This paper presents a high-gain X-band rectangular microstrip patch antenna with edge feed for spaceborne Synthetic Aperture Radar (SAR) applications. The increasing demand for high-resolution Earth Observation (EO) Satellite imagery prompts a growing necessity for high-gain antennas. PTFE (Teflon) substrate with a relative permittivity of 2.1 is used in this design which ensures high-frequency performance and resilience to space radiation. This substrate also delivers impedance stability, minimizing signal and dielectric losses. The substrate height has been set to 3 mm, a choice deemed more efficient for antenna performance. The antenna was simulated using HFSS with a fractional bandwidth (FBW) of 8.57% (8.7–9.48 GHz), which is depicted by the reflection coefficient (S11). A return loss of − 17.1 dB and a high gain of 8.1591 dBi is simulated at the resonant frequency (9 GHz). The proposed antenna has good impedance matching which makes it suitable for SAR applications.