Active N-path filters:Theory and design

Nowadays, wireless devices cover numerous wireless communication standards where almost for each one, a dierent frequency band has been allocated. There is a strong motivation towards SoC (System-on-Chip) solutions, where everything is integrated inside a chip to reduce the cost and form-factor of wireless devices. In radio-frequency receivers, due to the existence of large out-of-band blockers and a limited dynamic range, band-select ltering of the input signal is essential. Currently, most of the frontend circuitry of transceivers can be integrated on-chip. However, it is not possible to build integrated high-performance bandpass lters even after more than a decade research on this very topic. The inherent losses associated with on-chip inductors lead to lters having relatively high insertion losses, limited dynamic range and low outof- band rejection. For this reason, nowadays, most wireless systems utilize individual o-chip lters rather than fully integrated bandpass lters. This increases the size and cost. Moreover, most current wireless devices have several standards which leads to the exploitation of numerous o-chip bandpass lters which further exacerbate the size and cost issues.