Fundamental Limitations on the Output Power of Balanced Mixers and Even Harmonic Mixers in Modulator Operation

A theoretical comparison of fundamental limitations on the output power of balanced diode mixers and even harmonic mixers is presented in this paper. The modulator operation is employed for the formulation. Additionally, the maximum output power, the output power at the 1-dB gain compression point, and the conversion loss of both mixers are formulated. It is theoretically confirmed that even harmonic mixers exhibit output power saturation when there is a high local oscillator power, although balanced diode mixers exhibit no saturation. This saturation is caused by restrictions in the built-in voltage of diodes, and even harmonic mixers therefore have lower output power capability when compared to balanced diode mixers. Derived formulas are confirmed by performing experimental investigations at 100 MHz.