Yes, the latest generation of engineers are exploiting these new devices in exciting ways. I guess the reason I described it as a bit sad was because (in lots of areas) the modern chipsets/DSP are creating a layer of insulation between modern RF design techniques and basic physics. Maybe a few forum readers will be a bit alienated by my references to 'negative resistance'. Most people are quite comfy with the physics behind regular resistors and 'resistance' but the concept of negative resistance may be a bit of a mind bender for some. But in reality it isn't anything exotic. We have all measured FWD and REV with a VSWR meter when measuring antennas and antennas are usually passive devices. So the worst case 'reflection' is usually one where the antenna isn't there or is broken and the VSWR appears to be infinite. In this case the reflection coefficient is 1 (or extremely close to 1) because the reflected wave is the same size as the forward wave. Negative resistance can occur in active devices like amplifiers and when the VSWR of an amplifier port is measured with a VNA the reflected reading can arrive back slightly bigger than the initial forward reading. This means the load under test is an active source that can boost the strength of the reflected signal and it is said to be generating negative resistance. The magnitude of the reflection coefficient might be 1.015 for example. This is only a tiny amount bigger than 1.000 but this is enough to cause instability in an amplifier if it is then presented with a passive load impedance that can set up a series LCR network where the negative resistance produced by the amplifier is able to dominate the passive resistance in the passive load network at a frequency where there is resonance. In this case the resonance happens just outside the regular smith chart and this is the region where negative resistance can be plotted on a VNA. A modern VNA will be all set up to cope with and display negative resistance although the smith chart display may have to be shrunk to allow extra screen space to display the region outside the regular smith chart circle where the negative resistance is occurring. All areas inside the regular smith chart circle are impedances that have positive resistance.