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2 Resonators
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  • Xiaohu Wu ,
  • Mahmoud Nafe ,
  • Alejandro Alvarez Melcon ,
  • Juan Sebastian Gomez-Diaz ,
  • Xiaoguang Liu
Xiaohu Wu
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Mahmoud Nafe
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Alejandro Alvarez Melcon
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Juan Sebastian Gomez-Diaz
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Xiaoguang Liu
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Abstract

This paper presents novel designs of frequency reconfigurable distributed non-reciprocal bandpass filter and diplexer based on spatio-temporally modulated microstrip λg/2 resonators. The modulation is achieved by loading both ends of the λg/2 transmission line resonators with time-modulated capacitors. To provide an inherent biasing isolation between the RF and the modulation signals, the modulation voltage source is connected at the center of the resonator, where there is a natural voltage null. A single inductor is used to further enhance such biasing isolation. The wideband nature of this isolation scheme enables the tuning of the devices over a wide frequency range. With more than 30-dB RF to modulation isolation, the proposed resonator structure also enables low insertion loss by eliminating RF signal leakage to the modulation ports. Two examples of a 3-pole bandpass filter and a diplexer are demonstrated with good agreement between the measurement and the simulation. The fabricated filter shows a minimal insertion loss of 3.9 dB, a 20-dB isolation bandwidth of 42 MHz at 1.0 GHz, and frequency tuning range of 885-1031 MHz. The measured diplexer has two non-reciprocal bandpass channels at 829 MHz and 997 MHz, respectively. The two channels can be independently reconfigured without affecting each other.
Feb 2021Published in IEEE Transactions on Circuits and Systems II: Express Briefs volume 68 issue 2 on pages 667-671. 10.1109/TCSII.2020.3014499