This brief presents a 357–706 MHz dual-mode low-pass filter featuring an oscillator-based calibration method to address bandwidth deviations caused by process variations and component mismatches, eliminating the need for a high-frequency reference signal. Compared to conventional replica-based approaches, the proposed dual-mode oscillator calibration improves correlation coefficients from 0.922 to 0.978, as demonstrated by Monte Carlo simulations. Fabricated in 28-nm CMOS technology, the 3rd-order Butterworth active-RC filter occupies only 0.03 mm2 and consumes 3.8 mW from a 0.9 V supply. It achieves a bandwidth range of 357–706 MHz, an input-referred noise of 5.18 nV/Hz???√ , an in-band IIP3 of 17.65 dBm, and a figure-of-merit (FoM) of 0.015 fJ. Pearson’s correlation coefficients between the filter bandwidth and oscillator frequency are 0.96 and 0.97 across temperature ranges from ?60°C to 80°C and supply voltages from 0.8 to 1.4 V, respectively.