**Jose L. Medran del Rio 1, Aintzane Lujambio 2, Armando Fernández-Prieto 1,\*, Alejandro Javier Martinez-Ros 3, Jesús Martel <sup>4</sup> and Francisco Medina <sup>1</sup>**


Received: 27 March 2020; Accepted: 27 April 2020; Published: 29 April 2020

**Abstract:** A new dual-band balanced bandpass filter based on magnetically coupled open-loop resonators in multilayer technology is proposed in this paper. The lower differential passband, centered at the Global Positioning System (GPS) L1 frequency, 1.575 GHz, was created by means of two coupled resonators etched in the middle layer of the structure, while the upper differential passband, centered at a Wi-Fi frequency of 2.4 GHz, was generated by coupling two resonators on the top layer. Magnetic coupling was used to design both passbands, leading to an intrinsic common-mode rejection of 39 dB within the lower passband and 33 dB within the upper passband. Simulation and measurement results are provided to verify the usefulness of the proposed dual-band differential bandpass filter.

**Keywords:** dual-band differential filter; common-mode suppression; magnetic coupling; multilayer structure
