帧同步提取系统实验

1. Purpose  Understand the mechanism of frame synchronization

 To familiar with the performance of frame synchronization  To familiar with LOF impact on data services

2. Theory If the interruption time of speech signal is shorter than 100ms, will not easily distinguishable by the human ears. However, some data transmission terminal is not allowed. To ensure students to understand LOF, synchronization and error resilience in the environment of bit error, in the multiplexer module designed a wrong code generator (3 types BER),by the error code set jumper switch SWB02 (E_SEL0, E_SEL1) to select different channel bit error rate (approximately 4103、1.610-2和110-1). Students can observe that the multiplexing / de-multiplexing has anti-error performance that frame synchronization lock status when a small error, error frames-step increased, enter the frame synchronization search (scan) status; More over, you can test impact on voice services and data services by different error code and LOF.

3. Apparatus  JH5001 communication principle of a comprehensive test system  A 20MHz dual trace oscilloscope  A Function Generator

4. Procedure And Lab Results Preparation: Firstly,in multiplexing module,use the input signal and the clock

selection jumper switch KB01, KB02 set LOOP (from the ring), and make the multiplexing and de-multiplexing module which connected into self-loop test methods; Unplug the selection jumper M_SEL1, M_SEL2 of m-sequence belong to SBW02(working state selection jumper switch) which is in the multiplexing module,the m-sequence generator generated full 0 yards, unplug the wrong code selection jumper E_SEL0, E_SEL1 , not insert error code in frame transmission . 1.Frame synchronization process observed

(1)With an oscilloscope,Simultaneously observed the waveform of multiplexer module frame synchronization instructions and test point TPB07 and Demultiplexer module frame synchronization instructions test points TPB06 . TPB07 synchronization at the time of observation, adjust the scope so that the observed signal synchronization.

From the above chart we can find that the two signals of TPB07 and TPB06 looks synchronized.

(2)Unplug input data selection jumper KB01 crowbar in the Demultiplexer module,and make the transmission channel off, observe Demultiplexer module frame synchronization situation of de-synchronization . KB01 insert and unplug the crowbar repeatedly , observe synchronization and de-synchronization , record test results.

Results:

After unplugging KB01 crowbar, the waveform of TPB06 constantly moving , that means it is out of step;

After plugging KB01 crowbar, the waveform of TPB06 will stop moving until moving to synchronize, that means get to synchronization.

2.The qualitative observations of receiving frame data signal transmission under LOF

(1)Unplug the E_SEL0, E_SEL1 crowbar of the error code selection jumper SWB02 in the multiplexing module(no error code),then multiplexing /

de-multiplexing system is in a normal communication state, the switch signal indicator light-emitting diodes indicator (DB01 ~ DB08)within de-multiplexing module is consistent with the state of LED0 ~ LED8 belong to the jumper switch SWB01 in multiplexing module. Randomly change WB01's LED7 ~ LED0 crowbar, DB01 ~ DB08 indicator changes.

Results: Which LED connected of SWB01, the corresponding DB will light up. (2)Set the E_SEL0, E_SEL1 crowbar of the error code selection jumper SWB02 in different states within multiplexing module,change the transmission channel error bit rate. Qualitatively observe the change states of switch signal indicator LED lights (DB01 ~ DB08) within Demultiplexer module,record test results.

Results:

When connected E_SEL1, DB08 ~ DB01 will be light up in turn, and then all light, then darken, followed by cycle.

When connected E_SEL0, DB08 ~ DB01 has been in a dark state.