Category: Telecommunication Systems
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Microwave Active Devices: Types, Features & Operation
Generally microwave devices can be categorized as either passive components or active components. We have already talked about microwave passive components in this other article. This article focuses on microwave active devices. They may be classified into two types: … Read more
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Microwave Passive Components: Types & Functions
The part of the electromagnetic spectrum referred to as the microwave region loosely includes 1-300 GHz for practical purposes. These microwave bands are especially advantageous for transmission services such as satellite transmission, telephone transmission, broadcasting of commercial radio & television, … Read more
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Frequency Synthesizer – Features, Operation & Applications
Frequency synthesis is a technique of producing a range of frequencies with crystal-controlled stability. A frequency synthesizer uses phase-locked loop (PLL) to generate output frequencies over a wide range. The typical range is from 1 MHz to 160 MHz. Fig: … Read more
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Phase-Locked Loops (PLL) – Features, Operation & Applications
Features of a Phase-Locked Loop (PLL) A phase-locked loop (PLL) is a form of a servo system which consists of a phase detector, low-pass filter and voltage controlled-oscillator (VCO) as illustrated in the block diagram below. The phase detector compares … Read more
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Radio Frequency (RF) Signal Generator – Features & Applications
A radio frequency (RF) signal generator is used in generating high frequency signals at a specific frequency for testing laboratories. The output frequency may range for example from about 100 kHz to around 40 GHz. A typical RG generator consists … Read more
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Diode & Filter Applications in Amplitude Modulation (AM) Detection Circuits
The operation of a typical AM audio frequency signal is illustrated in the Figure 1.0 where vin is the modulated signal that is shown Figure 1.1. Figure 1.0 AM detector circuit A typical amplitude modulated signal that is fed … Read more
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Open Systems Interconnection Communication (OSI) Model
Developed by the ISO (International Organization for Standards) in 1983, the Open Systems Interconnection (OSI) reference model divides communication functions into seven-layer standard protocol system. The OSI model is a framework for developing a coordinated system of standards. The seven … Read more
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How Cellular Communication Systems Works
In cellular communication systems, there is a two-way wireless transmission between the cellular phone handset and the base station tower. The cell phone converts the audio signals into electrical form using a microphone. This information is imposed on a high … Read more
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Features of Optical Modulators in Telecommunication Systems
Light emitting PN junction devices such as LEDs and laser diodes are easily modulated by superimposing signals on to the injected current. This is direct modulation. Laser diodes in high-bit rate and long-span optical communication systems are often used under … Read more
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Network Access Control Techniques
Access control methods are required in a network to ensure that only one user of the network is able to transmit at any one time. In ring-based local area networks (LANs), two commonly employed techniques are: Token passing Slot passing… Read more