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A three‐band tunable polarization‐insensitive metamaterial absorber is proposed in this paper. The unit cell of the absorber is composed of a dielectric substrate, a metal patch, and four varactor diodes welded on the top layer. A simple metal via bias network is designed to facilitate the absorption frequency tuning of the absorber. The simulation results show that when there is no bias voltage (0 V), the proposed absorber has three absorption peaks of 88%, 99.5%, and 99.8% under normal incidence at 7.27, 10.93, and 15.84 GHz, respectively. Furthermore, by adjusting the reverse bias voltage (0–19 V) of the varactor, the first absorption peak of the absorber can be tuned from 7.27 to 8.2 GHz and the second absorption peak tuned from 10.93 to 11.4 GHz. Meanwhile, the tuning range for the third absorption peak is 15.84–16.1 GHz. Furthermore, the three‐band absorption and frequency tunable characteristics of the absorber are confirmed by experimental tests. [ABSTRACT FROM AUTHOR]

In this letter, a rectangular‐cavity‐like structure is proposed to feed the phase gradient metasurface (PGM), where two symmetrical long slots are cut on side walls along wave propagation direction of the rectangular waveguide cavity resonator. It consists of rectangular waveguide, transition section, slotted‐waveguide feed section, and shorted end of the cavity. The PGMs are placed in the slotted‐waveguide section and the slot is wide enough to accommodate PGMs. The antenna prototype is fabricated and measured whose measurements agree well with simulations in 7.8–11.0GHz. [ABSTRACT FROM AUTHOR]

A narrow‐band bandpass filter (BPF) based on parallel coupled lines and shorted stubs with very wide upper stopband has been presented. The transmission coefficient and reflection coefficient of the proposed BPF are straightforwardly derived via the input impedances using odd‐ and even‐mode analysis method. The calculation results illustrate that two narrow passbands with very high frequency ratio of the upper‐band to lower‐band center frequencies can be realized, which is significantly suitable to design a narrow‐band BPF with very wide upper stopband. To verify the proposed design idea, a narrow‐band BPF example was designed and experimentally characterized, whose measured in‐band return loss is >30 dB with center frequency at 1.76 GHz. The measured upper stopband is up to 14.34 GHz with the rejection levels of over 20 dB. [ABSTRACT FROM AUTHOR]