Sig & Sys Mod 1 Lec 2

Formula for instantaneous power of a signal

x(t) is unitless

Formula for Signal energy over a given time interval. I.e power dissipated over the time period

Formula for Signal energy over it’s entire duration

Formula for Average Power of a signal

What is an Energy Signal

Signal energy is a finite value, signal average power is 0.

Most finite duration signals of interest are energy signals

What is a Power Signal

Signal energy is infinite, signal average power is a finite value.

Periodic signals (& some other “sustained” signals) are power signals

RMS formula

Circuit interpretation of RMS values

the RMS value of an alternating periodic signal is
the magnitude of a constant signal that yields the same power dissipation as the time-
average power dissipation of that alternating signal.

Interpret this graph

1. Peak Value (A)

2. RMS, Effective Value (A/sqrt(2))

3. Equation, Acos(w+θ)

What is Crest Factor

The Crest Factor of a signal is defined as the ratio of it’s peak values to effective value.

The Crest Factor reflects the purity of a signal or waveform, & the capability of a system to handle a particular current or voltage.

Interpret this graph

They have the same RMS value, however the red line requires components that can tolerate the higher peak of voltage or current without breaking