By exploiting bended microstrip lines and tapered resonators, a new microstrip dual‐band bandpass filter (DBBPF) with tunable center frequency and compact size is proposed, analyzed, and fabricated. The LC equivalent circuit of the basic resonator is introduced to present an analytical description. The proposed filter has two passbands at the center frequencies of 2.4 and 5.7 GHz. The measured data show <0.22 and 0.56 dB insertion losses in the first and second bands, respectively, which are considered as a marked advantage. Furthermore, without increasing the circuit size, the second band can be tuned between 3.85 and 7.5 GHz. Finally, an acceptable similarity is observed between the simulated and measured S‐parameters.

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In this letter, a compact dual‐band bandpass filter (BPF) is designed, analyzed, and fabricated. A loop resonator loaded by two modified T‐shaped resonators, double T‐shaped resonators, and open bended stubs are applied to form the proposed configuration. The coupling spaces between the loop resonators and open bended stubs result in two passbands with the center frequencies of 2.4 GHz and 5.7 GHz. The LC equivalent circuit of the main resonator is introduced to present an analytical description. Without needing to increase the circuit size, the upper passband can be adjusted between 5.72 GHz and 6.93 GHz. The measured data indicates less than 0.64 dB and 0.76 dB insertion losses in the first and second passbands, respectively. Adjustable second center frequency, compact size, low insertion loss, good suppression level, and a symmetrical structure are the marked features of the proposed BPF. Finally, a good agreement between the simulated and measured results is observed.

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A highly sensitive absorption-based sensor based on folded split-ring metamaterial graphene resonators (FSRMGRs) is designed, and its biomedical application in terahertz (THz) spectrum is investigated. The sensor has a nearly perfect absorption with a spectral absorption coefficient of 99.75% at 4 THz, with a high Q-factor (average) of 13.76. The resonance peak frequency is sensitive to the refractive index (RI) of the test medium (analyte) and a fairly high sensitivity of 851 GHz/RIU has been obtained. The specifications of the sensor can be tuned by an external DC-bias voltage applied to the graphene layer. According to the obtained results, the developed absorber appears to be a good candidate bio-sensing applications.

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