ZHONG et al: CONFORMAL SPIRAL ANTENNA ON CONDUCTIVE TEXTILES 1  Abstract-We present a novel load-bearing spiral antenna on conductive textile threads (E-threads) for conformal applications. The textile spiral exhibits a nearly 10:1 bandwidth (0.3-3GHz) with circularly polarized gain of 6.5dBi across the 1-3GHz bandwidth. Such performance is unique for textiles and flexible surfaces. An important aspect of this paper is the demonstration of repeatable performance for this textile spiral antenna. Also, mechanical tests for the spiral showed no appreciable changes in performance, even after 300 flexing cycles. The spiral is a cavity-backed configuration with its ground plane also embroidered using very thin (diameter=0.12mm) Elektrisola E-threads. These threads can achieve geometrical precision down to 0.1mm. To enhance robustness, high-strength Kevlar fabric was employed as the substrate. Overall, the proposed spiral is very attractive for several wideband, conformal, and load-bearing applications, such as airborne and wearables.

The viability of a radiofrequency (RF) telemetry channel for reporting individual neuron activity wirelessly from an embedded antenna to an external receiver is determined. Comparing the power at the transmitting antenna required for the desired Channel Capacity, to the maximum power that this antenna can dissipate in the body without altering or damaging surrounding tissue reveals the severe penalty incurred by miniaturization of the antenna. Using both Specific Absorption Rate (SAR) and thermal damage limits as constraints, and 300 Kbps as the required capacity for telemetry streams 100 ms in duration, the model shows that conventional antennas smaller than 0.1 mm could not support human neuronal telemetry to a remote receiver (1 m away.) Reducing the antenna to 10 microns in size to enable the monitoring of single human neuron signals to a receiver at the surface of the head would require operating with a channel capacity of only 0.3 bps.

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