A digitally tuned 1.1 GHz subharmonic injection-locked VCO in 0.18μm CMOS

A 77 GHz CMOS requency triplers with subharmonic injection locking technology

“…The first issue is that the naturally running frequency of the oscillator must be very close to the desired harmonic of the reference to achieve injection‐locking [9]. In Figure 8 different situations, which occur depending on the injection frequency, are shown.…”

A low noise programmable clock multiplier based on a pulse injection-locked oscillator with a highly-digital tuning loop

“…There has recently been increasing interest in CMOS circuits that leverage injection-locked oscillators, including frequency dividers [1], clock and data recovery circuits [2], and clock multipliers [3]. However, in each of these cases, the injected oscillator is not continuously tuned to the input signal while the injection-locking is taking place.…”

“…The lack of tuning presents a potential problem in a practical context, especially for sub-harmonic injection locked oscillators such as [3], where the oscillator is locked to a harmonic of the input signal. In this case, the need to achieve an adequate injection power level such that injection-locking is maintained across thermal variations will potentially undermine the ability to achieve a low power implementation.…”

“…However, in each of these cases, the injected oscillator is not continuously tuned to the input signal while the injection-locking is taking place. Instead, the tuning voltage is either kept constant [1], adjusted according to a replica VCO in a PLL [2], or initially tuned to bring the natural frequency of the oscillator to a value close to the desired multiple of the injection frequency before injecting the signal into the oscillator with enough power to ensure locking [3].…”

A 20kHz frequency resolution DCO

“…Second, the low phase noise VCO is eliminated as the phase noise will be determined by the clock PLL, which allows a significant reduction in the VCO power consumption [23].…”