SPICE Model of a Single Twisted-Wire Pair Illuminated by a Plane Wave in Free Space

A SPICE model for the twisted-wire pair with uniform twists in free space is proposed in this paper, which is capable of calculating the transient terminal response of the twisted-wire pair terminated with nonlinear loads in the presence of a transient plane wave illumination. The model differs from its counterpart for a straight-wire pair in that an extra convolution is included in the source terms, which can be calculated efficiently by the recursive convolution method. For the sake of convenience, the derivation of the model is made in the frequency domain on the basis of the transmission-line theory. The resultant expressions are compared with the outcome of the method of moments, showing that the transmission-line model can be applied to the twisted-wire pair with loose twists. Furthermore, the low-frequency coupling properties and resonant peak of the twisted-wire pairs are investigated according to the derived approximate formulae. Based on the frequency-domain results, a SPICE model for the twisted-wire pair is proposed in the time domain before it is verified and applied to the twisted-wire pair terminated with nonlinear loads.