hfsynpy

A Python package for high-frequency (HF) microstrip synthesis and analysis.

This package provides tools for the synthesis and analysis of microstrip transmission lines, using the same models as KiCad. Results are generally valid up to 40 GHz, but always verify with full-wave simulation tools for critical designs.

Functional API Overview

This package provides two main functions for microstrip design:

  • synthesize_microstrip: Synthesize the required trace width for a target impedance.
  • analyze_microstrip: Analyze the electrical properties for a given trace width.

Both functions return results as dataclasses for clarity and type safety.

Microstrip Synthesis and Analysis Example

This example demonstrates how to use the functional API of hfsynpy for microstrip synthesis and analysis, including the new features: - Input of electrical angle in degrees for synthesis - Input of physical length for analysis - Output of phase shift (angle) in degrees for a given length - All attenuation values are always per meter (dB/m)

Synthesize Microstrip for Target Impedance and Angle

from hfsynpy import synthesize_microstrip, analyze_microstrip

# Synthesize width for target Z0 and electrical angle (degrees)
syn_result = synthesize_microstrip(
    eps_r=3.66,        # Relative permittivity
    tand=0.0037,       # Loss tangent
    h=1.524e-3,        # Substrate height (1.524 mm)
    t=35e-6,           # Copper thickness (35 um)
    rough=0e-6,        # Surface roughness (0 um)
    sigma=1 / (1.72e-8), # Copper conductivity (5.814e7 S/m)
    mur=1.0,           # Relative permeability (substrate)
    murc=1.0,          # Relative permeability (conductor)
    frequency=2.45e9,  # Frequency (2.45 GHz)
    z0_target=50.0,    # Target impedance (ohms)
    ang_l_target=30.0, # Target angle for length synthesis (degrees)
)
print(f"Synthesized width: {syn_result.width * 1e3:.4f} mm")
print(f"Effective permittivity: {syn_result.epsilon_eff:.4f}")
print(f"Skin depth: {syn_result.skin_depth * 1e6:.4f} um")
print(f"Conductor attenuation: {syn_result.atten_cond:.4f} dB/m")
print(f"Dielectric attenuation: {syn_result.atten_diel:.4f} dB/m")
print(f"Physical length: {syn_result.length * 1e3:.4f} mm")

Analyze Microstrip for Given Width and Length

ana_result = analyze_microstrip(
    width=0.79e-3,     # Trace width (0.79 mm)
    eps_r=3.66,
    tand=0.0037,
    h=1.524e-3,
    t=35e-6,
    rough=0e-6,
    sigma=1 / (1.72e-8),
    mur=1.0,
    murc=1.0,
    frequency=2.45e9,
    length=50e-3,      # Physical length (50 mm)
)
print(f"Characteristic impedance: {ana_result.Z0_0:.4f} ohms")
print(f"Effective permittivity: {ana_result.epsilon_eff:.4f}")
print(f"Skin depth: {ana_result.skin_depth * 1e6:.4f} um")
print(f"Conductor attenuation: {ana_result.atten_cond:.4f} dB/m")
print(f"Dielectric attenuation: {ana_result.atten_diel:.4f} dB/m")
print(f"Angle shift: {ana_result.angle_deg:.4f} degrees")

synthesize_microstrip

Synthesize the required microstrip width for a target impedance.

Parameters

Name Type Default Unit Description
eps_r float required - Relative permittivity (dielectric constant) of the substrate.
tand float required - Loss tangent of the substrate.
h float required m Height of the substrate.
t float required m Thickness of the conductor.
rough float required m Surface roughness of the conductor.
sigma float required S/m Electrical conductivity of the conductor.
mur float required - Relative permeability of the substrate.
murc float required - Relative permeability of the conductor.
frequency float required Hz Frequency of operation.
z0_target float required Ω Target characteristic impedance for synthesis.
ang_l_target float None rad Target electrical length for synthesis.
h_top float 1e20 m Height to top ground plane (very large for single ground plane).

Returns

A MicrostripSynthesisResult dataclass:

Name Type Unit Description
width float m Synthesized trace width.
epsilon_eff float - Effective relative permittivity.
skin_depth float m Skin depth of the conductor.
atten_cond float dB/m Conductor attenuation per meter.
atten_diel float dB/m Dielectric attenuation per meter.
length float m Physical length to reach the target angle.

analyze_microstrip

Analyze a microstrip line for given geometry and material parameters.

Parameters

Name Type Default Unit Description
width float required m Trace width.
eps_r float required - Relative permittivity (dielectric constant) of the substrate.
tand float required - Loss tangent of the substrate.
h float required m Height of the substrate.
t float required m Thickness of the conductor.
rough float required m Surface roughness of the conductor.
sigma float required S/m Electrical conductivity of the conductor.
mur float required - Relative permeability of the substrate.
murc float required - Relative permeability of the conductor.
frequency float required Hz Frequency of operation.
ang_l_target float None rad Target electrical length for analysis.
h_top float 1e20 m Height to top ground plane (very large for single ground plane).

Returns

A MicrostripAnalysisResult dataclass:

Name Type Unit Description
epsilon_eff float - Effective relative permittivity.
skin_depth float m Skin depth of the conductor.
atten_cond float dB/m Conductor attenuation per meter.
atten_diel float dB/m Dielectric attenuation per meter.
Z0_0 float Ω Characteristic impedance.
angle_deg float deg Phase shift for the given length.

Attribution

This package is part of a Python translation of KiCad's C++ source code.

Original C++ code: - © 2001 Gopal Narayanan gopal@astro.umass.edu - © 2002 Claudio Girardi claudio.girardi@ieee.org - © 2005, 2006 Stefan Jahn stefan@lkcc.org - Modified for KiCad: 2018 Jean-Pierre Charras - © The KiCad Developers, see AUTHORS.txt for contributors.

Python translation and modifications: - © 2025 Dominik Mair dominik.mair@uibk.ac.at

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.