05-07-2013, 04:12 PM
Measurement of Antenna and Characteristics & Microwave Link Design
Measurement of Antenna.pptx (Size: 100.48 KB / Downloads: 19)
Introduction
Antenna measurement techniques refers to the testing of antennas to ensure that the antenna meets specifications or simply to characterize it. Typical parameters of antennas are gain, radiation pattern, beam width, polarization, and impedance . We shall discuss the few characteristics….
Radiation Pattern Measurement
The two antennas are at fixed distance . The transmitting antenna is fixed while the test antenna is attached with calibrated rotating system.
The antenna under test is rotated stepwise in clockwise and anticlockwise direction . For every position of antenna , elevation angle ᶿR(degree) and corresponding received power(pr) are noted . These values are noted in observation table. It should be remembered that calibrated rotating system is rotated from +90 degree to -90 degree.
MICROWAVE LINK DESIGN
Microwave link design is a methodical and systematic process which includes the following calculations :
Loss/attenuation calculations
Fading and fad margins calculations
Frequency planning and interference calculations
Quality and availability calculations
Loss/attenuation calculations
The loss calculations are composed of the following two main contributions.
Propagation losses
Branching losses
The propagation losses are due to Earth`s atmosphere while branching losses comes from the hardware used to deliver the transmitter/receiver output to/from the antenna
Fading and fad margins calculations
Fading is defined as the variation of the strength of a received radio carrier signal due atmospheric changes and/are ground and water reflections in the propagations path.
Types of fading
Multiple fading
Rain fading
Refraction-diffraction fading
Quality and availability calculations
The main purpose of the quality and availability calculations is to set up reasonable quality and availability objectives for the microwave path.