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PMSE Body Effect

Wireless microphones and In-Ear-Monitor (IEM) are typically operated close on Human's Body or mounted in production environment. In both cases the emitted radiation is affected: on body used equipment only negative by absorption of radiated power.

To learn more about scenario "PMSE on Body", in a first step we compare it to a dipole antenna:

Vertical Dipole Antenna
* Reference scenario
* Radiated power = 100%, maximal 50 mW
* Antenna gain = 0 dBD
* In all directions the same field strength

Dipole completed by a Reflector
* Typical antenna characteristic Cardioid
* Radiated power = 100%
* Antenna gain in shown direction
* Some directions with a higher field strength

Contrary to this scenario, PMSE radiates less energy than a reference dipole. See below typical measurements of hand-held (left figure) and body-worn (right figure) PMSE operated at 500 MHz.
The light-blue line shows the reference dipole radiation, if operated by PMSE output power.
The purple line shows the PMSE radiation if its antenna is operated close to human’s body.
Finally, the comparison of the enclosed areas (radiated PMSE power) shows the high Body Effect:

CEPT Report 30 shows at page 106 a body loss example for the band 790 to 862 MHz:

It can be seen the body absorbs radiation: significant behind the body, few in front - seen from the placement of the transmitter. It can also be seen that the closer the radiating antenna is at the body the higher the absorption: less energy is radiated. This reduces the range of operation. In this example the handheld, left picture, has a certain distance to the body and shows fewer absorption than the right scenario where the antenna of the body pack is very close to the body.

See also:

1)
DKE Measurements on radiated power of PMSE in the 822 and 1800 MHz band
Measurement of the radiated power of 0.8 / 1.8 GHz hand held PMSE [1.313 KB]

2)
Cobham Technical Services, Report 2009-0333
Analysis of PMSE Wireless Microphone Body Loss Effects [784 KB]

3)
The Institute for Applied Physics (Italian National Research Council) provides an Internet resource for the calculation of the “Dielectric Properties of Body Tissues” in the frequency range 10 Hz to 100 GHz: http://niremf.ifac.cnr.it/tissprop/

4)
Page 52 to 59 of technical report ETSI TR 102 546 (not binding APWPT copy [1.209 KB] )

5)
Study of IT'IS (a foundation of the ETHZ), financed by BAKOM/OFCOM (CH)
The effect of the human body on wireless microphone transmission (not binding APWPT copy [19.802 KB] )