Cross-Functional Integration of Dielectric Resonator Bandpass Filter and Antenna Array With Low Insertion Loss and High Isolation

High insertion loss and poor isolation are difficult problems for the cross-functional integration of filters and antenna arrays. A coupling regulation technique based on metal superstrates is proposed to address these problems in this article. The superstrate serves both as a reflector for the filter and as a coupler for the antenna array. First, the operating modes for the two channels are selected based on image theory, and the filter and the antenna array are integrated by sharing dielectric resonators (DRs) to obtain a cross-functional design. However, simultaneous optimization of insertion loss and antenna isolation is difficult due to their strong interdependence. In this design, the structural adjustments of the metal superstrate are guided by self-impedance and current distribution analysis, enabling independent optimization of the additional reflected waves and coupling waves. Consequently, filter coupling is enhanced while antenna coupling is reduced. Two prototypes were fabricated, with dimensions of 0.92λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.79λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.21λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and 1.46λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.79λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.21λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>. The second-order prototype features an insertion loss of 0.74 dB and antenna isolation exceeding 25dB, while the fourth-order prototype exhibits an insertion loss of 1.45 dB and antenna isolation greater than 18 dB. Peak boresight gains reach 8.1 dBi and 9.9 dBi for the two- and four-element arrays, respectively. The four-element array supports a ±55° scanning range with 0.8 dB scan loss.