How is an upload signal processed by an inverting linear transponder?

An inverting linear transponder works by heterodyning (mixing) the incoming uplink signal with a fixed Local Oscillator (LO) on board the satellite. To achieve inversion, the circuitry selects the difference product of this mixing process (LO frequency minus uplink frequency). Because the uplink frequency is subtracted from the fixed LO frequency, an increase in the uplink frequency results in a decrease in the downlink frequency. This subtractive process is exactly what causes the sidebands to invert (USB becomes LSB) and the passband positioning to reverse. Distractors mentioning remodulating on a reverse sideband or filtering Q components describe complex digital or SDR processes rather than the fundamental analog mixing used to create a classic inverting transponder.