A complex quantity, given by (α + jβ), of a two-port network terminated in its image impedances. It is half the natural logarithm of the complex ratio of the steady-state volt-amperes input to output of the network:
where E1, I1 and E2, I2 are the voltages and currents at the input and output terminals, respectively.
The real part (α) of the image transfer constant is the image attenuation constant; the imaginary part (jβ) is the image phase constant. Compare propagation coefficient.