A probe calibration device that includes a first offset element having a substantially rectangular first aperture. The probe calibration device includes a tuned pass element disposed adjacent to the first offset element. The tuned pass element has a non-rectangular second aperture. The probe calibration device includes a second offset element disposed adjacent to the tuned pass element and on a side opposite the first offset element. The second offset element has a substantially rectangular third aperture. The probe calibration device includes a backing element disposed adjacent to the second offset element. The first offset element, the tuned pass element, the second offset element and the backing element form a cavity.