Built-in Filtering for Out-of-Channel Interferers in Continuous-Time Quadrature Bandpass Delta Sigma Modulators

This paper presents the design of implicit filtering for out-of-channel interferers in continuous-time (CT) quadrature bandpass (QBP) ΔΣ modulator using a differentiated signal-transfer-function (STF). Comparative study between possible ΔΣ modulator loop filter structures is addressed to better cope with the best implementation. The Fifth-order CT QBP ΔΣ modulator planned for the WiFi adjacent channel blockers requirements, illustrates clearly the totally elimination of interferers and the correctly signal process. This led to remove the baseband filter and PGA at the price of a very challenging ADC with merged-in cited functionalities. So, less analog components, low power consumption and high performance for the low-IF receiver.