APP B
The Decibel (dB)
The unit of power is Watt (W). One watt is equal to one ampere (A) of current flowing through an electrical potential difference of one volt (V). However, microwave engineers have to deal with quantities that are very large or very small and the ratio of two quantities. In this context, the relative unit gives more information. Hence, power is expressed in decibel (dB), which is the ratio of power at a point of measurement to reference power (say input power). For example, a cellular base station might transmit approximately 80 W of power in a macro cell. The mobile phone receives power of about 0.000 000 002 W only, which is 0.0000000025% of the transmitted power. When expressed in dBs, which is logarithmic ratio, it ...
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