A 4 X 4 butler matrix beamforming network used to feed a phased array of antenna elements.
S18 (blue curve) shows some phase deviation from S15 (red curve)
- Derive the equations for microstrip dimensions of hybrid couplers, delay and Crossover blocks
- Reduces or even eliminates all box resonance modes of the microstrip layout model
Credit : Angular Beamforming Technique for MIMO Beamforming System.pdf and EDABoard forum