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Signal Characteristics

Signal Characteristics. Chapter 2. Signal Characteristics . Analog (continuous) or digital (discrete) Periodic or aperiodic Components of a periodic electromagnet wave signal Amplitude (maximum signal strength) – e.g., in V

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Signal Characteristics

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  1. Signal Characteristics Chapter 2

  2. Signal Characteristics • Analog (continuous) or digital (discrete) • Periodic or aperiodic • Components of a periodic electromagnet wave signal • Amplitude (maximum signal strength) – e.g., in V • Frequency (rate at which the a periodic signal repeats itself) – expressed in Hz • Phase (measure of relative position in time within a single period) – in deg or radian (2p = 360 = 1 period)

  3. Sine Waves

  4. Sound Wave Examples Each signal is represented by x(t) = sin (2pf.t) f = 5Kz f = 1Kz A dual tone signal with f1 and f2 is represented by x(t) = sin (2pf1.t) + sin (2pf2.t)

  5. The simplest signal is a sinusoidal wave A sine wave can be expressed in time or space (wavelength) Wavelength is the distance the signal travels over a single cycle Wavelength is a function of speed and depends on the medium (signal velocity) Periodic Signal Characteristics lf=v Exact speed light through vacuum is 299,792,458 m/s

  6. Periodic Signal Characteristics • A signal can be made of many frequencies • All frequencies are multiple integer of the fundamentalfrequency • Spectrum of a signal identifies the range of frequencies the signal contains • Absolute bandwidth is defined as: Highest_Freq – Lowest_Freq • Bandwidth in general is defined as the frequency ranges where a signal has its most of energies • Signal data rate • Information carrying capacity of a signal • Expressed in bits per second (bps) • Typically, the larger frequency larger  data rate Example 

  7. Periodic Signal Characteristics • Consider the following signal • Consists of two freq. component (f) and (3f) with BW = 2f BW f 3f http://www.jhu.edu/~signals/listen-new/listen-newindex.htm

  8. Example: What is f1? What is f2? Which case has larger data rate? (sending more bits per unit of time) Data Rate & Frequency • f1 = 2(1/10^-3)=2KHz • f2 = 1 KHz • Case 1 has higher data rate (bps)

  9. Learn the Exponential Notations • 320,000 becomes 3.2 X 105 • 425,050,000 becomes 4.2505 X 108 • 0.0000045 becomes 4.5 X 10-6 • 0.0000306 becomes 3.06 X 10-5

  10. Colors and Wavelengths lf=v ColorRedOrangeYellowGreenBlueViolet Wavelength (nm)780 - 622 622 - 597597 - 577577 - 492492 - 455455 - 390 Frequency (THz)384 - 482482 - 503503 - 520520 - 610610 - 659659 - 769 1 terahertz (THz) = 10^3 GHz = 10^6 MHz = 10^12 Hz,  1 nm = 10^-3 um = 10^-6 mm = 10^-9 m. The white  light is a mixture of the colors of the visible spectra. Wavelengths is a common way of describing light waves.  Wavelength = Speed of light in vacuum / Frequency.

  11. Colors and Wavelengths

  12. Colors and Wavelengths

  13. Dialing Mechanisms • Touchtone dial pads • Introduced in 1972 • Uses the dual-tone multi-frequency – DTMF – system • Each number is represented by two specific frequencies • Much faster than rotary pulses http://www.mediacollege.com/audio/tone/dtmf.html

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