Crossovers are very interesting structures in monolithic Integrated Circuits (IC), antenna arrays and so on, which features two signal paths crossing over each other with high isolation and matched ports. There are different types of crossovers; air bridges, bond wires and printed planar crossovers for single and dual band, these crossovers are always used for connection and transport of signals between layers. Usually coupled transmission lines are utilized to design power dividers, couplers and filters. Moreover, coupled lines loaded with open/shorted stubs are used to design band-pass filters. Recently, the coupled lines loaded with open/short stubsare used to design planar crossovers.
In this article, a compact single planar crossover based on coupled lines is designed using SOLIDWORKS and simulated using the full wave 3D simulator HFWorks. An S Parameters analysis is conducted to characterizethe electromagnetic behavior of this structure.
The Model Geometry
This compact planar crossover example is formed of two coupled lines loaded with two open stubs. The resonance frequency of this crossover is 1.8GHz. It is constructed on the dielectric substrate with a relative permittivity of 2.65 and a dielectric loss tangent of 0.003. The overall size of the single band crossover is about 48 mm x 30 mm x 0.508 mm. The 3D model is shown in Figure 1.
Figure1 - The 3D SOLIDWORKS Model of the compact planar crossover (front and end view)
Two transmission lines are connected at port 1, 4 and ports 2, 3 as depicted in Figure 2.The ground plane of this structure is slotted using patterned ground-plane technique to increase the impedance ratio between the even and the odd mode impedances for the coupled lines. The structure parameters are summarized in Table 1.
The simulated S parameters results S11 and S31 using HFWorks and the measured results of the single band crossover are depicted in Figure4. The S Parameters are shown from 0.5 GHz to 3.5 GHz. the central frequency is located around 1.8 GHz.
Figure 3 - The return loss S11 measured and simulated resultsThe transmission coefficient |S31| is greater than -0.6 dB while the simulated |S11| is less than -20 dB for 1.81 - 1.875 GHz.
Figure 4 - S11 and S31 of the single band crossover
The isolation|S21| and |S41| are less than -20 dB for 1.73 - 1.814 GHz, and 1.81 – 1.87 GHz respectively, as shown in Figure5.
Figure 5 - S41 and S21 of the single band crossover
HFWorks automatically computes the electromagnetic field.The distribution of the electric field at the resonance frequency is shown in Figure6. The incident power is 1W.
Figure 6 - Distribution of the electric field at 1.80 GHz
A single band crossover is designed and simulated using the duo of SOLDWORKS and HFWorks. Good agreements can be observed between simulated results and the measured data .The resonance frequency is found at 1.80 GHz.
 https://www.emworks.com/product/ATLASS Wenjie Feng, Tianyu Zhang, WenquanChe“Compact Single-band Planar Crossover Based on Coupled Lines”Proceedings of the 46th European Microwave Conference, pp. 975 – 978, Oct 2016.