Bullet Sensors & Transducers e-Digest, Vol. 51, Issue 1,  January 2005: Product News

    (ISSN 1726- 5479)


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Ultra-Low-Power Radio Architecture Provides Scaleable Platform 

for Medical Implant Applications



Cambridge UK and Boston MA, January 18, 2004 - Cambridge Consultants has designed an intelligent radio transceiver optimized control-and-communications ASIC architecture that introduces a new level of power economy and performance for in-body medical diagnostic and therapeutic applications. The design is intended for implementation on system-on-chip (SoC) solutions and provides a control and communications platform suitable for implantable medical devices - a market currently growing at double-digit rates. The device will operate in the Medical Implant Communications Service (MICS) frequencies - the medical band now emerging as a global standard. 


A key attribute of Cambridge Consultants' design is exceptional power economy, and the architecture would consume an average current of less than 1A, and less than 1.7mA peak, for a 0.05% duty-cycle, 400 kbits/second bi-directional communications application. This would provide more than 10 years of activity from a lithium cell in a typical pacemaker application for example. However, flexibility built into the radio design also allows the chip to be used for other systems with short-term high data rate communications requirements - such as swallowable video imaging.


"Advances in electronics technology are enabling a host of new implantable applications, and this design draws on three of those trends: ultra low power consumption provided by cost effective CMOS/BiCMOS processes, enhanced radio performance through lean microcontroller and low-power DSP digital cores, and extreme miniaturization enabled by system-on-chip integration capabilities" says Richard Traherne, head of Cambridge Consultants' wireless business unit. "Combined with the opportunities offered by the MICS frequency allocation - which is emerging as a worldwide standard endorsed by the FCC and ETSI - we see great demand for an optimized single-chip wireless platform that delivers the economy required for mass-volume medical applications".


The new implantable transceiver design, called SubQore, leverages Cambridge Consultants' portfolio of field-proven intellectual property for ultra-low power radio, as well as the consultancy's lean RISC processor core, XAP. Extreme attention to power economy has been applied throughout the design, both to consumption in the transceiver architecture, as well as the power-saving algorithms that are employed to wake up and control the device.


Although the range of implantable medical applications is expanding exponentially, each application is different and requires a particular mix of control, monitoring and communications facilities - and Cambridge Consultants expects to fine-tune the IC core for individual applications.


SubQore's architecture reflects this diversity of potential use. In its basic form, SubQore's radio employs digital phase-shift keying (PSK) data modulation - a highly power-efficient scheme. However, the hardware that controls modulation has been designed to provide a degree of DSP (Digital Signal Processor) flexibility, to support the use of higher-efficiency schemes for more demanding applications such as video transfer. The XAP microcontroller core provides similar flexibility, and can be equipped with a range of digital and analog I/O - and memory sizes - to suit the application.


The SubQore radio operates in the 402-405 MHz 'MICS' (Medical Implant Communications Service) frequency band - compatible with new FCC and ETSI standards - and offers a communications range of 6 feet/2 metres when implanted under the skin. The only other use of this band is for meteorological equipment, minimizing the potential for interference and providing an excellent platform for economy of scale through standardization.


The low-IF (Intermediate Frequency) radio receiver architecture employed in this design, adapted from high-efficiency pager technology, offers lower power consumption and better immunity to interference than direct conversion receivers. SubQore is also optimized for physical compactness and requires just 10 components, enabling subcutaneous radios to be the size of a button using system-on-chip technology.


Among the applications that Cambridge Consultants sees for high-performance/long-lifecycle MICS cores are implantable pacemakers, defibrillators, remote telemonitors, orthopaedic devices, pump controllers, nerve stimulators and swallowable imaging and diagnostic systems.


Cambridge Consultants has a long track record in wireless applications, working from the IC and silicon level for low-power embedded radio, through to the design of complete wireless devices such as an ambulatory monitoring transceivers. Its portfolio embraces standards such as GSM, Bluetooth, 802.15.4/ZigBee and DECT, as well as application-specific designs for medical device projects such as ASICs for pacemaker and ECG monitoring equipment. This work has previously led to the spin-out of successful wireless-oriented companies, such as CSR (Cambridge Silicon Radio) and Alphamosaic. In addition to wireless expertise, Cambridge Consultants has a library of digital silicon IP including processor and DSP cores optimized for low power applications, and a library of analog intellectual property that has been proven on major silicon foundry processes around the world. These elements provide further essential ingredients for single-chip wireless solutions, as control is typically required in addition to a radio.


Barrie Nicholson,

Cambridge Consultants Inc.,

451 D Street, Boston MA 02210, USA

Tel: +1 617 532 4700, fax: +1 617 737 9889




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