Phase
Phase is not a property of just one RF signal but instead involves the relationship between two
or more signals that share the same frequency. The phase involves the relationship between the
position of the amplitude crests and troughs of two waveforms.
Phase can be measured in distance, time, or degrees. If the peaks of two signals with the same
frequency are in exact alignment at the same time, they are said to be in phase. Conversely, if the
peaks of two signals with the same frequency are not in exact alignment at the same time, they
are said to be out of phase. Figure 2.7 illustrates this concept.
What is important to understand is the effect that phase has on amplitude when radio cards
receive multiple signals. Signals that have 0 (zero) degrees phase separation (in phase) actually
combine their amplitude, which results in a received signal of much greater signal strength, or
twice the amplitude. If two RF signals are 180 degrees out of phase (the peak of one signal is
in exact alignment with the trough of the second signal), they cancel each other out and the
effective received signal strength is null. Depending on the amount of phase separation of two
signals, the received signal strength may be either cumulative or diminished.