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.

Localization of Passive UHF RFID Tags Using the AoAct Transmitter Beamforming Technique

Abstract: The localization of passive ultra-high frequ- ency (UHF) radio frequency identification (RFID) tags is an emerging technology that has reached a high level of interest in industry and research. Most solutions use classical techniques, such as the angle-of-arrival or the received-signal-strength methods. As an alternative, we present a new approach for estimating the position of a passive UHF RFID tag by using a transmitter beamforming technique that we call angle-of-activation (AoAct). It is based on manipulating the shape of the radiation pattern of the interrogator’s transmitter antenna array. By pivoting the main lobe of the pattern in the azimuth plane of the array and by utilizing the very sensitive response threshold of passive UHF RFID tags, we are able to estimate the tag direction. We use three-channel digital beamforming, where the phases and amplitudes of the antenna array’s feeding radio frequency signals are controlled by the baseband $I$ and $Q$ components of the interrogator’s transmitter signal. Our self-developed hardware pivots the main lobe of a three-element antenna array in a range of ±52° with a resolution of 0.02°. It senses the AoAct with a mean measured accuracy of 1.2° in the anechoic chamber, 1.9° in a basic multipath environment, and 2.5° in a real-world multipath environment. After estimating the AoAct of a tag from different locations, the tag position is triangulated. Experiments show that our AoAct system delivers a localization accuracy of 7 cm in a typical multipath environment.

A projection method providing low sidelobe pattern in conformal array antennas

Abstract: The authors present a novel method for the analytical determination of the amplitude distribution providing the low sidelobe pattern of conformal array antennas. The proposed projection method considers both the nonuniform element density and element patterns on the aperture. Numerical results are given as well as results of experimental verification for an X-band, half-spherical array with 60 rectangular microstrip antennas. >

Design considerations in sparse array antennas

Abstract: The design aspects concerning the sparse array antennas are discussed. Commonly, the beamwidth, the side-lobes level and the gain are the relevant features in antenna design procedures. These parameters are evaluated for different sparse topologies and generalised design relations are provided. The capabilities of sparse architectures are evaluated by comparison with uniform arrays for a similar level of performance.

Phased array antenna with coarse/fine electronic scanning for ultra-low beam granularity

Abstract: An antenna and scanning means therefor particularly useful in an aircraft landing system operating in the microwave frequency range. The antenna is of the line phased array type which includes digitally controlled phase shifters for each of the radiating elements of the array. The beam formed by the antenna is steered by incrementing the phase shift applied at each of the array radiating elements by an amount of phase which is dependent in part upon the position of the radiating element in the array. Phase increments sufficient to shift the beam position by one coarse step (0.1°) are applied to symmetrically located radiating element pairs, pair by pair, until all elements have been incremented. The beam is thereby caused to move through one coarse step in a number of fine steps equaling the number of pairs of elements in the array. An additional feature of the scanning means is the application of phase increment to the array elements in a pseudo-random sequence.

Performance of a wideband (3-14 GHz) dual-pol array

Abstract: A test array of 25/spl times/25 dual-pol flared dipoles ("bunny-ears") was built and tested. It was designed for 3-14 GHz applications with a low profile (1.2 cm thick). The egg-crate radiating aperture can be integrated with a thin radome and the multi-layer feed to form a load-bearing structure of an airborne platform. The array has an instantaneous bandwidth of 10 GHz, manifested by an impulse response with 100 ps rise time. Smooth well-behaved "active" element patterns in the E-, H-, and diagonal plane were observed. Cross-pol components were typically 30 dB below the co-pol at broadside and 20 dB on average at 60 degree off axis. Element gain over the band was measured and the data tracked fairly well with the theoretical curve defined by the element's unit area gain (4/spl pi/A//spl lambda//sup 2/).