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New for September 2010! Dynamic
range is the measurement of a receiver's ability to process a range
of input powers from the antenna. If the signal is too weak, it
can't be picked out from the noise, too large, and something starts
causing spurs, or maybe saturation occurs.
Dynamic range has the same meaning
in audio. In orchestras there are passages of near-silence, along
with passages of booming cannons, in the case of the 1812 Overture.
Recording and reproducing wide dynamic range is a challenge. Sometimes
a wide dynamic range is an annoyance. Did you ever try listening
to a "book on tape" in a car on the highway? If the speaker's
voice goes up and down in volume, you find yourself adjusting the
speaker volume in order to boost the quiet passages above the wind,
motor and tire noise, and reducing it when shouting starts in order
to spare your ears. In this manner, you have have become a compander,
mitigating the effects of a signal that has too much dynamic range
for the channel (your ears). The word "compansion" is
a portmanteau, a contraction
Spurious-free dynamic range
This is equal to 2/3 of the range
between the minimum detectable signal, and the third order intercept.
Defined this way, the dynamic range is the area between the minimum
detectable signal, and the point where the third-order product exceeds
minimum detection level.
Here's something peculiar...
if you worked really hard to improve the minimum detectable signal
of your receiver, and improved it by nine dB, you only improve the
SFDR by six dB!
Linear dynamic range
The linear dynamic range of a
receiver is a measurement of the minimum detectable signal, to the
maximum signal that will start to compress the receiver.
Extending dynamic range
Switchable attenuators can be
used in front of the receiver to extend the dynamic range. However,
this is at a cost of higher noise figure in the low gain state.