  Bias lines routed over a ground plane naturally form microstrip lines
associated with the presence of a capacitance. This can lead to unwanted
resonances when coupled to Josephson junctions. This work presents an
electrical model of a shunted Josephson junction with its bias lines and pads,
fabricated with the 1 kA/cm$^2$ RSFQ niobium process of the FLUXONICS Foundry.
A compact LCL T-model is used to simulate the microwave behavior of the bias
line, predict resonances and design resonance-free superconducting circuits.
The I-V characteristics of three shunted Josephson junctions have been obtained
from time-domain simulations done with JSIM and show a good match with the
global behavior and experimentally observed resonance at 230 GHz, measured at
4.2 K. The influence of the position and value of a series resistor placed on
bias lines is studied to damp unwanted resonances at the junction.
