Wireless Puts Down Medical Roots

Sept. 20, 2005
As hospitals increasingly recognize the benefits of going wireless, opportunities are being revealed for a diverse range of engineering products, companies, and technologies.

Wireless-communications and other high-frequency technologies are increasingly revolutionizing the medical industry. The obvious applications for these technologies are the wireless local-area networks (WLANs) that are being installed in some medical centers. Of course, wireless communications also can be credited for keeping doctors "on call" for years. As the medical-technology field grows, however, new applications are being spawned almost daily. As a result, a host of semiconductor companies, service providers, and others are now focusing more of their efforts and developments on the medical field.

An example can be seen in the recent partnering of American Medical Response (Greenwood Village, CO) and American Emergency Vehicles (Jefferson, NC). Through a blend of wireless networking and information technology, their second-generation "Ambulance of the Future" extends local-area networking to emergency-medical-services (EMS) personnel in the field. To enable this communications infrastructure, AMR and AEV rely on In Motion Technology's (Fairfax, VA) Mobile Local-Area-Network (mLAN) technology. Through a secure virtual private network (VPN), In Motion's new onBoard Mobile Gateway 1000 transparently routes data traffic between the multiple devices in and around the ambulance and AMR's operations control centers. As a result, EMS personnel can work with the devices and applications to which they are accustomed while seamlessly connecting to the applications and data stored on servers at the office.

Verizon Wireless (Bedminster, NJ) also is looking to virtually expand a larger hospital network. It just teamed with PatientKeeper (Boston, MA) to help physicians gain access to patient information and applications from outside the hospital through the Verizon Wireless network. The PatientKeeper Platform, which features an open architecture, connects mobile devices with existing hospital information systems.

Both of these announcements work to make information and network applications available outside of the hospital or medical center. Such announcements will only increase with the growth of remote patient monitoring and other applications. At the same time, however, many companies continue to focus on wireless networking within the hospital. In fact, a company called PanGo Networks, Inc. (Framingham, MA) is using RF identification (RFID) to drill down even further into this network.

The company's goal is to save time and increase efficiency by performing asset tracking. According to studies, hospital workers spend a great deal of time tracking down wheelchairs, empty beds, and more. PanGo's solution offers to do this tracking for them. The PanGo Locator is a complete RFID solution that uses a business' Wi-Fi access-point infrastructure as a reader network. It therefore eliminates a separate and costly overlay of hardware and associated labor. The solution includes an application platform that integrates with third-party location technologies, an end-user application for asset monitoring and reporting, and web service interfaces for rapid integration into third-party or home-grown business systems.

The application provides the means to easily configure and manage RFID tags. In addition, map-based and tabular interfaces allow users to quickly find individual assets or groups of assets by location, type, owner, name, etc. This past spring, PanGo announced the availability of a joint asset-tracking solution that integrates Cisco System's 2700 Series Wireless Location Appliance with PanGo Locator 2.0. The 2700 Series Wireless Location Appliance product makes location an actual feature of the network. It also provides the means for third-party applications to access the location of devices connected to the wireless LAN. Lee Memorial in Ft. Myers, FL and a leading healthcare system serving eight hospitals are among the first customers to deploy the integrated solution.

A broader wireless hospital atmosphere can be created with help from Micrel (San Jose, CA). In June, the company introduced the MicrelNet free firmware stack. This firmware stack supports wireless networking with a star networking topology. The solution can be configured to operate as a basic star network to a complex multi-level, multi-cluster solution with repeat functionality. When used in conjunction with the MICRF505 and MICRF506 RadioWire transceivers, the MicrelNet firmware stack creates a wireless-networking solution for telemetry, building, and residential home control. The MICRF505 transceiver solution operates from 850 to 950 MHz. It supports FSK modulation at data rates up to 200 kb/s. The MICRF506 transceiver operates from 410 to 450 MHz and supports FSK modulation at data rates up to 200 kb/s.

The company also can satisfy the medical market with the newest addition to its QwikRadio family. The MICRF010 IC features the same high-performance as Micrel's MICRF009, but in a smaller SOIC-8 package. Its sensitivity is typically 6 dB higher than earlier eight-pin QwikRadio receiver ICs. This increase translates into a 50-percent rise in range. The solution offers quicker recovery from shutdown—typically 3 ms. The IC has a frequency range of 300 to 440 MHz and data rates to 2.0 kb/s (Manchester encoding). It provides designers with low power consumption (2.9 mA fully operational at 315 MHz).

