1. Periodogram of a sinusoid + spike Single high value is sum of sine curves all in phase at time t 0 :

2. Periodogram of a sinusoid + white noise White noise is sum of sine curves with equal amplitude but random phases: NOTE THAT BOTH FLAT NOISE AND A SPIKE HAVE FLAT PERIODOGRAMS

3. Amplitude modulation Suppose the amplitude of the oscillation changes sinusoidally with time: This produces sidelobes at .

4. Phase modulation Suppose the phase increases at a rate that has a sine variation superposed: This also gives sidelobes at  but with different phases relative to those produced by amplitude modulation.

5. Phase relations for sidelobes Combined amplitude & phase modulation: Frequency spectra: S(  ) C(  ) Amplitude modulation Phase modulation