Abstract: A system for subsurface transmission includes an array of very low frequency (VLF) transmitter nodes supported by semi-autonomous maritime, airborne, or space platforms spaced at regular intervals from their nearest neighbors and phased to localize VLF coverage to some desired area on a body of water.

Abstract: A system for subsurface transmission includes an array of very low frequency (VLF) transmitter nodes supported by semi-autonomous maritime, airborne, or space platforms spaced at regular intervals from their nearest neighbors and phased to localize VLF coverage to some desired area on a body of water.

Abstract: An active biconical antenna and a receive array comprising a combination of active biconical and Vivaldi antennas. In one configuration, the active biconical antenna includes upper and lower cones. Each cone has a respective truncated apex. First and second feed points are respectively connected to the truncated apexes of the upper and lower cones and to first and second conductors. The active biconical antenna further includes a buffer amplifier having respective input terminals connected to the first and second conductors. The buffer amplifier has an input impedance that is impedance matched to an antenna impedance at and above but not below a frequency fc and is higher than the antenna impedance at frequencies substantially less than fc. The buffer amplifier also has an output impedance that is impedance matched to a system impedance at frequencies both above and below fc. A length of the first and second conductors is less than a wavelength at the frequency fc.

Abstract: An active biconical antenna and a receive array comprising a combination of active biconical and Vivaldi antennas. In one configuration, the active biconical antenna includes upper and lower cones. Each cone has a respective truncated apex. First and second feed points are respectively connected to the truncated apexes of the upper and lower cones and to first and second conductors. The active biconical antenna further includes a buffer amplifier having respective input terminals connected to the first and second conductors. The buffer amplifier has an input impedance that is impedance matched to an antenna impedance at and above but not below a frequency fc and is higher than the antenna impedance at frequencies substantially less than fc. The buffer amplifier also has an output impedance that is impedance matched to a system impedance at frequencies both above and below fc. A length of the first and second conductors is less than a wavelength at the frequency fc.

Abstract: An array of preferably electrically small scatterers is spaced at more or less regular intervals from a central transmitter. Each scatterer element includes a tunable or static reactive load which allows the propagation and fields generated by the central transmitter to be precisely controlled. Each scatterer element in the array also includes a resistive element whose value may change as a function of a distance between each scatterer and the central transmitter and which typically increases as a function of that distance. The central transmitter in the array nominally comprises an antenna, matching network, RF driver, and a vehicle, which may be a maritime vehicle or platform. The antenna for this transmitter may be comprised of an electrically small monopole oriented normal to the surface of the ocean or an electrically small loop antenna oriented with its magnetic moment parallel to the surface of the ocean.

Abstract: An energy conversion device disposed in series with an RF driver circuit and an RF antenna, the energy conversion device being arranged to convert a portion of available RF power from the RF driver circuit into a different form of energy (direct current, thermal, or higher frequency electromagnetic waves such as light) which is converted, if needed, to DC and stored in an energy storage device coupled with the RF driver circuit for supplying recycled electrical energy thereto. The RF antenna may be an electrically small antenna and thus a antenna matching network may be provided between the RF driver circuit and the RF antenna. The energy conversion device may comprise, for example, (i) a transformer in combination with a rectifying circuit, (ii) a full wave rectifier, (iii) a half wave rectifier, (iv) a heat and/or light producing device, an energy converter (such as a generator) or a combination of the foregoing.

Abstract: A system for an antenna for very low frequency communication includes a surface platform that is configured to move on a surface or to be stationary on the surface, a first conductive cable having a first end coupled to the surface platform, wherein the first conductive cable is electrically conductive, and an aerial platform coupled to a second end of the first conductive cable, wherein the aerial platform comprises an electrically conductive portion electrically coupled to the first conductive cable, wherein for a moving surface platform the aerial platform is towed and has an elevation above the surface, and wherein for a stationary surface platform the aerial platform flies an orbital path above the surface platform.

Abstract: A system for subsurface transmission includes an array of very low frequency (VLF) transmitter nodes supported by semi-autonomous maritime, airborne, or space platforms spaced at regular intervals from their nearest neighbors and phased to localize VLF coverage to some desired area on a body of water.

Abstract: A distributed transmitter antenna includes a plurality of antenna segments and a plurality of transmitters. A first transmitter of the plurality of transmitters is coupled to a first antenna segment of the plurality of antenna segments, and a second transmitter of the plurality of transmitters is coupled to the first antenna segment and a second antenna segment of the plurality of antenna segments.

