The research is plan to harvest the collective power of China's largest radio telescopes, combine the raw voltages from individual telescopes to form a tied-array telescope that provides high signal-to-noise observations of millisecond pulsar (MSPs) with the objective to increase the sensitivity of detecting low-frequency gravitational waves (GWs). The Pulsar Timing Array (PTA) plan to use the telescopes of Chinese Very Long Baseline Interferometry (VLBI) Network (CVN). The five telescopes are: the Tian Ma 65 meters radio telescope, the Mi Yun 50 meters radio telescope, the Kun Ming 40 meters radio telescope, the Nan Shan 26 meters radio telescope and the She Shan 25 meters radio telescope. The goal of the research is to enhance the sensitivity of pulsar timing observations by combining the signals of the five largest Chinese radio telescopes. The combination of individual telescope signals can be done coherently or incoherently. In the incoherent addition the signal-to-noise ratio (S/N) increase with the square-root of the number of added telescopes. In coherent mode, the telescopes form a single tied-array beam and the S/N is (optimal) linear sum of the S/N of the individual telescopes. The research includes polarization calibration, bandpass correction, frequency dependent phase correction, interference mitigation and pulsar gating. The research plan to developed a correlator and beamformer that allows the pulsar observations from the telescopes from CVN to be added coherently. In further applications, the research will also plan to get experience for the data processing technologies for the Square Kilometre Array (SKA).
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