Hand-held Transceivers Research Articles

The effect of exposure to radiofrequency fields on cancer risk in the general and working population: A protocol for a systematic review of human observational studies.

The World Health Organization (WHO) has an ongoing project to assess potential health effects of exposure to radiofrequency electromagnetic fields (RF-EMF) in the general and working population. Here we present the protocol for a systematic review of the scientific literature on cancer hazards from exposure to RF-EMF in humans, commissioned by the WHO as part of that project. To assess the quality and strength of the evidence provided by human observational studies for a causal association between exposure to RF-EMF and risk of neoplastic diseases. We will include cohort and case-control studies investigating neoplasia risks in relation to three types of exposure to RF-EMF: near-field, head-localized, exposure from wireless phone use (SR-A); far-field, whole body, environmental exposure from fixed-site transmitters (SR-B); near/far-field occupational exposures from use of handheld transceivers or RF-emitting equipment in the workplace (SR-C). While no restriction on tumour type will be applied, we will focus on selected neoplasms of the central nervous system (brain, meninges, pituitary gland, acoustic nerve) and salivary gland tumours (SR-A); brain tumours and leukaemias (SR-B, SR-C). Eligible studies will be identified through Medline, Embase, and EMF-Portal. We will use a tailored version of the OHAT's tool to evaluate the study's internal validity. We will consider separately studies on different tumours, neoplasm-specific risks from different exposure sources, and a given exposure-outcome pair in adults and children. When a quantitative synthesis of findings can be envisaged, the main aims of the meta-analysis will be to assess the strength of association and the shape of the exposure-response relationship; to quantify the degree of heterogeneity across studies; and explore the sources of inconsistency (if any). When a meta-analysis is judged inappropriate, we will perform a narrative synthesis, complemented by a structured tabulation of results and appropriate visual displays. Confidence in evidence will be assessed in line with the GRADE approach. This project is supported by the World Health Organization. Co-financing was provided by the New Zealand Ministry of Health; the Istituto Superiore di Sanità in its capacity as a WHO Collaborating Centre for Radiation and Health; ARPANSA as a WHO Collaborating Centre for Radiation Protection. PROSPERO CRD42021236798.

Local specific absorption rate reduction method for 1.2-GHz band handheld transceiver with a reflector

Local specific absorption rate reduction method for 1.2-GHz band handheld transceiver with a reflector

Design of self‐quadruplexing antenna using substrate‐integrated waveguide technique

AbstractA low‐profile cavity‐based self‐quadruplexing antenna (SQA) is projected by using substrate‐integrated waveguide (SIW) technology for multiband wireless communications. Four quarter‐mode‐like SIW‐based cavity resonators are used for radiation and each resonator is fed individually by four distinct printed feed lines. The proposed antenna topology offers four resonant frequencies around 3.5, 5.2, 5.5, and 5.8 GHz band when excited by the corresponding feed. By appropriately adjusting the design essentials, an isolation around 23.6 dB is realized between any two input ports. Thus, four separate signals can coexist on a single antenna assembly without interfering each other, which help to realize the self‐quadruplexing phenomenon. Finally, the antenna is prototyped and experimentally verified. The experimental results show good agreement with simulated counterparts. Moreover, the proposed design retains the advantages of a small footprint, compact size, low cost, and ease of manufacturing, which makes it a promising candidate for highly integrated handheld transceivers.

A study of the product styling design evaluation system and applications for handheld transceivers

This study is based on the fundamental contents and program of product styling designs. Embodied individual properties of handheld transceiver products and styling design experiences were integrated into the investigation. Via detailed questionnaire investigations and data analyses, the contents of evaluating handheld transceiver product design schemes can be verified and confirmed. This approach follows both fundamental quantitative and qualitative principles including comprehensiveness, systematicness, and flexibility. An evaluation model for the product styling of handheld transceivers has been built along and subjective factors, neutral factors, and objective factors serve as the factors of the first-level indicators. The analytic hierarchy process was used to build the hierarchical structure of the evaluation system. The sum-product method was utilized to calculate the weight vectors in order to form the ranking of levels in the hierarchy. The weight index of each level of the hierarchy in the evaluation system can also be obtained. The final step is to implement the examination and verification of this design evaluation system on the product styling designs for handheld transceivers. The implementation verified the objectivity, rationality, and effectiveness of this evaluation system, which has been endorsed jointly by enterprise customers and design houses. This approach has been verified to be provided with economic values and social values to a certain extent.

