Abstract: A broadband antenna includes a first antenna element having first and second ends spaced apart by a surface thereof. A second antenna element is substantially co-planar with the first antenna element, the second antenna element having first and second ends spaced apart by a surface thereof. The first end of the second antenna element is spaced apart from the second end of the first antenna element by a first air gap. A conductive structure is spaced apart from the first end of the first antenna element by a second air gap, the conductive structure being configured to provide for structural excitation of the antenna over a lower frequency range of an available broadband antenna bandwidth, such as may be a continuous operating bandwidth.

Abstract: A broadband antenna includes a first antenna element having first and second ends spaced apart by a surface thereof. A second antenna element is substantially co-planar with the first antenna element, the second antenna element having first and second ends spaced apart by a surface thereof. The first end of the second antenna element is spaced apart from the second end of the first antenna clement by a first air gap.

Abstract: A phased array antenna (12) that includes a plurality of multiple spiral arm antenna elements (10). The antenna elements (10) are hexagonal in shape and are aligned in a triangular lattice geometry, where the elements (10) are arranged in rings around a common center element (32). The elements (10) include at least two arms (18, 20) which terminate at opposite sides of the element (10). The ends (26, 28) of the arms (18, 20) of diagonally adjacent elements (10) are positioned proximate to each other to provide inter-element coupling to increase the bandwidth of the antenna (12). The tight coupling of the antenna elements (10) also reduces the RCS of the antenna (12).

Abstract: A compliant RF feed system (10) that provides impedance matching for VHF/AM, VHF/FM, UHF and L-band frequencies. The feed system (70) includes a feed post (14) electrically connected to an antenna element (18) at one end and a matching circuit package (22) at an opposite end, where the feed post (14) extends across a non-conductive gap (16) between the antenna element (18) and a conductive aircraft component (20). The matching package (22) includes a compressible bellows (38) mounted in the package (22), where the feed post (14) contacts the bellows (38) in a compression engagement to provide an electrical connection between the feed post (14) and a RF matching circuit (24) in the matching package (22). An impedance transformer (40) is provided in the matching package (22) to match the impedance of the bellows (38) to the matching circuit (24). The bellows (38) allows the electrical connection between the antenna element (18) and the aircraft component (20) to accommodate vibrations during aircraft operation.

Abstract: A multifunction antenna feed structure (30) that acts as a feed for a multibandwidth antenna system (22) used in connection with a modern tactical aircraft. The feed structure (30) includes a first feed (32) and a second feed (34) electrically connected to first and second feed points on an antenna element (24) at a location where the first feed (32) is impedance matched to the VHF/FM and UHF frequency bands and the second feed (34) is impedance matched to the VHF/AM frequency band. The first and second feeds (32, 34) are positioned within a flared notch (28) between the antenna element (24) and a conductive aircraft structural component (26). The feeds (32, 34) can take on different geometrical configurations, such as cylindrical feeds, cone feeds or taper feeds. The feeds are (32, 34) electrically isolated from conductive aircraft component (26) and are electrically connected to a matching network (70, 80).

Abstract: A wide band, single aperture antenna system (70) that provides simultaneous detection of both RHCP and LHCP signals. The antenna system (70) includes a multiple arm spiral antenna (10) that has spiral arm elements (12, 14, 16, 18) with no sharp transitions. To simultaneously both RHCP and LHCP sensitivity, an antenna feed is connected to both the center end and the outer end of each of the antenna arm elements (12, 14, 16, 18). A separate N-port transformer (74, 78) is connected to both the end feed and the center feed for all of the arms (12, 14, 16, 18) to provide impedance matching and cross-polarization compensation. An NXN port modeformer (76, 80) is connected to the N-port transformers (74, 78) to separate the various modes. The modeformers (76,80) separate the LHCP and RHCP modes to provide an accurate AoA estimation.

Abstract: An antenna system structurally integrated into a load-bearing structural member of an aircraft, such as a wing (30), horizontal tail section (36), or vertical tail fin (20) in such a way as to cause practically no added aerodynamic drag and to add minimal weight to the aircraft. The antenna system includes a flared notch (22, 32, 34 or 38) of non-conductive material and an antenna feed (12) that excites conductive portions of the structural member on opposite sides of the notch at a selected feed point (40). The conductive portions of the structural member and other conductive portions of the entire aircraft are excited by signals applied to the antenna feed. As a result, the antenna performance provides high gain omnidirectionally, and supports both vertically and horizontally polarized communication functions over a wide range of VHF and UHF bands.

Abstract: The present invention provides a modeforming circuit (100). The modeforming circuit (100) includes a first matrix circuit (102) comprising an interconnected network of transmission lines (208-212) and phase shifters (216-218) that implement at least one N/2.times.N/2 identity matrix and at least one N/2.times.N/2 phase shift matrix. The first matrix circuit (102) is connected in series to a second matrix circuit (104). The second matrix circuit (104) includes an interconnected network of phase shifters that implements at least one N/2.times.N/2 phase shift matrix. The modeforming circuit (100) may further include a third matrix circuit (106) connected in series with the second matrix circuit (104). The third matrix circuit (106) includes a network of transmission lines (220-230) that reorder N inputs to N mode outputs. The first matrix circuit (102) may be implemented as a first matrix sub-circuit (108) connected in series with a second matrix sub-circuit (110) to provide even further reduced complexity.

Abstract: An implementation of a Butler matrix transformation used to process antenna signals and, in particular, to transform signals obtained from an N-port antenna into mode signals used for direction finding and other purposes. A reverse transformation is used when the antenna is operating in a transmit mode. Instead of using a single Nth order transformation matrix, the circuit of the invention employs a decomposed form of the transformation matrix, thereby reducing the complexity of the transformation by using lower-order matrices. In an example of the invention for an 8.times.8 transformation, the circuit complexity is further reduced by using an additional level of decomposition, in which phase shifting is effected by a circuit implementation of a single 8.times.8 diagonal phase shift matrix requiring only three phase shift circuits. Reduction in circuit complexity, particularly in the number of phase shift circuits, reduces bias errors in the overall transformation and reduces fabrication cost.

Abstract: A multifunction antenna system is provided which has adaptive beam forming capabilities for transmitting and receiving signals having various beam patterns over a hemispherical field of view. The antenna system includes a beamformer having an array of N spiral arm elements for transmitting and receiving a radiating beam. N analytic voltage signals are produced by the N cylindrically symmetric spiral arm elements in relation to the radiating beam. A beam processor is further provided for selecting the appropriate combination of vector weight coefficients in response to input data. The beam processor loads the selected N vector weights into a vector weighter. In the transmit mode, the vector weighter multiplies the selected vector weights by an input signal to produce the N analytic signals which are then applied to the multiple arm spiral antenna and transmitted therefrom.

Abstract: Apparatus, and a corresponding method, for generating navigational data to aid a pilot in landing or taxiing an aircraft in poor visibility conditions. Radio-frequency (rf) beacons at predetermined locations around an airport runway or taxiway are separately modulated to render them uniquely identifiable from the aircraft. A fixed array of receiving antennas on the aircraft has multiple, angularly spaced antenna beams that substantially overlap each other in coverage, such that a signal received from one of the beacons will in most cases be received in more than one adjacent receive beam. Signals received in each beam are processed by a fast Fourier transform module to separate signal components from the various beacons; then an interpolation process determines the arrival angles of the signals by comparing the amplitudes received in adjacent receive beams.