LO drive level establishes the mixer switching condition, so too little or too much drive can change conversion gain or loss, P1dB, IP3, noise, offsets and leakage. Specify minimum, nominal and maximum LO power at the converter LO connector after the complete distribution path. Include source tolerance, splitter and switch loss, cable loss, temperature drift and mismatch.
LO leakage is LO energy appearing at the RF input, IF/output or other protected interface. At an antenna it can become an emission; at an ADC or amplifier it can consume headroom, mix again or create DC and baseband errors. Measure RF-to-LO, LO-to-IF and RF-to-IF isolation separately because they protect different paths. Add filtering, shielding, balanced topology or cancellation only after the required leakage limit and reference plane are known.
Verify conversion response, compression and two-tone intermodulation at the LO drive extremes, not only at nominal drive. Also check phase noise and reciprocal mixing with the real blocker plan. Reject the converter when acceptable linearity depends on an LO tolerance the distribution network cannot maintain, or when leakage remains above the antenna, ADC, amplifier or channel-allocation limit.