----- Original Message -----

From: Robert Riedlinger
To: Randy Ross
Cc: Brian Phillips 

----- Original Message -----

From: Ross, Randy
To: Robert Riedlinger 

Sent: Wednesday, March 14, 2007 4:13 PM

Subject: RE: Andersen, J.B.

We noticed that years ago.  That is why our web site has for years said 

    "...In general up to 50 percent of the power delivered to the antenna is absorbed by the head and/or hand of a user and 50 percent or more is transmitted away from the phone to find a cell site. ........ A hand or a head will absorb less energy from the "radiating structure(s)" of the phone (not necessarily exclusively the "antenna" or "sticking up part") when the phone's radiating structure is a greater distance away and will absorb more energy when it is held by the hand close to the head......... Studies have shown that for some phones operating at maximum output conditions, with certain head sizes and phone configurations, it may be possible to reach or exceed the specific absorption rate (SAR) limit for the general public in Safety Code 6 and also the "uncontrolled environment" limit of the American IEEE C95.1 - 1991, Standard of the Institute of Electrical and Electronics Engineers, Inc...... The American IEEE standard exempts cell phones from exposure restrictions when the radiating structure (not necessarily exclusively the antenna or sticking up part) is maintained at a distance greater than 2.5 cm from the body and certain other restrictions on maximum phone power are met. Studies show that SAR values in the head are reduced when a phone's radiating structure(s) is held farther from the head. It would appear that it is difficult to impossible for the phone user to assure compliance with the Safety Code 6 SAR limits when the radiating structure is contacting or very close to the head. Since the usual maximum output power of a hand held portable cellular or PCS phone is 0.6 watts, it is unlikely that the most restrictive conditions of Safety 6 will be exceeded when the radiating structure is not in contact with the head. More specifically portable telephones may be considered not to present a health hazard when operated with the radiating structure (not necessarily exclusively the antenna) 2.5 cm away from the body. A "hands free" earpiece has been shown to significantly reduce the SAR in user's head."

 

Randy Ross, MSc
Head, Non-Ionizing Radiation and Non-Medical X-Ray Program
Radiation Protection Services
BC Centre for Disease Control
655 West 12th Avenue, Vancouver BC V5Z 4R4
Tel: 604-660-6634, Fax: 604-660-6628
http://www.bccdc.org/division.php?item=8

 

---

From: Robert Riedlinger
Sent: Wednesday, March 14, 2007 3:27 PM
To: Ross, Randy
Cc: Phillips, Brian
Subject: Andersen, J.B.

 

. Results for radiation efficiency show that close to half of the energy is absorbed by hand and head

 

 

Effects on portable antennas of the presence of a person Toftgard, J.   Hornsleth, S.N.   Andersen, J.B.   Inst. of Electron. Syst., Aalborg Univ.; This paper appears in: Antennas and Propagation, IEEE Transactions on Publication Date: Jun 1993 Volume: 41,  Issue: 6 On page(s): 739-746 ISSN: 0018-926X References Cited: 14 CODEN: IETPAK INSPEC Accession Number: 4505211 Digital Object Identifier: 10.1109/8.250451 Posted online: 2002-08-06 18:39:41.0

Abstract This work deals with the influence the presence of a person has on the performance of antennas for hand-held portable telephones. It is shown how input impedance, far-field radiation pattern, radiation efficiency, and the magnitude of the near field are affected by the presence of the human body. The investigations have been carried out by applying the finite-difference time-domain (FDTD) technique to a model of the telephone with a λ/4 monopole antenna and a simple hand-head model of the operator. Results from this configuration are compared with results for the telephone box and antenna alone. Measurements have been performed to verify the results obtained by simulations. The results show that a shadow effect in the far-field pattern occurs in the direction of the person and that the radiation pattern, including polarization, changes considerably from the telephone with the antenna alone. The impedance results show a change in resonance frequency when the telephone is placed next to a person. Results for radiation efficiency show that close to half of the energy is absorbed by hand and head. On average a system loss of 3-4 dB should be included in a link budget, and there is considerable fading, even in a radio-anechoic chamber, when persons move around in a natural manner

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