ESAT

BALANCED TRANSMISSION LINE

Made up of two parallel conductors spaced from one another by a distance of ½ inch up to several inches

Transmission Line

is a metallic conductor system that is used to transfer electrical energy from one point to another.

Basic Emission Classification (first symbol)

- Type of Modulation of the Main Carrier

balanced

means that same current flows in each wire with respect to ground, although the currents are 180 deg out of phase

UNBALANCED TRANSMISSION LINE

Consists of a solid center conductor surrounded by a insulator. One conductor is connected to ground.

Baluns

A circuit device used to connect a balanced transmission line to unbalanced load

OPEN-WIRE TRANSMISSION LINE

It consists simply of two parallel wires, closely spaced and separated by air.

2 inches and 6 inches.

The distance between two conductors in OPEN-WIRE TRANSMISSION LINE is generally between __________and _________

Twin Lead

is essentially the same with Open-wire transmission line except that it is separated by solid dielectric rather than air.

5/16 inch

The distance of two conductors in Twin Lead is ____________ for television transmission cable.

twisted-pair cable

formed by twisting together two insulated conductors.

- Pair
- Units
- Cores

Twisted-pair configuration:

Coaxial cables

are used extensively for high-frequency applications to reduce losses and to isolate transmission paths.

provides excellent shielding against external interference

1. Rigid Air-filled
2. Solid Flexible

Types of Coaxial Cable

Rigid-Air Filled Coaxial Cable

has a center conductor surrounded coaxially by a tubular outer conductor and the insulating material is air.

rigid coaxial lines

Some ___________ are pressurized with an inert gas to prevent moisture from entering

SOLID FLEXIBLE

Consist of a flexible inner conductor and a concentric outer conductor of metal braid. The two are separated by a continuous insulating material.

Propagation Constant

used to express the attenuation and the phase shift per unit length of a transmission line.

STRIPLINE (Flat Metallic Ground Plane)

A microwave transmission line constructed of a center conductor suspended between parallel conductive ground planes.

MICROSTRIP

Consists of the top strip and its image below the ground plane.

CONDUCTOR LOSS

The inherent and unavoidable power loss because of the finite resistance of the transmission line.

Sometimes called conductor or conductor heating loss or I2R loss.

DIELECTRIC HEATING LOSS

Loss caused by the heating of the dielectric material between conductors, taking power from the source.
Increase with frequency for solid dielectric lines because of gradually worsening properties with increasing frequency.

RADIATION LOSS

If the separation between the conductors in a transmission line is an appreciable fraction of a wavelength, the electrostatic and electromagnetic fields that surround the conductor cause the line to act as an antenna.

COUPLING LOSS

occurs whenever a connection is made to or from a transmission line or when two separated pieces of transmission line are connected together.

CORONA

a luminous discharge that occurs between the two conductors of a transmission line when the difference of potential between them exceeds the breakdown voltage of the dielectric insulator.

non-resonant

A transmission line is _______________ if it is of infinite length or if it is terminated with a resistive load equal to the ohmic value of the characteristic impedance of the transmission lines.

Resonant

In a ____________ line, the energy is alternately transferred between the magnetic and electric fields of the distributed inductance and capacitance of the line.

reflection coefficient

a vector quantity that represents the ratio of the reflected voltage to incident voltage or reflected current to incident current

Standing Wave Ratio

is defined as the ratio of the maximum voltage to the minimum voltage or the maximum current to the minimum current of a standing wave.

A measure of the mismatch between the load and the line.

Electronic Communications Systems

•It is the SENDING, PROCESSING, and RECEIVING of information by electrical or electronic means.

•The EXCHANGE of INFORMATION by electronic means.

Transmitter

•A source of information, which must be delivered or transmitted to a particular destination over a channel.

•A DEVICE that TRANSMITS INFORMATION.

•Modulators
•Frequency-up converter
•Amplifiers
•Oscillators

Transmitter Components

Receiver

The destination upon which information from the transmitter is delivered.

•The DESTINATION of INFORMATION.

Amplifiers
•Frequency-down converter
•Oscillators
•Demodulators

Receiver Components

Transmission Channel

The PATH or MEDIUM that the information travels from the transmitter to the receiver

Frequency

•It is simply the number of times a particular phenomenon occurs in a given period of time.
•The NUMBER of TIMES an event occurs in a PERIOD of TIME.

Wavelength

•The DISTANCE between TWO POINTS of similar cycles of a PERIODIC WAVE.

•The DISTANCE travelled by an electromagnetic wave during the TIME of ONE CYCLE.

