Apparatus and methods for vector modulator phase shifters

A phase shifter with wideband operation, the phase shifter comprising:

• a quadrature filter configured to filter an input signal to generate an in-phase (I) voltage and a quadrature-phase (Q) voltage;
• a first variable gain amplifier (VGA) configured to amplify the I voltage to generate an I current;
• a second VGA configured to amplify the Q voltage to generate a Q current;
• and
• a current mode combiner configured to combine the I current and the Q current to generate an output signal, wherein a first gain setting of the first VGA and a second gain setting of the second VGA are operable to control a phase shift between the output signal and the input signal, wherein the current mode combiner comprises a cascode transistor, the current mode combiner configured to combine the I current and the Q current to generate a combined current that flows through the cascode transistor.

A method of phase shifting, the method comprising:

• filtering an input signal to generate an in-phase (I) voltage and a quadrature-phase (Q) voltage;
• amplifying the I voltage to generate an I current using a first variable gain amplifier (VGA) of a phase shifter;
• amplifying the Q voltage to generate a Q current using a second VGA of the phase shifter;
• combining the I current and the Q current to generate an output signal using a current mode combiner of the phase shifter;
• and
• controlling a phase shift between the output signal and input signal by controlling a first gain setting of the first VGA and a second gain setting of the second VGA,
• wherein combining the I current and the Q current to generate the output signal includes summing the I current and the Q current to generate a combined current, and providing the combined current through a cascode transistor of a common-gate stage or a common-base stage.