APPLICATION OF SPREAD SPECTRUM TECHNIQUE FOR MULTICHANNEL TRANSMISSION IN OPTICAL TELEMETRY

Koichi Shimizu, Nobuyuki Toya and Katsuyuki Yamamoto
Department of Bioengineering, Graduate School of Engineering,
Hokkaido University, Sapporo, 060, Japan

INTRODUCTION With the recent increase of medical equipment in an ICU and an operating room, their systematization has been required. However, the confusion of electric wires and tubes around a patient has to be avoided, and wireless transmission is preferable. Considering the EMC problems in a hospital, we have developed a data-transmission technique using an indirect scattered light. As a multiplexing technique for the multichannel transmission, the spread spectrum (SS) technique was applied.

METHOD Fig.1 illustrates the developed system. It is designed for the sampled and digitized medical data, such as an ECG, medical images and control signals for medical equipment. In the transmitter, the data is pre-modulated first, and then multiplied with a pseudo-noise (PN) signal for the SS modulation. The modulated signal is emitted in the air from an array of LED's. The indirect light reaches the receiver after the multiple reflections at a ceiling, a floor and walls. The signal received by a Si-PIN photodiode is demodulated by a SAW device using the same PN signal as used in the transmitter.

RESULTS To examine the feasibility of this technique, we have developed the fundamental part of the wireless data-transmission system. An experimental system was manufactured which consisted of two transmitters and one receiver. Using this system, the fundamental characteristics of this technique were investigated. Although there were some points to be improved, the feasibility of this technique was verified.