signals is less than 1.14 degree,when the output frequency is 750MHz.When the divider is cascaded with the frequency synthesizer,the measurement result shows that,every time it is divided by 2,the phase noise performance of the output signal improves by about 6dB Key words:frequency synthesizer,divider,4/4.5 prescaler,programmable divider,quadrature signalsignals is less than 1.14 degree, when the output frequency is 750MHz. When the divider is cascaded with the frequency synthesizer, the measurement result shows that, every time it is divided by 2, the phase noise performance of the output signal improves by about 6dB. Key words: frequency synthesizer, divider, 4/4.5 prescaler, programmable divider, quadrature signal V