Abstract: An antenna system having a Vivaldi antenna configured to be impedance matched to antenna impedance Za at and above but not below a frequency fc; a Field-Effect-Transistor buffer coupled to the Vivaldi antenna, the length of the coupling between the antenna terminals and the buffer being of a distance much less than a wavelength at frequency fc, the buffer configured to present a high impedance at frequencies substantially <fc, the buffer output impedance further configured to be matched to a system impedance Z0 at frequencies both above and below fc.

Abstract: An antenna system having at least one active element with a first end thereof for connection to a radio receiver, transmitter or transceiver and at least one electromechanical resonator connected in series with (i) at least portion of said at least one active element and at least another portion of said at least one active element or (ii) said at least one active element and said radio receiver, transmitter or transceiver. The at least one active element exhibits capacitive reactance at an intended frequency of operation and the at least one electromechanical resonator exhibits inductive reactance at the intended frequency of operation, the inductive reactance of the at least one electromechanical resonator offsetting or partially offsetting the capacitive reactance of the at least one antenna element at the intended frequency of operation.

Abstract: A holographic antenna including a transmission line structure having a traveling wave mode along a length of the transmission line structure, and a plurality of reconfigurable radiating elements located along the length of the transmission line structure.

Abstract: A system and method for a dual-polarized active artificial magnetic conductor (AAMC) is presented in this disclosure. An embodiment of the proposed system comprises an array of unit cells that reflects electromagnetic waves polarized parallel to a surface with a zero-degree phase shift. The array of unit cells has impedance elements connected to neighboring impedance elements with non-Foster circuits coupled in a crossover configuration, each impedance element being coupled to a ground with a conductive via.

Abstract: A wideband active antenna system comprising an antenna having N outputs and a nominal bandwidth, each of the N outputs being directly coupled to an associated buffer amplifier, with a distance between the N outputs and a first active stage of each associated buffer amplifier preferably being maintained as short as reasonably possible and preferably no greater than ¼ wavelength of any transmission and/or receiving frequency of the wideband active antenna system and/or preferably no greater than 0.1 wavelength of any transmission and/or receiving frequency in an extension band of frequencies lower than a lowest frequency in the nominal bandwidth of the antenna.

Abstract: A phased array that comprises a predetermined number of emitter/receiver elements; said emitter/receiver elements being arranged on a array formed of stacked rows, wherein the emitter/receiver elements in each row of the array are distributed according to a pseudo-random pattern; and the heights of the rows vary according to a pseudo-random pattern.

Abstract: An antenna system having a Vivaldi antenna configured to be impedance matched to antenna impedance Za at and above but not below a frequency fc; a Field-Effect-Transistor buffer coupled to the Vivaldi antenna, the length of the coupling between the antenna terminals and the buffer being of a distance much less than a wavelength at frequency fc, the buffer configured to present a high impedance at frequencies substantially <fc, the buffer output impedance further configured to be matched to a system impedance Z0 at frequencies both above and below fc.

Abstract: A wideband active antenna system comprising an antenna having N outputs and a nominal bandwidth, each of the N outputs being directly coupled to an associated buffer amplifier, with a distance between the N outputs and a first active stage of each associated buffer amplifier preferably being maintained as short as reasonably possible and preferably no greater than ¼ wavelength of any transmission and/or receiving frequency of the wideband active antenna system and/or preferably no greater than 0.1 wavelength of any transmission and/or receiving frequency in an extension band of frequencies lower than a lowest frequency in the nominal bandwidth of the antenna.

Abstract: A holographic antenna including a transmission line structure having a traveling wave mode along a length of the transmission line structure, and a plurality of reconfigurable radiating elements located along the length of the transmission line structure.

Abstract: In examples, systems and methods for increasing the performance of electrically-small antennas are described. An example system comprises an electrically-small antenna having an antenna feed. The electrically-small antenna is configured to receive a signal. The system also comprises a non-foster circuit having a negative capacitance coupled to the antenna feed in a shunt position. The non-foster circuit is configured to resonate the electrically-small antenna and provide a voltage increase to the received signal. The system also comprises a buffer circuit configured to provide an impedance conversion of the voltage-increased received signal between the antenna feed and an output of the buffer circuit. The buffer circuit includes a field-effect transistor.

Abstract: An antenna array containing two or more radiating elements, with nearest neighbor radiating elements connected together with a non-Foster circuit at terminals of the radiating elements such that mutual reactance of the elements is reduced over a wider bandwidth than which would be obtained if the non-Foster circuits were omitted.