fix: more reasonable value

examples/repeated_wave_propagation.jl

@@ -29,7 +29,7 @@ function repeated_wave_propagation(utx::AbstractArray{Complex{T}}, midx, domain:
     zr = 2π / λ * w0^2 / 2
     wz = w0 * sqrt(1 + domain.Dz^2 / zr^2)
     # effective transmit aperture
-    D1 = 2w0
+    D1 = 4w0
     # effective receive aperture, super-Gaussian window function reduces effective domain size to 2*0.47*Dxy (1/e, see split-step-method.jl)
     # D2 = min(2domain.rA, 0.94domain.Dx, 0.94domain.Dy, 2wz)
     D2 = 4wz