SNIFT – Precision measurements of antennas, a new era starts!
Antennas are often used for communication over long distances. Before the 1970s, measurements of an antenna radiation pattern were traditionally made in the so-called far field, at a distance far away from the antenna under test. This can potentially cause inaccuracies, and the practical aspects of the measurements may also be challenging. Some of the problems can, however, be avoided if the measurements are carried out in a shielded anechoic room. For antennas that are large in terms of wavelength it will then be the near field, which is measured, and this is different from the desired far field.
Professor Jesper E. Hansen – one of TICRA’s founders – had found that from an antenna measurement in the near field, an expansion of the data in spherical vector waves could be made, and with this expansion, the sought-after antenna far field could be determined. This became the topic of the licentiate study by Frank Jensen at DTU which he finalised in 1970. The method was later improved upon and extended by Flemming Holm Larsen, also at DTU.
Flemming’s work resulted in the first practical implementation of an algorithm for probe-corrected spherical near-field antenna measurements in 1977. In 1982, the program was made available to TICRA’s customers under the name SNIFT. During its lifetime, SNIFT has undergone several extensions and improvements. Now, almost 40 years later, it is still being provided to TICRA’s customers and is used every day at a great number of antenna measurement facilities around the world.
A detailed exposition of the mathematical foundation of the SNIFT transformation algorithm, as well as spherical near-field antenna measurements in general, is presented in the book Spherical Near-field Antenna Measurements by Jesper E. Hansen. This excellent work is still considered the go-to reference for both experienced and aspiring antenna engineers involved with spherical near-field measurements.