| CPC H03H 11/20 (2013.01) | 12 Claims |
|
1. A radio frequency (RF) phase shifter, comprising:
an input terminal;
an output terminal;
a quadrature hybrid comprising first, second, third, and fourth ports; and
first and second varactors, wherein each varactor comprises first and second ends, and
wherein:
a capacitance of each varactor changes by changing an external bias voltage applied to the first and second varactors,
the input terminal of the RF phase shifter is connected to the first port of the quadrature hybrid, and the output terminal of the RF phase shifter is connected to the fourth port of the quadrature hybrid,
the first end of the first varactor is connected to the second port of the quadrature hybrid, the first end of the second varactor is connected to the third port of the quadrature hybrid, and the second ends of the first and second varactors are connected to a ground conductor,
the RF phase shifter is configured to receive RF signals through the input terminal, pass the RF signals through the quadrature hybrid to the second and third ports of the quadrature hybrid, and reflect the RF signals from the first and second varactors into the quadrature hybrid,
the RF signals reflected from the second and third ports reach the first port with a 180 degrees phase difference, resulting in no reflection at the first port of the quadrature hybrid and the input terminal of the phase shifter, and the RF signals reflected from the second and third ports reach the fourth port of the quadrature hybrid and the output terminal of the phase shifter with a same phase shift, resulting in a constructive interference at the fourth port,
the phase shift of the RF signals at the fourth port of the quadrature hybrid and the output terminal of the phase shifter is equal to −270 degrees plus a phase shift that is a function of the external bias voltage applied to the first and second varactors,
the quadrature hybrid is positioned on a top surface of a substrate, each of the first and second varactors further comprises:
a plurality of active switches inside the substrate, each active switch comprising:
first and second conducting elements;
a conducting triangular plate, wherein a first side of the conducting triangular plate is connected to the first conducting element of the active switch; and
a gap layer between the second conducting element and a tip of the conducting triangular plate that is opposite the first side, and
the external bias voltage is applied between the first and second conducting elements of the active switches of each varactor.
|