The first eight to ten TEmnp resonances have been identified in one large (6.1 X 7.3 X 13.0 m) and one small (1.0 X 0.6 X 2.0 m) TEM cell. The resonant frequencies fit a new equivalent coaxial box model with the effective length of the box depending on the mode. Weakly propagating TEmn modes were also detected at frequencies above their respective first-resonance frequencies. A biological body or metal box at the center of the test zone interacts strongly with the TE10p and TE11p resonances, but not with the TE01p resonances. These interactions cause bandwidth limitations in the use of TEM cells for bioeffects dosimetry studies, EMC testing, and probe calibration work.

Canada KIA 024 squarer All O(dc) sq-r DSBPSK 2fc Abstruct-The laboratory performance of four spreadspectrum (SS) detectors (full-band and partial-band radiometers, chip-rate detector (CRD) and squaring carrier detector) was measured for direct sequence (DS) and frequency hop (FH) S S signals, FHDS hybrids, and time hop (TH) DS signals. Probability of detection as a function of input SNR for a constant false-alarm rate was measured for numerous combinations of SS waveform and detector. Theories were compiled from the literature and extended as necessary to provide a unified theoretical description. The results usually agreed with theory to within one dB. A constant-false-alarm-rate method was used to reduce the drift problem of radiometers. The fact that chip-rate and squaringcarrier detectors have a much reduced drift problem was confirmed. It is concluded that the four SS detectors used are relatively simple and inexpensive devices with laboratory detection performance close to theoretical. 28.6-1 785 7803-9828-5194 $4.00 0 1994 IEEE

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Further studies of human whole-body radiofrequency (RF) absorption rates were carried out using a TEM-cell exposure system. Experiments were done at one frequency near the grounded resonance frequency (approximately 40 MHz), and at several below-resonance frequencies. Absorption rates are small for the K and H orientations of the body, even when grounded. For the body trunk in an E orientation, the absorption rate of a sitting person is about half of the rate for the same person standing with arms at the sides; the latter in turn is about half the rate for the same subject standing with arms over the head. Two-body interactions cause no increase in absorption rates for grounded people. They do, however, increase the absorption rates for subjects in an E orientation in free space; the largest interaction occurs when one subject is lambda/2 behind the other (as seen by the incident wave). When these results are applied to practical occupational exposure situations, the whole-body specific absorption rate does not exceed the ANSI limit of 0.4 W/kg for exposures permitted by the ANSI standard (C95.1-1982) at frequencies from 7 to 40 MHz.

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