Operating Manual Vol 1 - ES Documentation

Digital ModulationSMIQFor offset QPSK (OQPSK), the Q signal is delayed by half the symbol period with reference to the Isignal.QAM modulation methods 16QAM, 32QAM, 64QAM and 256QAM were implemented according to ETSIstandard ETS 300429 for Digital Video Broadcasting (DVB).All PSK and QAM modulation methods can be combined with COS and SQR_COS baseband filters aswell as with IS-95 filters. A combination with GAUSS and BESSEL filters is not possible.2.10.1.2 Modulation π/4DQPSKWith differential coding switched on at the same time, a constellation diagram is obtained for π/4DQPSKwhich is similar to that obtained for 8PSK. Phase shifts are however assigned to the individualmodulation symbols. The following tables show the assignment of modulation symbols to phase shifts ofIQ vectors at the selected coding.Table 2-4Phase shifts for π/4DQPSK without codingModulation symbol d n(binary indication: MSB, LSB)00 01 10 11Phase shift ϕ+ 45° +135° -135° -45°Table 2-5Phase shifts for π/4DQPSK with coding NADC, PDC, PHS, TETRA or APCO25Modulation symbol d n(binary display: MSB, LSB)00 01 10 11Phase shift ϕ+ 45° +135° -45° -135°Table 2-6Phase shifts for π/4DQPSK with coding TFTSModulation symbol d n(binary display: MSB, LSB)00 01 10 11Phase shift ϕ- 135° +135° -45° +45°1125.5555.03 2.88E-9