Digital Modulation The discontinuity between analog and digital

Digital Modulation The discontinuity between analog and digital modulation is that in analog modulation, there are theoretically an infinite number of possible states for the carrier/channel; in digital modulation, there is a finite number of states (symbols) for the carrier/channel, and we can design the set of states to optimize decision accuracy at the receiver.

Phase Shift Keying (PSK) Bit 1 0 Oscillator 180 o 90 o 180 o 01 10 1 0 00 11 Bit 0 BPSK 0 QPSK 1 1

Phase Shift Keying (PSK) 0 Oscillator 180 o 01 11 QPSK + 180 o 00 1 + 0 90 o 10 Bit 1 1 Bit 0

Differential Binary Phase Shift Keying (DBPSK) e. g. , A zero causes a 180 degree phase change, a one causes no phase change. p 0 1 0 0 0 1 1 0 Mixer Rx Data LPF To Phase Modulator delay Data

Carrier Recovery BPSK @ f. IF BP @ f. IF X 2 BPF @ 2 f. IF PD Loop Filter X 2 VCO PD LPF Data

Quiz A 3 k. Hz BW analog signal of 5 v p-p is quantized a resolution of DQ = 0. 020 volts. What is the transmitted bit rate (+/- 5%)?

Differential QPSK 10 00 01 11 Phase Reference: Previous Carrier Phase

Quadrature Demodulation Q-bit QPSK Carrier Recovery (x 4) 10 00 11 01 90 o LPF Q-data I-bit

Bit Clock Recovery T I or Q Data RZ Signal Narrowband PLL: fc = 1/T T/2 Delay Recovered Bit Clock

Other Quadrature Modulations 8 -QAM 16 -QAM 8 -PSK (8 Phase) 8 -QAM (4