Over the past several years, rapid changes have taken place in the field of antenna testing. With more antenna types and new applications emerging at higher frequencies, there is increased urgency to refine established test strategies and develop new ones. For those who are new to antenna testing or are just getting reacquainted after several years away from the practice, it can be instructive to brush up on the fundamentals of antenna testing and study recent trends.
THE BASICS
The basic methods of antenna testing have not changed substantially, but the options for how and where to test antennas have shifted. The options enable various levels of cost, convenience, accuracy and sophistication. In particular, compact antenna test ranges (CATRs) are more widely available and operate at higher frequencies, up to 330 GHz or beyond.
For antenna measurements above 100 GHz, many CATR designs can be customized for specific waveguide bands by selecting different vector network analyzer (VNA) frequency extender modules and suitable feed antennas. For example, Eravant offers an open CATR with reflector options of 300 × 300 mm or 600 x 600 mm, as shown in Figure 1. These CATRs are available with VNA frequency extenders and feed antennas operating up to 330 GHz.

Figure 1 Eravant CATR.

Figure 2 MilliBox MBX32CTR CATR.
MilliBox has developed a series of CATR designs using modular anechoic enclosures. The MBX32CTR CATR from MilliBox provides measurement solutions for frequencies up to 330 GHz, as well. An example of their test range is shown in Figure 2.
Rohde & Schwarz provides a selection of mmWave CATR designs that feature shielded anechoic environments. Figure 3 shows a Rohde & Schwarz CATR with a shielded enclosure surrounding an anechoic chamber. Other commercially available antenna ranges include many traditional far-field ranges, as well as a variety of near-field (NF) scanning systems. Figure 4 shows a planar NF system from ASYSOL. The ASYSOL systems, along with others, typically operate at frequencies from microwave to mmWave bands.

Figure 3 Rohde & Schwarz ATS1800C CATR.

Figure 4 ASYSOL planar near-field system.

Figure 5 Quadsat drone for airborne antenna measurement services.
For those requiring only occasional antenna tests, one of the most common strategies is to use someone else’s antenna range. At first glance, this can seem like an inconvenient and expensive option until the time and cost of acquiring and maintaining a suitable antenna range is appreciated. Gaining experience using a variety of antenna ranges is one of the best ways to become familiar with current practices and equipment. Many companies offer economical antenna testing services, with some bringing their test equipment to the antenna rather than the other way around. For example, Quadsat provides airborne antenna measurement services for high gain outdoor antennas with drones. A Quadsat drone that provides these services is shown in Figure 5.
At the high end of the cost and complexity spectrum, complete antenna test ranges are available with fully engineered anechoic chambers, positioning systems, computer platforms, software and test equipment. A wide variety of configuration options can tailor antenna ranges to meet specific needs. Configuring a complete antenna range requires a team with advanced knowledge to perform tasks related to design, planning, construction, calibration, operation and maintenance.
Less complicated and lower-cost solutions are also available. Antenna range components like anechoic chambers, positioning systems, test equipment and software can be developed in-house or purchased individually. A list of companies in this space, along with the products and services offered by these companies, is shown in Table 1. Companies that supply these components can provide expert advice based on specific testing needs and they may refer customers to existing facilities to serve as points of reference. In general, the antenna testing community is open and cooperative on all levels, making it one of the most rewarding career paths available. Its participants span a diverse range of skills and interests.
