Electromagnetic Reverberation Chambers

Appendix 2

Formulas of the Quality Factor of a Rectangular Cavity

A2.1. Quality factor of the TM_{m n p} mode

We will reproduce the formula established by Liu of the TM_{m n p} mode [LIU 83]:

[A2.1]

The notation conventions are recalled below:

[A2.2]

[A2.3]

We find in [A2.1] the impedance of the Z_w plane wave and the surface resistance of the walls of the R_s cavity:

[A2.4]

a, b and d are the dimensions of the cavity.

A2.2. Calculation of the average quality factor

We will not recall the whole development of the Liu calculation, which is reproduced in detail in [LIU 83]. This appendix will limit itself to the framework of the calculation.

The computation is established for an over sized cavity, in the bandwidth occupied by a mode interfering with other modes, whose population will only increase with the frequency of the RF emission. According to the description proposed in section 2.3.2, we consider that the Δ f_{m n p} bandwidth belongs with the mode tuned on the f_{m n p} frequency. Knowing that ...