Flexible Antenna Offers Efficiency, Design Freedom to Remote-Monitoring Devices

Advancements in remote monitoring technologies are spurring progress in the home healthcare market to the extent that Frost & Sullivan predicts it will be a $428.6-million industry by 2015--and that's just for North America. But as medical device manufacturers clamor to make their mark in this lucrative market, they are faced with the challenge of wedding medical device design requirements with high-tech monitoring and wireless data-transfer needs. Drawing from its expertise in wireless industrial controls, cell phones, and GPS systems, Taoglas may be able to help. The company has introduced what it maintains is the first flexible-circuit loop antenna for the medical device market.

Although engineered for medical devices, the penta-band FLA .01 is inspired by a cell phone antenna design. Rather than using traditional antenna materials such as ceramic or metal, Taoglas makes the flexible circuits from Kapton, which lends flexibility and temperature stability to the product. The flexible material also allows the antenna to radiate at higher frequencies typically used for cellular and Wi-Fi applications, says director Dermot O'Shea. Operable frequencies include 433, 868, and 915 MHz, as well as 2.4 GHz and higher.

"Another feature of the flexible antennas is that they're really thin and they give you flexibility in the design, so they can be simply mounted directly onto an enclosure or they can be placed on the edge of a PCB," O'Shea notes. In the interest of design freedom and flexibility, however, the antennas can also be integrated into existing designs. "With a flexible antenna, [OEMs] can take that same format and adhere the flexible material to the enclosure and simply use a cable and connector to attach it to their circuit board."

In addition to being flexible, the medical device-optimized product is a loop antenna. "That means it creates a loop of current around the main circuit board," O'Shea explains. "It will use the device circuit board as the antenna ground plane. Essentially, the antenna ground plane is part of the antenna and it uses that to radiate energy more efficiently." And higher efficiency can translate into reduced power consumption, improved reception, and greater transmission sensitivity. In fact, Taoglas claims that its antenna boasts more than 40% efficiency in monitoring devices, compared with 20% demonstrated by standard, off-the-shelf antennas.

The company's product is also less vulnerable to detuning than conventional antennas, according to O'Shea. Noise, emissions, and radiations from surrounding components or the human body can detune antennas, consequently shifting the frequency out of band and causing the medical device to lose critical connectivity. But because the radiating element is embedded in the loop antenna and it communicates in the magnetic field, the FLA encounters reduced exposure to interference produced by the components and body, which tend to operate in the electric field.

"There are two unique features here: The flexible material and the electrical properties of the loop," O'Shea concludes. "Both allow the antenna to be more resistant to the effects of the body so it can remain more stable in a medical device product than other antennas on the market."