Coil noise

About: Coil noise is a research topic. Over the lifetime, 3174 publications have been published within this topic receiving 45337 citations.

Spiral scanner with electronic control

Abstract: A scanning device, typically ultrasonic, can make a volumetric scan of a conical scanning field. A transducer having a permanent magnet at its back end is gimbal mounted in a housing. Behind the permanent magnet is a hemispheric electromagnet coil assembly having at least two wound electromagnet coils. The coils are energized in turn with an alternating current signal, with the signal applied to any coil being out of phase with the signal applied to any other coil by 180°/n, where n is the number of coils in the hemispheric electromagnet coil assembly. Volumetric scanning is possible by periodically modulating the magnitude or frequency of the signals applied to the coils.

Transponder with overlapping coil antennas on a common core

Abstract: A wireless device includes an antenna assembly, including a core and one or more power coils, wound around the core on respective power coil axes, including at least a first power coil having a first power coil axis. One or more signal coils are wound around the core on respective signal coil axes, including at least a first signal coil wound so as to overlap the first power coil, the first signal coil having a first signal coil axis that is substantially parallel to the first power coil axis. Power circuitry is coupled to the power coils so as to receive therefrom first radio signals in a first frequency band, and to rectify the first radio signals so as to generate a direct current. Communication circuitry, powered by the direct current, is coupled to perform at least one of transmitting and receiving second radio signals in a second frequency band via the signal coils.

Induction coil sensors—a review

Abstract: This review describes induction coil sensors, which are also known as search coils, pickup coils or magnetic loop sensors. The design methods for coils with air and ferromagnetic cores are compared and summarized. The frequency properties of coil sensors are analysed and various methods for output signal processing are presented. Special kinds of induction sensors, such as Rogowski coil, gradiometer sensors, vibrating coil sensors, tangential field sensors and needle probes are described. The applications of coil sensors as magnetic antennae are also presented.

B(1) destructive interferences and spatial phase patterns at 7 T with a head transceiver array coil.

Abstract: RF behavior in the human head becomes complex at ultrahigh magnetic fields. A bright center and a weak periphery are observed in images obtained with volume coils, while surface coils provide strong signal in the periphery. Intensity patterns reported with volume coils are often loosely referred to as "dielectric resonances," while modeling studies ascribe them to superposition of traveling waves greatly dampened in lossy brain tissues, raising questions regarding the usage of this term. Here we address this question experimentally, taking full advantage of a transceiver coil array that was used in volume transmit mode, multiple receiver mode, or single transmit surface coil mode. We demonstrate with an appropriately conductive sphere phantom that destructive interferences are responsible for a weak B(1) in the periphery, without a significant standing wave pattern. The relative spatial phase of receive and transmit B(1) proved remarkably similar for the different coil elements, although with opposite rotational direction. Additional simulation data closely matched our phantom results. In the human brain the phase patterns were more complex but still exhibited similarities between coil elements. Our results suggest that measuring spatial B(1) phase could help, within an MR session, to perform RF shimming in order to obtain more homogeneous B(1) in user-defined areas of the brain.