AC Coupling in Direct-Conversion Receiver for TD-SCDMA Mobile

摘要

The AC coupling circuit is widely used in direct-conversion receivers to suppress the in-band DC offset and 1/f noise. This paper analyzes the requirements of the AC coupling circuit in a TD-SCDMA mobile phone operating in an environment with strong out-of-band interference. In this paper, a passive first-order high-pass filter is assumed to act as the AC coupling circuit. The recommended cutoff frequency of this high-pass filter is within the range of l0kHz-30kHz in order to achieve a required 2nd-order intermodulation intercept point (IIP2) of 36.7dBm -36.3dBm with a signal-to-noise ratio loss of less than 0.3dB.