Electronic Communications (Introduction - chapter 1)

Difference between highest and lowest frequencies contained in the information.

Bandwidth

The most basic digital symbol used to represent information.

Binary Digit / Bit

Its fundamental purpose is to transfer information from one place to another.

Electronic Communication System

The transmission, reception, and processing of information between two or more locations using electronic circuits.

Electronic Communication

Are time-varying voltages or currents that are continuously changing such as sine and cosine waves.

analog signals

Is sometimes referred to as a power loss.

Attenuation

Is sometimes referred to as a ______________, If Pout = Pin, the absolute power gain is 1, and the dB power gain is 0 dB.

Unity Power Gain

Are voltages or currents that change in discrete levels.

Digital Signals

A convenient parameter often used rather than noise figure in low noise, sophisticated VHF, UHF, microwave, and satellite radio receivers. It indicates the reduction in the signal-to-noise ratio a signal undergoes as it propagates through a receiver.

Equivalent Noise Temperature ( Te )

Te = T ( F - 1 )

NF ( dB ) = 10 log F

Formula for Noise Figure

F = Input/output

Formula for Noise Factor

Figures of merit used to indicate how much the signal- to-noise ratio deteriorates as a signal passes through a circuit or series of circuits

Noise Factor ( F ) and Noise Figure ( NF )

The ratio of the signal power level to the noise power level.

Signal-to-Noise Power Ratio ( S/N )

Noise produced when information signals from one source produce frequencies that fall outside their allocated bandwidth and interfere with information signals from another source.

Electrical interference

A form of external noise and as the name implies it means to disturb or detract form.

Interference

Characterized by high-amplitude peaks of short duration in the total noise spectrum.

Impulse Noise

Another name for harmonic distortion.

Amplitude Distortion

A frequency three times the original signal frequency.

Third Harmonic

A frequency two times the original signal frequency.

Second Harmonic

The original signal and also called the fundamental frequency

First Harmonic

The generation of unwanted sum and difference frequencies produced when two or more signals mix in a nonlinear device.

Inter-modulation Distortion

Occurs when unwanted harmonics of a signal are produced through nonlinear amplification (nonlinear mixing).

Harmonic Distortion

Correlated Noise

A form of internal noise that is correlated (mutually related) to the signal and cannot be present in a circuit unless there is a signal. " no signal, no noise! "

Johnson proved that thermal noise power is proportional to the product of bandwidth and temperature.

Noise Power

N = KTB

Thermal Noise, because it is temperature dependent; Brownian Noise, after its discoverer; Johnson Noise, after the man who related Brownian particle movement of electron movement; White Noise, because the random movement is at all frequencies;

THERMAL AGITATION HAS SEVERAL NAMES, INCLUDING :

Associated with the rapid and random movement of electrons within a conductor due to thermal agitation.

Thermal Noise

Any modification to a stream of carriers as they pass from the input to the output of a device produces an irregular, random variations.

Transit-time Noise

Noise caused by the random arrival of carriers (holes and electrons) at the output element of an electronic device.

Shot Noise

Electrical interference generated within a device or circuit.

Internal Noise

Noise that is produced by mankind.

Man-made noise

Noise sources that are continuously distributed throughout the galaxies.

Cosmic Noise

Noise generated directly from the sun's heat.

Solar Noise

Extraterrestrial noise is sometimes called ____________ .

Deep-Space Noise

Noise consists of electrical signals that originate from outside Earth's atmosphere and is sometimes called deep-space noise.

Extraterrestrial Noise

Atmospheric noise is commonly called ____________ .

Static Electricity

Noise that is naturally occurring electrical disturbances that originate within Earth's atmosphere.

Atmospheric Noise

Noise that is generated outside the device or circuit.

External Noise

Noise present regardless of whether there is a signal present or not.

Uncorrelated Noise

Any undesirable electrical energy that falls within the passband of the signal.

Electrical Noise

In 1948, mathematician Claude E. Shannon published a paper in the Bell System Technical Journal relating the information capacity of a communications channel to bandwidth and signal-to-noise ratio.

Shannon limit for information capacity I = Blog2 (1+S/N) or I = 3.32Blog2(1+S/N)

In 1928, R. Hartley of Bell Telephone Laboratories developed a useful relationship among bandwidth, transmission time, and information capacity.

Hartley's Law

I B x t

The number of bits transmitted during one second and is expressed in bits per second (bps).

Bit Rate

The measure of how much information can be propagated through a communications system and is a function of bandwidth and transmission time.

Information Capacity

A highly theoretical study of the efficient use of bandwidth to propagate information through electronic communications systems.

Information Theory

The bandwidth of a communications channel is the difference between the highest and lowest frequencies that the channel will allow to pass through it.

Passband

The two most significant limitations on the performance of a communications system are ________and ________.

Noise and Bandwidth

Radio transmitter classifications according to bandwidth, modulation scheme, and type of information.

Emission Classifications

The length that one cycle of an electromagnetic wave occupies in space (i.e., the distance between similar points in a repetitive wave).

Wavelength

Used for optical fiber systems.

Light-wave Communications

Includes electromagnetic frequencies that fall within the visible range of humans (0.3PHz to 3PHz).

