An apparatus and a method. The apparatus includes passive mixers, wherein each of the passive mixers includes a first input for receiving BBI, a second input for receiving BBI, a third input for receiving BBQ, a fourth input for receiving BBQ, a fifth input for receiving a first clock signal with a unique phase shift within one of the passive mixers, a sixth input for receiving a second clock signal with a unique phase shift within one of the passive mixers, a seventh input for receiving a third clock signal with a unique phase shift within one of the passive mixers, an eighth input for receiving a fourth clock signal with a unique phase shift within one of the passive mixers, and at least one output; and a voltage-domain vector summation array connected to the output of each of the passive mixers.