Analog Devices, Inc.
DC DETECTOR FOR A TRANSMIT DATAPATH

Abstract:

A transmitter with a DC detection circuit that can control when a modulator of the transmitter is active. When data is being transmitted, a tone introduced by a mixer in the transmit path is hidden by the data signal and has minimal effect on the transmit path. However, when there is no data, the tone can cause undesirable noise. A modulator may move the tone or noise outside of the transmitter's bandwidth. As the data can hide the tone, the DSM may only be needed when there is a DC signal. By activating the DSM only when a DC signal is detected, the extra power introduced by the modulator can be reduced while eliminating in-band noise.