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directivity(dÿ-rek-tiv -ă-tee) A measure of the ability of an antenna to concentrate its radiation or response in a particular direction. It is defined as the ratio of the maximum radiation intensity in the forward direction to the average radiation intensity over all directions. If an antenna is operating at a wavelength λ and has an effective area A e (see array), then the directivity, D , is given by
D = 4πA e /λ2
See also gain.
The ability of a logic circuit to ensure that the input signal is not affected by the output signal.
The value of the directive gain of an antenna in the direction of its maximum value.
The ratio of the power measured at the forward-wave sampling terminals of a directional coupler, with only a forward wave present in the transmission line, to the power measured at the same terminals when the direction of the forward wave in the line is reversed; the ratio is usually expressed in decibels.