Visible Light

Are signals in the 0.3THz to 300THz range and are not generally referred to as radio waves. Used in heat seeking guidance systems, electronic photography, and astronomy

Infrared

In the United States, assigns frequencies and communications services for free-space radio propagation.

Federal Communications Commission ( FCC )

Is an international agency in control of allocating frequencies and services within the overall frequency spectrum.

International Telecommunications Union ( ITU )

Each complete alternation of the waveform.

Cycle

The number of times a periodic motion, such as a sine wave of voltage or current, occurs in a given period of time.

Frequency

The purpose of an electronic communications system is to communicate information between two or more locations commonly called _____________ .

Stations

Process of converting a frequency or band of frequencies to another location in the total frequency spectrum.

Frequency Translation

A specific band of frequencies allocated a particular service.

Channel

1. It is extremely difficult to radiate low-frequency signals from an antenna in the form of electromagnetic energy. 2. Information signals often occupy the same frequency band and, if signals from two or more sources are transmitted at the same time, they would interfere with each other.

2 Reasons why modulation is necessary in electronic communications :

Demodulation is performed in a receiver by a circuit called _______.

Demodulator

The reverse process of modulation and converts the modulated carrier back to the original information.

Demodulation

Modulation is performed in a transmitter by a circuit called ________.

Modulator

A modulation technique where both the amplitude and the phase of the carrier are varied proportional to the information signal.

Quadrature Amplitude Modulation ( QAM )

A modulation technique where the information signal is digital and the phase () of the carrier is varied proportional to the information signal.

Phase Shift Keying ( PSK )

A modulation technique where the information signal is digital and the frequency (f) of the carrier is varied proportional to the information signal.

Frequency Shift Keying ( FSK )

A modulation technique where the information signal is digital and that amplitude (V) of the carrier is varied proportional to the information signal.

Amplitude Shift Keying ( ASK )

A modulation technique where the information signal is analog and the phase () of the carrier is varied proportional to the information signal.

Phase Modulation

A modulation technique where the information signal is analog and the frequency (f) of the carrier is varied proportional to the information signal.

Frequency Modulation ( FM )

A modulation technique where the information signal is analog and the amplitude (V) of the carrier is varied proportional to the information signal.

Amplitude Modulation ( AM )

The transmittal of digitally modulated analog carriers between two or more points in a communications system.

digital radio

A true digital system where digital pulses (discrete levels such as +5V and ground) are transferred between two or more points in a communications system.

Digital Transmission

A system in which energy is transmitted and received in analog form (a continuously varying signals such as a sine wave).

Analog Communication System

The process of changing one or more properties of the analog carrier in proportion with the information signal.

Modulation

Because it is often impractical to propagate information signals over standard transmission media, it is often necessary to modulate the source information onto a higher-frequency analog signal called a ______.

Carrier

Is any unwanted electrical signals that interfere with the information signal.

System Noise

A collection of electronic devices and circuits that accepts the transmitted signals fro the transmission medium and then converts those signals back to their original form.

Receiver

Provides a means of transporting signals between a transmitter and a receiver.

Transmission Medium

A collection of one or more electronic devices or circuits that converts the original source information to a form more suitable for transmission over a particular transmission medium.

Transmitter

One-tenth of a decibel.

Bel

Is a unit of measurement used to indicate the ratio of a power level with respect to a fixed reference level (1mW).

dBm

Is a logarithmic unit that can be used to measure ratio.

Decibel ( dB )

In 1876, Alexander Graham Bell and Thomas A. Watson were the first to successfully transfer human conversation over a crude metallic- wire communications systems using this device.

Telephone

To be transmitted, data must be transformed to ___________________.

electromagnetic signals

refers to information that is continuous. Human voice

Analog data

refers to information that has discrete states. Data stored in the computer memory in the form of 1s and 0s

Digital data

has infinitely many levels of intensity over a period of time. As the wave moves from value A to value B, it passes through and includes an infinite number of values along its path.

analog signal

can have only a limited number of defined values. Although each value can be any number, it is often as simple as 1 and O.

digital signal

In digital and data communications, we commonly use ____________________ and _________________.

periodic analog signals-non-periodic digital signals.

can be classified as simple or composite

Periodic analog signals

a sine wave, cannot be decomposed into simpler signals

Simple periodic analog signal

is composed of multiple sine waves.

Composite periodic analog signal

d refers to the amount of time, in seconds, a signal needs to complete 1 cycle

Period

refers to the number of periods in I s

Frequency

If a signal does not change at all, its frequency is _____. If a signal changes instantaneously, its frequency is _____.

zero-infinite.

describes the position of the waveform relative to time 0

Phase

According to Fourier analysis, any composite signal is a combination of _____________ with different frequencies, amplitudes, and phases.

simple sine waves

If the composite signal, the decomposition gives a series of signals with discrete frequencies

periodic

If the composite signal, the decomposition gives a combination of sine waves with continuous frequencies.

nonperiodic

Signals travel through transmission media, which are not perfect. This means that the signal at the beginning of the medium is not the same as the signal at the end of the medium. What is sent is not what is received.

TRANSMISSION IMPAIRMENT

Three causes of impairment are:

attenuation, distortion, and noise