Fast sampling DCO for 2.4 GHz wake-up receiver

This Letter reports an active inductor digitally controlled oscillator (DCO) for fast switchable low power wireless wake-up receivers. The LO output is held low when the enable pin is high and it oscillates when the enable pin goes low. The MOS transistor is used to turn on the oscillator for 200 ns (Ton) to mitigate the requirement of wake-up receivers (Tcycle = 1 μs). To save the die area, a symmetric differential-pair active inductor topology with 4-bit capacitor bank is proposed. The implemented circuit has one tenth of the chip size of LC oscillator.