Image rejection ratio
Encyclopedia
In radio
, the image rejection ratio, or image frequency rejection ratio, is the ratio
of (a) the intermediate-frequency
(IF) signal level produced by the desired input frequency to (b) that produced by the image frequency. The image rejection ratio is usually expressed in dB
. When the image rejection ratio is measured, the input signal levels of the desired and image frequencies must be equal for the measurement to be meaningful.
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
, the image rejection ratio, or image frequency rejection ratio, is the ratio
Ratio
In mathematics, a ratio is a relationship between two numbers of the same kind , usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two which explicitly indicates how many times the first number contains the second In mathematics, a ratio is...
of (a) the intermediate-frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
(IF) signal level produced by the desired input frequency to (b) that produced by the image frequency. The image rejection ratio is usually expressed in dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
. When the image rejection ratio is measured, the input signal levels of the desired and image frequencies must be equal for the measurement to be meaningful.