Abstract: A method and apparatus for measuring electrical or magnetic fields, such as high-frequency alternating fields in a nuclear magnetic resonance tomography device, convert a test signal into a corresponding ultrasound signal, and transmit the ultrasound signal to a receiver, where the received signal is converted back into an electrical signal. The transmission path contains no metallic components and thus does not cause any disturbance in the field being measured.

Abstract: A surface resonator for use in nuclear magnetic resonance tomography is a single turn loop of ribbon-like electrical conductor having spaced ends facing each other which form a capacitor whose capacitance determines the resonant frequency. The loop of ribbon-like conductor is shaped to conform substantially to the generated surface of a truncated cone. The ends of the loop may be in the form of spaced plates for providing the necessary capacitance, or may be connected by one or more discrete component capacitors.

Abstract: An antenna structure for exciting a substantially homogeneous magnetic RF field and/or for receiving RF signals in a nuclear magnetic resonance tomography apparatus includes a hollow cylindrical conductor sheath which is substantially transmissive at low frequencies for gradient magnetic fields, a number of conductor units within the conductor sheath, each conductor unit including at least one conductor element, and RF reflector disposed at the end faces of the antenna structure and an external energy feed or reception device. In this antenna structure, the current drop which increasingly occurs toward the end faces of the antenna structure is largely compensatable by shaping the electrically conductive cross-section of the conductor units so as to decrease symmetrically from an axial center of the antenna structure moving toward the end faces of the structure. The conductor units thus have a largest cross-section at a center of the antenna structure, and a smallest cross-section at the end faces.