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2 years ago in Electrical Engineering By Akshay R

Cavity Model Equations for Optimizing Microstrip Patch Feed for 50‑ Match

The cavity model treats the patch as a resonant cavity with magnetic walls on edges and electric walls on top and bottom. Input impedance is computed as Zin≈1/(G±jB)Z_{in} ≈ 1/(G ± jB)Zin?≈1/(G±jB), where G is radiative conductance and B is fringing susceptance. Feed point location along the patch edge is derived from desired edge impedance. Transmission line extensions can refine the match. Designers use this approach to optimize microstrip feeds while preserving radiation characteristics.

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By Nkumardo Answered 1 year ago

Cavity model gives input impedance: Zin ≈ (1/(G±jB)), with conductance G from radiation and susceptance B from fringing. Feed location x from edge for 50Ω: x ≈ (L/π) × acos(√(50/Z0)) where Z0 is edge impedance (~200–300Ω). More accurate: transmission line model with effective length extension ΔL.
 

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