In this work, the physical and electromagnetic modelling of a double barriers InGaAs/AlAs resonant tunnelling diode (RTD) oscillator was performed using a 4 μm2 mesa area diode with a peak current density of 3.3 mA/μm2 integrated with a coplanar waveguide resonator. A 100 GHz oscillator was realized with an output power of 83 μW by utilizing the diode’s negative differential resistance feature. The equivalent circuit model of the diode was extracted using a fitting model for the RTD’s measured I-V characteristics. Advanced design system (ADS) software was used to model the circuits. To ensure the circuit’s performance at 100 GHz, all parasitic elements associated with the passive components were considered and modelled. Additionally, the stabilizing resistance’s effect on the extracted power was discussed.