Abstract: An exemplary radio-based navigation system uses a small multimode direction-finding antenna and a direction-finding receiver capable of determining platform position, velocity, attitude, and time while simultaneously providing protection against narrowband and broadband sources of interference. Global Navigation Satellite System (GNSS) signals such as those from the Global Positioning System (GPS) provide attitude measurements with a compact multimode direction-finding antenna (e.g., a small two-arm spiral with improved angle-of-arrival performance over the entire hemisphere enhanced through the use of a conductive vertical extension of the antenna ground plane about the antenna perimeter and/or conductive posts placed evenly around the antenna perimeter) which provides simultaneous protection against jammers. The multimode spiral may be treated as an array of rotationally-symmetric antenna elements.

Abstract: An electrically tilted antenna system with polarization diversity has a dual polarized, tilt adjustable antenna (32). The antenna (32) has dipoles (34, 36) of two orthogonal polarizations associated with independently adjustable electrical tilt angles. The tilt angles are implemented by relative delays between corporate feed input or output signals, the delays being introduced by an antenna tilt assembly (54). Two signal feeders (F21, F22) associated with different antenna polarizations connect the antenna tilt assembly (54) to a base station filter assembly (50): the base station filter assembly 50 routes transmit signals from base stations (BS21, BS22) to different antenna polarizations via respective feeders (F21, F22) and the antenna tilt assembly (54). This assembly also divides receive signals from feeders (F21, F22) between both base stations (BS21, BS22).

Abstract: Disclosed is an Radio Frequency (RF) volumetric direction finding (DF) methodology, utilizing an Half Maxwell Fish-eye (HMFE) Lens having a semi-spherical shape, a focal plane with a feed structure composed of near-equally spaced frequency-independent antenna elements disposed uniformly to form a 2-dimentional feed array; and RF power splitters for each element and combiners for combining the RF energy received by the elements; forming rows and columns; thereby reducing the number of required RF receiver channels for subsequent processing, where the maximum row/column and differential amplitude comparison is used for deriving DF estimation of intercepted signals; as part of a robust signal detection and direction-finding (DF) system; for detecting and processing a plurality of signals emanating from navigation, radar and communication equipment on surface and airborne platforms.

Abstract: Disclosed is an Radio Frequency (RF) receiving system methodology, utilizing an Luneberg Lens having a spherically shaped outer surface and a semi-spherical shaped focal surface composed of near-equally spaced frequency-independent antenna elements disposed uniformly to cover the semi-spherical focal surface of the Luneberg Lens; and radio frequency (RF) power splitters and combiners for combining the RF energy received by the antenna elements; forming rows and columns; thereby reducing the number of required RF receiver channels for subsequent processing, where the maximum row/column and differential amplitude comparison is used for deriving volumetric direction finding (DF) of intercepted signals; as part of a robust signal detection and direction-finding (DF) system; for detecting and processing a plurality of signals emanating from surface and airborne platforms within the hemisphere, where each surface and airborne platform include transmitters for transmitting navigation, communication and radar signals

Abstract: An exemplary radio-based navigation system uses a small multimode direction-finding antenna and a direction-finding receiver capable of determining platform position, velocity, attitude, and time while simultaneously providing protection against narrowband and broadband sources of interference. Global Navigation Satellite System (GNSS) signals such as those from the Global Positioning System (GPS) provide attitude measurements with a compact multimode direction-finding antenna (e.g., a small two-arm spiral with improved angle-of-arrival performance over the entire hemisphere enhanced through the use of a conductive vertical extension of the antenna ground plane about the antenna perimeter and/or conductive posts placed evenly around the antenna perimeter) which provides simultaneous protection against jammers. The multimode spiral may be treated as an array of rotationally-symmetric antenna elements.

Abstract: A hybrid wireless network system is disclosed. The hybrid wireless network system includes an antenna array, an analog subsystem, and a digital subsystem. The antenna array at least includes two antenna elements. In the case of using multiple antenna elements to extend link range and coverage, a coarse-fine method is included for antenna elements selection. The analog subsystem calculates a difference signal and a sum signal based on the two RF signals. The analog subsystem includes step leveling devices. The digital subsystem estimates a direction-of-arrival (DOA) based on the sum signal and the difference signal. The step-leveling devices receive weights from the digital subsystem, in form of a feedback control, to apply the weights on the two RF signals respectively. The digital subsystem repetitively calculates new weights to update a beam pattern formed by the two RF signals until the DOA approaches null.

Abstract: An exemplary radio-based navigation system uses a single-aperture multimode direction-finding antenna capable of determining platform position, velocity, attitude, and time while simultaneously providing protection against narrowband and broadband sources of interference. Global Navigation Satellite System (GNSS)-signals such as those from the Global Positioning System (GPS) provide protection against jammers while simultaneously providing attitude measurements with a compact single-aperture multimode antenna (e.g., a small two-arm spiral with improved angle-of-arrival performance over the entire hemisphere enhanced through the use of a conductive vertical extension of the antenna ground plane about the antenna perimeter and/or conductive posts placed evenly around the antenna perimeter). The multimode spiral may be treated as an array of cylindrically symmetric antenna elements.