Appendix D
Useful tables and formulae
D.1 The deciBel
The deciBel (dB) represents a logarithmic ratio between two quantities. Of itself it is unitless. If the ratio is referred to a specific quantity (P2, V2 or I2 below) this is indicated by a suffix, e.g. dBμV is referred to 1 μV, dBm is referred to 1 mW.
Common suffixes
| suffix | refers to |
| dBV | 1 volt |
| dBmV | 1 millivolt |
| dBμV | 1 microvolt |
| dBV/m | 1 volt per metre |
| dBμV/m | 1 microvolt per metre |
| dBA | 1 amp |
| dBμA | 1 microamp |
| dBμA/m | 1 microamp per metre |
| dBW | 1 watt |
| dBm | 1 milliwatt |
| dBμW | 1 microwatt |
Originally the dB was conceived as a power ratio, hence it is given by:
Power is proportional to voltage squared, hence the ...
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