Injection locking

Injection locking is a high frequency (usually RF, but possibly microwave and optical) phenomenon where an oscillator directly synchronizes to another high frequency signal. In the case of a VCO an injection-locking signal may override its low-frequency control voltage. When accidental and degrading, it's termed unwanted injection locking. When intentionally employed, injection locking provides a means to significantly reduce power consumption and possibly reduce phase noise in comparison to other frequency synthesizer and PLL design techniques. The main trade-offs are a narrower frequency range and an increase in die-size to accommodate on-chip inductors.

Injection-locked oscillator

An injection-locked oscillator (ILO) is usually based on cross-coupled LC oscillator. It has been employed for frequency division [M. Tiebout, "A CMOS direct injection-locked oscillator topology as high-frequency low-power frequency divider," IEEE Journal of Solid-State Circuits, vol. 39, pp. 1170-1174, 2004.] or jitter reduction in PLL, with the input of pure sinusoidal waveform. It was employed in continuous mode clock and data recovery (CDR) or clock recovery to perform clock restoration from the aid of either preceding pulse generation circuit to convert non-return-to-zero (NRZ) data to pseudo-return-to-zero (PRZ) format [ M. De Matos, J. B. Begueret, H. Lapuyade, D. Belot, L. Escotte, and Y. Deval, "A 0.25um SiGe receiver front-end for 5GHz applications," SBMO/IEEE MTT-S International Conference on Microwave and Optoelectronics 2005, pp. 213-217. ] or nonideal retiming circuit residing at the transmitter side to couple the clock signal into the data. [ [54] T. Gabara, "An 0.25 μm CMOS injection locked 5.6 Gb/s clock and data recovery cell," in Symposium on Integrated Circuits and Systems Design 1999, pp. 84 - 87.] Recently, the ILO was employed for burst mode clock recovery scheme. [J. Lee and M. Liu, "A 20Gb/s burst-mode CDR circuit using injection-locking technique," in IEEE International Solid-State Circuits Conference (ISSCC), pp. 46-586, 2007.]

The operation of ILO is based on the fact that the local oscillation can be locked to the frequency and phase of external injection signal under proper conditions.

Unwanted injection locking

High-speed logic signals and their harmonics are potential threats to an oscillator. The leakage of these and other high frequency signals into an oscillator through a substrate concomitant with an unintended lock is unwanted injection locking.

Gain by injection locking

Injection locking can also provide a means of gain at a low power cost in certain applications.

=See also=
*Injection locked frequency divider
*Injection-locked PLL
*LC oscillator
*Electronic oscillator
*Burst mode clock and data recovery

=References=

Further reading

* Wolaver, Dan H. 1991. "Phase-Locked Loop Circuit Design", Prentice Hall, ISBN 0-13-662743-9, pages 95-105
*cite journal |last=Adler |first=R. |title=A study of locking phenomena in oscillators |journal=Proceedings of the IEEE |volume=61 |issue=10 |year=1973 |month=October |pages=1380-1385
*cite journal |last=Kurokawa |first=K. |title=Injection locking of microwave solid-state oscillators |journal=Proceedings of the IEEE |volume=61 |issue=10 |year=1973 |month=October |pages=1386-1410 * Lee, Thomas H. 2004. "The Design of CMOS Radio-Frequency Integrated Circuits", Cambridge, ISBN 0-521-83539-9, pages 563-566