Wilkinson power divider

In the field of microwave engineering and circuit design, the Wilkinson Power Divider is a specific class of power divider circuit that can achieve isolation between the output ports while maintaining a matched condition on all ports. The Wilkinson design can also be used as a power combiner because it is comprised of passive components and hence reciprocal. First published by Ernest J. Wilkinson in 1960 [E.J. Wilkinson, "An N-way Power Divider", "IRE Trans. on Microwave Theory and Techniques", vol. 8, p. 116-118, Jan. 1960] , this circuit finds wide use in radio frequency communication systems utilizing multiple channels since the high degree of isolation between the output ports prevents crosstalk between the individual channels.

Theory

The scattering parameters for the common case of a 2-way equal-split Wilkinson power divider at the design frequency is given by [D.M. Pozar, "Microwave Engineering", Third Edition, John Wiley & Sons: New York, 2005]

:

Inspection of the "S" matrix reveals that the network is reciprocal ($S\_\{ij\}=S\_\{ji\}$), that the terminals are matched ($S\_\{11\},\; S\_\{22\},\; S\_\{33\}=0$), that the output terminals are isolated ($S\_\{23\},\; S\_\{32\}$=0), and that equal power division is achieved ($S\_\{21\}=S\_\{31\}$). The non-unitary matrix results from the fact that the network is lossy.

Interestingly, no loss occurs when the signals at ports 2 and 3 are in phase.

See Also

*Power dividers and directional couplers

References