Differential Phase Shift Keying

Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave).

Any digital modulation scheme uses a finite number of distinct signals to represent digital data. In the case of PSK, a finite number of phases are used. Each of these phases is assigned a unique pattern of binary bits. Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data. This requires the receiver to be able to compare the phase of the received signal to a reference signal — such a system is termed coherent.

Alternatively, instead of using the bit patterns to set the phase of the wave, it can instead be used to change it by a specified amount. The demodulator then determines the changes in the phase of the received signal rather than the phase itself. Since this scheme depends on the difference between successive phases, it is termed differential phase-shift keying (DPSK).

Experiments:

1. To measure the parameters of various control signals.
   • Selected clock /data rate.
   • 8bit digital data of NRZ pattern - 256 combinations of data
   • Word pulse.
2. To measure the different signals involved in ASK generation and to measure the different signals involved in DPSK generation
   • Sinusoidal signal
     1. Amplitude 2V pp
     2. Frequency 10KHz
     3. Phase 0° and 180°
   • DPSK modulated output
3. To measure the characteristics of DPSK demodulator block
   • Multiplier and LPF output
   • DPSK demodulated output
   • Final demodulated output

Technical Specification:

FEATURES:

• All IC's are mounted on machined IC base.
• PCB's are SMOBC finished with glass epoxy coating.
• Multi color printed block diagram is given on the top of the kit.
• Testing point at the end of each functional block.
• 2⁸ or 256 data pattern combinations available through dip switches.
• The trainer kit is enclosed in fiber glass box for safe keep

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