93 M-ary PSK Bit Error Rate performance.
We can plot the signal constellation diagram for 16-PSK using an RC LPF with 0.3. The
diagram in Fig. 2.94 shows us the transmit waveform has envelope variations and is therefore not
a constant envelope.
16-PSK Constellation
??“3
??“2
??“1
0
1
2
3
??“4 ??“3 ??“2 ??“1 0 1 2 3 4
I-Channel
Q-Channel
FIGURE 2.94 16-PSK signal constellation using RC with 0.3.
The eye diagram of the corresponding signal constellation is given in Fig. 2.95. We can clearly see
the additional levels required to support the 16-PSK modulation waveform. Also note they are not all
equidistant from each other.
We made a point to mention noncoherent detection as a means to simply demodulate M-DPSK
modulation waveforms. The BER of M-DPSK (M2, 4, and 8) is presented in Fig. 2.96. When comparing
the BER performance of 8-DPSK to 8-PSK, we notice that noncoherent detection requires
approximately 3-dB-higher Eb/No for BER 1E-5 in an AWGN channel.
106 CHAPTER TWO
16-PSK Eye Diagram
??“3
??“2
??“1
0
1
2
3
0 4 8 12 16
Normalized Symbols (?—Ts/8)
Eye Value
FIGURE 2.95 16-PSK signal constellation using RC with 0.3.
Differential Detection of Differentially Encoded MPSK
1.
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