Bidirectional variable gain phase shifter

A bidirectional variable gain phase shifter comprising:

• a first circuit including a pair of first differential signal terminals that receive or output differential signals and four first quadrature signal terminals that receive or output quadrature signals, the first circuit being configured to operate as an I/Q generator in a first direction and to operate as a vector combiner in a second direction opposite to the first direction;
• a second circuit including four second quadrature signal terminals respectively connected to the four first quadrature signal terminals and a pair of second differential signal terminals, the second circuit being configured to operate as a vector combiner in the first direction and to operate as a variable gain differential amplifier in the second direction;
• and
• a control circuit configured to control the second circuit through first, second, third, and fourth bias current sources,
• wherein the first direction is from the first circuit toward the second circuit, and the second direction is from the second circuit toward the first circuit,
• wherein, during a forward operation, a first DC bias currents flowing through the two second differential signal terminals are controlled to be substantially equal, and during a reverse operation, a second DC bias currents flowing through the four second quadrature signal terminals are controlled to be substantially equal.