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[Technical article / FAQ, rfforum Editorial Team]
Datasheet LO-to-RF and LO-to-IF isolation, and even-order rejection, are often quoted at one drive level. On the bench, a mixer that looks clean at the datasheet LO power can throw even-order spurs as soon as drive walks a few dB — and many travelers never re-check.
1. What drive actually owns
- Diode / FET balance and LO amplitude set even-order cancellation; underdrive and overdrive both move the null
- A "good" LO-to-IF leakage number at one drive can worsen when you raise LO to buy conversion loss
- Temperature and supply on the LO buffer shift effective drive at the mixer, so a cold desk number is not the product operating point
2. Freeze list for an even-order / isolation claim
- LO power at the mixer port (not only at the generator), conversion loss, and even-order / LO leakage on the same sheet
- Sweep ± a few dB around the datasheet drive; note where rejection collapses
- Warm-up / thermal soak if the LO buffer or mixer is in a closed housing
- Whether RF was terminated when LO leakage at IF was measured (classic feedthrough trap)
3. Habit
Never publish mixer even-order or LO isolation from a single drive point. Archive the drive sweep next to the headline number.
Discussion: on your last even-order hunt, did the fix land in LO drive, a balun / layout balance change, or a different mixer — and do you require a drive sweep on every isolation traveler?
— rfforum 编辑部 / Editorial Team
Datasheet LO-to-RF and LO-to-IF isolation, and even-order rejection, are often quoted at one drive level. On the bench, a mixer that looks clean at the datasheet LO power can throw even-order spurs as soon as drive walks a few dB — and many travelers never re-check.
1. What drive actually owns
- Diode / FET balance and LO amplitude set even-order cancellation; underdrive and overdrive both move the null
- A "good" LO-to-IF leakage number at one drive can worsen when you raise LO to buy conversion loss
- Temperature and supply on the LO buffer shift effective drive at the mixer, so a cold desk number is not the product operating point
2. Freeze list for an even-order / isolation claim
- LO power at the mixer port (not only at the generator), conversion loss, and even-order / LO leakage on the same sheet
- Sweep ± a few dB around the datasheet drive; note where rejection collapses
- Warm-up / thermal soak if the LO buffer or mixer is in a closed housing
- Whether RF was terminated when LO leakage at IF was measured (classic feedthrough trap)
3. Habit
Never publish mixer even-order or LO isolation from a single drive point. Archive the drive sweep next to the headline number.
Discussion: on your last even-order hunt, did the fix land in LO drive, a balun / layout balance change, or a different mixer — and do you require a drive sweep on every isolation traveler?
— rfforum 编辑部 / Editorial Team
