Edward A. Parker

Cylindrical Slot FSS Configuration for Beam-Switching Applications

A novel design for a beam-switching antenna using active cylindrical slot frequency selective surface (ACSFSS) is presented. The antenna system is composed of an omnidirectional monopole antenna and the ACSFSS, which employs a new technique of switching slot arrays. The ACSFSS is made up of 12 columns with 8 slots each, dividing the cylinder by 30°. To steer the beam of the antenna the diodes are set off and on, so that the radiation pattern of the antenna is determined by the number of off state columns. To estimate the general dimension of the cylindrical FSS, an equivalent metallic reflector is introduced and optimized, and then parametric studies for the unit cell dimensions are discussed. The fabricated prototype works within the WLAN band, centered around 2.45 GHz, and can agilely select either a narrow-beam or wide-beam operating mode. Simulation and measurements confirm the operation of the ACSFSS antenna, with good matching and gain observed. In particular, the narrow-beam mode -3 dB beamwidth is 47° which offers enhanced angular resolution compared with other reported beam-sweeping work.

An active square loop frequency selective surface

An active frequency selective surface incorporating PIN diodes as switches is discussed. Waveguide simulation studies show that the frequency response of the surface can be electronically switched from that of a reflecting structure to a transmitting structure. A semi-empirical model based on a series-connected LC equivalent circuit approach gives agreement with measurements.<<ETX>>

Singly and Dual Polarized Convoluted Frequency Selective Structures

Convoluting the elements of frequency selective surfaces produces resonating structures with very small unit cell dimensions. This feature is attractive when the FSS is to be used at low frequencies, mounted on a curved surface, or when placed in the proximity of compact radiators. The characteristics of single and dual polarized convoluted FSS are analyzed and measured. The development of novel convoluted elements derived from the square loop slot is traced and their performance is examined. A novel technique of interweaving convoluted loops allows for further cell size reduction, while increasing the passband width, introducing flexibility in wideband FSS design, particularly for tailoring the electromagnetic architecture of buildings, and mobile communications in the built environment. Simulated transmission responses of the convoluted structures are in good agreement with the measurements.

Dual-Band Tunable Screen Using Complementary Split Ring Resonators

Active frequency selective surfaces (FSS) based on slot-form split ring resonators are described. Switching and tuning have been achieved using two different biasing circuit configurations. The first design switches ON and OFF the two concentric rings separately, producing four distinct transmission responses. The second design is able to vary the capacitance of the two split rings, allowing independent dual-band frequency tuning. The active FSS incorporate commercially available, low cost, surface mount switched PIN diodes and varactor diodes. The operation of the surfaces covers a wide band frequency range within the UHF spectrum, which is desirable for applications such as the modification of the EM architecture of buildings. Measurements compare well with the simulations.

An Active Annular Ring Frequency Selective Surface

Offering good performance in terms of all polarizations affected and good angular stability, the ring element is a popular choice in frequency selective surface (FSS) designs. This paper introduces a topology for two-state switching of a ring based FSS. The two states offered by the surface enable it to be either transparent or reflective at the frequency of interest. A design targeted at the 2.45 GHz WLAN band, and intended for the control of the electromagnetic architecture of buildings (EAoB), is realized both by simulation and measurement, the results of which are presented and evaluated.

Inkjet printed paper based frequency selective surfaces and skin mounted RFID tags: the interrelation between silver nanoparticle ink, paper substrate and low temperature sintering technique

Inkjet printing of functional frequency selective surfaces (FSS) and radio frequency identification (RFID) tags on commercial paper substrates using silver nanoparticle inks sintered using low temperature thermal, plasma and photonic techniques is reported. Printed and sintered FSS devices demonstrate performances which achieve wireless communication requirements having a forward transmission scattering parameter, S21, depth greater than -20 dB at 13 GHz. Printed and plasma sintered RFID tags on transfer paper, which are capable of being mounted on skin, improved read distances compared to previously reported single layer transfer RFID tags fabricated by conventional thermal sintering. This journal is cop. The Royal Society of Chemistry 2015.

