Environmental testing is a crucial part of antenna qualification. Depending on which application(s) an antenna is to be used for, the environmental qualification standards for which it has to pass will vary.
JEM Engineering qualifies both our own and our customers’ antenna products in a number of ways, including testing them in at least one of our in-house chambers. Both the Tapered Antenna Test Facility (TATF) and the Spherical Near-Field (SNF) chambers perform a number of measurements at varying frequencies. While these measurements indicate an antenna’s RF capabilities, the antenna is not fully qualified until it is rugged enough for long-term practical use.
Each of JEM’s qualified antennas is a product of a collaborative effort between both electrical and mechanical engineers. For example, the electrical engineer designs the printed circuit boards (PCBs) and various radio frequency components, whereas the mechanical engineer designs the product’s housing, as well as additional internal components that would allow the unit to withstand various environmental conditions. Additionally, the RF test technicians collect quantitative information pertaining to the antenna’s electrical design, while the mechanical engineer must put the unit through rigorous environmental testing, including shock, vibration, heat, immersion, humidity, chemicals, wind, and frost.
There are a number of different standards by which an environmental test may be performed, but because JEM Engineering is a contractor for the United States Department of Defense, we adhere by defense (or “military”) standard, also known as “MIL-SPEC.” While JEM Engineering does not have the capability to perform environmental testing in-house, we work closely with our trusted partners, who handle our required MIL-SPEC tests once we’ve designed and built any necessary fixturing for them.
MIL-SPEC environmental tests are classified by codes. For example, MIL-STD-810 Method 516 measures shock, at values ranging from as low as 20G’s to as high as 75G’s. Similarly, MIL-STD-810 Method 514 denotes a vibration test. Some tests take into account a combination of atmospheric factors. An example of this is MIL-STD-810 Method 520, which involves quantifying the temperature, altitude, humidity, and vibration a product can withstand.
Lastly, for a general overview on what processes are involved in qualifying antennas, you may refer to our blog post, The Makings of a Reliable Antenna.
Like with most products, an antenna’s outstanding performance in the field must be preceded by outstanding performance in the lab.
It is JEM Engineering’s job to not only design and manufacture antenna products, but also to qualify them to meet RF specifications, as well as environmental standards such as military standard MIL-STD-810 and RTCA/DO-160. Because of this, not only do our products survive strenuous environmental conditions; they perform well. We extend the same guarantee to our customers by offering them the same qualification services.
Our rigorous qualification procedures combine our own internal testing capabilities with those of our external testing partners. In this post, we list some of our in-house qualification capabilities.
Efficiency Measurements – The radiation efficiency, or simply “efficiency” of an antenna is commonly defined as the ratio of the power radiated from the antenna, in relation to the power delivered to the antenna. JEM’s Spherical Near-field Chamber (SNF) and Tapered Antenna Test Facility (TATF) chambers generate efficiency plots, in addition to as addition to radiation patterns, and ASCII Data Files.
Directivity Measurements – Directivity is one on of an antenna’s key performance factors. One can define it as the ability of an antenna to focus energy in a particular direction when transmitting. Directivity also measures the antenna’s ability to receive energy better from a particular direction.
Gain Measurements – Another useful performance measurement is the antenna’s gain. It combines the antenna’s efficiency with its directivity. The gain measurements we provide as part of our data package include peak, average, maximum linear, minimum linear, horizontal, and vertical, as applicable. Additionally, SNF and TATF chambers generate gain measurements for antennas within two different frequency ranges. The SNF measures from 400 MHz to 6 GHz , while the TATF measures 80 MHz to 40 GHz.
VSWR and Return Loss – Voltage standing wave ratio, or “VSWR,” is a measure that describes how well the antenna impedance -or voltage to the current at the antenna’s input- “matches” to the radio or transmission line it is connected to. A good match allows a transmitter or receiver to deliver power to an antenna without excessive reflection back on the line (return loss). At JEM, a single VSWR measurment, including system calibration, takes less than 10 minutes. In fact, minus calibration, it only takes 1 minute or less to complete a test!
Radiation Patterns – An antenna’s radiation pattern measures the strength of its radio waves in relation to the direction at which the waves travel. We can generate both 3-Dimensional, as well as 2-Dimensional renderings of radiation patterns.
Steered Array 3-D Pot
Steered Array 2-D Plot
Human Body Interaction – Besides producing full-spherical radiation patterns, our SNF chamber can accommodate a human test subject. This allows us to take accurate measurements of body interaction effects on body worn and handheld devices.
JEM Engineering technicians testing a wearable antenna in our SNF chamber in Laurel, MD
Temperature Effects – Temperature testing allows us to determine how a complete product, its parts, and its sub-assemblies are affected by extreme temperatures, as well as changes in temperatures. Consequently, this also allows us to assist customers in analyzing the cost effectiveness of manufacturing a product and using its components.
Simulations – Our team of experts has access to advanced simulation software, therefore, allowing us to measure in-situ performance, and eliminating need to run a physical test.