Reflective array antenna

About: Reflective array antenna is a research topic. Over the lifetime, 4366 publications have been published within this topic receiving 57884 citations.

Closed-form approximations for link loss in a UWB radio system using small antennas

Abstract: A critical need in the evaluation of an ultrawideband (UWB) radio system is the calculation of the energy link loss between the source at the transmit antenna and the receiver load. While the rigorous calculation of link loss in a wideband pulsed system requires a full transient electromagnetic solution for the transmit and receive antennas, we show in this paper that accurate approximations for link loss can be obtained for the special cases of electrically small dipole or loop antennas, with Gaussian or Gaussian doublet (monocycle) generator waveforms. We also consider the error involved with applying the much simpler narrowband Friis transmission formula. It is found that the use of the basic Friis formula can result in link loss errors of more than 60 dB for a UWB system having severely (impedance) mismatched antennas, but may give results correct to within a few dB for well-matched narrowband antennas, or if the formula is augmented with an impedance mismatch correction factor. It appears that the dominant limitation of the Friis formula, when applied to UWB systems, is the broadband effect of mismatch between the transmit/receive antennas and their source or load impedances. Numerical examples are presented for electrically short dipoles, resonant dipoles, and broadband lossy dipoles for both Gaussian and monocycle input pulse waveforms.

Miniature tv antenna

Abstract: An antenna for TV reception predominantly in the low band and high band VHF ranges having dipoles of significantly reduced physical length as compared with conventional dipoles for reception of signals respectively in the low and high band VHF ranges. Inductive elements are employed to form a portion of the dipole length to permit significant reduction in the physical length of the dipole. The dipoles are electrically isolated from one another by suitable trap circuits to isolate high band VHF operation from low band VHF operation. Lossy components are deliberately added to the dipole section of the antenna to provide significantly improved noise matching and power transfer between antenna and amplifier. The inductive elements further provide good impedance matching between antenna and amplifier to optimize power transfer. The antenna is provided with end loads of the capacitive-type for improving both current magnitude and current distribution across the dipole in both low band and high band VHF operation. Separate amplifier channels are provided for low band and high band VHF signals to improve gain and reduce intermodulation and cross modulation effects, among other. A passive UHF section may be integrated into the array.

Evaluation of adaptive phased array antenna, far-field nulling performance in the near-field region

Abstract: A theory for analyzing the behavior of adaptive phased array antennas illuminated by a near-field interference test source is presented. Conventional phased array near-field focusing is used to produce an equivalent far-field antenna pattern at a range distance of one to two aperture diameters from the adaptive antenna under test. The antenna is assumed to be a linear array of isotropic receive elements. The interferer is assumed to be a bandlimited noise source radiating from an isotropic antenna. The theory is developed for both partially and fully adaptive arrays. Results are presented for the fully adaptive array case with single and multiple interferers. The results indicate that near-field and far-field adaptive nulling can be equivalent. The adaptive nulling characteristics studied in detail are the array radiation patterns, adaptive cancellation, covariance matrix eigenvalues, and adaptive array weights. >

Highly Directional Steerable Antennas: High-Gain Antennas Supporting User Mobility or Beam Switching for Reconfigurable Backhauling

Abstract: Modern millimeter-wave (mmWave) communication systems for large indoor areas and most outdoor scenarios require high-gain antennas with beam-steering ability to support user mobility or beam switching for reconfigurable backhauling. In this article, two new concepts for the development of highly directional steerable mmWave antennas are proposed and analyzed. The first one is modular antenna array (MAA) technology, which allows the creation of large-aperture, high-gain adaptive antenna arrays in a cost-effective and scalable manner. Two MAA configurations based on the existing phased subarray module are considered and analyzed for mmWave small-cell access and backhauling. The second prospective technology that fulfills the required antenna parameters for mmWave smallcell flexible backhauling is the lens-array antenna (LAA). The combination of the dielectric lens for aperture increasing with only one subarray module with beam-steering capabilities may provide 25?30-dBi total antenna gain with azimuth sector sweeping !45?.

Missile base mounted microstrip antennas

Abstract: Proof of the feasibility of aft mounting low-profile antennas on reentry vehicles is presented. This is an application of state of the art antenna hardware. Aft mounting presents the best reentry environment to antenna hardware, and its practicality has been demonstrated. Microstrip antenna principles can be used to produce very rugged antennas. Their low profile reduces many interface, mechanical, and survival problems. The pattern coverage for these vehicles must be toward the fore direction. This type of pattern requires an interaction between the vehicle and the antenna when the antenna is effectively shadowed from that direction. This paper describes the results obtained by actual experimental hardware. Contoured elements were used, as were foreshortened elements. These elements demonstrated ability to be fit around other aft equipment. The versatility of these elements were further demonstrated by tailoring them for two different types of coverage to accommodate different vehicle operational requirements.