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Where To Find This Example

AWR Version 14

Understanding AWR .emz Files

AWR Version 13

This example was renamed since the previous version. Please see Previous Example Page for the version 13 page.

Design Notes

Optimization of RF Board to Waveguide Transition

This E-band 77-82GHz transition has a long simulation time due to all the sweeps incorporated in the project

Download

Simulating this project is time-consuming.  This example, with the datasets included, is available at: http://kb.awr.com/display/examples/Waveguide_to_RF_board

Overview

This project implements a microstrip to waveguide transition based on the following paper that describes a 2 layer Duroid RF board and E-band waveguide that utilizes an integrated backshort in the RF Board.  This example illustrates the capability to aggregate multiple technologies and simulator types into one EM Document through the use of an arbitrary 3D Analyst EM Cell and AXIEM 2 layer board EM structures.  Measured data from the paper was implemented in the “PaperResponse” datafile in the project to compare against Analyst simulation results of the whole transition simulation.

"Millimeter-Wave Microstrip Line to Waveguide Transition Fabricated on a Single Layer Dielectric Substrate", H.Iizuka, T.Watanabe, K.Sato, K.Nishikawa, R&D Review of Toyota CRDL, Vol 37, No 2.  Pg 13-18.

Modeling and Simulation

The paper describes the transition as constructed in the EM structure “WG_to_Microstrip_Hierarchy_AsFabricated”

and has all the material parameters and As-Fabricated dimensions included in the paper (Table 1 values in parenthesis).  This project was implemented hierarchically with the waveguide being an arbitrary Analyst 3D editor cell for an E-band rectangular waveguide section implemented as a copper boundary condition.  The 2-layer RF board was implemented in AXIEM using the built-in 2-layer RF board PDK's layers but modified for the Duroid electrical characteristics to match the paper's material set.  Both EM Document subcircuits were instantiated in the higher level EMDoc through the use of hierarchy.

In the paper, multiple dimensions of the design are optimized to obtain the performance for the transition.  “Rho” represents the extension of the microstrip probe, “L” and “W” represent the length and width of the radiating patch and “deltaY” is the location of the patch relative to center.  All of these variables are parameterized in the AXIEM and Analyst EM Docs in this project and swept blocks are used so that in a circuit schematic the transition can be optimized in AXIEM first.  Then longer simulations can be created with a combination of the AXIEM EMDoc with the Analyst 3D cell for the waveguide for the higher level simulation.

This project also illustrates the use of Shape Pre-Processing to automatically convert the round RF board drill vias to squares during EM simulation which matches the analysis done by the authors of this paper.

Simulation Plots

Waveguide to Microstrip Transition Thru GS - This graph illustrates Analyst simulated vs. measurements for the entire transition using as-fabricated parameters for the simulation.  The plot uses the Generalized S-Parameter measurement to automatically give the correct response when connecting to a waveguide port by automatically normalizing to the impedance of the waveguide port being referenced rather than characteristic impedance of 50Ohms. Reproduces the response in the paper's Figure 5.

Board Transition Only - AXIEM simulation of board radiating to free space against measured data for the entire transition.  Shows the waveguide causing a shift down in the return loss.

Delta Y Sweep - Sweep of the deltaY location showing the sensitivity of the transition performance to board and assembly registration of the transition.  Compare this plot to the paper's Figure 7b to show excellent agreement.