The radiation patterns of antennas and arrays are traditionally measured in anechoic chambers. The size of the chamber, its architecture and the quality of the surrounding absorbers all affect the chamber's frequency range of operation and the accuracy of the measured results. For example, in order to characterize an HF antenna operating at 40MHz, you need a very large and deep anechoic chamber several meters long. Anechoic chamber facilities are very expensive, require a large space and are hard to operate and maintain. Compact ranges are smaller replacements for full-sized chambers.
Near-field scanning systems are by far the most compact alternatives for antenna pattern measurement. Yet, conventional near-field scanning systems have substantial downsides. These systems involve metallic radiators that act as receivers for picking up the near field of the antenna under test (AUT). Such metallic pick-up antennas cannot get close to the AUT since they would perturb its near fields. They also limit the operational bandwidth of the system, and their accuracy degrades significantly at lower frequency bands. Sophisticated software tools error correction and compensation algorithms are often used in conjunction with these systems to de-embed and minimize various errors due to their specific architectures and configurations.