Rayengine said:
Hi,
Any good articles best describe the antenna diverity?
If we assume using two antennae
(1) How these two antenna oriented?
(2) In what distance should be separated ?
Any idea welcomed!
Rayengine
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RAYENGINE,
AS you've noticed there's a lot of diversity of ideas about antenna diversity.
From ITT's Reference for Radio Engineers:
I thas been shown that if two or more high-frequency radio channels are sufficiently separated in SPACE, FREQUENCY, ANGLE of arrival, TIME, or POLARIZATION, the fading on the various channels is more or less independent. Diversity systems make use of this fact to improve the overall performance, combining or selecting separate radio channels on a single high-frequency circuit.
Satisfactory diversity improvement can be obtained if the correlation coefficient of the fading on the various channels does not exceed about 0.6, and experiments have indicated that a frequency separation of the order of 400 Hertz gives satisfactory diversity performance on long high-frequency paths. (for FREQUENCY DIVERSITY)
SPACE DIVERSITY
Spacing between antennas at right angles to the direction of propagation should be about 10 WAVELENGTHS.
POLARIZATION DIVERSITY has been found to be about equivalent to space diversity in the high-frequency band.
TIME DIVERSITY
Measurements have indicated that times varying from 0.05 to 95 seconds may be necessary to obtain fading correlation coefficients as low as 0.6 in HF time-diversity systems.
ANGLE of ARRIVAL diversity requires the use of large antennas so as to obtain the required vertical directive characteristics. Differences in the angle of arrival of 2 degrees have been shown to give satisfactory diversity improvement on HF links.
Interesting topic
johnseven