Antenna Technology and Signal Transmission Explained
Understanding Antenna Technology and Signal Transmission
Full-Duplex Transmission on DSL
Full-duplex transmission on DSL operates in two modes, utilizing frequency division range (BW) for echo cancellation.
DMT Modulation
DMT (Discrete Multitone) modulation involves using discrete multitones.
TRC (Television Receiver Circuit) Basics
A TRC works by passing an electron gun beam through an array of glass to a phosphor screen. This screen contains selected colors (red, blue, and green) that vary in intensity based on the electron beam’s strength.
Aliasing Explained
Aliasing is an incorrect representation of curves and diagonal lines on a screen.
Television at 100 MHz
Television at 100 MHz utilizes a processor and 3-port RAM, refreshing the screen twice as fast.
Safety Standards
Key safety standards include:
- MPR II
- TCO 9x
- Energy Star
Laptop Screen Types
Different types of screens used in laptops include:
- TFT LCD
- DSTN LCD (Single Scan, Dual Scan, and Fast Scan)
- Active Matrix (utilizing a FET transistor behind each pixel)
Halo Effect
The halo effect is a trail left by moving images, commonly seen on older LCD displays.
TN Technology
TN (Twisted Nematic) technology is used for laptop screens.
Backlight Technology
Backlight technology illuminates LCD screens, such as those found in calculators.
HD Ready Label
The HD Ready label indicates that a device supports high definition (1280×720).
SED Technology
SED (Surface-conduction Electron-emitter Display) technology is based on having a TRC for each pixel on the screen.
TMDS Protocol
TMDS (Transition Minimized Differential Signaling) protocol facilitates the connection between the graphics card and the monitor.
OLED Technology
OLED (Organic Light Emitting Diode) is a new technology in LCD monitor development.
Antenna Polarization
Polarization in an antenna refers to the direction in which the signal arrives.
Forms of Polarized Electromagnetic Signals
Different forms include:
- Vertical
- Horizontal (more frequent)
Dipole Definition
A dipole is the resonant element that captures the signal.
Balanced Systems
In a balanced system, a balun is not necessary, and the impedance between the antenna and cable is adjusted.
Common TV Antennas
A commonly used receiving antenna in TV is the Yagi antenna.
Balun Definition
A balun is an impedance adapter used between the antenna and cable.
Antenna Equivalent Circuit
An antenna is equivalent to an electrical circuit, specifically RL (Resistor-Inductor).
Dipole and E Relationship
The relationship between a dipole and E (electric field) is proportional (E/2, E/4, E/8, etc.).
Technical Characteristics of Antennas
Key technical characteristics include:
- Gain
- Directivity
- Front/Back Ratio (D/A)
- Operating Frequency
- Impedance
- Wind Load
Antenna Gain
Gain is the ratio between the maximum voltage seen by the antenna and the voltage seen by a dipole.
Antenna Directivity
Directivity is the angle at which the antenna receives the signal.
Antenna Lobe Graph
The lobe graph shows the relationship between the gain and directivity of the antenna.
Lobe Relationships
Lobe relationships can be indicated in two ways:
- Attenuation as references to the maximum value (0 dB)
- Gain/attenuation to 0 dB as a reference in the case of a simple dipole
Antenna Opening Angle
The opening angle of an antenna indicates the points at which the antenna decreases by 3dB.
Opening Angle Types
The opening angle can be:
- Vertical
- Horizontal
Increasing Antenna Bandwidth
To increase the bandwidth of an antenna, two options are available:
- Increase the surface area of the drivers that form the antenna
- Add electrical circuits that resonate the antenna at different frequencies
Antenna Wind Load
The wind load on an antenna is the resistance the antenna offers to the wind, indicated by the manufacturer in km/h.
Types of TV Antennas
Types of TV antennas include:
- Yagi antenna
- Panel antenna
- Logarithmic antenna
Yagi Antenna Lobe
The lobe of a Yagi antenna is more closed when the antenna is more directive (more directors), and less closed when it is less directive.
Directory and Reflector
A directory is the element in front of the dipole that makes the antenna more directive. A reflector is an element behind the dipole that increases gain and counters interference.
Coupled Antenna Systems
Coupled antenna systems are used:
- Horizontal: To give more directivity to the antenna and avoid interferences.
- Vertical: To give more directivity to the antenna and avoid interferences from the ground.
- ë/4: For interference, annular phase.