Antenna Gain Calibration with Improved Accuracy Modeling of Pyramidal Standard Gain Horns

When using the gain transfer method with a pyramidal standard gain horn (SGH), it is common practice to use the on-axis NRL gain curves derived by Schelkunoff and Slayton [1]. Due to approximations in this formulation, Slayton assessed an uncertainty of ±0.3 dB for typical SGHs operating above 2.6 GHz. Since this uncertainty term is often one of the largest terms in the range measurement uncertainty budget for AUT gain, it is highly desirable to reduce it. Many studies in the past have attempted to improve upon Slayton’s expressions for SGH gain, but none have achieved widespread use.This paper investigates the use of several commercially available solvers, including HFSS™, CST Studio Suite®, and FEKO® to model the on-axis directivity and gain of a commercial offthe-shelf (COTS) X-band SGH provided by Microwave Vision Group (MVG) and referenced with the part number SGH820. Relevant modeling techniques are described in detail and are shown to employ best practices as well as conformance with the IEEE Standards for CEM modeling [2], [3]. The challenges and trade-offs of each CEM solving technique used, limitations of the CEM simulation errors, and practical considerations for antenna gain calibration are discussed.The CEM simulation results from multiple solvers in HFSS™, CST Studio Suite®, and FEKO® are shown to be within ±0.0075 dB of each other. Based on the compiled results of multiple simulations and measurements, this simulation methodology could be applied to other models of COTS SGH antennas to provide more accurate on-axis gain predictions.