Morphometric study of human foetal testes of north west region of India in second trimester

Murciano-Granadina dairy goats (n = 220) were used to assess the performance of visual and electronic identification devices: 1) leg tags (LT) on the shank of the right hind leg (metatarsus) consisting of plastic bands (181 × 39 mm, 21 g; n = 220) printed with a 3-digit code and closed with 2 types of electronic button tags (ET1, 3.9 g, 26 mm o.d., n = 90; ET2, 5.5 g, 25 mm o.d., n = 130); 2) electronic rumen boluses (RB, 75 g, 68 × 21 mm, n = 220) containing 32 × 3.8 mm transponders; 3) electronic ear tags (EE, button-button, 4.8 g, 24 mm, n = 47); and 4) visual plastic ear tags (VE, flag-button, 4.2 g, 40 × 38 mm, n = 220). The shank circumference of 47 replacement kids (5 to 6 mo of age) and 103 adult goats was measured to evaluate the proper circumference for fastened LT. Goats were identified with RB and VE before the experiment. Time for leg tagging, reading, and data recording with a handheld transceiver was measured. Readability [(read/readable) × 100] was monitored for 1 yr with goats restrained in the milking parlor. Reading time and errors of RB and ET2 in the milking parlor using the handheld transceiver were recorded. Shank circumference of kids (70 ± 1 mm) was 79.5% of that in adult goats (88 ± 1 mm), thus LT (107 ± 1 mm inner circumference) were only applied to adult goats as they were inadequate for 6-mo-old kids. Time for leg tagging and data recording was 53 ± 3 s. At 1 yr, readability of RB was 96.5%. No LT losses occurred and all were visually readable, although 3 (1.5%) had to be removed due to limping, leading to a final LT retention of 98.5%. Moreover, 7 (3.6%) LT were found open and electronically unreadable. Readability of button transponders, excluding removed LT, was 93.6% (3 lost and 2 unreadable) for ET1, and 98.3% (2 lost) for ET2. Readability was 95.7 and 97.0% in EE and VE ear tags, respectively. Only LT and ET1 readabilities differed. Reading time and reading errors (0.3 vs. 0%) in the milking parlor were greater for RB (61.2 s) than for ET2 (45.9 s). In conclusion, LT were not adequate for the identification of goat kids under 6 mo of age. Only LT with ET2 transponders met International Committee for Animal Recording requirements for official identification of adult goats (readability >98%) under the conditions of this experiment.

Readability of visual and electronic leg tags versus rumen boluses and electronic ear tags for the permanent identification of dairy goats

Murciano-Granadina dairy goats (n=220) were used to assess the performance of visual and electronic identification devices: 1) leg tags (LT) on the shank of the right hind leg (metatarsus) consisting of plastic bands (181 × 39mm, 21g; n=220) printed with a 3-digit code and closed with 2 types of electronic button tags (ET1, 3.9g, 26mm o.d., n=90; ET2, 5.5g, 25mm o.d., n=130); 2) electronic rumen boluses (RB, 75g, 68 × 21mm, n=220) containing 32 × 3.8mm transponders; 3) electronic ear tags (EE, button-button, 4.8g, 24mm, n=47); and 4) visual plastic ear tags (VE, flag-button, 4.2g, 40 × 38mm, n=220). The shank circumference of 47 replacement kids (5 to 6 mo of age) and 103 adult goats was measured to evaluate the proper circumference for fastened LT. Goats were identified with RB and VE before the experiment. Time for leg tagging, reading, and data recording with a handheld transceiver was measured. Readability [(read/readable) × 100] was monitored for 1 yr with goats restrained in the milking parlor. Reading time and errors of RB and ET2 in the milking parlor using the handheld transceiver were recorded. Shank circumference of kids (70±1mm) was 79.5% of that in adult goats (88±1mm), thus LT (107±1mm inner circumference) were only applied to adult goats as they were inadequate for 6-mo-old kids. Time for leg tagging and data recording was 53±3s. At 1 yr, readability of RB was 96.5%. No LT losses occurred and all were visually readable, although 3 (1.5%) had to be removed due to limping, leading to a final LT retention of 98.5%. Moreover, 7 (3.6%) LT were found open and electronically unreadable. Readability of button transponders, excluding removed LT, was 93.6% (3 lost and 2 unreadable) for ET1, and 98.3% (2 lost) for ET2. Readability was 95.7 and 97.0% in EE and VE ear tags, respectively. Only LT and ET1 readabilities differed. Reading time and reading errors (0.3 vs. 0%) in the milking parlor were greater for RB (61.2s) than for ET2 (45.9s). In conclusion, LT were not adequate for the identification of goat kids under 6 mo of age. Only LT with ET2 transponders met International Committee for Animal Recording requirements for official identification of adult goats (readability >98%) under the conditions of this experiment.

