A Novel Compact Design of Filtering Power Divider Based on Coupled Microstrip Lines

A compact, efficient wideband microstrip filtering power divider (FPD) is proposed to meet the requirements of integrated RF systems. The core innovation lies in adopting a single-layer folded structure that merges filtering and power-dividing functionalities, achieving significant miniaturization without compromising key performance metrics. The design integrates a coupled-line structure for broadband impedance matching and high selectivity, while a dual transmission line configuration extends the stopband and improves isolation. Odd- and even-mode equivalent circuit analysis is performed to clarify the distribution of transmission zeros (TZs), transmission poles (TPs), and impedance characteristics, while the initial value of the isolation resistor is derived to achieve optimal performance. A prototype centered at 3.2 GHz was fabricated and tested, showing a 3-dB fractional bandwidth (FBW) of 45 %, a minimum insertion loss (IL) of 3.52 dB, out-of-band rejection of 30 dB@2.2 f0, and port isolation greater than 17 dB. The proposed FPD offers an excellent balance of miniaturization 0.0475 λ2g, wideband functionality, and robust filtering performance, making it highly suitable for modern dense RF front-end integration.