Designing Connected Medical Devices: Overcoming Key RF Challenges

Understanding the key design, performance, and certification issues involved in connecting medical devices can help eliminate many of the challenges facing medical device manufacturers, and direct them down the correct path.

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As medical devices become more sophisticated and are marketed as “wellness devices” instead of medical equipment, their form factor is also shrinking. That’s making Internet of Things (IoT)-based medical devices even more popular with patients who don’t want or need to be tethered to a hospital or healthcare facility for real-time monitoring. Analyst firm Berg Insight says in 2016, 7.1 million patients enrolled in some form of digital health program featuring “connected” medical devices as a core part of their care plan. Berg expects the number of remotely monitored patients will reach 50.2 million by 2021, with 22.9 million patients expected to use Bring Your Own Device (BYOD) connectivity, preferring to use their own mobile devices.

The variety of devices is also growing significantly. Cardiac monitoring devices, insulin pumps, defibrillators, CPAP machines, and other devices are becoming more prevalent as equipment that can be remotely monitored, providing patients and their caregivers valuable real-time information.

IoT-based medical devices, of course, need to connect to the healthcare cloud, and that means they need a reliable antenna and RF system, which serves as the physical link to network connectivity, converting electrical signals into radio waves for transmitting and the opposite for receiving. An efficient, reliable antenna is critical, not only for connectivity in areas with weak signals, but also to avoid too much drain on the device’s battery.

As devices become more sophisticated and smaller, however, complexity and challenges arise. These include—among others—challenges in product design and performance, but also in achieving the required certifications from not only governing bodies such as FDA and FCC in the United States, but through mobile network operators (MNOs) as well.

Design Challenges

Designing a product for in-home or on-the-go usage means form factor is critical, and space is at a premium. Medical devices previously designed for in-facility use have the advantage of decades of design experience to improve form factor and usability. Much of that experience can be thrown right out the window when it comes to new connected medical devices.

A common mistake is trying to retrofit previously unconnected medical devices simply by adding cellular capabilities, but keeping the enclosure, battery size, main PCB shape inside, and other elements the same. Antennas need space to radiate efficiently, so merely trying to fit an antenna in a device not originally designed for such generally won’t work, unless that device is large and has an area of free space. Connected medical devices usually need a custom design and bespoke integration that includes consideration for the “discreet” factor; if the devices are worn on the body, they also need to be compact and comfortable, or they won’t be worn by the patient they are intended to help. To find success, medical device companies should plan for antennas at the beginning of the design process to ensure that the device will meet certifications and user expectations when tested.

Performance and the Certification Process

Connected medical devices need to meet certifications and a certain level of network performance. The wireless device certification process is a critical factor for companies looking to bring connected devices to market—and the process is often underestimated. Regardless of whether a device is new or is an existing device that the manufacturer is trying to connect, it must undergo a stringent certification process with the FCC or CE. If cellular connectivity is used, it must also be certified by the mobile network operator. For these tests, medical devices are tested on several criteria, including:

  • Meeting certain network standards and scenarios
  • How well they send and receive data
  • How weak a signal they can receive while still being connected

This testing for device transmit and receive sensitivity is known as Over the Air (OTA) testing.

Devices that are worn on or near the body drastically affect the antenna and RF system, so the manufacturer will need to consider the potential for extra testing and certification, such as SAR (Specific Absorption Rate)—especially if there are voice or heavy data functions for the application. The SAR testing for such devices is tough to pass if it is not a device that is deemed as a work tool—for example, a first responder communications unit or an electrical utility worker’s safety device.

Ensuring that medical devices are equipped with the right antennas to deliver robust cellular connectivity is vital for the devices to pass the required certifications the first time so product launches do not face delays.

Other issues include:

  • Noisy electronics and activity in proximity to the RF and wireless system will cause interference and impact performance. Custom antenna and filter designs can help compensate for these effects.
  • Medical devices may also be battery powered, and power consumption is often a critical factor. Best practice RF design must be utilized to minimize noise and interference. Efficient antenna performances are needed so the device is not losing power when receiving or transmitting.

Partnering Up for Success

Manufacturers of medical devices can easily underestimate the complexity of integrating wireless into a product that is already complicated, so partnerships—and constant communication before and during the device build process—are very important. Trusted partners may include the MNOs, antenna and RF vendors, module or chipset vendors, and test labs. They can help manufacturers understand:

  • Best practice wireless device design
  • How to successfully deploy devices in any location globally
  • The full range of connectivity options available, including cellular, low-power options such as LPWAN, or satellite
  • How to avoid the common pitfalls of the device certification process

Understanding the key design, performance, and certification issues involved in connecting medical devices can help eliminate many of the challenges facing medical device manufacturers, and direct them down the correct path. Involving an antenna supplier early in the process means they can help with antenna size, shape, mounting type, location, price, and other factors, and well as with carrier certification, testing plans, installation requirements, and other potential road blocks that can stall or even halt projects.

Dermot O'Shea

Dermot O’Shea, cofounder and joint CEO of Taoglas, is a seasoned IoT entrepreneur, with more than 15 years of experience in the global electronics industry spread over roles in Europe, Asia, and North America. He is recognized as an expert in the antenna and wireless business. O’Shea currently serves as Joint CEO of Taoglas Group and president of Taoglas USA—the leading machine-to-machine/IoT antenna solutions provider.

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