Standoff and Miniature Chemical Vapor Detectors Based on Tunable Diode Laser Absorption Spectroscopy

Trace gas sensing and analysis by tunable diode laser absorption spectroscopy (TDLAS) has become a robust and reliable technology accepted for industrial process monitoring and control, quality assurance, environmental sensing, plant safety, and infrastructure security. Sensors incorporating well-packaged wavelength-stabilized near-IR (1.2-2.0 ?m) laser sources sense over a dozen toxic or industrially-important gases. Recently developed mid-IR lasers, particularly quantum cascade devices spanning wavelengths of 3-12 ?m, can sense in real-time sub-parts per million concentrations of many hydrocarbons.A large emerging application for TDLAS is standoff sensing of chemical vapors, e.g., leaks from natural gas pipelines. Employing a 10-mW DFB laser, the eye-safe, battery-powered, 6-lb handheld remote methane leak detector illuminates a noncooperative topographic surface and analyzes returned scattered light to deduce the presence of excess methane. For aerial surveying, replacing the handheld transceiver with a large-aperture telescope and adding an erbium-doped fiber amplifier to the laser transmitter extends the standoff distance to 3000 m. By selecting a laser source having an appropriate wavelength, the standoff TDLAS tool detects trace concentrations of nonmethane hazardous gases, including several high-priority toxic industrial compounds and emissions from illicit chemical production laboratories. This paper also describes concepts for miniature integrated optic TDLAS sensors that combine a laser source, sampling section, and detector on a monolithic semiconductor materials system substrate. Such chip-scale low-power integrated optic gas-phase chemical sensors may enable low-cost mass production, so that many hundreds or thousands of such sensors can be distributed cost-effectively over a wide area of interest and communicate via wireless networks.

Traceability of extensively produced Iberian pigs using visual and electronic identification devices from farm to slaughter1

A total of 351 Iberian pigs with equal numbers of both sexes from 2 commercial farms were used to study the ability of various identification devices to guarantee the traceability required for labeled meat products from Iberian pigs reared under extensive production conditions in Spain. The performance of tattoos, visual ear tags, electronic ear tags, and i.p.-injected transponders of half duplex and full duplex technologies were compared during a production cycle from nursery to slaughter at 15 mo of age (156 +/- 3 kg of BW). No major health reactions to any of the identification methods were detected. Results showed that tattooing was not an adequate identification procedure due to reading difficulties as a consequence of dark skin, soiled appearance, and figure deformation. Ear tag losses and failures were affected by fencing type and increased in one of the farms (20.4 and 15.7% for losses and failures, respectively; P < 0.05) as a consequence of using barbed-wire fences. Ear tag losses decreased when fences changed to stone blocks at 365 d of age. Visual and electronic ear tag losses during transport and slaughter were low (3.7% for visual and 3.1% for electronic tag). Results of injectable transponders during the growing-fattening period were variable and were more readable for the half duplex than for the full duplex i.p. transponders (92.0 vs. 68.7% +/- 1.5; P < 0.05). Handheld transceivers worked properly under extensive conditions, although the body size and skin characteristics of the Iberian breed might limit the performance of reading devices, and the use of transceivers with longer reading distances is recommended. The main problem observed with i.p. transponders was their low recovery rate at slaughter due to the lack of adherence of the transponders to the omentum.

