Equal physical length can produce different electrical lengthRogers 77 GHz radar PCB: Material & Design Decisions. Engineering illustration, not a production photograph or test result.Equal physical length can produce different electrical lengthRogers 77 GHz radar PCB: Material & Design DecisionsPath AReference structure APath BReference structure BPhase = 360° × length / guided wavelengthGuided wavelength depends on effective permittivity and frequency.