A photonic approach using two cascaded Mach-Zehnder modulators (MZMs) and a semiconductor optical amplifier (SOA) is proposed to generate microwave signals with a f requency 24times of that of the low-frequency seed signal,with the advantages of wide frequency coverage and e xcellent clutter suppression.In the proposed system,a low-frequency seed signal is applied to modulate the lig htwave from a laser source in the two cascaded MZMs which are biased at the maximum transmission point (MATP) via adjusting the dc bias to suppress the odd-order sidebands.Then the ±2nd sidebands and the optical carr ier at the output of the second MZM will be eliminated by properly adjusting the modulation indices of the two M ZMs as well as the phase shifts introdued by the tunable electrical phase shifter (TEPS) and the tunable optical phase shifter (TOPS),resulting in the generation of the ±4th sidebands.The ±4th sidebands are then injected int o the SOA to be two pump waves, so that two idle waves (i.e.,±12th sidebands) would be generated due to the four wave mixing (FWM) effect.The ±12th sidebands are selected by using an opti cal filter and sent to a high-speed photodetecor.As a result,a microwave signal with a frequency 24times of that of the low-frequency seed si gnal is achieved.Finally, experiment and simulation are performed to verify the feasibility of the approac h.When the frequency of the microwave driving signal is tuned from 11GHz to 12GHz with an interval of 0.5GHz,the spacing of the generated ±12th sidebands is achieved from 264GHz to 288GHz.