Dual‐band filtering power divider with unequal power division ratio and low‐loss characteristic

Abstract

In this article, a dual-band filtering power divider with unequal power-division ability is proposed. Different from conventional equal power dividers constructed by filters or coupled resonators, noncoupled structures are employed in this design. As a result, low-loss characteristic is realized for the proposed power divider. In this proposed structure, the dual-band unequal power allocation is realized by replacing conventional single-band λ/4 transformers with dual-band ones (T-junction structures). Three identical λ/4 stepped impedance resonators are properly attached to all the three ports of the proposed power divider to generate an extra transmission zero between two operational bands. Therefore, a filter-like shaping in its S-parameter results is obtained. A resistor is located between two outputs for output isolation. Mathematical derivations of the overall design procedure are also provided based on the circuit models and transmission line theory. Meanwhile, a resistor for output isolation is also included between two outputs, whose value can be calculated using given equations. For validation, a prototype operating at 0.9 and 2.1 GHz are designed, fabricated, and measured. The isolations between two outputs are 30 and 26 dB while the phase differences are only 2.5°and 4.9° at 0.9 and 2.1 GHz in the measurement, indicating good consistence of outputs. Measured |S21| and |S31| are −(1.76 + 0.3) dB, −(4.77 + 0.2) dB at 0.9 GHz and −(1.76 + 0.6) dB, −(4.77 + 0.5) dB at 2.1 GHz.