Next month, AMI Semiconductor (Pocatello, ID) will announce a new member of its own IC family. The AMIS-53000 single-chip wireless solution is the latest member of the AMIS Application Specific Transmit and Receive IC (ASTRIC) product family. It incorporates application-specific features for wireless products targeted at the medical-implantable-communication-systems (MICS) markets. By delivering extensive frequency agility, the device allows designers to use the same part across a range of applications and geographies. For example, a product using the AMIS-53000 in the ISM bands can be programmed to operate at 915 MHz in the US and 868 MHz in Europe.

The AMIS-53000 has an operating voltage range of 2.2 to 3.3 V. Its operating-temperature range is the standard –40° to +85°C. The solution's operating frequency range is 300 to 928 MHz. The IC offers data rates of 1 to 19.2 kb/s (OOK) and 1 to 128 kb/s (FSK/GFSK). Its transmit output power is +15 dBm maximum (high power) and +0 dBm maximum (low power). It consumes transmit current of 50 mA typical (15 dBm). Receiver sensitivity is –115 dBm (OOK at 1 kb/s) and –105 dBm (FSK at 20 kb/s). The device's receiver current is 12 mA (continuous). The AMIS-53000's receiver linearity is +60 dBm for IP2 and +5 dBm for IP3. It has two RF output power ranges: +15 dBm maximum (high power) and 0 dBm maximum (low power).

This product reinforces AMIS' expertise in the MICS market. This past spring, AMIS announced a technology design and supply partnership with Interventional Rhythm Management, Inc. (IRM), which was founded by Synecor LLC (Research Triangle Park, NC). AMIS will provide low-power, mixed-signal, application-specific-integrated-circuit (ASIC) solutions that will be used in IRM's design for cardiac electrophysiology devices, such as implantable defibrillators and pacemakers. IRM's design allows defibrillators and pacemakers to be completely introduced and implanted within the vascular system without major surgery. The company's initial product will be an Intravascular Implantable Defibrillator (IID) that is designed for the prevention of sudden cardiac death.

Because the devices used in wireless hospitals have many of the same requirements as portable equipment, a sea of existing products can easily find uses in the medical market. One example hails from Fairchild Semiconductor (South Portland, ME). In May, the company introduced 11 IntelliMAX high-current (up to 400 mA), low loss (typical RDS(ON) = 0.120 ohms) load switches. Each FPF21XX device provides controlled switch turn-on to reduce in-rush current and supply transients, current limiting with device options (200 and 400 mA), and undervoltage lockout. To reduce excessive heating or system damage, the devices feature thermal shutdown. They also offer hard/short protection with fast response time (20 ns) for hard-short conditions. For nominal overcurrent conditions, their current-limit response time is 3 ms.

The devices flag for fault conditions with options for fault blanking, auto-restart functions. The optional reverse-current blocking feature offered by the FPF2108/09/10 devices ensures uni-directional current flow. In addition, all FPF21XX devices provide a low (<1-mA) shutdown current to conserve battery life. The devices operate over a wide input voltage range of 1.8 to 5.5 V.

A new I/O connector from AVX (Myrtle Beach, SC) also takes the portable-equipment route to medical electronics. The 9257-series I/O connector system was specifically spawned to meet dimensional constraints. The reduced-size connector plug offers cable termination with options of single- and double-sided contacts and single-row (8-way) or dual-row (16-way) plug connections. No latching is required due to the click design of the contacts. A standard SMT plug provides positive alignment and orientation of the plug and socket, ensuring a reliable and secure connection. The socket connector houses 16 contacts in two rows on 1.25-mm pitch with a 1amp per contact rating for 5000 mating cycles.

Although these wireless- and portable-related announcements are certainly impressive, many of the larger semiconductor companies are still focusing the bulk of their resources on medical imaging. Last month, for example, Motorola (Schaumburg, IL) announced a development agreement with Phiar Corp. (Boulder, CO). Their project will focus on the creation of next-generation electronic circuits, which can be incorporated with tiny antennas to deliver high-speed, millimeter-wave receive arrays. Because these receive arrays are expected to be low cost, they should be easily incorporated into high-speed applications like medical imaging.

