Vector Modulator Using An IQ Mixer

A vector modulator is a device that can modulate an input signal’s amplitude and phase. In this video, we show how an IQ mixer can be utilized as a vector modulator by using two bias tees to inject DC current into both the I and Q ports. Injecting DC current into the I and Q ports forward biases the IQ mixer cores, causing them to be shorted.

This connects the RF and LO baluns, allowing the input signal to pass from balun to balun without a frequency conversion. Modulating the DC current into either or both I and Q mixers allows the user to modulate the phase and amplitude of the signal based on the polarity and magnitude of the input current.