The variability of microstrips formulas as a source of uncertainty in microwave setups

Microstrips are used quite often to connect microwave measuring equipment to PCB mounted devices and represent a relevant element of the whole test setup. Their characteristics (the most relevant the characteristic impedance) may be determined by design or later experimentally; in any case they represent a relevant source of uncertainty that must be accounted for. This work reports in full, verifies and compares formulations appearing in the literature of the last 50 years; the study is carried out by sensitivity analysis (for the most relevant geometrical parameters and the dielectric permittivity of the substrate) and by comparison with experimental results.