Outline

  1. What is signal?
  2. How to represent signal?
    1. Time/Frequency domain
  3. How to transmit/receive information carried by signals?
    1. Analog modulation: AM, FM

Materials

MIT 6.082 Intro to EECS II Fall 2006

Fourier Serioes PartI

Modulation

Princeton CLC201

Signal

  • Start to think about how human communicate with each other by speaking
    • What is the signal that delivers information? - Voice
    • How does voice represent different information? - Variation in tones
    • Similarly, wireless communication exploits the variations of electromagnetic signals to carry information.
  • A signal is a certain waveform.
    • Starting with the basic f(t) = A\cdot cos(2\pi ft + \phi)
    • A wireless device can configure A, f, \phi to send different signals.

Frequency View

  • Fourier Transformation provides a different view to look at signals

  • Any signal can be consider as a sum of sinusoids.

    • $\sum^N_{n=1} A_n \cdot sin(2\pi f_nt + \phi_n)$
    • Or \sum^N_{n=1} a_n \cdot cos(2\pi f_nt) + b_n \cdot sin(2\pi f_nt)

  • Applet to play with

    • Show phase change by varying cos and sin.
      • Click phase shift
    • Show Square

  • With different frequency f, the signal can have different properties. NASA Wiki Zoom-In View

    • High frequency, low penetration

References:

Modulation

How to carry information with different signals?