What is the difference between a resistive and a reactive power divider?

A resistive power divider uses resistive elements (thin-film or chip resistors) to split the signal and absorb unwanted reflections, while a reactive power divider uses transmission-line sections (quarter-wave transformers) to achieve an impedance-matched split with minimal loss. Key differences: (1) Resistive divider: uses three resistors in a star or delta configuration. For a 2-way equal split in 50-ohm system: star configuration uses three 16.7-ohm resistors, delta configuration uses three 150-ohm resistors. Inherent 6 dB loss: even an ideal resistive divider has 6 dB insertion loss per path (-3 dB from the split + 3 dB absorbed in the resistors). This is because the resistors dissipate half the power to maintain port matching. All three ports are matched (S11 = S22 = S33 = 0 for ideal). Output port isolation: 6 dB. Bandwidth: extremely broad (DC to the frequency limit of the resistors, typically DC to 40+ GHz for thin-film resistors). Size: very small (a few mm at microwave frequencies). (2) Reactive (Wilkinson) divider: uses quarter-wave transmission lines (impedance = Z0×sqrt(2) = 70.7 ohms for 50-ohm system) and one isolation resistor (100 ohms for 50-ohm system). Inherent 3 dB split: the ideal Wilkinson has 0 dB excess loss (all power is delivered to the outputs, none is dissipated in the resistors for an equal split of matched loads). The isolation resistor only dissipates power when the output loads are unequal. All three ports are matched at the design frequency. Output port isolation: 20-30 dB (much better than resistive). Bandwidth: limited by the quarter-wave sections. Single section: 20-40% BW (where matching and isolation remain acceptable). Multi-section: up to octave or greater bandwidth. Size: each arm is lambda/4 long (7.5 mm at 10 GHz in microstrip on FR-4).