Low noise, high linearity double-balanced active mixers using lossless feedback

A further development in the application of single-transformer lossless feedback to improve the performance of double-balanced active mixers is described, in which the significant sources of noise are removed without impairing the intermodulation performance. Noise figures of better than 6 dB are obtained while continuing to enjoy IIP performance of better than +25 dBm with a local oscillator power of just 0 dBm. A brief discussion of lossless feedback double-balanced active mixers is provided, and a generalized topology for low-noise lossless feedback mixers is described. Test data describing the intermodulation and noise performance of a specific example is presented.