Datasheet

AD9777
Rev. C | Page 33 of 60
e
–jωt
/2j
e
–jωt
/2j
e
–jωt
/2 e
–jωt
/2
DC
DC
COSINE
SINE
02706-057
Figure 57. Real and Imaginary Components of
Sinusoidal and Cosinusoidal Waveforms
Amplitude modulating a baseband signal with a sine or a cosine
convolves the baseband signal with the modulating carrier in
the frequency domain. Amplitude scaling of the modulated
signal reduces the positive and negative frequency images by a
factor of 2. This scaling is very important in the discussion of
the various modulation modes.
The phase relationship of the modulated signals is dependent
on whether the modulating carrier is sinusoidal or cosinusoidal,
again with respect to the reference point of the viewer.
Examples of sine and cosine modulation are given in Figure 58.
DC
SINUSOIDAL
MODULATION
COSINUSOIDAL
MODULATION
DC
Ae
–jωt
/2j
Ae
–jωt
/2j
Ae
–jωt
/2 Ae
–jωt
/2
02706-058
Figure 58. Baseband Signal, Amplitude Modulated with Sine and Cosine Carriers