Research Output
Gain Optimization of Low-Profile Textile Antennas Using CMA and Active Mode Subtraction Method
A wideband wearable antenna using inverse partial ground designed using characteristic mode analysis
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Publication
This paper presents an active mode subtraction method based on the characteristic mode analysis to estimate the forward directivity based on the difference in modal significance curves. This made the optimization of the antenna gain in the design process to be more efficient. To the best of the authors' knowledge, such method is innovative and proposed in literature for the first time. This method is derived on the basis that the total radiated field of the antenna, and consequently, the directivity is mainly contributed by the excited dominant modes. To demonstrate its effectiveness, three compact, planar, and wearable antennas with increasing complexity will be designed and optimized using this method. The first is a conventional circular patch antenna operating at 5.3 GHz, whereas the second one is a planar loop antenna operating at 3.08 GHz. The third design is a crown-shaped planar antenna (CPA) with a 3 × 3 artificial magnetic conductor (AMC) plane integrated underneath to reduce potential coupling effects from the body. All three antennas are made fully using textiles with the same thicknesses: felt fabric as its substrate and ShieldIt Super as its conductive textile. For all designs, the use of the proposed method, which is validated using the method of moments, has predicted the maximum direction of radiation and its respective gain at the desired frequencies with good accuracy. Besides that, the design of the AMC plane for the CPA is also optimized using CMA prior to the integration with the antenna and a leather wrist strap. Measurements of the final crown-shaped antenna design indicated a good agreement with simulations, with an operating bandwidth of more than 240 MHz, FBR of 15.73 dB and a directional radiation pattern outward from the body.
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Publication
The design of a wearable wideband textile antenna based on a loop structure and fed using a coplanar waveguide line is proposed in this work. Characteristic mode analysis is used to first estimate the radiating modes on the structure. This is to ensure that the optimal mode significance is chosen. Analysis of modal significance enabled the first four modes to be identified from the structure. In this paper, the antenna is proposed to designed with an inverse partial ground (IPG) to enhance the bandwidth. It is shown that this IPG method improved impedance bandwidth to 1560 MHz (60.57%), indicating a bandwidth broadening of about 370 MHz (11.61%). A compact size of 70×70 mm2(0.57 × 0.57 ?g) is also maintained, with a realized gain of 4.23 dBi. Finally, the proposed antenna is fabricated and measured to validate the analysis experimentally, indicating a good agreement with simulations.