Rapporto SNR in uscita

Se si valuta il rapporto segnale rumore in uscita alla rete, otteniamo

SNR_u$$\left(\vphantom{ f}\right.$$f$$\left.\vphantom{ f}\right)$$ = $${\frac{\mathcal{W}_{dg}\left( f\right) G_{d}\left( f\right) }{\frac{1}{2}kT_{e_{i}}\left( f\right) G_{d}\left( f\right) }}$$ = $${\frac{\mathcal{W}_{dg}\left( f\right) }{\frac{1}{2}k\cdot \left[ T_{g}\left( f\right) +\left[ A_{d}\left( f\right) -1\right] T_{Q}\right] }}$$

Ricordando che il generatore in ingresso presenta un SNR_i$\left(\vphantom{ f}\right.$f$\left.\vphantom{ f}\right)$ = ${\frac{\mathcal{W}_{dg}\left( f\right) }{\frac{1}{2}kT_{g}\left( f\right) }}$, possiamo valutare il peggioramento prodotto dalla presenza della rete:

$${\frac{SNR_{i}\left( f\right) }{SNR_{u}\left( f\right) }}$$ = $${\frac{\mathcal{W}_{dg}\left( f\right) }{\frac{1}{2}kT_{g}\left( f\right) }}$$ ^. $${\frac{\frac{1}{2}k\cdot \left[ T_{g}\left( f\right) +\left[ A_{d}\left( f\right) -1\right] T_{Q}\right] }{\mathcal{W}_{dg}\left( f\right) }}$$ = 1 + $${\frac{T_{Q}}{T_{g}\left( f\right) }}$$ ^. $$\left[\vphantom{ A_{d}\left( f\right) -1}\right.$$A_d$$\left(\vphantom{ f}\right.$$f$$\left.\vphantom{ f}\right)$$ - 1$$\left.\vphantom{ A_{d}\left( f\right) -1}\right]$$