The table at the right shows the equivalency of the two, however the upper right and lower left cell values are not normally used because of the aforementioned difference in broadband/narrowband. % Ratio 5 10 20 30 40 50 60 1.05 : 1 1.11 : 1 1.22 : 1 1.35 : 1 1.50 : 1 1.67 : 1 1.85 : 1 67 100 120 133 150 160 163 2 : 1 3 : 1 4 : 1 5 : 1 7 : 1 9 : 1 10 : 1
Page 21 Omnidirectional or merely weakly directional antenna receives or radiates essentially in all directions. These are employed once the relative position on the other station can be unknown or human judgments. They are likewise used at lower frequencies when a directional antenna can be too large, or maybe to cut costs in applications when a directional antenna is just not required. Directional or beam antennas that happen to be intended to preferentially show or receive in a particular direction or maybe directional pattern. In common usage "omnidirectional" usually refers to all horizontal guidelines; typically with reduced performance on the way to the sky or the bottom (a truly isotropic radiator is just not even possible). A "directional" antenna usually is intended to maximize its coupling towards the electromagnetic field on the way to the other stop, or sometimes to pay a particular sector such as a 120° horizontal fan pattern when it comes to a panel antenna at the cell site. Here is an example of 3-dimensional or Omni-directional radiation pattern as show in figure.
Page 22 Example radiation pattern for Omni-directional antenna (figure 1) This is an example of a donut shaped or toroid radiation pattern. In this case, along the z-axis, which would correspond to the radiation directly overhead the antenna, there is very little power transmitted. In the x-y plane (perpendicular to the z-axis), the radiation is maximum. These plots are useful for visualizing which directions the antenna radiates . Typically, because it is simpler, the radiation patterns are plotted in 2-d. In this case, the patterns are given as "slices" through the 3d plane. The same pattern in Figure 1 is plotted in Figure 2. Standard spherical coordinates are used, where polar angle theta for plots in spherical coordinates is the angle measured off the z-axis, and phi, the azimuth angle of spherical coordinates in antenna patterns is the angle measured counterclockwise off the x-axis.
Page 23 2-Dimensional Radiation Pattern (Figure 2) In case if someone is unfamiliar with light patterns or spherical coordinates, it might take a while to discover that Figure 2 represents a similar radiation pattern since shown in Amount 1. The radiation pattern for the left in Figure 2 will be the elevation pattern, which represents the plot on the radiation pattern as a function of this angle measured journey z-axis (for a set azimuth angle). Watching Figure 1, we observe that the radiation design is minimum in 0 and one hundred eighty degrees and gets maximum broadside for the antenna (90 degrees journey z-axis). This corresponds for the plot on this left in Amount 2.
- Summer '19