Designing microstrip antennas with wide bandwidth and low-frequency capabilities presents several challenges. These difficulties mainly arise due to the relatively small size of the microstrip in comparison to the operating frequency. Therefore, achieving a combination of enhanced bandwidth and lowerfrequency cut-off becomes crucial to support a broad frequency range of communication technologies. This paper presents a method for enhancing the bandwidth of a circular microstrip antenna based on an inverted C-shaped ground configuration. The proposed method successfully creates an antenna with extended bandwidth while lowering the operating frequency. The antenna was simulated and then fabricated using an RO5880 duroid substrate with a relative permittivity of 2.2, a thickness of 1.575 mm, and a loss tangent of 0.0009. The simulation and measurement results demonstrate that the antenna can operate effectively within a wide frequency range of 3.5 GHz to 18 GHz. Additionally, utilizing this method enables the antenna to function at even lower frequencies and wider bandwidth without the need for additional dimensions.