1. A system comprising:an analyzer connected to a radio frequency port of a device under test wherein said device under test comprises a mixer;
an additional external device connected to said analyzer via a radio frequency port of said additional external device, and connected to said device under test, wherein said additional external device comprises an additional mixer;
a local oscillator connected to a local oscillator port of said device under test and a local oscillator port of said additional external device, via a power divider; and
a first switch connecting said device under test to a second switch, a third switch connecting the additional external device to the second switch, wherein the second switch connects the first switch and the third switch to a vector voltmeter.