Microstrip antenna elements with internal amplifier slots for spatial power combining reflectarray applications

A new active microstrip antenna element for use in spatial power combining reflectarrays is introduced along with a study of its variations. This new element utilizes a specially shaped slot cut into a square patch to accommodate amplifier components on the same layer within the footprint of the patch. While others have inserted one-port devices in internal slots in a patch, two-port amplification devices have not been inserted in this manner to the authors´ knowledge. Use of MMIC amplifiers that have 50-ohm input/output impedances and simplified biasing techniques eliminates the need for complex matching networks, which would reduce bandwidth and possibly cause spurious radiation. By placing the amplifier inside the patch footprint between the two orthogonal feed locations, the element spacing is greatly reduced as well, since the amplifier does not need to be located between radiating elements. This paper presents a study of the effects of slots of differing size and shape on the standard square microstrip patch in preparation for MMIC amplifier implementation.