System, methods and apparatus are described that facilitate communications circuit design. A first response of a channel to a first signal transmitted through the channel and a second response of the channel to a second signal transmitted through a neighboring channel are determined and a first signal analysis based on the first response and the second response is calculated. A modified second response is determined after modifying the magnitude or timing of the second response to simulate a change in a characteristic of the second signal. A second signal analysis performed using the first response and the modified second response may identify differences in the effects of the second signal and the modified second signal on the first signal. A physical relationship between a pair of connectors of a circuit may be modified based on the magnitude of a scaling factor or phase difference used to obtain the second response.