Design and Optimization of Mixers Using Load-Pull Analysis of Higher Order Intermodulation Products

This work proposes an innovative approach to improve the design of frequency-converting circuits. The novelty is the determination of the precise optimal impedance at each harmonic and inter-modulation frequency that will improve the performance of the mixer cell. The method takes into account the effect of the load impedances at inter-modulation frequencies on the conversion gain of the circuit. The proposed method can be applied to the optimization of any figure of merit. The optimal performance is found by varying load impedances, along with frequency, separately controlled using an ideal filter network at one or several mixer ports. The proposed load-pull analysis is applied to the optimization of a resistive mixer as a millimeter-wave monolithic integrated circuit, having a local oscillator frequency of 300 GHz and radio frequency bandwidth of 88 GHz. It is shown that by filtering the harmonics and presenting specific impedances, the conversion gain increases by more than 2.5 dB, while the radio frequency 3 dB-bandwidth has doubled. With the help of this analysis, the output matching network can be optimized.