Miniature Convoluted FSS for Gain Enhancement of a Multiband Antenna

Garth D Catton,Steven G O'Keefe,Aliya A Dewani,Hugo G Espinosa

doi:10.1109/access.2021.3060398

Garth D Catton, Steven G O'Keefe + Show 2 more

Open Access

https://doi.org/10.1109/access.2021.3060398

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Abstract

Convoluted elements on a frequency selective surface (FSS) allow for low frequency elements to be contained in physically smaller unit cells. Smaller unit cells give the FSS greater angular stability, especially where a curved FSS is required, and so unwanted grating effects are avoided. A convoluted element FSS with a frequency rejection band centred at 2 GHz and unit cell area of 15 mm by 15 mm ( $0.10\,\,\lambda \times 0.10\,\,\lambda$ ) has been developed. To test its usefulness, the full structure FSS is used as a parabolic reflector in a dual band FSS reflector antenna operating at 1 GHz and 2 GHz. Simulated and measured results are close at both bands. The reflector antenna has high gain at 2 GHz of 12.7 dBi (simulated) and 11.7 dBi (measured). To observe the angular stability of the FSS and therefore its effectiveness as a reflector, it was compared with a copper test reflector at both bands. Simulation of the reflector antenna with test reflector produced a 2 GHz gain of 13.3 dBi which is very close to that with the FSS reflector. The simulated 2 GHz gain plot of the reflector antenna with FSS reflector is very similar to that with the test reflector indicating that the FSS has good angular stability. The gain at 1 GHz is also high with 9.3 dBi (simulated) and 8.7 dBi (measured). Simulation of the reflector antenna with no FSS and only a rear test reflector produced a 1 GHz gain of 10 dBi which is very close to that with the FSS reflector in place indicating that the FSS causes no significant attenuation at that frequency. The convoluted element FSS would be useful as a curved reflector in the creation of high gain, multiband, conformal antennas.

Highlights

With the roll out of 5G communication infrastructure there is a need for small, conformal, high gain, antennas and often there is a requirement for those antennas to be multiband
The reflector antenna gain was measured using the gain standard antenna replacement technique. This technique requires that the distance between the antenna under test (AUT) and the test antenna places them in each other’s far field at the frequencies of operation
This is important as the AUT utilizes an frequency selective surface (FSS) and it’s the far field frequency response characteristics of the FSS that are of interest for these measurements

Summary

Introduction

With the roll out of 5G communication infrastructure there is a need for small, conformal, high gain, antennas and often there is a requirement for those antennas to be multiband. Small multiband antennas can be realised using frequency selective surfaces (FSS). An FSS behaves differently depending on the frequency of an incident electromagnetic (EM) wave. A band stop FSS consists of a periodic array of conductive elements on a dielectric substrate. It reflects EM waves at one frequency band while EM waves at other bands pass through with minimal attenuation [4].

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