Passive electronically scanned array

Abstract: Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, holographic rendering can be achieved without cumbersome circuitry and with only a single transducer, thus significantly reducing system complexity. Such metamaterial-based holograms can serve as versatile platforms for various advanced acoustic wave manipulation and signal modulation, leading to new possibilities in acoustic sensing, energy deposition and medical diagnostic imaging.

Abstract: A plurality of transmitting (14, 16, 18, 20) and receiving antenna elements (22, 24, 26, 28) are formed on a support member (12) which may be mounted on a corner of a vehicle for scanning a pattern including areas on opposite sides of the vehicle corner In an automotive application, the pattern may include a rear area, and a blind spot on the side of the vehicle adjacent to the rear area A transmitter (50) is connected to the transmitting antenna elements (14, 16, 18, 20) by a passive phased array (30) such as a planar microstrip Butler matrix, and an electronic switch (52) which sequentially connects the transmitter (50) to inputs of the transmitting array (30) A receiver (62) is similarly connected to the receiving antenna elements (22, 24, 26, 28) by a planar microstrip passive phased array (40), and an electronic switch (64) which sequentially connects the receiver (62) to outputs of the receiving array (40) The support member (12) may be formed into a non-planar shape, or be flexible enough to be bent into a non-planar shape, to conform to a non-planar surface of the vehicle on which the sensor is to be mounted

Abstract: The metascreen-based acoustic passive phased array provides a new degree of freedom for manipulating acoustic waves due to their fascinating properties, such as a fully shifting phase, keeping impedance matching, and holding subwavelength spatial resolution. We develop acoustic theories to analyze the transmission/reflection spectra and the refracted pressure fields of a metascreen composed of elements with four Helmholtz resonators (HRs) in series and a straight pipe. We find that these properties are also valid under oblique incidence with large angles, with the underlying physics stemming from the hybrid resonances between the HRs and the straight pipe. By imposing the desired phase profiles, the refracted fields can be tailored in an anomalous yet controllable manner. In particular, two types of negative refraction are exhibited, based on two distinct mechanisms: one is formed from classical diffraction theory and the other is dominated by the periodicity of the metascreen. Positive (normal) and negative refractions can be converted by simply changing the incident angle, with the coexistence of two types of refraction in a certain range of incident angles.

Abstract: This paper reports on the design, fabrication and characterization of a 3-D printed RF front end for a 2.45 GHz phased array unit cell. The printed unit cell, which includes a circularly-polarized dipole antenna, a miniaturized capacitive-loaded open-loop resonator filter and a 4-bit phase shifter, is fabricated using a direct digital manufacturing (DDM) approach that integrates fused deposition of thermoplastic substrates with micro-dispensing for deposition of conductive traces. The individual components are combined in a passive phased array antenna unit cell comprised of seven stacked substrate layers with seven conductor layers. The measured return loss of the unit cell is ${>}12$ dB across the 2.45 GHz ISM band and the measured gain is ${-}11$ dBi including all components. Experimental and simulation-based characterization is performed to investigate electrical properties of as-printed materials, in particular the inhomogeneity of printed thick-film conductors and substrate surface roughness. The results demonstrate the strong potential for fully-printed RF front ends for light weight, low cost, conformal and readily customized applications.