Performance of offset prime focus reflectors as a function of feed orientation

Radiation characteristics of the offset paraboloidal reflectors illunminated by a tilted prime-focus feed are studied employing the physical optics current method. A family of curves is generated which indicates the optimum orientation of the axis Of the feed for maximum antenna efficiency as a function of the offset angle\betaand the half-angle\alphasubtended by the rim of the reflector at its focus. A comparative study on efficiency and sidelobe levels is presented for different excitation angles of the feed axis.