Quadrature 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).

Also known as quaternary or quadriphase PSK or 4-PSK, QPSK is one of the PSK techniques which uses four points on the constellation diagram, equispaced around a circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER — twice the rate of BPSK. Analysis shows that this may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the data-rate of BPSK but halve the bandwidth needed.

Experiments:

1. To measure the parameters of various control signals.
   • Selected clock /data rate.
   • 8-bit NRZ (L) digital data - 256 combinations of data
   • Word pulse.
2. To measure the different signals involved in QPSK generation
   • Sinusoidal signal
     1. Amplitude 2V pp
     2. Frequency 10KHz
     3. Phase 0°, 90°, 180° and 270°
   • In phase and Quadrature components
   • Output of BPSK modulation because eventually QPSK modulator output is two BPSK modulators combined in parallel.
   • Finally QPSK modulated output.
3. To measure the different signals involved in QPSK demodulation
   • Carrier signal recovery at multipliers
   • LPF and Comparator output
   • Data recovered at Bit combiner

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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