Comparison of visual and electronic identification devices in pigs: Slaughterhouse performance1,2

Traceability during slaughter was studied in 1,581 pigs identified by different devices. Treatments were visual ear tags (n = 1,300), electronic ear tags of different technologies (half-duplex, n = 636; full-duplex, n = 632), and intraperitoneally injected transponders of different technologies (half-duplex 32 mm, n = 645; full-duplex 34 mm, n = 642). Piglets were individually identified at weaning and intensively fed until 100 kg of BW. Pigs were slaughtered in 2 commercial slaughterhouses (including scalding, flaming, and peeling) at different throughputs (450 and 550 pigs/h). Readability during slaughtering was checked visually and using standardized hand-held transceivers. No effect of slaughterhouse was detected (P > 0.05). Ear tag losses in the slaughtering line were similar for visual (3.7%) and half-duplex (3.5%) but were increased for full-duplex (11.5%; P < 0.05). Moreover, electronic failures during slaughtering did not differ (P > 0.05) between ear tags (half-duplex, 1.1%; full-duplex, 0.6%). Intraperitoneally injected transponders were not affected by slaughtering (retention 100%, no failures), and 89.0% of the transponders were manually recovered from the abdominal viscera in the offal trays. The remaining transponders (11.0%) were lost on the floor, but none were found in the carcasses. No differences (P > 0.05) in recovery were observed between intraperitoneal transponders. Considering on-farm and slaughterhouse data, total traceability from farm to carcass release was greater (P < 0.05) for intraperitoneally injected transponders (98.2%) than for ear tags. Between ear tags, the greatest traceability was obtained with visual tags (95.7%), which differed (P < 0.05) from electronic tags (half-duplex, 91.4%; full-duplex, 84.5%; P < 0.05). Intraperitoneally injected transponders were an efficient and reliable identification system for tracing pigs from farm to the end of the slaughter line, allowing the transfer of pig identification to the carcass. Adherence of intraperitoneally injected transponders to the viscera should be improved to reduce risks of loss in the meat chain. A dual system based on intraperitoneally injected transponders and plastic ear tags would allow a redundant and automatic reading system that is efficient and reliable for data management and traceability in the swine industry.

Comparison of visual and electronic identification devices in pigs: On-farm performances1,2

A total of 1,822 pigs from 2 farms (farm A, n = 1,032; farm B, n = 790) were used to evaluate pig traceability under on-farm conditions by using identification devices (n = 4,434) of different technologies. The devices were visual ear tags (n = 1,533; Model 1, n = 776; Model 2, n = 757), electronic ear tags (n = 1,446; half-duplex, n = 702; full-duplex, n = 744), and intraperitoneally injected transponders (n = 1,455; half-duplex, n = 732; full-duplex, n = 723). A group of 790 pigs wore 3 types of devices, and 1,032 wore 2 devices. Piglets were identified before (wk 1 to 3 of age; farm A) or after (wk 3 to 4 of age; farm B) weaning and intensively fattened until approximately 100 kg of BW. Readability of devices was checked at each farm operation by using standardized handheld transceivers. No negative effects of the identification devices on animal health (mortality rate, 8.4%) or performance were detected. On-farm losses averaged 1.6% for ear tags (visual, 0.8%; half-duplex, 1.9%; full-duplex, 2.7%; P > 0.05) and 1.8% for intraperitoneally injected transponders (half-duplex, 1.7%; full-duplex, 1.9%; P > 0.05). Moreover, 1.4% electronic failures occurred in the electronic ear tags (half-duplex, 2.2%; full-duplex, 0.6%; P < 0.05) but not in the intraperitoneally injected transponders. Final on-farm readability was greater (P < 0.05) for visual ear tags (99.2%) than for electronic ear tags (half-duplex, 95.9%; full-duplex, 96.7%; P > 0.05). Readability for intraperitoneally injected transponders was intermediate (half-duplex, 98.3%; full-duplex, 98.1%; P > 0.05). Electronic devices were in all cases easier and faster to read than the visual ear tags. Visual ear tags and intraperitoneally injected transponders were efficiently retained under conditions of commercial pig farms, which agrees with the minimum values recommended by the International Committee for Animal Recording (> 98%). When readability and reading ease were also included as decision criteria, injectable transponders were preferred.

