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Antenna measurement techniques refers to the testing of antennas in order to ensure that the antenna meets specifications or simply to characterize it. Typical antenna parameters are gain, bandwidth, radiation pattern, beamwidth, polarization, impedance; These are imperative communicative means.
When considering an antenna's directional pattern, gain with respect to a dipole does not imply a comparison of that antenna's gain in each direction to a dipole's gain in that direction. Rather, it is a comparison between the antenna's gain in each direction to the peak gain of the dipole (1.64). In any direction, therefore, such numbers are 2 ...
Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: =. A useful relationship between omnidirectional radiation pattern directivity (D) in decibels and half-power beamwidth (HPBW) based on the assumption of a sin ( b θ ) / b θ {\displaystyle \sin(b\theta )/{b ...
A high-gain antenna (HGA) is a directional antenna with a focused, narrow beam width, permitting more precise targeting of the radio signals. [1] Most commonly referred to during space missions , [ 2 ] these antennas are also in use all over Earth , most successfully in flat, open areas where there are no mountains to disrupt radiowaves.
For the Arecibo antenna at 2.4 GHz, the beamwidth was 0.028°. Since parabolic antennas can produce very narrow beams, aiming them can be a problem. Some parabolic dishes are equipped with a boresight so they can be aimed accurately at the other antenna. There is an inverse relation between gain and beam width.
An antenna's directivity is greater than its gain by an efficiency factor, radiation efficiency. [1] Directivity is an important measure because many antennas and optical systems are designed to radiate electromagnetic waves in a single direction or over a narrow-angle.
The half-power point is the angle off boresight at which the antenna gain first falls to half power (approximately −3 dB) [a] from the peak. The angle between the −3 dB points is known as the half-power beam width (or simply beam width). [4] Beamwidth is usually but not always expressed in degrees and for the horizontal plane.
Since a half-wave dipole has a gain of 2.19 dBi and a radiation resistance of 73 Ohms, a quarter-wave ( 1 / 4 λ) monopole will have a gain of 2.19 + 3.0 = 5.2 dBi and a radiation resistance of about 36.5 Ohms. [13] The antenna is resonant at this length, so its input impedance is purely resistive.