Cambridge Consultants has designed a new ‘control and communications’ radio architecture for in-body medical diagnostic and therapeutic applications. Called SubQore, it supports medical device manufacturers’ drive for implantable devices which combine very low power requirements with robust wireless communications.

Cambridge Consultants' design combines exceptional power economy with great flexibility. In a typical pacemaker for example, SubQore would deliver more than 10 years of activity from a lithium cell. But it’s equally capable of meeting short-term requirements for high volumes of data, in a swallowable video imaging device for example.

The implantable device market is currently growing at double-digit rates: wireless communications have added a valuable new dimension to in-body therapeutic devices, and enabled a whole new generation of diagnostic aids. For device designers, the challenge is to exploit these new capabilities within extreme size constraints, and with minimal power requirements. SubQore is designed for implementation on system-on-chip (SoC) solutions, to provide a tiny control and communications platform suitable for devices using Medical Implant Communications Service (MICS) frequencies, the medical band now emerging as a global standard.

"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 technology, more intelligent radio performance and extreme miniaturisation" 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 optimised single-chip wireless platform that delivers the economy required for mass-volume medical applications".

The new implantable transceiver design 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. The architecture would consume an average current of less than 1µA, and less than 1.7mA peak, for a 0.05% duty-cycle, 400 kbits/second bi-directional communications application.

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.

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, minimising the potential for interference and providing an excellent platform for economy of scale through standardisation.

Among the applications that Cambridge Consultants sees for high-performance/long-lifecycle MICS devices 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 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). In addition to wireless expertise, Cambridge Consultants has a library of digital silicon intellectual property including processor and DSP cores optimised for low power applications, and a library of analogue IP 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. The company's royalty-free RISC processor core, XAP, is integrated into the market leading Bluetooth chip family for example - which has already been fabricated in volumes of over 50 million.

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