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Short-range communications in the 2.4 GHz frequency range offers many benefits, such as low power, noise immunity, widely available modular components that make integration much less challenging, and worldwide homologation. Zigbee offers a high reliability, low cost, and low power communication option but at lower bandwidth than Bluetooth. Bluetooth is a widely used standard in portable devices, such as cell phones. BLE (Bluetooth Low Energy) was introduced in 2006 under the name Wibree and merged into the Bluetooth standard V4.0 in 2010. BLE targets very low power applications utilizing coin cells. Today BLE is marketed as Bluetooth Smart. (See Figure 1)

Embedded Antenna: The antenna used for your RF design may or may not play an important role in the overall device performance depending on the distance requirements. The farther the communications needs, the more critical the antenna design will be. Space considerations often are a major handicap for a proper antenna implementation lacking suitable ground plane and physical length to achieve a full 1/4 wavelength. At 400MHz, the antenna should be approximately 7" long, while at 2.4 GHz, the antenna length can be approximately 1.2". Many boardmounted antennas are commercially available, but space considerations often make them impractical, leaving the engineer with a PCB trace as the antenna solution. If performance is critical, engage an antenna design consultant with experience in embedded antenna design.

Regulatory: All devices with a clock circuit must pass FCC/EMI/RFI testing and be included as part of your FDA 510(k) submission. Most of this is covered in the IEC 60601 standard, but be aware that part 11 of the standard deals with homeuse devices and places even more stringent requirements on emissions. Devices that contain RF communications must be further qualified by the FCC and carry an RF device ID. Your compliance requirements can be greatly lessened by integrating RF modules with a recognized module ID. With this, only RF screening with the production equivalent antenna is needed for filing with the FCC.

Board Classification: Quality standards exist for printed circuit board assemblies (PCBAs) and the classification specified. This will have an impact on the cost of the board and, therefore, the product. High reliability products that may be used in life support are classified as Class III. Most medical devices fall into a Class II requirement, allowing the PCBA manufacturer more latitude in its inspection criteria, which can reduce manufacturing costs.

Software/Firmware: The vast majority of intelligent medical device recalls are due to software issues. As a result, there are very stringent requirements on the development and testing of all elements in the software development process from module testing (referred to as Unit Testing), to integration testing, and finally complete system testing. This overhead to the development process is significant, but a necessary part of creating software design resulting in a robust, intuitive, and reliable finished product. FDA, IEC, and ISO standards and guidelines apply.

Manufacturing Considerations

Medical devices containing electronics also face strict adherence to device integrity and compliance when being manufactured. Process repeatability and validation, material component analysis, regulatory, shelf life, device handling due to electrostatic discharge (ESD) issues, supply chain management, and assembly all are factors to be addressed prior to the manufacturing stage. (See Figure 2) Manufacturing considerations when dealing with electronic integration include the following.

Fig. 2 – Designing products to include electronic integration requires a knowledge of user needs, available technology and technology limitations, as well as understanding of the complicated maze of regulation that control these products.
Medical devices with electronics often have a shorter shelf life than their non-electronic counterparts. The FDA’s regulations and policies relating to the shelf life of medical devices identify parameters that determine the stability of the device over time. Identifying shelf life early allows for accuracy in the timeline for manufacturing, storage, shipping, and distribution to the end user, and avoids further demands and tests.

Process repeatability and validation are critical to manufacturing medical devices. The development of an automated production line can be a key benefit: a repeatable validated process, precise assembly methods, less “human” touch, and overall product quality improvement.

When handling and assembling devices with electronics, manufacturers need to understand ESD issues. Sensitive medical devices must be supplemented with ESD control measures for incoming inspection, in-process handling and assembly, and final packaging.

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