The incidence of radio-frequency impulsive noise within hospital buildings: initial measurements in the 450 MHz band

This paper reports on the incidence and level of man-made electrical impuls e noise capable of causing interference to low-power, ASK and FSK radio bio telemetry links. Measurements were made at two acute hospitals, one in a re sidential area of Belfast, Northern ireland and the other in an industrial part of Berlin, Germany. Monitoring was effected in the 450 MHz band using a communications receiver with its AGC line disabled and AM-detector AM out put fed to a PC-based logger. The RF bandwidth was 20 kHz and a rotatable f olded-dipole receiving antenna was used. Seven-day impulse counts were reco rded at each location, for separate RF input thresholds of -100, -110 and - 120 dBm and a common trigger window of 10 mu s-10 ms. Histograms depicting the average pulse count per minute are presented; values range from a maxim um of 55x10(3)/min for -120 dBm sensitivity in Berlin, to a minimum of 1.2/ min for -100 dBm sensitivity in Belfast, both with vertical polarisation. ( C) 1999 IPEM. Published by Elsevier Science Ltd. All rights reserved.