2.5 CHAPTER SUMMARY

Analog signals vary continuously, whereas digital signals represent information using discrete levels. Both are ultimately realized as physical waveforms, so the same basic signal quantities are relevant to communications and RF safety.

A sinusoid is described by amplitude, frequency, and phase. Complex periodic waveforms can be represented as combinations of sinusoidal components, making time-domain and frequency-domain descriptions complementary ways of examining the same signal.

Frequency determines wavelength and helps define how a signal propagates, interacts with antennas and objects, and is treated by RF exposure limits. Bandwidth describes the range of frequencies occupied by a signal; ideal rectangular pulses have infinite bandwidth, while practical systems use filtering and pulse shaping to limit spectral occupancy.

Signal magnitude may be expressed as peak, peak-to-peak, RMS, or a time-averaged value. For RF exposure work, RMS and square-law averaging are essential because heating and power are related to the square of field strength. Far-field plane-wave relationships connect RMS electric field, magnetic field, and power density, but do not generally apply in the near field.