E T = E 1 +E2 +E3 HT < H1+H2+H3 E2 H1 E3 H2 H3 Parallel flight paths run perpendicular to the target 27 Figure 4. Line-abreast configuration for collaborative EW. Properly configured and sequenced, this configuration can act as a linear array with power density gain of 2 N d / λ exactly on broadside (and lesser power density gain further from broadside). figuration. We will look more closely at this in a future installment. POINTS TO REMEMBER FOR "BACK OF THE ENVELOPE" What do we need to remember when making "back of the envelope" calculations for collaborative EW? Here are the important points: 1) Conservation of energy is absolute. If a result violates conservation of The Journal of Electronic Defense | January 2018 E1 energy, go back and check the work, including any assumptions. 2a) The uniform plane wave is a simple special case that is useful for teaching but fails to take into account conservation of energy. It is not a general result and should be used with caution. 2b) The uniform plane wave proportionality of power flow density and power to the square of the electric field is a special case result and cannot be applied to a generalized EM field. 3) General EM power flow requires proper calculation of both the electric and magnetic fields, and then finding the EM power flow density from the vector cross product. And no, the math is not easy, but you really don't have a choice if you want to get it right.