CrossAxis Coupling Effects in SingleAxis Nuclear Magnetic Resonance Gyroscopes Nuclear magnetic resonance gyroscopes (NMRGs) may be operated in an environment with violent vibration that usually contains both linear components and angular components. To analyze the influence of angular vibration on an NMRG, crossaxis coupling effects are studied. The crossaxis rotation rates induce an equivalent magnetic field. Its influence can be described by the Bloch equations. The approximate frequency shift and amplitude of the spin oscillator with an equivalent magnetic field in the crossaxis were obtained, which was validated by numerical simulation. The findings show that the angular vibration component leads to a remarkable error for the NMRG. When the angular vibration frequency is near the Larmor frequency, the oscillation frequency of the spins may be locked to the angular vibration frequency, destroying the NMRGxe2x80x99s ability to measure rotation rates. The crossaxis coupling problem should be considered in the design of an NMRG and corresponding inertial navigation systems.

Injection locking in selfoscillating magnetometers Injection locking (IL) is a wellknown phenomenon that occurs in nonlinear oscillators subject to external periodic or nonperiodic signals. It is a phenomenon of induced synchronization that occurs when an external (injection) signal locks the frequency of the oscillator to the frequency of the external signal. This form of synchronization is relatively straightforward to implement because it does not require specially organized feedback as is the case with phase locked loop. Circuits that exploit IL can have very simple designs and be applied to a broad range of applications, such as to synchronize frames and lines in early television sets, to synchronize lasers, and to function as ac voltmeters, fieldintensity meters, amplifierlimiters and AM and FM detectors. However, the focus of this article is the recent application of IL to magnetic field sensors. This novel application highlights the potential benefits of the IL approach but also some of the complexities and opportunities for further development. As with all measurement systems, the consideration of noise is paramount in the design of magnetic sensors. Noise reduction and mitigation strategies are essential. IL can be employed as a noise mitigation strategy in magnetometers that utilize selfoscillations as part of their detection paradigm; it can stabilize the oscillation frequency, potentially simplifying the measurement circuitry, and in some circumstances improve the signaltonoise ratio. Here we review some magnetometers that have successfully exploited IL principles and highlight design options. We also propose a new circuit that is simple to implement and more straightforward to analyze.