Miniaturizing Wilkinson Power Dividers

March 28, 2017

This application brief explains how one can utilize design software to create a compact Wilkinson power divider.

Wilkinson power dividers, commonly used in RF/microwave applications, can achieve high isolation between output ports while also maintaining a good match on all ports. In the application example, “Design of a Reduced Footprint Microwave Wilkinson Power Divider With EM Verification,” National Instruments presents how its AWR Design Environment was utilized to design a Wilkinson power divider with a compact footprint.

The design flow consists of three steps. First, a design is created using ideal transmission lines. The next step involves updating the ideal schematic with the actual microstrip lengths and widths. The final step is generating the design’s physical board layout.

As mentioned, the first step took advantage of ideal transmission-line models. The electrical lengths of these transmission lines were derived by specifying a frequency of 2 GHz, which is the intended center frequency. After identifying the properties of the chosen substrate, the physical attributes of the ideal transmission lines can be determined. Those attributes were obtained via the TX-LINE transmission-line calculator.

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Next, an updated schematic was created that incorporated the microstrip lengths and widths. The schematic contains both MTEEX$ and MTRACE2 elements. The MTEEX$ is a microstrip tee-junction element, and the MTRACE2 element is a microstrip meander line element. The MTRACE2 elements are employed so that the quarter-wavelength microstrip lines can be bent in the layout environment.

The last step involved creating the physical board layout, with a goal of minimizing the board area without compromising performance. The application brief explains how to add bends to microstrip lines in the layout. The document also discusses how to account for coupling between sections by utilizing automated-circuit-extraction (ACE) technology. ACE is a tool that can extract high-frequency models of the layout—including coupling effects.

After completing the layout, the next step was to further miniaturize the layout. The AXIEM 3D planar electromagnetic (EM) simulator was used for final EM verification.

National Instruments Corp., 11500 N Mopac Expwy., Austin, TX 78759-3504; (877) 388-1952; www.awrcorp.com.