Impressively, Motorola and Phiar plan to demonstrate circuits based on this new technology that are capable of running in the hundreds of gigahertz and potentially into the terahertz range. The joint development effort will utilize Phiar's metal-insulator technology with Motorola's millimeter-wave circuits and systems technology, modeling and simulation, device and circuit characterization, and advanced prototyping capabilities. Phiar's metal-insulator technology is compatible with multiple standards and substrates, giving it the potential to improve speed and simplify interconnects.

This summer also saw Texas Instruments' (Dallas, TX) most recent foray into the medical-imaging market. In June, the company introduced a clock synthesizer and jitter cleaner. The 3.3-V CDCM7005 offers low phase noise of –219 dBc/Hz (PLL figure of merit), maximum output skew of 20 ps, and low phase jitter performance of 162 fs (LVPECL) and 232 fs (LVCMOS). The output frequency is DC to 1500 MHz. The CDCM7005 includes serial-peripheral-interconnect (SPI) logic for programming and individual support control. To deliver high-frequency, clean clock outputs, it synchronizes a voltage-controlled crystal oscillator (VCXO) frequency up to 2.2 GHz (LVPECL) to one of two reference clocks. The outputs can be divided by 1, 2, 3, 4, 6, 8, or 16 divide ratios and delivered at LVCMOS and LVPECL levels. The temperature range for the CDCM7005 is –40° to 85°C.

A new logarithmic amplifier from Analog Devices (Norwood, MA) also targets medical-imaging applications. The AD8319 promises to accurately measure RF signals over the industry's widest frequency range of 1 MHz to 10 GHz. As a demodulating log amp, the AD8319 provides precise, temperature-stable performance over the full range of –40° to +85°C. It offers accurate RF measurement of better than ±1 dB over a dynamic range of 40 dB. The device can also be used as a power controller when its outputs are used to adjust a power amplifier (PA) or variable-gain amplifier (VGA). It operates over a supply voltage range of 3 to 5.5 V, consuming only 20 mA. That power consumption is reduced to less than 1 mW when the device is disabled.

The company also is targeting the medical-imaging market with a new VGA. For improved signal control, the AD8337 provides designers of industrial and instrumentation applications with a low-noise 0.5>, single-ended, linear-in-dB VGA element at frequencies up to 250 MHz (see figure). By offering low power per channel, the device claims to require 25 percent less power than competing VGAs. The AD8337 topology is an X-AMP structure (ADI's patented circuit technique). It boasts 24 dB of gain range and superior bandwidth uniformity across that entire range. The gain control interface provides precise linear-in-dB scaling of 20 dB/V and can be centered by an output common-mode adjust pin. Operating at up to 250 MHz bandwidth, the AD8337 is a very fast dc-coupled VGA. It boasts a high slew rate of 475 V/ms in a 2-V step.

To satisfy high-channel-count systems like positron-emission-tomography (PET) medical imaging, the AD8337 flaunts power consumption of 78 mW at ±2.5-V supplies. Dual supply operation enables gain control of negative-going pulses, such as those generated by photodiodes or photo-multiplier tubes. The part's output-referred dc offset voltage is less than 20 mV over the entire gain control voltage range of 24 dB. For any gain greater than 2, an integrated preamplifier at its input can be configured with external resistors. That preamplifier allows both inverting and non-inverting topologies, enabling a dual-polarity VGA. The AD8337 also flaunts low output-referred noise of 34 nV/(Hz)0.5.

Clearly, hospitals are increasingly going wireless thanks to a plethora of products and categories that cannot be contained in a singular article. Such capabilities require products of every kind—from amplifiers to materials, cables, components, and more. These products must team to create systems for applications like imaging, wireless medical telemetry, low-power radio service, medical implant communications, and the latest in medical networking. Sensor networks, for example, are being examined as a solution for pre-hospital and in-hospital care and even rehabilitation. As these application areas grow and attract more engineering firms, innovation will only increase. The resulting hospitals, medical centers, and connected entities will be more efficient, organized, and able to focus on their core competencies: helping people heal and saving lives.

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