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This paper presents a monolithic transmission- line-based ring resonator dual-mode active bandpass filter (BPF) fabricated in a standard 0.13-μm complementary metal-oxide-semiconductor (CMOS) technology. The dual-mode ring resonator comprises a quasi-TEM complementary-conductive- strip transmission-line loop and a shunt metal-insulator-metal perturbation capacitor. Two CMOS cross-coupled pairs are integrated with the ring resonator symmetrically, forming a robust approach, which both enhances the quality factor of dual modes and reduces the resonator size significantly. Basic characteristics of the filter are discussed, including the unloaded resonant frequencies, transmission zeros, coupling coefficients, Q-enhancement mechanism, linearity, noise, and power consumption. The area of the proposed dual-mode active BPF is 270 × 270 μm2 (0.02 λ0 × 0.02 λ0) without dc-biasing circuits and pads. The measured results, in good agreement with the simulated data, demonstrate 0-dB insertion loss at the center operating frequency of 24.1-GHz, bandwidth of 640 MHz (2.32% fractional bandwidth), passband ripple of 0.556 dB, P1 dB of -25.43 dBm, IIP3 of -10.57 dBm, and noise figure of 14.7 dB under voltage supply of 1.8 V and current of 3.0 mA.