fixed feature size

wafer_layouts/single_idt.scad

@@ -47,7 +47,7 @@ scale_unit = 1e3;
 substrate = "SI";
 
 // linbo
-// the aoucstice wave speed in the substrate
+// the acoustic wave speed in the substrate
 c = 3992.0;
 // si
 // c = 3159.0;
@@ -144,7 +144,7 @@ module params() {
             str("leg_length     : ", leg_length),
             str("leg_angle      : ", leg_angle),
             str("size           : ", size),
-            str("feat. size (mm): ", (c/freq)*scale_unit),
+            str("feat. size (mm): ", (c/freq)*1e3 / 4),
             str("version        : ", SCRIPT_VERSION)
         ]
     );