Adapted Attenuator and Noise Factor

This chapter shows explicitly that the noise figure on 50 ohm, denoted as NF(50 ohm) expressed in dB, of a resistive attenuator adapted on 50 ohm, is equal to its attenuation expressed in dB. It demonstrates the calculation of the attenuator's Y and S parameters and the condition for the attenuator to be adapted to 50 ohm; equivalent noise generators at the attenuator's input; and the noise factor on 50 ohm of this attenuator. To represent noise in a noisy two‐port, two partially correlated equivalent noise sources can be used: one in voltage and the other in current, placed at the input of the two‐port. The chapter shows how to calculate noise factor on 50 ohm of the adapted attenuator, and demonstrates another way to demonstrate the result by using noise power waves and Bosma's theorem.