441 (Analog Modulation)

Communication

Process of establishing a link between 2 or more people through a transmission medium.

Terminal Equipment

Equipment that converts info into a language ot can understand (eg. computer)

Nodes

Power stations; for routing and computing.

Types of Transmission Media

Broadcast and Point-To-Point

Noise

Signal interference that can be produced internally and externally

Signal

Function that represents a physical quantity and contains info about it.

Electronic Comms Systems Classifications

Transmission type (baseband or modulation comms)

Type of info signal (Analog or Digital)

Direction (Simplex, Half Duplex, Full Duplex)

Modulation

Process of impressing a high frequency carrier signal on a lower frequency Intelligence signal.

Modulation advantages

Improves signal quality, reception quality, transmission range.

Prevents signal mixing and reduces antenna height.

Aids multiplexing.

Types of Analog Modulation

Amplitude, Pulse and Angle.

Amplitude Modulation

amp of carrier frequency varied with amp of modulating signal

Angle Modulation

Sine wave carrier angle is varied from reference value.

Types of Angle Modulation

Frequency and Phase Modulation

Frequency modulation

Carrier signals INSTANTANEOUS frequency is proportionally varied with modulating signals amplitude

Phase Modulation

carriers’ phase angle is proportionally varied to modulating signals amplitude

Demodulation

Extraction of intelligence signal from carrier signal.

Amplitude Demodulation Techniques

DAED - Diode Amplifier Envelope Detector

Synchronous Detector

Product Detector

Types of Amplitude Modulation

DSB

DSB SC

SSB

VSB

Angle Modulation advantages over Amp Mod

Less noise, power efficient, system fidelity

Angle Modulation Applications

RB

2WR

CR

TVST

FM Transmitter Block Diagram

AI, RM, CO, BA, FM, DA, POA, A

FM Reciever Block Diagram

RFA, M, IFA, AFVA, AFPA, S, Oscillator connected to AFVA and M.

Instantaneous Voltage formula for phase mod

weird L = A sin (Wc + Mp sin Wi t)

Instantaneous Velocity Eqn for freq mod

wierd L = A sin (Wct + Mf sin Wit)

Transmission Medium Impairments

Attenuation, Distortion, Noise.

Types Of Transmission Mediums

Fiber optics, Co axial Cables, Telephone networks, Wired pairs, Telex Networks.

Groups/Types of Transmission Media

Bounded and Unbounded Media

Examples of Bounded Media

Coaxial cables, Optical fibres, Telex networks, Twisted pair cables

Unbounded Media Examples

Radio waves, Infra red, Satellites, Ultra sonic

Types of External Noise

Man made, Atmospheric and Space Noise

Man made noise

Usually a spark producing mechanism, occurs randomly at 500MHz

Atmospheric Noise

occurs because of earth's natural disturbances eg lightning in a thunderstorm

Space Noise

noise from celestial bodies; solar and cosmic noise (noise from sun and stars)

Types of Internal Noise

Thermal noise

Transistor noise

Thermal noise

Delays electrons and varies resistors’ pd

Johnson'ss Noise

Noise produced by resistance/resistors

Noise Power Formula

Pn = kT◇f

where k = 1.38 ×10^ 23

for max power transfer…?

Rl = Rs and voltage noise must be equal in those places.

Power noise formula

Pn = kT◇f

Voltage Noise formula

Vn = [4kT◇fR]^0.5

Transistor Noise Formula

In = [2q Idc ◇f]^0.5