U-band microwave direct modulation system

A U-band microwave direct modulation system comprises a C-band local oscillation circuit, a C-band amplification circuit, a U-band 8-frequency multiplication circuit, a U-band QPSK microwave direct modulation circuit and a level conversion circuit. The C-band local oscillator circuit takes a high-stability reference source as an input, performs sampling phase locking on the high-stability reference source, and generates C-band carrier waves with extremely low phase noise; the C-band amplifying circuit is used for carrying out power amplification and isolation on the C-band carrier with extremely low phase noise; the U-frequency band 8-frequency multiplication circuit is used for carrying out multiple harmonic frequency multiplication and isolation on the amplified and isolated C-frequencyband carrier wave with extremely low phase noise so as to generate a U-frequency band carrier wave; the level conversion circuit performs bipolar conversion on the external data to obtain bipolar level data; and the QPSK microwave direct modulation circuit of the U frequency band modulates the phase of the carrier of the U frequency band under the data driving of the bipolar level to realize QPSKmodulation so as to obtain a QPSK modulation signal, and the QPSK modulation signal is isolated and then output.