<![CDATA[This paper presents the design and experimental realization of a 5th-order Chebyshev microstrip low-pass filter (LPF) based on a Stepped Impedance Resonator (SIR) integrating T-shaped stub topology at center frequency (fc) 5.575 GHz for synthetic aperture radar (SAR) system applications. Two topologies are systematically compared: conventional SIR and SIR T-shaped stub (SIRS T-Shaped), and both are fabricated on Rogers 5880 substrate. The simulation was conducted using two electromagnetic simulations as perform cross-validation. The measurement results show that the SIRS-T topology achieves insertion loss (IL) S21 of -4.67 dB at the center frequency with a transmission zero (Tz) depth of -61.46 dB at 12.24 GHz, while the conventional SIR yields IL S21 of -8.2 dB, well beyond the acceptable degradation threshold. The deviation may be attributed to practical factors such as fabrication tolerances, conductor and dielectric losses, soldering effects of SMA connectors, and parasitic discontinuities introduced by the embedded T-shaped structure. The SIRS-T structure demonstrates clear superiority in harmonic suppression and roll-off sharpness, establishing it as the preferred LPF architecture for C-band SAR for UAV payload applications.]]>
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