is indicated by a frequency counterconnected to a source of a digital signal.

7/29/2019 06_tt2510eu01al_

12/28


TT2510EU01AL_0112

HDB3-Coding rules

(Third-Order-High-Density-Bipolar-Code)

The HDB3-code is a modified version of the AMI-code. Binary signals or AMI-codesignals may contain lengthy 0 sequences, which hinder the clock retrieval in theregenerative repeaters along digital transmission paths. The HDB3 code enables theelimination of 0 sequences with more than 3 zeros.

1. If there are more than 4 consecutive 0-signal elements, the fourth 0-signalelement shall be replaced by a V-signal element (=1-signal element. A V-signalelement causes a Violation of the AMI-rule.

2. If between the V-signal element, inserted according to the conditions specifiedabove (rule 1), and the preceding V-signal element there is an even number of

1-signal elements, then the first of four 0-signal elements shall be replaced byan A-signal element (=1-signal element). The polarity of the A-signal elementcomplies with the AMI-rule. The last of four 0-signal elements becomes again a

V-signal element (A00V). In this the A- and V-signal elements have the samepolarity.

7/29/2019 06_tt2510eu01al_

13/28


TT2510EU01AL_0113

Binary

HDB3

Binary

HDB3

0 0 1 1 1 0 0 0 0 1

V

previous V-bit

0

rule 1 appliesrule 2 does not apply

0 0 1 1 0 0 0 0 0 1

previous V-bit

0

rule 1 and 2 apply

V

V

A V

Fig. 5 Conversion of binary signals into HDB3-signals

7/29/2019 06_tt2510eu01al_

14/28


TT2510EU01AL_0114

7/29/2019 06_tt2510eu01al_

15/28


TT2510EU01AL_0115

3 Digital Signal Regeneration

7/29/2019 06_tt2510eu01al_

16/28


TT2510EU01AL_0116

The digital signal regeneration is one of the advantages of the digital transmissiontechnique. Theoretically, it enables the signals to be transmitted via an unlimiteddistance without any quality loss.

During transmission, a digital signal is attenuated and distorted; which results in areduction of the signal /noise ratio. The regeneration process has the task ofcanceling such distortions and regenerating the originally sent signal from theactually received signal. That is why every interface on the receiving side is followedby a regenerator.

7/29/2019 06_tt2510eu01al_

17/28


TT2510EU01AL_0117

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TX REG+

attenuation +

interference

signal source transmission path regenerator

regenerated

signal

regenerated

signal

received

signal

transmitted

signal

Fig. 6 Principle of digital signal regeneration

7/29/2019 06_tt2510eu01al_

18/28


TT2510EU01AL_0118

Four basic function blocks are necessary for the digital signal regeneration:

lAmplification block (balancing of attenuation losses)

l

Clock retrieval blocklAmplitude decision block

l Time decision block.

7/29/2019 06_tt2510eu01al_

19/28


TT2510EU01AL_0119

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AGC AD TD regener.

data signalReceived

signal

distorted

and

attentuated

PLL

CR

regenerated

clock

AGC : Automatic gain controlled amplifierAD : Amplitude decisionTD : Time decisionCR : Clock retrieval

Fig. 7 Block diagram of a digital signal regenerator

7/29/2019 06_tt2510eu01al_

20/28


TT2510EU01AL_0120

These four functions are represented in next figure.

l The receiving signal is fed into a controlled amplifier (AGC) which keeps theamplitude of the outgoing signal at a constant value over a wide range of incoming

amplitudes. Thus, the attenuation of the transmission path is balanced.

l The constant output level is a precondition for the functioning of the amplitudedecision block (AD) which follows. This AD decides on the basis of an internalthreshold value whether the level of incoming signal is above or below thisthreshold. Accordingly, a signal with the level Log. 1 or Log.0 is emitted at theoutput. The output signal thus consists of pulses, the width of which only dependson the period during which the output signal exceeds the decision threshold.

l The time decision block (TD) has the task of generating signal pulses withconstant width. For this, it requires the regenerated receive signal clock whichsamples the output signal of the amplitude decision block. If, at the time ofsampling the signal has a level of Log. 1, the time decision block emits a pulse

with constant width. Thus, incoming pulses of any width are turned into pulsescorresponding exactly to the bit width of the transmitted signal. The time decisionprocess is the final stage of regeneration.

l The clock retrieval CR block is in charge of regenerating the transmitted signalclock from the receive signal clock. In order to effect this function, a phase lockedloop (PLL) is employed, basically consisting of a voltage-controlled oscillator

whose frequency can be changed by a control-voltage.

