Patent ID: 6894657

Claim:
A system for bi-directionally modulating a signal and that produces an amplitude and phase shift that is the same for both transmission and reception comprising: a first power divider that splits an input signal into a first output signal and a second output signal, said first output signals and said second output signals having the same phase with respect to one another; a first variable attenuator connected to said first power divider that receives said first output signal of said first power divider to generate a first attenuated signal; a second variable attenuator connecting said first power divider that receives said second output signal of said first power divider to generate a second attenuated signal; a branch line coupler connected to said first variable attenuator and said second variable attenuator that receives said first attenuated signal and said second attenuated signal; said branch line coupler producing a first coupled output and a second coupled output that are in quadrature; a phase shifter connected to said branch line coupler that receives a signal from said second output of said branch line coupler producing a shifted output signal that is phase shifted 180 degrees; a third variable attenuator connected to said branch line coupler that receives said first coupled output from said branch line coupler to generate a third attenuated signal; a fourth variable attenuator connected to said phase shifter that receives said shifted output signal from said phase shifter to generate a fourth attenuated signal; and a second power divider connected to said third variable attenuator and said fourth variable attenuator, said second power divider that receives and combines said third attenuated signal and said fourth attenuated signal, said second power divider that combined said third attenuated signal and said fourth attenuated signal with the same phase with respect to one another, said second power divider that generates a final output signal.