A balanced transmitter up-converts a baseband signal directly from baseband-to-RF. The up-conversion process is sufficiently linear that no IF processing is required, even in communications applications that have stringent requirements on spectral growth. In operation, the balanced modulator sub-harmonically...http://www.google.co.uk/patents/US8077797?utm_source=gb-gplus-sharePatent US8077797 - Method, system, and apparatus for balanced frequency up-conversion of a baseband signal
