The fast orbit feedback (FOFB) system of the high energy photon source (HEPS) has been developed for the beam orbit control in its storage ring. It mainly consists of beam position monitors (BPMs), the algorithms of fast orbit controller (FOC) and fast correction units. To support HEPS commissioning, we have developed a high-performance signal generator to complete the simulation of beam signals.

The developed signal source includes four output ports with independently adjustable signal amplitudes and synchronous triggers. Its goal is to simulate the timing signals, and enable the simulation output of BPM signals under real beam conditions in the laboratory without beam, with the advantages of simple structure, low cost and high repeatability.

The core of the signal source is an FPGA board. Firstly, a 250 MHz clock signal with a 25% duty cycle was generated by the PLL and directly routed through the MRCC pin. After completing the impedance matching, the RF signal was processed via differential circuit to obtain the required simulated beam signals. Then, the required signals were amplified using the RF amplifier. After the 1∶4 power division, beam signals with four adjustable amplitudes output channels were finally acquired. The trigger signal was supplied directly from the FPGA I/O pins configured for LVCMOS33 operation at 3.3 V, to meet the required LVTTL of BPM electronics.

Based on the beam current characteristics of the HEPS storage ring, we tested the beam signal simulation performance of HEPS storage ring with a frequency of 220 kHz and different patterns during the experiment. In addition, the simulation performance of the single trigger signal and BEPCII collision zone with a frequency of 1.21 MHz has also been tested. The test results showed that the developed signal source could simulate the beam signal well and meet the design requirements. Then, we tested the pattern dependence of HEPS BPM electronics with this signal source. The results showed that there was no pattern dependence effect in the HEPS BPM electronics used in this experiment.

This signal generator could be used to assist in the logical design and correctness of DBPM, to debug the data transmission and control logic between the DBPM and FOFB, and to test the latency of the FOFB system. Based on this system, the debugging difficulty of BPM and FOFB systems could be reduced and accelerate the deployment of the FOFB system.