A Baseband transmitter for a radio frequency (RF) communication device according to an embodiment of the present invention includes a single-carrier processor, a pulse shape filter, a multi-carrier processor and a signal combiner. The single-carrier processor generates a single-carrier signal at a first sample rate. The pulse shape filter includes multiple polyphase filters which filter the single-carrier signal according to a time shaping pulse that approximates a multi-carrier power spectrum and a sample switch that selects outputs of the polyphase filters at a second sample rate. The multi-carrier processor generates a multi-carrier signal at the second sample rate. The signal combiner combines the filtered single-carrier signal with the multi-carrier signal while maintaining phase, gain, frequency and timing alignment.