VAlidation STandard antennas: Past, present and future

The field of antenna measurements is lacking a Golden Standard, i.e. an antenna of which the pattern is known by definition. To gain confidence in the performance of a range, including the procedures and skills of the operators, range comparison has been a popular tool for over three decades. In the beginning, ad-hoc available antennas were shipped around the various ranges. Soon it became clear that the comparisons were restricted by the properties of the antenna. The European Space Agency (ESA) stimulated and supported the development of a dedicated VAlidation STandard (VAST) antenna, specifically designed for validation campaigns of antenna measurement ranges. The driving requirements of VAST antennas are their mechanical stability over a given operational temperature range and with respect to any orientation of the gravity field. The mechanical design shall ensure extremely stable electrical characteristics allowing frequent travel and shall ease the handling of the VAST antenna (practical electrical and mechanical interfaces, well-defined alignment tools, low mass, attachment points for lifting, etc). The widespread use of the so-called VAST-12 antenna demonstrates the long-term value of dedicated test antennas. Currently, ESA is considering expanding its set of validation elements developing a VAST antenna at mm-waves. The frequencies considered are application driven: 20/30 GHz as up/down link of Ka-Sat, 38/48 GHz as up/downlink of Alphasat, thus, covering the Ku/Ka-band and the upcoming Q/V-band of telecom satellites. The paper will address requirements for future VASTs and possible architecture for multi-frequency Validation Standard antennas.