Day 1: Antennas & Beams Flashcards
A theoretical antenna that radiates energy equally in all directions in the shape of a sphere
Isotropic Antenna
Gain is determined by what main elements?
- Directivity
- Efficiency
Describes the antennas capability to transmit and receive
Reciprocity
In a perfect environment, Tx gain = Rx gain
The Reciprocity Theorem
What are the types of gain?
- Active
- Passive
- Computational (AKA coding or synthetic gain)
Boosting the signal strength using power
Active Gain
Focusing the signal in a specific direction without adding power
Passive Gain
Improving signal clarity by using computer processing
Computational Gain
Total power leaving an antenna compared to an isotropic radiator
Effective Isotropic Radiated Power (EIRP)
What are the radiation lobes?
- Main Lobe
- Side Lobe
- Back Lobe
The angular separation between the half-power points on the radiation pattern
Half Power Beam Width (HPBW) (3 dB)
One feed point at the base of the antenna radiating out to the sides, but not above or below
Monopole Antenna
Made up of two conductive wires or rods, with a feedline in the middle connecting to a transmitter or receiver
Dipole Antenna
Optimal for high VHF/low UHF, between 240 to 400 MHz
Yagi-Uda Array
What are the elements of the Yagi-Uda Array?
- Driven Element
- Directors
- Reflector
Circularly polarized to combat Faraday Rotation and scintillation
Yagi-Uda Array
Multiple antenna elements working as a single unit
Array Antenna
Acts as a reflecting mirror - reflect energy to the point of reference
Parabolic Antenna
Widely used for SHF communications
Parabolic Antenna
- Point of reference that gathers the reflected signal
- Focuses signal to amplifier
Feedhorn
Receives a large portion of incoming signal, and focuses on one spot
Sub reflector
A tunnel that guides radio frequency (RF) waves from one point to another
Waveguide
Ensures that the waves travel in a specific direction with minimal loss of energy
Waveguide
Physically splits the orthogonal/perpendicular polarities to different ports for Rx/Processing of dual-polarized signals without interference
Orthomode Transducer (OMT)
