Constraints of Fiber Weave Effect on High-Speed Circuits

High-speed circuits impose special restrictions on dielectrics with smaller constant dielectric permittivity. On these circuits, velocity increases with the decrease of relative dielectric permittivity. On the other hand, the cost of the system will increase due to substrate's cost, as substrates with low loss at higher frequencies, as N4000-13, are more expensive comparing to the most common substrates as FR4, and design cost will also increase due to the need of proper evaluation of the electromagnetic and signal integrity aspects. High speed and ultra-high speed sensors, 5G networks and IoT applications require lower latency and lower jitter, higher data rates and demand timing analyses while minimizing power consumption. In the current paper, we will analyze several aspects on signal integrity, circuits with frequency dependent dielectric models and fiber weave effect (FWE) upon the dielectric model to characterize the composite structure of printed circuit boards' (PCB) substrates. Also, we will study and include in simulation circuit various types of laminated fabrics and describe the impact of fiberglass effect on the proposed circuit. Coupled lines or single ended lines in the proposed circuit model the interconnections on the PCB. Based on these circuits, we represented the reflection and transmission coefficients for two materials that allows analyzes of composite type substrates: FR4 and N4000-13. In order to highlight the FWE, we designed a circuit with two uncoupled lines and we study the reflection and insertion loss that appear with the increase of the frequency.