EMC Formulas - Reverse engineering

1 1 of 6 033109 EMC Formulas Term Conversion in 50 Environment Log dB V to dBm 107 VdBdBm dB A to dBm 73 AdBdBm dBm to dB V 107 dBmVdB dB A to dB V 34 AdBVdB dBm to dB A 73 dBmAdB dB V to dB A 34 VdBAdB Log Linear Volts to dBm 13)(20 VoltsLogdBm Amps to dBm 47)(20 AmpsLogdBm Watts to dB V 137)(10 wattsLogVdB Amps to dB V 154)(20 AmpsLogVdB Watts to dB A 103)(10 WattsLogAdB Volts to dB A 86)(20 VoltsLogAdB Log Linear dB V to Watts 1013710 VdBWatts dB A to Watts 1010310 AdBWatts dBm to Volts 201310dBmVolts dB A to Volts 208610 AdBVolts dBm to Amps 204710dBmAmps dB V to Amps 2015410 VdBAmps Linear Volts to Watts 502 VoltsWatts Amps to Watts 502 AmpsWatts Watts to Volts 50 WattsVolts Amps to Volts 50 AmpsVolts Watts to Amps 50 WattsAmps Volts to Amps 50 VoltsAmps Unit Conversion Log Linear Watts to dBm 3010 WattsLogdBm Volts to dB V 120log20 VoltsVdB Amps to dB A 120log20 AmpsAdB to dB log20dB Used for the conversion of Voltage & Current Log Linear dBm to Watts 103010dBmWatts dB V to Volts 2012010 VdBVolts dB A to Amps 2012010 AdBAmps dB to 2010dB 2 of 6 033109 Term Conversion / Ohms law Log dB V to dBm 90)(10 LogVdBdBm dB A to dBm 90)(10 LogAdBdBm dBm to dB V 90)(10 LogdBmVdB dB A to dB V )(20 LogAdBVdB dBm to dB A 90)(10 LogdBmAdB dB V to dB A )

2 (20 LogVdBAdB Linear Find Watts 2 AmpsWatts, 2 VoltsWatts Find Volts AmpsVolts, WattsVolts Find Amps WattsAmps, VoltsAmps dB Calculations dB Watts 2110 WattsWattsLogdB dB Volts 2120 VoltsVoltsLogdB dB Amps 2120 AmpsAmpsLogdB New Watts w/dB 10)(1010startWattsLogdBNewWatts New Volts w/dB 20)(2010startVoltsLogdBNewVolts New Amps w/dB 20)(2010startAmpsLogdBNewAmps dB Correction for distance change (antenna far field) 12distancedistance20 LogdB AAmpsVVoltsOhms WattsW WVW V WAW AAV2 AWWV2 2V 2 AAV Sine Wave Voltage levels for a sine wave AvgrmspeakVoltsVoltsVolts 22 AvgpeakrmsVoltsVoltsVolts 222 AvgpeakavgVoltsVoltsVolts 222 peakpeakpeakVoltsVolts 2 3 of 6 033109 w/ Impedance of air = 377 dB V/m to dBm/m2 mVdBmdBm dBm/m2 to dB V/m mdBmmVdB dB A/m to dB V/m mAdBmVdB dB V/m to dB A/m mVdBmAdB dB A/m to dBpT 2/ mAdBdBpT dBpT to dB A/m 2/ dBpTmAdB Watts/m2 to V/m 377//2 mWattsmV V/m to Watts/m2 377/22mVmWatts Radiated Field dB V/m to V/m 20120/10/mVdBmV V/m to dB V/m 120)(20/ mVLogmVdB New V/m with dB 20)(2010/startmVLogdBnewmV Interpolation values on a graph w/ Log of frequency This equation works for finding all points on a test curve where test limit is sloping ( DO 160F BCI testing))

