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Microstrip losses as a function of width

50 Ohm microstrip transmission line width is feature designed and influenced by the copper and substrate properties and dimensions.
In some instances where low loss is required, it may be beneficial to design for a wider microstrip trace width to minimise conductor losses.

Microstrip dielectric losses are fairly consistent with width for 50 Ohms, but the conductor loss varies considerably. The chart above shows how widening the trace width (with corresponding substrate height increase) can reduce the total transmission line loss.
The benefits are significant for both standard FR4 (orange) and a low loss laminate like Rogers RO4350B (blue). These simulations were performed at 6GHz and include both conductor and dielectric losses.
The conductor thickness was plated 1oz (50um) and the only aspect not included is radiation loss.