This is a standard unit used in real-life RF system development, and it’s very convenient when, for example, you are calculating a link budget, because gains and losses expressed in dB can simply be added to or subtracted from the output power expressed in dBm. You definitely want to familiarize yourself with the concept of dBm. A straightforward example is amplifier gain: If the power of the input signal is 1 W and the power of the output signal is 5 W, we have a ratio of 5: In contrast, dB is a unit that involves the logarithm of a ratio between two numbers. Current is also an absolute measurement because the unit (amperes) involves a specific amount of charge with respect to a specific amount of time. Voltage is an absolute measurement because we always speak of a potential difference, i.e., the difference in potential between two points usually we are referring to the potential of one node with respect to a 0 V ground node. You cannot say, “The output power is 10 dB.” It is easy to forget that dB is a relative unit. Instead, we will focus on practical aspects of the decibel in the specific context of RF systems. We won’t cover the generic details of decibels because they are already available on this page of the AAC Electric Circuits textbook. It’s a logarithmic unit that provides a convenient way of referring to ratios, such as the ratio between the amplitudes of an input signal and an output signal. If you become deeply entrenched in an RF project, you may find that the word “dB” becomes as familiar to you as your own name.Īs you probably know, dB stands for decibel. One of the most important words that you will need when working in the world of RF is “dB” (and some variants thereof). RF engineering, like all scientific disciplines and subdisciplines, involves quite a bit of specialized terminology. Learn about the decibel and its variants in the context of RF design and testing.

Decibel unit