A low-complexity analog technique to suppress the local oscillator (LO) harmonics in software-defined radios is presented. Accurate mathematical analyses show that an effective attenuation of the LO harmonics is achieved by modulating the transconductance of the low-noise transconductance amplifier (LNTA) with a raised-cosine signal. This modulation is performed through the bias network of a cascode device with a negligible increase in the LNTA noise figure. The proposed technique results in a notch at the third harmonic and at least 36 dB of attenuation at the fifth and the seventh harmonics. Experimental results in 130-nm CMOS and post layout simulation results in 65-nm CMOS verify the proper functionality of the proposed technique and the accuracy of the proposed analyses.
DT mixing techniques of LO harmonic is used to improve their harmonic rejection.
It presents the SDR receivers for low complexity analog technique for attenuation of LO harmonics.