Dual Polarized Reconfigurable Frequency Selective Surfaces

Novel band-stop active frequency selective surfaces (FSS) capable of modifying their response for different polarizations are proposed. Geometries based on full rings, and split rings are employed. The designs using full rings are able to tune over a wide frequency range while designs using split rings tune in a narrow frequency band. Both structures use a new biasing methodology which allows independent control of rows and columns of FSS arrays, therefore permitting independent modification of the transmission responses at the vertical and horizontal polarizations. Convoluting the shape of the elements significantly reduces the sensitivity to angle of wave incidence. The aim is to demonstrate a technology that could be used for various applications including modification of the electromagnetic architecture of buildings and the control of electromagnetic wave propagation to improve the efficiency of radio spectrum use. The surfaces incorporate commercially available, low cost, varactor diodes and surface mount resistors. Theoretical and experimental results confirm the operation of the surfaces within the UHF frequency band.

Towards inkjet-printed low cost passive UHF RFID skin mounted tattoo paper tags based on silver nanoparticle inks

The present work describes the inkjet printing and low temperature sintering of silver nanoparticle inks onto transfer tattoo paper. Our approach results in silver features of excellent resolution and conductivity and, subsequently the first passive UHF RFID transfer tattoo tags functional mounted on human skin of improved performance when compared to screen printed passive UHF RFID transfer tattoo paper tags. Moreover, inkjet printed passive UHF RFID transfer tattoo tags show similar performance to copper etched passive UHF RFID tags on plastic substrates. This study compares the image quality (resolution) and electrical performance of two commercial silver nanoparticle inks inkjet printed on transfer tattoo paper. The optimal printing and sintering parameters to obtain high resolution features of resistivities 20 to 57 times the resistivity of bulk silver (1.59 × 10−6 ohm cm) are described. We demonstrate how, by selectively depositing ink in specific areas of the antenna, read distance of passive UHF RFID tags can be increased from 54 to 68 cm whilst decreasing the amount of ink used by 33%. Furthermore, this approach results in inkjet printed passive UHF RFID tattoo tags with larger read distance than silver screen printed passive UHF RFID tattoo tags, 45 cm, and similar to copper etched passive UHF RFID plastic tags, 75 cm. Moreover, inkjet printed passive UHF RFID tattoo tags in this work are considerably thinner (1–5 μm) than screen and etched passive UHF RFID tags (tens of micrometers) hence, making the former more appealing to the end user. In addition to this, inkjet printing is compatible with large area manufacturing techniques and has the potential to evolve as one of the most promising RFID mass-production techniques. Therefore, this work represents a step towards the commercialization of on-body transfer tattoo paper passive UHF RFID tags.

3-D Printing of Elements in Frequency Selective Arrays

3-D printing is a technology that enables the fabrication of complex objects directly from a digital model. Folding the elements of Frequency Selective arrays in three dimensions gives a significant reduction in the resonant frequency for a given cell dimension, and such structures are candidates for additive manufacture. The aim in this paper is to demonstrate by example the development of novel electromagnetic structures that could be fabricated in parallel and integral with the additive manufacture of buildings, for electromagnetic architecture control. The principle is illustrated with two new geometries based on dipole and loop elements. The cores of these structures were fabricated with a 3-D printer that uses a plaster-based material. Theoretical and experimental results confirm the operation of the surfaces within the UHF frequency band.

Switchable Frequency Selective Slot Arrays

A switchable frequency selective surface (FSS) made of square loop slots and PIN diodes connected to a novel separate biasing circuit is presented. The structure uses a very thin, flexible substrate sandwiched between two physically independent metallic layers to create the active filter. An application is the modification of the EM architecture of buildings, where propagation could be controlled using active FSS. The relatively small number of elements employed creates a compact FSS structure which could fit in an aperture within a wall of a building. The Fabry-Perot approach is used to design a cascaded version for improved filter selectivity.