Traditional spatial frequency response (SFR) measurement, as defined by the ISO 12233 slanted-edge methodology, encounters significant measurement uncertainties and operational constraints when applied to wide-angle imaging systems. While recent updates to the standard incorporate polynomial edge-fitting to mitigate geometric warping, the underlying linear-edge model remains inherently limited by directional anisotropy and sampling phase instabilities at critical field angles. Furthermore, the rigid alignment requirements of slanted edges—often compromised by distortion-induced slope deviations—necessitate time-consuming mechanical orientation of the device under test (DUT) or the test target. This paper proposes a robust Circular-Edge SFR framework that synthesizes the broadband spectral coverage of the slanted-edge with the rotational invariance of the Siemens star. By employing a sub-pixel centroiding algorithm and a 60° tangent-aligned sector projection, the proposed method achieves continuous sampling phase integration and simultaneous extraction of SFR in any orientation, e.g., sagittal and tangential. Validation using synthetic equidistant projection models at a 100° field angle demonstrates that the circular-edge maintains high-fidelity measurements where traditional slanted edges collapse due to localized geometric stress. Notably, the superior azimuthal robustness and rotational symmetry of circles eliminate the 'critical angle' sampling failures. The framework provides a high-precision, alignment-independent solution for evaluating the image quality of wide-angle and fisheye camera systems.