Microstrip patch antennas are common for GNSS applications due to their low profile, small size, ease of fabrication, and low cost. Typically, the radiation characteristics of a single-element patch antenna are fixed, with an inability to electronically control the radiation characteristics in azimuth and elevation. This paper presents a single-aperture (i.e., single-element) GNSS patch antenna that can electronically control the radiation characteristics, by placing an area of high directivity with a commensurate area of low directivity in a particular direction that may be useful for interference suppression. Here, the performance of a circular four probe-fed GPS L5 patch antenna over a circular ground plane is illustrated with an amplitude and phase control subsystem for pattern control. The overall design approach is outlined and supported with computational electromagnetic model (CEM) simulations and measured results. The fabrication of the antenna is illustrated and the measured results at the component level and anechoic chamber radiation characteristics are presented to illustrate the pattern control aspects of the antenna. Gain (i.e., directivity) suppression is achieved at, above, and below the horizon in the commanded null direction, with gain suppression at the horizon varying from 4-13 dB and null depth varying from 22-35 dB. This control has a major advantage by controlling the radiation characteristic to allow for mitigation of interfering signals at, above, and below the horizon.