Mid Sweden University

In some of the radio-frequency identification (RFID) applications, RFID tag antennas will be printed onto flexible substrates. Sticked onto different surfaces, geometric distortion of the tag antenna, such as bending of the tag, could occur due to antenna substrate flexibility. In the present paper performance degradation due to such distortion of an RFID system, using the common half-wave dipole antennas usually used in tags, is simulated. It is shown that degradation of RFID system performance in terms of operating range due to such distortion is significant and that antenna structures less sensitive for this deformation should be considered for RFID systems where this kind of effect may occur.

Antennas in some military applications can be expected to suffer from physical damage of the antenna structure itself. Examples are intelligent munitions when rammed into the gun barrel and vehicle mounted conformal antennas harmed by various types of mechanical impact. Another example is extremely low cost antenna applications. A Radio Frequency IDentification (RFID) system consists of a more or less advanced reader and a very simple tag that can be fastened onto a variety of surfaces. The tag incorporates a transceiver and can carry one or more sensing devices and report findings back to the reader. To keep costs down, low-cost standardized antennas will be used even when the tag is deployed in harsh environments. For the kind of antennas described above, a predictable graceful degradation of performance is appealing. A partial damage of the antenna must not lead to a system breakdown. An essential part of the antenna design must be to ensure robust communication even when the antenna is partially damaged. What performance can be expected from an antenna when part of its structure has been removed? In this paper this issue is examined for a bow-tie antenna when part of its structure has been removed. The structural deformation has been inflicted by removing stripes of the outer part of one of the antenna arms. The investigation was undertaken by simulations in a commercial Finite Integration (FI) program and by verifying measurements.

This paper presents a methodology for the evaluation of antenna susceptibility to various types of random physical damage. A Monte Carlo statistical method is proposed to estimate antenna parameters for different damage levels. A virtual experiment is used in order to avoid lengthy experimental trials. Antenna parameters are modeled for each randomly generated damage pattern. Statistical post processing with the Bootstrap method evaluates the parameters acquired from the antenna modeling software. To illustrate the methodology a comparative study of the Input Return Loss for the damage inflicted upon a planar dipole and a bow-tie antenna is made. The median value is estimated to describe the "typical" behavior of the antenna. With taken assumptions, Input Return Loss for the Bow-tie antenna is found more sensitive to partial damage