An open-path, hand-held laser system for the detection of methane gas

We have developed an open-path hand-held gas detector incorporating a distributed feedback InGaAs laser diode at 1.65 µm. Incorporated into a hand-held transceiver unit, the emitted laser beam is backscattered from nearby surfaces, collected and focused onto an amplified InGaAs detector using a 150 mm diameter plastic Fresnel lens. At ranges of 4–5 m, a typical backscattered signal is tens of nanowatts of laser light. Applying second derivative wavelength modulation spectroscopy gives a sensitivity to methane of better than 10 parts per million over a one metre path length. A number of demonstration units have been fabricated and successfully evaluated by end users.

The use of passive injectable transponders in fattening lambs from birth to slaughter: effects of injection position, age, and breed.

A total of 1,159 Tiris half-duplex passive injectable transponders (PIT) of 32-mm length were used to study the electronic identification of 618 fattening lambs of two breeds used for different production purposes (Ripollesa, meat breed, n = 271, and Manchega, dairy breed, n = 347). The lambs were s.c. injected in the armpit and the retro-auricular positions at 2, 15, and 30 d of age. All lambs were also tagged with a small plastic ear tag after birth. A group of 76 lambs were injected only in the right armpit and were kept for breeding. The PIT losses, breakages, and electronic failures were evaluated at weekly weight recordings throughout the fattening period using two types of hand-held transceivers. Fattened lambs were harvested in a commercial abattoir between 3 and 4 mo of age when they reached market weight (11 to 12 kg hot carcass weight). The total number of PIT that fell or broke in the slaughtering line, the location method, and the recovery time were recorded. On the farm PIT losses were not affected (P > 0.05) by age at injection, injection position, or breed. Mean losses of PIT and ear tags during the same period were 5% and 6.3%, respectively (P > 0.05). No PIT breakages or failures were observed during the fattening period. Mean recovery of PIT in the abattoir (85.6%) was affected (P < 0.05) by breed and injection position. Losses of PIT in the abattoir were greater (P < 0.05) in the Ripollesa breed (18.4%) than in Manchega (10.0%), and for both breeds losses were greater (P < 0.05) in the retro-auricular than in the armpit positions (18.6 vs 10.8%, respectively). The percentage of PIT broken during slaughtering was low (0.3%). The mean recovery times (18 +/- 2 s) were not affected (P > 0.05) by breed, injection position, or age, thus allowing a harvesting speed of 200 lambs/h on average. In conclusion, the injection of 32-mm PIT into the armpit or the retro-auricular region is not recommended as a practice for the electronic identification of fattening lambs, even though they perform similarly to small plastic ear tags. This is partly a consequence of the PIT losses observed on the farm but mainly because of the difficulties with recovering the PIT in the abattoir. More research will determine whether the use of smaller transponders or injection in other positions could improve their performance in fattening lambs.

Mobile voice verification system

The present invention generally includes three principal components; namely, (1) a hand held transceiver for transmitting a voice pattern while moving (e.g., driving) past an (2) infra-red receiver array which receives the transmitted voice pattern, and a (3) speech enhancement and voice verification algorithm for conducting a comparison between the transmitted voice pattern and the registered voice patterns stored in the computer's memory. The hand held transceiver includes a conventional telephone handset in which a microphone subassembly, a transceiver circuit card, and LED indicators are housed. The transceiver element, also housed in the handset, includes a 16-bit analog to digital converter for converting the analog voice pattern to a corresponding digital signal, a microprocessor, a memory unit for storing the digitized voice sample for a predetermined period of time, and an IR transceiver for transmitting the digitized voice sample. Once a voice sample is digitized in the hand held transceiver, the individual may point the transceiver at a receiver array station which is housed in a cabinet, and after receiving a prompt from the receiver array, the voice signal, among other things, will be automatically, wirelessly transmitted. The processing computer will first recognize the spoken phrase, and then perform speaker verification using speech processing and comparing algorithms consisting of a speech recognizer and a vector quantification software classifier, ultimately sending a “pass” or “fail” signal to a control center computer based upon whether the speaker's voice pattern matches one of the voice samples stored in the computer's memory, respectively.

Effects of injection position and transponder size on the performances of passive injectable transponders used for the electronic identification of cattle.

