Since the onset of the COVID-19 pandemic, the diagnostic testing, medical equipment, and healthcare professional communities have shifted much of their focus to temporary facilities requiring radio-frequency (RF) and microwave-dependent communications and diagnostic systems. The overwhelming demand for community-based testing (over 30,000,000+ tests administered to date) was further complicated by the fact that most testing needed to be accomplished in temporary field sites.

The sudden surge of hospital inpatient volume taxed the established healthcare system beyond its capacity and necessitated the temporary establishment of COVID-specific treatment/testing locations in such unlikely venues as convention centers, public parks, and military installations. The challenge was that these critical diagnostic and treatment centers were dependent on efficient connectivity to other temporary facilities, i.e. labs, hospitals, and government agencies. This ultimately created a critical and unprecedented demand for mobile and wireless communications, along with the urgency for wired equipment networks in larger temporary treatment locations.

Interconnect Requirements

RF performance parameters should be determined by the end user and validated during the cable assembly’s production process. (Credit: CDM Electronics)

It became evident within days of the coronavirus pandemic outbreak in the United States that the need for state-of-the-industry communications was urgent. Due to the remote nature of many of the newly established diagnostic and treatment facilities, connectivity was required for cellular networks to link hospitals’ and temporary locations’ Wi-Fi access points. This involved the immediate installation of temporary networks and/or the employment of satellite antenna systems.

Robust connectivity was integral to the accuracy and efficiency of remote testing and pop-up acute treatment facilities. Connectivity capabilities, optimized to ensure consistent signal transmission and reception, were wholly dependent on the durability and reliability of such interconnection components as RF interfaces, specialty RF connectors, cables, and cable assemblies.

In addition to prioritizing signal integrity, interconnect providers were faced with the challenge of establishing network equipment and/or antenna systems in less-than-ideal/harsh environments. Their task was made even more difficult by the need to get systems operational ASAP. This too frequently resulted in faulty installations by personnel not adequately trained in mission-critical communications equipment and/or network connectivity.

U.S. military personnel assist the medical community in construction of mobile testing facilities. (Credit: CDM Electronics)

Cable, cable assembly, and connector suppliers quickly recognized that products intended for remote network equipment and/or antenna systems needed to be easy to install and ruggedized. To address this, value-added cable assembly manufacturers specified flexible coaxial cables with a minimum bend radius of not more than 10X the overall cable diameter. This bend radius is considered ideal for routing cable assemblies around and through an array of obstacles in nonpermanent applications. IP67 (or higher rated) interconnect or termination sleeves as well as self-sealing coaxial cable were also specified to maintain structural integrity in case the assembly jacket was compromised.

Temporary medical facilities require mobile, wireless, and sometimes wired network communications. (Credit: CDM Electronics)

Notably, many cable assembly providers began to observe an increased number of customers now requiring Mil-Spec components in their commercial RF interconnect devices. This new initiative is widely believed to be in direct response to the markets’ heightened awareness of the critical need for durable connectivity. The employment of Mil-Spec components ensures that RF performance parameters more accurately validate frequency range requirements and determine that insertion loss is within specification. Mil-Spec mechanical testing applies to such requirements as tensile strength and pull testing (terminations and entire assembly), radial torque, and moisture resistance/humidity testing. It can further be used to identify mishandling of the interconnections.

Unique RF Interconnect Requirements

Many connectivity requirements for these applications mirror those of temporary field wireless and satellite communications; however, temporary diagnostic, treatment, and patient-monitoring applications necessitate a particular focus on RF performance. In addition to the specification that coaxial cables call for, a minimum bend radius of not more than 10X the overall cable diameter, best practice is to validate the frequency range. Most systems typically operate within the industrial, scientific, and medical (ISM) radio bands of 900 MHz, 2.4 GHz, and 5.8 GHz. Other considerations for validation are time domain/time delay, insertion loss, and VSWR (voltage standing wave radio.) Peak performance is further ensured when cable assemblies are phase matched during the manufacturing process.

Again, an increasingly common alternative to conventional commercial specifications is to employ Mil-Spec mechanical testing requirements. These specialized testing prerequisites need be administered and documented by the cable assembly provider to ensure that assemblies are certified to ISO standards. Choosing a supplier that is military and aerospace accredited (AS9100D, Nadcap, etc.) is suggested.

It should further be noted that diagnostic imaging systems such as ultrasound, CT scan, and advanced radiography equipment require a significantly larger and more robust set of RF interconnects and coaxial cables and have their own a distinctive set of challenges.

Evolving RF Technology

Pop-up testing locations depend on ruggedized and reliable interconnects. (Credit: CDM Electronics)

Most commercial off-the-shelf wireless components and assemblies are not optimal for integration into medical devices as they often do not comply with the requirement for nonmagnetic materials. While single metal plating has been used for many years, “white bronze” or tri-metal (Tri-M3) has become a widely accepted, cost-effective alternative.

Tri-metal (composed of copper, tin, and zinc) plating features low electrical resistance, superior corrosion resistance, nonmagnetic properties, and extremely high hardness characteristics to support superior overall equipment performance and durability. Moreover, it supports low-PIM performance (passive intermodulation) to ensure minimal noise within the cable or subassembly, especially important in medical connectivity applications. PIM performance can be specified and quantified during the cable or subassembly process.

Wireless product development, including technology optimized for teleradiology, will focus on robust performance and 100 percent shielding to avoid dropped connections, time-outs, and data re-tries caused by external factors compromising the quality of the interconnect. It is now more important than ever to rely on the experience and expertise of a manufacturing partner that delivers cable assemblies certified to ISO standards and is military and aerospace accredited.

This article was written by Robert Grzib, CDM Marketing Manager, CDM Electronics, Turnersville, NJ. For more information, visit here .