Bandwidth

•It is the PORTION of the electromagnetic spectrum OCCUPIED by a SIGNAL.

•The FREQUENCY RANGE over which an information signal is transmitted or over which a receiver or other circuits operates.

• Extremely Low Frequency (ELF)
• Voice Frequency (VF)
• Very Low Frequency (VLF)
• Low Frequency (LF)
• Medium Frequency (MF)
• High Frequency (HF)
• Very High Frequency (VHF)
• Ultra High Frequency (UHF)
• Super High Frequency (SHF)
• Extremely High Frequency (EHF)
• Light

The Frequency Spectrum

Extremely Low Frequency (ELF)

30-300 Hz range
•AC Power line

Voice Frequency (VF)

•300 - 3000 Hz range
•Normal range of HUMAN SPEECH.

Very Low Frequency (VLF)

3 - 30 kHz range
•Used in some GOVERNMENT and MILITARY Communications.
•Used in NAVY to communicate with SUBMARINES.

Low Frequency (LF)

•30 - 300 kHz range
•Used as SUBCARRIERS.
•Subcarriers *SIGNALS which carry the BASEBAND modulating information but which in turn, MODULATE another higher-frequency carrier.

Medium Frequency (MF)

•300 - 3000 kHz range •Major application is the AM RADIO BROADCASTING •Also for MARINE and AERONAUTICAL Communications Applications

High Frequency (HF)

•3 - 30 MHz range
•Known as SHORT WAVES.
•Used for AMATEUR RADIO and CB Communications.

Very High Frequency (VHF)

•30 - 300 MHz range
•Used in MOBILE RADIO, FM RADIO BROADCASTING and COMMERCIAL TV BROADCASTING

Ultra High Frequency (UHF)

300 - 3000 MHz range
•Used in UHF Television
•Used in LAND MOBILE Communications and RADAR. •Also called MICROWAVES.

Super High Frequency (SHF)

•3 - 30 GHz range
•Widely used in SATELLITE Communications and RADAR.

Extremely High Frequency (EHF)

•30- 300 GHz range
•Includes Satellite Communications and SPECIALIZED RADAR.
•Referred to as MILLIMETER WAVES.

*Infrared
*Visible
*Ultraviolet

•Three Categories of Light

Infrared

•Occupies the range between 0.01 mm and 700 nm.
•Long infrared (0.01 mm to 1000 nm)
•Short Infrared (1000 nm to 700 nm)

Power and DeciBel

•It is the fundamental quantity representing the RATE at which ENERGY is used
. •It is more readily measurable since it can be converted to HEAT.
•Decibel indicates the relation between two powers

Ralph Hartley
Claude Shannon

Information Capacity

Ralph Hartley

*Developed a useful relationship among bandwidth, transmission time, and information capacity.

Claude Shannon

Published a paper relating information capacity to bandwidth and S/N ratio

Noise

•Is random, undesirable electric energy that enters the communication system via the communicating medium and interferes with the transmitted message.

•RANDOM, UNDESIRABLE ENERGY that enters the system through the MEDIUM.

Uncorrelated Noise
Correlated Noise

Categories of Noise

Uncorrelated Noise

* is PRESENT regardless of whether there is SIGNAL PRESENT or NOT

Correlated Noise

* to the SIGNAL and CANNOT BE PRESENT in CIRCUIT UNLESS there is an INPUT SIGNAL.

External Noise
•Internal Noise

Types of Uncorrelated Noise

External Noise

•Type of noise that affects the communication system coming from OUTSIDE environment.
•Atmospheric Noise
•Extraterrestrial Noise Solar Noise Cosmic Noise
•Man-made Noise

Atmospheric Noise

•Naturally occurring electrical disturbances that originates within the Earth's atmosphere
•Also called STATIC NOISE.
•It is caused by LIGHTNING discharges in thunderstorms.

Extraterrestrial Noise

•Solar Noise constant noise radiation from the sun electrical disturbance due to SOLAR CYCLE activities *repeats every 11 years

•Cosmic Noise RF NOISE radiated by DISTANT STARS. What they lack in nearness, they nearly makeup in numbers.

Man-made Noise

usually between 1 to 600 MHz and usually most intense in industrial and densely populated areas.

•Automobile and aircraft ignition, electric motors and switching equipment, leakage from high voltage lines, fluorescent lamps, etc.

Internal Noise

White, Johnson, or Thermal Noise
•Shot Noise
•Partition Noise
•Excess Noise
•Transit-time Noise

Thermal Agitation or White Noise

Produced by random motion of electrons in a conductor due to HEAT.

