This study presents the design, analysis, and optimisation of a rectangular patch antenna for wireless applications in the Ka band. Two distinct substrate materials (Rogers RT6202PR and Rogers RO4003C) have been employed for the antenna designs (Antenna 1 and Antenna 2). To attain optimal performance, the design process entails selecting a suitable substrate material, optimising patch dimensions, and employing a microstrip feeding method. This examination of the antenna’s reflection coefficient (S11), voltage standing wave ratio (VSWR), radiation pattern, gain, directivity, surface current, Smith Chart, and bandwidth is performed utilising diverse simulation methodologies in CST. The antenna is engineered for best performance inside a compact framework, rendering it appropriate for high-frequency communications, including satellite networks, radar systems, and advanced 5G services. The results indicate that the antenna exhibits a return loss above −10 dB and preserves a consistent emission pattern. This validates the antenna’s appropriateness for high-speed wireless applications functioning in the Ka-band. The antenna’s performance regarding return loss, bandwidth, efficiency, and radiation characteristics renders it an appropriate selection for high-frequency wireless applications inside the Ka-band.