EC-22.3 Noise Figure, Gain, Linearity and Dynamic Range

Work through these

• Thermal noise, noise power in a bandwidth, and the noise floor

  Any resistance at a temperature generates noise proportional to bandwidth, which sets the quietest signal any receiver can detect. Every sensitivity figure in a specification is that floor plus what the electronics adds.

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• Noise figure of one stage, and of a cascade

  The cascade formula divides each later stage's contribution by the gain before it, which is why the first amplifier decides almost everything. It also explains why a lossy component in front of the first stage is so expensive.

  NPTEL: RF Transceiver Design (IIT Roorkee) · Course

• Gain compression, and the one-decibel point

  Every amplifier stops being proportional at some input level, and the level at which its gain has fallen by one decibel is the standard way of quoting it. Above that point the output no longer represents the input.

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• Intermodulation and the third-order intercept point

  Two strong signals in a slightly non-linear stage create products that can land exactly on the wanted channel, where no filter can remove them. The intercept point is an extrapolated figure that predicts how bad this will be.

  NPTEL: RF Integrated Circuits (IIT Delhi) · Course

• Dynamic range: the gap between the faintest and the strongest usable signal

  The floor is set by noise and the ceiling by distortion, and improving one usually worsens the other. Stating the range explicitly forces that trade into the open rather than leaving it to be discovered on the bench.

• Building a chain budget in a spreadsheet, and reading what it says

  Laying every stage in a row with its gain, noise figure and intercept point produces the system figures directly and shows which stage is limiting. Almost every receiver design starts as one of these before a component is chosen.