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Conducted-Emission Port Spectrum Estimator

Pass trapezoidal-wave harmonics line by line through a passive filter with source/load terminations and first-order parasitics to estimate the port RMS voltage spectrum; this is not a receiver measurement or compliance decision.

FORMULAv1.0.0
INPUT PARAMETERS

Enter the Thevenin switching source and port network

Calculate port RMS voltage harmonic by harmonic. Rs and all component parasitics must be entered from the circuit, a model, or measurements.

THEVENIN SOURCEOpen-circuit trapezoidal excitation
LOADED TWO-PORTFilter network and port

L1 series inductor

C1 load-side shunt capacitor

CALCULATION RESULT

Calculation result

Calculated locally
∿

Enter the parameters and run the calculation to see results and model assumptions here.

FORMULA & TRACEABILITY

Formulas and applicability

Formulas, variables, and model boundaries are published. References last reviewed on 2026-09-01.

3 formulas · 3 references
CORE EQUATIONS

Core equations

These equations directly produce the primary results and define the tool’s core model.

2
F01

Discrete Harmonics Through the Network

Vport,n = Vsource,n · H(nf₀)，n = 1, 2, …, N

Derive exact discrete RMS harmonics from the periodic trapezoidal Thevenin source, then evaluate the same complex two-port at each n·f₀. Harmonics are not connected into a continuous spectrum.

Vsource,n
Open-circuit RMS voltage of Thevenin-source harmonic nV RMS
H(nf₀)
Complex voltage transfer including source/load terminations1
Vport,n
Load-port RMS voltage of harmonic nV RMS
Applicability
  • Linear time-invariant, small-signal sinusoidal steady state
  • The trapezoidal input is the Thevenin open-circuit voltage
  • Evaluate only at integer harmonic frequencies
F02

Terminated Two-Port Voltage Transfer

H=1/(A+B/RL+RS·C+RS·D/RL)，H₀=RL/(RS+RL)

ABCD parameters follow the actual order of series L and shunt C elements with first-order parasitics. H₀ is the port-voltage reference after removing the filter under the same source and load.

A,B,C,D
Total ABCD chain parameters of the filter network—
RS
Thevenin source series resistanceΩ
RL
Equivalent purely resistive port loadΩ
Applicability
  • Source and load are purely resistive in this version
  • Component parameters are treated as constant across the analysis band
  • Not equivalent to the frequency response of a real LISN/AMN
DERIVED & CONVERSION

Derived and conversion equations

Derive units, levels, and supporting engineering quantities from the core values.

1
F03

Port Level and Loaded-Voltage Insertion Loss

Lport,n=20log₁₀(Vport,n/1 μV)；ILn=20log₁₀(|H₀|/|H(nf₀)|)

Convert each sinusoidal port component RMS value to dBμV. Insertion loss compares voltages with and without the filter under identical terminations. Neither value is a quasi-peak or average receiver reading.

Lport,n
Port RMS voltage level of harmonic ndBμV
ILn
Loaded-voltage insertion loss of harmonic ndB
Applicability
  • Only nonzero spectrum lines are converted
  • RBW, detector, dwell time, and measurement uncertainty are not modeled
REFERENCES

References

01Texas Instruments · Application Report SCAA082A, Section 1.2 Clock SignalsHigh-Speed Layout Guidelines2017 revision · Explains that Fourier harmonics of finite-edge digital waveforms depend on edge time, providing the ideal source-spectrum basis for this chain.
02Keysight Technologies · Application Note 5992-2693S-Parameters and Two-port MeasurementsOfficial application material · Describes two-port networks and T/ABCD chain parameters; this project evaluates complex voltage transfer under specified terminations.
03IEC / CISPR · CISPR 16-2-1:2014 + AMD1:2017Specification for radio disturbance and immunity measuring apparatus and methods — Conducted disturbance measurementsConsolidated version · Used only to establish that formal conducted-disturbance measurement requires defined apparatus, methods, and conditions. This page neither reproduces the standard text nor makes a compliance decision.
Engineering use notice

Results use the models and assumptions shown on this page for design estimates and pre-compliance risk review. Complex structures, dispersion, near-field coupling, and test setup can cause significant deviation.

PRE-COMPLIANCE SUPPORT

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