- A simple passive sampling mixer is shown in Figure 1.
- Sample RF signal at much lower frequency (LO frequency need not be near to RF)
- RF sampling mixer can be modeled as sampler followed by a ZOH circuit as shown in Figure 2.
- A continuous time signal() sampled at uniform sampling frequency() is given by
- Hold circuit
Fourier transform is
- The output after hold circuit is,
The spectral images of RF signal are suppressed by the sinc function
At , Conversion gain =
- The capacitive load() of S/H circuit eliminate the noise due to