SPITE 0.1.2

Scattering Parameter Inspection Tool for Engineers

"The secret ingredient is SPITE :D"

1. Introduction

SPITE is a lightweight single-file Python library for RF network analysis, built so undergraduate students can learn the basics of RF/microwave engineering and run simulations outside of class or internships without needing expensive, license-gated software.

SPITE is built around the Network class, which represents RF networks using frequency data, scattering parameters, reference impedance, and schematic information. Python operators are used for 1-port and 2-port network composition: @ for cascading and ** for repeating networks.

2. Features

• The entire library is in one file
• Conversion between S, Z, Y, and ABCD parameters in both directions
• Lumped R, L, C and transmission line elements (2-port and 1-port)
• Schematics for 2-port and 1-port networks
• @ for cascading 2-port and 1-port networks
• ** for repeating a 2-port network
• Linear, dB, phase, group delay, and Smith chart plots
• Time-domain gating
• Touchstone file import and export
• Very important functions such as esqueleto() and merendola() (for reasons beyond RF engineering)

3. Limitations

Features not yet implemented

• Frequency dependent / complex reference impedance
• General N-port topology / circuit connection
• Components such as waveguides, microstrips, etc.
• Noise factor as a network parameter / property

Try using scikit-rf for more advanced RF engineering.

4. Installation

SPITE depends on NumPy and Matplotlib. Nothing else.

pip install spite

In a notebook environment, run the following cell to install SPITE:

!pip install spite -q  # -q is optional

Then start your Python script or notebook with:

import numpy as np
import spite as sp

SPITE imports Matplotlib internally. So importing Matplotlib again is unnecessary unless you want to make custom plots.

5. Examples

Quarter-wave matching network

f = np.linspace(0.1, 4e9, 100)  # frequency sweep

# Zc = sqrt(Z0*R) is the quarter-wave matching condition
matching_network = (
    sp.net2p_tline_series(f=f, f0=1e9, EL_deg=90, Zc=np.sqrt(50 * 75))
    @ sp.net1p_R(f=f, R=75)  # terminates the network with a 75-ohm load
)

matching_network.plot_schematic()  # horizontal stack of SYM2P_TLINE_SERIES + SYM1P_R
matching_network.plot_dB()  # S11 in dB

A quarter-wave transformer of Zc = sqrt(Z0 * R_L) matches a 75Ω load to a 50Ω system exactly at f0.

RLGC ladder

f = np.linspace(0.1, 4e9, 100)  # frequency sweep
R, L, G, C = 1.5, 5e-9, 3e-4, 2e-12  # R, L, G, C values of one section

ladder = sp.net2p_RLGC(f, R, L, G, C) ** 3  # ** repeats the section 3 times

ladder.plot_schematic()
ladder.plot_dB(port_indices=(2, 1))  # S21 in dB
ladder.plot_smith()  # color gradient encodes frequency

Lumped-element low-pass filter

f = np.linspace(0.1, 4e9, 100)  # frequency sweep

filter = (
    sp.net2p_L_series(f, 3.9785e-9)
    @ sp.net2p_C_shunt(f, 3.184e-12)
    @ sp.net2p_L_series(f, 3.9785e-9)  
)

S11_at_2GHz = filter.sample(2e9, param="S", port_indices=(1, 1))
print(20 * np.log10(np.abs(S11_at_2GHz)))  # -3.0127 dB 

filter.plot_dB(floor=-30, port_indices=[(1, 1), (2, 1)])
filter.plot_smith(port_indices=[(1, 1), (2, 1)], chart_type="Y")  # Admittance charts are available as well

This exact filter was cross-checked against an AWR Microwave Office simulation of the same design. SPITE's predicted response matched to within 0.01 dB at the 2 GHz cutoff.

6. License and Citation

SPITE is released under the 0BSD License

• You can use, modify, and share SPITE freely.
• Attribution is appreciated but not required.
• The software comes as is, with no warranty.

A bibtex is provided below for those who would like to use it:

@software{spite,
  author  = {Lee, Anthony Jeongseok},
  title   = {SPITE: Scattering Parameter Inspection Tool for Engineers},
  year    = {2026},
  url     = {https://github.com/anthonyjlee377/spite},
  version = {0.1.2}
}

7. Disclosure

• SPITE is an independent project unaffiliated with any supervisor or institution.
• Generative AI has been used in the development of its source code and initial documentation. The source code is subject to human review and validation. The single-file source code is intended to serve as learning material for students in future versions, and therefore requires a balance between computational efficiency and pedagogical clarity to reflect this goal.