looking for info on homebrewing 900mhz ism sector antenna's

[Batman]

looking to build high gain dual polarity sector antenna's in the 900mhz ism band.

anyone ever come across someone who has already done this?

i'm assuming it's similar to a stacked dipole array with a rear reflector and that the degree of horizontal radiation is determined by how far away the dipoles are from the reflector.

looking for 90 or 120 degree. i've seen the 120 degree antenna's and they cost some insane amount close to $800.00 for a 3 panel array.

i'm thinking it can't be any harder than homebrewing wifi antenna's for 2.4ghz.