What are Body Worn Antennas?

Body Worn Antennas (BWAs) are antenna modules that are primarily designed to be worn by soldiers in the field. The antennas have been specifically designed to be used on the body. They can be placed into or under clothing or placed against the skin. BWAs replacements to the traditional vertical omnidirectional antennas and bring several improvements that help overcome challenges faced by military personnel.

Vertical omnidirectional antenna being carried by a soldier

Traditional omnidirectional antennas have been used by the military for decades. Although they are quite simple and have a very basic design, they are bulky, difficult to conceal, limit maneuverability, have low gains with low efficiency (see image above).

Covert body-worn antennas are designed to tackle these challenges. They are required to be small and low-profile to not blow the cover of the soldier and simultaneously provide high performance. BWAs also need to have excellent shielding from nearby electronics equipment such as phones, computers and other RF devices that a soldier might be carrying or have integrated into their uniform/suit.

Low Profile

Body worn antennas have a low-profile design which is crucial in a real-world operational environment. Since they are compact and do not stick out of the uniform, they prevent soldiers from becoming easy targets on the battlefield. BWAs also increase maneuverability of military personnel as they are not bulky and usually integrate into the military uniform. 

Coverage

BWAs generally utilize two methods of providing coverage. They either use a single antenna or multiple sector-antenna radios to create a field in the area. The single antenna implementation is basically an omnidirectional antenna which is placed on shoulders below the head. The multi-radio setup works like cell towers which utilize multiple directional antennas to provide 360-degree coverage. For instance, four 90-degree antennas can be combined to create a field identical to an omnidirectional antenna.

Higher Performance

Body worn antennas have significantly higher gains with higher efficiency and deliver a better performance overall. Using multiple radios also help in increasing the coverage area along with providing a better and more efficient radiation efficiency. They are also designed to be used very close to the body, as the name suggests, to ensure minimal signal absorption and signal attenuation.

Antenna performance relative to distance from body (Source: L3Harris)

The above diagram shows the human body, clothing and armor. The antenna (blue rectangle) can be placed anywhere from Small Arms Protective Insert (SAPI) to any distance away from the body. The Specific Absorption Rate (SAR) of the human body is inversely proportional to the distance between antenna and body, whereas the gain (or efficiency) is proportional to distance away from the body. This means the further away an antenna is from the body, the lower the absorption and higher the gain. The antenna must be far enough from the body to be past the SAR limit as set by the IEEE C95.1 standard, as a minimum. The maximum distance for a realistic case would be 100 mm.

Redundancy

Redundancy is another huge advantage of using multiple radios in body worn antennas. Using multiple radios ensure that failure of one element will not affect the performance of other radios and will only hamper the quality of communication rather than stopping it altogether. It is also easier to carry additional radios as they are quite small and can be replaced easily in case of failure.

A multi-radio setup body worn antenna with radios on each side of the body (marked in red)

Body worn antennas are being increasingly used by various military forces because of their low profile and better performance. They are robust and less prone to snagging which is always one of the primary requirements for military applications and their market is anticipated to grow over the next few years.

These antennas have also found applications in non-military applications such as law enforcement and animal monitoring. Click here to find body worn antennas from the leading manufacturers on everything RF.