Effect of Embroidery Style on the Bandwidth of Textronic RFID UHF Transponder Antenna

Abstract

The production of consumer electronics using electrically conductive materials is a dynamically developing sector of the economy. E-textiles (electronic textiles) are also used in radio frequency identification technology, mainly in the production of tag antennas. For economic reasons, it is important that the finished product is universal, although frequencies in radio systems have different values in different regions of the world. Therefore, the antenna bandwidth must be sufficiently wide so that the read range of the tag is maximally large for all frequencies of the specified band. The bandwidth of an antenna depends on its type and geometric dimensions, but this parameter can also be influenced by the way a given type of antenna is made. The authors prepared samples of embroidered RFID tag antennas for the UHF band using various types of embroidery. Then, its impedance and the read range of the tag were examined in order to determine the exact influence of the type of embroidery on the parameter of interest (antenna bandwidth). The results obtained during the research indicate the influence of different embroidery styles is present; however, that influence is not significant.

Keywords: RFID transponder; embroidered antenna; embroidery; textile antenna; textronics.

Figure 1

Block diagram of textronic RFID transponder (RFIDtex tag).

Figure 2

Geometry of designed antennas: (a) open contour; (b) closed contour; (c) planar.

Figure 3

Models prepared in PE DESIGN 11: (a) model MN1—open contour; (b) model MN2—closed contour; (c) model MN3—planar ver. 1; (d) model MN4—planar ver. 2; (e) model MN5—planar ver. 3; (f) model MN6—planar ver. 6.

Figure 4

Photograph of sewn samples (red ones—thread B; orange—thread A).

Figure 5

Photograph of a deformed sample (model MN6).

Figure 6

Models prepared in PE DESIGN 11: (a) model MN8—planar ver. 5; (b) model MN8—closeup; (c) model MN9—planar ver. 6; (d) model MN10—planar ver. 7.

Figure 7

Photograph of sewn samples (selected models from group D).

Figure 8

Photographs of the measurement stands: (a) impedance measurements; (b) anechoic chamber.

Figure 9

Reader parameters in Tagformance.

Figure 10

Impedance of the model antennas: (a) group A, real part; (b) group A, imaginary part; (c) group B, real part; (d) group B, imaginary part; (e) group D, real part; (f) group D, imaginary part.

Figure 11

SL3S1214 UCODE 7m chip impedance.

Figure 12

Calculated CMF: (a) calculations for group A; (b) calculations for group B; (c) calculations for group D.

Figure 13

Methodology of determining model antenna bandwidth.

Figure 14

Graphical representation of model antenna bandwidth (determined from CMF) values for: (a) samples from group A; (b) samples from group B; (c) samples from group D.

Figure 15

Read range of UHF RFID tag with model antenna—data obtained for group A.

Figure 16

Read range of UHF RFID tag with model antenna—data obtained for group B.

Figure 17

Read range of UHF RFID tag with model antenna—data obtained for groups C and D.

Figure 18

Graphical representation of model antenna bandwidth (determined from read range) values for (a) samples from group A; (b) samples from group B; (c) samples from group C; (d) samples from group D.