Loss
Loss in electromagnetic systems refers to the reduction of signal power as it travels through space or components. It is a key parameter in high-frequency (HF), RF, and EMC applications, where energy dissipation and signal degradation must be quantified and minimized.
Path Loss
Path loss describes the reduction in power density as an electromagnetic wave propagates through space:
PL = (4πd / λ)²
where:
PL: Path loss
d: Distance between transmitter and receiver (m)
λ: Wavelength (m)
This simplified model assumes ideal free-space conditions. In practice, effects such as reflection, diffraction, and absorption also contribute to total loss.
Free Space Path Loss (FSPL)
Free-space path loss quantifies signal attenuation in an ideal environment and is derived from the Friis transmission equation:
FSPL = (4πdf / c)²
or, in logarithmic form:
FSPL[dB] = 20 log₁₀(4πdf / c)
where:
f: Frequency (Hz)
d: Distance (m)
c: Speed of light (≈ 3 × 10⁸ m/s)
Transmission Line Loss
Attenuation in cables or waveguides is calculated using:
α = 10 log₁₀(P₁ / P₂)
where:
α: Attenuation (dB)
P₁: Input power
P₂: Output power
Return Loss
Return loss quantifies how much signal is reflected due to impedance mismatch:
RL = −10 log₁₀(Pᵣ / Pᵢ)
where:
Pᵣ: Reflected power
Pᵢ: Incident power
RL: Return loss (dB)
Higher RL indicates better impedance matching.
Insertion Loss
Insertion loss measures the signal power reduction due to introducing a component:
IL = −10 log₁₀(Pₒ / Pᵢ)
where:
Pᵢ: Input power
Pₒ: Output power
IL: Insertion loss (dB)
Applications
RF communication: Link budget analysis and range estimation
Wireless networks: Signal coverage and degradation modeling
Antenna design: Minimizing loss for improved radiation efficiency
Satellite communication: Long-distance signal analysis
Radar systems: Evaluating signal return strength and propagation effects
EMC testing: Loss modeling in shielding and coupling scenarios
Microwave engineering: Transmission line and component evaluation