Cambridge Consultants has designed an intelligent radio transceiver architecture that it claims 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. The device will operate in the Medical Implant Communications Service (MICS) frequencies.

A key attribute of Cambridge Consultants' design is exceptional power economy, and the architecture would consume an average current of less than 1 μA, and less than 1,7 mA peak for a 0,05% duty-cycle, 400 Kbps bi-directional communications application, it says. This could provide over 10 years of activity from a lithium cell, 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 miniaturisation 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 optimised single-chip wireless platform that delivers the economy required for mass-volume medical applications."

The new implantable transceiver design, called SubQore, makes use of the company's portfolio of IP for ultra-low power radio, as well as its lean RISC processor core, XAP. Extreme attention to power economy has been applied throughout the design.

Each implantable medical application is different and requires a particular mix of control, monitoring and communications facilities. SubQore's architecture reflects this diversity of potential use. In its basic form, it 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 digital signal processing 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' frequency band, and the company says it offers a communications range of 2 m when implanted under the skin. The only other use of this band is for meteorological equipment, which minimises the potential for interference.