Patent ID: 7333790

Claim:
A radio frequency (RF) phase shifter comprising: a transconductor for producing first and second currents from an input voltage; a 90 degrees phase shifting circuit coupled to the transconductor, the 90 degrees phase shifting circuit having a first circuit portion for shifting the first current and a second circuit portion for shifting the second current; a gain controller for providing a first gain to the first current and a second gain to the second current; and an adder coupled to the first and second circuit portions of the 90 degrees phase shifting circuit and for adding the shifted and gained first current with the shifted and gained second current; wherein, when the gain controller is turned off, the 90 degrees phase shifting circuit provides the first current and the second current with a phase angle of 90 degrees with respect to each other and the adder adds the first current and the second current to generate an output current having a phase angle of 45 degrees with respect to the first current; and wherein, when the gain controller is turned on, the gain controller provides the first gain and the second gain to the 90 degrees phase shifting circuit to vary the phase angle of the output current with respect to the first current.