1、EMC FormulaS Log Linear Voltage dBmV to Volts ( ) ( ) 20 / 120 10 - = V dB V m Volts to dBmV ( ) 120 log 20 + = V V dBm dBV to Volts ( ) 20 / 10 dBV V = Volts to dBV ( ) V dBV log 20 = dBV to dBmV 120 + = dBV V dBm dBmV to dBV 120 - = V dB dBV m Log Linear Power dBm to Watts ( ) ( ) 10 / 30 10 - = d
2、Bm W Watts to dBm 30 ) log( 10 + = W dBm dBW to Watts ( ) 10 / 10 dBW W = Watts to dBW ) log( 10 W dBw = dBW to dBm 30 + = dBW dBm dBm to dBW 30 - = dBm dBW Log Linear Current dBuA to uA ( ) 20 / 10 A dB A m m = uA to dBuA ) log( 20 A A dB m m = dBA to A ( ) 20 / 10 dBA A = A to dBA ) log( 20 A dBA
3、= dBuA to dBA 120 - = A dB dBA m dBA to dBuA 120 + = dBA A dBm Log Linear Impedance dB(ohms) to ohms ( ) 20 / ) ( 10 ohms dB Z = ohms to dB(ohms) ( ) Z ohms dB log 20 ) ( = Term Conversion dBm to dBuV dBm Z v dB + + = ) log( 10 90 m dBuV to dBm ) log( 10 90 Z V dB dBm - - = m dBuA to dBm 90 ) log( 1
4、0 - + = Z A dB dBm m dBm to dBuA 90 ) log( 10 + - = Z dBm A dB m dBuA to dBuV ) log( 20 Z A dB V dB + = m m dBuV to dBuA ) log( 20 Z V dB A dB - = m m Volts to Amps & Watts Z V A = Z V W 2 = Amps to Volts & Watts Z A V * = Z A W * 2 = Watts to Volts & Amps Z W V * = Z W A = RF related, Field Strengt
5、h & Power Density dBuV/m to V/m ) 20 / ) 120 ) / ( 10 / - = m V dB m V m V/m to dBuV/m ( ) 120 / log 20 / + = m V m V dBm dBuv/m to dBmW/m2 8 . 115 / 2 / - = m V dB m dBm m dBmW/m2 to dBuV/m 8 . 115 2 / / + = m dBm m V dB m dBuV/m to dBuA/m 5 . 51 / / - = m V dB m A dB m m dBuA/m to dBuV/m 5 . 51 /
6、/ + = m A dB m V dB m m dBuA/m to dBpT 2 / + = m A dB dBpT m dBpT to dBuA/m 2 / - = dBpT m A dBm W/m2 to V/m 377 * ) 2 / ( / m W m V = V/m to W/m2 377 2 ) / ( 2 / m V m W = wound coil Flux Density ) , ( 20 ) )( ( 4 m radius amps turns T p m = uT to A/m 25 . 1 / T m A m = A/m to uT ) / ( * 25 . 1 m A
7、 T = m EMC Calc Christian Rosu http:/ http:/Antenna (Far Field) Gain , dBi to numeric ) 10 / ( 10 dBi numeric Gain = Gain , numeric to dBi ) log( 10 numeric Gain dBi = Gain, dBi to Antenna Factor 79 . 29 ) log( 20 - - = dBi MHz AF Antenna Factor to gain in dBi 79 . 29 ) log( 20 - - = AF MHz dBi Fiel
8、d Strength given Watts, Numeric Gain, Distance in meters Meters Gain watts m V numeric * * 30 / = Field Strength given Watts, dBi gain, Distance in meters Meters watts m V dBi ) 10 / ( 10 * * 30 / = Transmit Power needed, given desired V/m, Antenna numeric gain, Distance in meters. numeric Gain mete
9、rs m V watts * 30 ) * / ( 2 = Transmit Power needed, given V/m, Antenna dBi gain, Distance in meters ) 10 / ( 2 10 * 30 ) * / ( dBi meters m V watts = Amplitude Modulation Peak power, given CW power and modulation % .(sine wave AM) 2 ) 01 . 0 * % ( 1 ( Mod W W CW peak + = Average power, given CW pow
10、er level and modulation % (sine wave AM) 2 ) ) 01 . 0 * % ( 2 ( * 2 Mod W W cw avg + = Average power, given peak power and modulation % 2 2 ) 01 . 0 * % ( 1 ( * 2 ) ) 01 . 0 * % ( 2 ( * Mod Mod W W peak avg + + = Current Probe dB(ohm) to Zt (transfer impedance) ) 20 / ) ( ( 10 ohm dB t Z = Zt to dB(
11、ohm) ) log( 20 ) ( t Z ohm dB = Conductance ( Gt) in dB(s) to transfer impedance, ( Zt) in dB(ohms) t G t Z - = Transfer Impedance in Zt ( dB(ohms), to Conductance in Gt (dB(s) t Z t G - = Power needed for BCI Probe (50 W) , given voltage level into 50 W load (V) and Probe Insertion Loss L I . ) 10
12、/ ) 50 / 2 log( 10 ( 10 V L I watts + = Watts needed for 150 Ohm EM Clamp ) 10 / ) 150 / 2 log( 10 ( 10 V L I watts + = Conducted current level using current measuring probe given probe factor in dB(ohm) and probe terminal voltage in dBuv ) ( ohm dB V dB A dB - = m m Conducted current level, given p
13、robe factor in Zt (ohms) and terminal voltage in dBuv ) log( 20 t Z V dB A dB - = m m dB calculations Compute db delta (volts) = 2 1 log 20 V V dB Compute dB delta (amps) = 2 1 log 20 A A dB Compute dB delta (watts) = 2 1 log 10 W W dB compute new voltage w/ db delta + D = 20 ) log( 20 ( 10 given V
14、dB new V compute new wattage w/ db delta + D = 10 ) log( 10 ( 10 given W dB new W EMC Calc Christian Rosu http:/ http:/ VSWR/reflection coefficient/return loss VSWR given Fwd/Rev Power fwd rev fwd rev P P P P VSWR - + = 1 1 VSWR given reflection coefficient r r - + = 1 1 VSWR Reflection coefficient,
15、 r, given Z1/Z2 ohms 2 1 2 1 Z Z Z Z + - = r Reflection coefficient, r, given fwd/rev power fwd rev P P = r Return Loss, given fwd/rev power = rev fwd P P dB RL log 10 ) ( Return Loss, given VSWR + - - = 1 1 log 20 ) ( VSWR VSWR dB RL Return Loss, given reflection coefficient ) log( 20 ) ( r - = dB
16、RL Mismatch loss, given fwd/rev power = - rev fwd fwd P P P dB ML log 10 ) ( Mismatch loss, given reflection coefficient ) 1 log( 10 ) ( 2 r - - = dB ML Misc Linear interpolation with log of freq L L U L U L X X X X F F Log F F Log Value + - = ) ( * ) / ( ) / ( where F L = lower frequency F U = Upper frequency X L = Value at lower frequency X U = Value at upper frequency F X = Frequency of desired value TEM Cell Power Needed Z Height V Watts 2 ) 5 . 0 * * ( = where V = field strength in V/m Z = TEM cell impedance in ohms EMC Calc Christian Rosu http:/ http:/
