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The spurious-free dynamic range is the range (defined at the input of
the amplifier) from the noise floor or Minimum Detectable Signal (MDS)
level to the input level at which spurious products begin to emerge from
the noise floor at the output of the amplifier.
These spurious products may be either two-tone intermodulation
products or single-tone harmonic products. Intermodulation products
arise when two simultaneous signals are applied to the amplifier input
and mix due to nonlinearities, creating intermodulation products at the
amplifier output. Single-tone spurious products occur when only a
single fundamental frequency is present at the input of the amplifier.
Initially single tone spurious products will only consist of harmonic
integer multiples of the fundamental frequency, but, when these
harmonics achieve sufficient amplitude they begin generating
intermodulation products with the fundamental and eventually with
themselves. The spurious-free dynamic range can be calculated from
the amplifier's intercept point, gain, and MDS level, using the equation
DRf = 2/3[IP - G - MDS]
where DRf is the spurious free dynamic range (in dB)
IP is the third order intercept point (in dBm)
G is the gain of the amplifier (in dB)
MDS is the Minimum Detectable Signal at the input of the amplifier
MDS can be calculated from the Equation
MDS = kTB + BW + 3dB + NF
where kTB is the thermal noise level in a 1 MHz bandwidth (-114 dBm)
BW is the amplifier bandwidth (in dB relative to a 1 MHz bandwidth)
NF is the amplifier noise figure (in dB)
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