Evaluation of Polylactic Acid Polymer as a Substrate in Rectenna for Ambient Radiofrequency Energy Harvesting

Abstract

This work details the design and experimental characterization of a 2D rectenna for scavenging radio frequency energy at 2.45 GHz (WiFi band), fabricated on polylactic acid polymer (PLA) using a plastronics approach. PLA is the RF substrate of both antenna and rectifier. The two transmission line (TTL) approach is used to characterize the substrate properties to be considered during design. A linearly polarized patch antenna with microstrip transmission feeding is connected to a single series diode rectifier through a T-matching network. The antenna has simulated and measured gain of 7.6 dB and 7.5 dB, respectively. The rectifier has a measured DC output power of 0.96 μW at an optimal load of 2 kΩ under RF input power of −20 dBm at 2.45 GHz. The power conversion efficiency is 9.6% in the latter conditions for a 54 × 36 mm patch antenna of a 1.5 mm thick PLA substrate obtained from additive manufacturing. The power conversion efficiency reaches a value of 28.75% when the input power is −10 dBm at 2.45 GHz. This corresponds to a peak DC power of 28.75 μW when the optimal load is 1.5 kΩ. The results compare significantly with the ones of a similar rectenna circuit manufactured on preferred RF substrate.

Evaluation of Recycled Cardboard Paper as an Eco-Friendly Substrate for Rectenna and Ambient Radio Frequency Energy Harvesting Application

“…As expected and summarized in Table 13, the rectifier designed on Rogers substrate gives the best results, followed by the one on PLA substrate and cardboard material. This is due to the lowest loss tangent of Rogers substrate (0.0027), which is around four times lower than the one of PLA (0.01) [7], which is also approximately six times lower than the loss tangent of cardboard material #1 (0.055). Despite the lowest value of DC power, the rectifier on cardboard material offers acceptable operation within the range of power obtained for RF energy harvesting solutions (Table 13).…”

“…The TTL method is a simple method deployed over a wide band of frequency. The details of the TTL are described in the literature [7,32].…”

“…An inaccuracy could arise that would mask the difference in behavior resulting from the substrate face roughness. Equations ( 6) and (7) show the relationship between the length and width of the substrate as a function of the resonance frequency. Figure 13 also shows that the antenna on cardboard sample #1b (rougher surface) presents more losses than the same patch antenna fabricated on a smoother surface.…”

“…Polylactic acid (PLA) is an ecofriendly material reported for rectenna design [7]. PLA is compatible with additive manufacturing like 3D printing or fuse deposition modeling (FDM).…”

“…The lumped components, ground, power supply, via-ground, and via-inductor are connected to the schematic in (Figure 20 (bottom)). A previous work [7] details how matching was performed and describes how cosimulation is performed. To ensure that the rectifier is supplied with the intended input power (−10 dBm, −5 dBm, 0 dBm), directional couplers are utilized in the measurement setup (Figure 21).…”