Analog (kỹ THUẬT TRUYỀN số LIỆU SLIDE)

Analog Transmission Outline  Aspects of Digital-to-Analog Conversion  Amplitude Shift Keying  Frequency Shift Keying  Phase Shift Keying  Quadrature Amplitude Modulation Digital-to-Analog Conversion  Required to send digital data over a band-pass channel  Also known as modulation (band-pass channel) Carrier Signals  Carrier signal is a high-frequency signal acting as a base for information signal  Also known as "Carrier Frequency" Sine Waves Revisited signal strength period T = 1/f peak amplitude time  General form: x(t) = A×sin(2πft + φ) phase / phase shift Conversion Techniques Bit Rate vs Baud Rate  Bit rate → the number of bits per second  Baud rate → the number of signal elements per second  In the analog transmission of digital data, the baud rate is less than or equal to the bit rate Example 5.2 An analog signal has a bit rate of 8000 bps and a baud rate of 1000 baud How many data elements are carried by each signal element? How many different signal elements we need? Solution In this example, S = 1000, N = 8000, and r and L are unknown We find first the value of r and then the value of L Binary Amplitude Shift Keying  Or Binary ASK  Simplest form → On-Off Keying (OOK) fc – Carrier frequency