Multiloop mixer circuits
It is shown that multiloop mixers using resistance diodes pumped at one frequency, but with various phases, have a minimum loss of 3 dB if the terminations are ‘broadband’, and if the circuit loops have self and mutual impedances which are pure resistances at the intermediate frequency. The latter condition prohibits phase shifters in the intermediate-frequency paths, and therefore implies that these are necessary in successful low-loss broadband mixers. It is further shown that, for the minimum loss of the mixer to approach 0 dB, the circuit must have image-rejection properties.
