6. Generation and Detection of DPSK Aim: To study the various steps involved in generating the differential binary sign signal al and and diffe differen renti tial al phas phase e shif shiftt eye eyed d sign signal al at the the modu modula lator tor and and recovering the binary signal from the received DPSK signal. Apparatus: !athode ray oscilloscope" Probes" Patch chords Theory: Digital communication become important #ith the e$pansion of the use of computers and data processing "and have continued to develop into a ma%or industry providing the interconnection of the computer peripherals and transmission of data bet#een distant sites. Phase shift eying is a relatively ne# system" in #hich the carrier may be phase shifted by &'( degrees for mar" and by )'( degrees for space. PSK has a number of similarities to *SK in many aspects+ fre,uency of the carrier is shifted in accordance #ith the modulating s,uare #ave. *ig)- sho#s the circuit diagram of differential phase shift ey modulation and de modulation .n this ! /(0/ is a basic #ave form generator #hich generates sine" s,uare" triangle #aveforms. The sine #ave generated by /(0/ ! is used as a carrier signal to the system. The s,uare #ave generated by /(0/! is 123 -45 level. so this is converted into a 15 signal #ith the help of a transistor and diodes as sho#n in fig -.this s,uare #ave is used as a cloc input to a decade counter #hich generates the modulating data outputs. The differential signal to the modulating signal is generated using an 7$clusive)89 gate and a -)bit delay circuit. !D (- is an analog multiple$er to #hich carrier is applied #ith and #ith out -/( degrees phase shift;created by using an operational amplifier connected in inverting mode
Procedure: -. S#itch on the e$perimental board. 4. !hec the carrier signal and the data generator signals initially. 0. Apply the carrier signal to the carrier input of the DPSK modulator and give the data generator to the data input of DPSK modulator and bit cloc output to the input of DPSK modulator and bit cloc o2p to bit cloc input of modulator.
. 8bserve the DPSK modulating output #ith respect to the input data generated signal of dual trace oscilloscope" and observe the DPSK signal #ith respect to differential data also.
. Give the output of the DPSK modulator signal to the input of the demodulator" give the bit cloc output to the bit cloc input to the demodulator and also give the carrier output to the carrier input of demodulator.
6. 8bserve the demodulator output #ith respect to data generator signal. Kit Diagram:
