2.8 A mixed-mode injection frequency-locked loop for self-calibration of injection locking range and phase noise in 0.13µm CMOS

Injection-locked oscillators (ILOs) are widely used to realize low-noise carrier sources, particularly at mm-Waves by leveraging harmonic injection, but only within a narrow locking range (Δf
_L
) [1]. Substantial effort has been made to improve Δf
_L
by increasing the injection current through multiport injections in open-loop architectures at the expense of a fair amount of extra power dissipation (P
_diss
) [2]. The Δf
_L
-limitation can also be mitigated by calibrating the free-running frequency (f
_osc
) of the ILO using a mixer-based closed-loop configuration, but at the expense of significant hardware complexity in the multi-frequency feedback control and substantially increased P
_diss
[3]. In the closed-loop self-calibration technique presented in this paper, the feedback signal is primarily processed in the digital domain after extracting the envelope signal bearing the frequency difference between the injection source (f
_inj
) and f
_osc
in the analog domain, resulting in a compact and power-efficient injection-frequency locked loop (IFLL) tracking the 3
^rd
-harmonic of f
_inj
over 26.5-to-29.7GHz (Δf
_L
: 11.4%) with a 2.4mW P
_diss
in the calibration circuits.