by Y.Y. Yang, X.W. Shi, X.H. Wang, X.Q. Chen and D.Z. Chen, Xidian University, Shanxi, China
A power divider is one of the most important passive circuits used in microwave and millimeter-wave applications. In 1960, Wilkinson proposed an N-way in-phase power divider.1 He described a circularly symmetric power divider, which split a signal into N-equiphase and equiamplitude signals with an even or odd number N.
Since then, several different N-way power dividers have been proposed.2,3 All of them are for equal power dividers. In 2004, an N-way power divider with an arbitrary power split ratio was proposed by Ahn.4 In Ahn’s article, the circuit and design formulas are given, resulting in high isolation between ports. However, the structure of the divider is difficult to fabricate and it operates at a single frequency. In 2003, a small dual-frequency transformer section was introduced by Monzon,5 which operates at any two arbitrary frequencies, f1 and f2. In this article, an extension of Monzon’s analysis to the design of an improved N-way dual-frequency power divider is presented. The proposed power divider operates at two arbitrary frequencies f1 and f2, and with an arbitrary power split. The design equations are given and a new circuit is proposed, which is easy to fabricate and also has a high isolation. To verify the design method, a three-way power divider, with a power split ratio of 1: 2: 3 at both frequencies 0.915 and 2.45 GHz, which can be used in RFID applications, has been simulated and fabricated using microstrip technology. The validity of this analysis is demonstrated by experimental results.
Analyses and Design Equations
Figure 1 Diagram of an N-way arbitrary power divider.
The configuration of an N-way arbitrary power divider with arbitrary power division ratio is depicted in Figure 1, where all the transmission lines are λ/4 long, Z11, Z12, Z21,…, ZN2 represent the characteristic impedances of 2N transmission lines, respectively. If the power split ratio is P1: P2: P3…: PN = K1: K2: K3…: KN, the following equations can be obtained:
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