Differential Injection-Locked Frequency Tripler with a Low-coupling 8-shaped Transformer

This letter designs an injection-locked frequency tripler (ILFT) fabricated in a 0.18 μm CMOS process. The ILFT uses a voltage-controlled oscillator (VCO) with a one-turn center-tapped 8-shaped inductor for low interference noise coupling and it also uses a frequency tripler with a common source inductor for frequency doubler generation. The above two inductors are configured as a low coupling transformer for die area saving. The fabricated ILFT with the low-coupling transformer occupies an area of 1.146×0.484 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> including the buffer and the oscillation frequency is tunable from 7.61 GHz to 9.81 GHz. The operation range is from 7.2 GHz to 10.25 GHz.