Ansi c63. 19 -2a -2007 Revision of

F.4Summary

1. 
   Helmholtz coils may be used to volumes with dimensions of 0.6 r for highly accurate probe or sensor calibration.
   
2. 
   Helmholtz coils should be used in the series-aiding connection, but may be used in the parallel-aiding connection if necessary—with extra current controls and precautions.
   
3. 
   Balance the products NI in the two coils for maximum accuracy.
   
4. 
   Consider Helmholtz coils a primary standard; they can be calibrated by ruler.
   

F.5References

[1] Bronaugh, E. L., “Helmholtz coils for EMI immunity testing: stretching the uniform field area,” Electromagnetic Compatibility, Seventh International Conference on EMC, Pub. no. 326, Institution of Electrical Engineers, York, UK, 1990, pp 169–172.

[2] Rubens, S. M., “Cube-surface coil for producing a uniform magnetic field,” Review of Scientific Instruments, vol. 16, no. 9, Sept. 1954, pp 243–245.

[3] Loeb, L. B., Fundamentals of Electricity and Magnetism, 3rd Ed., Dover Publications, Inc., NY, 1961, pp 56–62.

[4] Van Bladel, Electromagnetic Fields, McGraw-Hill, Inc., NY, 1964, pp 155–156.

[5] Millanta, L. M., et al., “Helmholtz coils: static and frequency-dependent performance limitations.”

Annex G
(informative)
RF envelope comparison for U.S. WD systems

G.1Introduction

The purpose of this annex is to outline the similarities and differences between the current cellular systems being used in the U.S. The discussion is tailored towards the information that is pertinent to the issue of hearing aid compatibility, when addressing the issue of interference to hearing aids from digital cellular phones. There is one major analog and several digital cellular systems on the air currently in the U.S. They are advanced mobile phone systems (AMPSs) (IS-91A), NADC (IS-136), PCS1900 (JTC007), iDEN, and CDMA (IS-95). The following discussion will review each of these systems, highlighting their operation as it relates to the time domain transmitter signatures. Table G.1 shows a summary of the relevant parameters of each of these systems.
Table G.20—Relevant parameters for time domain transmitter signatures

Characteristic	IS-91A Analog	IS-136 800 MHz TDMA (NADC)	800 MHz GSM	JT C007 1900 MHz PCS	IS-95 800 MHz CDMA	iDEN
Transmit frequency (MHz)	824–849	824–849	890–915	1850–1990	824–849	806–821 896–901
Peak transmitter power (mw)	600	600	2000	1000	250	600
Lowest transmitter power (mw)	7	0.4	20	20	< 0.001	0.3
Average transmitter power (mw)	600	200	235	118	varies	100 (1:6 duty cycle 200 (2:6 duty cycle)
Pulse repetition (pulses/sec)	N/A	50	217	217	varies	11 (1:6 duty cycle) 22 (2:6 duty cycle)
Pulse width (msec)	N/A	6.7	0.6	0.6	varies	15
Time between pulses (msec)	N/A	13.4	4	4	varies	75 (1:6 duty cycle) 30 (2:6 duty cycle)
Modulation in pulse	FM	pi/4 QPSK(1)	GM SK(2)	GM SK(2)	OQPSK(3)	QUAD 16-QAM
Power control	Base station only	Base station only	Base station only	Base station only	Base and mobile	Mobile
pi/4 QPSK modulation has eight modulation phase states, which travel in an irregular path between states, resulting in a small of AM content. GMSK modulation has four modulation phase states which travel in a circular path between states, resulting in no AM content. OQPSK modulation has four modulation phase states which travel in an irregular path between states thus resulting in a large AM content.

Directory: documents
documents -> Concept stage
documents -> Concept stage
documents -> The great global switch-off
documents -> Nonprofit grant application
documents -> The Truth about the Rwandan Genocide
documents -> Annual InStructional unit plan
documents -> Chaos equipment included

Download 1 Mb.

Share with your friends: