RF module configured for implantable medical devices

August 07, 2015 // By Graham Prophet
An off-the-shelf radio link, Microsemi’s ZL70323 is, the company says, the smallest radio module it has ever produced. The ZL70323 is optimised for implantable medical devices such as pacemakers, cardiac defibrillators and neurostimulators—measuring just 5.5 x 4.5 x 1.5 mm.

The module supersedes the company’s ZL70321 and complements its ZL70120 radio module used for external device controllers. Both modules are based on Microsemi’s ultralow power (ULP) ZL70103 radio transceiver chip, which supports a very high data rate radio frequency (RF) link for medical implantable communication applications.

The implantable module implements all RF-related functions needed to deploy the implant node in a Medical Implantable Communications Service (MICS) RF telemetry system. The integrated antenna tuning circuit allows the module to be used with a wide range of implantable antennas (nominal antenna impedance is 100+j150 Ohms). The module provides the following major blocks:

- ZL70103-based MICS-band RF transceiver with integrated matching network, surface acoustic wave (SAW) filter for suppression of unwanted blockers, and antenna tuning;

- 2.45 GHz wake-up receiver matching network;

- Integrated 24 MHz reference frequency crystal; and

- Decoupling capacitors and series termination resistors.

Patient health and device performance data can be quickly transmitted with little impact to the battery life of the implanted device. The device operates in the 402–405 MHz MICS band. Multiple low power wake-up options are supported including using an ULP 2.45 GHz industrial, scientific and medical (ISM) band wake-up receive option. The ZL70103 consumes less than 6 mA when transmitting or receiving and 290 nA when in a periodic sleep/sniff mode (1 second sniff interval).

“Our radio modules allow medical device companies to focus … on new therapies that enable a better quality of life. The reduction in size makes it easier for companies to design smaller devices that aid patient comfort and reduce risk of infection, as a smaller incision is needed,” said Martin McHugh, Microsemi’s product line manager for the new module. “RF engineering is a highly specialised discipline and leveraging our deep expertise in this area also allows our customers to reduce design times, reduce time-to-market and minimise project risk.”

An application development kit (ADK) is available to qualified customers.

Microsemi; www.microsemi.com/products/ultra-low-power-wireless/implantable-medical-transceivers/zl70323