Local-oscillator noise cancellation in the subharmonically pumped down-converter

It is shown that the noise power at the IF output of a superheterodyne mixer, which is caused by local-oscillator noise, can be reduced significantly by using a subharmonically pumped down-converter. The response of conventional mixers and of the present down-converter to local-oscillator noise is analyzed. Measurements of the noise performance of a 60-GHz hyperbolic-sine-law mixer with IF output at 1.4 GHz are reported which clearly indicate a noise reduction of at least 19 dB relative to the noise expected from a conventional single-ended mixer employing the same local oscillator. It is concluded that the down-converter discussed provides an attractive solution to the problem of utilizing noisy sources, including IMPATT diodes, as local oscillators at millimeter-wave frequencies.