  A closed electromagnetic resonant chamber (RC) is a highly favorable
artificial environment for wireless communication. A pair of antennas within
the chamber constitutes a two-port network described by an impedance matrix. We
analyze communication between the two antennas when the RC has perfectly
conducting walls and the impedance matrix is imaginary-valued. The transmit
antenna is driven by a current source, and the receive antenna is connected to
a load resistor whose voltage is measured by an infinite-impedance amplifier.
There are a countably infinite number of poles in the channel, associated with
resonance in the RC, which migrate towards the real frequency axis as the load
resistance increases. There are two sources of receiver noise: the Johnson
noise of the load resistor, and the internal amplifier noise. An application of
Shannon theory yields the capacity of the link, subject to bandwidth and power
constraints on the transmit current. For a constant transmit power, capacity
increases without bound as the load resistance increases. Surprisingly, the
capacity-attaining allocation of transmit power versus frequency avoids placing
power close to the resonant frequencies.