Shot Noise

Due to RANDOM VARIATIONS in current flow in ACTIVE DEVICES.

Partition Noise

Similar to shot noise but occurs only in devices where a SINGLE CURRENT separates into TWO or MORE PATHS.

Excess Noise

Also called FLICKER NOISE or 1/f NOISE because NOISE POWER varies INVERSELY with FREQUENCY.

•Also called PINK NOISE because there is PROPORTIONATELY MORE ENERGY at the LOWFREQUENCY end of the spectrum.

Transit-Time Noise

Any MODIFICATION to a stream of CARRIERS as they pass from INPUT to OUTPUT of a DEVICE produces an IRREGULAR, RANDOM VARIATION.

Harmonic Distortion
•Intermodulation Distortion
•Impulse Noise
•Interference

Types of Correlated Noise

Harmonic Distortion

• is when UNWANTED HARMONICS of a signal are PRODUCED through NON-LINEAR AMPLIFICATION.

Intermodulation Distortion

•It is the generation of UNWANTED SUM and DIFFERENCE FREQUENCIES when two or more signals are amplified by a NONLINEAR DEVICE.

Impulse Noise

•It is characterized by HIGHAMPLITUDE PEAKS of SHORT DURATION in the total noise spectrum.

•Consists of SUDDEN BURST of IRREGULARLY SHAPED PULSES.

Interference

•It is a form of EXTERNAL NOISE that means to TO DISTURB or DETRACT FROM.

•Electrical interference is when INFORMATION SIGNALS from ONE SOURCE produce FREQUENCIES that FALLS OUTSIDE their ALLOCATED BANDWIDTH and INTERFERE with ANOTHER SOURCE

•Signal-to-Noise Power Ratio

*It is the RATIO of the SIGNAL POWER level to the NOISE POWER level.

Noise Figure (NF)

*simply Noise Factor expressed in dB.

Noise Factor (F)

*FIGURE OF MERIT used to INDICATE how much SIGNAL-TONOISE RATIO DETERIORATES as a SIGNAL passes through a CIRCUIT or SERIES OF CIRCUITS.

Fiber Optics Communications System

An electronic communication system that uses light as a carrier of information.

• Optical Transmitter • Optical Fiber • Optical Receiver

Components of Fiber Optics Communications System

• Greater information capacity • Immunity to crosstalk • Immunity to static interference • Environmental immunity • Safety • Security • Economics

Advantages of Fiber optics

• Interfacing costs • Strength • Remote electrical power • Specialized tools, equipment, and training

Disadvantages of Fiber optics

Reflection

• The angle of incidence is equal to the angle of reflection.

Refractive Index

• The ratio of the velocity of propagation of the light ray in free space to the velocity of propagation of light ray in a given material.

Refraction

The bending of light ray as it travels from one material to another material with different density.

Snellʼs Law

• Also known as Descartes' law, the Snell‒Descartes law, and the law of refraction.
• States that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of velocities in the two media, or equivalent to the opposite ratio of the indices of refraction.

Critical Angle

• The minimum angle of incidence at which light ray may strike the interface of two media and result in an angle of refraction of 90°.

Acceptance Angle

• It is the maximum angle in which external light rays may strike the airfiber interface and still propagate down the fiber.
• Also called Acceptance Cone Half-Angle

Acceptance Cone

Rotating the acceptance angle around the fiber axis.

Numerical Aperture

• Closely related to Acceptance Angle.
• It is the Figure of Merit commonly used to measure the magnitude of the acceptance angle.
• Described as the light gathering ability of an optical fiber

Mode

means path or ways light may travel into the optical fiber.

Single and Multi mode

types of mode

Index Profile

The graphical representation of the value of the refractive index across the fiber

• Step index • Graded index

types of index profile

Step Index Optical Fiber

• A fiber with a core with uniform refractive index.

• The core is surrounded by an outside cladding with uniform refractive index less than that of the core.

Graded Index Optical Fiber

• The refractive index of the core is non-uniform.
• The refractive index at the core is highest at the center and decreases gradually with distance toward the outer edge.

• Single-mode Step Index
• Multi-mode Step Index
• Multi-mode Graded Index

Optical Fiber Configurations

Maximum Core Radius

• Core radius is proportional to the wavelength and the numerical aperture of the fiber.

Cutoff-Wavelength

The minimum wavelength that permit single mode operation.

• Attenuation
• Absorption
• Material or Rayleigh Scattering losses
• Chromatic or Wavelength Dispersion
• Radiation Losses
• Modal Dispersion
• Coupling Losses

Fiber Optic Losses