Abstract: Low-protrusion array antennas enable reception of satellite signals by airliners in flight. Prior systems using a beam normal to an array face required a 70° array tilt for reception from a satellite at 20° elevation (i.e., tilt angle is complementary angle (90°−&bgr;) of satellite angle (&bgr;) of elevation). Compared to that 70° array tilt for reception from a satellite at 20° elevation, disclosed antennas require an array tilt of only 25° (90°−&bgr;−&agr;=25°). This is accomplished by providing a beam at a fixed acute angle (&agr;) to the array face (e.g. 45 degrees). A side-by-side linear array 16 of slotted waveguide radiator columns 18 provides a pencil beam at a fixed acute angle of 45° to array aperture, for example. By action of tilting motor 42 to mechanically tilt the array of slotted waveguides over a range of ±25° from horizontal, the beam can be scanned from 20° elevation to 70° elevation.

Abstract: Synthesizer radiating systems provide efficient wideband operation with an antenna, such as a loop, which is small relative to operating wavelength. Energy dissipation is substantially reduced by cycling energy back and forth between a high-Q radiator and a storage capacitor. Wideband operation is achieved by actively controlling power switch devices. Dissipation is further reduced during high speed switching by use of sequential switching methods to avoid dissipation of energy capacitively stored in switch capacitances, including switch control circuit capacitance. Systems using multi-segment loop antennas are arranged to match antenna input impedance to switching circuit parameters. Personal transmit/receive systems mounted on a jacket or other clothing for field use are enabled.

Abstract: A dual-radiator whip antenna to operate over a 30 to 450 MHz frequency band includes a high frequency dipole above a low frequency monopole. The outer conductor (30) of a coaxial line is configured to operate as a monopole. Above the upper terminus of the outer conductor, an extension (32a) of the inner conductor (32) is configured as the upper arm of a dipole. An upper length of the outer conductor also functions as the lower dipole arm. With a single antenna port (13), a diplexer and other feed elements separate signals into high and low frequency bands respectively coupled to the dipole and monopole radiators. Increased high frequency range results from positioning of the center of radiation of the dipole above the monopole.

Abstract: A self-contained four-dipole element provides a 360 degree phase-progressive-omnidirectional (PPO) circularly polarized antenna pattern. Via a single signal port, a PPO excitation network incorporated into the element excites the four dipoles at phases differing by successive 90 degree increments. The four-dipole element is adapted for efficiently reproducible fabrication using printed circuit techniques. Antennas employing a stack of the elements provide a hemispherical antenna pattern with PPO circular polarization and a sharp cutoff below horizontal. For GPS reception in Differential GPS aircraft landing applications, a 21 element antenna provides multipath suppression and a unitary phase center enabling avoidance of signal phase discrepancies. More or fewer elements may be employed in other applications.