A digital phase and amplitude feedforward correction system

We have designed and fabricated a phase and amplitude correction system (PACS) using digital microelectronic circuitries and microstrip RF components with subnanosecond switching and response time. The control system uses a feedforward scheme to correct unwanted variations in phase and amplitude of a short (<100 ns) RF pulse which is generated repeatedly by an external RF source (e.g. relativistic klystron, FEL). Programmable or constant phase and amplitude (to within 0.5/spl deg/ and 0.1 dB, respectively) are achievable with the PACS. The system features a digitally programmable phase shifter and attenuator based on a direct RF digital-to-analog converter (RFDAC).<>