A total of 686 Tiris half-duplex passive injectable transponders (PIT) of two sizes (23 and 32 mm) were randomly injected s.c. in three positions, armpit, ear scutulum, and upper lip, in 343 fattening calves (1 to 3 mo old). Injections were performed by two trained and two untrained operators. Losses and breakages on the farm were recorded at wk 1, 3, 7, 11, and 15 in restrained animals using two types of hand-held transceivers with a stick antenna. Dynamic reading efficiency (DRE) in animals running through a raceway was also evaluated at wk 1 and 3 and monthly until slaughter, using a stationary transceiver working at 137 dB x microV x m(-1) at 3 m. The total number of PIT that fell or broke in the slaughtering line, the location method, and the recovery time were also recorded. Results on the farm showed low breakages on average (0.4%) and differences (P < 0.05) in losses according to position (armpit, 1.7%; ear, 5.2%; and lip, 14.0%). An interaction (P < 0.05) between position x size was observed, and losses were greatest using a 32-mm PIT in the lip. The DRE was affected (P < 0.05) by PIT position and size, and values were greater for the 32-mm PIT in all positions (armpit: 99.9 +/- 0.1 vs 95.8 +/- 4.9%; ear: 93.8 +/- 2.2 vs 81.9 +/- 4.6%; lip: 66.8 +/- 4.9 vs 53.4 +/- 4.7%, respectively, for 32 vs 23 mm). Recovery of PIT in the abattoir was on average 96.7, 96.7, and 99.2% for armpit, ear, and lip, respectively (P > 0.05). Most of the PIT injected in the armpit were recovered by sight or palpation, but 31.9% were recovered after cutting the muscles around the area and 10.7% were recovered on the internal side of the hide, which jeopardized carcass identification. Recovery of PIT injected in the ear was 23.4% in the hide and 76.6% in the auricular muscles of the head. The easiest recovery was in the lip, 8.9% of PIT were located in the hide and 91.1% in the head. Recovery time was affected (P < 0.05) by position: the quickest was lip (27 +/- 2 s), followed by ear (52 +/- 5 s) and armpit (78 +/- 7 s). In conclusion, taking into account retention and reading performances, injection of a 32-mm PIT into the armpit showed the best results on the farm, but a careful and longer recovery was needed in the abattoir. Improvement of recovery methodology and time would be necessary in order to recommend injection of PIT in the armpit instead of in the ear for cattle tracking or monitoring.

Characterisation of Energy Deposition in the Head from Cellular Phones

This paper is an extension of previous work on the evaluation of power deposition in the head from hand-held transceivers deployed at 900 and 1800 MHz. A realistic model of the head was produced by segmenting a close-grained set of serial MRI slices from one subject. A generic transceiver was considered to be a λ/4 monopole on a metal box. The purpose of that study was to find the maximum SAR values averaged over I g and 10 g for comparison with protection standards based on thermal considerations. The present work investigates the distribution of energy deposition in the head with particular reference to putative sites of cancer induction. Various modifications of the original model had to be made to perform this study including the introduction of the paired parotid, submaxillary and sublingual glands. The SAR distribution in the head at 900 and 1800 MHz has been calculated for various positions of the transceiver. The importance of attenuation through the head and its effect on the bilateral distribution of SAR in paired organs such as the salivary glands, ears and tear ducts is noted.

Cell Phones and Cancer: What Is the Evidence for a Connection?

There have been allegations in the media and in the courts that cell phones and other types of hand-held transceivers are a cause of cancer. There have also been numerous public objections to the siting of TV, radio and cell phone transmission facilities because of a fear of cancer induction. A recent publication in Radiation Research by Repacholi et al. (147, 631-640, 1997) which suggests that exposure to radiofrequency (RF) radiation may increase lymphoma incidence in mice has contributed to this controversy. The goal of this review is to provide biomedical researchers a brief overview of the existing RF radiation-cancer studies. This article begins with a brief review of the physics and technology of cell phones. It then reviews the existing epidemiological studies of RF radiation, identifying gaps in our knowledge. Finally, the review discusses the cytogenetics literature on RF radiation and the whole-animal RF-radiation carcinogenesis studies. The epidemiological evidence for an association between RF radiation and cancer is found to be weak and inconsistent, the laboratory studies generally do not suggest that cell phone RF radiation has genotoxic or epigenetic activity, and a cell phone RF radiation-cancer connection is found to be physically implausible. Overall, the existing evidence for a causal relationship between RF radiation from cell phones and cancer is found to be weak to nonexistent.

