Forouzan's Introduction to Physical Layer

Data can be ______ and ______

digital, analog

Both analog and digital signals can take one or two forms, which are

periodic and non-periodic (aperiodic)

A _______ completes a pattern within a measurable time frame, called a _________

periodic signal, period

A _________ signal changes without exhibiting a pattern or cycle that repeats over time

non-periodic

The ________ is the most fundamental form of a periodic analog signal

sine wave

A sine wave can be represented by three parameters. Name them.

• peak amplitude

• frequency

• phase

For electric signals, peak amplitude is normally measured in ______

volts

Period refers to the amount of ________ a signal needs to complete _______

time (in seconds), 1 cycle

Frequency is measured in ____

Hertz (Hz)

A ms is equal to

10^-3 s

What’s the phase of a sine wave?

The term phase, or phase shift, describes the position of the waveform relative to time 0.

Phase is measured in _____ or ______

degrees, radians

The wavelength is normally measured in _______

micrometers (microns)

What’s bandwidth?

Bandwidth is the range of frequencies contained in a composite signal. It’s the difference between the highest and the lowest frequencies contained in that signal. B = f2 - f1

True or false: A digital signal can have more than two levels

True, a digital signal can have more than two levels

If a signal has L levels, each level needs ______ bits

log₂L

The bit rate is _________

the number of bits sent in one second

The bit rate is expressed in ______

bits per second (bps)

The bit length is

the distance one bit occupies on the transmission medium

[Formula] bit length =

propagation speed x bit duration

A digital signal is _________

a composite analog signal with an infinite bandwidth

Baseband transmission requires that we have a _____

low pass channel

Attenuation means

a loss of energy

To show that a signal has lost or gained strength, engineers use the unit of the ________.

decibel (dB)

The decibel measures __________

the relative strengths of two signal or one signal at two different points

A decibel is negative if a signal is ______

attenuated

A decibel is _________ if a signal is amplified

positive

How can we find the dB given the powers of a signal ?

We do dB = 10log₁₀(P₂/P₁)

How can we find the dB given the voltages of a signal ?

We do dB = 20log₁₀(V₂/V₁)

Distortion means that the signal changes its _____

form or shape

Name the types of noise

• Thermal noise

• Induced noise

• Crosstalk

• Impulse noise