Brief on PCB Modeling for Sub-THz Transceiver Module Design

Sub-THz transceivers are anticipated to emerge soon for supporting communication systems beyond 5G. Precise printed circuit board (PCB) modeling has therefore become essential for designing these modules. Accordingly, the experimental model extraction for a low transmission loss PCB will be explained in this report. The modeling work is aiming at defining the model parameters of both the dielectric and metal layers while considering the influence of the surface roughness. For extracting the model experimentally, planar transmission lines (TL) had been fabricated on the concerned PCB, measured over a 0.1 to 110 GHz frequency range, and then multi-Thru Reflect Line (m-TRL) calibration was introduced. Ansys Electromagnetic simulator, HFSS, had then been used to simulate the measured TL while optimizing the PCB’s model to fit the associated measurement. Djordjevic-Sarkar formula was referred and defined in HFSS in terms of the sweep parameters to model the dielectric material enabling optimization with the full degree of freedom. Copper conductivity and the snowball radius of Huray roughness model, on the other hand, were optimized on the account of the conductor interconnect under the influence of the surface roughness. A Rat-Race BALUN had been referred as a case study to approve the extracted model. Based on the optimum extracted model, the simulation results are showing a good agreement with the lab measurements. Furthermore, the designed 50 Ohm TL had been optimized and the measurement of the new TL had noticeably shown an enhancement in its performance.