SeriousTyro
Member level 2
From this article
http://www.emc.york.ac.uk/reports/linkpcp/appD.pdf
It mentions
"If a QPSK modulated signal undergoes filtering to reduce the spectral side lobes, the
resulting waveform will no longer have a constant envelop and in fact, the occasional
180o shifts in phase will cause the envelope to go to zero momentarily."
and with OQPSK
"When an OQPSK signal undergoes bandlimiting, the resulting intersymbol interference
causes the envelop to droop slightly to the region of ± 90o phase transition, but since
the phase transitions of 180 have been avoided in OQPSK, the envelop will never go
to zero as it does in QPSK."
I understand how the QPSK signal would undergo filtering to reduce the spectral side lobs but why is the envelope becoming zero momentarily bad?
http://www.emc.york.ac.uk/reports/linkpcp/appD.pdf
It mentions
"If a QPSK modulated signal undergoes filtering to reduce the spectral side lobes, the
resulting waveform will no longer have a constant envelop and in fact, the occasional
180o shifts in phase will cause the envelope to go to zero momentarily."
and with OQPSK
"When an OQPSK signal undergoes bandlimiting, the resulting intersymbol interference
causes the envelop to droop slightly to the region of ± 90o phase transition, but since
the phase transitions of 180 have been avoided in OQPSK, the envelop will never go
to zero as it does in QPSK."
I understand how the QPSK signal would undergo filtering to reduce the spectral side lobs but why is the envelope becoming zero momentarily bad?