Image rejection mixers provide an IF output to either the lower sideband output or the higher sideband output, depending on whether the RF signal is below or above the local oscillator. Image rejection is accomplished through vector cancellation within the network. This network is formed of an in-phase power divider, two double balanced mixers and two 90° hybrids. An image condition occurs during mixing when both the sum and difference output signals appears in the frequency band. The image is separated from the real signal by vector subtraction, with the level of cancellation obtained usually expressed as a rejection ration in dB.