Now I design an image rejection mixer, conventional Gilbert cell mixer +poly phase filter the simulation results : conversion gain 6.4 dB, ip3 8.49dBm, ports to ports isolation is bigger than 40dB and the image rejection ratio is bigger than 50dB@all corner the power consumption 1.4mA*3.3V all satisfying except NF, the Noise Figure simulated more than 20dB including the ppf if I improve this parameter the current would increase, How to decrease the NF @ minimum power ,and I use the poly phase filter for image rejection ,because the results would vary with the RC mismatches,and the area really acount, any idea about image rejection? could someone please shed a sight and light me up?