3 LowerlowerupperlowerupperlowernewnewValu evaluevaluefreqfreqLogfreqfreqLogvalue Current Injection Power needed for BCI probe (50 ) for given Insertion loss(IL(dB)) 105010210 VoltsLOGILW atts 105010210 AmpsLOGILW atts 107310 AdBILW atts Power needed for BCI probe or EM Clamp (150 ) for given Insertion loss(IL(dB)) 1015010210 VoltsLOGILW atts 1015010210 AmpsLOGILW atts Conducted current measurement using a current probe. Where reading is in dB V and probe factor is dB or dBVdBAdB )(20 LogVdBAdB Power needed for TEM Cell )50( HeightWattsmV Power needed for GTEM Cell )50(2 eightSpectrualHWattsmV Wave length ( ) MHzmeters300][ MHzmeters75][41 4 of 6 033109 Period HzsTime1)( )(1sTimeHz VSWR VSWR given Fwd/Rev power fwdrevfwdrevWattsWattsWattsWattsVSWR 11 VSWR given Return Loss (RL) 20)(20)(101101dBRLdBRLVSWR VSWR Given Impedance (Z) ZO>ZL LOVSWR ZL>ZO OLVSWR VSWR given reflection coefficient ( ) 11 VSWR Reflection Coefficient ( ) FwdvWattsWattsRe AmploadAmpload 11 VSWRVSWR 20)(10dBRL Return Loss (RL) in dB 1120)(VSWRVSWRLogdBRL revfwdWattsWattsLogdBRL10)( LogdBRL20)( Transmission Loss (TL) in dB revfwdfwdWattsWattsWattsLogdBTL10)( 2110)( LogdBTL 220)(10110)(dBRLLogdBTL 211110)

4 (VSWRVSWRLogdBTL 5 of 6 033109 Antenna Equations Far Field Distance Dipole & Log-periodic antenna 2 FarField Horn antenna 22apetureFarField Far Field Equations Gain over isotropic 1010dBiGainNumericGain )(10numericdBiGainLogGain WattsMetersGainmVNumeric 302 WattsMetersLogGainmVdBi30102 )(20 AFMHzLogGaindBi Antenna Factor (AF) )(20 dBiGainMHzLogAF )(10)(20 numericGainLogMHzLogAF Find Antenna Spot size, Beam Width and Distance 2tanDistance23dBmetersmetersAngleSpot 2tan2 Distance3dBmetersmetersAngleSpot Distance2tan213metersdBSpotAngle Field Strength MetersGainWattsmVnumeric 30/ MetersWattsmVdBiGain 101030/ numericmVGainmetersWatts 302 1021030dBiGainmVmetersWatts Power needed if gain remains constant (in Far Field) using same antenna and changing field level or test distance. For Field Change 22 OldmVNewmVOldNewWattsWatts For Distance Change 22 OldNewOldNewMetersMetersWattsWatts Power for given Amplitude Modulation % CWpeakWattsWatts CWavgWattsWatts peakavgWattsWatts Power for given Pulse Modulation Duty Cycle % avgpeakWattsWatts 6 of 6 033109 Useful conversions 1 in = m 1 ft = m 1 yd = m 1 in2 = m2 1 ft2 = m2 1 yd2 = m2 1 in3 = m3 1 ft3 = m3 1 yd3 = m3 1 lb = kg 1 psi.)

5 = 6, Pa (Pascal) 1 hp = 550 ft lb/sec = Watts C = ( F-32) 1,000,000,000,000,000,000,000,000 = 1024 yotta Y 1,000,000,000,000,000,000,000 = 1021 zetta Z 1,000,000,000,000,000,000 1018 exa E 1,000,000,000,000,000 = 1015 peta P 1,000,000,000,000 = 1012 tera T 1,000,000,000 = 109 giga G 1,000,000 = 106 mega M 1,000 = 103 kilo k 100 = 102 hecto h = 10-2 centi c = 10-3 milli m = 10-6 micro = 10-9 nano n 0.

6 000000000001 = 10-12 pico p 0. 000000000000001 = 10-15 femto f 0. 000000000000000001 = 10-18 atto a 0. 000000000000000000001 = 10-21 zepto z 0. 000000000000000000000001 = 10-24 yocto y Resistor Color Codes 1st(A) 2nd(B) Multiplier (C) Tolerance (D) Color0011% Black11102% Brown221003% Red331034% Orange44104 Yellow55105 Green66106 Blue77107 Violet88108 Gray99109 No color20% Capacitor Color Codes Color Codes for Ceramic Caps Multiplier (C) Tolerance (D) Temp Coef ppm/ C (E) Color Above 10pf Below 10pf Black101-30 Brown1002-80 Red10003-150 Orange4-220 Green6-470 Blue7-750 White A B C DD A C BE A B C D E A B C DDisc Cap Ceramic Cap Mica Cap Classification A B D C White=EIA Code Black=Military Code Color=Old EIA