Flexible antennas for GPS reception

International Journal of Antennas and Propagation

2012

When circularly polarized (CP) microstrip antennas are bent, the polarization becomes elliptical. We present a simple model that describes the phenomenon. The two linear modes present in a CP patch are modeled separately and added together to produce CP. Bending distorts the almost-spherical equiphase surface of a linearly polarized patch, which leads to phase imbalance in the far-field of a CP patch. The model predicts both the frequency shifting of the axial ratio band as well as the narrowing of the axial ratio beam. Uncontrolled bending is a problem associated especially with flexible textile antennas, and wearable antennas should therefore be designed somewhat conformal.

Section: Comments On the Modelmentioning

confidence: 98%

Analysis of Circular Polarization of Cylindrically Bent Microstrip Antennas

International Journal of Antennas and Propagation

2012

“…In addition to screen printing [7][8][9], wearable antennas have been fabricated of conducting textiles [10,11], conductive ribbons [12], and copper meshes [13], embroidered using conductive thread [12,14] and sprayed using conductive paint [12]. Copper tape is often used for first prototypes, but it easily breaks in use and cannot be used in consumer products.…”

Section: Wearable Rfid Tagsmentioning

confidence: 99%

Towards Washable Wearable Antennas: A Comparison of Coating Materials for Screen-Printed Textile-Based UHF RFID Tags

International Journal of Antennas and Propagation

Virkki

Merilampi

et al. 2012

(Radio frequency identification) RFID tags integrated into clothing enable monitoring of people without their conscious effort. This requires tags to be an unnoticeable part of clothing and comfortable to wear. In this study, RFID antennas were screen printed on two different fabrics, six different coating materials for the (integrated circuits) ICs were applied, and the reliability of these RFID tags was tested with moisture and laundry tests. Generally, glue-type coating materials were easier to handle and could be spread precisely. All the tags were operational immediately after the coatings were applied, and five of the coating materials were seen to protect the IC from detaching in the laundry. It was found that the uneven fabric surface caused discontinuities and breaks in narrow conductors, and thus hard coatings may also be needed to keep the tag from breaking in laundry.

“…Example designs of wearable antennas include a variety of microstrip patch antennas [2], dipoles [3], and invertedF antennas [4]. The process flow of textile antenna design is described in [5].…”

Section: Introductionmentioning

confidence: 99%

Snaps to Connect Coaxial and Microstrip Lines in Wearable Systems

International Journal of Antennas and Propagation

2012

Commercial snaps (clothing fasteners) can be used to connect a coaxial cable to a microstrip line. This is useful in the context of wearable antennas, especially in consumer applications and disposable connections. The measuredS-parameters of the transition are presented, and an equivalent circuit and approximate equations are derived for system design purposes. The proposed connection is usable up to 1.5 GHz (10 dB return loss condition), and the frequency range can be extended to 2 GHz if a thinner, more flexible coaxial cable is used.