What is the front-to-side ratio of the antenna radiation pattern shown in Figure E9-1?

Front-to-side ratio indicates how well a directional antenna rejects signals arriving exactly from the side. It compares the antenna's maximum forward signal strength against its gain at exactly 90 degrees off-axis. In Figure E9-1, the main forward peak rests on the 0-degree line at the 0 dB outer ring. To find the side gain, look at the horizontal axis intersecting the 90-degree and 270-degree lines. Tracing the radiation pattern to where it crosses the 90-degree axis, the plot intersects exactly at the -14 dB circle. The difference between the 0 dB forward peak and the -14 dB side intersection provides a front-to-side ratio of exactly 14 dB.