By adequate evaluation of the receiving signal it is now possible to reach a controlvoltage which can set the oscillator to the exact clock frequency value of thetransmitting signal.

The following examples show a regenerator for HDB3 signals, as well as the signalshape between individual function blocks.

7/29/2019 06_tt2510eu01al_

21/28


TT2510EU01AL_0121

1

2

3

4

5

6

7

8

receiving signal

after

amplification

after amplitude

decision

retrieved clock

after time

decision

after addition

PLL

12

3

4

5

6

7

8

Fig. 8 Regeneration of HDB3 signals

7/29/2019 06_tt2510eu01al_

22/28


TT2510EU01AL_0122

7/29/2019 06_tt2510eu01al_

23/28


TT2510EU01AL_0123

4 Reasons for Bit Errors

7/29/2019 06_tt2510eu01al_

24/28


TT2510EU01AL_0124

The decisive quality criterium for the transmission of digital signals is the so-called biterror rate (BER). This BER represents the proportion of bits which have beenmutilated (i.e. incorrectly recorded) during transmission, to the total amount of bits

transmitted within a certain interval. The BER directly influences the quality of thetransmitted services (e.g. voice channels, data channels, video signals). Twosignificant BER are explained exemplary in the following:

l BER = 10-6

This BER virtually cannot be perceived in a voice channel. For the transmission ofdata channels, however, this value represents the maximum acceptable limit. Thetransmission system is in a state of "degraded quality", which is indicated by adegradation alarm (low priority) on the devices involved. The transmission pathremains, nevertheless, in operation.

l BER = 10-3

This BER causes a strong interference noise in a voice channel. The operatingstate is judged to be of "unacceptable quality", which is signaled by the devicesinvolved by the emission of a failure alarm (high priority). The transmission pathgoes out of operation.

How do bit errors arise?

In the previous section it was mentioned that digital signals can be regenerated asrequested, i.e. a transmission without quality reduction is possible. This statement is,

however, only partially true, i.e. whenever the impairment of the transmission signalsis within limits which still permit the regeneration at the receiving side. The reasonsfor the formation of bit errors are

l low signal/noise ration

ljitter

l intersymbol interference

Low signal/noise ratio

Noise amplitudes which influence the amplitude decision process are superimposed

to the originally sent signal.

The superimposed interference peaks lead to an incorrect signal interpretation at thereceiving end. Reasons for a low S/N-ratio are:

3. too strong signal attenuation during transmission

4. external interference during transmission.

For transmission in cable sections (especially optical fiber) both reasons can belargely eliminated by careful planning.

7/29/2019 06_tt2510eu01al_

25/28


TT2510EU01AL_0125

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Decision treshold

Fig. 9 Low S/N-ratio

7/29/2019 06_tt2510eu01al_

26/28


TT2510EU01AL_0126

Jitter

Due to jitter, the transitions between signal levels log. 0 and log. 1 do not take place

at periodically recurring points in time (characteristically moments) as for undisturbedsignals, which means that the transitions oscillate around the characteristicallymoments.

Jitter is characterized by jitter amplitude (unit intervals UI) and jitter frequency.

One UI means that, because of deviation from the characteristically moments, thesignal edges are within a range equal to the width of 1 bit.

The jitter frequency is the number of oscillations around the characteristically momentper one second. Jitter influences the time decision process in the regenerator andcauses bit errors for high jitter amplitudes and frequency.

Jitter arises in the devices used for signal transmission. (I.e. in regenerators anddemultiplexers = systematical jitter), or on the transmission path due to externalinfluences (non-systematic jitter).

7/29/2019 06_tt2510eu01al_

27/28


TT2510EU01AL_0127

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

signal without jitter

premature occurence of signal

edge (+T/2)

late occurence of signal

edge (-T/2)characteristical

moment

T

T

Fig. 10 Representation of an Unit Interval (UI)

7/29/2019 06_tt2510eu01al_

28/28


Intersymbol interference.

Is caused by a discrepancy between the bandwidth of the transmission path and the

bandwidth required for the digital signal. This leads to a bit extension, so that there isan overlap of bits which follow each other. Thus, bit errors occur, the reasons of

which can be traced back to the impairment of amplitude decision process. Forconductor-bound transmission of digital signals this effect can be excluded byadequate planning. For transmission on radio paths this effect is of fundamentalimportance as the frequency response of the transmission path can change due toatmospherically influence.

Documents

06_tt2510eu01al_