13.3 : 能量和功率信号

Consider an electric system with a resistor. Here, the voltage and current signals enable power and energy measurement across the resistor.

For a continuous-time signal, the total energy over the time interval is defined as the integral of the square of the signal's magnitude over the same interval.

The time-averaged power is calculated by dividing the total energy by the duration of the time interval.

For a discrete-time signal, the total energy over the time interval is computed by summing the squares of the signal's magnitude for all points within the interval, while the average power is found by dividing the total energy by 2N+1.

The expressions for total energy and power are redefined for continuous and discrete signals over the intervals —t1 to t2 and –n1 to n2.

Based on these definitions, there are three major types of signals.

Energy signals have finite total energy, resulting in zero average power.

Power signals have finite average power, which results in infinite energy.

Non-physical signals are signals where neither power nor energy are finite.