This paper presents the design of a bandpass filter using a microstrip with an open loop resonator, both simulated and realized. The design uses a rectangular resonator with radial stubs. This paper discusses a symmetrical rectangular resonator shape with a variation in the feeder section. The bandpass is designed to work at S-Band frequencies, with a center frequency of 3 GHz. The design, simulation, and realization of this bandpass filter use NPC-H220A substrate material with a dielectric constant (varepsilonr) of 2.18, and the thickness of this substrate is 1. 2 ~ m m. The objective of designing this bandpass filter is to obtain several response parameters, including insertion loss, return loss, and a narrow bandwidth. The design, simulation, and realization of this filter are presented with key response parameters, including a return loss of 23.709 dB, an insertion loss of 0.666 dB, and a resulting bandwidth of 130 MHz at 3 GHz, along with the realization of the bandpass filter. The complete results will be presented in this paper. © 2024 IEEE.