A compact lumped-element two-way differential to single-ended Wilkinson power combiner with embedded impedance transformation

This letter presents a compact lumped-element two-way differential to single-ended Wilkinson power combiner with embedded impedance transformation. It consists of two transformer baluns and two parallel resistance and capacitor (RC) branches. The two transformers generate high-order impedance transformation networks at even-mode operation and form resonators together with the two parallel RC branches at odd-mode operation, thus achieving broadband impedance matching and power combining with a compact area. A proof-of-concept prototype working at 1.7 GHz is designed and fabricated. Measurement results show that the peak isolation is 24.5 dB, insertion loss is from 0.34 to 1.15 dB and magnitude and phase imbalance are within 0.1 dB and 1 circle ${1}<^>{\circ }$, respectively, over the frequency range from 1.37 to 1.97 GHz. The area is only 6.54 mm x $\times $ 6 mm.