Shape-morphing structured materials have the ability to transform a range of applications. However, their design and fabrication remain challenging due to the difficulty of controlling the underlying metric tensor in space and time. Here, we exploit a combination of multiple materials, geometry, and 4-dimensional (4D) printing to create structured heterogeneous lattices that overcome this problem. Our printable inks are composed of elastomeric matrices with tunable cross-link density and anisotropic filler that enable precise control of their elastic modulus (E) and coefficient of thermal expansion ( α ) . The inks are printed in the form of lattices with curved bilayer ribs whose geometry is individually programmed to achieve local control over the metric tensor. For independent control of extrinsic curvature, we created multiplexed bilayer ribs composed of 4 materials, which enables us to encode a wide range of 3-dimensional (3D) shape changes in response to temperature. As exemplars, we designed and printed planar lattices that morph into frequency-shifting antennae and a human face, demonstrating functionality and geometric complexity, respectively. Our inverse geometric design and multimaterial 4D printing method can be readily extended to other stimuli-responsive materials and different 2-dimensional (2D) and 3D cell designs to create scalable, reversible, shape-shifting structures with unprecedented complexity.

https://www.pnas.org/content/pnas/116/42/20856.full.pdf

Shape-shifting structured lattices via multimaterial 4D printing

Two different types of Vivaldi antenna arrays have been designed for UWB see through wall applications. The first is a 16 × 1 antipodal Vivaldi antenna covering 8-12 GHz, and the second is an 8×1 tapered slot antenna for 2-4 GHz frequency range. The array elements are optimized to have a compact size and almost constant gain with frequency. Wilkinson power dividers were designed and fabricated to compose the feed network for the Vivaldi antenna arrays. Measured results of the manufactured antipodal and tapered slot Vivaldi antenna arrays are in excellent agreement with the simulated ones, with a gain of more than 13dBi and 12 dBi respectively within their respective operating band. The first array is geared towards see through dry wall with high resolution, while the second is designed at lower frequencies to allow see through concrete wall applications. Full arrays were manufactured and connected to multi-throw switches and have been utilized as part of synthetic aperture radar.

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Design of compact vivaldi antenna arrays for uwb see through wall applications

In this letter, we present a novel printed monopole antenna for ultrawideband (UWB) applications. The proposed antenna consists of a square radiating patch with two rectangular slots and a ground plane with inverted T-shaped notch, which provides a wide usable fractional bandwidth of more than 120% (3.1212.73 GHz). The proposed antenna is simple and small in size. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range.

Small Square Monopole Antenna With Inverted T-Shaped Notch in the Ground Plane for UWB Application

A novel coplanar waveguide (CPW)-fed compact ultrawideband (UWB) microstrip antenna is proposed for ultrawideband applications. The proposed antenna posseses a method to minimize the monopole antenna by loading of inverted L-strip over the conventional monopole patch antenna to lower the height of the antenna. The ground was vertically extended toward two sides of the single radiator. Therefore, the large space around the radiator that is usually wasted can be effectively saved. The antenna is practically fabricated and simulated. Measured results show a good agreement with simulated results. The prototype with overall size of $25 \times 25 \times 1.6\ {\hbox{mm}}^3$ achieves good impedance matching, constant gain, stable radiation patterns, and constant group delay over an operating bandwidth of 2.6-13.04 GHz (10.44 GHz).

A CPW-Fed Compact UWB Microstrip Antenna

Free space optical communication

A dual band-notched printed ultrawideband monopole antenna is presented, with a modified ground plane. By using this modified element including a pair of variable L-shaped slots, cut in the ground plane, additional resonances are excited and hence the bandwidth is increased up to 130%. To generate single and dual band-notched characteristics, we use inverted U- and fork-shaped parasitic structures, respectively, instead of changing the patch or feedline shapes. By properly adjusting the dimensions of these capacitive-coupled elements, not only one or two controllable notch resonances are achieved, but also the lower-edge frequency of the band is decreased. The measured results show that the proposed dual band-notched monopole antenna offers a very wide bandwidth from 2.2 to 13.4 GHz (143%), defined by 10-dB return loss, with two notched bands, covering all the 5.2/5.8-GHz WLAN, 3.5/5.5-GHz WiMax and 4-GHz C bands. Impedance, radiation, efficiency and gain characteristics of the antenna are also discussed.

Bandwidth Enhancement of Novel Compact Single and Dual Band-Notched Printed Monopole Antenna With a Pair of L-Shaped Slots

In this letter, a novel printed monopole antenna (PMA) for ultrawideband (UWB) applications with variable frequency band-notch characteristic is presented. The proposed antenna consists of a stepped square radiating patch with two U-shaped slots and a notched ground plane with a T-shaped sleeve that provides a wide usable fractional bandwidth of more than 140% (2.8516.73 GHz). By cutting two modified U-shaped slots with variable dimensions on the radiating patch, frequency band-stop performance is generated, and we can control its characteristics such as band-notch frequency and its bandwidth. The designed antenna has a small size of 12 times 19 mm2 while showing the band rejection performance in the frequency band of 5.02-5.97 GHz.

Small Square Monopole Antenna for UWB Applications With Variable Frequency Band-Notch Function

This paper presents a novel modified Printed Tapered Monopole Antenna (PTMA) for ultra wideband (UWB) wireless communication applications. The proposed antenna consists of a truncated ground plane and two-tapered radiating patch separated by a slot (air gap) of different slopes, which provides a wideband behavior and relatively good matching. Moreover, the effects of a modified T-shaped slot inserted in the first tapered patch, on the impedance matching is investigated. The antenna has a small area of 23 × 26.5 mm2 and offers an impedance bandwidth as high as 100% at a centre frequency of 7.2 GHz for S11 < −10 dB, which has an area reduction of 15% and a frequency bandwidth increment of 72% with respect to the previous similar antenna. The presented antenna covers the 5.2/5.8 GHz WLAN and 5.5 GHz WIMAX operating bands. Numerical analysis using Ansoft HFSS and measurement results is also presented in the paper.

/pdf/a-modified-microstrip-fed-two-step-tapered-monopole-antenna-44rlfyye1w.pdf

A Modified Microstrip-Fed Two-Step Tapered Monopole Antenna for UWB and WLAN Applications

A novel modified microstrip-fed ultrawideband (UWB) planar monopole antenna with variable frequency band-notch characteristic is presented. By inserting two slots in the both sides of microstrip feedline on the ground plane, much wider impedance bandwidth can be produced. A modified H-shaped conductor-backed plane with variable dimensions is used in order to generate the frequency band-stop performance and control its characteristics such as band-notch frequency and its bandwidth. The designed antenna has a small size of 22 x 22 mm2 and operates over the frequency band between 3.1 and 14 GHz for VSWR < 2 while showing the band rejection performance in the frequency band of 5.1 to 5.9 GHz.

Changiz Ghobadi

Papers

Small Square Monopole Antenna With Inverted T-Shaped Notch in the Ground Plane for UWB Application

Bandwidth Enhancement of Novel Compact Single and Dual Band-Notched Printed Monopole Antenna With a Pair of L-Shaped Slots

Small Square Monopole Antenna for UWB Applications With Variable Frequency Band-Notch Function

A Modified Microstrip-Fed Two-Step Tapered Monopole Antenna for UWB and WLAN Applications

Novel Modified UWB Planar Monopole Antenna With Variable Frequency Band-Notch Function