Uncertainty Assessment of a Small Rectangular Anechoic Chamber: From Design to Operation

Abstract

Anechoic chambers are widely used to measure antenna parameters because of the free reflection conditions inside them. Recently, there has been increasing research into antennas working at frequencies from 20 to 70 GHz. Generalpurpose anechoic chambers are usually between 5 and 10 meters in size, which leads to free space distances longer than required at millimeter wave frequencies, and corresponding larger cables losses. Designing anechoic chambers tailored to such a frequency range would lead to minimum losses and improve measurement performance. If uncertainty is considered all the way from the design stage to operation, it will be easier to obtain highly accurate measurement outcomes. This paper focuses on the issues related to uncertainty in a tailor-made millimeter wave anechoic chamber at every step before achieving a fully functional measurement system. This includes setting the requirements for the chamber, calculating its dimensions, designing the structure and selecting the building materials, in order finally to characterize its performance by measuring the insulation from external signals and the ripple in the quiet zone. This process has resulted in a full description of design, construction and operation stages of an anechoic chamber from the point of view of the control on the measurement uncertainty. Index Terms-Anechoic chambers (electromagnetic), antenna testing, measurement uncertainty, millimeter waves. I. INTRODUCTION EASUREMENTS of antennas in the far field region are extensively performed in anechoic chambers as they provide a controlled environment free from reflections and undesirable external signals. In recent years, novel antenna designs at frequencies in the 20-70 GHz range have been developed [1]-[6]. General-purpose anechoic chambers for traditional measurements of antennas between 1 to 18 GHz have sizes between 5 and 10 meter [7], depending on the used range antennas and other design requirements. At such distances for the above frequencies, free space and test cable losses are high, making the received signal power too close to the receiver noise floor. Amplifiers can help overcome the Manuscript

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