A Tiny Complementary Oscillator With 1/f3 Noise Reduction Using a Triple-8-Shaped Transformer

This letter presents a triple-8-shaped transformer-based complementary oscillator. It features tiny area, wide tuning range (TR), electromagnetic compatibility (EMC), and low flicker phase noise (PN), combining the merits of both LC-tank and ring oscillators. We identify that after suppressing the second-harmonic voltage by the complementary operation itself, the third-harmonic current entering the capacitive path is now the main cause of asymmetry in the rising and falling edges, leading to the 1/f noise upconversion. By tuning the capacitance ratio between gate and drain nodes of the switching transistors, it mitigates the third-harmonic voltage and introduces a specific gate-drain phase shift, reducing the 1/f
³
PN. Fabricated in 22-nm FDSOI CMOS, the prototype occupies an area of 0.01 mm
²
and achieves 1/
³
PN corner of 70 kHz, PN of -110 dBc/Hz @1MHz and Figure-of-Merit (FoM) of -182 dB at 9 GHz, 39% TR, resulting in the best FoM with normalized TR and area (FoM
_TA
) of -214 dB@1 MHz.