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Group

Signal

Signal

Communicated information: a piece of informationcommunicated by an action

Means of communication: an action, gesture or sign as a mean of communication

Incitement: something that incited somebody to action

Electronics transmitted information: information transmitted by means of modulated current or an electromagnetic wave and received by telephone, telegraph, radio or radar

Spectra

Signal spectra (plural of spectrum) describe thefrequency content of the signal

Spectrum is a condition or value that is not limited to aspecific set of values but can vary infinitely within a continuum

Evolved from old english “Spectre” meaning ghostor apparition but the modern meaning now comesfrom it’s use within science`

First scientific use of word spectrum is within the field of optics.it is used to describe the rainbow of colors in visible light whenseparated using prism (prismatic diffraction)

Analog signal

Any variable signal continuous in both time and amplitude. Any information can be conveyed by an analog signal, often such a signal is measured response to changes in physical phenomena, such as sound, light , temperature, position or pressure, and is achieved using a transducer.

This signal uses some property of medium to convey the information. Electrically, the properties commonly used are Voltage followed closely by frequency, current and charge

Digital Signal

Is a digital representation of discrete-time signal which is often derived from analog signal. An analog signal is a datum that changes over time

Discrete-time signal is a sampled version of an analog signal: the value of the datum is noted at fixed intervals rather than continuously. If individual time values of the discrete-time signal, instead of being measured precisely (which would require an infinite number of digits) and are approximated to a certain precision – which therefore, only requires a specific number of digits - then the resultant data stream is Digital Signal

Digital Signal

Quantization – the process of approximating the precise value within a fixed number of digits

SIGNAL PROCESSING

Signal Processing

Refers to extracting information from a signal, conditioning a signal for subsequent use,

signal transformation or altering a signal structure

Analog signal Processing

Any signal processing conducted on analog signals by analog means. Specifically the mathematical algorithm that processes the the signal is implemented with analog electronics in which the mathematical values are represented as a continuous physical quantity, an analog, usually as voltage, electric current or electric charge around some components in the electronic devices. A small error or noise affecting such physical quantities will result in a corresponding error in the signals represented by such physical quantities

Digital Signal Processing (DSP)

Is the study of signals in a digital representation and the processing methods of signals.

Four major subfields of DSP are:a. Audio signal

processingb. Control

engineeringc. Digital image

processingd. Speech

processing

Transmitter

It is the device that generates high frequency power, which, by means of a suitable antenna, is radiated or transmitted through space, or through conductors or through obstructive media, such as walls and glass

It may be modulated with information, (noise, voice, pictures). This modulation or information may be received and demodulated in a receiver, where the combination of transmitter and receiver is known as radio system.

AM TransmitterLow-level modulation approach

AM TransmitterHigh level modulation approach

Radio Receiver

Is understood to mean any device which is intended to receive a radio signal and extract the information or intelligence (modulating signal) from the rf signal (carrier signal)

Tuned Radio Frequency (TRF)

Composed of several tuned-radio frequency amplifiers followed by circuits to detect and amplify the audio signal

Superheterodyne

Invented by Edwin Armstrong in 1918

Characteristic of Good Receiver

Selectivity – ability of the receiver to receive the desired signal and reject all others

Sensitivity – ability of the receiver to amplify weak signals

Fidelity – it is the ability of the receiver to faithfully reproduce the information

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