Impact of Image Frequency Operation on Vector Mixer Characterization

This article presents the features of image mixers analysis when determining a phase shift of frequency conversion devices. The authors analyzed the change in the phase of intermediate frequency components when measuring the sum and difference of two mixers. Having the intermediate frequency networks characterized separately before the mixer measurements, we could observe how the change between positive and negative sideband components affects the overall frequency response of a network with series or parallel combinations of two mixers. It was shown that, due to the change from positive to negative part of frequency spectrum, the amplitude response remains to be the same, while the phase response is changed only for intermediate frequency networks. The phase response of each mixer, radio frequency and local oscillator networks are kept constant. The obtained results imply the need for two separate calibration techniques, at the intermediate and image frequencies, when determining the frequency response of a mixer under test.