Split-band modulator for Kahn-technique transmitters

Kahn-technique transmitters exhibit high efficiency over a wide dynamic range of amplitudes and therefore also exhibit high average efficiencies for amplitude-modulated signals. Their bandwidth is, however, limited by that of their class-S modulator. The split-band modulator described here combines a class-S modulator and a class-B linear amplifier to provide greatly increased bandwidth (from 25 kHz to 5 MHz) at the cost of a small reduction (10 percent) in efficiency. A Negative-Component Signal Processor provides driving signals that allow both amplifiers to operate efficiently into resistive loads. Linear class-B amplifiers can be implemented with bandwidths of 100 MHz. The split-band modulator thus makes possible the use of the Kahn technique in wideband applications such as W-CDMA, base stations, and satellite repeaters.