RF Calculations & RF Unit Conversions
Note: The decimal point "." is used as decimal separator for both input and output:
Calculate wavelength from frequency:
Formula:
λ = c/f
λ: Wavelength in meters
c: Speed of light (299792458 m/s)
f: Frequency in Hz
Input frequency in Hz:
Calculate frequency from wavelength:
Formula:
λ = c/f
λ: Wavelength in meters
c: Speed of light (299792458 m/s)
f: Frequency in Hz
Input wavelength in m:
Conversion between different units of Power Flux Density:
Power Flux Density in W/m2:
Power Flux Density in mW/m2:
Power Flux Density in uW/m2:
Power Flux Density in W/cm2:
Power Flux Density in mW/cm2:
Power Flux Density in uW/cm2:
Calculate 3-axis Field Intensity from 1-axis Mesurement:
Formula:
Field Intensity = √ (x2 + y2 + z2)
E: 3-axis Field intensity, measured in V/m
X, Y, Z: Single axis field intensity, measured in V/m.
Note:
Some instruments only measure single axis field intensity. This calculation is used to calculate the 3-axis field intensity from 3 single axis measurements.
Single axis Field Intensity (x-axis) in V/m:
Single axis Field Intensity (y-axis) in V/m:
Single axis Field Intensity (z-axis) in V/m:
Calculate Field Intensity from Power Flux Density:
Formula:
Pd = E2/Z0 = Z0*H2
Pd: Power Flux Density, measured in W/m2
E: Field Intensity for the electric field, measured in V/m.
H: Magnetic field, measured in A/m.
Z0: Impedance of free air = 120π = 377Ω
Note:
I far-field conditions Field intensity and Power Flux Density is related by free air impedance. This calculation is therefore only valid for far-field conditions.
Power Flux Density in W/m2:
Calculate Power Flux Density from Electric Field Intensity:
Formula:
Pd = E2/Z0 = Z0*H2
Pd: Power Flux Density, measured in W/m2
E: Field Intensity for the electric field, measured in V/m.
H: Magnetic field, measured in A/m.
Z0: Impedance of free air = 120π = 377Ω
Note:
I far-field conditions Field intensity and Power Flux Density is related by free air impedance. This calculation is therefore only valid for far-field conditions.
Electric Field Intensity in v/m:
Calculate Power Flux Density from an Isotropic Antenna:
Formula:
Pd = Pt / (4 * π * d2)
Pd: Power Flux Density, measured in W/m2
Pt: Transmitter Output Power, measured in W
d: Distance, measured in meters
Transmitter Output Power in Watts:
Distance in meters from transmitter:
Calculate Power Flux Density from an Directional Antenna:
Formula:
Pd = (Pt * Gt) / (4 * π * R2)
Pd: Power Flux Density, measured in W/m2
Pt: Transmitter Output Power, measured in W
Gt: Transmitter antenna gain (linear)
d: Distance, measured in meters
Transmitter Output Power in Watts:
Distance in meters from transmitter:
Gain (linear, non-dimensional) for transmitter antenna:
Conversion from Gain in dB to linear gain:
Formula:
Glinear = 10(GdB / 10)
Glinear: Gain measured in linear terms (dimensionless)
GdB : Gain measured in dB
Note:
Gain can be measured either as a purely matematical construct - in which case it is referred to as dB.
It can also be measured in decibels referenced to an isotropic antenna - in which case it is referred to as dBi
Since the gain of an isotropic antenna is 1, these units are interchangeable. 1 dB gain is equal to 1 dBi gain, but the term dBi denotes the reference to the isotropic antenna.
An alternative definition compares the antenna to the power received by a lossless half-wave dipole antenna, in which case the units are written as dBd.
Since a lossless dipole antenna has a gain of 2.15 dBi, the relation between these units is: gain in dBd = gain in dBi - 2.15 dB
Gain in dB:
Conversion from power in dBm to power in Watt:
Formula:
P(W)Power = 1W * 10(P(dBm)/10) / 1000
P(W) : Electrical Power, measured in W
P(dBm) : Electrical Power, measured in dBm
Note:
dBm denotes a measurement in decibels referenced to a milliWatt
Power in dBm:
Conversion from power in dBW to power in Watt:
Formula:
P(W)Power = 1W * 10(P(dBW)/10)
P(W) : Electrical Power, measured in W
P(dBW) : Electrical Power, measured in dBW
Note:
dBW denotes a measurement in decibels referenced to a Watt
Power in dBW:
Conversion from power in Watt to power in dBm:
Formula:
P(dBm) = 10 * log10(1000 * P(W))
P(W) : Electrical Power, measured in W
P(dBm) : Electrical Power, measured in dBm
Note:
dBm denotes a measurement in decibels referenced to a milliWatt
Input power in Watt:
Conversion from power in Watt to power in dBW:
Formula:
P(dBW) = 10 * log10(1 * P(W))
P(W) : Electrical Power, measured in W
P(dBm) : Electrical Power, measured in dBW
Note:
dBW denotes a measurement in decibels referenced to a Watt
Input power in Watt:
Calculate EIRP from Transmitter Power and Gain:
Formula:
EIRP = Pt * Gt
Pt: Transmitter Power, measured i W
Gt: Transmitter Gain, measured as a linear ratio
Transmitter Power in Watt:
Linear Gain:
Calculate EIRP from Electric Field and Distance:
Formula:
EIRP = (E * d)2 / 30
E: Electrical Field, measured in V/m
d: Distance, measured in meters
Electric Field in V/m:
Distance in m:
Calculate ERP from EIRP:
Formula:
ERP = EIRP / 1.64
EIRP:
Friis Transmission Formula (calculation of received power) solved for wavelength:
Formula:
Pr = (Pt * Gt * Gr * λ2 ) / (4*pi*d)2
Pr : Received Power, measured in W
Pt : Transmittet Power, measured in W
Gt : Transmitter Antenna Gain, linear
Gr : Receiver Antenna Gain, linear
λ : Wavelength, measured in meters
d : Distance, measured in meters
Transmitter Power (W):
Transmitter gain (linear):
Receiver gain (linear):
Wavelength (m):
Distance (m):
Calculate Safety Distance from a transmitter:
Formula:
Pd = (Pt * Gt) / (4 * π * d2)
Pd: Power Flux Density, measured in W/m2
Pt: Transmitter Power, measured in W
Gt: Transmitter Antenna Gain, linear
d: Distance, measured in meters
Note:
Safety distances are calculated using:
SBM2008 "No Concern"-Limit: 0.0000001 W/m2
BioInitiative 2012 "Precautionary Level": 0.000003 W/m2
Transmitter Output Power in Watts:
Gain (linear, non-dimensional) for transmitter antenna: