Juha Lilja

Exposing textile antennas for harsh environment

Textile antennas as part of soldiers garment is commonly exposed to various harsh operational conditions. It is crucial that the communication link between soldiers is not compromised by the environmental conditions. The effect of water, ice and snow on the performance of fully textile antenna is studied in this paper. The effects of environmental exposure on antenna performance is validated via experimental tests, using a satellite communication systems; Iridium for a bi-directional satellite data transmission and GPS for a reception tests. During the tests the antenna is immersed into water, exposed to ice and snow while the communication link remains active. These results show that thorough understanding of the textile antenna design process leads to an optimal antenna performance even under the harsh environmental conditions.

Textile material characterization for SoftWear antennas

Modern industrial textile materials are composed of mechanically strong fibers that find their applications in integrated antennas within soldiers garment and armors in ballistic protection as well. This paper will cover electromagnetic characterization of such textile materials for SoftWear antenna substrate. Dielectric permittivity and loss tangent are analyzed and measured in varying relative humidity and temperature. In addition, the application of conductive textile materials to antennas is analyzed and discussed thoroughly.

Application of wide-band material parameter extraction techniques to printable electronics characterization

Material characterization is an important part of printable electronics design, since material properties depend strongly on the manufacturing process. This paper reviews application of wide-band extraction techniques to printable electronics characterization. The extraction methods are validated using full-wave simulation data with exactly known reference for material parameters. Suitable test structures are evaluated and applied to printable electronics characterization.

Significance of Conductivity and Thickness of Thin Inkjet Printed Microstrip Lines

The effect of conductor loss of very thin lossy printed silver nano-particle traces manufactured using the printable electronics technology is studied up to 10 GHz by simulations and measurements. First, microstrip resonators are used as test structures with measurements and simulations. In addition to this, the behavior of the attenuation of microstrip lines with different conductivity value and layer thickness pairs have been studied with simulations to achieve basic guidelines for the effects of parameter variation.

On the modeling of conductive textile materials for SoftWearAntennas

Wide-band simulation of the surface resistance requires that both thickness and conductivity are adapted for the conductive fabric. Because conductive fabrics are woven of metal-coated non-conductive yarns, an approach of using a thickness different from the physical thickness of the fabric may be justified. This approach is consistent with the fact that only part of the cross-section of the signal trace carries current. The sheet resistance defines the low-frequency resistive loss and connects the thickness of the fabric to its conductivity. Furthermore, the applied impedance model should yield a non-zero surface resistance being equal to the dc sheet resistance.

High-frequency characterization and simulation of conductor loss in printable electronics technology

The conductor loss of very thin lossy printed silver nanoparticle traces manufactured using the printable electronics technology is characterized up to 10 GHz by simulations and measurements. Microstrip resonators are used as test structures.

Characterization of conductive textile materials for SoftWearAntenna

Transmission line measurements have shown a potential in characterization of conductive textiles for SoftWearAntenna applications. Decrease in the conductivity of the fabric is seen to decrease the propagation velocity of a wave. This is expected to have a lowering effect on the operation frequency of textile antennas based on conductive fabrics when compared with antennas utilizing copper as conductive elements.

Application of Thin-Film RCLG Model for the Modeling of Inkjet Printed Microstrip Lines

Conductor thickness arising from printable electronics manufacturing technology is typically of the order of a skin depth in the frequency range from the upper UHF band to the lower SHF band. Modeling these conductors using standard circuit models however yield inaccurate results whereas full-wave modeling is very time consuming. In this paper, a circuit simulation model based on the surface resistance of a thin penetrable conductor is presented. The proposed model is validated by comparison with full-wave simulation results, Comparison with a conventional circuit-simulation model shows improved accuracy in the loss calculation.

Environmental characterization of industrial fabric for SoftWearAntenna

It was observed that changes in the environmental conditions have direct effect on the electrical parameters. High relative humidity increased the loss tangent. However, keeping the relative humidity constant while decreasing temperature, it was observed to decrease the loss tangent. It seems that the amount of water in the air controls the loss tangent; Decrease in temperature with constant relative humidity condenses some of the water vapor and thus the amount of water in the air is decreased. It was noticed that relative air humidity has a strong influence on permittivity. Increase in relative humidity was seen as an increase in permittivity and vice versa. Additionally, the temperature change affected the absolute value of permittivity. At lower temperatures the permittivity had lower values than at higher temperatures when the relative humidity remained fixed. Here, the absolute amount of water in the air seemed to be connected to this behavior as well.

Textile antennas: Shotgun proven performance

Demanding operational environments, especially in combat situations, expose soldiers garment integrated textile antennas to potentially destructive conditions. Until now, the environmental testing of textile antennas has included experiments that do not affect the physical integrity. Therefore, splinter effect on textile antennas is experimentally studied in this paper. Splinter effect is created by shooting the antennas with a shotgun. Different pellet sizes were tested. Rigid planar antennas were employed as a reference. Antennas were measured before and after the shooting event and the results showed that textile antennas can survive from a shotgun blast without significant reduction in electrical performance. Furthermore, the physical damages were less severe when compared to rigid antennas