Novel Hybrid Tolerance Analysis Method with Application to the Low Cost Manufacture of Edge Slot Waveguide Arrays

摘要

Edge slot waveguide antenna arrays have been extensively employed in surveillance radar applications, such as the Airborne Warning and Control System (AWACS), where large volume coverage at a relatively low cost can be achieved via phase shifter electronic scanning in elevation and 360° mechanical scanning in azimuth. One of the requirements typically set forth in such applications is an extremely low side lobe level (SLL). In the edge slot array, this requires accurate dimensional tolerance control of the slot parameters: (1) width, (2) tilt angle, (3) depth, and (4) location. Modern manufacturing processes are capable of achieving extremely accurate dimensional tolerances, and it is tempting to simply specify the tightest slot tolerances possible. However, over specifying the necessary slot tolerances can artificially increase cost to the point where the ID electronically scanned antenna (ESA) edge slot waveguide array is not economically feasible in an application that could have otherwise benefited from its performance advantages. It is the job of the engineer to determine the appropriate slot tolerances required to provide the desired performance and production yield while maintaining the lowest production cost. To this end, a Monte Carlo based tolerance analysis method was developed that utilizes a standard shunt admittance transmission line model for the edge slot waveguide. The shunt admittances are derived by interpolating between a three dimensional dataset generated in Ansoft HFSS™. This hybrid tolerance analysis method provides an efficient and accurate means of determining the effects of slot dimensional tolerances on the SLL and input impedance of the edge slot waveguide array. It is the purpose of this paper to describe the tolerance analysis method in detail and illustrate its use in the low cost design and manufacture of ID ESA edge slot waveguide arrays.