Some of the structures most frequently used for demodulation and modulation in the intermediate frequency (IF) stage of wireless transceivers are reviewed in this lecture. It is observed that high dynamic range, high selectivity and low harmonic distortion are essential features of IF systems. The design of a double-sided-band (DSB) to single-sided-band (SSB) converter using switched-capacitor techniques is presented, whose blocks are suitable for IF signal processing. The DSB / SSB converter has been implemented using discrete components and an image-rejection ratio above 40 dB has been experimentally obtained.