Octagonal phase rotators

A method for generating output signals of phase from an octagonal phase rotator apparatus, said generated output signals dependent on a digital control code, the method comprising:

• using an I-DAC of an I-mixer for steering current between positive and negative phases of an in-phase signal in dependence on k I-DAC control bits of said control code, each control bit controlling switching of a first current unit between said phases,
• receiving, at a set of amplifiers, said phases of the in-phase signal and weighting each phase, in dependence on current steered to that phase by the I-DAC, to produce a weighted output signal;
• using a Q-DAC of a Q-mixer for steering current between positive and negative phases of a quadrature signal in dependence on k Q-DAC control bits of said code, each control bit controlling switching of a said first current unit between said phases,
• receiving, at a further set of amplifiers, said phases of the quadrature signal and weighting each phase, in dependence on current steered to that phase by the Q-DAC, to produce a weighted output signal;
• switching, at a respective IQ-DAC component of an IQ-mixer comprising n IQ-mixer units each comprising the respective IQ-DAC, a second current unit between said in-phase and quadrature signals in dependence on a respective bit of n IQ-DAC control bits of said code, and between the positive and negative phases of the in-phase and quadrature signals via I and Q polarity switches respectively of that component, and
• receiving at a set of amplifiers said phases of said signals and weighting each phase, in dependence on current steered to that phase by the IQ-DAC component, to produce a weighted output signal, wherein the I and Q polarity switches of at least some different IQ-DAC components are arranged to switch in dependence on different I-DAC control bits and Q-DAC control bits respectively;
• and
• summing, at a summation circuit, the weighted output signals from the I-mixer, Q-mixer and IQ-mixer to produce said output signal.