The Image-Reject Continuous-Time Quadrature Bandpass DS Modulator

This paper presents the design of an image-reject continuous-time (CT) quadrature bandpass (QBP) DS modulator using a tailored signal-transfer-function (STF) design. The quadrature delta-sigma noise shaping with polyphase filter implementations and strategic IF placement effectively improve image rejection internally. The Fifth-order CT QBP DS modulator planned for WiMAX and Bluetooth standards, illustrates clearly the totally elimination of image generation 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.