Dipole configurations with strongly improved radiation efficiency for hand-held transceivers

In this paper the design criteria for antenna structures with improved radiation efficiency while operating in close vicinity to a biological scatterer are investigated. The study is performed using a simple /spl lambda//2 dipole combined with a directive or reflective element. The optimization criteria are the effective radiation efficiency, the spatial peak specific absorption rate (SAR), and the sensitivity of the input resistance to the distance from the scatterer. It is demonstrated that the primary design criterion to improve the radiation efficiency is not directivity but the reduction of the maximum incident magnetic field strength in the exposed skin area of the user's head. For the reflectively coupled dipole, all performance parameters are improved by several decibels compared to a standard, /spl lambda//2 dipole, whereas for some other directive structures, the performance is impaired. The study is conducted with the generalized multipole technique (GMT) numerical simulation method, the results of which are validated by measurement methods.

Calculation of antenna near field reactions on low conducting materials using the finite element method

On account of the progress in using mobile telecommunications systems in the high frequency range, the human body is increasingly exposed to electromagnetic fields. Therefore, the numerical simulation of the power absorbed in human tissue becomes extremely important in order to avoid thermal destruction. A typical example is the strong interaction between the near field of a receiving antenna of a hand held transceiver and the sensitive organs on the head, like the eyes. A finite element formulation is given for calculating 3D electromagnetic scattering problems. The influence of a dipole excited field on low conducting materials situated very close to the antenna is discussed. The backscattering from the conducting object to the antenna can be treated as well. Along the far boundaries of the computational domain, absorbing boundary conditions of second order have been prescribed in order to avoid non-physical reflections. The formulation described is assessed by applying it to a special problem and the solution obtained is compared with a boundary element calculation.

Electromagnetic absorption in the human head from experimental 6-GHz handheld transceivers

We have used a new millimeter-resolution MRI-based model of the human body to calculate the electromagnetic absorption in the head and neck for three experimental Yagi antennas suggested for handheld transceivers of a proposed 6-GHz personal communication network (PCN) system. The SAR distributions are obtained with a resolution of 1.974/spl times/1.974/spl times/1.5 mm for transceivers that are held against the ears and tilted forward by 33/spl deg/. The finite-difference time-domain technique is used to calculate the EM fields and SARs for the transceiver, antenna, and head and neck coupled region that is divided into 158/spl times/84/spl times/188 or nearly 2.5 million cells. The highlights of the numerical calculations are verified by means of a head-shaped experimental model made of tissue-equivalent materials simulating the electrical properties (/spl epsiv//sub r/,/spl sigma/) of the skull, brain, muscle, eyes, and ears developed for use at 6 GHz. Because of the proximity to the antenna, the highest SARs are obtained for the upper part of the ear. For a planned radiated power of 0.6 W, the peak SARs averaged over any 1 g of tissue defined as a tissue volume in the shape of a cube are on the order of 0.5-1.0 W/kg for two of the proposed antennas and considerably higher (2.06 W/kg) for the third antenna using a narrower off-axis reflector. Low SARs for the first two antennas are likely due to the shielding provided by the relatively wider strip reflector plates used for these antennas.

Performance analysis of antennas for hand-held transceivers using FDTD

The design of antennas for hand-held communications devices depends on the implementation of simulation tools that can accurately model general topologies. The paper presents the analysis of small antennas mounted on hand-held transceivers using the finite-difference time-domain (FDTD) method. The key features of the FDTD implementation are discussed, with particular emphasis placed upon modeling of the source region. The technique is used to predict the gain patterns and broadband input impedance behavior of monopole, planar inverted F, and loop antenna elements mounted on the handset. Effects of the conducting handset chassis, the plastic casing around the device, and lumped elements integrated into the antenna design are illustrated. Experimental results are provided to verify the accuracy of the computational methodology. The concept of antenna diversity is discussed, and key assumptions and expressions are provided that characterize the multipath fading fields. Several computational examples demonstrate the diversity performance of two receiving antennas on a single handset. >