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In this paper, a second-order digitally controlled oscillator, based on subharmonic injection locking, is presented. The prototype design is implemented in a 0.18 /spl mu/m standard CMOS process. The implemented injection-locked oscillator, with a resonant frequency of 1.1 GHz, provides a low phase noise of -99.7 dBc/Hz at a 50 KHz offset. The oscillator is injection-locked with the eleventh harmonic of a low frequency 100 MHz PLL. Using switched-capacitor banks, the oscillator can be digitally tuned to within 300 KHz of the injection locking frequency which allows it to be locked with an input signal as low as - 53 dBm. The oscillator has an overall tuning range of 20% and together with an input amplifier consumes only 688 /spl mu/W when powered by a single 1.6V supply voltage.