A Dual-Polarized Solar Cell Stacked Microstrip Patch Antenna with a Ȝ/4 DC/RF Isolation Circuit for 5.8 GHz Band WiMAX Networks Okan Yurduseven, David Smith and Michael Elsdon Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, United Kingdom, okan.yurduseven@northumbria.ac.uk Abstract— In this paper, photovoltaic integration of a dual- polarized microstrip patch antenna is demonstrated for 5.8 GHz band WiMAX networks. The proposed antenna consists of a dual-fed ±45° dual-polarized square microstrip patch stacked with a polycrystalline silicon (poly-Si) solar cell operating as an RF parasitic patch element in addition to its photovoltaic function. A DC/RF isolation circuit consisting of quarter- wavelength microstrip transmission lines providing RF open- circuit and DC short-circuit impedances at the DC terminals of the stacked solar cell is used in order to minimize the effect of solar operation on the RF response of the antenna. It is demonstrated that the proposed solar patch antenna operates across a measured frequency band of 5.66-5.91 GHz with a gain of 7.6 dBi at the resonance frequency of 5.8 GHz. Index Terms—Solar antenna, dual-polarization, polarization diverse, DC/RF isolation, WiMAX. I. INTRODUCTION Recently, there has been a growing interest in integrating microwave antennas with solar cells into a single compact element for environmentally-friendly communication systems [1-10]. In this framework, work reported in the literature mainly focusses on the demonstration of linearly-polarized photovoltaic antennas [1-7]. However, in a practical communication environment, due to the presence of various elements, the signal between the transmitter and receiver in the uplink and downlink undergoes diffraction, reflection and scattering during the propagation, which results in the signal in a communication link being received as a combination of different polarizations. Therefore, in a real communication environment, polarization diversity is an important factor that needs to be considered in order to achieve the communication between the transmitter and receiver. In view of this, work into circularly-polarized photovoltaic antennas has been demonstrated in the literature with promising results [8-10]. However, no work has been carried out into the combination of dual-polarized microwave antennas with photovoltaics, which offer a significant potential to be employed in polarization diverse environmentally-friendly communication systems. Moreover, the use of dual-polarized antennas makes it possible to address the multipath fading and provides double transmission channels for frequency reuse communication systems [11, 12]. In this paper, a ±45° dual-polarized square microstrip patch antenna stacked with a polycrystalline silicon (poly-Si) solar cell, which operates as an RF stacked parasitic patch element in addition to its photovoltaic function, is proposed for polarization diverse 5.8 GHz band WiMAX communication systems. II. DUAL-POLARIZED SOLAR PATCH ANTENNA DESIGN AND RESULTS The proposed dual-polarized solar patch antenna is demonstrated in Fig. 1. Fig. 1. Dual-polarised solar antenna with DC/RF isolation (Dimensions in mm: A=4.25, B=1.64, C=0.37, D=15.2, W=60, L=62, h=2). The square patch is printed upon a 1.5 mm thick low-loss RT/Duroid 5870 substrate, İ r =2.33 and tanį=0.0012, with a ground plane on the backside. The patch is fed through two microstrip transmission lines each consisting of a quarter- wavelength (Ȝ r /4) sub-transmission line matching the impedance at the patch edge, which is 150, to the impedance of the input port, which is 50. While port 1 is used for +45° polarization excitation of the patch, port 2 provides -45° polarization excitation. As illustrated in Fig. 1, the microstrip patch is stacked with a poly-Si solar cell, which is suspended at 2 mm above the printed patch. The detailed structure of the stacked poly-Si solar cell is given in Fig. 2. The 8th European Conference on Antennas and Propagation (EuCAP 2014) 978-88-907018-4-9/14/$31.00 ©2014 IEEE 1382