radiation pattern

A radiation pattern is the 'shape' of where an antenna sends its energy — a map of how strong the signal is in every direction, usually drawn as a lobed flower around the antenna. It answers the question every wireless engineer asks: if I stand over there, how loud is this transmitter? An omnidirectional antenna draws a circle (loud everywhere on the horizon); a dish draws a single sharp spike (loud one way, silent elsewhere).

The biggest petal is the main lobe — the desired direction — and the smaller petals are side lobes and the back lobe, leaked energy that wastes power or, worse, picks up interference. Key numbers read off the pattern are the half-power beamwidth (the angular width where power has dropped to half, or −3 dB) and the front-to-back ratio. A narrow main lobe means high directivity but a fussy aim, like a spotlight versus a bare bulb.