Radio frequency phase shifter with variable input capacitance

A radio frequency (RF) phase shifter comprising:

• a hybrid coupler to generate a first output and a complementary second output in response to a received RF signal;
• a vector modulator amplifier having an amplification stage to produce an amplified voltage, the amplification stage having a first amplifier with a first input coupled to the first output of the hybrid coupler and a second amplifier with a complementary second input coupled to the complementary second output of the hybrid coupler, a vector modulation stage coupled to the amplification stage to receive the amplified voltage and to produce a modulated vector, the vector modulation stage having an in-phase section and a quadrature section to control a phase of the modulated vector in response to a phase control signal, and a varactor coupled across the first input and the second input of the amplification stage, the varactor adjusting a capacitance between the first input and the second input in response to a capacitance control signal;
• a combiner to combine an output of the in-phase section and an output of the quadrature section and to generate a modulated vector;
• and
• a varactor controller coupled to the varactor to generate the capacitance control signal in response to a phase control signal.

A method comprising:

• amplifying a first input coupled to a first output of a hybrid coupler in an amplification stage to produce a first amplified voltage;
• amplifying a second input coupled to a second output of the hybrid coupler in the amplification stage to produce a second amplified voltage, wherein the first input and the second input are complementary;
• receiving the first amplified voltage and the second amplified voltage and producing a modulated vector in a vector modulation stage coupled to the amplification stage having an in-phase section and a quadrature section to control a phase of the modulated vector in response to a phase control signal;
• adjusting a capacitance between the first input and the second input at a varactor coupled across the first input and the second input of the amplification stage in response to a capacitance control signal;
• and
• operating in a high performance mode at the varactor by disabling a capacitive connection between the first input and the second input.