Adaptive Feedforward Linear Wideband HF Power Bank.
NAVAL RESEARCH LAB WASHINGTON DC
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To fulfill modern naval command, control, and communication requirements, a new, wideband, high frequency HF communications system is being developed that is characterized by the complete removal of high power switching and tuning and that uses adaptive cancellation techniques in transmitting subsystem to suppress unwanted radiation of noise and distortion. The report focuses on the development of an unusually linear 500-W power amplifier and describes techniques that have been applied to further reduce noise and distortion product generation by means of iterated feedforward cancellation stages. Although three stages have been planned, only two have been implemented. To minimize power handling and distortion requirements of the auxiliary feedforward amplifiers, adaptively controlled weights are used to augment nonadaptive equalizers in the cancellation of fundamental energy for each stage. Performance measurements verifying the concept are presented, and various practical limitations are described. Intermodulation distortion to signal ratios of greater than -86 dBc have been achieved with the amplifier delivering two l00-W fundamental signals.
- Electrical and Electronic Equipment
- Radiofrequency Wave Propagation
- Radio Communications