A multimode, broadband and all-inkjet-printed absorber using characteristic mode analysis

In this paper, we demonstrate a multimode and broadband absorber that is fabricated directly on PET substrate using a commercial direct-to-garment (DTG) inkjet printer. A design procedure of this kind of absorber is presented. Based on the theory of characteristic mode, the underlying modal behaviors of the absorber structure are firstly analyzed to guide the design of multimode absorber. Two modes on the absorber structure are designed to resonate around 1.83 GHz and 4.28 GHz to cover the working frequency range. Simulation and measurement results show that the multimode absorber with a total thickness of 0.0883λ_L at the lowest operating frequency can achieve broadband microwave absorption with efficiency over 90% in the frequency band of 1.0 ∼ 4.5 GHz (127.3% in fractional bandwidth) through deliberate design. Both the simulated and experimental results demonstrate the validity of the proposed method and indicate that the method can be applied to other microwave and millimeter-wave regions.