Observations of microwave type-U bursts

Two microwave type-U bursts observed with the 2.6-3.8 GHz spectrometer of B eijing Astronomical Observatory (BAO) are described and analysed in this pa per. The microwave type-U bursts have very short durations (about 200 ms), narrow bandwidth. high-frequency drift rates of the ascending and descendin g branches, and a high degree of circular polarization (80%). The sense of polarization remains the same from the ascending to the descending branch.