Improved Vector Modulator Card for MTCA-based LLRF Control System for Linear Accelerators

Modern linear accelerators require high-precision RF field regulation of accelerating cavities. A critical component to achieve high-precision in the feedback loop a Low Level Radio Frequency (LLRF) controller is the vector modulator driving the high power RF chain. At FLASH, the Free Electron Laser in Hamburg and European XFEL the LLRF controls are based on MTCA.4 platform. This paper describes the concept, design and performance of an improved vector modulator module (DRTM-VM2). It is constructed as Rear Transition Module (RTM). The module consists of digital, analog, diagnostic and management subsystems. FPGA from Xilinx Spartan 6 family receives data from control module (AMC) using Multi-Gigabit Transceivers (MGTs). The FPGA controls the analog part which includes fast, high-precision DACs, I/Q modulator chips, programmable attenuators, power amplifier and fast RF gates for external interlock system. Pin assignment on the Zone3 connector is compliant with digital class D1.2 recommendations proposed by DESY. The design has been optimized for mass production and for easy extends to wider frequency range. Electronic switches offer software configuration of power and clock sources