In this paper, we show that the signal transfer function of continuous-time /spl Sigma//spl Delta/ modulators can be used to remove the baseband analog filters in radio receivers. General expressions for the signal transfer function of continuous-time /spl Sigma//spl Delta/ modulators are derived. Comparisons between the frequency response of feedforward and feedback architectures of discrete-time and continuous-time /spl Sigma//spl Delta/ modulators are established. Filtering of GSM adjacent channel blockers using a 5/sup th/ order continuous-time /spl Sigma//spl Delta/ is given as an example.