RF Engineering for Wireless Networks

Appendix 5 Power Density

1. Rederiving P

In Chapter 5 we provided a heuristic argument to derive an equation for the power density that could be delivered by a propagating potential. In this appendix we provide a somewhat more exhaustive (or perhaps just exhausting) justification for this formula.

The question we wish to address is how much power is carried in a plane wave potential? This is the same as asking how much power can such a potential deliver to a physical object? One way of getting to the answer is to imagine a plane wave impinging upon a region in which the potential can induce a current (Figure A5-1).

In Figure A5-1 we have asserted a particular relationship between the potential and current and a resulting behavior of the potential. ...