Antennas, FM Receivers, and Cellular Communication Systems
Antenna Principles
Antennas sense electromagnetic waves and capture a part of them for processing. According to the standard definition by IEEE, an antenna or aerial may be defined as a “means for radiating or receiving radio waves.”
Fig. 1: Source, Transmission Line, and Antenna
Fig. 1 shows the position of an antenna in a transmission system. The source produces a radio frequency (RF) current. The antenna consists of a conductor split at the middle. The RF current is fed into the antenna by a
Read MoreUnderstanding MOSFET Channel Behavior: Voltage Effects
Effect of Source/Drain Voltage on Channel
For either enhancement- or depletion-mode devices, at drain-to-source voltages much less than gate-to-source voltages, changing the gate voltage will alter the channel resistance, and drain current will be proportional to drain voltage (referenced to source voltage). In this mode, the FET operates like a variable resistor, and the FET is said to be operating in a linear mode or ohmic mode.
If drain-to-source voltage is increased, this creates a significant
Read MoreProgramming Languages: Pascal, Basic, Fortran, and Cobol
Pascal. It was designed by Professor Niklaus Wirth at the Federal Institute of Technology in Zurich in 1970. He named it after the seventeenth-century French mathematician Blaise Pascal. The language was first introduced by its designer and later became available for all popular microcomputers.
The main reason that prompted Niklaus Wirth to develop Pascal was to provide a language for educational programming as a systematic discipline, so that the principles of discipline were clearly reflected by
Read MoreElectromagnetic Waves, Bands, and Channels in Television
Electromagnetic Waves and Their Properties
Calculating Frequency and Wavelength
1. If an electromagnetic wave has a repetition period of 5 microseconds, what is its frequency and wavelength?
Solution: Period and frequency are inversely related. Frequency (F) can be calculated using the formula: F = 1/T = 1/(5 * 10-6) = 200,000 Hz. From the frequency, the wavelength (λ) is calculated: λ = c/F = (3 * 108) / (2 * 105) = 1500 m.
2. If an electromagnetic wave has a wavelength of 10 km, what is its frequency
Read MoreShannon-Weaver & Berlo Communication Models: Key Concepts
Shannon-Weaver Information Theory
Key Concepts:
Shannon and Weaver’s information theory distinguishes three levels:
- Technical: Focuses on the fidelity of information transmission.
- Semantic: Deals with the meaning of the message.
- Pragmatic: Concerns the effect of the communication on behavior.
Shannon-Weaver Communication Model
- Source:
- Information
- Message
- Transmitter: Emphasizes sending.
- Channel:
- Noise
- Received signal message
- Receptor
- Destination
The theory conceptualizes information as the degree of freedom to
Read MoreUnderstanding Sound: Properties and Phenomena
The Nature of Sound
Sound is a vibration that spreads through the air. It follows the same principles as when we throw a stone into a pond: the disturbance of the stone causes the water to stir in all directions until their amplitude is so small that it ceases to be perceived.
Frequency
The number of times that this vibration is produced per second is what is known as frequency. The frequency of sound is measured in Hertz (Hz). A person with healthy ears can hear frequencies from 20 to 20,000 Hz.
When
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